表面荧光机制的理论研究

本文研究了 Rh B分子的 539.0 nm和 572 .5nm两荧光峰在表面增强活性银胶颗粒表面上的增强和淬灭效应 :在同一分子体系中同时观察到 530 .0 nm荧光峰的增强和 572 .5nm荧光峰的淬灭 ,并对其进行了理论计算。结果表明这两个荧光峰的增强或淬灭主要取决于局域电磁场增强和分子到金属表面无辐射能量转移衰减过程的竞争效应。当满足吸收共振增强和辐射共振增强时 ,荧光被增强 ;反之 ,荧光被淬灭。计算表明 ,荧光增强因子最高为 1     

银微粒表面吸附若丹明B分子荧光增强和淬灭的研究

研究了若丹明B分子的530.0和572.0nm两个荧光峰在银微粒表面的增强和淬灭效应,发现若丹明B分子的530.0nm荧光峰获得了30倍的增强,而与此同时,572.5nm荧光峰则强烈淬灭。对其快速动力学过程的研究表明,这两个荧光峰的增强和淬灭过程在每一时刻都是互逆的。 关键词：     

表面增强的分子间能量转移效应的机理研究

对吸附于粗糙金属银表面的分子间能量转移效应的机理进行了研究.采用电磁理论,讨论了金属银表面对分子间能量转移速率的影响.结果表明,当能量供体(D)分子的辐射频率和能量受体(A)分子的吸收频率同时与银表面等离子体激发频率共振时,分子间非辐射的能量转移速率被增强10~3—10~4倍.采用表面增强喇曼散射(SERS)活性表面-银胶,测量了吸附的2,2菁染料单体分子和J聚集体分子的荧光光谱,观察到的J聚集体分子增强的592.4nm的荧光带是通过被加速的分子间能量转移过程而产生的,从而证实了表面增强的分子间能量转移效 关键词：     

Synthesis and Adsorption Study of BSA Surface Imprinted Polymer on CdS Quantum Dots

开发了CdS量子点用于牛血清白蛋白(BSA)表面压印的方法,将CdS量子点掺杂进BSA的分子压印聚合物中. 实验过程中对制备条件和吸附条件进行了优化. 量子点(QDs)和量子点分子压印聚合物(QDs-MIP)的形貌用扫描电子显微镜进行了表征. 当该QDs-MIP重新结合模板分子BSA时,CdS量子点的荧光被淬灭. 荧光淬灭的原因可能是量子点与模板蛋白质分子之间的荧光共振能量转移. 该聚合物对压印分子的吸附为单分子层吸附,符合Langmuir等温吸附模型. 化学吸附为速率控制步骤. 该新型聚合物的最大吸附容量可达226.0 mg/g,比未掺杂量子点的BSA压印聚合物提高142.4 mg/g.     

高压拉曼光谱方法研究联苯分子费米共振

测量了0—15 GPa压强下联苯分子的拉曼光谱. 结果表明,随压强增加,分子内和分子间π-π共轭和离域效应增强,谱线的绝对强度变大、蓝移. 联苯分子的两费米共振谱线强度比R_f/a减少,频率差Δ增加,当压强为8 GPa时,费米共振现象消失,利用Betran理论得出了固有频率差Δ₀和耦合系数ω随压强的变化关系,通过高压下相变进行了解释,并探讨了高压下费米共振耦合变弱的机理. 关键词： 联苯 费米共振 高压 拉曼光谱     

金纳米粒子掺杂DNA-CTMA-DPFP薄膜的表面增强拉曼散射特性

采用柠檬酸三钠还原氯金酸和离子交换法制备金纳米粒子掺杂DNA-CTMA材料,利用钯催化反应合成9,9-二乙基-2,7-二-(4-吡啶)芴荧光染料(DPFP),将DPFP与DNA-CTMA混合后,旋凃制备金纳米粒子掺杂的DNA-CTMA-DPFP薄膜样品。通过吸收光谱、荧光光谱和拉曼光谱的测量,研究了薄膜样品的光学特性和表面增强拉曼散射(SERS)特性。实验结果表明,薄膜样品在300～360 nm的吸收主要来自DPFP,在500～700 nm的吸收来自样品中金纳米粒子的局域表面等离子共振;样品在370,386,408 nm处的荧光峰分别对应DPFP的S₁₀-S₀₀、S₁₀-S₀₁和S₁₀-S₀₂能级的电子振动跃迁;在785 nm激光激发下,薄膜样品的拉曼散射主要来自DPFP分子,随着金纳米粒子掺杂比的增大,DPFP分子的拉曼散射峰强度逐渐增强。因此,金纳米粒子掺杂DNA-CTMA薄膜适合作为多种染料分子的SERS基底。     

电场诱导氧化石墨烯的极化动力学特性研究

本文通过外加电场改变氧化石墨烯团簇分子的共振能量,利用激光激发氧化石墨烯产生的共振荧光特性测量氧化石墨烯在电场作用下的极化动力学特性. 发现存在外加电场使得荧光共振峰的半高全宽趋于饱和的时间特性,而不同的氧化石墨烯团簇分子的荧光共振峰的暂态特性同时反映了电场对氧化石墨烯产生定向极化和变形极化的动力学特性. 关键词： 氧化石墨烯 团簇分子 电场 极化动力学     

不同表面修饰和尺寸的纳米银的荧光增强效应的研究

分别以柠檬酸钠(CTS)和聚乙烯吡咯烷酮(PVP)为表面修饰剂,采用化学法制备纳米银(分别标记为Ag-CTS和Ag-PVP)。当甲基橙溶液中加入Ag-CTS或Ag-PVP时,S₂→S₀和S₁→S₀荧光强度分别明显减弱和增强。不同的是Ag-PVP引起S₂→S₀和S₁→S₀荧光强度减弱和增强的幅度更大,且S₂→S₀荧光峰出现红移。当甲基橙溶液中加入Ag-CTS时,S₁→S₀荧光强度随时间延长逐渐增强,而加入Ag-PVP时,S₁→S₀荧光强度则不随时间而变化。颗粒尺寸较大的片状结构纳米银引起S₁→S₀荧光强度增强比率较小。甲基橙溶液浓度越低,S₁→S₀荧光强度增强比率越大。研究结果表明,纳米银表面吸附的不同表面修饰剂通过影响纳米银与甲基橙分子间距离进而影响纳米银的荧光增强效应;纳米银尺寸大小则由于所产生的局域面表面等离子共振特点等差异影响其局域场增强效应。     

粒子等离子共振对有机半导体共混体系中激发复合体荧光发射的作用

研究了具有局域等离子共振特性的金纳米岛状结构阵列对高分子材料共混体系中激发复合体荧光发射特性的影响.实验结果表明,当粒子等离子共振发生在激发复合体荧光光谱区时,其荧光发射的强度得到了显著增强,且荧光寿命也得以延长.可以认为,粒子等离子共振诱发的局域场增加了激子的扩散距离,利于在相分离界面处激发复合体的形成. 关键词： 金纳米岛状结构 粒子等离子共振局域场增强效应 聚合物共混体系 激发复合体     

核黄素/银溶胶体系的吸收光谱和表面增强共振喇曼光谱

利用可见紫外吸收光谱和表面增强共振喇曼散射光谱(SERRS)研究了核黄素和银胶颗粒的相互作用。不仅有效地淬灭了黄素发色团的荧光干扰,而且还使其喇曼散射得到显著增强。对SERRS进行了分析和指认,SERRS结果揭示出,黄素发色团与银胶颗粒相互作用所形成的络合物,不同于与银离子所形成的络合物。利用这一方法还得到1000cm^-1以下的喇曼带,这些带多与发色团的环呼吸振动和C—H面外变型振动有关。 关键词：     

Enhancement of Secondary Radiation of Chromophores Adsorbed on the Rough Surface of Thin Silver Films under Conditions of Resonance Excitation

The spectra of giant Raman scattering of light and surfaceenhanced fluorescence of certain chromophores absorbing light in the visible spectrum region are investigated. The factors that have an effect on the enhancement of secondary radiation of chromophores adsorbed on the surface of rough silver films under conditions of resonance excitation are determined. The spectra of mirror reflection of light by the substrates used are considered. The coefficients of diffuse and mirror reflection, absorption, and transmission of light by thin silver films at wavelengths of 488 and 633 nm are determined. The scheme of an experimental system for observation of the spectra of giant Raman scattering and surfaceenhanced fluorescence on the source side of a transparent substrate is proposed. Conclusions on the predominant contribution of the resonance excitation of surface plasmons to the enhancement of the signal of the giant Raman scattering and surfaceenhanced fluorescence of molecules adsorbed on the rough metal surface are drawn.     

维生素K3的表面增强拉曼光谱研究

首次报道了维生素K3 (VK3 )分子的常规拉曼光谱 (NRS)及该分子在活性衬底银镜上的表面增强拉曼散射 (SERS) ,并对它的拉曼特征谱带进行了初步的指认和归属。通过对比VK3 的常规拉曼光谱和SERS谱 ,发现VK3 分子吸附在银表面后拉曼散射强度被大大增强了。另外 ,VK3 的羰基与银粒子发生电荷转移后形成负离子自由基 ,碳氧双键打开。受VK3 分子吸附在银镜表面的影响 ,萘环结构发生了很大的扰动 ,导致一些拉曼特征峰产生位移 ,环变形振动对应的拉曼散射强度得到了增强。这些研究结果为SERS技术今后对VK3进行药物检测以及痕量分析方面的应用提供了依据。     

STUDY OF HOMOGENEOUS ADSORPTION KINETICS OF CRYSTAL VIOLET

The adsorption kinetica of crystal violet (CV) on silver mirror and two different kinds of silver sols is studied. The adsorption of CV on silver is homogeneous. It is confirmed that the topography of the surface affects only adsorption rate constant, while it does not change heterogeneity parameter. The similar behavior of enhancement factor and adsorption rate constant of CV in the two silver sols is discussed. The adsorption energy of CV and the concentration of adsorbed sites on the surface are estimated by adsorption isotherm. It is found that the enhancement effect on the silver mirror is determined by the concentration of adsorbed sites on surface.     

Surface plasmons for fluorescence enhancement in Sm-doped borate glasses

Heat treatment of Sm-activated lithium and sodium borate glasses which are additionally doped with silver oxide leads to a reduction of the doped silver ions and to the formation of metallic silver nanoparticles indicated by a broad plasmon-related absorption band in the visible spectral range. The influence of the plasmon resonance field enhancement on the Sm³⁺ fluorescence excitation bands is too small to lead to enhanced fluorescence emission intensities.     

Synthesis of indium–silver bimetallic nanocomposites for surface-enhanced Raman scattering

We report on the synthesis of indium–silver bimetallic nanocomposites by chemical reduction method under atmospheric condition and their activity for surface-enhanced Raman scattering (SERS). It is found that the indium–silver bimetallic nanocomposites have better SERS activity with larger enhancement factors (EF) than pure silver nanoparticles with similar size. The SERS EF can reach 10⁷ for 4-mercaptobenzoic acid and 10⁹ for crystal violet and rhodamine 6G adsorbed on the nanocomposites and the detection limits can be at least down to 10^?7 and 10^?10 M, respectively. The results demonstrate that the indium–silver bimetallic nanocomposites are promising as SERS substrate for a myriad of chemical and biological sensing applications.     

Electromagnetic interaction of fluorophores with designed two-dimensional silver nanoparticle arrays

We study the fluorescence enhancement of dye molecules adsorbed on regular two-dimensional arrays of designed silver nanoparticles. The silver particles show two orthogonal optical resonances at different wavelengths because of their elongated shape. The short-wavelength resonance was designed to fit to the absorption maximum of the fluorophore. When the excitation light drives the short-wavelength resonance, the measured fluorescence intensity is strongly enhanced compared to that for the orthogonal particle orientation. This shows directly a strong electromagnetic coupling between the nanoparticles and the fluorophore. Additionally enhanced photochemical bleaching is observed due to the interaction of fluorophores with the particles. Using a rate model describing the fluorescence enhancement and the bleaching enhancement, an average value for the particle-induced increase in the radiative fluorescence rate is obtained, together with a lower limit for the averaged particle-induced field intensity enhancement factor. Received: 3 July 2001 / Revised version: 3 September 2001 / Published online: 15 October 2001     

多孔硅银淀积表面RhB染料分子的表面增强Raman散射

我们采用多孔硅和多孔硅银淀积表面作为衬底研究了ＲｈＢ染料分子的表面增强Ｒａ ｍａｎ散射。在多孔硅表面,ＲｈＢ染料分子的Ｒａｍａｎ散射有大约１０倍的表面增强效果;而在多孔硅的银淀积表面,表现出超过１０４表面增强。通过多孔硅表面银颗粒对ＲｈＢ染料分子荧光的抑制和对Ｒａｍａｎ散射的表面增强,我们获得了谱峰清晰的ＲｈＢ染料分子Ｒａｍａｎ散射谱     

Theoretical elucidation of the origin of surface‐enhanced Raman spectra of PCB52 adsorbed on silver substrates

To better understand experimentally observed surface‐enhanced Raman Scattering (SERS) of polychlorinated biphenyls (PCBs) adsorbed on nanoscaled silver substrates, a systematic theoretical study was performed by carrying out density functional theory and time‐dependent density functional theory calculations. 2,2′,5,5′‐tetrachlorobiphenyl (PCB52) was chosen as a model molecule of PCBs, and Ag_n (n = 2, 4, 6, and 10) clusters were used to mimic active sites of substrates. Calculated normal Raman spectra of PCB52–Ag_n (n = 2, 4, 6, and 10) complexes are analogical in profile to that of isolated PCB52 with only slightly enhanced intensity. In contrast, the corresponding SERS spectra calculated at adopted incident light are strongly enhanced, and the calculated enhancement factors are 10⁴ ~ 10⁵. Thus, the experimentally observed SERS phenomenon of PCBs supported on Ag substrates should correspond to the SERS spectra rather than the normal Raman spectra. The dominant enhancement in Raman intensities origins from the charge transfer resonance enhancement between the molecule and clusters. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhancement of Raman scattering of light by ultramarine microcrystals in presence of silver nanoparticles

Approximately 10²‐fold enhancement of Raman scattering by ultramarine microcrystals is reported by means of interaction with silver nanoparticles in films and powders. Theoretical modeling predicts the maximal 10¹⁰‐fold enhancement in close vicinity of a silver spherical nanoparticle (0.24 nm) with rapid decay of enhancement factor to 1 in the range of approximately 50 nm. Experimental enhancement factor is treated as overall effect within the small portion of every microcrystal in the close vicinity of silver nanoparticle(s). The results are considered as an important extension of traditional surface enhanced molecular Raman spectroscopy towards bigger inorganic probes. Copyright © 2012 John Wiley & Sons, Ltd.     

Quenching and enhancing of SERS of methyl orange after the addition of chlorine and nitrate anions

The influence of Cl⁻ and NO₃⁻ anions on surface enhanced Raman scattering (SERS) of methyl orange adsorbed on “chemical pure” silver colloids was studied. It was found that NO₃⁻ could give rise to a large enhancement of SERS of methyl orange, while Cl⁻ could obviously weaken the SERS intensity of this molecule. Both quenching and enhancing effects were discussed and compared with each other. It indicated the coadsorbed process of these adsorbed species, and different adsorption behaviors of the molecules on silver surface directly resulted in the difference. In addition, the results of TEM pictures and UV-visible spectral experiments have also confirmed the conclusion above.