Highly sensitive ethanol sensors based on nanocrystalline SnO2 thin films

This paper reports on a simple and inexpensive ultrasonic spray pyrolysis method to synthesize agglomerate-free nanosized SnO₂ particles with a size smaller than 10 nm. Scanning electron microscopy, transmission electron microscopy and high resolution X-ray diffraction studies were used to characterize the morphology, crystallinity, and structure of the SnO₂ particles. Under the optimized experimental conditions, the prepared SnO₂ sensor shows the high response (S = 491) towards 100 ppm ethanol gas at 300 °C, linearity in the range of 100–500 ppm, quick response time (2 s), recovery time (60 s) and selectivity against other gases. The response of the sensor was monitored in a 250–450 °C temperature range. The seven fold enhancement in gas response and selective detection of C₂H₅OH in the presence of other gases such as CH₃OH and CH₃CHOHCH₃ are the significant points in this investigation. These results demonstrate that pure nanocrystalline SnO₂ thin film can be used as the sensing material for fabricating high performance ethanol sensors.     

Microdisplacement and microvibration sensors based on semiconductor lasers

Conclusion The above analysis of a microvibration sensor based on a semiconductor laser has shown that in the optimal operating regime one can expect a detection ability of 10^–2 nm.It is preferable to record an optical signal (change of radiation power) than an optoelectronic one (change diode voltage).Several sensor variants were constructed: with an ILPN-202 commercial laser diode, with a laser cartridge, and with the LMF-1300 single-mode laser module. Since real sensors contain additional noise sources (pumping- and recording-system noise, fluctuations due to parasitic reflection, etc.), the sensitivity limit could not be reached. The detection ability ranges, depending on the scheme employed, from fraction of a nanometer to several nanometers, but is perfectly acceptable for many practical applications.Translation of Preprint No. 42 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1991.     

UV photodetector based on polycrystalline SnO2 nanotubes by electrospinning with enhanced performance

Journal of Nanoparticle Research - Measurement of light scattered from suspensions of monodisperse nanoparticles in solution (“turbidity”) long has been used to derive their size....     

Dependence of the selectivity of SnO2 nanorod gas sensors on functionalization materials

Effects of functionalization materials on the selectivity of SnO₂ nanorod gas sensors were examined by comparing the responses of SnO₂ one-dimensional nanostructures functionalized with CuO and Pd to ethanol and H₂S gases. The response of pristine SnO₂ nanorods to 500 ppm ethanol was similar to 100 ppm H₂S. CuO-functionalized SnO₂ nanorods showed a slightly stronger response to 100 ppm H₂S than to 500 ppm ethanol. In contrast, Pd-functionalized SnO₂ nanorods showed a considerably stronger response to 500 ppm ethanol than to 100 ppm H₂S. In other words, the H₂S selectivity of SnO₂ nanorods over ethanol is enhanced by functionalization with CuO, whereas the ethanol selectivity of SnO₂ nanorods over H₂S is enhanced by functionalization with Pd. This result shows that the selectivity of SnO₂ nanorods depends strongly on the functionalization material. The ethanol and H₂S gas sensing mechanisms of CuO- and Pd-functionalized SnO₂ nanorods are also discussed.     

Electrochemical performance of SnO2 hexagonal nanoplates

This study reports the electrochemical performance of SnO₂ hexagonal nanoplates (SnO₂-NPs) coated on copper substrate by electrodeposition method in different aqueous electrolytes. The influence of deposition voltage on the morphology of the nanoplates was investigated by scanning electron microscopy. The synthesized SnO₂ was characterized using SEM, X-ray diffraction, Raman, FTIR and UV–visible absorption spectrum. The results clearly have shown that with the increase in deposition voltage at constant deposition time, the thickness of the plate decreased. The obtained nanoplates were of several hundred nanometers in planar dimension and about 50-300 nm in thickness. The electrochemical reaction of SnO₂-NPs with lithium ions were investigated by cyclic voltammetry in LiOH·H₂O, Li₂CO₃, LiNO₃ and Li₂SO₄ aqueous solution. The SnO₂ hexagonal nanoplates deposited on copper substrate can be an ideal anode material for aqueous rechargeable lithium-ion battery.     

Spectral and static noise characteristics of semiconductor gas sensors in equiresistance conditions

The extent to which the resistance fluctuations in semiconductor gas sensors can be considered stationary and Gaussian, as well as the noise spectrum of these sensors in equiresistance conditions, are studied. It is shown that the extent to which the noise is stationary and Gaussian depends on gas phase composition. It is found that the spectrum of the sensor noise is qualitatively distinct in different media. On the basis of these results, it is concluded that it is possible in principle to increase the selectivity of the gas sensors by combined measurements of their resistive and noise characteristics.     

基于多芯片封装的半导体激光器热特性

设计了一种由12只单条形芯片分为2组以从高到低阶梯排列的百瓦级半导体激光器结构。针对其在稳态工作条件下的热特性利用ANSYS软件进行了模拟分析,通过改变Cu热沉的宽度、间距和高度差,得到了最高和最低Cu热沉封装的芯片有源区温度及两者温度差值的变化规律。最后设计了一种较为理想的百W级半导体激光器的散热结构。     

Improving precursor adsorption characteristics in ATR-FTIR spectroscopy with a ZrO2 nanoparticle coating

Journal of Nanoparticle Research - Transparent superhydrophobic coatings, which are highly desired for the protection of material surfaces, have been limited to particular kinds of materials, e.g....     

Room temperature response of SnO2-electrode modified solid state electrochemical CO2 sensors

A thin film solid state electrochemical gas sensor has been investigated for CO₂ detection based on the cell reaction: Na⁺+OH+CO₂=NaHCO₃. The galvanic cell arrangement is Au | Na_xCoO_2−δ (ref.) | NASICON | Au, SnO₂ where the right hand electrode is in contact with CO₂ and O₂ in a humid atmosphere. The response has been compared to results obtained with a conventional pellet type sensor. Furthermore, both devices have been exposed to CO and humidity. Strong cross-sensitivities were observed leading to large changes in the emf in both cases. The response to moisture is reversible and fast with a response time of about 1 min according to a fast surface reaction of H₂O with SnO₂. The presence of CO leads to a signal change with a high response time and a very slow reverse reaction. However, the response to CO₂ is not influenced by the presence of CO or H₂O with regard to the signal height and response time. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

基于多芯片封装的半导体激光器热特性

设计了一种由12只单条形芯片分为2组以从高到低阶梯排列的百瓦级半导体激光器结构。针对其在稳态工作条件下的热特性利用ANSYS软件进行了模拟分析,通过改变Cu热沉的宽度、间距和高度差,得到了最高和最低Cu热沉封装的芯片有源区温度及两者温度差值的变化规律。最后设计了一种较为理想的百W级半导体激光器的散热结构。     

The infrared vibration characteristics of SnO2 nanoparticles

The infrared vibration characteristics of SnO₂ nanoparticles with different sizes were studied using the infrared spectra. The Fröhlich modes were observed in experiments and compared with the theoretical values. The influence of phonon localization resulting from quantum size effects on the infrared spectra of SnO₂ nanoparticles is discussed.     

基于大功率激光二极管的光导开关导通特性

研究了应用于介质壁加速器的小间隙光导开关在大功率激光二极管驱动下的导通特性。激光二极管产生的激光脉冲中心波长为905nm,脉冲宽度(FWHM)约20ns,前沿约3.1ns,抖动小于200ps,峰值功率约90W。所用光导开关为异面电极结构的砷化镓(GaAs)光导开关,电极间隙5mm,偏置电压为15~22kV脉冲高压,工作在非线性(高增益)模式。测得光导开关最小导通电阻4.1Ω,抖动小于1ns,偏置电压在18kV时平均使用寿命约200次。     

Effect of Er3+ doping in SnO2 semiconductor nanoparticles synthesized by solgel technique

Pure and Er³⁺ doped SnO₂ semiconductor nanoparticles have been synthesized by solgel technique. The X-ray diffraction patterns show peaks corresponding to tetragonal structure of SnO₂. No Er related impurity peaks could be observed. From the TEM micrographs average crystallite size was estimated to be 12 nm. The UV–visible absorption spectra of SnO₂:Er showed blue shift in the absorption shoulder compared with the spectra of undoped SnO₂ sample. Photoluminescence emission intensity of SnO₂:Er nanoparticles was found to be quenched with increasing concentration of Er³⁺ ions. The electron spin resonance (ESR) analysis of Er doped SnO₂ nanoparticles indicated Er in 3 + state with g = 2.     

基于大功率激光二极管的光导开关导通特性

研究了应用于介质壁加速器的小间隙光导开关在大功率激光二极管驱动下的导通特性。激光二极管产生的激光脉冲中心波长为905 nm, 脉冲宽度（FWHM）约20 ns, 前沿约3.1 ns, 抖动小于200 ps, 峰值功率约90 W。所用光导开关为异面电极结构的砷化镓（GaAs）光导开关, 电极间隙5 mm, 偏置电压为15～22 kV脉冲高压, 工作在非线性（高增益）模式。测得光导开关最小导通电阻4.1 , 抖动小于1 ns, 偏置电压在18 kV时平均使用寿命约200次。     

Preparation and characterization of SiO2 nanowires using a SnO2 catalyst

SiO₂ nanowires have been successfully synthesized on the surface of the silicon substrate via a thermal evaporation method using SnO₂ powders as the catalysts. The final synthesized product was systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), and electron energy dispersive X-ray (EDX), UV-Visible absorption and photoluminescence (PL) spectroscopy. The results reveal that in the reaction and growth process, the real catalytic effect is Sn and SnO_x, and the growth of SiO₂ nanowire is most likely controlled by VLS mechanism. The PL spectral results indicate the obtained products have a stable yellow-green emission range. The products have improved performance and can be used in optoelectronic semiconductor devices.     

Improving signal-to-noise ratio performance of compressive imaging based on spatial correlation

In this paper, compressive imaging based on spatial correlation (CISC), which uses second-order correlation with the measurement matrix, is introduced to improve the signal-to-noise ratio performance of compressive imaging (CI). Numerical simulations and experiments are performed as well. Referred to the results, it can be seen that CISC performs much better than CI in three common noise environments. This provides the great opportunity to pave the way for real applications.     

基于第一性原理计算Mn掺杂MoS2对油中溶解气体的吸附性能

CO、C₂H₂、CH₄是溶解在变压器油中的典型故障特征气体,其种类和浓度能够反映油浸式变压器绝缘故障的不同类型和严重程度,进行油中溶解气体分析是在线检测变压器运行状态的重要方法.基于第一性原理,通过Mn-MoS₂单层对三种气体的吸附能、转移电荷、态密度和形变电荷密度等参数以及解吸性能分析和灵敏度计算,提出了一种基于Mn-MoS₂材料的气敏传感器对油中溶解气体进行分析的方法.结果表明Mn-MoS₂对CH₄是物理吸附,对CO和C₂H₂是化学吸附.对于Mn-MoS₂来说,CH₄在常温下吸附能力差且灵敏度低,CO在不同温度下均有较强的吸附能力,而C₂H₂在常温下吸附稳定,高温下易解吸且响应灵敏度高.因此,Mn掺杂的MoS₂体系可预期作为CO的气体吸附剂和检测C₂H     

Tests of quantum mechanics based on interference of photons

Some difficulties with a modified version of the Pfleegor-Mandel experiment recently proposed by Garuccio, Popper and Vigier are pointed out, and a different modification is proposed in order to test the conventional quantum mechanical interpretation.     

Low-threshold performance of fiber Bragg grating external-cavity semiconductor lasers using genetic algorithms

The lowest threshold current of the external-cavity semiconductor laser with fiber Bragg grating using genetic algorithms is investigated. Effects of the external cavity length, coupling efficiency and anti-reflection coating reflectivity on static characteristics, such as L-I curves and side mode suppression ratios (SMSR) are investigated by using multi-mode rate equation. It is found that the reflectivity of the anti-reflection coating for low-threshold performance needs to be increased at the cost of the stability of the fiber grating external-cavity semiconductor laser. The optimal external cavity length obtained by genetic algorithms can be used to obtain the lowest threshold current for sacrificing a little SMSR. However, with the decrease of AR-coating reflectivity, output powers and SMSRs are slightly dependent on the external cavity length.