掺杂Mn对CeO2-ZrO2-Al2O3材料性质的影响

采用共沉淀法制备了一系列Mn掺杂摩尔分数为0～5%的CeO2-ZrO2-Al2O3(CZA)复合氧化物, 并采用BET, OSC, XRD, XPS, H2-TPR等方法对所制备的材料进行了表征. 结果表明, 所制备的材料均形成了稳定的CZA固溶体, 尤其是Mn掺杂0.5%的材料在600和1000 ℃焙烧后均表现出最好的织构性能. OSC和H2-TPR的结果表明, Mn掺杂量≤1%时, 氧在材料中的体相移动是材料储氧和被还原的速控步骤, 并且Mn的掺杂量为0.2%时, 储氧量最大, 材料的还原温度也最低; Mn掺杂量>1%时, Mn物种对材料储氧和被还原的作用显著. XPS结果表明, Mn在焙烧过程中会迁移向表面, 结合H2-TPR结果可知, 新鲜样品表面的MnOx物种主要为Mn2O3, 而老化样品主要为Mn3O4.     

以Fe2O3为原料制备LiFePO4/C复合材料及其性能研究

以Fe2O3为铁源原料, 利用热还原法成功地制备了LiFePO4/C复合材料. 用XRD以及SEM对材料的晶体结构以及表面形貌进行了表征. 通过循环伏安和充放电测试研究了材料的电化学性能. 研究结果表明， 于700 ℃下制备的LiFePO4/C复合材料在0.1C的倍率下可以得到放电容量144.8 mA·h/g, 在循环160次后, 容量仍保持在141.4 mA·h/g. 这种以廉价的Fe2O3代替目前常用的二价铁盐原料方法, 具有减少LiFePO4合成成本的优点.     

锂电池正极材料Li1.06Mn0.8Cr0.14O2的水热合成及其光谱研究

采用水热方法合成了掺铬锂锰氧化合物, X射线衍射和Raman光谱分析结果表明, 所得材料为具有NaFeO2结构的晶体. 由等离子发射光谱(CIP)确定其组分为Li1.06Mn0.8Cr0.14O2. X射线光电子能谱(XPS)研究结果表明, 与未掺杂的LiMnO2相比, 所得材料中Mn的平均价态增加, 这将抑制因Mn3+离子的存在而产生的Jahn-Teller畸变, 有利于提高材料的电化学循环性能.     

镓酸镧基中温-SOFC的新型阳极NiO-La0.3Ce0.7O2-δ研究

采用共沉淀法制备了NiO-La0.3Ce0.7O2-δ(LDC30)新型阳极材料, 通过对其配方与性能的研究, 探索获得中温SOFC高性能阳极材料的新途径.     

BaCo0.7Fe0.2Nb0.1O3-δ膜反应器还原侧表面反应机理

研究了BaCo0.7Fe0.2Nb0.1O3-δ(BCFN)透氧膜反应器还原侧表面反应机理, 分析了表面催化微粒及催化床对膜反应器的作用. 提出了“催化解离机制”是构成甲烷重整BCFN膜反应器透氧量上升的主要原因; CH4, H2及CO在BCFN膜表面的反应活性依次为H2>CO>CH4; 当CH4气氛中加入H2或CO时, BCFN膜表面的主要发生由CH4直接氧化转变H2或CO的氧化反应, 同时极大提升了BCFN膜反应器的透氧量; BCFN膜表面氧化反应为“晶格氧”氧化反应模式主导.     

锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2的合成、表征及电化学性能

以过渡金属乙酸盐和氢氧化锂为原料, 应用共沉淀或流变相预处理高温烧结法优化并制备出LiNi0.4Co0.2Mn0.4O2正极材料. X射线衍射技术(XRD)及Rietveld结构精修、扫描电子显微技术(SEM)、综合热分析(TG-DSC)表征结果和电化学测试结果表明, 该材料具有单一层状结构, 颗粒大小均匀, 热稳定性好, 首次放电比容量高达208.7 mA·h/g(2.0-4.6V, 0.1 C), 电化学性能优异. 非原位(ex situ)XRD测定结果表明, 材料充至高电位下发生的不可逆相变造成了材料的循环容量衰减.     

Y2O3和Nd2O3介孔薄膜的制备与表征

以聚乙烯合丁烯-嵌-聚氧乙烯嵌段共聚物(PHB-PEO)作模板, 采用蒸发诱导自组装方法, 分别制备了Y2O3和Nd2O3介孔薄膜. 用小角、广角X射线衍射和透射电子显微镜对薄膜样品在不同的热处理阶段进行了表征. 结果表明, 所制备的Y2O3和Nd2O3薄膜样品呈现一种大孔径(平均孔径分别约为11.5和12.5 nm)、有序的立方扭曲球形孔排列、稳定于450 ℃并具有部分晶态孔壁结构的介孔薄膜材料.     

等离子体协同CuO/TiO2-γ-Al2O3催化CH4脱除NO

对合成的12%CuO/15%TiO2/γ-Al2O3催化剂进行了BET和XRD表征, 并结合等离子体与催化协同脱除NO的反应装置, 考察了单一等离子体、单一催化剂以及等离子体与催化协同脱除NO+CH4+O2的反应结果, 研究了上述三种条件下NO和CH4的转化率. BET表征结果表明, 15%TiO2/γ-Al2O3的孔径分布在微孔和介孔之间; XRD结果表明, 催化剂表面有CuO晶相; 反应活性数据表明, 单一等离子体存在时, NO和CH4的转化率随着等离子体的输入功率增大而逐渐增加, 反应体系引入体积分数为2.5%的O2气促进了NO和CH4的转化; 使用单一催化剂时, NO和CH4的转化率随温度升高而分别增大至30%和20%. 同时NO转化率随O2气浓度的增加先增加后降低, CH4随O2气浓度的增加转化率逐渐增大; 等离子体与催化剂协同作用NO+CH4+O2反应中, NO和CH4的转化率随O2气浓度的增加与只有催化剂存在条件下的变化趋势一致, 但是增大了NO的低温转化率, 同时CH4的转化率提高到了90%.     

Ce和Dy在Cd0.5Zn0.5B4O7中的发光特性及能量双向传递

采用高温固相法制备了白蓝光双发射为一体的Cd0.5Zn0.5B4O7∶Ce/Dy系列发光材料. 由XRD测得Cd0.41Zn0.5B4O7∶Ce0.04/Dy0.02的晶胞参数: a=1.3885 nm, b=0.8020 nm, c=0.8670 nm, 属于正交晶系, Pbca空间群. 在Ce/Dy双掺的体系中存在Ce3+和Dy3+两种发光中心, 254~350 nm激发主要是Dy3+的 4F9/2→6H15/2和4F9/2→6H13/2跃迁发射, 而355—390 nm激发主要为Ce3+的5d→4f跃迁发射. 340 nm激发Ce/Dy双掺发光体的发射强度是同浓度Dy3+单掺的31倍, Ce3+是Dy3+的高效敏化剂, 而355—390 nm激发Dy3+是Ce3+的敏化剂. 体系中存在少见的Ce3+→Dy3+与Dy3+→Ce3+的能量双向传递.     

ABO3型钙钛矿结构的可见光光催化剂LaCo0.5Ti0.5O3的设计与合成

采用溶胶-凝胶法在较低温度条件下设计合成了新型的具有ABO3型钙钛矿结构的三元金属复合氧化物LaCo0.5Ti0.5O3. 通过TG-DTA, XRD, XPS, UV-Vis DRS等测试技术和可见光光催化活性测试对其进行了表征. 结果表明, 与LaCoO3和La2Ti2O7相比, LaCo0.5Ti0.5O3样品表现出相对较高的可见光光催化活性, 并且合成温度较低. 这是由于原料中的Co2+和Ti4+离子通过电荷补偿作用使产物B位的两种金属均以+3价氧化态分布所致.     

单粒子表面增强拉曼光谱的二维成像研究

以单个椭球形Fe₂O₃@Au核壳粒子作为SERS活性基底, 苯硫酚(TP)作为探针分子, 研究了椭球形粒子表面SERS效应的分布, 对比了粒子尖端以及中间SERS效应的差别. 为了得到单个粒子表面不同部分对SERS强度的贡献差别, 通过数学模拟和解析了探针分子SERS的二维成像(2D-mapping)信号, 获得了粒子边缘不同点的SERS效应. 模拟分析结果表明, 当xy平面内粒子在垂直入射(z轴)平面波作用下, 单个椭球形Fe₂O₃@Au核壳粒子表面单位面积上的SERS强度相差极大, 粒子长轴方向端点附近单位面积上的SERS效应最大, 而其它表面部分较弱, 其中与短轴平行方向的表面附近为最弱, 差异可达到约2~3个数量级. 若考虑SERS增强主要为电磁场增强的尖端效应, 则单个椭球形粒子尖端的局域感应电磁场为垂直方向的5倍.     

Amplified light scattering and emission of silver and silver core-silica shell particles

Side versus forward light scattergrams, and fluorescence (488 nm excitation) intensity versus particle count histograms were gathered for bare, R6G-coated, and silica-R6G-coated silver particles of 150-200 nm diameter, one-by-one by flow cytometry. Fluorescence emission intensity of the composite particles monotonically increased and then reached a plateau with greater R6G concentrations, as measured by flow cytometry. Fluorescence amplification factors of up to 3.5x10(3) were estimated by reference to measurements on core-shell particles with silica instead of silver cores. Huge surface enhanced Raman scattering (SERS) intensities, at least 10(14)-fold greater than normal Raman scattering intensities, were observed with 633 nm excitation for molecules such as rhodamine 6G (R6G) on the same single particles of silver. Although routine transmission (TEM) and scanning (SEM) electron microscopies showed gross structures of the bare and coated particles, high-resolution field emission scanning electron microscopy (FE-SEM), revealed Brownian roughness describing quantum size and larger structures on the surface of primary colloidal silver particles. These silver particles were further characterized by extinction spectra and zeta potentials. Structural and light scattering observations that are reported herein were used to tentatively propose a new hierarchical model for the mechanism of SERS.     

Au/Ag核-壳结构纳米粒子的制备及其SERS效应

随着大量有关表面增强拉曼散射 (SERS)的实验和理论研究的开展 ,金属纳米粒子作为一类重要的 SERS增强介质 ,已引起了人们浓厚的研究兴趣 [1] .而 Au和 Ag作为最常用的活性基底物质 ,更是研究的热点 [2 ,3 ] .最近 ,美国印第安那大学的 Nie等 [4 ] 在单个银纳米粒子上 ,观察到高达 1 0 14 ～ 1 0 15的SERS因子 .同时 ,他们的另外一项工作表明银纳米粒子的形状和大小对 SERS活性有很大影响 [5] .但是 ,由于 Ag溶胶制备的重复性较差 ,且粒度分布不均匀 ,通过控制银颗粒大小而调控 SERS活性是相当困难的[6] .与 Ag相比 ,Au在可见光…     

Synthesis of p-aminothiophenol-embedded gold/silver core-shell nanostructures as novel SERS tags for biosensing applications

We describe a novel surface-enhanced Raman scattering (SERS) tag that is based on Au/Ag core-shell nanostructures embedded with p-aminothiophenol. The Au/Ag core-shell sandwich nanostructures demonstrate bright and dark stripe structure and possess very strong SERS activity. Under optimum conditions, the maximum SERS signal was obtained with a 10?nm thick Ag nanoshell, and the enhancement factor is 3.4?×?10⁴ at 1077?cm^?1. After conjugation to the antibody of muramidase releasing protein (MRP), the Au/Ag core-shell nanostructures were successfully applied to an SERS-based detection scheme for MRP based on a sandwich type of immunoassay.

不同Pt壳厚度Au_(core)@Pt_(shell)纳米粒子SERS效应

以Au粒子(55nm)为核,抗坏血酸为还原剂,将不同量的Pt沉积在Au核上,制得可控壳层厚度(0.3～6nm)的Pt包Au纳米粒子(Aucore@Ptshell).用紫外-可见吸收光谱、扫描电镜(SEM)、透射电镜(TEM)和电化学循环伏安法等观测Aucore@Ptshell纳米粒子的表面形貌、结构和性能.另以SCN-为探针,考察了Pt壳厚度对Aucore@Ptshell纳米粒子SERS信号的影响.结果表明,SCN-离子的SERS信号强度随Pt壳厚度的增加呈指数衰减,当Pt壳厚度为1.4nm时,Aucore@Ptshel纳米粒子表现出铂良好的电化学性能,又具有较强的SERS活性.     

Ag负载TiO2核壳基底的制备及对结晶紫的高效(SERS)检测

通过简单的一步水热法制备了TiO2核壳微球，然后经过原位光还原将Ag负载于其表面，成功得到了用于有机分子检测的Ag负载TiO2核壳表面增强拉曼散射（SERS）基底。得益于TiO2核壳微球的结构，其对结晶紫（CV）分子表现出高的吸附容量。单一TiO2核壳微球对CV的检测限为10-3 M，而负载Ag以后，其对CV的检测限能达到10-7 M，增强因子（EF）可达3.49×105。优异的SERS检测性能可能归因于以下几点：（1）半导体TiO2为Ag纳米粒子提供了均匀分散的骨架，创造了高密度的热点；（2）为CV分子提供了大的吸附面积；（3）复合材料促进了激发光子的相互作用。     

Au-Ag合金纳米粒子制备及其表面增强拉曼光谱研究

首先采用柠檬酸钠法制得Au-Ag合金纳米种子, 然后采用盐酸羟胺生长法得到不同组成的Au-Ag合金纳米粒子. 在其UV-Vis光谱中只观察到一个位于单金属银和金之间的等离子体共振峰, 表明Au-Ag合金纳米粒子已经形成. TEM结果表明, 合金纳米粒子的粒径约为60 nm, 且颜色均一, 没有明显的核壳结构. 用苯硫酚(TP)作为探针分子研究了合金纳米粒子的表面增强拉曼光谱(SERS). 结果表明, SERS强度与合金纳米粒子的组成和尺寸有关. 当纳米粒子粒径一定时, 除Au25Ag75外, 随着金的增加SERS强度增强. Au25Ag75的粒径比Ag小, 导致SERS强度比Ag低. Au50Ag50和Au75Ag25加入TP分子后, 其聚集方式与Au相似, 等离子体共振峰逐渐靠近1064 nm, 金含量较高时, TP的SERS归于聚集体的等离子体共振增强的贡献.     

The effects of Au aggregate morphology on surface-enhanced Raman scattering enhancement

We have identified empirically a relationship between the surface morphology of small individual aggregates (<100 Au nanoparticles) and surface-enhanced Raman scattering (SERS) enhancement. We have found that multilayer aggregates generated greater SERS enhancement than aggregates limited to two-dimensional (2D) or one-dimensional structures, independent of the number of particles. SERS intensity was measured using the 730 cm(-1) vibrational mode of the adsorbed adenine molecule on 75 nm Au particles, at an excitation wavelength of 632.8 nm. To gain insight into these relationships and its mechanism, we developed a qualitative model that considers the collections of interacting Au nanoparticles of an individual aggregate as a continuous single entity that retains its salient features. We found the dimensions of the modeled surface features to be comparable with those found in rough metal surfaces, known to sustain surface plasmon resonance and generate strong SERS enhancement. Among the aggregates that we have characterized, a three 75 nm nanoparticle system was the smallest to generate strong SERS enhancement. However, we also identified single individual Au nanoparticles as SERS active at the same wavelength, but with a diameter twice in size. For example, we observed a symmetric SERS-active particle of 180 nm in diameter. Such individual nanoparticles generated SERS enhancement on the same order of magnitude as the small monolayer Au aggregates, an intensity value significantly stronger than predicted in recent theoretical studies. We also found that an aspect of our model that relates the dimensions of its features to SERS enhancement is also applicable to single individual Au particles. We conclude that the size of the nanoparticle itself, or the size of a protrusion of an irregularly shaped single Au particle, will contribute to SERS enhancement provided that its dimensions satisfy the conditions for plasmon resonance. In addition, by considering the ratio of the generated intensities of typical 2D Au aggregates to the enhancement of individual SERS-active particles, a value of approximately 2 is determined. Its moderate value suggests that it is not the aggregation effect that is responsible for much of the observed SERS enhancement but the surface region associated with the SERS-active site.     

Ag_核Au_壳金属复合纳米粒子的制备及表面增强拉曼光谱研究

在已制备好的Ag纳米粒子表面,通过化学还原的方法沉积生长Au包裹层,制备了粒子尺寸为50-70nm的Ag核Au壳复合纳米粒子.通过改变AuCl₄^-量,使Ag_100-xAu_x中Au的含量由x=0变为x=30.用UV-Vis吸收光谱和透射电子显微镜(TEM)对该结构纳米粒子进行了表征,并以对巯基苯胺(PATP)为探针分子进行表面增强拉曼光谱(SERS)研究.表面拉曼光谱表明,该结构的纳米粒子具有比Ag更强的SERS活性,随着Au:Ag比例的逐渐增加,其活性呈现先增大后减小的趋势,其最大增强约为Ag纳米粒子的10倍.     

Characterization of the surface enhanced raman scattering (SERS) of bacteria

The surface enhanced Raman scattering (SERS) of a number of species and strains of bacteria obtained on novel gold nanoparticle (approximately 80 nm) covered SiO(2) substrates excited at 785 nm is reported. Raman cross-section enhancements of >10(4) per bacterium are found for both Gram-positive and Gram-negative bacteria on these SERS active substrates. The SERS spectra of bacteria are spectrally less congested and exhibit greater species differentiation than their corresponding non-SERS (bulk) Raman spectra at this excitation wavelength. Fluorescence observed in the bulk Raman emission of Bacillus species is not apparent in the corresponding SERS spectra. Despite the field enhancement effects arising from the nanostructured metal surface, this fluorescence component appears "quenched" due to an energy transfer process which does not diminish the Raman emission. The surface enhancement effect allows the observation of Raman spectra of single bacterial cells excited at low incident powers and short data acquisition times. SERS spectra of B. anthracis Sterne illustrate this single cell level capability. Comparison with previous SERS studies reveals how the SERS vibrational signatures are strongly dependent on the morphology and nature of the SERS active substrates. The potential of SERS for detection and identification of bacterial pathogens with species and strain specificity on these gold particle covered glassy substrates is demonstrated by these results.