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Platinum nanoparticles (PtNPs), with diameters of 3–10 nm, were synthesized by water phase reduction, using 3-mercapto-1-propanesulfonate (3MPS) as a hydrophilic capping agent. PtNPs were deposited by a dipcoating technique on titania nanofibers (TiO2NFs), obtained by electrospinning. The investigated properties of the Pt–TiO2 hybrid at room temperature show that this material combines the properties of photoconduction of titania and the photocatalytic activity of the hybrid. To assess the best performance of Pt–TiO2, different measurements were performed at room temperature, comparing hydrogen response under UV of the uncoated TiO2NFs, compared with the Pt–TiO2 system prepared with two different amounts of PtNPs. During the sensing tests toward hydrogen an enhancement of photoconductivity (150%), an increase in response (400%) and an overall improvement of their dynamic behaviour were observed.

In this work the ability to perform desorption studies by using a micro-thermogravimetric device is demonstrated. The instrument consists of an oscillating quartz crystal microbalance with an integrated micro-heater that might turn out to be extremely useful in the study of the desorption of volatile compounds from refractory materials. The experiment here discussed has been performed by studying the release of adsorbed water from clay. Clay has been principally chosen because it is a material known for its ability to desorb and subsequently re-adsorb water at low temperatures and it might be considered a test mineral for a large number of applications, from first guess analysis of agricultural soil to quick inspection of materials of planetological interest (e.g., asteroid regolith). Results show that the device can be in stable operative conditions at 100 °C with 0.5 W of power supplied, allowing to measure the amount of desorbed water. In particular, as expected, it has been possible to assess that the desorbed water amount depends upon the working temperature, being less than 3 wt.% at 70 °C and about 5 wt.% at 90 °C.

Gas and volatile organic compounds (VOCs) release in soil is known to be linked to microbial activity and can differently affect the life of organisms in soil. Electronic noses (E-noses) are sensing devices composed of sensor arrays able to measure and monitor gases and VOCs in air. This is the first report on the use of such a sensing device to measure specifically microbial activity in soil. In the present study, gamma-irradiated sterilised soil was inoculated with Pseudomonas fluorescens. To be sure for a rapid microbial growth and activity, two pulses of nutrient solution with organic and inorganic C, N, P and S sources were added to soil and the resulting microcosms were incubated for 23 d. During the incubation, respiration and enzyme activities of acid phosphatase, beta-glucosidase, fluorescein diacetate hydrolase and protease, were measured, and microbial growth as global biomass of vital cells based on substrate-induced respiration (SIR-C(mic)) and enumeration of viable and culturable cells by means of dilution plate counts (CFU) were also monitored. Concurrently, VOCs and/or gas evolution in the headspace of the soil microcosms were measured through the E-nose, upon their adsorption on quartz crystal microbalances (QCMs) comprising the sensory device. The E-nose typically generated an odorant image (olfactory fingerprint) representative of the analysed samples (soils) and resulting from the concurrent perception of all or most of the analytes in headspace, as it commonly happens when several selective but not specific sensors are used together (array). The basic hypothesis of this study was that different soil ecosystems expressing distinct microbial metabolic activities, tested through respiration and enzyme activities, might generate different olfactory fingerprints in headspace. Furthermore, the possibility to detect several substances at the same time, released from the soil ecosystems, possibly deriving from both abiotic and biotic (microbial metabolism) processes provides an "odorant image" representative of the whole ecosystem under study. The E-nose here used succeeded in discriminating between inoculated and non-inoculated ecosystems and in distinguishing different metabolic and growth phases of the inoculated bacteria during incubation. Specifically, E-nose responses were proved highly and significantly correlated with all hydrolytic activities linked to the mobilisation of nutrients from soil organic matter and their cycling, with CO(2) fluxes (respiration and presumed heterotrophic fixation) and with P. fluorescens population dynamics during exponential, stationary and starvation phases measured by SIR-Cmic and CFUs. Interestingly, the E-nose successfully detected soil microbial activity stimulated by nutrient supply, even though none of the catalytic activities tested directly produced VOCs and/or gases. The E-nose technology was then proved able to supply a real holistic image of microbial activity in the entire gnotobiotic and axenic soil ecosystems. (C) 2011 Elsevier Ltd. All rights reserved.

This study focuses and discusses the effects of temperature and humidity on electrospun conductive nanofibers, made with different polymer blends, deposited directly on interdigitated electrodes. The selected conductive polymers were based on blends of polyaniline emeraldine salt form and three different carrier hosting polymers: polyvinilpyrrolidone, polystyrene, and polyethylene oxide respectively. The obtained fibrous layers were investigated by the electrical measurements and morphological analysis (scanning electron microscopy). The study was made on the correlation between the electrical changes and morphological discrepancies due to temperature treatment. Moreover, this article reports the effects of relative humidity variations on electrical parameters. Since polyaniline is a well-known sensing material for different gases and volatile organic compounds, this study could be considered a supportive study for employing of the mentioned polymer blends as chemical interactive materials in gas sensor applications.

Olfactory receptor neurons in the mammalian olfactory system transduce the odour information into electrical signals and project these into the olfactory bulb. In the biological system the huge redundancy and the massive convergence of the olfactory receptor neurons to the olfactory bulb are thought to enhance the sensitivity and selectivity of the system. To explore this concept a polymeric chemical sensor array consisting of 216 (65,536) sensors comprising tens of different types will be built in the frame of the FP7 NEUROCHEM project. To interface such a large sensor array, a topological array configuration with n rows and m columns has been adopted in order to reduce the total wiring connections to n + m. A detailed numerical analysis of the electrical crosstalk deriving from such a configuration has been carried out for elucidating advantages and limitations of the scanning algorithm. A prototype of the transducing array has been designed and an electronic scanning system capable of reading the 65,536 sensing elements array has been realized.

In this paper we present the design and fabrication of a humidity sensor on ultra thin (8 μm) flexible polyimide substrate. The ultra thin flexible substrate can be preserved also when a read-out electronic interface is integrated by using Polycrystalline Silicon Thin Film Transistors technology. The sensor device is a capacitor where a thin layer of [bis(benzo cyclobutene)] is used as a dielectric sensitive material between two metal electrodes. The electrode layout has been designed with the aid of numerical simulations in order to optimize the sensor performances. The fabricated sensor has shown sensitivity to relative humidity of 0.38%/RH% and a linearity of 0.996 in the range of 10–90 RH%. Furthermore, measurements regarding the sensor response time, different bending and bias voltage effects have been performed.

Acoustic sensors are generally known as high-resolution mass-sensitive transducers. They are composed of piezoelectric crystal plus at least one layer of chemically interactive material (CIM) deposited on one of their surfaces in order to infer a given chemical sensitivity. Electronic noses based on quartz crystal microbalances (QCM) are widely used in volatile organic compounds analysis. These multisensor systems typically employ a number of quartzes coated with different CIM having broad and overlapping sensitivity. Depending on the number of sensors used and taking into account the electronic units needed to drive them, the total volume of such a system may be considerable. In the present work we have shown the possibility of including four different QCM in the same quartz plate in order to reduce the overall space dedicated to the sensors, realizing the so called multichannel quartz crystal microbalance (MQCM). Moreover we have investigated the possibility of using a single oscillator circuit to drive the oscillations for all the four channels of the MQCM. The work outlines the advantages of implementing this single oscillator technique in terms of volume reduction, better homogeneity in the sensor array behavior and power saving. The overall system comprising the sensor array, the driving oscillator and the electronic interface has been built and successfully tested. (c) 2007 Elsevier B.V. All rights reserved.

In this work two recently developed techniques (solid phase microextraction-SPME associated to gas-chromatography mass spectrometry-GC/MS analysis and electronic nose-EN), able to analyse the headspace of solid or liquid samples, were used to monitor the possible degradation of phenanthrene in an artificially contaminated soil. The analysis by SPME-GC/MS showed a drastic decrease of phenanthrene content after 30 days of incubation (-92%) and different treatments with nutritive solutions and/or surfactant improve this rate up to 97%. Differently, the analysis of soil headspaces by EN, processed by principal component analysis (PCA), showed that both contaminated and uncontaminated soil samples (controls) might be distinguished on a temporal scale and that they were delayed relative to controls. The application of PLS-DA to chromatograms obtained by SPME-GC/MS pointed out the presence, in polluted soils, of a series of possible indicators involved in the phenanthrene degradation, which were completely absent in relative control sample. In questo lavoro, due tecniche sviluppate recentemente (la microestrazione in fase solida-SPME abbinata alla gascromatografia e all’analisi della massa molecolare-GC/MS e il naso elettronico-EN) capaci di analizzare lo spazio di testa di campioni solidi o liquidi sono stati usati per minitorare la possibile degradazione del fenantrene in suoli contaminati artificialmente. L’analisi tramite SPME-GC/MS ha mostrato una drastica diminuzione del contenuto di fenantrene dopo 30 giorni di incubazione (-92%) e l’applicazione di trattamenti con soluzioni nutritive e/o surfattanti hanno migliorato tale tasso di diminuzione fino al 97%. Differentemente, l’analisi dello spazio di testa tramite l’EN, processata tramite PCA, ha mostrato che sia i campioni contaminati che quelli non contaminati (controlli) potevano essere distinti su scala temporale ed inoltre la presenza di un ritardo nell’evoluzione degli ecosistemi contaminati con fenantrene rispetto a quanto osservabile nei controlli. L’applicazione della PLS-DA ai cromatogrammi ottenuti tramite SPME-GC/MS ha evidenziato la presenza, nei suoli contaminati, di una serie di possibili indicatori coinvolti nella degradazione del fenantrene che erano completamente assenti nei relativi campioni di controllo. L'articolo è disponibile sul sito dell'editore: http://www.sciencedirect.com

This work deals with temperature characterization of embedded resistors deposited on CAM (Contamination Assessment Microbalance), quartz crystal microbalances developed for thermogravimetric analyses in Space. Designed instrument is innovative thanks to the deposited resistors that allow quartz crystal thermal control by direct heating of the sensing area. Characterization of the deposited materials is of primary importance to provide accurate temperature measurement and retrieve reliable results from the instrument thermogravimetric analyses. Linearity of the Cr-Au material has been verified between −20 and 100 °C and confirmed at cryogenic temperatures. Characterization has been complemented with thermal mapping of an instrument mockup in air. Agreement between reading of the deposited sensor and IR thermography of the crystal has been achieved and the measured thermal map allowed validation of the instrument design.

Long-term manned space missions requires a continuous monitoring of the air quality inside the spacecraft. For this scope, among several different solutions, electronic noses have been considered. On behalf of European Space Agency an electronic nose specifically designed for air quality control in closed environment is under development. After several ground experiments concerning the monitoring of a biofilter efficiency, the instrument has been tested during the ENEIDE mission on board of the International Space Station. in this paper the instrument main concepts and its performance in ground and space experiments are illustrated.

Noble metal nanoparticles (MNPs) with controlled diameters in the range 5-15 nm, have been prepared by chemical wet reduction reactions starting from Au precursor in the presence of bifunctional thiolate, i.e. biphenyl-4,4′-dithiol. MNPs have been deposited on electrospinned titania nanofibers by dipping. The composite has been investigated at room temperature in resistive type device under UV irradiation. IV curves show properties of photoconduction and upon exposure towards sulphur dioxide (SO 2 ) a sensing behaviour has been observed. The devices shoved an exponential decay for increasing values of SO 2 concentration.

Terzo e conclusivo rapporto tecnico progetto TEMIBILE, stipulato in data 16/10/2013 con 3V-CHIMICA Srl, nell'ambito del Bando POR&FILAS 2007-2013, che ha previsto lo sviluppo di un prototipo modulare basato su QCM integrate con microriscaldatore per il monitoraggiodi VOCs/gas e particolato atmosferico.

Piezoelectric Crystal Microbalances (PCM’s) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM’s are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results’ accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

The use of nanostructured materials, such as those based on metal or metal oxides, has opened a new way to enhance the performances of chemical sensors making them able to detect gases at ppb level. In this type of sensors, the conductance is modulated by the presence of analytes that interact through physical-chemical processes of absorption and desorption, inducing changes in mobility or carriers density. The nano-scale dimensions of these materials enhance the interaction phenomena in terms of time and responses. In order to activate the physical/chemical interaction processes of the sensors based on oxide materials, an high operating temperature (200–400 °C) is required, resulting in significant power consumption. In this chapter, we report our recent studies on the possibility to exploit the titania photoconduction to develop gas sensor devices working at room temperature. We present the characterization of two different photoconductive Electrospun sensing layers: the first one is composed of titania nanofibres (TiO2 NFs) and the second of TiO2 NFs decorated with Pt nanoparticles (PtNPs) ranging from 5 to 10 nm.

Our previous study of interaction between low intensity radiation at 53.37 GHz and cell-size system – such as giant vesicles – indicated that a vectorial movement of vesicles was induced. This effect among others, i.e. elongation, induced diffusion of fluorescent dye di-8-ANEPPS, and increased attractions between vesicles was attributed to the action of the field on charged and dipolar residues located at the membrane–water interface. In an attempt to improve the understanding on how millimeter wave radiation (MMW) can induce this movement we report here a real time evaluation of changes induced on the movement of giant vesicles. Direct optical observations of vesicles subjected to irradiation enabled the monitoring in real time of the response of vesicles. Changes of the direction of vesicle movement are demonstrated, which occur only during irradiation with a “switch on” of the effect. This MMW-induced effect was observed at a larger extent on giant vesicles prepared with negatively charged phospholipids. The monitoring of induced-by-irradiation temperature variation and numerical dosimetry indicate that the observed effects in vesicle movement cannot be attributed to local heating.

An important drawback of semiconductor gas sensors is their operating temperature that needs the use of heaters. To overcome this problem a prototyping sensor using titania nanofibres (with an average diameter of 50 nm) as sensitive membrane were fabricated by electrospinning directly on the transducer of the sensor. Exploiting the effect of titania photoconductivity, resis- tance variations upon gas interaction under continuous irradiation of ultra violet light were measured at room temperature. The resistive sensor response was evaluated towards ammonia, nitrogen dioxide and humidity. The sensor exhibited a higher response to ammonia than to nitrogen dioxide, especially for concentrations larger than 100 ppb. For 200 ppb of ammonia and nitrogen dioxide, the responses were*2.8 and 1.5 %, respectively.

A hybrid electrospun nanofibrous framework of titania, generated at first by growing up the nanofibres directly onto an interdigitated electrode (IDE) as a transducer and then coating them with an ultra-thin film of PEDOT–PSS, was investigated as a potential sensing material for NO. The stoichiometric oxidation of NO into NO 2 by CrO 3 , allowed the conductometric sensor to detect analyte concentrations down to 1 ppb, then being suitable for asthma monitoring. The sensing features were assessed by following the sampling procedures specified by the ATS-ERS guidelines, and testing potential interfering substances such as H 2 O, CO 2 and O 2 . The resulting sensor performances seemed to be mainly related to the peculiarity of the framework structure (through AFM, SEM, TEM and MIA investigations) and to the phenomena occurring at the interface between the TiO 2 fibres and the conductive polymer.

Flexible sensors are gaining increasing interest in a number of applications, including biomedical, food control, domotics and robotics, having very light weight, robustness and low cost. In order to improve signal-to-noise ratio, integration of readout electronics is crucial and several technologies are available for the fabrication of thin film transistors (TFTs) based circuits on flexible substrates. Among these technologies, the low temperature polycrystalline silicon (LTPS) is particularly attractive, since LTPS TFTs show excellent electrical characteristics, good stability and offer the possibility to exploit CMOS architectures. The different aspects for the direct fabrication of LTPS TFTs on polymer substrates are reviewed and the specific fabrication process adopted on ultrathin polyimide substrates is described in some detail. Then, as examples of flexible sensing systems, we present both chemical and physical sensors integrated with LTPS TFTs frontend electronics. The present results can pave the way to advanced flexible sensing systems, where sensors and local signal conditioning circuits can be integrated on the same flexible substrate.

Electrospinning seems to be the most suitable technique to obtain long polymer fibres of submicron diameters. This technology is mostly suitable whenever the high surface area to volume ratio is required, e.g. in highly efficient filtering materials, scaffolds for tissue engineering, nano-chemical sensors, etc. In the latter case, nanofibrous interacting layers enhance the available sensing surface area, providing an increase in sensitivity and capture efficiency, due to surface area approximately one or two orders of magnitude higher than in continuous films. Among electrospun conductive polymer (CP) sensors, polyaniline (PANi) has been one of the most investigated solid state materials due to both its environmental stability (up to 300°C) and peculiar sensing mechanisms. For instance, a dedoping effect through deprotonation is expected to happen when ammonia gaseous is adsorbed onto PANi molecules. On the contrary, acidic gases (HCl, H2S, and CO2 with water) cause PANi doping through protonation. In addition, volatile organic compounds (VOCs) change conductivity of the solid state polymer. Each of these events upon polymer exposure to analytes can be measured as current variations detectable through suitable resistors [1]. Electrospun blends of PANi and insulating host polymers (HPs) have been designed, prepared and studied in our laboratory to assess the sensing features of nanofibres resulting from the combination of CP electrical conductivity and HP physical properties [2]. In order to create a new generation of environmental friendly sensors, a biocompatible and biodegradable nanofibrous sensor based on PANi and poly-3-hydroxybutyrate (PHB) was fabricated, characterized and tested to detect VOCs and gases. Specifically, the interdigitated electrodes (IDEs) coated with 10 min electrospun fibrous layers at increasing concentrations of PANi, were investigated through optical microscopy, SEM, AFM and TEM. All layers were highly porous, with interconnected void volumes and high surface-to-volume ratios. Additionally, the polymeric fibres covered both all electrodes in each IDE and the gaps between them, providing electrical connection within each transducer. The sensor retained good mechanical integrity and thermal stability until six months, at least, which reflected into reproducible sensing properties, and it was water resistant. All sensors fabricated at different PANi concentrations resulted conductive and fast responding to gases (NH3, NO2) and VOCs (acetone, acetic acid). The amount of PANi in nanofibres was a key factor for layer conductivity (low noise, increase in current), dependence on environmental parameters (humidity, temperature) and interaction with gases and VOCs.

We have performed noise measurements on 5 different carbon black polymer composite resistive gas sensors, both in an inert chemical atmosphere (dry nitrogen) and in an active chemical atmosphere (with toluene or ethanol vapour). All the sensors exhibited the presence of significant 1/f noise for biasing currents in the μA range; moreover, we show that the level of 1/f noise is strongly dependent upon the chemical environment and, in particular, the concentration of the vapour. These results, obtained for the first time with this chemically sensitive nanocomposite material, should help in the creation of circuit models and also in the design of low noise chemical sensors using carbon-black composite materials. Additionally, in the thinnest sensor, at sufficiently high biasing currents we found the deactivation of 1/f noise above a certain frequency, with an unexpected residual 1/f γ excess noise (γ around 2.2) which, to our knowledge, has not been observed before. Interestingly, this unusual excess noise was almost insensitive to the presence of either toluene or ethanol vapour; this observation may offer insight on the origins of both 1/f and the measured 1/f γ excess noise in composite polymer resistors. Finally, we have estimated the available noise energy per trap for a given adsorption process which may be used to characterize the noise fluctuations in a chemical environment. We believe that our work will also enable the construction of better SPICE models to help in the design of advanced CMOS transduction circuitry. © 2012 Elsevier B.V.

The electronic nose (E-nose) is a sensing technology that has been widely used to monitor environments in the last decade. In the present study, the capability of an E-nose, in combination with biochemical and microbiological techniques, of both detecting the microbial activity and estimating the metabolic status of soil ecosystems, was tested by measuring on one side respiration, enzyme activities and growth of bacteria in natural but simplified soil ecosystems over 23 days of incubation through traditional methodologies, and on the other side VOCs and/or gases evolution in their headspace during the same period through the E-nose. Both kinds of measurements, i.e. biochemical-microbiological and sensorial, succeeded in discriminating between inoculated and non-inoculated microcosms and in distinguishing different phases of bacterial growth and activity during the incubation. E-nose responses were highly and significantly correlated with all catalytic activities, respiration and different phases of bacterial growth. Hence, the E-nose was proved able to detect microbial activity in natural soil ecosystems. The metabolic status of these soil ecosystems was calculated on the base of some of the parameters previously tested in order to obtain a metabolic index (MI), ranging between 0 and 1. These MIs were then grouped into 3 classes, corresponding to a low, medium and high metabolic status. All the other measures were used as a multi-type data set in a partial least square discriminant analysis to generate a model capable of classifying the soil microcosms at different sampling dates according to the 3 classes of MIs. The resulting outcomes confirmed that the E-nose technology combined with both metabolic and biomass parameters can altogether represent reliable indicators of the metabolic status of soil ecosystems.

Electrospun nanofibres have been confirmed to be very good candidates for ultra-sensitive gas sensors since they greatly improve surface area to volume ratios of coatings, which in turn affect two additional and crucial features for sensors: high sensitivity and fast response time. Electrospinning is a simple method for the deposition of long (up to several centimetres) nanofibres, aligned or non-woven, directly onto suitable transducers. Such a structured layer may have better properties than a compact film, providing faster adsorption and minimising some bulk effects (i.e. long diffusion–desorption time, analyte entrapment, etc.). Electrospun conductive polymers (CPs) have been specifically investigated for developing smart sensors whose electrical properties change upon interactions with the analytes. Polyaniline is one of the most interesting CPs for gas sensing, because of its conductive features, when doped, as well as its thermal stability and sensing performance. The sensing mechanisms are different, depending on the nature of both PANi and the targeting analytes. Thus, various blends of polyaniline and insulating host polymers have been planned, prepared, deposited and studied to optimise the properties of sensors consequent to the combination of the electrical conductivity of CP and of the physical properties of the host polymer. Host polymer carriers cause great modifications to the topology of the interacting surface (diameter and length of the fibres, roughness, porosity, presence of beads and grains, non-woven framework and branched junctions, adhesion, etc.), in addition to the different affinity to the analytes tested. However, they enable electrodes to function over a wider dynamic range of gas or vapour concentrations. The polymer features have been also characterised over a range of water vapour concentrations and temperatures.

In this paper we present the design and fabrication of a fully flexible sensorial system, composed of three different sensor units implemented on an ultrathin polyimide substrate of 8 μm thick. Each unit is composed by a capacitive chemical sensor integrated with readout electronics. The sensors are parallel plate capacitors with the top electrode properly patterned to allow analytes diffusion into the dielectric that acts as chemical interactive material. Three different polymers, poly(tetrafluoroethene) (PTFE), poly(methyl 2-methylpropenoate) (PMMA) and benzocyclobutene (BCB), were used as dielectrics. A ring oscillator circuit, implemented with polysilicon thin film transistors (PS-nTFT), was used to convert the capacitance variations into frequency shifts. The electronic tests show oscillating frequencies of about 211 ± 2 kHz and negligible frequency shifts under different bending radius conditions. Furthermore, system response to some alcohols concentrations (Methanol, ethanol, 1-butanol, and 1-propanol) is reported and data analysis proves that the system is able to discriminate methanol from ethanol.

The aim of the present study is to combine a bio-inspired nanofibrous artificial epithelium to the electronic nose (e-nose) principles. The sensing device set up was an electronic nose consisting of an array of 9 micro-chemoresistors (Cr–Au, 3 × 3) coated with electrospun nanofibrous structures. These were comprised of doped polyemeraldine base blended with 3 different polymers: polyethylene oxide, polyvinilpyrrolidone and polystyrene, which acted as carriers for the conducting polymer and were the major responsible of the features of each fibrous overlay (electrical parameters, selectivity and sensitivity ranges). The two sensing strategies here adopted and compared consisted in the use of 2 different textural coatings: a single- and a double-overlay, where the double-overlay resulting from overdeposition of 2 different polymer blends. Such e-nose included a plurality of nanofibres whose electrical parameters were at the same time depending on each polymer exposure to analytes (NO2, NH3) and on the spatial distribution of the interlacing fibres. The morphology of the coating arrangements of this novel e-nose was investigated by scanning electron microscopy (SEM) and its sensor responses were processed by multicomponent data analyses (PCA and PLS) reporting encouraging results for detection and recognition of analytes at ppb levels.

Secondo rapporto tecnico attività

Risultati inerenti l'attività di Ricerca e Sviluppo da parte di IMM-CNR di Roma sugli obiettivi realizzativi stabiliti con MIR nel progetto dal titolo: "Nitric Oxide Exhaled Sensor Integrated System", NOESIS, Progetto di Ricerca presentato a FILAS a fronte del 1° Bando Pubblico Distretto Tecnologico delle Bioscienze I intervento per "Progetto Industriale e Sviluppo Precompetitivo", Delibera CIPE 35/05, avviato il 26 marzo 2009 e che sarà concluso il 25 marzo 2012.

We present the design and fabrication of a chemoresistive sensor array for the volatile organic compounds and gas detection. Different nanofibrous conductive polymers, produced by electrospinning technique, have been used as chemical interactive materials. Sensor array was integrated with read-out electronic circuits on flexible substrate. In order to obtain high electrical performances maintaining integration capability, on plastic materials, respect to standard c-Si CMOS technology, polycrystalline silicon thin film transistor based circuitry has been used. The performances of the fabricated sensor array have been tested with different concentrations of Methanol, Lactic acid and Ammonia.

This work describes a biosensor for direct measurements of carbon dioxide (CO2). The functionality of this device was tested by a QMB transducer coated by a liposome containing carbonic anhydrase (AC). During the CO2 adsorption process a change in the QMB frequency was observed. Another transducer was used in this context. By a high resolution temperature variation transducer, such as the LiTaO3. it has been possible to detect the heat generated during the reaction CO2 +H2O ->HCO3- + H+ developed inside the liposomes. In this work the response curves of both QMB and LiTaO3 are shown and commented.

In this paper we present the design and fabrication of two flexible sensor devices: humidity sensor and ammonia sensor integrated with electronic circuit interface on thin flexible substrate (8 mum). The transducers layout has been optimized by means of numerical simulations. A thin layer of Bisbenzocyclobytene (BCB) is used as dielectric sensitive material in humidity sensor. Conversely a mixed polymer layer based on polyaniline emeraldine base (PANi-EB) is used as sensing conductive polymer for ammonia.

In this work an attempt to obtain a more compact artificial system for gas sensing, properly designed on a transducer, is presented. This novel device can be applied for a wide application range such as environmental, bio-medical, agriculture etc. fields. In the Nature, a mucous layer covering olfactory receptor cells, selectively tunes chemical interactions among odorous molecules and sensing system. An odor, in fact, is perceived only if it is able to cross mucus of nasal cavity.

The response to relative humidity (RH) and alcohol vapors of resistive-type sensors based on nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymer poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), were investigated. Sensors based on ordered arrays of these nanostructured polymeric materials showed stable and reproducible current intensity variations in the range 10-90% of relative humidity at room temperature. Both polymers also showed sensitivity to aliphatic chain primary alcohols, and a fine tuning of the sensor response was obtained by varying the chain length of the alcohol in relation to the polarity. The nanostructured feature of polymeric-based membranes seems to have an effect on the sensing response and an enhancement of the sensitivity was observed for the response to water and alcohol vapor variations with respect to previous studies based on amorphous polyphenylacetylene. High stability of the polymeric nanostructured membranes was detected with no aging after two weeks in continuum stressing measurement conditions. © 2008 IOP Publishing Ltd.

In this work an attempt to obtain a more compact system for gas sensing, designed directly on a transducer, is presented. In the nature, a mucous layer covers the olfactory receptor cells of mammalians and selectively tunes the chemical interactions between odorous molecules and sensing systems. Such natural double layer design was reproduced in this study using a double coating comprised of a proper hydrophobic Teflonlike overlayer tuning the humidity interference between the odorous molecules and the sensitive matrix below consisting of a Zn-porphyrin film. This double coating was applied on both surfaces of the quartz crystal microbalance used for transducing into electrical signals the chemical signals deriving from the adsorption of volatile molecules. © 2008 Elsevier B.V. All rights reserved.

Acoustic sensors are generally known as high-resolution mass-sensitive transducers. They are composed of piezoelectric crystal plus at least one layer of organic matter to improve chemical sensitivity. The acoustic properties, resumed in the acoustic load impedance, can be exploited by measuring the electric parameters of an equivalent circuit. Some sensing results of a thickness shear mode resonator coated by increasing amounts of a porphyrin solid film have been studied and compared with the performances of the device (quality factor, impedance, motional parameters) to exploit the capabilities and the limitations of a porphyrin-based acoustic chemical sensor.

Although quartz microbalances (QMBs) are widely used, controlling their temperature is a challenge. Here a slightly modified quartz microbalance, driven by an original /spl Sigma//spl Delta/ electronic interface, acts as temperature sensor, flow sensor, heater, and resonator; no interference between the oscillator circuit and the /spl Sigma//spl Delta/ interface has been observed. In comparison with traditional solutions, the proposed approach is more accurate, faster, cheaper, more flexible, and more power efficient. As an additional, unique advantage of our system, the flow velocity is automatically measured by the QMB sensor itself. The technological and circuit solutions reported here are general and may be useful in other applications where temperature and/or flow velocity must be controlled.

We report a very simple, robust, and reliable on-chip fabrication method of a chemoresistive sensor based on silicon nanowires (NWs). Our method permits the use of nanowires without the need of their removal and transfer to a support different from the growth substrate. Our method, completely based on the silicon technology platform, exploits nanowires directly grown onto a selected area, over and between pre-patterned, interdigitated electrodes defined on oxidized silicon. The fabricated sensor is capable to detect NO2 down to a few ppb levels operating at room temperature. The sensor characteristics benefit of the presence of self-welded nanowires.

Hybrid sensors consisting of nanofibrous scaffolds of TiO2 coated with thin films of self-assembled conductive polymer (CPs) blends have been recently tested in their capability of detecting traces of some gaseous markers of metabolic diseases, treated meat or spoiled food and explosives, and the resulting sensors have been compared in their sensing properties. In the present study, fibresimilar chemoresistors, based on the integration of a nanosized TiO2 and different blends of organic polymers (PEDOT:PSS and PANi:PS) were designed and set up. The resulting sensors showed an overall enhancement of sensing performances (sensitivity, selectivity, rapid responses, etc.) and greater lifetimes, and decrease in drawbacks of each polymer. Sensing characteristics towards NO2 and NH3 were tested at both the equilibrium and within a shorter time upon the rapid sensor responses, and results were discussed. Since the reaction between sensors and analytes was assumed to occur at the interface between CPs and TiO2, the resulting film structures were also investigated through scanning and transmission electron microscopy.

This work presents the fabrication and the characterization of a chemoresistor based on titania nanofibers, produced by means of the electrospinning technique, with high sensitivity to some gases of relevant interest in fields like environment or medical applications, such as NH3 and NO2 without the need to use high temperatures (300-500iC). In order to obtain a reasonable sensor conductance and to enhance the sensor response and the signal to noise ratio, we have used an ultra violet (about 400 nm) light source to irradiate the titania nanofibers exploiting its photoconductivity. Sensor response, in terms of percentage of relative current shift, was about 1.2% for 125 ppb of NO2 and 1.5% for 110 ppb of NH3.

We present the results concerning the fabrication and characterization of a piezoelectric transducer based on electrospun polyvinylidene difluoride (PVDF) nanofibers. The deposition process was optimized to obtain aligned nanofibers and to maximize the overall piezoelectric effect. The piezoelectric properties were investigated depositing the material on interdigitated metal electrodes implemented on a thin flexible substrate. In order to generate a suitable mechanical stimulation, the device was coupled to an acoustic actuator and its response was recorded at different vibration frequency and during the interaction with humidity and ethanol.

In this work an attempt to obtain a more compact artificial system for gas sensing, properly designed on a transducer, is presented. This novel device can be applied for a wide application range such as environmental, bio-medical, agriculture etc. fields. In the Nature, a mucous layer covering olfactory receptor cells, selectively tunes chemical interactions among odorous molecules and sensing system. An odor, in fact, is perceived only if it is able to cross mucus of nasal cavity. A proper hydrophobic Teflon-like overcoating tunes chemical interactions, humidity free, between odorous molecules and sensing system, miming mucus covering olfactory receptor cells. Here the latters were represented by doped polyaniline added of polyethylenoxide. The interacting surface has been enormously enhanced creating nanofibrous coatings by electrospinning deposition technique. Such nanofibers can be compared with the olfactory cilia covered by mucus. Few modifications of both overlayers and nanofibrous polymers can encourage the developing of new chemical sensors for array sensor system generations. Surfaces analysis, electrical parameters and sensing properties of the double layers on interdigitated transducers have been investigated.