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Mesoporous thin films (MTFs) displaying high surface area and controlled porosity constitute interesting materials for a plethora of applications in optics and electronics. A critical aspect in MTF processing is template removal that usually consists in thermal treatment at 350 °C, which consolidates the oxide film but might change the pore features. In addition, the use of such high temperature must be avoided when organic functionalities are to be preserved, or in the case of film deposition on polymeric substrates. Here we present and compare five different methods to consolidate silica MTF (SMTF) in mild conditions, at a maximum processing temperature of 130 °C. Conditions, such as duration of the thermal treatment, vacuum conditions, exposure to acidic and alkaline media, were systematically explored and the resulting films were analyzed by optical microscopy, focused ion beam, scanning electron microscopy, ellipsometry, and infrared spectroscopy. The optimized conditions leading to accessible mesopores and a stable oxide structure that can be used as a mesoporous perm-selective electrode are discussed.

Antibodies are the most used technological tool in histochemistry. However, even with monoclonal antibodies, their standardization is difficult due to variation of biological systems as well as to variability due to the affinity and amplification of the signal arising from secondary peroxidase detection systems. In this article we combined two synthetic molecules to facilitate the standardization of a detection protocol of protein markers in histological sections. The first molecule was an aptamer, a 50-base single-stranded DNA fragment, which recognizes a PTEN tumor suppressor. The second molecule used was also another single stranded 18-base aptamer DNA fragment, which forms a quadruplex structure guanine box. This G-quadruplex recognizes and attaches a molecule of hemin, increasing the catalytic capacity for the hydrogen peroxide. Our results show how the correct structural design of DNA combining an aptamer together with the peroxidase-like DNAzyme allows to detect proteins in histological sections. This tool offers the standardization of the detection of prognostic markers in cancer, in quality and quantity, due to its synthetic nature and its 1:1 antigen:enzyme ratio. This is the first time that reproducible results have been presented in histological sections staining a cancer marker using a single-stranded DNA molecule with dual function.

The combination of different nanomaterials through step-by-step synthesis procedures has turned into a promising alternative to fabricate high-quality nanosystems in order to satisfy the increasingly demanding requirements of the biomedical field. In this work, we report a detailed study on the synthesis and characterization of a complex nanosystem composed of nanoparticles with a single magnetic nanoparticle core and a shell of dense and mesoporous silica arranged in layers. The procedure designed to fabricate these systems lead us to the formation of a dispersion of non-agglomerated spherical nanoparticles of nearly 100 nm. The structural characterization performed over the final samples confirmed both the prevalence of single-core systems and the presence of the mesoporous silica shell in the outer layer. The performance of the nanosystem in a specific technological application was tested by sequentially loading two different fluorescents molecules by covalent and non-covalent bonding strategies. Due to the distinct loading strategies, the resulting nanosystem presented a magnetically-assisted probe & release functionality as analyzed in a magnetophoretic experiment.

Chemical and physical methods have been generally used for modifying the surface of titanium implants with the aim of achieving better osseointegration. In this work, an evaluation of the effect of different chemicals and thermochemical treatments on the surface modification of titanium was carried out. Plates of commercially pure titanium were polished and treated with four different methods. Scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, X-ray diffraction and drop shape analysis were used to characterize the modified titanium surface. Our results showed that the AEPTTT surface exhibited the highest Ra values followed by AEAT, AEPT, polished Ti and AE samples. In addition, the AEAT and AEPTTT treatments developed the largest surface area, while the AE treatment produced the lowest surface area. Furthermore, the AEAT treatment created the most hydrophilic surface, which is known to positively affect the osseointegration rate of dental implants. Keywords: Titanium, surface modification, hydrogen peroxide treatment, alkali treatment, thermochemical treatment.

Mesoporous oxide thin films (MOTF) present very high surface areas and highly controlled monodisperse pores in the nanometer range. These features spurred their possible applications in separation membranes and permselective electrodes. However, their performance in real applications is limited by their reactivity. Here, we perform a basic study of the stability of MOTF toward dissolution in aqueous media using a variety of characterization techniques. In particular, we focus in their stability behavior under the influence of ionic strength, adsorption of electrochemical probes, and applied electrode potential. Mesoporous silica thin films present a limited chemical stability after electrochemical cycling, particularly under high ionic strength, due to their high specific surface area and the interactions between the electrochemical probes and the surface. In contrast, TiO₂ or Si0.9Zr0.1O₂ matrices present higher stability; thus, they are an adequate alternative to produce accessible, sensitive, and robust permselective electrodes or membranes that perform under a wide variety of conditions., Facultad de Ciencias Exactas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas

Enzyme inks can be inkjet printed to fabricate enzymatic biosensors. However, inks containing enzymes present a low shelf life because enzymes in suspension rapidly lose their catalytic activity. Other major problems of printing these inks are the non-specific adsorption of enzymes onto the chamber walls and stability loss during printing as a result of thermal and/or mechanical stress. It is well known that the catalytic activity can be preserved for significantly longer periods of time and to harsher operational conditions when enzymes are immobilized onto adequate surfaces. Therefore, in this work, horseradish peroxidase was covalently immobilized onto silica nanoparticles. Then, the nanoparticles were mixed into an aqueous ink containing single walled carbon nanotubes. Electrodes printed with this specially formulated ink were characterized, and enzyme electrodes were printed. To test the performance of the enzyme electrodes, a complete amperometric hydrogen peroxide biosensor was fabricated by inkjet printing. The electrochemical response of the printed electrodes was evaluated by cyclic voltammetry in solutions containing redox species, such as hexacyanoferrate (III/II) ions or hydroquinone. The response of the enzyme electrodes was studied for the amperometric determination of hydrogen peroxide. Three months after the ink preparation, the printed enzyme electrodes were found to still exhibit similar sensitivity, demonstrating that catalytic activity is preserved in the proposed ink. Thus, enzyme electrodes can be successfully printed employing highly stable formulation using nanoparticles as carriers. Fil: Mass, Mijal. Instituto Nacional de Tecnología Industrial. INTI-Micro y Nanotecnologías; Argentina Fil: Veiga, Lionel S. Instituto Nacional de Tecnología Industrial. INTI-Micro y Nanotecnologías; Argentina Fil: Garate, Octavio. Instituto Nacional de Tecnología Industrial. INTI-Micro y Nanotecnologías; Argentina Fil: Longinotti, Gloria. Instituto Nacional de Tecnología Industrial. INTI-Micro y Nanotecnologías; Argentina Fil: Moya, Ana. Consejo Superior de Investigaciones Científicas. Centro Nacional de Microelectrónica. Institut de Microelectrònica de Barcelona; España Fil: Ramón, Eloi. Consejo Superior de Investigaciones Científicas. Centro Nacional de Microelectrónica. Institut de Microelectrònica de Barcelona; España Fil: Villa, Rosa. Consejo Superior de Investigaciones Científicas. Centro Nacional de Microelectrónica. Institut de Microelectrònica de Barcelona; España Fil: Ybarra, Gabriel. Instituto Nacional de Tecnología Industrial. INTI-Micro y Nanotecnologías; Argentina Fil: Gabriel, Gemma. Consejo Superior de Investigaciones Científicas. Centro Nacional de Microelectrónica. Institut de Microelectrònica de Barcelona; España

Access to appropriate diagnostic tools is an essential component in theevaluation and improvement of global health. Additionally, timely detection ofinfectious agents is critical in early diagnosis and treatment of infectiousdiseases. Conventional pathogen detection methods such as culturing, enzymelinked immunosorbent assay (ELISA) or polymerase chain reaction (PCR) requirelong assay times, and complex and expensive instruments making them not adaptableto point-of-care (PoC) needs at resource-constrained places and primary caresettings. Therefore, there is an unmet need to develop portable, simple, rapid,and accurate methods for PoC detection of infections. Here, we present thedevelopment and validation of a portable, robust and inexpensive electrochemical magnetic microbeads-based biosensor (EMBIA) platform for PoC serodiagnosis ofinfectious diseases caused by different types of microorganisms (parasiticprotozoa, bacteria and viruses). We demonstrate the potential use of the EMBIAplatform for in situ diagnosis of human (Chagas disease and human brucellosis)and animal (bovine brucellosis and foot-and-mouth disease) infections clearlydifferentiating infected from non-infected individuals or animals. For Chagasdisease, a more extensive validation of the test was performed showing that theEMBIA platform displayed an excellent diagnostic performance almostindistinguishable, in terms of specificity and sensitivity, from a fluorescentimmunomagnetic assay and the conventional ELISA using the same combination ofantigens. This platform technology could potentially be applicable to diagnoseother infectious and non-infectious diseases as well as detection and/orquantification of biomarkers at the POC and primary care settings. Fil: Cortina, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Melli, Luciano Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Roberti, Mariano. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Mass, Mijal Inés. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Longinotti, Gloria. Instituto Nacional de Tecnología Industrial. Procesos Superficiales; Argentina Fil: Tropea, Salvador. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Lloret, Paulina. Instituto Nacional de Tecnología Industrial. Procesos Superficiales; Argentina Fil: Rey Serantes, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Salomón, Francisco. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Lloret, Matías. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Caillava, Ana Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Restuccia, Sabrina. Instituto Nacional de Tecnología Industrial; Argentina Fil: Altcheh, Jaime Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; Argentina Fil: Buscaglia, Carlos Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Malatto, Laura. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Ugalde, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Fraigi, Liliana. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Moina, Carlos. Instituto Nacional de Tecnología Industrial. Procesos Superficiales; Argentina Fil: Ybarra, Gabriel Omar. Instituto Nacional de Tecnología Industrial. Procesos Superficiales; Argentina Fil: Ciocchini, Andres Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina Fil: Comerci, Diego José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin) | Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnológicas. Instituto de Invest. Biotec. (subsede San Martin); Argentina. Comisión Nacional de Energía Atómica; Argentina

A simplified, surfactant-free method is presented for the synthesis of cuprous oxide mesoparticles involving the use of only three reactants at room temperature. Different morphologies, such as cubes, cuboctahedra, truncated octahedra, octahedra, hexapods, and porous spheres could be obtained using different concentrations of reactants. The roles played by each reactant in the synthesis are critically discussed. The mesoparticles were used in the formulation of carbon nanotube-based waterborne inks to prepare coated electrodes. The electrocatalytic activity of the different cuprous oxide mesoparticles used in the inks towards hydrogen peroxide reduction was measured and compared. Cuprous oxide hexapods yielded the highest sensitivity whereas porous spheres were superior in terms of stability. The combination of carbon nanotubes and cuprous oxide mesoparticles in waterborne ink allows printing of electrodes combining electrical conduction and electrocatalysis in a single layer printed onto flexible substrates. Fil: Veiga, Lionel S.. Instituto Nacional de Tecnología Industrial; Argentina Fil: Garate, Octavio. Instituto Nacional de Tecnología Industrial; Argentina Fil: Tancredi, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Industrial; Argentina Fil: Monsalve, Leandro Nicolas. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Ybarra, Gabriel. Instituto Nacional de Tecnología Industrial; Argentina

Conductive inks with optimal properties for amperometric sensor fabrication are key materials for low cost and high performance electrodes printed on flexible substrates. In this work, electrodes made with a carbon nanotube (CNT) waterborne ink were prepared and characterized. The electrodes showed mechanical stability and electrocatalytic behavior. Moreover, they were used for the immobilization of horseradish peroxidase (HRP) and their performance as enzymatic biosensors was assessed. Oxygen plasma treatment was used to generate carboxylic functionalities for enzyme immobilization. Its effect on the electrodes was investigated in order to optimize their performance. These electrodes were fabricated with an ink that provides a potentially simple route for roll-to-roll biosensor printing. Fil: Garate, Octavio. Instituto Nacional de Tecnología Industrial; Argentina Fil: Veiga, Lionel. Instituto Nacional de Tecnología Industrial; Argentina Fil: Medrano, Anahí V.. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Longinotti, Gloria. Instituto Nacional de Tecnología Industrial; Argentina Fil: Ybarra, Gabriel. Instituto Nacional de Tecnología Industrial; Argentina Fil: Monsalve, Leandro Nicolas. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Plasma nitriding of austenitic stainless steel is of high technological importance due to its ability to improve the surface hardness, wear and corrosion resistance. Therefore, such process presents a significant potential as a treatment of materials for biomedical applications. The resulting properties obtained on the nitrided layer depend on the nitriding parameters used, such as temperature, gases partial pressures, process time, among others. In this work, austenitic stainless steel AISI 316L was nitrided in a DC plasma using two different N2-H2 atmospheres: 25% N2 and 20% N2. A detailed analysis of surface microstructure has been carried out and related to corrosion behaviour in two saline solutions. The results were compared with the 316L unnitrided (UN). The chemical composition of the nitrided layer was determined by GDOES. The phases present in the nitrided layer were analysed by X-ray diffraction (XRD) and the phases in the surface of nitrided layer were analysed by grazing incidence X-ray diffraction mode (GIXRD). The corrosion behaviour of the samples was studied by an electrochemical corrosion test in 3 wt% NaCl and Ringer's solutions. The GDOES (Glow Discharge Optical Emission Spectroscopy) analysis shows a higher N concentration of in the surface of 25% N2 samples, named HN. The phases observed, by GIXRD, in HN samples were expanded austenite γN, CrN, Fe3N and Fe4N and, in the 20% N2 samples, named LN, only peaks of expanded austenite and Fe4N were observed. The corrosion results showed that LN present better corrosion resistance than HN, this could be due to the absence of chromium nitrides in the surface of LN as a consequence of lower N percentage in the nitriding atmosphere. Fil: de Las Heras, Maria Evangelina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Ybarra, Gabriel Omar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Industrial; Argentina Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Cabo, Amado. IONAR S.A.; Argentina Fil: Dalibon, Eugenia Laura. Universidad Tecnológica Nacional; Argentina Fil: Brühl, Sonia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional; Argentina

Iron oxide nanoparticles were synthesized by the co-precipitation method and subjected to an adsorption and functionalization process at controlled pH with five different small carboxylate ligands, namely: citrate, tartrate, gluconate, succinate and β-alanine. The efficiency of the functionalization was evaluated by infrared spectroscopy and thermogravimetric measurements, finding that the presence of hydroxyl groups in the organic molecule is essential to achieve good levels of adhesion. In the three cases with higher levels of adhesion, the nanoparticles remain permanently stabilized and the system behaves like a ferrofluid at neutral pH. Colloidal properties such as the mean hydrodynamic diameter and the surface electrokinetic potential were studied over a wide pH range, being able to establish a clear correlation between the speciation equilibria of the adsorbed species, the surface charge and the formation of agglomerates between the particles. Finally, a magnetophoretic experiment was designed to evaluate and compare the mobility of the nanoparticles under a magnetic field gradient. In systems with individually stabilized nanoparticles, no magnetophoretic mobility was observed due to the low limit velocity reached by the particles. This result is consistent with a theoretical limit speed calculated considering the different parameters of the experiment and the ferrofluids. In systems with agglomerated nanoparticles it was found that the magnetophoretic mobility and the limit speed increase with the hydrodynamic diameter. In turn, this property varies strongly with the pH of the system according to the protonation / deprotonation equilibria of the surface of the nanoparticles and the formation or rupture of the agglomerates.

Magnetic Fe3O4@Au nanocomposite, nanostructured particles were prepared by depositing gold onto seeds of superparamagnetic iron oxide nanoparticles (SPION). The particles were characterized by SEM, TEM, XRD, visible and near infrared spectroscopy, and magnetic measurements. They were also functionalized and employed as enzymatic carriers for electrochemical biosensing. The nanostructured particles showed an urchin-like, roughly spherical morphology whose surface was covered with nanometric protuberances. The average diameter of the particles could be controlled in the 100–500 nm range by changing the concentration of surfactants (oleylamine and oleic acid) employed in the synthesis. XRD showed a preferential growth of {1 1 1} facets. 3-Mercaptopropionic acid was used to chemically modify the surface of the nanostructured particles and horseradish peroxidase was immobilized onto the gold surface. Attached enzymes showed good activity even after several cycles of magnetic collection, drying, and redispersion.

In cattle, cryopreservation of semen and sex-sorting kill up to 50% of spermatozoa and decrease the success of assisted insemination (AI). Therefore, significant efforts are being carried out to improve the quality of semen prior to AI. In this work we used the Cell-SELEX technique to select single strand DNA aptamers able to recognize with high affinity and specificity damaged sperm cells generated by heat- treatment. We first isolated aptamers with a conserved two motifs of 6 nucleotides of length that bind to the membrane of heat-treated spermatozoa. Then, we used synthetic biotin-labeled aptamers containing the conserved motif to recognize membrane-damaged cells and separate them from viable cells by the use of avidin-coated superparamagnetic iron oxide nanoparticles (SPION). This procedure improved the quality of semen by significantly increasing the percentage of healthy sperm cells without affecting the rate of blastocyst cleavage. This technique was successfully applied to both unsorted and sex-sorted sperm suspension. Fil: Farini, Veronica Lujan. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Camaño, Carla V.. Instituto Nacional de Tecnología Industrial; Argentina Fil: Ybarra, Gabriel Omar. Instituto Nacional de Tecnología Industrial; Argentina Fil: Viale, Diego Luis. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Vichera, Gabriel Damian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Yakisich, Juan Sebastian. Hampton University; Estados Unidos Fil: Radrizzani Helguera, Martin. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina

The protective performance of epoxy coatings on mild steel immersed in 3.5% NaCl solutions was evaluated by means of electrochemical noise analysis and electrochemical impedance spectroscopy (EIS). Current and voltage noise were recorded and the standard deviations of the potential, current and noise resistance were calculated. Additionally, the spectral noise resistance (RSN) was obtained from the harmonic analysis of the noise data. Finally, EIS measurements were carried out and the data fitted with an equivalent circuit from which the polarization resistance was obtained. Resistance parameters obtained by both techniques were found to be in good agreement. A set of parameters obtained from electrochemical noise measurement is proposed to be used for the assessment of the performance of protective coatings.

In this work, a study about the deposition of hydroxyapatite on a titanium substrate employing the biomimetic method is presented. A solution with high content of calcium and phosphorus (SCS) was used. In addition, activation of titanium with hydrogen peroxide and hydrochloric acid and a subsequent heat treatment was performed. The characterization of materials used and the coating obtained was carried out by Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). As a result of the activation processes a hydrated titanium oxide was formed. On the active surface, a coating of hydroxyapatite was obtained after a period of 24 h, which has a thickness of about 2-4 μm.En el presente trabajo se realizó un estudio de la deposición de hidroxiapatita sobre un sustrato de titanio mediante el método biomimético. Para ello se empleó una disolución con elevado contenido de calcio y fósforo (SCS). Además, se realizó la activación del titanio a partir de la aplicación de procesos de oxidación con peróxido de hidrógeno y ácido clorhídrico con un posterior tratamiento térmico. La caracterización de los materiales empleados, así como de los recubrimientos obtenidos, se realizó mediante Espectroscopia Infrarroja (FT-IR), Difracción de Rayos X (DRX), Microscopia Electrónica de Barrido (MEB) y Espectroscopia de Energía Dispersiva de Rayos X (EDX). Como resultado del proceso de activación se formó un óxido de titanio hidratado. Sobre la superficie activada se logró obtener un recubrimiento de hidroxiapatita en un período de 24 h, caracterizado por su elevada densidad y cristalinidad y por presentar un espesor entre 2-4 μm.

A method of synthesis is presented for the rapid preparation of copper, copper oxide and mixed copper oxide-copper nanoparticles employing a conventional home microwave oven. The nanoparticles were characterized by SEM, XRD and UV-visible spectroscopy. The size and the composition of the nanoparticles were controlled by the heating time. Cuprous oxide nanoparticles were obtained at short heating times and copper nanoparticles at longer times, while mixed cuprous oxide-copper nanoparticles where obtained in an in between window of time.

In the present work, a study of the photoelectrochemical characteristics and chemical structure of anodic films formed onto different Sn1-xIn x (0 ≤ x < 0.3) alloys in 0.2 M NaOH is presented. The electrochemical behavior of the alloys was studied by means of cyclic voltammetry. The optical band gaps of the passive films were determined by photocurrent spectroscopy, while its chemical structure was studied by Fourier transform infrared reflection-absorption spectroscopy. The experimental results indicate that the anodic films consist of hydroxylated species of the type In ySn(1-y)(OH)4-y. The films are enriched in In and, for x > 0.25, In(OH)3 is the dominant component of the surface layers. The existing theoretical background was used to estimate the relative concentration of Sn and In in the films from the band gap measurements.

The oxidation–reduction of the Ferri/Ferrocyanide couple in solution onto modified glassy carbon Rotating Disk Electrodes (RDE) covered by Os(II) bipyridile poly-vinylpyridile (OsBPP) polymer was studied at room temperature. Steady state polarization curves were carried out as a function of the rotation speed, the polymer thickness and the concentration of redox centers within the polymer. This system has the characteristic that the formal redox potentials of both the external redox couple (E0′(Fe(CN)63−/4−) = + 0.225 V vs. SCE) and the mediator polymer (E0′(OsBPP) = 0.260 V vs. SCE) lie very close. It is demonstrated that diffusion of the Ferri/Ferrocyanide inside the polymer can be ruled out. Since the processes of charge transfer at the metal/polymer and the mediating reaction are fast, the experimental results can be interpreted in terms of a kinetics in which the charge transport in the polymer or the diffusion in the solution may be the rate determining step, according to the experimental conditions. A simple model is considered that allows interpreting the experimental results quantitatively. Application of this model allows the determination of the diffusion coefficient of the electrons within the film, De ≈ 10−10 cm2 s−1.

In this work we briefly review the theoretical basis for the electrochemical rectification in mediated redox reactions at redox polymer modified electrodes. Electrochemical rectification may have two distinct origins. It is either caused by a slow kinetics of the reaction between the external redox couple and the mediator or it is originated by a slow electronic transport within the film under an unfavorable thermodynamic condition. We show experimental results for the redox mediation reaction of poly(o-aminophenol) (POAP) on the Fe2+/3+ and on the Fe(CN)63−/4− redox couples in solution that prove the proposed mechanisms of electrochemical rectification.

In this work, we analyze the i–E response of a redox mediator modified electrode in steady state and in the absence of permeation of the reactants into the film. We show that, besides some kinetic criteria existing in the literature based on the behavior of the limiting currents, there are others based on the entire i–E response. This analysis allows to explain several features of the i–E curve, yet unexplained, such as the shift of the half wave potential, electrochemical rectification, the shape of the Koutecky–Levich plots and the shape of the E vs. ln [(iL − i)/i] plots. From them, it is possible to determine, almost unmistakably, the type of kinetic control and to obtain the corresponding kinetic parameters.

Austenitic stainless steel are used in industrial applications, mainly due to their good corrosion resistance; however, their low hardness and poor wear performance impose strong limitations in many cases. In this work, the wear behavior of the unnitrided and DC-pulsed plasma nitrided AISI 316L stainless steel has been investigated using an Amsler-Disc-Machine under rolling–sliding contact conditions. The microstructure was studied by X-ray diffraction and the worn surface, subsurface, and wear debris were analyzed by optical microscopy, scanning electron microscopy, and microhardness testing. The obtained results show that pulsed plasma nitriding improves the wear resistance of the AISI 316L and different wear mechanisms were observed depending on the normal applied load.

Composite magnetite–gold mesoscopic particles were prepared by deposition of Au onto magnetite nanoparticles. The surface morphology of the mesoparticles could be tuned by controlling the factors that affect the kinetics of the reactions and by adding surfactants that direct the growth of gold crystals. The internal structure of composite mesoparticles was analyzed by focused ion beam and scanning electron microscopy. A particle-mediated growth mechanism of formation was proposed. Fil: Lloret, Paulina. Instituto Nacional de Tecnologia Industrial. Procesos Superficiales; Argentina Fil: Ybarra, Gabriel. Instituto Nacional de Tecnologia Industrial. Procesos Superficiales; Argentina Fil: Granell, Pablo. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; Argentina Fil: Socolovsky, Leandro Martin. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Moina, Carlos. Instituto Nacional de Tecnologia Industrial. Procesos Superficiales; Argentina

In the present work, industrial-scale DC-pulsed plasma nitriding for 20 h at 673 K was used to improve the wear resistance of an AISI 410 martensitic stainless steel. The tribological behaviour was studied and compared to the behaviour of the same steel in as-received condition. Pin-on-disc dry tests, using an alumina ball as counter-body, were carried out to determine the evolution of the friction coefficient. The wear resistance was investigated using an Amsler-disc-machine, employing a dry combined contact of rolling–sliding with three different applied loads. The wear mechanisms involved during rolling–sliding of unnitrided and plasma nitrided steels were investigated by microscopic observation of the surfaces, the corresponding cross-sections and the produced wear debris. The combination of different wear mechanisms taking place in the wear process of unnitrided and nitrided materials were discussed and analyzed. In contrast to the unnitrided steel, DC-pulsed plasma nitrided samples presented an improvement in the friction coefficient and the wear rate.

The influence of DC-pulsed plasma nitriding time on the surface properties of AISI 4140 low-alloy steel has been investigated. The samples were nitrided in an industrial equipment using a gas mixture consisting of 25% N2+75% H2 and the DC-pulsed glow discharge time was varied between 1 and 28 h. Optical and scanning electron microscopy as well as X-ray diffraction, electron probe microanalysis and microhardness measurements have been used to study the ion-nitrided surfaces. It was found that the compound layer thickness does not follow a parabolic law with treatment time. An equation has been derived according to the experimental data that can predict the thickness under the nitriding conditions studied in the present investigation. Furthermore, when the nitriding time is increased, the compound layer passes from a dual phase (e-Fe2–3N+gV-Fe4N) to a monophase gV-Fe4N. The topographical evolution and roughness, studied by atomic force microscopy (AFM), have shown that all the roughness parameters increase with the ion nitriding time. The rate of increase is higher during the first hours of nitriding, which could be related to the relative intensity of sputtering and redeposition. The microformations developed during nitriding show a conical aspect with different morphologies. Their growth direction changes from a perpendicular orientation in the center of the sample to an inclination close to the sample edge, as a consequence of the change of the direction of the electric field lines close to the edges. D 2005 Elsevier B.V. All rights reserved.

The goal of this paper is to present a method to determine the time evolution of epoxy conversion for epoxy/amine and epoxy/amide formulations in heterogeneous systems such as paints by means of near infrared (NIR) spectroscopy. The cure reaction involves a simple addition mechanism between the oxirane ring and the amine/amide hydrogen functional groups. The extent of the reaction was calculated from the NIR absorption band at around 4530 cm −1 which depends on the oxirane rings concentration. The NIR spectroscopic method, which has the advantage of real time analysis over other techniques such as chemical titration, can be employed with most of the usual, modern FTIR spectrometers.

In this work, we studied the changes in volume of an electroactive polymer as [Os(bipy) 2 (PVP) 10 Cl] 2+ . The dependence of the polymer volume on the solution pH and applied potential was measured. The morphology of [Os(bipy) 2 (PVP) 10 Cl] 2+ , deposited onto monocrystalline Si substrates, both by drop coating and by spin coating was studied by AFM. Drop-coated films show a globular structure on top of a thin and homogeneous film while spin-coated films are even and homogeneous. The volume changes with the pH of the external solution were measured following the changes in the globules size of drop-coated films. Also, the thickness dependence of spin-coated films on pH was measured by AFM. Both the size of the globules and the thickness of the films increase as the pH of the external solution decreases. The possible reasons for this increase are discussed. The volume change following the oxidation of a drop-coated polymer was estimated from the projected area obtained by optical microscopy with image capture. The images show an increase in the projected area as the film is progressively oxidized. The possible reasons for this increase in volume are discussed.

AISI 410 martensitic stainless steel samples with different metallurgical structures were DC-pulsed plasma nitrided at 623, 723 and 773 K. The samples were ion nitrided in an industrial equipment using a gas mixture consisting of 25% N2+75% H2 under a pulsed DC glow discharge. Optical and scanning electron microscopy, as well as glancing angle X-ray diffraction and microhardness measurements have been used to study the ion nitrided surfaces. All plasma nitrided samples showed surface hardness values higher than 1000 HV; the highest value was obtained at 673 K. The case depth was approximately 30 Am for samples nitrided at 673 and 773 K, while the sample nitrided at 623 K showed an 'expanded ferrite' phase (aN) and an incipient precipitation of Fe4N. Depending on the treatment temperature and time, two fronts were formed, termed diffusion front and transformation front; the latter produces a softening of the nitrided case. Electrochemical measurements showed a decrease of corrosion resistance in the samples nitrided during 20 h at 673 and 773 K. Conversely, the sample nitrided at 623 K presented a low corrosion current and more noble corrosion potential.

—In this work, we present the development of apoint-of-care platform for the serologic diagnosis of infectiousdiseases. The complete system consists of magnetic particles withimmobilized antigens, disposable electrochemical cells, hardwareand software. The main purpose of this paper is to present thelast two components. The platform is powered by a rechargeablebattery and can be controlled using mobile devices, allowingpoint-of-care diagnosis of diseases. The platform was successfullytested for the diagnosis of foot-and-mouth disease, human andbovine brucellosis, and Chagas disease.Keywords—Point-Of-Care Diagnosis; Electrochemical Biosen-sor; Portable platform; Android app I. I NTRODUCTION Biosensors are compact analytical devices which employa biological element in order to detect a specific substance,i.e. the analyte. After the analyte has been detected by thebiological recognition element, a signal of some sort is pro-duced which is then converted into an electrical signal witha transducer. In the case of electrochemical biosensors, thechemical signal generated by the interaction between the bio-logical recognition element and the analyte is then convertedinto an electrical current via an electrochemical reaction at anelectrode surface [1]. A particular case is the amperometricbiosensors, where the electrochemical measurement is carriedout by a potentiostat, which is an instrument that applies avoltage to a working electrode with respect to a reference elec-trode and measures the current flowing through that workingelectrode.Voltage is controlledby usingan auxiliaryor counterelectrode.Biosensors aimed for the detection of the presence ofspecific antibodies or antigens are particularly important forthe diagnosis of diseases in remote environments, wherecarrying out immunoassays such as ELISA (Enzyme-LinkedImmunosorbent Assay) is not an option. In addition to thepossibility to carry out diagnosis with minimum training andequipment, point-of-care devices have additional advantages.For instance, fast, non-expensive and multiple assays can beperformed with point-of-care portable devices, which can beof help in the occurrence of an epidemic spread.This article presents the development of a compact andwireless amperometric biosensors platform, with support forAndroid and other operating systems that allows to diagnoseinfectious diseases as foot-and-mouth disease, human andbovine brucellosis, and Chagas disease. Emphasis is placed onthe development of the hardware and its associated software,mentioning also the detection principle and other system com-ponents. Results obtained for those diagnosis are presented.II. D

En este trabajo intentamos avanzar en el conocimiento del proceso de pintado de las cuevas con arte rupestre de la Sierra de Ancasti (Provincia de Catamarca, Argentina) a partir del análisis químico de las mezclas pigmentarias con las que fueron realizadas las pinturas. De este modo, planteamos la posibilidad de comprender algunos de estos abrigos pintados como «obras abiertas», es decir, como el resultado del agregado de motivos a lo largo de un proceso cuya duración, quizás larga, aún no conocemos. In this paper we attempt to advance the understanding of the process of painting in caves with rock art at Ancasti’s Highlands (Catamarca Province, Argentina) from chemical analysis of pigment mixtures with which the paintings have been made. Thus, we suggest the possibility of understanding some of the art in these caves as «open works», i.e.: as the result of addition of motives over a process whose duration, perhaps long, we do not know. Fil: Gheco, Lucas Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Catamarca. Escuela de Arqueología; Argentina Fil: Quesada, Marcos Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Catamarca. Escuela de Arqueología; Argentina Fil: Ybarra, Gabriel Omar. Instituto Nacional de Tecnología Industrial; Argentina Fil: Polizsuk, Andrea. Instituto Nacional de Tecnología Industrial; Argentina Fil: Burgos, Omar. Grupo Argentino del Color; Argentina

The electronic, structural and morphological characteristics of passive layers formed anodically on tin in the 7–14 pH range were studied. Photocurrent spectroscopy measurements showed that Sn passive films behave as highly disordered n-type semiconductors. The measured band gap values, E g , diminish as the formation pH is increased. Fourier transform infrared reflection–absorption spectroscopy results indicate that the ratio between SnOH and SnOSn bonds in the passive films increases with increasing formation pH. At pH >12.5 the films contained appreciable amounts of lattice water. A correlation between E g and the hydroxylation degree of the films was proposed.

The electrochemical behaviour and solid state properties of passive oxide layers formed on binary tin + indium alloys in alkaline aqueous solution were studied by using photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). Results obtained from PCS and EIS measurements showed that the anodically formed tin oxides behaved as heavily doped, n-type amorphous semiconductors. From the photocurrent spectra the mobility gap energies of different passive layers were evaluated. The mobility gap exhibited a remarkable dependence on the alloy composition, shifting towards higher energies as the indium content in the alloy was increased. Impedance diagrams displayed a complex frequency response and the corresponding transfer function analysis employing both parametric identification procedures and non-linear fit routines, presented several contributions. The apparent flat-band potential obtained from Mott-Schottky plots depended on alloy composition, shifting more negatively with increasing indium content. On the basis of PCS and EIS data, a tentative scheme of the valence and conduction mobility edge energies for the different passive films was postulated and its correlation with the oxide layer composition critically discussed.

Calcium phosphate coating on metal implants is an effective method to improve the bioactive properties of the metallic surfaces. In the present study is examined the characteristics of hydroxyapatite coatings deposited on an alkali- treated titanium substrate by biomimetic method in a super- saturated calcium solution (SCS). The samples were treated in a 10 mol/l NaOH solution for 24 h at 60 °C and subsequently immersed in a SCS solution during 24 h. The treated surfaces and the coatings obtained were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that a laminar coating of hydroxyapatite had formed on pre-treated titanium substrate. Therefore, a NaOH pre-treatment is recommended as an effective method for preparing a bioactive calcium phosphate coating.

Immunosensors are compact analytical devices in which the event of formation of antigenantibody complexes is detected and converted, by means of a transducer, to an electrical signal, which can be processed, recorded and displayed. Different transducing mechanisms are employed in immunological biosensors, based on signal generation (such as an electrochemical or optical signal) or properties changes (such as mass changes) following the formation of antigen-antibody complexes. In this chapter, the basics of immunosensors are presented focused on the different transduction techniques used in immunosensing.

The development of an inmunosensor for the point-of-care detection of the foot-and-mouth cattle disease is presented. The detector is based on an ELISA method with electrochemical detection. A non-structural protein, 3ABC, is used to selectively detect antibodies is used to selectively detect anti-3ABC antibodies produced after infection. The biological test is performed onto a screen printed electrodes. A dedicated small, portable potentiostat is employed for the control of the sensors, as well as data acquisition, processing, and storage.

Proton ejection/injection during the redox switching of polyaniline (PANI) have been qualitatively measured employing the rotating ring-disk electrode in the amperometric mode at the ring. The ring response shows that there is proton ejection during the oxidation of a fully relaxed polymer both from the leucoemeraldine to emeraldine forms and from it to the fully oxidized form. During the reduction of the polymer there is proton injection. However, this process is incomplete for the emeraldine/leucoemeraldine transition, indicating proton equilibration is a slow process. The ring response during the second positive half-potential sweep (nonrelaxed polymer) shows that the ring current is much smaller, indicating the polymer is not in protonic equilibrium with the external electrolytic phase. © 2000 The Electrochemical Society. S1099-0062(00)04-028-1. All rights reserved.