有机衬底SnO2:Sb透明导电膜的制备与特性研究

常温下,采用射频磁控溅射法在有机的柔性衬底上制备出了SnO2:Sb透明导电膜,并对薄膜的结构和光电性质进行了研究.制备的样品为多晶薄膜,并且保持了二氧化锡的金红石结构.性能良好的薄膜电阻率为6.5×10-3Ω·cm,载流子浓度为1.2×1020cm-3,霍耳迁移率是9.7cm2·V-1·s-1.薄膜在可见光区的平均透过率达到了85%. 关键词： 柔性衬底 SnO2:Sb透明导电膜 射频磁控溅射法     

Structural and photoluminescence properties of terbium-doped zinc oxide nanoparticles

We present in this paper a study of the structural and photoluminescence （PL） properties of terbium （Tb） doped zinc oxide （ZnO） nanoparticles synthesized by a simple low temperature chemical precipitation method, using zinc acetate and terbium nitrate in an isopropanol medium with diethanolamine （DEA） as the capping agent at 60 ℃. The as-prepared samples were heat treated and the PL of the annealed samples were studied. The prepared nanoparticles were characterized with X-ray diffraction （XRD）. The XRD patterns show the pattern of typical ZnO nanoparticles and correspond with the standard XRD pattern given by JCPDS card No. 36-1451, showing the hexagonal phase structure. The PL intensity was enhanced due to Tb^3＋ doping, and it decreased at higher concentrations of Tb^3＋ doping after reaching a certain optimum concentration. The PL spectra of Tb^3＋ doped samples exhibited blue, bluish green, and green emissions at 460 nm （5^D3 - 7^F3）, 484 nm （5^D4 - 7^F6）, and 530 nm （5^D4 - 7^F5）, respectively, which were more intense than the emissions for the undoped ZnO sample. Based on the results, an energy level schematic diagram was proposed to explain the possible electron transition processes.     

Pd@SnO2 and SnO2@Pd Core@Shell Nanocomposite Sensors

Pd@SnO₂ and SnO₂@Pd core@shell nanocomposites are prepared via a microemulsion approach. Both nanocomposites exhibit high‐surface, porous matrices of SnO₂ shells (>150 m² g^?1) with very small SnO₂ crystallites (<10 nm) and palladium (Pd) nanoparticles (<10 nm) that are uniformly distributed in the porous SnO₂ matrix. Although similar by first sight, Pd@SnO₂ and SnO₂@Pd are significantly different in view of their structure with Pd inside or outside the SnO₂ shell and in view of their sensor performance. As SMOX‐based sensors (SMOX: semiconducting metal oxide), both nanocomposites show a very good sensor performance for the detection of CO and H₂. Especially, the Pd@SnO₂ core@shell nanocomposite is unique and shows a fast response time (τ₉₀ < 30 s) and a very good response at low temperature (<250 °C), especially under humid‐air conditions. Extraordinarily high sensor signals are observed when exposing the Pd@SnO₂ nanocomposite to CO in humid air. Under these conditions, even commercial sensors (Figaro TGS 2442, Applied Sensor MLC, E2V MICS 5521) are outperformed.     

SnO2纳米晶体的制备、结构与发光性质

使用软化学方法在碱性溶液中制备出了颗粒尺寸分布均匀的SnO2纳米颗粒,使用透射电子显微镜(TEM)、X射线衍射(XRD)、光致发光谱(PL)和光吸收谱等方法分析与表征了SnO2纳米颗粒的结构和光学性能.实验中通过表面活性剂的加入来控制纳米颗粒的结晶与凝聚.XRD,TEM的结果表明,原始制备出的SnO2纳米颗粒的平均粒径小于4 nm,为完好的晶体状态.纳米颗粒经过400-1000 ℃退火后晶粒尺寸进一步增大.光吸收谱表明,相对于体材料,纳米颗粒的禁带宽度展宽并随颗粒尺寸增大而红移.光致发光谱测试表明,不同温度下退火的SnO2纳米颗粒在350-750 nm有较强的发光,研究表明这是来源于颗粒表面的氧空位缺陷发光.     

3D hopping conduction in SnO2 nanobelts

The temperature dependence of the electrical transport of an individual tin oxide nanobelt was measured in darkness from 400 to 5 K. We found four intrinsic electrical transport mechanisms through the nanobelt. It starts with thermally activated conduction between 400 K and 314 K, followed by nearest‐neighbor hopping conduction between 268 K and 115 K and variable range hopping conduction below 58 K, with a crossover from the 3D Mott to the 3D Efros–Shklovskii regime at 16 K. We claim that this sequence reveals the three‐dimensional nature of the electrical transport in the SnO₂ nanobelts, even though they are expected to behave as one‐dimensional systems. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sensing low concentrations of CO using flame-spray-made Pt/SnO2 nanoparticles

Tin dioxide nanoparticles of different sizes and platinum doping contents were synthesized in one step using the flame spray pyrolysis (FSP) technique. The particles were used to fabricate semiconducting gas sensors for low level CO detection, i.e. with a CO gas concentration as low as 5 ppm in the absence and presence of water. Post treatment of the SnO₂ nanoparticles was not needed enabling the investigation of the metal oxide particle size effect. Gas sensors based on tin dioxide with a primary particle size of 10 nm showed signals one order of magnitude higher than the ones corresponding to the primary particle size of 330 nm. In situ platinum functionalization of the SnO₂ during FSP synthesis resulted in higher sensor responses for the 0.2 wt% Pt-content than for the 2.0 wt% Pt. The effect is mainly attributed to catalytic consumption of CO and to the associated reduced sensor response. Pure and functionalized tin dioxide nanoparticles have been characterized by Brunauer, Emmett and Teller (BET) surface area determination, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) while the platinum oxidation state and dispersion have been investigated by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). The sensors showed high stability (up to 20 days) and are suitable for low level CO detection: <10 ppm according to European and 50 ppm according to US legislation, respectively.     

Structural,dielectric and photoluminescence properties of co-precipitated Zn-doped SnO2 nanoparticles

Zn-doped SnO₂ nanoparticles were prepared by the chemical co-precipitation route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses of these prepared nanoparticles were carried out for structural and morphological studies. All the samples have been found to have tetragonal rutile structure of the polycrystalline SnO₂ having crystallite size in the range 13–25 nm. TEM micrographs show agglomeration of nanoparticles in all the samples. At a particular temperature, the dielectric constant of all the samples has been found to decrease with increasing frequencies which may be due to rapid polarization processes occurring in SnO₂ nanoparticles. The ac conductivity, σ (ω), has been found to vary with frequency according to the relation σ (ω) ∝ ω^S. The value of S has been found to be temperature dependent, decreasing with increasing frequency which suggests that a hopping process is the most likely conduction mechanism in these nanoparticles. The room temperature photoluminescence (PL) spectra of the undoped and Zn-doped SnO₂ nanoparticles consist of the near band-edge ultraviolet (UV) emission and the defect related visible emissions. The origin of emission peaks in the visible region is attributed to oxygen-related defects that are introduced during growth.     

FP-LAPW Calculations of the EFG at Cd Impurities in Rutile SnO2

We report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO₂(rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO₂ host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions. This revised version was published online in September 2006 with corrections to the Cover Date.     

Enhanced dielectric properties of polyvinylidene fluoride with addition of SnO2 nanoparticles

In this letter, SnO₂/polyvinylidene fluoride (PVDF) nanocomposites with outstanding dielectric properties were fabricated. The SEM and TEM images showed that SnO₂ nanoparticles with size of 5–7 nm dispersed homogeneously in polymer matrix. The significantly improved dielectric constant was well explained by percolation theory. The nanocompo‐ sites can retain a certain value of breakdown field. The maximum energy density of SnO₂/PVDF nanocomposites was 5.4 J/cm³, two times that of the pure polyvinylidene fluoride. These findings suggest that SnO₂/PVDF nanocomposites are suitable candidates for energy storage applications. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Encapsulation of SnO2/Sn Nanoparticles into Mesoporous Carbon Nanowires and its Excellent Lithium Storage Properties

A peculiar nanostructure of encapsulation of SnO₂/Sn nanoparticles into mesoporous carbon nanowires (CNWs) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), X‐ray diffraction (XRD), BET, energy‐dispersive X‐ray (EDX) spectrometer, and X‐ray photoelectron spectroscopy (XPS) characterizations. The 1D mesoporous CNWs effectively accommodate the strain of volume change, prevent the aggregation and pulverization of nanostructured SnO₂/Sn, and facilitate electron and ion transport throughout the electrode. Moreover, the void space surrounding SnO₂/Sn nanoparticles also provides buffer spaces for the volumetric change of SnO₂/Sn during cycling, thus resulting in excellent cycling performance as potential anode materials for lithium‐ion batteries. Even after 499 cycles, a reversible capacity of 949.4 mAh g^?1 is retained at 800 mA g^?1. Its unique architecture should be responsible for the superior electrochemical performance.     

Co$lt;sub$gt;2$lt;/sub$gt;SnO$lt;sub$gt;4$lt;/sub$gt;/Graphene复合材料的制备与电化学性能研究

实验首先采用改进的Hummers法制备氧化石墨,然后以氧化石墨烯为前驱体,通过水热法将锡酸钴纳米颗粒均匀镶嵌在石墨烯薄膜基片上,最终获得Co₂SnO₄/Graphene镶嵌复合材料. 采用X射线衍射（XRD）、扫描电子显微镜（SEM）对材料的结构和形貌进行表征,通过恒电流充放电（CC）、循环伏安法（CV）与交流阻抗法（EIS）测试了材料的电化学性能. 实验结果表明,石墨烯良好的分散性及较高的电子导电率,可以提高锡酸钴材料的电化学性能,材料首次可逆容量达到1415.2 mA·h/g,50次循环后仍能保持469.7 mA·h/g的放电比容量. 关键词： 2SnO₄')" href="#">Co₂SnO₄ 石墨烯 电化学性能 锂离子电池     

Preparation, characterization and room temperature photoluminescence properties of a zinc oxide nanosheet network grown on glass substrate by a facile chemical route

An ultralong and ultrathin zinc oxide nanosheet network grown on glass substrate is prepared using an organic CTAB (cetyltrimethylammonium bromide, CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻) and the simple chemical materials (Zn(AC)₂·2H₂O and NaOH) by hydrothermal method. The morphology and microstructure of ZnO nanosheet network have been characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis spectroscopy. The results revealed that the product grown on glass substrate was the ultralong and ultrathin zinc oxide nanosheet network and the crystalline hexagonal wurtzite ZnO crystal structure. The zinc oxide nanosheet network exhibits room temperature photoluminescence (RTPL) characteristics and three blue emissions located at 452, 459, and 469 nm, and a green emission located at about 494 nm were observed.     

Surface modification and fluorescent properties of Mn2+-doped and undoped ZnS nanoparticles

Abstract

ZnS nanoparticles and Mn²⁺-doped ZnS nanoparticles were prepared by a reverse micelle reaction system. In addition, ZnS and Mn²⁺-doped ZnS nanoparticles were modified with poly(vinyl alcohol) (PVA) and 1-dodecanethiol (C₁₂H₂₅SH). The average particle size of the ZnS sample is determined around 2.3 nm by using the well-known Scherrer equation, which is in accordance with the results obtained from UV–vis and TEM analysis. Fluorescence intensity of the Mn²⁺-doped ZnS nanoparticles increases with increasing Mn²⁺ content compared with undoped ZnS nanoparticles, and coating PVA can also make fluorescence intensity increase. Different Zn²⁺/S^2- or C₁₂H₂₅SH/Zn²⁺ can affect intensity of PL emission peak and its position, which is discussed in this paper.     

Effect of nano-sized SiO2 on the optical properties of YVO4:Eu3+ phosphors

In this paper, YVO₄: 1%Eu³⁺ phosphor was synthesized via solid state method at 1100 °C. Then TEOS was used as the source of silica, to coat the phosphors, using sol–gel approach. HRTEM analysis confirmed the formation of adhered and smooth coating layer with the thickness of 40–50 nm. From the experiments and characterizations, we found that although the amounts of added SiO₂ to the phosphors were not remarkable, but it resulted in enhancement of photoluminescence properties. Interestingly, under the excitation wavelength of 310 nm, the efficiency of the phosphors increased by about 20%. Also, a considerable effect of coating layer on decrease in surface oxygen vacancies was studied using ESR technique. Finally it was found that SiO₂ coating of YVO₄:Eu³⁺ phosphors, improves both chemical stability and thermal quenching, effectively.     

Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors

The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors.     

Synthesis by sol–gel process,structural and optical properties of nanoparticles of zinc oxide doped vanadium

We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol–gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed.     

SiO2干凝胶光致发光性质的研究

以硅酸酯Si(OC2H5)4(TEOS)和H2N(CH2)3Si(OC2H5)3(APS)为主要原料,在不同的条件下(催化剂、热处理、高分子添加剂)通过溶胶-凝胶法制备了一系列不同组成的SiO2干凝胶,并通过发光光谱对所得的干凝胶进行了表征.在长波365nm紫外光激发下,干凝胶样品都显示出较强的蓝光发射,但其发光波长和发光忖强度随着组成和处理条件的不同而有明显的差异.APS与有机酸(醋酸)和无机酸(盐酸、硝酸、硫酸)所得SiO2干凝胶的结果为IHAc(λmax=432nm)＞JHNO3(λmax=441nm)≈IH2SO4(λmax=426nm)>IHCI(λmax=442nm),并且在APS与HCl作用所得的干凝胶样品中,明显存在两种发光中心(其发射峰值波长分别位于442nm和487nm,相应的激发波长分别位于365nm和273nm).一定量的TEOS与APS相混合并与HAc作用不仅有利于干凝胶样品的迅速形成,而且有利于提高其发光强度:当R(APS/TEOS+TEOS摩尔比)=0.5～0.7时,样品发光较强;在0.5摩尔APS+0.5摩尔TEOS与3摩尔HAc的反应过程中加入高分子添加剂聚乙二醇(PEG5000、PE10000),所得样品的发光强度先随着PEG的加入量的增加而变强,然后随着PEG的加入量的增加而变弱,PEG5000和PEG10000的最佳掺杂量分别为0.8g和0.6g.在温度20～200℃的范围内,干凝胶样品的发光强度随着热处理温度的升高而增强,同时真空中处理样品的发光强度大于空气中处理样品的发光强度.这表明干凝胶样品的发光和氧缺陷及碳杂质有关.     

Correlated room temperature ferromagnetism and photoluminescence in Al-doped SnO2 nanoparticles

We investigated the single exciton and multiple exciton generation (MEG) behavior in Ag₇ and single Cu atom-doped Ag₇ quantum clusters using ab initio. MEG is observed for the first time in metal clusters. The results indicate that multiple excitons appear in the visible and near ultraviolet light ranges. Single excitations are main contribution for the optical spectra, while the multiple excitons merely contribute for some peaks at the higher energies. However, occurrence of MEG enhances the optical absorption in Ag₇ cluster. The optical spectrum of pure Ag₇ cluster obtained using the symmetry-adapted cluster theory with configuration interaction, and time-dependent density functional theory is in excellent agreement with experiment spectrum. As observed in both single Cu atom-doped Ag₇ clusters, redshifts and suppressions of the MEG-related absorption peaks are observed compared with pure Ag₇ cluster.