Gas-Sensing Properties of Thermally-Oxidized Metal Oxide Nanowires

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Niobium and Tungsten Oxide Nanowires for Chemical Sensor

AbstractThin films of tungsten and niobium (WNb) were the starting point for the growth of metal oxide nanowires. RF Magnetron sputtering was used to deposit a layer of 100nm on 2 · 2 mm2 alumina substrates. Prepared samples were thermally oxidized to obtain the growth of nanostructures whose morphology was investigated by a scanning electron microscope (SEM). Structural properties of these nanostructures were investigated by RAMAN spectroscopy. Functional characterization was carried out using a homemade test chamber. Interdigitated contacts and heating elements were deposited by DC Magnetron sputtering, and samples were bonded to TO packages thanks to gold wires. The gas sensing properties of samples were analyzed in a wide range of working temperatures for different target gases in order to verify the best working condition

NiO/ZnO nanowire-heterostructures by vapor phase growth for gas sensing

Physical interface between p and n-types semiconducting materials known as p-n junction or heterojunction represents the key technology in many electronic and optoelectronic devices such as gas sensors. In this work we are presenting a novel method for the growth of NiO/ZnO (NWs) based heterostructures with vapor phase mechanism and their preliminary sensing study for acetone. To fabricate the NiO/ZnO NWs heterostructures, firstly NiO nanowires were grown on alumina substrates with VaporLiquid- Solid (VLS) method and then Vapor-Solid (VS) method was used for the growth of ZnO nanowires on as grown NiO nanowires. The surface morphology of NiO nanowires and NiO/ZnO heterostructures were investigated with scanning electron microscopy (FE-SEM). Raman spectroscopy has also been used for the structural characterization of heterostructures. A set of conductromertric sensing devices based on NiO/ZnO heterostructures have been prepared. The preliminary sensing performance of NiO/ZnO NWs heterostructure devices towards acetone at temperature of 400 degrees C is reported in this work. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

Titanium dioxide nanostructures chemical sensor

Titanium dioxide (TiO2) nanostructures were grown directly on the sensitive area of the transducer. A titanium thin film was deposited on 2 . 2 mm(2) alumina substrates by RF magnetron sputtering and hydrothermal method was used to achieve TiO2. This method is characterized by the use of different solutions (KOH, NaOH), a not stirred pressure reactor and a heating system. As-prepared samples require an acid treatment followed by a calcination step to obtain pure TiO2 nanostructures. The nanostructured morphology was confirmed by a scanning electron microscope (SEM) and their structural properties were investigated by RAMAN spectroscopy. Obtained samples were used as gas sensors, and their behaviour towards several gaseous species was analysed in a wide range of working temperatures. Measurements were carried out in a test chamber, investigating the change in the electrical conductance due to the surrounding atmosphere

Niobium Oxide Nanostructures for Chemical Sensing

AbstractNiobium oxide nanostructures were synthesized by hydrothermal method starting from niobium films deposited by RF magnetron sputtering on 2 × 2 mm2 alumina substrates. The samples were firstly treated with a KOH solution and with HNO3, and then annealed to obtain the Nb2O5 nanostructures. A scanning electron microscope (SEM) was used to investigate the morphology of the samples, while RAMAN spectroscopy was used to analyse their structural properties. In order to study the functional properties of the material, electrical contacts and heating elements were deposited over the substrates by DC magnetron sputtering. The as-prepared samples were mounted on TO packages using gold wires. Afterwards, functional tests were performed in a test chamber to investigate their electrical conductance variation as a function of the surrounding atmosphere and thus the sensitivity to different gaseous species

Influence of Nb-doping on hydrogen sensing performance of WO3 nanowires

Tungsten oxide nanowires were synthetized by thermal oxidation in vacuum, using a custom tubular furnace, adding niobium in the growth process to evaluate the influence of niobium in the conductometric response towards hydrogen gas. Samples were characterized by XRD and Raman spectroscopy, to confirm the crystalline structure of the material. The conductometric response of fabricated sensors was evaluated towards hydrogen gas. The addition of small percentage of niobium during the synthesis enhance the hydrogen sensing performance of the devices. (C) 2016 The Authors. Published by Elsevier Ltd

Electronic nose for the early detection of different types of indigenous mold contamination in green coffee

In the last few years Electronic Noses (ENs) have been revealed to be a very effective and fast tool for monitoring the microbiological spoilage and food quality control. European regulations report the maximum concentration of mycotoxins permitted in green coffee beans. The aim of this study was to test the ability of a novel EN, equipped with an array of MOX gas sensors based on thin films as well as nanowires, to early detect mold contaminations from Aspergillus spp., in cooperation with classical microbiological and chemical techniques like Gas Chromatography coupled with Mass Spectroscopy with SPME technique. In general the selection of the green coffee is controlled by visual inspection of shape, color and size. However, this process in often not enough to prevent the entrance in the food chains of contaminated products. We have demonstrated that the novel EN is able to early detect the qualitative and quantitative differences between contaminate and uncontaminated samples. Achieved results vividly recommend the use of our EN as a quality control tool in coffee producer industr

Tungsten Oxide Nanowires Chemical Sensors

AbstractTungsten oxide nanowires have been synthetized by a simple thermal oxidation route in an oxygen atmosphere, at low vacuum pressure. The morphology of the nanostructures was investigated by scanning electron microscope (SEM).Chemical sensors were fabricated using tungsten oxide nanowires as active layer, directly deposited on the transducer. Gas sensingperformances were evaluated towards some target chemical species (CO, NO2, NH3, Acetone, Ethanol). Firstly, a temperature screening was performed in presence of a fixed gas concentration, to determine the optimal working temperature of the sensors. Then, calibration curves for some chemical species were estimated. The influence of relative humidity was taken into account. Fabricated devices seem very promising for the detection of ammonia and carbon monoxide

Low temperature gas sensing properties of Graphene Oxide/SnO2 nanowires composite for H-2

In this work Graphene Oxide (GO) and SnO2 nanowires (NWs) composite sensing performance were studied. Single crystal SnO2 NWs were directly grown by thermal evaporation method and GO was successfully synthesized using modified Hummers method. RF magnetron sputtered Pt particles were used as a catalyst for the growth of SnO2 NWs. Drop cast technique was used to deposited GO on top of the SnO2 NWs. FE-SEM (LEO 1525) was used to investigate the morphology of SnO2 NWs and GO. Fabricated sensors were tested towards various concentration of H-2 at different working temperatures. This GO/SnO2 hybrid sensors show a reversible response to H-2 at low operating temperature. (C) 2016 The Authors. Published by Elsevier Ltd