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We investigated the effect of light activation on the gas sensors based on aligned nanowires (NWs). Due to almost monocrystalline perfection, NWs exhibit excellent chemical and thermal stability that makes them superior to polycrystalline thin-film sensors. Nanowires were aligned in two different ways: using Langmuir-Blodgett technique on a chip with electrodes being two microns apart, and using hydrothermal growth procedure to obtain inter-crossed nanowires. Our objective was to fabricate multiple aligned nanowire sensors that could mimic the advantages of a single NW sensors, but benefiting from a macroscopic alignment procedure that avoid the use of lithography for making contacts on a single nanowire. In the present study, we investigated the effects of illumination wavelength (sub and supra band-gap) on the sensing capabilities of the developed structures at room temperature. Light activated devices were found effective for NO 2 sensing, while no interference to ethanol and relative humidity was observed.

Nowadays miniaturized sensors have become more and more important in order to monitor several fields of urban ambient and human life carefully. Low cost synthesis of nanostructured metal oxides for gas-sensing application is therefore of crucial importance for a mass production. Herein, NiO nanostructures were grown and used to realize sensors selective to hydrogen gas in presence of liquefied petroleum gas (LPG), to be used on portable and isolated fuel cell systems. NiO p-type semiconducting nanowires with polycrystalline structure were prepared via an easy, cheap and scalable hydrothermal method. Morphology and crystal structure of the NiO nanowires were characterized by scan electron microscopy, X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The nanostructured material was then tested as hydrogen sensor showing very good performance in terms of sensor response (110%), stability, speed of response and recovery (20 s) and selectivity in presence of LPG (a ratio of 200 times).

In this study, carbon screen-printed electrodes (SPEs) modified with gold nanoparticles (AuNPs), were prepared for label-free detection of Escherichia coli(E. coli) O157. AuNPs were synthesized by an electrochemical method and then modified on the carbon SPEs to improve the stability and effectiveness of the biosensor. Anti-E. coli O157 antibody was immobilized on the modified SPEs via -NHS cross-linking. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were selected to investigate electrochemical properties of modified carbon SPEs in a 5.0 mM K3[Fe(CN)6]/ K4[Fe(CN)6] added with 0.1 M KCl as well as to detect E. coli O157 bacteria. Results showed that the carbon SPEs were successfully modified with AuNPs of 18.0 ± 1.6 nm. The electrochemical signal of modified SPEs was stable after CV cycles, and the charge transfer resistance (Rct) decreased approximately to half of its initial value. Importantly, electrochemical biosensors based on AuNPs-modified carbon SPEs could detect E. coli O157 in the range of 10–106 CFU/mL without labels. The limit of detection was found at 15 CFU/mL with a signal-to-noise ratio of 3:1, and the time of detection was about 30 min. The success of as-prepared biosensor could open a strategy of portable diagnostics for label-free and quick detection of bacterial pathogens causing food-borne diseases, hospital-acquired infections as well as the emerging and re-emerging infectious diseases.

The use of micro- and nano-sensors is nowadays becoming more important in order to monitor several aspects of human life and environment. Controlled production of metal oxides nanostructures for gas-sensing applications is therefore crucial to integrate nanosensors to most systems, as they are ideal materials for such utilization. Here, nickel oxide (NiO) polycrystalline nanowires were grown and used to realize sensors that can selectively detect hydrogen and ethanol gas. NiO semiconducting nanowires with polycrystalline structure were grown through an easy, cheap and scalable hydrothermal procedure. Morphology and crystal structure of the NiO nanowires were investigated by energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The NiO nanostructures were then tested as gas sensors showing very good performance in terms of sensor response (107% for hydrogen, 136% for ethanol), stability, response and recovery times (20 s for hydrogen, 35 for ethanol). Their tunable dual-selectivity to hydrogen and ethanol make them ideal for use in ethanol steam-reforming systems.(C) 2016 Elsevier B.V. All rights reserved.

Gas nanosensors are nowadays very important to monitor environment and human conditions in many fields. Low cost synthesis of nanostructured metal oxides is thus crucial to satisfy this need to the best. Herein, nickel oxide p-type semiconducting nanowires with polycrystalline structure were prepared by a facile and scalable hydrothermal method. Morphology and structure of the NiO nanowires were investigated by scan electron microscopy, X-ray diffraction and transmission electron microscopy. The nanostructured materials were then tested as ethanol sensors showing good performance in terms of sensor response, stability, speed and selectivity towards ethanol, ammonia and liquefied petroleum gas. (C) 2015 The Authors. Published by Elsevier Ltd.

In this work we have grown one-dimensional (1D) and two-dimensional (2D) zinc oxide nanostructures. Changing the deposition parameters we were able to obtain ZnO nanowires with an average diameter of 80-250 nm. Nanosheets grown in different conditions show thickness values in the range 70-360 nm. These kinds of nanostructure have been used to fabricate conductometric gas sensors for liquid petroleum gas (LPG) detection. Different sensing parameters are investigated in both cases as a function of the dimensionality and size of the zinc oxide nanostructures. A first approximation of the "depletion layer sensing mechanism" is used to explain how the geometrical factors of one- and two-dimensional nanostructures affect their sensing parameters. The depletion layer affects two dimensions of nanowires and only one of nanosheets. This greatly improves the sensor response of 1D-nanostructures. On the other side two-dimensional nanostructures have a larger cross-section, which increases the base current, thus lowering the limit of detection. At the same operative conditions, nanowires show a better percentage response when compared to similar thickness nanosheets, but 2D nanosheets demonstrate an improved limit of detection (LoD). (C) 2015 Elsevier B.V. All rights reserved.

Low cost synthesis of nanostructured metal oxides for gas sensing application at low temperature is nowadays of crucial importance in many fields. Herein, NiO p-type semiconducting nanowires with polycrystalline structure were prepared by a facile and scalable hydrothermal method. Morphology and crystal structure of the NiO nanowires were investigated by scan electron microscopy, X-ray diffraction, and transmission electron microscopy. The nanostructured material was then tested as hydrogen sensor showing very good performance in terms of sensor response, stability, absence of drifts, and speed of response and recovery. The selectivity of the NiO sensor to hydrogen towards other gases (ethanol, ammonia, and liquefied petroleum gas) was found to be good.