Au纳米颗粒和CdTe量子点复合体系发光增强和猝灭效应

利用金属蒸发真空多弧离子源注入机, 将Au离子注入到高纯石英玻璃来制备镶嵌有Au 纳米颗粒的衬底材料, 随后将化学方法合成的CdTe量子点旋涂在玻璃衬底上制备了Au纳米颗粒和CdTe量子点复合体系. 通过对镶嵌有Au纳米颗粒的衬底进行热退火处理来控制Au纳米颗粒的生长和分布, 系统研究了Au纳米颗粒的局域表面等离子体共振对CdTe量子点光致发光性能的影响. 利用光学吸收谱、原子力显微镜、透射电子显微镜和光致发光谱对样品进行了表征和测试. 光致发光谱表明, Au纳米颗粒的局域表面等离子体对CdTe量子点的发光有增强效应也有猝灭效应. 深入分析了Au纳米颗粒和CdTe量子点之间的相互作用过程, 提出了关于Au-CdTe 纳米复合体系中CdTe 发光增强和猝灭的新机理. 该实验结果为利用金属纳米颗粒表面等离子体技术制备高发光性能的光电子器件提供了较好的参考.     

基于银胶纳米颗粒的痕量三硝基甲苯的表面增强拉曼光谱的实验研究

近年来对作为典型的硝基苯环类炸药的三硝基甲苯(TNT)的痕量检测受到越来越多的关注。将银胶纳米颗粒作为表面增强拉曼散射(SERS)基底,研究了10-6 mol.L-1的TNT的表面增强拉曼光谱的优化实验条件,重点研究了氯化钠溶液(NaCl)的含量以及碱性水解对TNT的表面增强拉曼光谱的影响。实验发现SERS样品中如果没有加入NaCl溶液,将观察不到TNT的SERS谱。加入的NaCl的含量必须在某一个范围之内才能观察到TNT的SERS谱,而且在这个范围之内,随着NaCl含量的增加,TNT的1 392cm-1处的拉曼峰出现先增大后减小的现象。对NaCl在TNT的SERS中的作用给予了理论解释。研究还发现TNT分子经过碱性水解后,与银纳米颗粒之间的吸附作用增强,其SERS谱的强度明显优于未经碱性水解的SERS结果。     

用于Raman光谱与微纳米结构同步检测的Raman-AFM系统研究

研究和发展了一种将微区拉曼(Raman)光谱检测与原子力显微镜(AFM)微纳米扫描成像相结合的新型Raman-AFM技术。设计了Raman光谱与AFM扫描成像的原位检测探头;研制出相应的Raman-AFM系统;利用该系统,对ZnO纳米颗粒和TiO2纳米薄膜开展了微区Raman光谱与微纳米结构的检测实验。研究表明,所获得的Raman光谱检测结果与理论值良好吻合,同时,AFM扫描检测得到的图像很好地表征了样品的微纳米结构,从而实现了微区Raman光谱与AFM图像的原位及同步检测,验证了这一技术的可行性,为Raman光谱技术与微纳米技术领域的实际应用提供了技术基础。     

Al2O3薄膜/纳米Ag颗粒复合结构的光吸收谱及增强Raman散射光谱研究

Al₂O₃介质薄膜与纳米Ag颗粒构成的复合结构,被应用于表面增强Raman散射探测实验中,其中Al₂O₃介质薄膜对纳米Ag颗粒的吸收谱及增强Raman散射光谱的影响被特别关注.该复合结构的光学特性表征出纳米Ag颗粒的偶极振荡特性.从光吸收谱中可以看到,其共振吸收谱随Al₂O₃介质薄膜厚度增加而在整个谱域上发生红移,表明纳米Ag颗粒的周围介电常数随Al₂O₃介质薄膜厚度的增加而增大.采用罗丹明6G作为探针原子,6个Raman特征峰的平均增益值作为表征表面增强Raman散射衬底增益程度的量度.实验结果表明,Al₂O₃介质薄膜层的引入提高了纳米Ag颗粒的衬底介电常数,并引起了散射共振的增强,从而使表面增强Raman散射强度提高. 关键词： 纳米Ag薄膜 共振吸收 表面增强Raman散射 介电常数     

孤立分散在SiO2基质中的半导体InSb纳米颗粒界面效应的MS-XANES研究

利用MS-XANES计算研究了嵌入在SiO₂介质中的InSb纳米颗粒的界面效应, 结果显示Sb K-XANES实验谱在白线峰强度增大和白线峰向高能一侧展宽这两个特点的起因是: 1. SiO₂介质透过界面处强的Sb-O共价键间接地影响和改变了InSb团簇中Sb原子内部的势分布; 2. 通过InSb纳米颗粒界面处存在着强的Sb-O共价键使得Sb原子的5p电子被耗尽来提高InSb纳米颗粒Sb原子的5p的空穴数. 这两方面共同决定了InSb纳米颗粒的Sb K-XANES实验谱在白线峰 强度的增大. 此外, 由于纳米颗粒的界面效应, 仅仅把白线峰的强度增大归因于吸收原子电荷转移带来的空穴数增加, 并依此通过白线峰的强度计算吸收原子的空穴数是不合理的.     

激光激发等离子体中的光吸收实验

利用两个激光等离子体相互作用获得离子的吸收光谱的技术已得到很大改善。实验中采用了新的信号检测系统和新的数据处理技术。此实验技术已成功地应用到对瞬态的中等Z离子的吸收谱的测量。获得了BeⅣ、BeⅢ、BeⅡ和BeⅠ离子的1s电子的吸收谱及相关的软X射线范围内的光电离谱。简要地实验得到的碳离子的初步结果。     

稀磁ZnO纳米颗粒的生长和性能

利用Zn、Fe、Mn、Co的铜铁试剂盐为前驱体,胺为表面包裹剂,在200℃N2保护下生长了2%的过渡金属离子掺杂的ZnO稀磁纳米晶体,研究了纳米晶体的结构、形态、光学和磁学性能。所有ZnO纳米晶体均为近圆形的颗粒,晶体结构为六角纤锌矿结构,无其他氧化物相的析出,但过渡金属离子的掺入使纳米颗粒的尺寸增大。在掺杂纳米颗粒的吸收谱和发射谱中均可以观察到明显的激子吸收和发射峰,所有纳米颗粒在温度高于43K时只有顺磁性。     

Al2O3薄膜/纳米Ag颗粒复合结构的光吸收谱及增强Raman散射光谱研究

Al₂O₃介质薄膜与纳米Ag颗粒构成的复合结构,被应用于表面增强Raman散射探测实验中,其中Al₂O₃介质薄膜对纳米Ag颗粒的吸收谱及增强Raman散射光谱的影响被特别关注.该复合结构的光学特性表征出纳米Ag颗粒的偶极振荡特性.从光吸收谱中可以看到,其共振吸收谱随Al₂O₃介质薄膜厚度增加而在整个谱域上发生红移,表明纳米Ag颗粒的周围介电常数随Al₂O₃介质薄膜厚度的增加而增大.采用罗丹明6G作为探针原子,6个Raman特征峰的平均增益值作为表征表面增强Raman散射衬底增益程度的量度.实验结果表明,Al₂O₃介质薄膜层的引入提高了纳米Ag颗粒的衬底介电常数,并引起了散射共振的增强,从而使表面增强Raman散射强度提高.     

金纳米棒的单光束光操纵及其散射谱的测量

利用波长为800nm的单光束飞秒激光对水溶液中的金纳米棒颗粒进行了稳定地二维光捕获.通过测量金纳米棒的散射谱研究了光阱中金纳米棒之间的耦合相互作用.比较光阱中只有单个金纳米棒被捕获和两个金纳米棒同时被捕获时的散射谱.结果表明,当两个金纳米棒同时被光阱捕获时,金纳米棒之间相互排斥,存在一定的间隔,该间隔使得两个金纳米棒之间没有发生表面等离子耦合相互作用.该实验结果为金纳米棒的光操纵及其在生物分子探测等领域的研究提供技术指导及实验参考.     

修饰银电极上单壁碳纳米管的表面增强拉曼散射

本文采用修饰了银纳米颗粒的银电极作为基底,获得了高质量的单壁碳纳米管(SWCNTs)的表面增强拉曼散射(SERS)光谱。在1100~1500 cm-1范围内观测到了一组表征SWCNTs结构的新峰。修饰在银电极上的银纳米颗粒不仅可以保证SWCNTs在这一体系中吸附的紧密性,而且通过变面等离子体共振起到了电磁放大的作用。通过对银纳米颗粒修饰银电极表面SWCNTs的SERS光谱及其随电位变化的SERS光谱的研究,我们可以研究这一过程中的SERS机制。理论和实验结果表明,银纳米颗粒修饰银电极上单壁碳纳米管的SERS很有潜力成为一种检测单壁碳纳米管合成质量的新方法。     

Electron dynamics in supported metal nanoparticles: relaxation and charge transfer studied by time-resolved photoemission

Resonant excitation of the plasmon polariton in supported nanoparticles leads to a strong enhancement of the multiphoton photoemission yield and consequently, the total yield is dominated by the emission from the nanoparticles although they cover only a minor fraction of the surface. This allows investigation of the electron dynamics in supported nanoparticles, directly in the time domain. Here, Ag nanoparticles grown on graphite are used to demonstrate that the transient shape of the photoemission spectrum in time-resolved two-color multiphoton photoemission spectroscopy, reveals the electron relaxation within the nanoparticle, and the dynamic charge transfer between substrate and nanoparticle. The photoemission spectra map the transient electron energy distribution and exhibit a transient shift that is attributed to a dynamic charging of the nanoparticle. The comparison with model calculations comprising the full relaxation cascade in the nanoparticle and substrate, shows that the dynamic charge transfer accounts for almost half of the total deposited energy in the nanoparticle. PACS 78.67.Bf; 73.22.-f; 67.40.Fd; 78.47.+p     

Photophysics of 1-ethynylpyrene-modified RNA base adenine

The photophysical behaviour of a pyrene-modified adenine base is examined. Time-dependent absorption and fluorescence spectroscopy is used to shed light on the fluorescence behavior and the charge transfer between the fluorophore and the nucleobase. The results from TCSPC, fluorescence upconversion and pump-probe absorption spectroscopy are reported, compared and analyzed. This study is a prerequisite for the detailed characterization of RNA dynamics in real time and on a molecular time scale.     

Role of surface modification of CdS nanoparticles on the performance of hybrid photovoltaic devices based on p-phenylenevinylene derivate

The role of organic capping ligand of semiconductor nanoparticles in dictating the interfacial charge transfer processes in hybrid semiconductor nanoparticles/polymer-based photovoltaic devices is investigated. Morphology, optical and structural study of the CdS nanoparticles and the hybrid material were accomplished using X-ray diffraction (XRD), absorption (UV–vis), atomic force microscopy (AFM), transmission electron microscopy (TEM), photoluminescence (PL) and time resolved photoluminescence spectroscopy (PLRT). A broad band absorption in UV–visible region and considerable fluorescence quenching of MEH-PPV in the composites are noted indicating a photo-induced charge transfer and dissociation of excitons. Time-resolved photoluminescence measurements indicating decreased lifetime further confirm this process. The solar cells open-circuit voltage and short-circuit current were improved using thiophenol modified CdS nanoparticles as electron acceptor in comparison to MEH-PPV only device demonstrating a promising approach to enhance charge transport in the hybrid nanoparticles–polymer composite photovoltaic cells (PV).     

Comparative charge transfer studies in nonmetallated and metallated porphyrin fullerene dyads

Single material organic solar cells become an interesting area of research to overcome the challenges with efficient charge separation efficiencies in conventional organic solar cells. In this article, we have synthesized nonmetallated and metallated porphyrin‐fullerene dyad materials (H2P‐C60 and ZnP‐C60, respectively) with simple structure, comprehensively studied their charge transfer mechanism, and established a proof of concept that nonmetallated porphyrin‐fullerene dyads are better candidates to be used in organic solar cells compared with metallated dyads. Absorption and electrochemical analysis revealed the ground state electronic interactions between donor‐acceptor moieties in both types of dyads. Driving force (?ΔG^o_ET) for intramolecular electron transfer process was calculated by first oxidation and reduction potentials of dyads. The excited state electronic interactions were characterized by time‐resolved fluorescence and pump‐probe transient absorption experiments. Strong fluorescence quenching of porphyrin along with reduced lifetimes in dyads due to deactivation of singlet excited states by photoinduced charge transfer process between porphyrin/Zn‐porphyrin core and fullerene in different polarity solvents was observed. Transient absorption spectroscopy was also applied to identify the transient spectral features, ie, cationic (H2P⁺/ZnP⁺) and anionic (C₆₀^?) radicals formed because of the charge separation in both types of dyads. Finally, organic solar cell device was also fabricated using the dyads. We obtained higher V_oc, J_sc, and fill factor in single material organic solar cell using H2P‐C60 compared to previous reports.     

同步荧光光谱法研究肿瘤芳香族氨基酸残基含量的变化

用同步荧光光谱法评估原发性肝细胞癌患者血浆、肝癌荷瘤小鼠以及培养细胞(HepG2和HL-7702)中酪氨酸(Tyr)和色氨酸(Trp)残基水平变化。固定发射波长λ_em和激发波长λ_ex之间的波长差Δλ分别为20和60 nm,激发和发射单色器同时进行扫描,确定350 nm为Trp的同步特征发射峰位置,318 nm为Tyr的同步特征发射峰位置。结果表明,肝癌患者及荷瘤小鼠血浆蛋白质所含Tyr和Trp残基的荧光强度明显增加。相反,肝癌细胞或荷瘤小鼠肿瘤组织中Tyr和Trp残基荧光强度却随生长时间增长而减少。进一步实验表明,具有抗癌活性的苦参碱处理癌细胞后,细胞Tyr和Trp残基的荧光强度升高。这些结果表明,Tyr和Trp残基的变化可能参与了肿瘤的发生发展。     

CdS化学修饰TiO2纳米管阵列电极的传质特性分析

通过声电阳极氧化-化学沉积的方法制备CdS修饰的TiO₂纳米管阵列,并对其进行形貌表征及光电性能和传质特性的研究。结果表明;相对于未修饰的TiO₂纳米管列电极,CdS纳米粒子的化学修饰在增强电极对可见光吸收能力的同时,可减小电荷载流子的迁移阻力而有效提高光生电荷的分离和传递速率。在超声场中进行化学沉积,CdS纳米粒子可在TiO₂纳米管壁上均匀沉积,使得传质阻力进一步降低而获得相对最大的光电流和电荷载流子密度(9.29×10¹⁹cm^-3)。     

Optical and IR study of CdS nanoparticles dispersed in a new confined p-phenylenevinylene

In the present study we have synthesized CdS semiconducting quantum dots by reverse micelle method using dodecanthiol (C₁₂H₂₆S) as the capping agent. The synthetic medium consists of a quaternary water/Sodium dodecyl sulfate (SDS)/buta-1-ol/hexane microemulsion. The size of the particles was controlled by changing the molar ratio W=[H₂O]/[SdS], where [H₂O] and [SdS] are the molar concentrations in hexane of water and SdS respectively. The CdS nanoparticles were embedded in a new PPV derivate named Fluorinated Bisphenol A P-phenylenevinylene (BPAF-PPV). Fourier transform infrared spectroscopy (FT-IR) showed a strong interaction of thiol groups with CdS nanoparticles. Blue shift of the optical absorption onset is observed due to quantum size effect. The band gap and particle sizes of the nanoparticles were deduced from optical absorption spectra and the use of an effective mass approximation (EMA) model. Photoluminescence spectroscopy evidenced a charge transfer process via the interface between BPAF-PPV/CdS nanoparticles.     

Silver–titanium dioxide nanocomposites as effective antimicrobial and antibiofilm agents

Recent studies have revealed the existence of liver cancer stem cells (CSCs). Therefore, there is an urgent need for new and effective treatment strategies specific to liver CSCs. In this work, the poly(d,l-lactide-coglycolide) nanoparticles containing paclitaxel were prepared by emulsification-solvent evaporation method. The nanoparticles decorated with anti-CD133 antibody, termed targeted nanoparticles, were prepared by carbodiimide chemistry for liver CSCs. The physicochemical characteristics of the nanoparticles (i.e., encapsulation efficiency, particle size distribution, morphology, and in vitro release) were investigated. Cellular uptake and accumulation in tumor tissue of nanoparticles were observed. To assess anti-tumor activity of nanoparticles in vitro and in vivo, cell survival assay and tumor regression study were carried out using liver cancer cell lines (Huh7 and HepG2) and their xenografts. Particle size of targeted nanoparticles was 429.26 ± 41.53 nm with zeta potential of ?11.2 mV. Targeted nanoparticles possessed spherical morphology and high encapsulation efficiency (87.53 ± 5.9 %). The accumulation of targeted nanoparticles depends on dual effects of passive and active targeting. Drug-loaded nanoparticles showed cytotoxicity on the tumor cells in vitro and in vivo. Targeted nanoparticles resulted in significant improvement in therapeutic response through selectively eliminating CD133 positive subpopulation. These results suggested that the novel nanoparticles could be a promising candidate with excellent therapeutic efficacy for targeting liver CSCs.     

Rhodamine B-Coated Gold Nanoparticles as Effective “Turn-on” Fluorescent Sensors for Detection of Zinc II Ions in Water

We designed a fluorescence resonance energy transfer system consisting of fluorophore Rhodamine B and gold nanoparticles for sensing of zinc ions in aqueous solution. The electrostatic attraction between positively charged N-atoms in Rhodamine molecules and negatively charged citrate corona of gold nanoparticles led to substantial fluorescence quenching. However, the quenching is switched off in the presence of zinc ions and therefore the system can be used as an effective “turn-on” fluorescence sensor. UV-Vis absorption, fluorescence spectroscopy, and transmission electron microscopy were used for sensor evaluation. The approach of “turn-on” fluorescence has real potential for sensing metallic ions in water.     

New highlights on degradation process of verdigris from easel paintings

Verdigris is a green copper organometallic pigment, widely used in paintings during the fifteenth and sixteenth centuries. With ageing, chromatic modifications like browning or darkening can be observed on those green painted layers. An original but crucial approach has been developed based on the characterization of a reference neutral verdigris pigment—anhydrous copper acetate—and model samples, made of verdigris and linseed oil. Samples have undergone artificial ageing (temperature, light) to reproduce the color change effect. They were analysed before and after accelerated ageing tests by a complementary set of classical techniques: colorimetry, electron paramagnetic resonance, X-ray absorption spectroscopy, and UV–visible absorption. Our experiments revealed that the incorporation of the verdigris pigment in linseed oil induces a transformation of the copper acetate bimetallic structure, with the formation of monomeric species. These monomers, however, are not directly responsible for the darkening. The chromatic alteration seems instead linked to the transient formation of Cu(I) in the copper complexes of the pigment/oil system. This formation could be initiated by ambient light absorption through ligand-to-metal charge transfer, which favors the decarboxylation of the copper complexes leading to the reduction of Cu(II) into Cu(I). Moreover, dioxygen can react with partially decarboxylated dimers to form peroxy-Cu dimer complexes that can be responsible for the darkening.