激光诱导碳纳米管制备石墨烯纳米带及其电学性能分析

通过将纳米管解压缩可以很容易地生产石墨烯纳米带,因为碳纳米管结构可以被认为是卷起的石墨烯筒。这是一种特殊的2D石墨结构,具有出色的性能。应用领域广泛,包括晶体管、光学和微波通信设备、生物传感器、化学传感器、电子存储和处理设备以及纳米机电系统和复合材料。通过扫描电子显微镜（SEM）观察薄膜的形貌,通过拉曼光谱法表征石墨烯的性质,并通过半导体参数测量系统测量薄膜的电导率。拉曼光谱表明,通过优化工艺可以增强石墨烯的拉曼特性。碳纳米管制备石墨烯带的两个重要参数是激光能量密度和辐照时间。在这项研究中,通过准分子激光辐照碳纳米管薄膜来生产石墨烯纳米带。实验结果表明,在150 mJ的激光能量下,观察到连接时碳纳米管没有打开。在450 mJ的能量下,可以有效地破坏碳纳米管,并且使其部分地形成石墨烯带。此时,膜的电导率达到最大值。由于蓄热作用,在碳纳米管壁上出现大量的多孔结构。     

纳米银线/还原石墨烯复合材料的制备与表征

用改进的Hummer法制备了氧化石墨烯(GD),并制备 了表面用聚乙烯吡咯烷酮修饰的纳米银线(AgNWs), 通过原位还原法将二者复合成一种新型的水溶性AgNWs/还原石墨烯(RGD)材料,克服了石 墨烯材料不易分散 的缺点。用X射线衍射(XRD)、紫外-可见分光(UV-vis)光度计、扫描电子显 微镜(SEM)和傅里 叶变换红外(FT-IR)光谱分析仪对样品结构和形貌进行了表征。结果表明,制备的AgNWs/RG D材料具有与前驱 体不同的物理参数,有望在非线性光学、光电传感器和生物抑菌等方面有良 好的表现。     

修饰银纳米粒子的石墨烯泡沫镍衬底制备及其SERS活性研究

为了解决表面增强拉曼散射(SERS)衬底的吸附性差、稳定性低以及灵敏度不高的问题,设计了一种沉积银纳米粒子的石墨烯泡沫镍SERS衬底,并进行了实验研究.利用化学气相沉积法在泡沫镍衬底上生长石墨烯,并通过溶液沉积的方法将合成的银纳米粒子沉积在石墨烯泡沫镍衬底表面,烘干后制备成石墨烯泡沫镍修饰银纳米粒子的新型SERS衬底.采用罗丹明6G(R6G)对SERS衬底进行拉曼实验研究,结果表明石墨烯能够较好地淬灭SERS衬底的背景荧光;泡沫镍的独特三维结构能够增大衬底对检测分子的吸附;同时,银纳米粒子也可大幅增强衬底的SERS活性.而修饰了银纳米粒子的石墨烯泡沫镍新型衬底同时具有以上优异特性,是一种具有很大应用潜力的新型SERS衬底.     

α-Ni(OH)2/石墨烯纳米复合材料的制备及其电容性能研究

近年来,石墨烯复合材料作为理想基底用于电极材料的生长,在电化学的许多领域都得到了广泛的应用。以石墨烯和六水合硝酸镍为原料,用NaBH_4作为还原剂,在90℃低温条件下制备合成了具有纳米尺寸的α-Ni(OH)_2/石墨烯复合材料。研究了石墨烯与α-Ni(OH)_2的质量比不同时复合材料的电化学性能。结果表明:当质量比为5∶5时,复合材料显示了最佳的电化学性能:在0～0.47 V的电位窗口,0.2 A/g的电流密度下,比容量高达1280 F/g;2 A/g的电流密度下循环充放电测试2000次后,比容量仍然保持88%。因此,该复合材料作为一种理想的复合电极材料,可被应用到能量转化/储存系统中。     

石墨烯与Ag纳米颗粒复合材料的制备与表征

采用液相混合与水热还原相结合的方法制备了一种颗粒直径在10~20 nm之间,分布均匀的石墨烯与Ag纳米颗粒复合材料。利用透射电子显微技术研究在不同反应阶段时石墨烯或氧化石墨烯表面颗粒的晶格结构与组成成分。研究结果表明,在液相混合阶段Ag+与氧化石墨烯之间发生了氧化还原反应,Ag+还原成为Ag纳米颗粒并附着于氧化石墨烯的表面,颗粒的直径在5 nm以下,分布均一;在水热还原氧化石墨烯阶段,Ag纳米颗粒发生了奥斯瓦尔德熟化现象,较小的Ag纳米颗粒随着水热反应的进行不断的溶解,并在较大的Ag颗粒表面凝聚,使得颗粒的尺寸增加。     

低温氧等离子体处理对单层石墨烯微观结构影响的研究

运用低温氧等离子体对化学气相沉积法生长的单层石墨烯进行处理,通过拉曼光谱仪和X射线光电子能谱仪来表征处理前后的变化,重点探讨了低温氧等离子体处理对单层石墨烯微观结构的影响。在拉曼光谱中,处理后的石墨烯出现了明显的D峰和D′峰,同时G峰和2D峰也出现了明显的退化,而G峰峰位右移,2D峰峰位左移。通过X射线光电子能谱表征,表明处理后向石墨烯中引入了较多的官能团。利用原子力显微镜研究了处理前后SiO_2/Si基底上石墨烯的表面形貌,发现低温氧等离子体处理后石墨烯表面高度明显增加,同时褶皱减少。     

空心SnO_2@G复合材料的结构表征及其储锂性能研究

本文采用简易湿化学法制备石墨烯包裹的空心二氧化锡复合材料(SnO_2@G)。利用X射线衍射仪(XRD)和透射电子显微镜(TEM)手段表征其形貌、成分及微观结构,并测试其锂离子电池负极性能。结果表明空心SnO_2纳米颗粒尺寸约为300~400 nm,且均匀包裹在石墨烯里面,锂电性能测试结果显示复合材料与纯SnO_2有着良好的循环性能、较高的比容量和良好的倍率性能。     

单层石墨烯在空气中的热稳定性研究

采用化学气相沉积方法制备了高质量的大面积单层石墨烯,利用拉曼光谱、X射线光电子能谱和原子力显微镜对在空气中热处理前后的石墨烯进行了表征,研究了单层石墨烯在空气中的热稳定性。结果表明,在空气中热处理后,石墨烯的缺陷明显增加,晶粒发生细化,其主要是由于热处理后石墨烯会发生轻微的氧化,表面形成C O及C—OH键。另外,由于石墨烯与衬底的结合形态有所变化,使得热处理后石墨烯表面更趋平整。     

氧化石墨烯/碳纤维复合材料的制备及表征

采用改进的Hummers法制备氧化石墨,经后处理得到氧化石墨烯(GO)悬浮液,再将涂覆了环氧树脂(EP)的碳纤维(CF)布在不同浓度的GO溶液中浸渍,经不同温度(60℃和120℃)真空退火,得到GO/EP/CF复合材料,并分析了复合材料的结构、形貌、导电性和拉伸性能。结果表明,与基底碳纤维布相比,低温改性处理的复合材料具有更优的综合性能。     

Nitrogen dioxide (NO2) sensing performance of p-polypyrrole/n-tungsten oxide hybrid nanocomposites at room temperature

Polypyrrole (PPy)–tungsten oxide (WO₃) hybrid nanocomposite have been successfully synthesized using different weight percentages of tungsten oxide (10–50%) dispersed in polypyrrole matrix by solid state synthesis method. The sensor based on PPy–WO₃ was fabricated on glass substrate using cost effective spin coating method for detection of NO₂ gas in the low concentration range of 5–100 ppm. The gas sensing performance of hybrid material was studied and compared with those of pure PPy and WO₃. It was found that PPy–WO₃ hybrid nanocomposite sensor can complement the drawbacks of pure PPy and WO₃. The structure, morphology and surface composition properties of PPy–WO₃ hybrid nanocomposites were employed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The presence of WO₃ in PPy matrix and their interaction was confirmed using XRD, FTIR techniques. The porous surface morphology was observed with addition of WO₃ in PPy matrix which is useful morphology for gas sensing applications. TEM image of PPy–WO₃ hybrid nanocomposites shows the average diameter of 80–90 nm. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of nanocomposites. It was observed that 50% WO₃ loaded PPy sensor operating at room temperature exhibit maximum response of 61% towards 100 ppm of NO₂ gas and able to detect low concentration of 5 ppm NO₂ gas with reasonable response of 8%. The hybrid sensor shows better sensitivity, selectivity, reproducibility and stability compared to pure PPy and WO₃. The proposed sensing mechanism of hybrid nanocomposite in presence of air and NO₂ atmosphere was discussed with the help of energy band diagram. Furthermore, the interaction of NO₂ gas with PPy–WO₃ hybrid nanocomposites sensor was studied by cole–cole plot using impedance spectroscopy.     

Enhanced ammonia sensing characteristics of tungsten oxide decorated polyaniline hybrid nanocomposites

Polyaniline (PAni)-tungsten oxide (WO₃) hybrid nanocomposites sensor have been lucratively synthesized by in-situ chemical oxidative polymerization method by entrapping tungsten oxide nanoparticles (10–50%) in the polyaniline matrix on precleaned glass substrate. The structural, morphological and surface composition elucidation of PAni-WO₃ hybrid nanocomposites were explored by X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The existence of WO₃ in PAni matrix and interaction between them was confirmed using XRD and Raman spectroscopy. The incorporation of WO₃ nanoparticles into the PAni matrix introduces porosity which enhanced gas sensing properties. The TEM image of PAni-WO₃ hybrid nanocomposite film exploded the average diameter of WO₃ nanoparticles ranging from 40 to 50 nm. Chemical composition of PAni-WO₃ hybrid nanocomposites was characterized by using X-ray photoelectron spectroscopy (XPS). In order to investigate the gas sensing parameter of PAni-WO₃ hybrid nanocomposite, hybrid nanocomposite film was exposed to different oxidizing gases (Cl₂, NO₂) and reducing gases (NH₃, H₂S, CH₃OH, C₂H₅OH) in range 5–100 ppm concentration of gas. It was observed that the sensors of PAni-WO₃ hybrid nanocomposites showed better sensitivity, selectivity, stability and reproducibility compared to pure PAni and pure WO₃. PAni-WO₃ (50%) hybrid nanocomposite sensor operating at room temperature reveals maximum response of 158% towards 100 ppm of NH₃ gas and also capable to respond very little concentration of 5 ppm NH₃ gas with reasonable response of 24%. The gas sensing mechanism of the nanocomposites in presence of air and with target NH₃ gas atmosphere was discussed in detail with the help of energy band diagram. The interaction of NH₃ and NO₂ gas with PAni-WO₃ hybrid nanocomposite sensor was investigated by employing an impedance spectroscopy also.     

聚苯胺/复合钒钼酸纳米复合材料的制备与表征

采用原位氧化聚合法制备了聚苯胺/复合钒钼酸纳米复合材料,并对其进行了XRD、FT-IR、SEM表征和复阻抗谱分析。结果表明,聚苯胺以单层方式插入复合钒钼酸层间,由于层间缝隙限制以较伸展的链构相存在。随着苯胺(An)含量的增加,复合材料的电导率增大,当m(An):m(H2V10Mo2O31±y)为4:1时,复阻抗Z′小于0.2M?,Z″小于0.1M?。     

Structural,compositional and electrical characterization of Si-rich SiOx layers suitable for application in light sensors

Metal-Oxide-Silicon (MOS) structures containing silicon nanoparticles (SiNPs) in three different gate dielectrics, single SiO_x layer (c-Si/SiNPs-SiO_x), two-region (c-Si/thermal SiO_x/SiNPs-SiO_x) or three-region (c-Si/thermal SiO₂/SiNPs-SiO_x/SiO₂) oxides, were prepared on n-type (100) c-Si wafers. The silicon nanoparticles were grown by a high temperature furnace annealing of sub-stoichiometric SiO_x films (x=1.15) prepared by thermal vacuum evaporation technique. Annealing in N₂ at 700 or 1000 °C leads to formation of amorphous or crystalline SiNPs in a SiO_x amorphous matrix with x=1.8 or 2.0, respectively. The three-region gate dielectric (thermal SiO₂/SiNPs-SiO₂/SiO₂) was prepared by a two-step annealing of c-Si/thermal SiO₂/SiO_x structures at 1000 °C . The first annealing step was carried out in an oxidizing atmosphere while the second one was performed in N₂. Cross-sectional Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy have proven both the nanoparticle growth and the formation of a three region gate dielectric. Annealed MOS structures with semitransparent aluminum top electrodes were characterized electrically by current/capacitance–voltage measurements in dark and under light illumination. A strong variation of the current at negative gate voltages on the light intensity has been observed in the control and annealed at 700 °C c-Si/SiNPs-SiO_x/Al structures. The obtained results indicate that MOS structures with SiO_1.15 gate dielectric have potential for application in light sensors in the NIR–Visible Light–UV range.     

Synthesis and characterization of Manganese doped Tungsten oxide by Microwave irradiation method

The aim of this article is to synthesis tungsten oxide (WO₃) nanoparticle along with Manganese (3 wt% and 10 wt%) by Microwave irradiation method. The physical properties of the synthesized Manganese doped Tungsten oxide materials were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscope (TEM), UV-Diffuse Reflectance Spectroscopy, SEM-EDAX and Photoluminescence studies. The predominant peaks obtained in X-ray diffraction pattern reveal the crystalline nature of the nanoparticles and the structure belongs to Monoclinic for pure and Mn doped WO₃. FTIR analysis shows the presence of Tungsten and oxygen in the synthesis material and verified with EDAX. TEM analysis shows both pristine and Mn doped WO₃ nanopaticles. They are having spherical shaped morphology with average particle size from 35 to 40 nm. UV-DRS revealed that the bandgap energy for pure and Manganese doped WO₃ are discussed in this article. The Scanning Electron Microscope analysis shows the plate like morphology for pure WO₃ and the morphology were decreased by doping Manganese. The defects and oxygen deficiencies were analysed by photoluminescence spectroscopy.     

Structural characterization of SiC nanoparticles

The structure and size of SiC nanoparticles were studied by different characterization methods including small angle X-ray scattering (SAXS), transmission electron microscope (TEM), and X-ray diffraction (XRD). The results showed that particle size distributions determined respectively from SAXS and TEM are comparable and follow the log-normal function. The size distribution of the particles is between 10 to 100 nm with most of them being in the range of 20–50 nm. The average particle size is around 42 nm. XRD identifies the phase of the SiC nanoparticles and suggests the average size of the single crystalline domain to be around 21 nm. The combined results from XRD and SAXS suggest the existence of many polycrystals, which is confirmed by the HRTEM observation of particles with twins and stacking faults. The material synthesis methods leading to various particle sizes are also discussed.     

磁控溅射C/W纳米多层膜的微观结构分析

利用非平衡磁控溅射离子镀技术以纯钨靶和纯石墨靶作为溅射源制备了C/W纳米多层膜。采用X射线衍射（XRD）、X射线光电子能谱（XPS）和高分辨透射电子显微镜（HRTEM）对薄膜相组成及其微观组织结构进行了分析。结果表明：W含量约为9 at.%的C/W薄膜具有周期厚度约为6.5 nm的多层结构;沉积的W元素不以单质态存在,而是与碳元素反应生成了WC纳米晶;薄膜中的碳为非晶态,碳主要以sp2键类石墨态存在。     

XPS analysis and characterization of thin films Cu2ZnSnS4 grown using a novel solution based route

A new technique to grow single phase Cu₂ZnSnS₄ (CZTS) thin films for solar cells applications using a chemical route is presented; this consist in sequential deposition of Cu₂SnS₃ (CTS) and ZnS thin films followed by annealing at 550 °C in nitrogen atmosphere, where the CTS compound is prepared in one step process by simultaneous precipitation of Cu₂S and SnS₂ performed by diffusion membranes assisted CBD (chemical bath deposition) technique and ZnS by conventional CBD technique.Measurements of X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were used to identify the phases present in the CTS and CZTS films as well as to study their structural and morphological properties. Further, the oxidation states and the chemical composition homogeneity in the volume were studied by X-ray photoelectron spectroscopy (XPS) analysis. Oxidation states and results regarding structural and morphological characterization of CZTS films prepared using the novel technique are compared with those results obtained from single phase CZTS films prepared by sequential evaporation of metallic precursors in presence of elemental sulfur. XRD and Raman spectroscopy studies were used to verify that the CZTS films prepared by the novel method do not present secondary phases.     

微波辅助合成纳米WO_3/TiO_2复合材料及其气敏性能

为改善WO3基敏感材料的气敏性能,采用微波回流法一次性合成了纳米WO3/TiO2复合材料,并研究TiO2掺杂量对用其制备的气敏元件气敏性能的影响。结果表明:此气敏元件对体积分数为100×10-6的NOx、二甲苯、H2S和丙酮气体具有较强的敏感性,掺杂w(TiO2)为20%的元件,对H2S和NOx的灵敏度分别为31.18和695.84;掺杂w(TiO2)为30%的元件,对二甲苯和丙酮的灵敏度分别为39.19和35.69。     

Demonstration of enhanced the photocatalytic effect with PtSe2 and TiO2 treated large area graphene obtained by CVD method

Here, we report our method on enhancing the photocatalytic effect with PtSe₂ and TiO₂ treated large area graphene (LAG). The LAG was growth on copper foil at a low temperature (500 °C) under atmospheric pressure by chemical vapor deposition (CVD) method. A facile, fast ultrasonic method was then used to successfully synthesize PtSe₂-LAG/TiO₂ nanocomposites. The composites that were obtained were characterized using X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), Raman spectroscopic analysis, and X-ray photoelectron spectroscopy (XPS). UV–vis diffuse reflectance spectra (DRS) analyses were also performed, and the catalytic behavior was investigated by the decomposition of methylene blue (MB).The as-prepared LAG with a Raman D band was obtained, and graphene layers can be clearly seen in High-Resolution Transmission Electron Microscopy (HRTEM) images. The degradation performance of the MB solution was determined via UV–vis spectrophotometry. This improved photocatalytic activity is a result of the positive synergetic effect between PtSe₂ and LAG in the heterogeneous photocatalyst. In this study, the LAG behaves as an electron transfer agent, contributor, collector, and source of active adsorption sites. The optical properties were also observed to be affected by the different weight ratios of the LAG in the composites by observing their respective band gaps from diffuse reflectance spectra.