Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Sensing (gas + sensing)
Selected AbstractsLarge-Scale Synthesis of Long Crystalline Cu2-xSe Nanowire Bundles by Water-Evaporation-Induced Self-Assembly and Their Application in Gas SensingADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Jun Xu Abstract By a facile water evaporation process without adding any directing agent, Cu2-xSe nanowire bundles with diameters of 100,300,nm and lengths up to hundreds of micrometers, which comprise crystalline nanowires with diameters of 5,8,nm, are obtained. Experiments reveal the initial formation/stacking of CuSe nanoplates and the subsequent transformation to the Cu2-xSe nanowire bundles. A water-evaporation-induced self-assembly (WEISA) mechanism is proposed, which highlights the driving force of evaporation in promoting the nanoplate stacking, CuSe-to-Cu2-xSe transformation and the growth/bundling of the Cu2-xSe nanowires. The simplicity, benignancy, scalability, and high-yield of the synthesis of this important nanowire material herald its numerous applications. As one example, the use of the Cu2-xSe nanowire bundles as a photoluminescence-type sensor of humidity is demonstrated, which shows good sensitivity, ideal linearity, quick response/recovery and long lifetime in a very wide humidity range at room temperature. [source] Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub-Micrometer FibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jeremy M. Rathfon Abstract The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro-Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub-micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices. [source] Synthesis of Indium and Indium Oxide Nanoparticles from Indium Cyclopentadienyl Precursor and Their Application for Gas Sensing,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2003K. Soulantica Abstract Decomposition of the organometallic precursor [In(,5 -C5H5)] in toluene in the presence of methanol (8 vol.-%) at room temperature leads to the immediate formation of aggregates of indium nanoparticles of 15,±,2 nm mean diameter. The aggregates are roughly spherical with a mean size of 400,±,40 nm. The particles were characterized by means of transmission electron and high-resolution transmission electron microscopies (TEM and HRTEM), and X-ray diffraction (XRD) studies indicate that the powder consists of the tetragonal phase of indium. The thermal oxidation in air of these nanoparticles yields well-crystallized nanoparticles of In2O3 with unchanged morphology (aggregates of nanoparticles of 16.6,±,2 nm mean diameter with aggregate mean size of 400,±,40 nm) and without any sign of coalescence. XRD pattern shows that the powder consists of the cubic phase of In2O3. The electrical conductivity measurements demonstrate that this material is highly sensitive to an oxidizing gas such as nitrogen dioxide and barely sensitive to a reducing gas such as carbon monoxide. Its association with SnO2 -based sensors allows the selective detection of carbon monoxide (30 ppm) and sub-ppm amounts of nitrogen dioxide (400 ppb) in a mixture at 21,°C and at a relative humidity of 60,%. [source] Gas Sensors: Room-Temperature Gas Sensing Based on Electron Transfer between Discrete Tin Oxide Nanocrystals and Multiwalled Carbon Nanotubes (Adv. Mater.ADVANCED MATERIALS, Issue 24 200924/2009) Hybrid nanostructures consisting of multiwalled carbon nanotubes (CNTs) uniformly coated with SnO2 nanocrystals can be used as a novel gas sensing platform, exhibiting high sensitivity to low-concentration gases (NO2, H2, and CO) at room temperature, report Junhong Chen and co-workers on p. 2487. The hybrid nanomaterial provides a new opportunity to engineer sensing devices through electronic transfer between the nanocrystals and the CNT. [source] Soft Langmuir,Blodgett Technique for Hard NanomaterialsADVANCED MATERIALS, Issue 29 2009Somobrata Acharya Abstract Materials and their assemblies of dimensions down to a few nanometers have attracted considerable scientific interest in physical, chemical, and biological sciences because of unique properties not available in their bulk counterparts. The Langmuir,Blodgett (LB) technique allows rigid nanomaterials to be aligned in particular structures through a flexible assembly process at liquid interfaces. In this review, we summarize the development of assembly of hard nanomaterials using soft LB techniques. An initial summary of the basic features of nanomaterials will include dimension-related effects, synthesis, characterization, and analysis, and will be followed by examples of LB assemblies of nanomaterials described according to their morphology: nanoparticles, nanorods, nanowires, nanotubes, and nanosheets. Some of the nanomaterials have been fabricated in orientation-controlled morphologies, and have been incorporated into prototype devices for gas sensing and photocurrent transport. In the final part of this review, the challenges remaining for LB techniques of hard nanomaterials will be overviewed, and will include a comparison with the widely-used LB technique involving soft materials. [source] FIB fabrication of ZnO nanotetrapod and cross-sensorPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010Lee Chow Abstract This article presents the fabrication of zinc oxide (ZnO) nanotetrapod and cross-nanorods-based sensors. This low-dimensional device is made in a focused ion beam set-up by using nanodeposition for metal electrodes. The gas response of the sensor based on an individual zinc oxide nanotetrapod and on crossed ZnO nanorod for detection of ultraviolet (UV) light and hydrogen at room temperature is presented. It is shown that ZnO tetrapod has potential application as UV and as chemical sensor with multi-terminal construction. The chemisorbed gas molecules on the ZnO surface can extract or donate electrons to ZnO and this effect was used to monitor the electrical resistance values change of the tetrapod sensor. ZnO tetrapod sensor demonstrates sensitivity and selectivity in resistance upon exposure to UV light, H2, O2, NH3, CO, CO2, and LPG gas. The resistivity change is different for UV and for H2 gas sensing. The presented ZnO sensor proves to be promising for application in various processes. [source] Titanium dioxide thin films deposited by the sol-gel technique starting from titanium oxy-acetyl acetonate: gas sensing and photocatalyst applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2010A. Maldonado Abstract Titanium dioxide (TiO2) thin films were deposited onto sodocalcic glass plates by the sol-gel technique, starting from a non-alkoxide route, namely, titanium oxy-acetyl acetonate as Ti precursor. Film thickness effect on both the gas sensing and photocatalytic degradation performance was studied. The as-deposited films were annealed in air at 400 °C. All the X-ray spectra of the films show a very broad-peak centered in a 2, angle around 30°. In the case of the thinnest films the surface morphology is uniform and very smooth, whereas for the thickest films the corresponding surface is covered by grains with a rod-like shape with a length on the order of 140 nm. The films were tested both for two straightforward applications: ultraviolet assisted-degradation of methylene blue dissolved in water, at different times, as well as gas sensor in a controlled propane (C3H8) atmosphere. As the film thickness increases, the degradation of methylene blue (MB) also increases. The thickest TiO2 thin films after being exposed by 5 hours to the catalytic degradation, promoted by ultraviolet illumination, showed a final MB solution degradation in the order of 48%. This reult can be associated with the increase in the effective exposed area of the TiO2 thin films. On the other hand, the exposition of the films to a controlled propane atmosphere produced a significant change in the surface electrical resistance of the films at operating temperatures of 200 °C and above. In fact, in the case of the thickest TiO2 films, a dramatic electrical resistance change of non-exposed and propane exposed , 560 to 0.7 M, ,, was registered. The results show that TiO2 films deposited by an economical deposition technique, as is the case of the sol-gel technique, could have an important potential in industrial applications. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||