Room temperature Cl(2) sensing using thick nanoporous films of Sb-doped SnO(2)

Thick film resistive Cl(2) sensors were fabricated using SnO(2) doped with Sb. The nanocrystalline powders of Sb-doped SnO(2) synthesized by a sol-gel method were compressed into an 800?μm thick pellet. The fabricated sensors were tested against gases like Cl(2), Br(2), HCl, NO, NO(2), CHCl(3), NH(3) and H(2). The highest response to Cl(2) was achieved in 0.1% Sb doping where an exposure to 3?ppm of Cl(2) gas led to a 500-fold increase in device resistance. The high sensitivity to Cl(2) is accompanied by minor interference due to other gases at room temperature. It was found that the SnO(2) doped with 0.1% Sb exhibited high response, selectivity (>100 in comparison to the gases described above) and short response time (～60?s) to Cl(2) at 3?ppm level at room temperature.     

无机溶胶-凝胶法制备B型和M型VO2粉体

以V2P5为原料,采用无机溶胶-凝胶法制备出V2O5粉体,在H2气氛下热处理得到了VO2(B)粉体,再在Ar气氛下热处理VO2(B)粉体,制备出了VO2(M)粉体.采用X射线衍射(XRD)、红外吸收光谱(IR)、差热分析(DTA)等方法对样品进行了成分和结构分析,结果表明,当热处理温度为500℃、H2浓度50%时,得到VO2(B)粉体;然后,在Ar气氛下分别经过550、600、650、700℃处理1h后,VO2由B型向M型转变,700℃处理成功制备出了VO2(M)粉体.     

Hydrothermal synthesis of single-crystal VO2(B) nanobelts

Single crystalline VO₂(B) nanobelts with a metastable structure were obtained through a simple hydrothermal synthetic method. The VO₂(B) nanobelts were characterized by means of X-ray diffraction, transmission electron microscopy, selected area electronic diffraction, field-emission scanning electron microscopy and X-ray energy-dispersive spectroscopy techniques. The as-obtained VO₂(B) nanobelts are 400–600 nm long, typically 100–150 nm wide and 20–30 nm thick. The belt-like VO₂(B) with a high surface area may be beneficial to lithium insertion between the VO₆ layers for application in batteries.     

Room temperature CO and H2 sensing with carbon nanoparticles

We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.     

Room temperature H2S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) thick films

The study reports H₂S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) films. The porous alumina (PoAl) thick layers were formed in the dark on aluminum substrates using an electrochemical anodization method. Thin semitransparent platinum (Pt) films were deposited on PoAl samples using chemical bath deposition (CBD) method. The films were characterized using energy dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM). The thicknesses of coated and bare films were measured using ellipsometry. The sensing properties such as sensitivity factor (S.F.), response time, recovery time and repeatability were measured using a static gas sensing system for H₂S gas. The EDAX studies confirmed the purity of Pt–PoAl film and indicated the formation of pure platinum (Pt) phase. The ellipsometry studies revealed the thickness of PoAl layer of about 15–17 μm on aluminum substrates. The SEM studies demonstrated uniform distribution of spherical pores with a size between 0.250 and 0.500 μm for PoAl film and nearly spherical platinum particles with average particle size ∼100 nm for Pt–PoAl film. The gas-sensing properties of these samples were studied in a home-built static gas characterization system. The H₂S gas sensing properties of Pt–PoAl at 1000 ppm of H₂S gave maximum sensitivity factor (S.F.) = 1200. The response time and recovery time were found to be 2–3 min and ∼1 min respectively. Further, the measurement of H₂S gas sensing properties clearly indicated the repeatability of gas sensing response of Pt–PoAl film. The present study indicated the significant potential of Pt coated PoAl films for H₂S gas sensing applications in diverse areas.     

Gas sensor based on rGO/ZnO aerogel for efficient detection of NO2 at room temperature

Journal of Materials Science: Materials in Electronics - In this paper, a simple, low cost and easy to operate hydrothermal method was successfully used to synthesize rGO/ZnO aerogel in one step....     

二氧化钒超薄纳米片的制备及其光学性能研究

采用V2O5作为钒源,以乙二醇(EG))为还原剂,在190℃的条件下,通过简单的水热途径制备出了VO2 (B)超薄纳米片晶.并利用X射线衍射(XRD)、扫描电镜(SEM)、荧光分光光度计(PL)对样品的结构、形貌及荧光性能进行表征.研究结果表明:以乙二醇(EG)为还原剂制备出的晶体为纳米VO2 (B),长180～350...     

Hydrothermal synthesis of W and Mo co-doped VO2(B) nanobelts

W and Mo co-doped VO₂(B) nanobelts which used formic acid as reduction acid, NH₄VO₃ as vanadium source, (NH₄)₆W₇O₂₄?·?6H₂O and (NH₄)₆Mo₇O₂₄?·?4H₂O as doped sources were synthesised by the hydrothermal method. The samples were characterised by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). TEM and HRTEM images showed the samples had a length of 1?µm and a width of 100?nm. XRD, FTIR and XPS spectra revealed that Mo⁶⁺ and W⁶⁺ incorporated into the VO₂(B) lattice and formed solid-solution phases with VO₂(B).     

室温下金属有机骨架材料Cu3（BTC）2的合成与表征?

通过将配体均苯三甲酸 H 3 BTC 转化为均苯三甲酸钾,在室温条件下快速获得了金属有机骨架材料中的经典化合物 Cu3(BTC)2(HKUST-1),并通过SEM跟踪了晶体的生长过程。粉末 XRD 测试结果表明化合物为纯相,并具有较高结晶度,TGA 测试结果表明产物可稳定存在至300℃,N2吸附测试显示出产物具有高的比表面积及孔容积。研究工作为Cu3(BTC)2这一重要化合物提供了一条简便及低能耗的合成方法。     

Fabrication of single- and multilayer MoS2 film-based field-effect transistors for sensing NO at room temperature

Single- and multilayer MoS(2) films are deposited onto Si/SiO(2) using the mechanical exfoliation technique. The films were then used for the fabrication of field-effect transistors (FETs). These FET devices can be used as gas sensors to detect nitrous oxide (NO). Although the single-layer MoS(2) device shows a rapid response after exposure to NO, the current was found to be unstable. The two-, three-, and four-layer MoS(2) devices show both stable and sensitive responses to NO down to a concentration of 0.8 ppm.     

Room temperature tensile ductility in polycrystalline B2 Ni-30Al-20Fe

This paper reports the observation of room temperature tensile elongation (∼2.5%) in B2 Ni30Al20Fe where the only slip vector observed was <100>. These results suggest that <100> slip does not preclude limited ductility of polycrystalline B2 alloys in tension at low temperatures.     

Effect of reduced graphene oxide (rGO) on structural,optical, and dielectric properties of Mg(OH)2/rGO nanocomposites

In this paper, we report the synthesis of Mg(OH)₂ NPs and Mg(OH)₂–rGO nanocomposites (NCs) by microwave assisted co-precipitation method. The crystal phase, structural morphology and functional groups of the as-synthesized samples were analyzed by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). Raman spectroscopy was used to study the defects in the samples. Raman spectroscopy and the SEM results validate the growth of Mg(OH)₂ NPs on the rGO nanosheets. The chemical composition of the prepared samples was analyzed by EDAX. Optical properties of the as-synthesized samples were studied by UV–visible spectroscopy and the energy band gap was calculated by Tauc relation which shows a decrease in band gap with an increase in the amount of Graphene Oxide (GO) in the NCs. The dielectric properties were studied as a function of frequency over a range of 50 Hz to 5 MHz at room temperature. The value of dielectric constant decreases with an increase in frequency, this could be due to the existence of a polarization process at the border of the rGO sheets and Mg(OH)₂ NPs. The value of dielectric loss shows a decreasing trend with an increase in frequency whereas the larger value of AC conductivity in Mg(OH)₂–rGO NCs as compared to Mg(OH)₂ NPs approves the restoration of sp² network in the graphene sheets.     

Room temperature solid-state synthesis and ethanol sensing properties of sea-urchin-like ZnO nanostructures

ZnO gas-sensing materials were prepared by one-step solid-state reaction at room temperature. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize the hierarchal ZnO nanocrystals. The results indicate that ZnO clusters are assembled with nanosheets when no surface-active agent is present. When surface-active agent PEG-10000 was added, sea-urchin-like ZnO are assembled from ZnO nodules. The rods have an average diameter of 33 nm and length of about 100 nm. The primary gas-sensing results show that sea-urchin-like ZnO have good gas sensitivity to ethanol vapor.     

Hydrothermally synthesized ZnO and Z-rGO nanorods: Effect of post-annealing temperature and rGO incorporation on hydrogen sensing

Journal of Materials Science: Materials in Electronics - In this work, hydrogen-sensing characteristics of zinc oxide nanorods and reduced graphene oxide-incorporated zinc oxide nanorods are...     

Room temperature magnetic properties of Cu-doped titanate, TiO2(B) and anatase nanorods synthesized by hydrothermal method

The Cu-doped hydrogen titanate nanorods are synthesized via a hydrothermal reaction and converted into Cu-doped TiO₂(B) and anatase phases by calcinations. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and selected area electron diffraction (SAED) pattern do not show the presence of any other phases and thus confirmed the intrinsic ferromagnetic behavior rather than it arising from metallic clusters. The blue shifting in absorption edge and increase in photoluminescence (PL) intensity from Cu-doped hydrogen titanate to anatase phase are strongly correlated with concentration of oxygen vacancies and defect formation. The higher concentration of oxygen vacancies and/or structural defects leads to the coalescence of ferromagnetic domains, which corroborates to the observed higher magnetization value of Cu-doped anatase phase compared to other phases.     

Room temperature photoluminescence studies of nitrided InP(100) surfaces

The evolution of thin InN overlayer grown on InP (100) rich In substrate was investigated at room temperature by photoluminescence method versus the duration of nitridation process. The main important parameters were the duration of the process, and the angle of the reactive nitrogen flow. The nitridation was performed by a glow discharge source (GDS). The correlations between the electronic properties, gathered from photoluminescence (PL) measurements, and the chemical composition of InN–InP interfaces, derived from Auger electron spectroscopy (AES) were found. AES revealed that the nitridation process proceeds quickly in time showing self-limiting behavior. It is more effective for grazing nitrogen flux. The interface state density distributions, N_SS(E), were determined via advanced computer-aided analysis of dependencies of band edge PL efficiency, Y_PL, versus excitation light intensity, Φ. The analysis showed that the substrates were well passivated with N_SS(E) minima on the order of 5·10¹¹ cm^− 2 eV^− 1_. The nitrogen flux angle during the nitridation was found to have an influence on Y_PL(Φ) spectra. In all analyzed cases the grazing nitrogen flux generated the interface with slightly improved N_SS(E) distribution. Finally, the behavior of Y_PL versus Φ and N_SS(E) was precisely examined.     

NO2 and humidity sensing characteristics of few-layer graphenes

Sensing characteristics of few-layer graphenes for NO₂ and humidity have been investigated with graphene samples prepared by the thermal exfoliation of graphitic oxide, conversion of nanodiamond (DG) and arc-discharge of graphite in hydrogen (HG). The sensitivity for NO₂ is found to be highest with DG. Nitrogen-doped HG (n-type) shows increased sensitivity for NO₂ compared with pure HG. The highest sensitivity for humidity is observed with HG. Sensing characteristics of graphene have been examined for different aliphatic alcohols and the sensitivity is found to vary with the chain length and branching.