Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts

©2002 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: : http://link.aip.org/link/?APPLAB/81/1869/1DOI:10.1063/1.1504867Gas sensors have been fabricated using the single-crystalline SnO₂ nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO₂ , as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and 21550% for 0.5 ppm NO₂ at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb

Graphene-zinc oxide based nanomaterials for gas sensing devices

Herein, we report the preparation of a hybrid material by combination of modified graphene and ZnO. The morphological and compositional analyses of the obtained material have been performed by means of scanning electron microscopy and energy dispersive X-ray analysis. The functional properties of the prepared structures have been investigated for their application in gas sensor devices. The gas sensing performance of the hybrid material show that the structure can be used for fabrication of chemical sensors, as well as in electronic nose technology. (C) 2016 The Authors. Published by Elsevier Ltd

Response dynamics of metal oxide gas sensors working with temperature profile protocols

Abstract In this work we present the analysis of gas sensors working in modulated temperature mode with temperature varying according to exponential law. We integrate conductometric gas sensor based on semiconducting metal oxide layers and an ad-hoc developed electronics to present a sensing system based on a single sensor featuring a degree of selectivity arising from the exploitation of response dynamics features. In particular, a set of parameters is used to summarize the deviation of the response shape from the single exponential law

Copper oxide nanowires prepared by thermal oxidation for chemical sensing

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Zinc Oxide Nanowires Deposited on Polymeric Hotplates for Low-power Gas Sensors

Zinc oxides (ZnO) nanowires were successfully deposited on plastic low-power micro-hotplates using the thermal oxidation technique. Metallic zinc layer was deposited on the sensing transducer by RF magnetron sputtering and then oxidized in a controlled atmosphere in order to obtain ZnO nanostructures. Morphological investigations confirmed the nanometric dimensions of the fabricated nanostructures. The n-type behavior of the nanostructured material was evaluated towards different chemical species to highlight the electrical properties of the materials. Calibration curves for the detection of several chemical species were defined. © 2012 The Authors. Published by Elsevier Ltd

Candida milleri detected by Electronic Nose in tomato sauce

AbstractThe tomato sauce is a product of great importance for its massive production in Italy. Microbial contamination is a constant concern for the industries, causing severe economic losses, posing risks to consumers’ health and contributing to an enormous wasting of food. This work shows how the use of the Electronic Nose (EN) EOS 507C can be effective compare to the current procedures in the food production. EN composed of an array of thin film sensors, 6 Metal Oxide (MOX). All the samples were analyzed in parallel with classical chemical technique, like GC-MS with SPME

Multiparametric Porous Silicon Sensors

We investigated the possibility of using several sensing parameters from porous silicon in order to improve gas selectivity. By fabricating porous silicon optical microcavities, three independent quantities can be measured, i.e. the electrical conductance, the photoluminescence intensity, and the wavelength of the optical resonance. We monitored the change of these three parameters as a function of NO2 (0.5-5 ppm), ethanol (300-15000 ppm) and relative humidity (0-100%). Preliminary results confirm that the examined species affect the parameters in a different way, both as a relative change and as dynamic

Investigation of dopant profiles in nanosized materials by scanning transmission electron microscopy

Scanning electron microscopy is capable to provide chemical information on specimens interesting for the field of materials science and nanotechnology. The spatial resolution and the chemical information provided by incoherent imaging and detection of transmitted, forward-scattered electrons can reveal useful information about the specimen composition and microstructure. This paper discusses the capability and potential of low-voltage Scanning Transmission Electron Microscopy (STEM) for the characterization of multilayered structures and dopant profiles in crystalline materials

Real-Time Microwave, Dielectric, and Optical Sensing of Lincomycin and Tylosin Antibiotics in Water: Sensor Fusion for Environmental Safety

Antibiotics are widely used to prevent and treat bacterial infections in livestock animals, aquaculture, and humans. However, the unconditional use of those drugs as a growth promoter for livestock animals and the wrong usage as a treatment for infections in humans has led to high antibiotics pollution, especially in water resources. The elevated presence of antibiotics in water has resulted in the phenomenon known as the bacterial antibiotics resistance. To prevent ecological catastrophe, continuous realtime monitoring of water sources is necessary. The aim of this research work is to compare the abilities of three different techniques: novel electromagnetic wave spectroscopy, UV-Vis spectrophotometry, and capacitance sensing system for the realtime detection and quantification of antibiotics in water. Tylosin and lincomycin antibiotics were selected to the study, as both are regularly found in water sources. Two novel microwave sensor configurations were used: a planar sensor with interdigitated electrode pattern and a hairpin resonator sensor, as a means of real-time water analysis. Reflected S11 power signals were analyzed in GHz frequency range for microwave sensors. In parallel, UV-Vis spectrophotometry was used, where change in the optical absorbance was used as an indicator of water pollution, whereas change in the value of a capacitance in low frequency range has signalled the change in the dielectric properties of the solution. It was found that in all cases the changes in the measured parameters were dependent on both the type of antibiotic present in water and on its concentration. Fusion of all these techniques into a comprehensive sensing platform provides adequate real-time assessment of the water pollution with antibiotics and would allow adequate management of environment for safety and sustainable development. In particular, the lowest lincomycin samples’ concentration, 0.25 μg/l, was measured with a hairpin resonator sensor, while the lowest tylosin samples’ concentration, 0.20 μg/l, was measured with an IDE sensor. Since concentration in groundwater were 0.36 μg/l of lincomycin and 1.5 μg/l of tylosin, it is demonstrating a high-sensing platform utility

Defect study of SnO2 nanostructures by cathodoluminescence analysis: Application to nanowires

Defects in SnO2 nanowires have been studied by cathodoluminescence, and the obtained spectra have been compared with those measured on SnO2 nanocrystals of different sizes in order to reveal information about point defects not determined by other characterization techniques. Dependence of the luminescence bands on the thermal treatment temperatures and pre-treatment conditions have been determined pointing out their possible relation, due to the used treatment conditions, with the oxygen vacancy concentration. To explain these cathodoluminescence spectra and their behavior, a model based on first-principles calculations of the surface oxygen vacancies in the different crystallographic directions is proposed for corroborating the existence of surface state bands localized at energy values compatible with the found cathodoluminescence bands and with the gas sensing mechanisms. CL bands centered at 1.90 and 2.20 eV are attributed to the surface oxygen vacancies 100° coordinated with tin atoms, whereas CL bands centered at 2.37 and 2.75 eV are related to the surface oxygen vacancies 130° coordinated. This combined process of cathodoluminescence and ab initio calculations is shown to be a powerful tool for nanowire defect analysis