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The implementation of the succession process as a strategy of mapping, development and retention of talent is gaining space in organizations. This article aimed to verify whether organizations have a structured process for retaining professionals identified as potential successors and whether there is differentiation according to the level of maturity of the succession process. A sample of companies seeking to differentiate themselves in terms of people management, consisting of 396 companies, was analyzed. For analysis, the Phi coefficient was used, and the survey results showed that a small number of organizations have a process of retaining professionals identified as potential successors, and that organizations that are more mature with respect to their succession process are more likely to work on retaining their talents in a structured manner, and the aspects that lead to most voluntary dismissals of professionals in the organizations surveyed are linked to compensation, career and development actions.

Made available in DSpace on 2021-06-25T10:27:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Wireless communication employing radio-frequency identification (RFID) tags is progressively more widespread in a variety of industrial and commercial sectors. Aspects as demanding specific needs regarding reading distance, production cost, and processability are requested for commercial applications. Nowadays, printing of optical barcodes is the most economically technology for short distance (up to ~30 cm) reading applications. However, the large-scale and low-cost printing of RFID tags would be a competitive alternative to barcode technology because it allows quicker identification with much less reading errors. Here we demonstrate a semi-transparent, screen printed RFID antennas using a non-metallic and environmentally friendly conductive paste. The variation of the film thickness (from 2.5 up to 15 µm) permitted the fabrication of antennas with reading range (0.84–3.29 m), sheet resistance (6.2–36 Ω/sq), and optical transmittance (0–32.3%), which are compatible to commercial or industrial applications aiming short to moderate reading distances. Indústria de Tintas Condutivas TICON Flextronics Instituto de Tecnologia (FIT) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp)

The increasing demand for food production has necessitated the development of sensitive and reliable methods of analysis, which allow for the optimization of storage and distribution while ensuring food safety. Methods to quantify and monitor volatile and biogenic amines are key to minimizing the waste of high-protein foods and to enable the safe consumption of fresh products. Novel materials and device designs have allowed the development of portable and reliable sensors that make use of different transduction methods for amine detection and food quality monitoring. Herein, we review the past decade?s advances in volatile amine sensors for food quality monitoring. First, the role of volatile and biogenic amines as a food-quality index is presented. Moreover, a comprehensive overview of the distinct amine gas sensors is provided according to the transduction method, operation strategies, and distinct materials (e.g., metal oxide semiconductors, conjugated polymers, carbon nanotubes, graphene and its derivatives, transition metal dichalcogenides, metal organic frameworks, MXenes, quantum dots, and dyes, among others) employed in each case. These include chemoresistive, fluorometric, colorimetric, and microgravimetric sensors. Emphasis is also given to sensor arrays that record the food quality fingerprints and wireless devices that operate as radiofrequency identification (RFID) tags. Finally, challenges and future opportunities on the development of new amine sensors are presented aiming to encourage further research and technological development of reliable, integrated, and remotely accessible devices for food-quality monitoring. Made available in DSpace on 2022-09-28T20:05:36Z (GMT). No. of bitstreams: 1 P-Recent-Progress-in-Amine-Gas-Sensors-for-Food-Quality-Monitoring.pdf: 4506930 bytes, checksum: afd8070c0df98dba888f9ab63a3b7a3e (MD5) Previous issue date: 2022

Made available in DSpace on 2020-12-12T02:46:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-07-15 A comparison of Zinc Oxide (ZnO) phototransistors prepared by spray and sputter coating process is presented. The work shows that spray coated layers provide significant advantages in sensor response over ZnO phototransistors made by physical vapour deposition and we show that spray deposited ZnO phototransistors can exhibit state-of-the-art performances for UV photodetectors. Topographic images of the samples surface shows that there is increase in surface roughness in spray coated samples indicating increasing grain sizes, which is considered the source of the greater sensor responsivity. X-ray photoelectron spectroscopy (XPS) is also used to understand the root cause of the greater UV responsivity. It was observed that sprayed ZnO TFTs are more sensitive to UV radiation due to higher adsorption of oxygen level. Responsivity and external quantum efficiency (EQE) of the sprayed and sputtered ZnO TFTs are also evaluated. School of Electronics Bangor University School of Technology and Sciences São Paulo State University (Unesp) Institute of Geosciences and Exact Sciences São Paulo State University (Unesp) Rio Claro Faculty of Science and Engineering University of Chester School of Technology and Sciences São Paulo State University (Unesp) Institute of Geosciences and Exact Sciences São Paulo State University (Unesp) Rio Claro

Made available in DSpace on 2022-04-28T19:49:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Monitoring glucose levels is critical for diabetes management and might be a key step in the development of individualized treatment strategies. In this scenario, tracking salivary glucose has been recognized as a promising strategy due to its merits of ease sampling and non-invasive nature. In this paper, we report on the development of an electrical impedance-based biosensor array to distinguish glucose at different concentrations in saliva. The enzymatic biosensors were made of gold interdigitated electrodes coated with pristine electrospun zinc oxide nanofibers (NFZ) and NFZ combined with graphene-based nanomaterials (i.e., reduced graphene oxide - rGO and graphene quantum dots - GQDs), on which a layer of glucose oxidase (GOx) enzyme was adsorbed. Electrical impedance measurements indicate that the NFZ-GQDs@GOx and NFZ-rGO@GOx platforms presented good linear relationship with glucose concentration in the range of 0.1 to 6 mM. The highest sensitivity was reached for NFZ-rGO@GOx with a detection limit (LOD) of 14 μM, while the LOD was 32 μM for NFZ-GQDs@GOx. Both biosensors were also capable of detecting glucose in artificial saliva using aliquots of 10 μL, with recovery between 87.3 and 106.8%. Furthermore, the three sensing units (NFZ@GOx, NFZ-rGO@GOx and NFZ-GQDs@GOx) were employed to build a bioelectronic tongue. Using Principal Component Analysis (PCA) technique to project the electrical impedance data of all sensing units allowed the discrimination of the different glucose concentrations and interferents. This study reveals the applicability of the developed bioelectronic tongue as non-invasive glucose sensors, which approach could also be pottentially adapted to detect other disease biomarkers present in saliva. Institute of Chemistry Federal University of Bahia (UFBA), BA Nanotechnology National Laboratory for Agriculture (LNNA) Embrapa Instrumentação, SP PPGQ Department of Chemistry Center for Exact Sciences and Technology Federal University of São Carlos (UFSCar), SP Physics Department Institute of Geosciences and Exact Sciences São Paulo State University (UNESP), SP Physics Department Institute of Geosciences and Exact Sciences São Paulo State University (UNESP), SP FAPESP: 2016/23793-4 FAPESP: 2017/10582-8 FAPESP: 2017/12174-4 FAPESP: 2018/22214-6

Made available in DSpace on 2019-10-06T17:10:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Conductive composites based on cross-linked poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blends have been widely applied to produce electronic devices, such as organic electrochemical transistor, biosensors and electrochromic devices, to name a few. Notwithstanding, fundamental details regarding the influence of the cross-link agent on the charge transport mechanism of PEDOT:PSS based composites is still not completely understood. Herein, we present a study regarding the influence of the cross-link (3-glycidyloxypropyl) trimethoxysilane (GPTMS) on the charge transport mechanism of PEDOT:PSS/GPTMS composites. We have verified that the charge transport is dominated by hopping into percolated PEDOT:PSS-rich clusters for composites with a PEDOT:PSS content above 40%-wt. Interestingly, by analyzing the conductivity data by the variable range hopping model we observed that the hopping temperature, electronic localization length and charge carriers mobility remains practically independent on the PEDOT:PSS concentration. As for non-percolated composites, (i.e. below 40%-wt PEDOT:PSS), however, the charge transport is dominated by charge carrier hopping between unconnected PEDOT:PSS clusters, in which the electrical conductivity and the hopping temperature are strongly influenced by the cross-link agent content, and characterized by shorter carrier localization lengths. Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Sao Carlos Institute of Physics University of São Paulo, PO Box 369 Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP

Made available in DSpace on 2022-04-28T19:41:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-25 Quality control in the production and processing of raw meat is currently one of the biggest concerns for food industry and would benefit from portable and wireless sensors capable of detecting the onset of spoilage. Raw meat is a natural source of biogenic and volatile amines as byproducts of decarboxylation reactions, and the levels of these compounds can be utilized as quality control parameters. We report herein a hybrid chemiresistor sensor based on inorganic nanofibers of SiO2:ZnO (an n-type material) and single-walled carbon nanotubes functionalized with 3,5-dinitrophenyls (a p-type material) with dosimetric sensitivity ∼40 times higher for amines than for other volatile organic compounds, which also provides excellent selectivity. The hybrid nanomaterial-based chemiresistor sensory material was used to convert radio-frequency identification tags into chemically actuated resonant devices, which constitute wireless sensors that can be potentially employed in packaging to report on the quality of meat. Specifically, the as-developed wireless tags report on cumulative amine exposure inside the meat package, showing a decrease in radio-frequency signals to the point wherein the sensor ceased to be smartphone-readable. These hybrid material-modified wireless tags offer a path to scalable, affordable, portable, and wireless chemical sensor technology for food quality monitoring without the need to open the packaging. Department of Chemistry Institute for Soldier Nanotechnologies Massachusetts Institute of Technology Cambridge, 77 Massachusetts Avenue Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, 77 Massachusetts Avenue Nanotechnology National Laboratory for Agriculture (LNNA) Embrapa Instrumentação, São Paulo Institute of Geosciences and Exact Sciences São Paulo State University (UNESP), São Paulo Institute of Geosciences and Exact Sciences São Paulo State University (UNESP), São Paulo

Made available in DSpace on 2021-06-25T10:33:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Instituto Nacional de Ciência e Tecnologia em Eletrônica Orgânica Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The UV photocurrent response of thin films of wide bandgap semiconductors such as zinc oxide (ZnO) can be applied to a great number of electronic devices aiming applications in environmental sensing or UV-detection. Electronic devices like thin-film transistors or Schottky diodes commonly present multiple parameters of electrical characteristic, which can be beneficially exploited to provide more information than sensors based on purely resistive or capacitive response. We manufactured Schottky diodes using spray-coated ZnO and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as an easy, simple and low-cost method for producing multiparametric UV-photodetectors. The diode parameters presented rectification ratios (RR) as high as 104 and ideality factors as low as 1.3, and their characteristic curves were analyzed by Cheung's method to determine the effect of UV irradiation on the ideality factor, series resistance and Schottky barrier height. The study of the photocurrent response from spray-coated ZnO films as a function of geometric parameters and UV intensity demonstrated a transition from bimolecular to monomolecular recombination process at higher irradiance values, as a result of the adsorption/desorption dynamics of molecular oxygen at the semiconductor/air interface. São Paulo State University – UNESP Faculty of Science and Technology (FCT) Physics Department São Paulo State University – UNESP Institute of Geosciences and Exact Sciences (IGCE) Physics Department São Paulo State University – UNESP Faculty of Science and Technology (FCT) Physics Department São Paulo State University – UNESP Institute of Geosciences and Exact Sciences (IGCE) Physics Department FAPESP: 2018/04169-3 FAPESP: 2019/01671-2 FAPESP: 2019/08019-9

Esta pesquisa teve como objetivo estudar a distribuição espacial do Aedes aegypti em escolas públicas do município de Bezerros-PE. Com o intuito de avaliar áreas vulneráveis a transmissão de arboviroses, no período de junho a novembro de 2018. Foram utilizadas armadilhas de oviposição para avaliar os quantitativos de ovos e coletados um total de 3.277 ovos, sendo estes 2.898 viáveis e 379 inviáveis. Após esse levantamento, foi possível correlacionar os dados climáticos, índices entomológicos e socioeconômicos e classificar a área em risco, alerta e controle para a transmissão de arboviroses.

Made available in DSpace on 2020-12-12T02:43:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Universidade Estadual Paulista Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the dielectric layer of thin-film transistors (TFTs). Growth of aluminum-oxide layers from anodization of metallic aluminum films is greatly advantageous when compared to sophisticated processes such as atomic layer deposition (ALD) or deposition methods that demand relatively high temperatures (above 300 °C) such as aqueous combustion or spray-pyrolysis. However, the electrical properties of the transistors are highly dependent on the presence of defects and localized states at the semiconductor/dielectric interface, which are strongly affected by the manufacturing parameters of the anodized dielectric layer. To determine how several fabrication parameters influence the device performance without performing all possible combination of factors, we used a reduced factorial analysis based on a Plackett-Burman design of experiments (DOE). The choice of this DOE permits the use of only 12 experimental runs of combinations of factors (instead of all 256 possibilities) to obtain the optimized device performance. The ranking of the factors by the effect on device responses such as the TFT mobility is possible by applying analysis of variance (ANOVA) to the obtained results. School of Technology and Sciences São Paulo State University-UNESP Scholl of Electronic Engineering Bangor University Institute of Geosciences and Exact Sciences São Paulo State University-UNESP School of Technology and Sciences São Paulo State University-UNESP Institute of Geosciences and Exact Sciences São Paulo State University-UNESP FAPESP: 14/13904-8 FAPESP: 16/03484-7 FAPESP: 19/01671-2 FAPESP: 19/05620-3 FAPESP: 19/08019-9

Made available in DSpace on 2020-12-12T01:53:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Polymer light-emitting electrochemical cells (PLECs) are organic electronic devices which operating mechanism depends on the injection and transport of electronic charge carrier and the electrochemical doping of the organic semiconductor. The details of the interactions between the salt (or its ions) and the semiconducting polymer composing the device active layer provide important information about the electronic processes associated to the device operation in steady-state. In this context, the present paper proposes a study where theoretical results from Density Functional Theory (DFT) were obtained for three different steady-state operational regimes: i) without external voltage, in which the undissociated salt molecules interact with uncharged semiconducting polymer; ii) for applied voltages lower than the device turn-on (VEg/e), in which the dissociated ions interact with charged semiconducting polymer. In addition, the theoretical results have been confronted with experimental results of PLECs fabricated using different salt concentrations. For both theoretical and experimental approaches, we considered lithium triflate as the salt compound and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-vinylenephenylene)] (F8PV) as the semiconducting polymer. We observed substantial changes in the electronic structure of the systems at the different operating regimes, which were interpreted in terms of the electronic charge injection from the electrodes and the electrochemical doping of the semiconducting polymer. São Paulo State University (UNESP), Posmat São Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Physics Department University of São Paulo São Carlos Institute of Physics, São Carlos São Paulo State University (UNESP) School of Sciences Physics Department São Paulo State University (UNESP) Campus of Itapeva São Paulo State University (UNESP), Posmat São Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Physics Department São Paulo State University (UNESP) School of Sciences Physics Department São Paulo State University (UNESP) Campus of Itapeva CNPq: 133770/2017-6 FAPESP: 2007/58991-1 FAPESP: 2013/24461-7 FAPESP: 2014/20410-1 CAPES: 23038.004680/2015-01 CNPq: 420449/2018-3 CNPq: 448310/2014-7

Made available in DSpace on 2022-04-28T19:40:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Volatile organic compounds (VOCs) are environmental pollutants that pose risks to the human health even at very low concentrations. Therefore, fast and sensitive analytical methods capable to discriminate VOCs are highly demanded. Herein, we have successfully synthetized and characterized TiO2 nanofibers (NF) by electrospinning and TiO2 nanoparticles (NP) by sol-gel method to be employed in an electronic nose (e-nose) for monitoring VOCs. Electrical comparison between TiO2-NF and TiO2-NP indicated that the former presented better electrical response, which can be attributed to the better charge transfer along the nanofiber framework. The TiO2 nanostructures were combined with three different polymers, namely poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), polypyrrole (PPy), and polystyrene sulfonate (PSS), which obtained nanocomposites were deposit by drop casting onto gold interdigitated electrodes and used as sensing units of the e-nose. Electrical impedance spectroscopy measurements were employed to collect the e-nose electrical resistance data, which were treated by Principal Component Analysis (PCA), revealing the system was able to discriminate the three VOCs. Our results indicate that the e-nose system has potential to be employed as a rapid and simple alternative in the detection of VOCs. Nanotechnology National Laboratory for Agriculture (LNNA) Embrapa Instrumentação PPGQ Department of Chemistry Center for Exact Sciences and Technology Federal University of São Carlos (UFSCar) Institute of Chemistry Federal University of Bahia (UFBA) Institute of Geosciences and Exact Sciences São Paulo State University (UNESP) Institute of Geosciences and Exact Sciences São Paulo State University (UNESP) FAPESP: 2016/23793-4 FAPESP: 2017/12174-4 FAPESP: 2018-22214-6 FAPESP: 2018/08012-1

Made available in DSpace on 2020-12-10T20:06:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Recent studies have shown spray-pyrolysis is a low-cost, simple and efficient technique for deposition of metal oxide semiconductors (such as zinc oxide) as the active layer of thin-film transistors (TFTs). However, to allow the translation from laboratory scale to industry the reproducibility of such method needs to be evaluated. We present herein a representative study concerning the reproducibility and uniformity of spray-coated ZnO TFTs using several devices, from different production batches, following the same fabrication protocol. We demonstrate that it is possible to obtain transistors with high performance and reproducibility by controlling the most relevant deposition factors, corroborated by a low deviation rate (below 10%) from the characteristic TFT parameters (mobility in saturation, threshold voltage and on/off ratio), which is compatible to commonly available commercial electronic devices. Sao Paulo State Univ UNESP, Phys Dept IBILCE, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IGCE, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IBILCE, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IGCE, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil FAPESP: 2019/08019-9 CAPES: 001

Made available in DSpace on 2020-12-12T01:28:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Instituto Nacional de Ciência e Tecnologia em Eletrônica Orgânica The electrical properties of polymeric films/blends comprising polyaniline (PANI) and cashew gum (CG) blends were studied by impedance spectroscopy in the temperature range from 300 K to 353 K. Protonation promoted by sulfuric acid was responsible for changing the oxidation state from undoped emeraldine base (EB) to doped emeraldine salt (ES). The low-frequency conductivity of the films varied more than 6 orders of magnitude by doping. In (PANI- EB)/CG blends, the presence of cashew gum acts a dispersing agent, lowering the electrical conductivity contrasting to (PANI-ES)/CG blends, where the electrical conductivity increases with CG concentration up to 20% (w/w). Moreover, undoped films presented a thermally-activated electrical conductivity, whereas doped films presented a decrease in the conductivity by increasing temperature. An equivalent circuit model is proposed to analyze the data by considering the system being composed of highly conductive regions separated by insulating/semiconducting ones. Instituto de Física de São Carlos Universidade de São Paulo Instituto Federal do Maranhão - IFMA Campus de São João dos Patos Universidade Estadual Paulista - UNESP Departamento de Física Universidade Federal do Piauí - UFPI Departamento de Física Universidade Estadual Paulista - UNESP Departamento de Física

The present study reports a two-level multivariate analysis to optimize the production of anodized aluminum oxide (Al2O3) dielectric films for zinc oxide thin-film transistors (TFTs). Fourteen perf...

Made available in DSpace on 2018-12-11T17:02:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-08-01 We present a study of the electrical properties of electrochemically doped conjugated polymers using polymeric light-emitting electrochemical cells (PLECs) and interpreting the results according to a phenomenological model (PM) which assumes that, above the device turn-on voltage, the bulk transport properties of the doped organic semiconductor are responsible for the main contribution to the whole device conductivity. To confirm the predictions of this model, the dependence of the conductivity of PLECs with different parameters is evaluated and compared with the behavior expected for a doped semiconducting polymeric material. The organic semiconductor doping level, the blend concentration of organic semiconducting molecules, the device thickness, the charge carrier mobility, and the temperature are the parameters varied to perform this analysis. We observed that the device conductivity is independent of the active layer thickness, weakly dependent on the temperature, but strongly dependent on the semiconductor doping level, on the semiconductor fraction in the blend, and on the intrinsic charge carrier mobility. These results were well described by the variable range hopping (VRH) model, which has been widely employed to describe the charge transport in doped semiconducting polymeric materials, confirming the prediction of the phenomenological model. The current analysis demonstrates that PLECs are a suitable system for studying, in situ, the electrochemical doping of semiconducting polymers, permitting the evaluation of material properties as, for instance, the density of electronic charge carriers (and, consequently, the ionic charge carrier concentration) necessary to achieve the maximum electrochemical doping level of the organic semiconductor. Departamento de Física Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista – UNESP Instituto de Física de São Carlos Universidade de São Paulo Departamento de Física Instituto de Biociências Letras e Ciências Exatas Universidade Estadual Paulista – UNESP Departamento de Física Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista – UNESP Departamento de Física Instituto de Biociências Letras e Ciências Exatas Universidade Estadual Paulista – UNESP

Made available in DSpace on 2019-10-06T16:38:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Thin-film transistors (TFTs) with the active layer composed by zinc oxide (ZnO) deposited via spray-pyrolysis present several advantages such as high electrical performance, high optical transmittance in the visible spectrum, low production cost and the ability to cover large areas. Besides the traditional application in electronic/optoelectronic circuits, ZnO TFTs can also be used in sensing devices due to its responsivity to UV-light. In the present work, we performed a bi-level full multifactorial analysis of TFT performance parameters exposed to UV-light. Characterization conditions like UV-light irradiance and time after UV exposure, as well as processing parameters such as annealing temperature were varied simultaneously, allowing the application of analysis of variance (ANOVA) to investigate the effect of these factors on the electrical performance of the devices. Field-effect mobility, threshold voltage, on/off current ratio and the device intrinsic current were among the parameters used as the responses in the factorial analysis. ANOVA was used to determine the ranking of significance of each factor on the different response parameters by the evaluation of the factor effects. Moreover, the results from ANOVA permitted the construction of linear functions used to predict the device responses in the whole range of the experimental conditions, which were confirmed by independent experimental results. The influence of factor interactions and of the linearization of some response parameters was also studied to improve the accuracy of TFT response prediction. Physics Department/IBILCE UNESP – São Paulo State University Physics Department/IGCE UNESP – São Paulo State University, Av. 24A, 1515 Physics Department/IBILCE UNESP – São Paulo State University Physics Department/IGCE UNESP – São Paulo State University, Av. 24A, 1515

Made available in DSpace on 2018-12-11T17:36:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A number of solution-processed electronic materials have been developed for application in printed devices, which are normally built by piling up several coated layers one on the top of the other. To achieve low-cost and simple to manufacture printed devices, stable and easy to process layers are mandatory. Here we introduce a mixture of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with 3-glycidoxypropyltrimethoxysilane (GPTMS) as solution-processed material that becomes insoluble in water after film processing. We performed morphological, optical and electrical characterization in the proposed composite and highlight its advantages as a stable transparent electrode in light-emitting diodes as well as in electrochromic devices. Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Sao Carlos Institute of Physics University of São Paulo, PO Box 369 Brazilian Synchrotron Light Laboratory (LNLS) Brazilian Center for Research in Energy and Materials (CNPEM), Campinas Physics Department Institute of Biosciences Language and Exact Sciences São Paulo State University – UNESP Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Physics Department Institute of Biosciences Language and Exact Sciences São Paulo State University – UNESP CAPES: 2015/25069-9 FAPESP: 312025/2016-5

In this paper, a detailed study of the capacitance spectra obtained from Au/doped-polyaniline/Al structures in the frequency domain (0.05 Hz–10 MHz), and at different temperatures (150–340 K) is carried out. The capacitance spectra behavior in semiconductors can be appropriately described by using abrupt cut-off models, since they assume that the electronic gap states that can follow the ac modulation have response times varying rapidly with a certain abscissa, which is dependent on both temperature and frequency. Two models based on the abrupt cut-off concept, formerly developed to describe inorganic semiconductor devices, have been used to analyze the capacitance spectra of devices based on doped polyaniline (PANI), which is a well-known polymeric semiconductor with innumerous potential technological applications. The application of these models allowed the determination of significant parameters, such as Debye length (≈20 nm), position of bulk Fermi level (≈320 meV) and associated density of states (≈2×1018 eV−1 cm−3), width of the space charge region (≈70 nm), built-in potential (≈780 meV), and the gap states’ distribution.

Esta tese de doutorado é o resultado de um estudo dos mecanismos de operação de dispositivos poliméricos emissores de luz, com um particular enfoque nos processos de injeção e transporte de portadores de carga em polímeros derivados do poli(p-fenileno vinileno), PPV. Para tanto, se fez necessário o domínio de todas as etapas de produção e caracterização, desde a síntese química dos polímeros até a fabricação propriamente dita dos dispositivos, as quais são brevemente descritas neste trabalho. Basicamente, dois tipos diferentes de dispositivos foram caracterizados: diodos poliméricos emissores de luz (PLEDs), nos quais a camada ativa é composta por um filme fino (100-500 nm de espessura) do polímero eletroluminescente puro, e células eletroquímicas emissoras de luz (LECs), compostas por blendas do polímero conjugado com um eletrólito polimérico condutor iônico. As propriedades ópticas dos dispositivos foram analisadas através dos espectros de absorção óptica na região do ultravioleta/visível e de emissão (foto e eletroluminescência) enquanto as propriedades de injeção e de transporte de carga foram exploradas através de medidas elétricas de corrente-voltagem (I-V), espectroscopia de impedância no domínio da freqüência (condutividade ac), espectroscopia de fotocorrente e ressonância magnética detectada eletricamente (EDMR). A influência de parâmetros como a estrutura dos dispositivos, os metais utilizados como eletrodos e a temperatura permitiram uma análise mais detalhada de alguns modelos teóricos utilizados na interpretação dos resultados experimentais, fornecendo, dessa forma, um maior conhecimento das propriedades físicas dos materiais estudados. This PhD thesis is an extensive study of the operation mechanisms of polymeric light-emitting devices, with a particular focus on the injection and transport properties of charge-carriers in poly(p-phenylene vinylene), PPV, derivatives. Therefore, it was necessary to dominate all the processes of fabrication and characterization of such devices, from the chemical synthesis of the polymers to the device fabrication, which are briefly described along this work. Two different kinds of devices were studied: polymeric ligh-emitting diodes (PLEDs) composed by a single thin layer (100-500 nm thick) of the pure electroluminescent polymer, and light-emitting electrochemical cells (LECs), which active layers are formed by a blend of the conjugated polymer and an ionic conductive polymeric electrolyte. The optical properties of the devices were analyzed by optical absorption in the ultraviolet-visible range and emission (photo- and electroluminescence) spectra. The charge injection and transport properties were studied by electrical measurements like current-voltage (I-V) curves, impedance spectroscopy in the frequency domain (ac conductivity), photocurrent spectroscopy and electrically detected magnetic resonance (EDMR). The influence of parameters like the device structure, the electrodes work function and the temperature allowed a detailed analysis of some theoretical models commonly used in the interpretation of the experimental results, providing more information about the physical properties of the studied conjugated polymers.

Made available in DSpace on 2018-11-26T16:16:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) INEO nBioNet, Brazil In this study we propose the use of a blend, comprising poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and polyvinyl alcohol (PVA), to be used as flexible, semitransparent and highly conductive material for electronic and optoelectronic devices. The electrical conductivity and optical transmittance of spray-deposited films of the blend, in different thicknesses and at different weight ratios, were studied in order to determine the most appropriate composition for optimal device performance and cost. We propose a direct method to determine the most appropriate blend composition to produce polymeric films with a desired sheet resistance, optical transmittance and cost, by using a diagram which considers the influence of blend composition and film thickness in a light-transmittance versus sheet resistance plot, mediated by the material cost per unit area. In this way, the present study establishes an empirical method to determine the PEDOT: PSS/PVA blend composition to be used as electrode material in optoelectronic devices which satisfies the desired conditions of optical transmittance, sheet resistance and cost-effectiveness. Univ Estadual Paulista UNESP, Dept Fis, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-15054000 Sao Jose Do Rio Preto, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560250 Sao Carlos, SP, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-15054000 Sao Jose Do Rio Preto, Brazil FAPESP: 2008/57706-4 FAPESP: 2012/19005-0 FAPESP: 2012/01624-5

A phenomenological model has been developed to account for the results of impedance/admittance spectroscopy measurements from light-emitting electrochemical cells (LECs) comprising a polymer electrolyte and two different conjugated polymers used as organic semiconductor. The application of a d.c. offset bias superimposed to the a.c. modulation voltage was used to observe the transition from the behavior prior to device operation and after the formation of the electrochemical p-i-n junction. The analysis of the whole device “conductivity” as a function of the applied bias and of the frequency was used to support the assumptions considered to develop the model. The results show that the device, after the p-i-n junction formation, can be considered as composed by two highly conductive electrochemically doped (n and p) regions and a thin (few tens nanometers), insulating layer, where the electrical current is dominated by electronic charge carrier injection via tunneling through a rectangular energy barrier. Before the p-i-n junction formation, there is no doping of semiconductor material, and the device electrical properties are dominated by the intrinsic electronic charge carriers in the organic semiconductor. Results from devices made of organic semiconductors with different band gap energy and different layer thicknesses are used to corroborate the proposed model.

The efficiency of the charge-carrier photogeneration processes in poly(2,5-bis(3′,7′-dimethyl-octyloxy)-1,4-phenylene vinylene) (OC1OC10-PPV) has been analyzed by the spectral response of the photocurrent of devices in ITO/polymer/Al structures. The symbatic response of the photocurrent action spectra of the OC1OC10-PPV devices, obtained for light-excitation through the ITO electrode and for forward bias, has been fitted using a phenomenological model which considers that the predominant transport mechanism under external applied electric field is the drift of photogenerated charge-carriers, neglecting charge-carrier diffusion. The proposed model takes into account that charge-carrier photogeneration occurs via intermediate stages of bounded pairs (excitonic states), followed by dissociation processes. Such processes result in two different contributions to the photoconductivity: The first one, associated to direct creation of unbound polaron pairs due to intrinsic photoionization; and the second one is associated to secondary processes like extrinsic photoinjection at the metallic electrodes. The results obtained from the model have shown that the intrinsic component of the photoconductivity at higher excitation energies has a considerably higher efficiency than the extrinsic one, suggesting a dependence on the photon energy for the efficiency of the photogeneration process.

Understanding the microscopic origin of the dielectric properties of disordered materials has been a challenge for many years, especially in the case of samples with more than one phase. For polar dielectrics, for instance, the Lepienski approach has indicated that the random free energy barrier model of Dyre must be extended. Here we analyse the dielectric properties of a polymer blend made up with the semiconducting poly(o-methoxyaniline) and poly(vinylidene fluoride-trifluorethylene) POMA/P(VDF-TrFE), and of a hybrid composite of POMA/P(VDF-TrFE)/Zn2SiO4:Mn. For the blend, the Lepienski model, which takes into account the rotation or stretching of electric dipoles, provided excellent fitting to the ac impedance data. Because two phases had to be assumed for the hybrid composite, we had to extend the Lepienski model to fit the data, by incorporating a second transport mechanism. The two mechanisms were associated with the electronic transport in the polymeric matrix and with transport at the interfaces between Zn2SiO4:Mn microparticles and the polymeric matrix, with the relative importance of the interfacial component increasing with the percentage of Zn2SiO4:Mn in the composite. The analysis of impedance data at various temperatures led to a prediction of the theoretical model of a change in morphology at 190 ± 40 K, and this was confirmed experimentally with a differential scanning calorimetry experiment.

Photogenerated charge carrier profiles in poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) light-emitting diodes were determined from steady-state photocurrent spectra and transient photocurrent decay measurements. The observation that the photocurrent spectra behavior is strongly dependent on the bias polarity and amplitude suggests the existence of an intrinsic electric field, determined by the difference in the work function of the metallic electrodes, as well as a field dependence on the free charge carrier generation rates. The obtained results reveal built-in voltages of +0.2 and −0.6 V for Au and Al electrodes, respectively. The photocurrent spectra can be semi-quantitatively explained using a simple model which takes into account the internal built-in electric field of the device structure, the band gap energy and the migration/diffusion of the photogenerated charge carriers through the polymeric film. The drift mobility of carriers was investigated by the time-of-flight technique (TOF). The value for the mobility of holes was obtained from the change of slopes in the double logarithmic plot of the transient current and was independent of the applied field. The TOF transients for electrons showed no change of slopes in the double logarithmic plot and the drift mobility of electrons could not be calculated.

A técnica de injeção de cargas por feixe eletrônico em materiais poliméricos pode ser utilizada como uma importante ferramenta no estudo das propriedades elétricas destes materiais. Fenômenos tais como a emissão eletrônica secundária, o transporte e armazenamento de portadores de carga no volume do material, fenômenos de injeção e condutividade induzida por radiação podem ser observados em películas finas de dielétricos lançando mão desta poderosa técnica. Neste trabalho, utilizamos um canhão de elétrons de energia variável (O a 10 keV) na irradiação de amostras de polianilinas, por nós sintetizadas, para o estudo da emissão secundária e de transporte no volume. Alguns experimentos foram também realizados com o poli(fluoreto de vinilideno), que é um polímero bem mais resistivo que as polianilinas. As medidas de emissão eletrônica foram feitas em circuito aberto, enquanto as medidas de transporte foram obtidas em circuito fechado. Neste segundo tipo de configuração, procuramos fazer uma análise do comportamento da corrente através da amostra pela observação de transientes rápidos (da ordem de 10 ms) de corrente gerados pela injeção de pacotes de carga de penetração bem definida a partir da superfície bombardeada. Propriedades elétricas intrínsecas como a condutividade do material e a permissividade elétrica, e extrínsecas como a condutividade na região irradiada foram utilizadas como parâmetros no ajuste dos resultados experimentais. Charge injection in polymeric materials by electron beam is a powerful technique in the study of electrical properties of such materials. Secondary emission, transport and storage phenomena, as well as radiation-induced conductivity are among the subjects related to dielectrics that can be investigated. At present work we used an electron beam system (O to 10 keV) to irradiate polyaniline films, synthesized in our laboratory, and to perform studies of secondary emission and transport phenomena. Some experiments were also carried out with poly(viny1idene fluoride), a more resistivity polymer. Secondary emission measurements were carried out in an open-circuit configuration while the transport ones used a short circuit mode. Fast transient phenomena (about 10 ms) were also studied in details. Intrinsic electric properties, such as conductivity and dielectric constant, and extrinsic ones, like the induced conductivity in the irradiated region of the sample, were obtained in the fitting between the model and the experimental results.

Light-emitting electrochemical cells (LECs) made of electroluminescent polymers were studied by d.c. and transient current-voltage and luminance-voltage measurements to elucidate the operation mechanisms of this kind of device. The time and external voltage necessary to form electrical double layers (EDLs) at the electrode interfaces could be determined from the results. In the low- and intermediate-voltage ranges (below 1.1 V), the ionic transport and the electronic diffusion dominate the current, being the device operation better described by an electrodynamic model. For higher voltages, electrochemical doping occurs, giving rise to the formation of a p-i-n junction, according to an electrochemical doping model.

Made available in DSpace on 2013-08-28T14:08:41Z (GMT). No. of bitstreams: 1 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) Made available in DSpace on 2013-09-30T18:43:40Z (GMT). No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Previous issue date: 2012-09-10 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:02:43Z No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Made available in DSpace on 2014-05-20T14:02:43Z (GMT). No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Previous issue date: 2012-09-10 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Institute of Organic Electronics (INEO) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Frequency-dependent electroluminescence and electric current response spectroscopy were applied to polymeric light-emitting electrochemical cells in order to obtain information about the operation mechanism regimes of such devices. Three clearly distinct frequency regimes could be identified: a dielectric regime at high frequencies; an ionic transport regime, characterized by ionic drift and electronic diffusion; and an electrolytic regime, characterized by electronic injection from the electrodes and electrochemical doping of the conjugated polymer. From the analysis of the results, it was possible to evaluate parameters like the diffusion speed of electronic charge carriers in the active layer and the voltage drop necessary for operation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752438] Univ São Paulo, Inst Fis Sao Carlos, BR-13560250 Sao Carlos, SP, Brazil Univ Estadual Paulista, UNESP, Dept Fis, BR-15054000 Sao Jose do Rio Preto, SP, Brazil Univ Estadual Paulista, UNESP, Dept Fis, BR-15054000 Sao Jose do Rio Preto, SP, Brazil

Neste trabalho, são apresentados os conceitos básicos de calibração radiométrica, fotométrica e colorimétrica de fontes de luz, os quais foram aplicados na prática a três diodos emissores de luz (LEDs) comerciais, utilizados para compor as diferentes sensações de cor que o olho humano percebe na região visível do espectro eletromagnético. Para tanto, um sistema experimental composto por um circuito de controle de corrente para os LEDs e uma esfera integradora artesanal foi montado tanto para a calibração radiométrica e fotométrica inicial quanto para a obtenção de um conjunto de combinações de intensidade e de espectros associadas a diferentes coordenadas colorimétricas CIE (Commission internationale de l'Eclairage). Dessa forma, é possível que o leitor compreenda, de uma forma bastante simples, o processo de composição de cores de um elemento de imagem (pixel) de um monitor ou tela colorida. In the present work, the basic concepts of radiometric, photometric and colorimetric calibration are presented, which were applied to three light-emitting diodes (LEDs) used to compose the different color sensations that the human eye perceives in the visible region of the electromagnetic spectrum. In this sense, an experimental setup comprising a LED drive circuit and a home-made integrating sphere was assembled for the initial radiometric and photometric calibration as well as to obtain a set of intensity and spectral combinations associated to different colorimetric CIE (Commission Internationale de l'Eclairage) coordinates. The reader can, therefore, understand, in a simple manner, the process of color composition inside a color monitor or display picture element (pixel).

In the past years, organic electrochemical transistors (OECTs) have emerged as potential transducers inapplications that require the conversion of ion fluxes to electronic current. For the rational optimization and understanding of the fundamentals of OECTs and OECT-based applications, however, it is essential to have theoretical models capable to predict experimental data. Within drift-diffusion models,ion flux from the electrolyte into the organic semiconducting layer is considered to take place due to the action of an electrical field, but also because of diffusion processes generated by the concentration gradients. The governing equation of the drift-diffusion model is the Nernst-Planck equation.Thus, in this project, a numerical approach is followed in order to solve the Nernst-Planck equation in one dimension,and model the ion migration from the electrolyte to the semiconductor. To evaluate the accuracy of the implementation, standard boundary conditions used in the literature to solve analytically the drift-diffusion equations were considered.In doing so,the numerical results were in good agreement with the analytical solutions,achieving maximum errors in the order of 1%. Aiming to a better representation of OECTs, closed boundary conditions are considered. Here, the temporal evolution of the concentration profiles showed a convergence to an exponential steady state distribution, which is in good agreement with the result expected theoretically. A further situation investigated was the consideration of a non-uniform electric field acting on the system, assumed to be finite in the electrolyte regionandzerointhe semiconductor.This Consideration impacts principally the temporal evolution of the concentration in each region. In order to consider the distinct compositions in electrolyte and semiconductors, different values of diffusion coefficients were introduced for each region. This extension has visible impacts in the time that the system needs to achieve the steady state. Moreover, the introduction of the chemical potential gradient as the driving force of diffusion leaded to significant variations in the results obtained with the model. Here,the so-called uphill diffusion reported in the literature was observed. With the numerical approach,it was possible to consider different types of pulsed gate voltages, which allowed to simulate the charge and discharge processes of OECTs. For all cases, oscillatory curves similar to experimental measurements were obtained. Therefore, the numerical approach allowed to go beyond the analytical description, and develop an extensive investigation of the impact that different considerations have in the results. Nos últimos anos, os transistores eletroquímicos orgânicos (OECTs) surgiram como transdutores em aplicações que requerem a conversão de fluxos iônicos em corrente eletrônica. Para a otimização e compreensão dos fundamentos das OECTs e suas aplicações, é essencial ter modelos teóricos capazes de prever dados experimentais. Nos modelos de drift-diffusion, o fluxo de íons do eletrólito para a camada semicondutora orgânica é considerado como tendo lugar devido à ação de um campo elétrico, mas também devido aos processos de difusão gerados pelos gradientes de concentração. A equação governante do modelo de drift-diffusion é a equação de Nernst-Planck. Assim, neste projeto, uma abordagem numérica é seguida para resolver a equação de Nernst-Planck em uma dimensão e modelar a migração iônica do eletrólito para o semicondutor. Para avaliar a precisão da implementação, foram consideradas as condições de contorno padrão utilizadas na literatura para resolver analiticamente as equações de drift-diffusion. Ao fazê-lo, os resultados numéricos obtidos mostraram boa concordância com as soluções analíticas, alcançando erros na ordem de 1% .Visando uma melhor representação das OECTs, são consideradas as condições de contorno fechado. Aqui, a evolução temporal dos perfis de concentração mostraram uma convergência para uma distribuição exponencial no estado estacionário, que está em boa concordância com o resultado esperado teoricamente. Adicionalmente, foi considerado um campo elétrico não uniforme atuando sobre o sistema, assumido como finito na região do eletrólito e zero no semicondutor. Esta consideração afeta principalmente a evolução temporal da concentração em cada região. Como objetivo de considerar as composições distintas em eletrólitos e semicondutores, foram introduzidos diferentes valores de coeficientes de difusão para cada região. Esta extensão tem impactos visíveis no tempo que o sistema precisa para alcançar o estado estacionário. Além disso, a introdução do gradiente do potencial químico como a força responsável da difusão dos íons levou a variações significativas nos resultados obtidos como modelo. Aqui, a chamada difusão scendente relatada na literatura foi observada. Com a abordagem numérica, foi possível considerar diferentes tipos de tensões pulsadas no eletrodo da porta, o que permitiu simular os processos de carga e descarga dos OECTs. Para todos os casos, foram obtidas curvas oscilatórias semelhantes às medidas experimentais. Portanto, a abordagem numérica permitiu ir além da descrição analítica, e desenvolver uma extensa investigação do impacto que diferentes considerações têm nos resultados.

Esta tese explora o conceito de sistemas computacionais semi-automatizados de diagnóstico baseados em Aprendizado de Máquina (AM), em que diferentes tipos de dados de biossensores e de outras fontes são empregados. A partir de um pipeline base de AM, foram desenvolvidas quatro aplicações e diversos métodos foram implementados para cada uma das etapas/tarefas do pipeline. Como foram selecionados problemas desafiadores, um alto desempenho na acurácia do diagnóstico em geral só foi alcançado com algoritmos de AM supervisionado. Três aplicações foram em diagnóstico de câncer, sendo a primeira a partir de imagens de microscopia eletrônica de genossensores que detectam o biomarcador de PCA3 para câncer de próstata. Essas imagens foram usadas como entrada para algoritmos de AM supervisionado. Com os atributos de textura Local Complex Features and Neural Network (LCFNN) e o algoritmo Linear Discriminant Analysis (LDA) obteve-se uma taxa de acerto de 99,9% para classificação binária (sim/não para PCA3) e 88,3% para a classificação multiclasse em que se determina a concentração do biomarcador de PCA3. As outras duas aplicações envolveram a detecção de biomarcadores de câncer a partir de medidas elétrica/eletroquímica. A concentração da proteína p53, importante marcador de diferentes tipos de câncer, em amostras de urina e saliva sintéticas, foi determinada a partir de medidas eletroquímicas com imunossensores, em que voltamogramas foram analisados com os algoritmos Logistic Regression (LR), LDA, Support Vector Machine-kernel linear (SVM- L), Gaussian Naive Bayes (GNB), K-Nearest Neighbors (KNN) e Decision Tree (DT). O imunossensor otimizado exibiu acurácia de 100% com todos os algoritmos na maioria dos conjuntos de atributos construídos a partir dos dados brutos. No diagnóstico de câncer de boca, a partir de medidas de impedância elétrica com uma língua eletrônica em amostras de saliva de pacientes e voluntários, a maior acurácia de 86.7% foi obtida com o algoritmo SVM-kernel radial. Nesta aplicação, a acurácia da classificação multiclasse aumentou quando foram adicionadas informações clínicas dos pacientes, indicando a importância de combinação de diferentes tipos de dados nos sistemas computacionais. A quarta aplicação foi o diagnóstico de COVID-19 com a detecção da proteína S do SARS-CoV-2 a partir de mapas hiperespectrais de Espectroscopia Raman com Amplificação de Superfície (SERS) obtidos de imunossensores. Usando algoritmo LDA obteve-se uma acurácia de 100% na distinção dos mapas para resultado positivo e negativo para SARS-CoV-2. Os resultados dessas quatro aplicações demonstram a possibilidade de se desenvolverem sistemas automatizados de diagnóstico, pois as várias etapas/tarefas dos pipelines de AM podem ser implementadas sem necessidade de intervenção humana, mesmo quando se combinam imagens, dados clínicos e de testes clínicos. This thesis explores the concept of computer-assisted diagnosis based on machine learning (ML), in which different types of data from biosensors and other sources are employed. Using a ML pipeline, we developed four applications using different methods in the steps of the pipeline. Because the diagnostic problems addressed were all challenging, a high performance in accuracy was only achieved with supervised ML algorithms. Three applications involved cancer diagnosis, the first being from electron microscopy images of genosensors that detect the PCA3 biomarker for prostate cancer. These images were used as input for the ML algorithms, with texture features from Local Complex Features and Neural Network (LCFNN) and the algorithm Linear Discriminant Analysis (LDA) leading to a 99.9% accuracy for binary classification (yes/no for PCA3) and 88.3% accuracy for the multiclass classification where the PCA3 biomarker concentration is determined. The other two applications were related to detection of cancer biomarkers using electrical or electrochemical measurements. The concentration of p53 protein, an important marker of different types of cancer, in synthetic urine and saliva samples was determined from electrochemical measurements with immunosensors, and the voltammograms were analyzed with the Logistic Regression (LR), LDA, Support Vector Machine-kernel linear (SVM-L), Gaussian Naive Bayes (GNB), K-Nearest Neighbors (KNN) and Decision Tree (DT) algorithms. The optimized immunosensor had 100% accuracy with all ML algorithms for most of the datasets with the raw voltammetric data. In the diagnosis of oral cancer using impedance measurements with an electronic tongue in saliva samples from volunteers and patients, the highest accuracy was 86.7% with SVM-kernel radial algorithm. In this application, the accuracy increased when patients clinical information was added, indicating the importance of combining different types of data in computer-assisted diagnosis systems. The fourth application was the diagnosis of COVID-19 with detection of the SARS-CoV-2 S protein using Surface-Enhanced Raman Spectroscopy (SERS). Using the algorithm LDA an accuracy of 100% was achieved in distinguishing spectra for positive and negative result for SARS-CoV-2. The results of these four applications demonstrate the possibility of developing automated diagnostic systems, as the various stages/tasks in the ML pipeline can be implemented without the need for human intervention, even when combining images, clinical information and data from biosensors.

Electrical impedance spectroscopy has been used extensively for sensing and biosensing due to the multiple electrical properties that can be interrogated through varying the frequency of the electrical excitation. An impedance spectroscopy system comprises three main units: signal processing, sensing and data analysis. This Masters Dissertation starts with a detailed revision of these units. We elaborate upon the methods to fabricate sensing units, including the choice of nanomaterials and biomolecules in controlled molecular architectures. Using arrays of sensing units, as electronic tongues, generates large amounts of data that require the use of data analysis methods, which we also revise and include examples of information visualization and machine learning techniques. The main focus of the revision, however, is on the signal processing unit, responsible for generating the excitation signal and performing the impedance readout. This focus is due to the high cost of the impedance spectrometers available in the market, which hampers integration of biosensing systems to be used in the field. A detailed description is given of the methods to develop a portable, fully integrated low-cost impedance analyzer that offers wide impedance magnitude, signal amplitude and frequency ranges. The device referred to as Simple-Z includes the integrated circuit AD5933 and peripheral circuits that allow for fine output amplitude regulation, flexible response amplification, sampling rate control, automatic calibration and external communication. We were able to fabricate a few units of Simple-Z with reproducible results, develop a graphical user interface and apply it successfully in sensing and biosensing, including for SARS-CoV-2 detection. The validity of Simple-Z was confirmed by comparing its results in some of the applications with those obtained with benchtop commercial impedance analyzers. Simple-Z can now be deployed in point-of-care diagnosis systems. Furthermore, owing to its low cost it can be fabricated with mass production to also be used in teaching labs for training students in electrical impedance spectroscopy. A espectroscopia de impedância elétrica tem sido usada extensivamente para (bio) sensoriamento graças às múltiplas propriedades elétricas que podem ser interrogadas por meio da variação da frequência da excitação. Um sistema de espectroscopia de impedância compreende três unidades principais: processador de sinais, sensor e analisador de dados. Esta Dissertação de Mestrado começa com uma revisão detalhada dessas unidades. Revisamos os métodos para fabricar sensores, incluindo a escolha de nanomateriais e biomoléculas em arquiteturas moleculares controladas. O uso de matrizes de sensores, como línguas eletrônicas, gera grandes quantidades de dados que exigem o uso de métodos de análise de dados que também revisamos e incluímos exemplos de visualização de informações e técnicas de aprendizado de máquina. O foco principal da revisão, entretanto, está no processador de sinais, responsável por gerar o sinal de excitação e realizar a leitura de impedância. Esse foco se deve ao alto custo dos espectrômetros de impedância disponíveis no mercado, o que dificulta a integração de sistemas de biossensoriamento para serem utilizados em campo. É fornecida uma descrição detalhada dos métodos para desenvolver um analisador de impedância portátil, totalmente integrado e de baixo custo que oferece amplas faixas de magnitude de impedância, de amplitude de sinal e de frequência. O dispositivo, nomeado Simple-Z, inclui o circuito integrado AD5933 e circuitos periféricos para regulagem fina de amplitude de saída, amplificação flexível de resposta, controle da frequência de amostragem, calibração automática e comunicação externa. Fabricamos algumas unidades de Simple-Z com resultados reprodutíveis com uma interface gráfica e aplicamos com sucesso em (bio)sensoriamento, incluindo a detecção de SARS-CoV-2. A validade do Simple-Z foi confirmada comparando seus resultados em algumas das aplicações com aqueles obtidos com analisadores de impedância comerciais de bancada. O Simple-Z agora pode ser implantado em sistemas de diagnóstico para uso em campo. Além disso, graças ao seu baixo custo, pode ser fabricado com produção em massa para ser utilizado também em laboratórios de ensino para treinamento de alunos em espectroscopia de impedância elétrica.

Um dos grandes diferenciais dos materiais semicondutores orgânicos é sua habilidade de suportar, em determinadas situações, transporte eletrônico e iônico simultaneamente. Essa habilidade possibilitou tais condutores mistos a serem aplicados com grande sucesso em dispositivos de interesse biológico. Um exemplo é o transistor eletroquímico orgânico (OECT). Esse dispositivo é formado por uma camada semicondutora orgânica, delimitada por dois eletrodos (fonte e dreno), que forma o canal do transistor. Esta camada fica em contato com uma solução eletrolítica, que contém um eletrodo denominado porta. Durante a operação, aplica-se uma tensão no eletrodo porta, o que induz troca iônica entre o polímero e o eletrólito. Isso altera o estado de dopagem do canal, levando a uma mudança na corrente extraída entre fonte-dreno. Um dos principais pontos de interesse é o de aprimorar o desempenho destes dispositivos, a partir da compreensão das propriedades fundamentais do material do canal, e como ele se comporta na presença de diferentes íons. Para tal estudo, foram confeccionados OECTs com poli(3,4-etileno dioxitiofeno):poliestireno sulfonado (PEDOT:PSS) como camada ativa. A resposta elétrica e morfológica dos OECTs foi caracterizada utilizando diversos eletrólitos aquosos, com concentração de 100 mM, a saber: NH4Cl, KCl, NaCl, CaCl2 e MgCl2. Os resultados demonstram que íons com menor raio iônico e maior esfera de hidratação resultam em dispositivos com maior fator de mérito (μC*). Uma vez que filmes de PEDOT:PSS absorvem água, analisamos a diferença entre a quantidade de água absorvida para as diferentes espécies iônicas. Os resultados demonstram que a quantidade de água cresce seguindo a mesma ordem do fator de mérito e este aumento é de aproximadamente 100% quando comparamos os resultados extremos. Além disso, realizamos um estudo da capacitância volumétrica em função da espessura do filme, com o intuito de avaliar a influência da espécie iônica na sua profundidade de penetração no volume do canal. Observamos que a capacitância volumétrica decai para espessuras superiores a 800 nm quando utilizamos KCl e superiores a 1200 nm para MgCl2. Deste modo, nossos resultados demonstram que a natureza da espécie iônica tem impacto importante na resposta dos dispositivos. Essa compreensão é indispensável para busca/desenvolvimento de novos materiais para compor a camada ativa do dispositivo e para a compreensão dos mecanismos biológicos. Organic semiconductor materials are able to support both electronic and ionic transport. This ability enabled such mixed conductors to be applied with great success in devices of biological interest. An example is the organic electrochemical transistor (OECT). In a typical OECT, the active channel is placed in contact with an electrolyte solution containing a gate electrode. During operation, application of a gate voltage induces ion exchange between the polymer and the electrolyte. This changes the doping state of the channel, leading to a change in the source-drain current. One of the main points of interest is to improve the performance of these devices, start from the understanding of the fundamental properties of the channel material, and how it operates in the presence of different ions. Here, we produced poly(3,4-ethylene dioxithiophene):sulfonated polystyrene (PEDOT:PSS) - based OECTs. The electrical and morphological properties of the OECTs were characterized using different aqueous electrolytes, with concentration of 100 mM, namely: NH4Cl, KCl, NaCl, CaCl2 and MgCl2. The results demonstrate that ions with a smaller ionic radius and a larger dehydration sphere result in devices with a higher factor of merit (μC*). Once PEDOT:PSS films absorb water, we analyze the difference between the amount of water absorbed for the different ionic species. The results show that the amount of water grows following the same order as the factor of merit and this increase is approximately 100% when we compare the extreme results. Besides that, we carry out a study of the volumetric capacitance as a function of the thickness film, in order to evaluate the influence of the ionic species on its depth of penetration in the volume of the channel. We observe that the volumetric capacitance decreases for thicknesses greater than 800 nm when using KCl and greater than 1200 nm for MgCl2. Thus, our results demonstrate that the nature of the ionic species has an important impact on the response of the devices. This understanding is indispensable for the search/development of new materials to compose the active layer of the device and for the understanding of biological mechanisms.

In the global scenario of increasing environmental concerns over the dependence on fossil fuels, photocatalytic water splitting has been regarded as a promising method for the clean production of hydrogen fuel (H2) from water and sunlight. Despite recent advancements, only a few materials can be efficiently applied as photocatalysts for this reaction. In this context, sodium tantalate (NaTaO3) is highly active for H2 evolution, although the wide band gap of 4.0 eV precludes its practical application for solar water splitting. Therefore, a variety of band-gap narrowing approaches for this compound have been recently proposed, including bismuth doping. In this work, Bi-doped NaTaO3 with a nanocubic morphology has been obtained through a simple molten salt method, in order that Bi3+-Ta5+ atomic substitutions promote the formation of midgap electronic states which allow the absorption of light from the simulated sunlight spectrum (AM 1.5G). X-ray diffraction results reveal that the orthorhombic perovskite structure of NaTaO3 undergoes a structural transition to pseudocubic upon low-concentration (0.5-4 mol%) Bi-doping. Accordingly, the Bi-doped photocatalysts present considerable H2 evolution under simulated sunlight, whereas pristine NaTaO3 exhibits negligible activity in these conditions. The highest H2 evolution rates are obtained with 3 mol% Bi-doped NaTaO3, as a possible consequence of the conjunction between the narrowed band gap of 3.6 eV with the rectified Ta-O-Ta bond angles in the pseudocubic lattice. Moreover, the photocatalytic activity is further improved and kept stable for 110h of reaction after Ni co-catalysts are loaded onto Bi-doped NaTaO3 by magnetron sputtering deposition, in order that the nanosized Ni particles may provide abundant surface reaction sites for the evolution of H2. Em vista do cenário global de crescentes preocupações ambientais a respeito da atual dependência em combustíveis fósseis, a divisão fotocatalítica da água tem sido considerada uma das mais promissoras estratégias para a produção limpa de hidrogênio (H2) a partir da água e da luz solar. Apesar dos avanços recentes, observa-se que poucos materiais podem ser aplicados de forma eficiente como fotocatalisadores para esta reação. Neste contexto, o tantalato de sódio (NaTaO3) mostra-se altamente ativo para a evolução de H2, ainda que sua larga banda proibida de 4.0 eV impeça sua aplicação prática sob luz solar. Portanto, diversos métodos para o estreitamento desta banda proibida tem sido recentemente propostos, sendo um destes a dopagem com bismuto. Neste trabalho, NaTaO3 dopado com Bi foi produzido de forma simples pelo método de sal fundido, de modo que a substituição atômica Bi3+-Ta5+ promove a formação de estados eletrônicos na região da banda proibida, permitindo assim a absorção de luz solar simulada (espectro AM 1.5G). Resultados de difração de raios-X revelam que a estrutura da perovskita ortorrômbica, característica do NaTaO3 puro, se converte para uma perovskita pseudocúbica sob baixas concentrações do dopante (0.5-4 mol% Bi). Como consequência destas modificações, o fotocatalisador dopado com Bi apresenta uma significativa evolução de H2 sob luz solar simulada, em contraste com a atividade nula do NaTaO3 puro, sob estas mesmas condições. As mais altas taxas de produção de hidrogênio foram obtidas com NaTaO3 dopado a 3 mol% Bi, possivelmente como resultado conjunto do band gap de 3.6 eV com os ângulos Ta-O-Ta retificados na rede pseudocúbica. Subsequentemente, a atividade catalítica é potencializada e se mantém estável por 110h após a deposição do cocatalisador Ni por pulverização catódica, evidenciando que as nanopartículas de Ni provém abundantes sítios ativos para a evolução de H2 na superfície do NaTaO3 dopado com Bi.

A condutividade elétrica do poli (3,4-etilenodioxietiofeno) com poliestirenosulfonato (PEDOT: PSS) depende significativamente de sua morfologia, microestrutura e número de contra íons que equilibram as cargas dopantes positivas transportadas pelas cadeias conjugadas do PEDOT. No entanto, devido à alta solubilidade em água e solventes polares em geral dos domínios de PSS, os filmes PEDOT:PSS facilmente dissolvem quando expostos a tais solventes. A fim de evitar essa dissolução, normalmente são adicionados agentes de reticulação à solução de polímero, para estabilizar o filme em estado sólido. Como consequência da adição de reticuladores, tanto a morfologia do filme quanto a condutividade iônico-eletrônica são impactadas negativamente, gerando filmes com desempenho inferior às amostras sem adição de agentes reticuladores. Neste trabalho, objetivamos analisar o comportamento dos filmes PEDOT:PSS misturados com diferentes agentes de reticulação, a saber, o 3-glicidiloxipropiltrimetoxissilano (GOPS), o 3-cloropropiltrimetoxissilano (Cloro), o 3-Trimetoxisilil-Propil-Metacrilato (Trime) e o Viniltrimetoxisilano (Vinil). A condutividade elétrica foi avaliada por meio de medidas de quatro pontas, revelando que o filme PEDOT: PSS reticulado com GOPS, reticulador tradicionamente utilizado em aplicações em bioeletrônica, apresenta a menor condutividade eletrônica – reduzindo a condutividade do PEDOT:PSS puro em mais de 40%. Já os demais agentes reticulantes, Cloro, Vinil e Trime, também apresentaram redução da condutividade, quando comparada ao do PEDOT:PSS puro, porém menor do que a do GOPS. Em relação ao desempenho de Transistores Eletroquímicos Orgânicos (OECTs), mostramos que os reticuladores Cloro e Vinil apresentam o maior desempenho entre os agentes analisados. Mostramos também que a capacitância volumétrica (C*) dos filmes é pouco impactada pelos reticuladores. Nosso trabalho sugere que o uso de agentes de reticulação otimizados pode melhorar o desempenho dos dispositivos condutores iônico-eletrônicos mistos PEDOT:PSS. The electrical conductivity of poly(3,4-ethylenedioxidethiophene) with polystyrenesulfonate( PEDOT: PSS) depends significantly on its morphology, microstructure and number of counter ions that balance the positive doping charges carried by the conjugated PEDOT chains. However, due to the high solubility of PSS-rich domains in water or other polar solvents, PEDOT:PSS films easily undergo dissolution when exposed to such solvents . In order to prevent such dissolution, crosslinking agents are normally added to the polymer solution, prior to film formation, to stabilize the solid-state film. As consequence of crosslink addition, both the film morphology and electronic/ionic conductivity are negatively impacted, generating films with lower performances when compared to crosslink-free samples. Here we aim to analyze the behavior of PEDOT:PSS films mixed with different crosslinking agents, namely the (3-Glycidyloxypropyl)trimethoxysilane (GOPS), (3-Chloropropyl)trimethoxysilane (Cloro), 3-(Trimethoxysilyl)propyl methacrylate (Trime), and Vinyltrimethoxysilane (Vinil) . The electrical conductivity was evaluated by means of four-probe measurement, revealing that the PEDOT: PSS film crosslinked with GOPS, a crosslinker traditionally used in bioelectronics applications, has the lowest electronic conductivity - reducing the conductivity of pure PEDOT: PSS by more than 40%. The other cross-linking agents, Cloro, Vinil and Trime, also showed reduced conductivity when compared to PEDOT: PSS, but far less than that of GOPS. Regarding the performance of Organic Electrochemical Transistors (OECTs), we show that the Cloro and Vinil crosslinkers present the highest performance among the analyzed agents. We also show that the volumetric capacitance (C*) of the films is little impacted by the crosslinkers. Our work suggests that the use of more optimized crosslinking agents can improve the performance of PEDOT: PSS mixed ionic-electronic conductive devices.

Um desafio central na área das ciências da saúde e biomédica tem sido o desenvolvimento de testes clínicos embasados em novas tecnologias que resultem em medidas precisas, com resultados consistentes mais rápidos que os convencionais, e ao menor custo possível. Os esforços atuais têm se concentrado em integrar a análise de materiais biológicos a componentes de circuitos integrados compatíveis com a indústria de semicondutores existente. Nesse contexto, esse trabalho apresenta duas contribuições a partir do uso de materiais nanoestruturados alótropos do carbono. Primeiramente, demonstramos como o desempenho de um sensor de pH embasado na tecnologia EGFET (Extended Gate Field Effect Transistor) pode ser controlado com a incorporação de grafenos, com diferentes graus de funcionalização, a eletrodos de FTO (Fluorine doped Tin Oxide). Os eletrodos de FTO foram modificados através da deposição dos materiais nanoestruturados de carbono via eletroforese. O desempenho dessas amostras como sensor de íons H+ mostrou dependência quanto ao tempo de deposição e composição tampão utilizado, tendo seu desempenho aumentado em até 24%, atingindo uma sensibilidade máxima de 67 mVopH-1 para tampão fosfato. A segunda contribuição desse trabalho trata-se da combinação das informações obtidas com um arranjo de dispositivos de NTFETs (Nanotubes Field Effect Transitors) decorados com nanopartículas metálicas e análise de discriminantes lineares, empregados na classificação de diferentes populações celulares. O método proposto foi capaz de identificar e classificar corretamente entre as linhagens de células cancerígenas B16 (melanoma), 3LL (carcinoma) e 3L4 (linfoma), além de distingui-las corretamente de suas contrapartes saudáveis. Adicionalmente, utilizamos esse conjunto de dados para classificar uma população celular desconhecida, demonstrando uma possível utilidade clínica da metodologia desenvolvida. A central challenge in the biomedical field has been the development of new approaches for clinical tests based on microelectronic technologies, aiming trustful and precise results, faster and cheaper than the standard techniques. Current efforts have focused on integrating the analysis of biological samples and integrated circuit components compatible with the standard semiconductor industry. In this context, the present work gives two contributions on the usage of carbon nanostructure allotropes. First, we show how the performance of pH sensors based on EGFET (Extended Gate Field Effect Transistor) can be tuned with the integration of graphene nanosheets, with different degrees of functionalization, into FTO (Fluorine doped Tin Oxide) electrodes. The FTO electrodes were modified through EPD (electrophoretic deposition) of the carbon nanomaterials. The device performance as pH sensor showed dependence on the time of deposition and buffer composition, increasing up to 24% compared to the bare FTO electrode and reaching a maximum sensitivity of 67 mVopH-1 for phosphate buffer. The second contribution of this work regard the combination of the data gathered using an array of NTFETs (Nanotube Field Effect Transistors) decorated with metal nanoparticles and LDA (Linear Discriminant Analysis) to distinguish among different cell populations. The proposed method correctly classifies among the cancer cell lines B16 (melanoma), 3LL (carcinoma), and 3L4 (lymphoma), as well as cancer cells from their healthy counterparts. Additionally, we demonstrated a possible application of the method correctly classifying blind samples.

Os transformadores são equipamentos fundamentais para o sistema elétrico e o acompanhamento regular de suas condições de operação é muito importante para que se reduzam custos associados ao seu ciclo de vida, bem como para que se possa garantir a sua confiabilidade e a sua durabilidade. As falhas elétricas ocorrem, muitas vezes, motivadas pela degradação do sistema isolante e consequentemente danificam o equipamento. O óleo é um dos componentes isolantes que se deteriora com facilidade devido ação de falhas ou variação de temperatura e umidade. O acompanhamento e a manutenção da qualidade do óleo isolante são etapas essenciais para proporcionar uma operação confiável dos equipamentos elétricos garantindo a confiabilidade do fornecimento de energia. Um dos parâmetros que pode ser monitorado no óleo é a água, pois esta reduz drasticamente a rigidez elétrica do dielétrico. Uma revisão na literatura relata alguns procedimentos de diagnósticos disponíveis para avaliar a condição do óleo de transformadores, tais como as análises físico química e a análise de gases dissolvidos (DGA). Pesquisas recentes revelam um tópico ressaltado que consiste na utilização de sensores acústicos para caracterização de líquidos, uma vez que essa análise possui a vantagem de ser não destrutiva, com possibilidade de aplicações não invasivas e em transformadores em operação. Neste contexto, esta tese propõem uma metodologia acústica para contribuir na detecção de umidade no óleo mineral isolante utilizando sensores piezoelétricos. A metodologia consiste na utilização de sensores para emitir e recepcionar os sinais transmitidos através de amostras de óleos de transformadores. Os experimentos foram realizados na faixa de MHz, utilizando transdutores comerciais e na faixa de kHz, utilizando um transdutor piezoelétrico desenvolvido pelo Grupo de Alta Tensão e materiais da USP de São Carlos. Medidas da amplitude do sinal são correlacionadas com o teor de água contido nas amostras de óleos. Os resultados revelam que é possível diagnosticar se as amostras de óleo estão aptas ou não para uso em transformadores. Em alguns casos é possível distinguir as quatro classes das amostras de óleo mineral isolante testadas: óleo novo (virgem), óleo regenerado, óleo sujo e óleo queimado. A metodologia proposta, além de ser inédita, se mostra promissora para auxiliar no diagnóstico de amostras de óleo mineral isolante em campo. Transformers are fundamental equipment in electrical power system and constant monitoring their operating conditions is very important to reduce the costs associated with their life cycle, as well as to guarantee their reliability and durability. One of the main cause of electrical failures in power transformers is the degradation of the power transformer insulation system, which can cause permanent damages. A crucial element in their insulation system is oil used to insulate parts, but also to cool the equipment. Therefore monitor and maintain the insulating oil are essential steps to provide a reliable operation of the electrical equipment guaranteeing the reliability of the power supply. A review in the literature reports a wide variety of diagnostic procedures available to assess the condition of transformer oil, such as physical chemical analysis and dissolved gas (DGA) analysis. Recent research reveals a highlighted topic that consists of the use of acoustic sensors for characterizing liquids, since the acoustic analysis presents the characteristic of being non-destructive with possibility of non-invasive and application during transformer operation i.e. in line. In this context, this thesis proposes an acoustic methodology for the analysis of mineral insulating oil using piezoelectric sensors. The methodology consists of the use of sensors to emit and receive signals transmitted through oil transformer samples. The experiments were carried out in the MHz band, using commercial transducers and in the kHz band, using a piezoelectric transducer developed by the High Voltage and Materials Group from USP of São Carlos. Measurements of signal amplitude are correlated with the water content contained in the oil samples. The results show that it is possible to diagnose whether or not the oil samples are suitable for use in transformers. In some cases it is possible to distinguish the four classes of tested mineral oil samples. The proposed methodology is promising for the diagnosis of mineral insulation oil samples in the field.

Dispositivos baseados em eletrônica orgânica já estão presentes há vários anos no mercado com displays de OLEDs com alta definição de cores e contraste. Atualmente, essas telas são fabricadas com o uso de pequenas moléculas orgânicas depositadas por técnicas de evaporação a vácuo. A possibilidade de deposição dos materiais poliméricos em solução traz vantagens de fabricação com relação a custos e a velocidade de processamento, além de maiores escalas dimensionais. No entanto, diversos entraves técnicos ainda precisam ser superados para garantir desempenho e estabilidade de dispositivos eletrônicos e optoeletrônicos orgânicos. Neste sentido, este trabalho apresenta um equipamento de deposição roll-to-roll de proporções laboratoriais, com o intuito de servir de ponte entre o desenvolvimento acadêmico e as técnicas de produção industriais. Uma primeira versão do equipamento, já apresentado no trabalho de mestrado, foi agora modificado e atualizado com novas funcionalidades. Ele tornou-se mais completo e de operacionalidade mais eficiente, e foi utilizado para a deposição de várias camadas de dispositivos, incluindo a fabricação de eletrodos semitransparentes e da camada ativa de dispositivos luminescentes. Para solucionar as limitações do óxido de estanho e índio (principal condutor semitransparente atualmente) sobre substratos flexíveis, foi validado um eletrodo alternativo, através da síntese e aplicação de nanofios de prata e do polímero condutor PEDOT:PSS por diferentes técnicas de deposição. Também foi investigada a camada ativa de células eletroquímicas emissoras de luz (LEC), depositadas pela técnica slot-die, variando-se o polímero luminescente, de emissão azul, e o solvente utilizado. Por fim, foram fabricados dispositivos luminescentes do tipo LEC com diferentes arquiteturas e sobre diferentes substratos. O dispositivo final apresentado foi fabricado com eletrodos otimizados, depositados por spray com nanofios de prata e PEDOT:PSS, sendo os dois eletrodos semitransparentes. Com isso, obteve emissão em ambas as polaridades e em ambas as direções. Devices based on organic electronics have been present for some years on the market with OLED displays with high color definition and contrast. Currently, these screens are manufactured using organic small molecules deposited by vacuum evaporation techniques. The possibility of deposition of polymeric materials in solution brings manufacturing advantages in terms of costs and processing speed, as well as larger dimensional scales. However, several technical barriers still need to be overcome to ensure performance and stability of organic electronic and optoelectronics devices. In this sense, this work presents roll-to-roll deposition equipment of laboratory proportions, in order to serve as a bridge between academic development and industrial production techniques. A first version of the equipment, already presented in the master\'s work, has now been modified and updated with new functionalities. It has become more complete and more operationally efficient, and has been used for the deposition of several layers of devices, including the manufacture of semitransparent electrodes and the active layer of luminescent devices. To solve the limitations of indium tin oxide (the main semitransparent conductor today) on flexible substrates, an alternative electrode was validated through the synthesis and application of silver nanowires and the PEDOT:PSS conductive polymer by different deposition techniques. It was also investigated the active layer of light-emitting electrochemical cells (LEC), deposited by the slot-die technique, varying the blue-emitting luminescent polymer and the solvent used. Finally, luminescent LEC devices were manufactured with different architectures and on different substrates. The final device presented was manufactured with optimized electrodes, deposited by spray with silver nanowires and PEDOT:PSS, the two electrodes being semi-transparent. With this, it obtained emission in both polarities and in both directions.

A proposta desse estudo é investigar as propriedades de migração do éxciton, transferência de energia e transporte de cargas em heteroestruturas orgânicas ultrafinas compostas pela integração de um polímero semicondutor com moléculas de clorofila. A sintonização dos estados eletrônicos desses materiais torna possível a obtenção de heteroestruturas com modulação energética capazes de aprisionar éxcitons e cargas apresentando potencialidade de aplicação em Diodos Orgânicos Emissores de Luz (OLEDs). Para tal filmes de polifuoreno (PFO) (camada transportadora de carga) totalmente amorfo e filmes de clorofila (camada ativa na forma de poço de potencial) foram preparados utilizando a técnica e automontagem (LBL) combinada com spin-coating, caracterizados por microscopia confocal por varredura a laser e técnicas espectroscópicas de absorção e emissão. Investigou-se os processos fotofísicos utilizando microscopia confocal e de tempo de vida. Os resultados foram interpretados com base no modelo de transferência de energia de Förster combinado com as taxas de Miller-Abrahams e com a equação de difusão excitônica. Com essa abordagem, obteve-se uma relação entre a migração do éxciton no PFO e a transferência de energia não radiativa deste polímero para as moléculas de clorofila. Observou-se uma eficiente transferência de energia igual a 94% no regime de filmes ultrafinos. Para compreender os mecanismos de transporte de carga, implementamos e validamos o método de simulação de Monte Carlo para o transporte de carga em sistemas orgânicos desordenados. Com essa abordagem investigou-se a dinâmica das cargas em filmes poliméricos desordenados com e sem a camada de poço de potencial. Propriedades elétricas, tais como, mobilidade elétrica e coeficiente de difusão, foram obtidas e estão de acordo com os reportados na literatura. Obteve-se uma taxa de preenchimento de cargas no poço de potencial igual a 1010 buracos/s para campo elétrico de 1 MV/cm e constatou-se que a taxa aumenta com o campo elétrico. Tal abordagem apresenta-se como uma alternativa interessante para auxiliar o planejamento experimental de OLEDs baseados em heteroestruturas orgânicas. In this study the exciton migration, energy transfer and charge transport in ultrathin organic heterostructure formed by semiconductor polymer and chlorophyll molecules were investigated. The energetic tuning between these materials promotes organic heterostructures with energetic modulation capable of trapping excitons and charges showing an application potential in Organic Light Emitting Diodes (OLEDS). Amorphous polyfluorenes (PFO) and chlorophyll a (chla) were prepared using self-assembly combined with spin-coating methods and characterized by confocal laser scanning microscopy and spectroscopic techniques. Photophysical processes were investigated using confocal and life-time microscopy and the results interpreted from the model of Förster energy combined with the Miller-Abrahams rate as well as the exciton diffusion equation. These results provided a relationship between the exciton migration in the PFO film and the non-radiative energy transfer from polymer to chla molecules. An efficient transfer of energy equal to 94% was observed. Method of the Monte Carlo simulation were implemented to investigate the charge transport in this disordered organic system. Using this method, the charge dynamics with and no potential well layer was studied. Electrical properties obtained, such as electric mobility and diffusion coefficient, are in agreement with literature. It was estimated a charge fill rate in the potential well equal to 1010 holes/s for 1 MV/cm and this parameter increases with the electric field. This approach has been shown to be an interesting alternative for the experimental design of OLEDs composed by organic heterostructure.

O objetivo principal desta tese foi desenvolver dispositivos microfluídicos do tipo língua eletrônica baseada em espectroscopia de impedância para análise de líquidos complexos. Dois tipos de língua eletrônica foram desenvolvidos. O primeiro com unidades sensoriais fabricadas com eletrodos interdigitados de ouro sobre vidro, selados com microcanal de PDMS, e recobertos com filmes automontados de polímeros condutores, materiais orgânicos e semicondutores. Essa língua eletrônica foi usada para diferenciar os sabores básicos, representados por soluções aquosas de NaCl (salgado), sacarose (doce), cafeína (amargo), HCl (azedo) e glutamato monosódico (umami), distinguir diferentes tipos de cafés, e detectar a presença de gliadina em soluções e alimentos. A distinção foi possível processando-se os dados de magnitude da capacitância com técnicas de projeção multidimensional IDMAP (Interactive Document Map) e análise de componentes principais (PCA). O segundo tipo de língua foi produzido com eletrodos interdigitados de carbono impressos sobre papel com canal hidrofílico e barreiras hidrofóbicas também impresso, modificado com hidrogel funcionalizado com ácido fenil-borônico (PBA) ou polilíquido iônico (PIL). Com dados de capacitância tratados com PCA e IDMAP, a língua foi usada para distinguir soluções dos açúcares glicose, frutose e sacarose, em diferentes concentrações, e diferentes marcas de suco de maçã. Nesta última língua, empregou-se a capacidade de intumescimento de hidrogéis contendo PBA na presença de açúcares, principalmente frutose, que também foi explorada na confecção de sensores com eletrodos de papel que puderam detectar concentrações baixas de glicose, próximas às encontrados no suor humano. Com a tecnologia de sensores em papel e microfluídica, podem-se conceber aplicações futuras, de baixo custo, em sensores na forma de emplastro para monitorar o nível de glicose no suor humano de maneira não invasiva e língua eletrônica para verificar a presença de glúten em alimentos. The main aim of this thesis was to develop microfluidic devices of electronic tongue (e-tongue) type based on impedance spectroscopy to analyze complex liquids. Two types of e-tongue were developed. The first had sensing units fabricated with gold interdigitated electrodes onto glass with a microchannel sealed with PDMS and coated with layer-by-layer films of conducting polymers, organic and semiconductors. This e-tongue was used to distinguish the basic tastes, represented by aqueous solutions of NaCl (salty), sucrose (sweet), caffeine (bitter), HCl (sour) and monosodium glutamate (umami), to distinguish different types of coffees, and detect the presence of gliadin in solutions and food. The distinction was made possible by processing the capacitance data with the multidimensional projection techniques IDMAP (Interactive Document Map) and principal component analysis (PCA). The second type of e-tongue was produced with carbon interdigitated electrodes printed on paper with a hydrophilic channel with hydrophobic barriers, also printed, modified with functionalized hydrogel with phenylboronic acid (PBA) or poly(ionic liquid) (PIL). With capacitance data treated with PCA and IDMAP, the e-tongue was used to distinguish solutions at various concentrations of glucose, fructose and sucrose, in addition to different brands of apple juice. In this latter e-tongue, use was made of the ability of the hydrogel containing PBA to swell in the presence of sugars, mainly fructose, which was exploited in producing sensors with paper electrodes that could detect low concentrations of glucose, close to the values found in human sweat. With the technology of paper-based sensors and microfluidics, one may envisage future low cost applications, including patch sensors to monitor glucose in human sweat in a non-invasive manner and e-tongues to determine the presence of gluten in food.

A importância da pesquisa em eletrônica orgânica, se comparada à microeletrônica convencional baseada principalmente em silício, surge pela presença de inúmeros semicondutores e técnicas de deposição de baixo custo e em grande superfície. Os Transistores de Filmes Finos Orgânicos (OTFTs, do inglês Organic Thin-Film Transistors) são a unidade fundamental em circuitos eletrônicos e, geralmente, apresentam a estrutura de um transistor de efeito de campo. Podem ser fabricados sobre substratos plásticos e oferecem grande número de aplicações como: mostradores, etiquetas de identificação por rádio frequência e eletrônica têxtil. Além disso, há demanda por componentes eletrônicos portáteis e baratos, principalmente como sensores em diagnósticos médicos e veterinários in-situ. A geometria de OTFT mais utilizada em sensores na atualidade é a bottom gate sobre substratos de silício altamente dopado e com óxido de porta inorgânico. Polímeros como poli(3-hexiltiofeno) (P3HT) vêm sendo amplamente utilizados pela comunidade científica, atestando o potencial comercial deste semicondutor em sensores. Neste contexto, esta tese apresenta o desenvolvimento de transistores à base de P3HT como sensores na detecção de analitos em fase vapor. O estudo é composto por uma etapa inicial de caracterização da mobilidade dos portadores de carga por técnicas de transiente de corrente, seguida pela otimização do desempenho de parâmetros elétricos do transistor através de alterações no processamento dos filmes dielétrico e semicondutor. Enfim, conclui-se a investigação através do entendimento dos fatores ligados à degradação do OTFT após exposição à atmosfera e sob estresse elétrico, além do detalhamento da sensibilidade e especificidade do sensor. Sensores de P3HT oferecem enorme potencial de detecção de amônia, cetonas e compostos organoclorados. Outros semicondutores poliméricos são provavelmente necessários para maior especificidade em relação a vapor dágua e álcoois. Research on organic electronics, compared to conventional silicon-based microelectronics, is necessary as it offers plenty of semiconductors and low-cost deposition techniques that can be performed over wide surfaces. Organic Thin-Film Transistors (OTFTs) are the fundamental unity in electronic circuits and, usually, display the metal insulator semiconductor field-effect transistor (MISFET) structure. OTFTs can be processed over cheap plastic substrates and integrate a high number of applications as: flexible displays, radio frequency identification tags, textile electronics and sensors (e.g. chemical and biological compounds). Nowadays, consumers demand portable and low-cost electronic devices, mainly as sensors for in-situ medical and veterinarian diagnosis. The most widely used OTFT structure in sensing is the bottom-gate/bottom-contact FET over highly-doped silicon substrates and inorganic dielectrics. Polymers as poly(3-hexylthiophene) (P3HT) have found increasing acceptance by the scientific community, attesting their potential as semiconductors for commercial applications. In this context, the thesis lies in the development of organic transistors based in P3HT polymer for the detection of vapor-phase compounds. This study begins with transistor performance optimization through changes in dielectric and semiconductor processing. Thin-film thickness and P3HT cast solution drying time are the main studied parameters. It involves also the understanding of device performance degradation when exposed to atmosphere and under bias stress, before finally mapping sensitivity and specificity against gaseous analytes. P3HT-based sensors are potentially interesting for ammonia, ketones and organochlorides detection. Other polymeric semiconductors may be necessary to increase specificity against water steam and alcohol analytes.

As células eletroquímicas emissoras de luz (PLECs) pertencem a um novo ramo importante na optoeletrônica orgânica devido ao seu grande potencial para ser usado como ponto - pixels para telas coloridas e também para painéis de iluminação. Diferentemente de diodos orgânicos emissores de luz (OLEDs), a tecnologia de OLECs ainda está em estágios iniciais de desenvolvimento, em comparação com a tecnologia de OLED , OLECs tem a vantagem de ser operado em ambas as polaridades de tensão ( para a frente ou de polarização reversa ), e, além disso, o seu desempenho é menos dependente dos materiais do eletrodos e a espessura da camada ativa do dispositivo. A camada ativa de um OLEC compreende uma mistura de um polímero eletroluminescente conjugado e um eletrólito de polímero. Consequentemente, o transporte elétrico durante a operação do dispositivo envolve uma combinação de dinâmica iônica e eletrônica e efeitos intrincados nas interfaces com os eletrodos. A literatura apresenta até agora duas abordagens diferentes para descrever o fenômeno de transporte nas OLECs. O modelo de eletrodinâmica, que combina separação iônica com o processo de difusão limitada eletrônica, e o modelo de dopagem eletroquímico que considera uma dopagem eletroquímica do polímero conjugado, dando a formação de uma junção p-i-n na camada ativa. Usando as medidas de decaimento da corrente sobre uma voltagem aplicada e espectroscopia de impedância /admissão , investigamos o transporte de portadores de carga em um OLEC tendo como camada ativa uma mistura de poli [ ( 9, 9 - dioctyl - 2, 7 - divinileno - fluorenileno ) - alt - co - { 2 - metoxi -5 - ( 2 - etil- hexiloxi ) -1,4 - fenileno } ] ( PFGE ) , com poli ( óxido de etileno ) ( PEO ) complexado com triflato de lítio ( TriLi ) , na proporção 01:01 : X , onde X foi de 0,10 , 0,05 , 0,01 , 0,00. Foram obtidos dados importantes relacionados com efeito iônico e eletrônico durante a operação deste PLEC, sendo que as medidas de transiente e de impedância mostraram que o movimento iônico auxilia o processo de injeção eletrônica. Outro fato relevante é que o desempenho da PLEC é dependente da formação da dupla camada iônica que tem sua espessura abaixo de 10 nm e que o processo de sua formação depende altamente da condução iônica, que por sua vez vai depender da quantidade de íons e de sua mobilidade, sendo influenciando por fatores como concentração de sal e temperatura do dispositivo. As medidas realizadas mostram que as PLECs com 2,5 e 5% de concentração de sal apresentam o melhor desempenho. Organic Light-emitting Electrochemical Devices (OLECs) belong to a new important branch in organic optoelectronics due to their great potential to be used as dot-pixels for color displays and also to lighting panels. Differently from organic light-emitting diodes (OLEDs), the technology of OLECs is still in early stages of development. In comparison to OLED technology, OLECs have the advantage in being operated in both voltage polarities (forward or reverse bias), and, in addition, their performance is less dependent on the electrode materials and the device thickness. The active layer of an OLEC comprises a mixture of a conjugated electroluminescent polymer and a polymer electrolyte. Consequently, the electrical transport during the device operation involves a combination of ionic and electronic dynamics and intricate effects at the interfaces with the electrodes. The literature presents so far two different approaches to describe the transport phenomenon in the OLECs. The electrodynamic model, which combines ionic charge separation with electronic diffusionlimited process, and the electrochemical doping model that consider an electrochemical doping of the conjugated polymer, giving and the formation of a p-i-n junction in the active layer. Using current decay under an applied voltage measurements and impedance/admittance spectroscopy, we investigate charge carrier transport in an OLEC having as active layer a mixture of poly [(9, 9 - dioctyl - 2, 7 - divinileno - fluorenileno) - alt - co - {2 - methoxy -5 - (2 - ethyl-hexyloxy) -1,4 - phenylene}] (PFGE), with poly (ethylene oxide) (PEO) complexed with lithium triflate (TriLi), in the proportion 1:1:X, where X was 0.10, 0.05, 0.01, 0.00. We have obtained important results related to ionic and electronic effect during this operation PLEC. This measurements of transient current and impedance showed that ionic movement aids the process of electron injection. Another relevant fact is that the performance of PLEC is dependent on the formation of ionic double layer having thickness below 10 nm. The formation of this double layers is highly dependent on the ionic conduction, which in turn will depend on the amount of ions. The ionic mobility is influenced by factors such as salt concentration and temperature of the device. The measurements show that PLECS with 2.5 and 5% salt concentration had the best perform.

Neste trabalho, foram realizados estudos de propriedades elétricas e de eletroluminescência em diodos emissores de luz (OLED) contendo modulação energética de poços de potencial para elétrons e buracos (tipo I), poços esses posicionados na região central da camada ativa. A camada ativa é composta por poços simples e duplos, de espessura de 5 e 10nm, de Poli (fenilenovinileno), PPV (Eg = 2,4 eV), dispostos entre duas barreiras de Polifluoreno ou PFO (Eg = 3,0 eV) de espessura 40 nm. Os filmes de PFO foram obtidos a partir de uma solução em Clorofórmio via spin coating e os de PPV a partir de um precursor solúvel em agua via spin assistant LbL, técnica essa que permitiu o crescimento alternado de filmes de PFO e filmes extremamente finos de PPV mesmo em vista da ortogonalidade de seus solventes. Camadas injetoras de polieletrólitos foram depositadas adjacentes ao catodo para diferenciar injeção eletrônica da injeção de buracos. Foram feitos dispositivos contendo somente uma camada de PFO de 80 nm, chamados referência, para comparação do efeito dos poços nos dispositivos com um e dois poços de potencial. Na caracterização foram utilizadas as técnicas de microscopia confocal, com o intuito de demonstrar o crescimento efetivo das camadas, e medidas elétricas de corrente (IxV) e eletroluminescência (LxV) por voltagem. Medidas do perfil de intensidade ao longo do filmes e espectros de fotoluminescência em três regiões distintas da área total do dispositivo mostraram que as camadas de PPV de aproximadamente 5 e 10 nm estavam homogêneas e que recobriam bem as camadas de PFO. Os espectros de eletroluminescência dos dispositivos mostraram que as diferenças energéticas entre os orbitais π (ΔEHOMO= 0,54 eV) e π* (ΔELUMO = 0,37 eV) do PFO e PPV foram suficientes para causar o aprisionamento e recombinação dos portadores dentro do poço, resultando em emissões características do PPV com picos bem definidos próximos a 520 nm, bastante distintas das emissões dos dispositivos referência, contendo somente PFO (banda larga e não definida de emissão com λ > 480 nm). A presença dos poços de potencial alterou significativamente as propriedades dos dispositivos levando a diminuição da voltagem de acendimento (Von) para 3,5 V mesmo para dispositivos contendo camada injetora que dificultava a injeção eletrônica. Quando há apenas um poço de potencial na camada ativa dos dispositivos, com ou sem camada injetora, o regime de corrente para voltagens abaixo de 3,5 V é ôhmico e unipolar, sendo ditado por buracos, mas quando a voltagem é maior do que 3,5 V o regime de corrente fica limitado pelo portador minoritário, o elétron. Surpreendentemente, quando são colocados dois poços na camada ativa, separando os portadores, tanto corrente como a formação excitônica e consequente recombinação, ficam sujeitas a um processo de tunelamento do portador majoritário, o buraco. In this work, studies of electrical properties and electroluminescence in organic light emitting diodes (OLED) containing energetic modulation of potential wells for charge carriers (type I), positioned in the central region of active layer. The active layer is composed of single and double wells of Poly (phenylenevinylene), PPV (2.4 eV), arranged between two barriers of polyfluorene, PFO (3.0 eV), with 40 nm thickness. The PFO films were obtained from a chloroform solution by spin coating and PPV from a water soluble precursor via spin assistant LbL technique, a technique that has allowed the alternate growth of PFO films and extremely thin PPV films from a orthogonal solvent to chloroform, water. Injection layers of polyelectrolytes were deposited adjacent to the cathode to differentiate electronic injection from hole injection. Confocal microscopy measurements showed that the PPV layer of 5 to 10nm thickness were homogeneous and covered PFO layers entirely. Electroluminescence measurements of the devices showed that the energetic difference between π (ΔEHOMO = 0.54 eV) and π* (ΔELUMO = 0.37 eV) orbitals from PFO and PPV were enough to cause the charge carriers efficient trapping and recombination in the well, resulting in PPV characteristic emission peaks near to 520 nm, quite different from the reference device emission containing only PFO (broad emission band in the lower energy range). The current measurements showed that the presence of potential wells in the middle of the active layer is responsible for effective change in electrical properties of devices such as carrier density n, μ the mobility and conductivity. When there is only one potential well in the active layer, with or without injection layer, the current regime for voltages below 3.5 V is ohmic and unipolar, being dictated by holes, but when the voltage is greater than 3.5 V current regime is limited by the minority carrier, the electron. Surprisingly, when two wells are placed in the active layer, separating the carriers, both current as the excitonic formation and subsequent recombination are subject to a tunneling process by the majority carrier, the hole.

Erros de alinhamento em sistemas ópticos não criam novas aberrações, mas alteram a dependência com o campo das aberrações já conhecidas. Neste trabalho, a sensibilidade teórica ao alinhamento, de sistemas ópticos reflexivos compostos por dois elementos, foi avaliada em função das constantes cônicas dos espelhos. Dentre as diferentes configurações consideradas nesta análise, uma específica apresenta menor sensibilidade à descentralização do espelho secundário. A utilização da teoria de aberração de onda aplicável a sistemas plano-simétricos revelou que a escolha apropriada da constante cônica do espelho secundário faz com que coma uniforme de terceira ordem seja compensado quando esse elemento encontra-se descentralizado, fazendo com que esse sistema seja livre da aberração mais importante causada a ele por desalinhamentos, tornando-o menos sensível. Este trabalho apresenta uma metodologia de alinhamento baseada na análise da frente de onda transmitida por sistemas ópticos, que utiliza redes neurais artificiais para a estimativa dos erros de alinhamento. A frente de onda transmitida por um sistema óptico carrega informações das aberrações desse sistema, que podem ser descritas em termos dos polinômios de Zernike. Esses polinômios podem ser usados para a análise dos efeitos de erros de alinhamento nas aberrações do sistema. Redes neurais artificiais são empregadas na análise dos coeficientes dos polinômios de Zernike visando avaliar o tipo de desalinhamento e a sua magnitude. As estimativas teóricas dos desalinhamentos tanto em sistemas reflexivos como em sistemas refrativos são satisfatórias quando o sistema é considerado perfeito, ou seja, as superfícies ópticas de seus elementos não apresentam erros de forma e não há ruído nos dados avaliados. Na presença de defeitos de fabricação ocorre degradação no desempenho do estimador. Além de descentralização e inclinação, redes neurais artificiais são capazes de fornecer uma estimativa de erros de posicionamento axial dos elementos do sistema. Com base nos estudos realizados, acredita-se que redes neurais artificiais constituem uma alternativa promissora no alinhamento de sistemas ópticos complexos. Although misalignments in optical systems do not generate new aberration forms, they change the field-dependence of the known ones. In this research, the sensitivity of two-mirror optical systems due to misalignments is evaluated in function of the conic constants of the mirrors. Among the different configurations considered in this study, a specific one has shown low sensitivity due to decenter misalignments. The application of the wave aberration theory for plane-symmetric optical systems has revealed that the proper choice of the secondary mirror conic constant allows third-order uniform coma to be compensated, leading to a less sensitive system, free from the most important misalignment-induced aberration. This thesis also presents an alignment methodology based on the analysis of the transmitted wavefront utilizing artificial neural networks to estimate alignment errors in the components of the system. The transmitted wavefront carries information about the aberrations in the optical system, which can be described in terms of Zernike polynomials. Such polynomials are used for the analysis of the effects of misalignments on the aberrations of the system. Artificial neural networks are employed in the analysis of the coefficients of Zernike polynomials and used to evaluate both type and magnitude of the misalignments. Theoretical misalignments estimated in reflexive and refractive optical systems are satisfactory for perfect systems, i.e., systems with no surface errors, and noiseless data. When surface imperfections are considered, the performance of the estimator is reduced. Besides decenter and tilt misalignments, artificial neural networks can estimate axial positioning errors of the elements in the system, therefore they are believed to be a promising alternative for the alignment of complex optical systems.