不同粒径金纳米微粒对荧光素钠的猝灭效应研究

采用柠檬酸盐合成法制备了不同粒径的金纳米微粒,用吸收光谱和透射电镜对金纳米微粒进行了表征。研究了不同粒径金纳米微粒与荧光素钠分子的相互作用。发现金纳米微粒对荧光素钠具有荧光猝灭效应, 并且其荧光猝灭程度与金纳米微粒的粒径大小有关。随着金纳米微粒粒径的减小,荧光猝灭程度增大。探讨了金纳米微粒对荧光素钠荧光猝灭的机理,表明该荧光猝灭为动态猝灭。     

银纳米粒子对抗生素诺氟沙星的荧光猝灭效应

以β-环糊精(β-CD)为稳定剂,葡萄糖为还原剂,采用"绿色化学方法"合成了平均粒径约为31nm的类球形银纳米粒子。研究了其对水溶液中痕量诺氟沙星荧光行为的影响,实验结果表明,制得的银纳米粒子对诺氟沙星具有较强的荧光猝灭效应,且随着加入银纳米粒子量的增加荧光猝灭效果逐渐增强。初步探讨了银纳米粒子对诺氟沙星的荧光猝灭机理。     

空穴传输材料对CdSe核壳量子点的荧光影响

用稳态光谱和时间分辨光谱技术研究了空穴传输材料对CdSe/ZnSe 与CdSe/ZnS核壳量子点的荧光影响。结果表明,空穴传输材料对量子点有较强的猝灭作用,随空穴传输材料分子浓度的增加,量子点的荧光强度明显地被猝灭,同时量子点的荧光寿命也被减短。两种不同空穴传输分子对CdSe/ZnSe量子点的荧光猝灭明显不同。在与相同空穴传输分子相互作用时,包覆ZnS壳层的CdSe核壳量子点荧光猝灭效率明显低于包覆ZnSe壳层的CdSe核壳量子点。量子点的荧光猝灭过程可以解释为静态猝灭和动态猝灭过程,其中静态猝灭来源于量子点表面与空穴传输材料间相互作用,而动态猝灭则主要来源于量子点到空穴传输材料的空穴转移过程。实验结果表明空穴传输材料的种类以及核壳量子点的壳层结构都对其荧光猝灭效应起关键作用。     

基于超分子结构共掺杂纳米复合薄膜的制备与荧光特性

为改善功能分了的特性,提出一种基于金属纳米粒子-偶氮染料复合物共掺杂超分子结构功能材料的设计新方法.并依照此方法制备出复合材料,观测了其显微结构,测量了其紫外-可见光吸收,研究了该超分子结构复合体系的荧光特性.实验发现,由于金属银纳米粒子的掺杂,使得超分子结构复合体系中功能分子甲基橙在溶液态体系的荧光强度增强近5倍,而在两种不同结构(共混结构和包覆结构)的薄膜态超分子结构体系中,其荧光强度分别被猝灭15%和20%.研究结果表明,复合膜中采用超分子结构完全能够改善功能分子的特性.     

L-半胱氨酸修饰的金纳米粒子与牛血清白蛋白相互作用的荧光光谱研究

采用荧光猝灭光谱和同步荧光光谱研究了L-半胱氨酸修饰的金纳米粒子(Cys-GNPs)与牛血清白蛋白(BSA)间的相互作用。根据荧光猝灭相关方程计算了Cys-GNPs与BSA相互作用的结合常数和结合位点数,探讨了其荧光猝灭机制为静态猝灭,并且根据热力学参数确定了二者间的作用力类型,推断出Cys-GNPs和BSA间主要靠疏水作用力结合。同步荧光光谱表明,二者的相互作用没有导致牛血清白蛋白的构象及色氨酸残基的微环境发生明显变化。     

纳米金膜及金壳表面局域等离激元对 上转换荧光波长的选择调控

基于贵金属表面局域等离子体共振(LSPR)调控上转换荧光的研究绝大部分集中于纳米颗粒或纳米棒,即使同一复合结构对上转换荧光(UCL)也有或增强或猝灭的截然相反的报道,而对于进一步提高上转换荧光材料的效率和强度以满足更广泛的应用需求则越来越引起人们高度关注。本文通过构筑两种纳米金/上转换纳米晶复合结构,系统研究了各自的表面局域等离激元对上转换荧光的增强和猝灭效应,基于微结构表征及对稳态、瞬态荧光光谱的分析,阐述了波长依赖的上转换荧光增强和猝灭机理。结果显示超薄纳米金壳结构对Ho~(3+)、Fe~(3+)共掺杂纳米晶的绿光发射选择性地增强了25倍,源于激发光能量与LSPR能量匹配的激发增强机制,而在覆盖有超薄纳米金膜的上转换纳米晶复合结构中却观察到了金膜引起的Er上转换荧光猝灭,同时红绿比随金膜厚度增加而增大,来自于金膜对激发光的散射、金膜的LSPR吸收带与绿光发射能级耦合引起无辐射跃迁几率增加,绿光上转换荧光强度下降相对显著,UCL寿命变短。     

CdSe/ZnSe核-壳结构纳米粒子合成新方法

报道用“一步”合成新方法制备了CdSe/ZnSe核-壳结构的发光纳米粒子.该方法是将锌的前驱体注入表面Se富集的CdSe发光纳米粒子溶液中,通过Zn²⁺与Se共价键结合,从而在CdSe发光纳米粒子的表面形成ZnSe壳.分别通过X射线粉末衍射、光电子能谱、透射电镜、紫外-可见吸收光谱和光致发光光谱,对核-壳结构的发光纳米粒子的结构及光学性质进行了表征.结果表明,以较宽带隙的ZnSe在较窄带隙的CdSe纳米粒子表面形成的壳层有效地钝化了CdSe纳米粒子的表面缺陷,明显地提高了室温下CdSe纳米粒子的光致发光效率.X射线粉末衍射表明随着Zn²⁺的不断注入,CdSe/ZnSe的衍射峰逐渐移向ZnSe衍射峰.光电子能谱数据显示,Zn2p的双峰分别位于1020,1040eV附近,通过与体材料ZnO相比,确定为Zn²⁺的光电子发射,说明Zn是以共价键形式存在于CdSe纳米粒子的表面.透射电镜照片显示纳米粒子具有良好的单分散性,核-壳结构的发光纳米粒子直径较CdSe核的直径明显增加.     

纳米银组装结构上罗丹明B的表面增强荧光效应

采用表面自组装技术,在玻璃表面构筑银纳米粒子的二维组装结构。银纳米粒子组装结构的表面等离子共振光谱中偶极子表面等离子体共振对组装结构更为敏感而表现出较大位移。组装银纳米粒子可极大增强罗丹明B的荧光。荧光的表面增强效应主要来自银纳米粒子对荧光分子所处区域的局部电磁场增强,银纳米粒子的表面分子修饰对其表面增强效应有较大的影响。     

银纳米粒子与R6G分子间的电荷转移

本文通过吸收光谱、表面增强垃曼光谱、荧光光谱等手段研究了银纳米粒子与罗丹明6G（R6G）分子之间的相互作用,结果表明：银纳米粒子表面与R6G分子之间存在电荷转移效应。表现为吸收谱长波方向出现银粒子－R6G复合体的吸收带,R6G分子的拉曼振动模得到显著增强,而其荧光得到明显猝灭;AgN特征拉曼振动带的出现服银米粒子与R6G分子是通过银粒表面的活位与R6G分子中的氮原子配位形成复合体而发生电荷转移的。     

基于NaGdF_4∶Eu纳米粒子的荧光猝灭测定痕量Cu~(2+)

采用水热法合成了柠檬酸盐修饰的水溶性NaGdF4:Eu荧光纳米粒子,粒子溶液荧光强度稳定.实验发现,Cu2+外对合成粒子的荧光有猝灭作用,据此可建立用NaGdF4:Eu荧光探针测定痕量Cu2+的新方法.实验确定NaGdF4:Eu的浓度为1.0×10-3 mol·L-1,溶液的pH值为10.0.考察了其他常见离子对粒子荧光性能的影响,其中Fe3+使荧光发生猝灭,用三乙醇胺可消除Fe3+的干扰.标准曲线的线性回归方程为I=532-0.685c,相关系数r为-0.998 4,线性范围为3.33×10-6～1.33×10-4 mol·L-1,检出限为8.9×10-7 mol·L-1,对浓度为6.0×10-5 mol·L-1的Cu2+溶液平行测定11次,RSD为0.62%.以上结果表明,方法的线性范围较宽,灵敏度和精密度较高.测定了茶叶样品中铜含量,测定结果和原子吸收法测定结果相一致.分析Cu2+对粒子荧光猝灭的机理认为,Cu2+和粒子表面的柠檬酸根发生化学结合,改变了粒子表面的结构和组成,导致其荧光发生猝灭.     

Single-molecule measurements of gold-quenched quantum dots

We report the study of the quenching of quantum dots (CdSe) by gold nanoparticles at the single-molecule level. Double-stranded DNA is used as a rigid spacer to tune the distance between the two nanoparticles. The width of the fluorescent intensity distribution, monitored at different interparticle distances, reflects both the nanoparticle heterogeneity and the fluorescence intermittency of the quantum dot. The fluorescence distribution emitted by single CdSe nanocrystals can easily be distinguished from the fluorescence of partially quenched CdSe. Our results show that the distance-dependence quenching is compatible with a F?rster-type process.     

Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al_2O_3/Au nanoparticles

We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al_2 O_3 film modified by gold nanoparticles. The photoluminescence(PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy(SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al_2 O_3 nanopores are combined with the carboxyl of CdSe quantum dots' surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al_2 O_3 film. Compared with the area of nonself-assembled nano-wire, the fluorescence on the Al_2 O_3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles' surface. In addition, its full width at half maximum(FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.     

Fluorescence properties of a composite material based on the 5CB nematic liquid crystal with gold nanoparticles

The steady-state and time-resolved fluorescence spectra of n-pentyl-n′-cyanobiphenyl and a related composite material with gold nanoparticles in the liquid crystalline and solid states have been investigated. The introduction of gold nanoparticles into the liquid crystal leads to a noticeable quenching of fluorescence in the emission region of the predimer and excimer states of cyanobiphenyl. In the solid phase, a quenching of free excitons and a short-wavelength shift of fluorescence bands have been observed.     

油溶性CdSe量子点荧光探针直接检测农药水胺硫磷

基于农药水胺硫磷对油溶性CdSe量子点荧光猝灭的现象,建立了一种简单、快速、直接检测农药水胺硫磷的新方法。在最佳实验条件下,油溶性CdSe量子点的荧光猝灭程度与水胺硫磷浓度在2.30×10-7～1.09×10-5 mol·L-1范围内呈较好的线性关系,相关系数为0.999 9,对水胺硫磷的检出限为1.1×10-7 mol·L-1。本法已成功用于大米和小麦面粉样品中水胺硫磷农药残留的检测,加入回收率在93.3%～105.0%之间,结果满意。结合紫外-可见吸收光谱及时间分辨荧光光谱,探讨了水胺硫磷对油溶性CdSe量子点荧光猝灭的机理。研究结果表明,水胺硫磷能有效改变油溶性CdSe量子点的表面状态,增大了表面缺陷和非辐射重组的发生,从而使油溶性CdSe量子点的荧光猝灭。     

CdSe/ZnS Fluorescent Nanoparticles as Nanoprobes of Local pH in Diagnostics of Oncology

We discuss the fluorescence spectra from a set of points in histological sections of colon tissue with different levels of pathology that were stained with hydrophilic semiconductor CdSe/ZnS nanoparticles that were modified by a unique method at the phase interface. The shifts in the fluorescence spectra that were recorded for stained cells at different pathologies are described using the electrochromism of the nanoparticles. Aqueous solutions of the CdSe/ZnS nanoparticles with different pH values are used as systems that model the acidity of a biological medium. It has been shown that the shifts of the fluorescence bands of the CdSe/ZnS nanoparticles are caused by a change in the local electrical field that is induced by solvated ions near their surface at different pH values of the solutions. The application of the CdSe/ZnS nanoparticles as nanoprobes for the local pH in biological tissue is discussed in the context of this model.     

Size-dependent interaction of gold nanoparticles with transport protein: A spectroscopic study

Gold nanoparticles of different sizes have been synthesized using sodium citrate as a reducing agent for tetrachloroauric (III) acid. The formed gold nanoparticles have been characterized by the UV-visible and transmission electron microscopy (TEM) measurements. The different sized gold nanoparticles have been used to study the interaction with model transport protein, bovine serum albumin (BSA). Experimental results reveal that BSA molecules adsorbed on the metallic surfaces, suffer strong quenching of their fluorescence and the rate of quenching efficiency is different for different particle size. The analysis of the quenching results has been performed in terms of the Stern-Volmer equation. The mechanism of quenching of fluorescence has been explained. The extent of adsorption of BSA on the gold nanoparticles has been estimated.     

Quenched Emission of Fluorescence by Ligand Functionalized Gold Nanoparticles

A fluorescence-based detection scheme that uses ligand functionalized gold nanoparticles is proposed. The transduction scheme is based on the strong quenching of the fluorescence emission exerted by metallic surfaces on fluorophores positioned in their immediate vicinity (< 5 nm). Binding of fluorophore-labeled anti-biotin to biotinylated gold nanoparticles resulted in decreased fluorescence emission intensity. Subsequent competitive dissociation of labeled anti-biotin with D-biotin resulted in increased fluorescence emission intensity. These interactions occurred by means of specific molecular recognition because when the binding sites of anti-biotin were saturated with D-biotin prior to interaction with the gold nanoparticles; changes in the fluorescence emission intensity were not observed.     

Femtosecond time-resolved energy transfer from CdSe nanoparticles to phthalocyanines

The first real-time observation of the early events during energy transfer from a photoexcited CdSe nanoparticle to an attached phthalocyanine molecule are presented in terms of a femtosecond spectroscopic pump–probe study of the energy transfer in conjugates of CdSe nanoparticles (NPs) and silicon phthalocyanines (Pcs) with 120 fs time resolution. Four different silicon phthalocyanines have been conjugated to CdSe NPs. All of these have proven potential for photodynamic therapy (PDT). In such NP-Pc conjugates efficient energy transfer (ET) from CdSe NPs to Pcs occurs upon selective photoexcitation of the NP moiety. Spectral analysis as well as time-resolved fluorescence up-conversion measurements revealed the structure and dynamics of the investigated conjugates. Femtosecond transient differential absorption (TDA) spectroscopy was used for the investigation of the non-radiative carrier and ET dynamics. The formation of excitons, trapped carriers states, as well as stimulated emission was monitored in the TDA spectra and the corresponding lifetimes of these states were recorded. The time component for energy transfer was found to be between 15 and 35 ps. The ET efficiencies are found to be 20-70% for the four Pc conjugates, according to fluorescence quenching experiments. Moreover, as a result of the conjugation between NP and the Pcs the photoluminescence efficiency of the Pc moieties in the conjugates do not strictly follow the quantum yields of the bare phthalocyanines. PACS 73.63.Bd