Investigations on nanoparticle-chromophore and interchromophore interactions in pyrene-capped gold nanoparticles
Investigations on nanoparticle-chromophore and interchromophore interactions in pyrene-capped gold nanoparticles
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DOI：
10.1021/jp048321a
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发表时间：
2004-09-02
影响因子：
3.3
通讯作者：
Thomas, KG
中科院分区：
文献类型：
--
作者：
Ipe, BI;Thomas, KG
将三种具有不同长度柔性烷基的芘烷醇衍生物（P1、P2和P3）与十二烷醇（Au-P1、Au-P2和Au-P3）一起沿着在金纳米颗粒（尺寸约2 -3 nm）上。研究了这些体系的光物理性质随发色团与金核的距离、金表面芘浓度和溶剂极性的变化。在金纳米颗粒（Au-P1）表面附近，芘发色团的结构吸收带发生了明显的扰动，表明Au纳米颗粒的等离子体激元电子与发色团的π电子云之间存在较强的基态相互作用.在Au-P2和Au-P3系统中没有观察到这种效应，其中连接基团足够长以防止任何基态相互作用。随着间隔基长度的增加，芘发色团正常荧光带III/I的峰强度比逐渐增加。这些结果表明，与本体介质相比，靠近An纳米颗粒表面的局部环境更具极性。在Au-P1体系中，由于球形金纳米粒子的曲率限制，发色团间的相互作用受到限制，而Au-P2/Au-P3体系中的柔性烷基链束缚芘则允许发色团间自由相互作用。稳态和时间分辨发射光谱研究表明，在非极性溶剂中，正常荧光和分子间激基缔合物的形成是芘单重激发态的主要失活途径.相反，在极性溶剂中，竞争性电子转移到金纳米核占主导地位。
Three pyrene alkanethiol derivatives (P1, P2, and P3) possessing flexible alkyl groups of different lengths were attached to nanoparticles of gold (similar to2-3 nm in size) along with dodecanethiol (Au-P1, Au-P2, and Au-P3). The photophysical properties of these systems were investigated as a function of (i) distance of chromophore from gold core, (ii) concentration of pyrene on gold surface, and (iii) solvent polarity. The structured absorption bands of the pyrene chromophore were significantly perturbed near the surface of gold nanoparticles (Au-P1), indicating a strong ground state interaction between the plasmon electrons of Au nanoparticles and thepi-electron cloud of the chromophore. Such effects were not observed in Au-P2 and Au-P3 systems, in which the linker groups are long enough to prevent any ground state interactions. A gradual increase in the peak intensity ratio of band III/I of the normal fluorescence of pyrene chromophore was found with an increase in length of the spacer group. These results indicate that the local environment close to the surface of the An nanoparticle is more polar compared to the bulk medium. Interchromophoric interactions are limited in the Au-P1 system due to the restriction imposed by the curvature of spherical gold nanoparticle whereas the flexible alkyl chain tethering pyrene in Au-P2/Au-P3 allows free interaction between chromophores. Steady state and time-resolved emission studies indicate that the normal fluorescence and intermolecular excimer formation are the main deactivation channels of the singlet excited state of pyrene linked to An nanoparticles, in nonpolar solvents. In contrast, the competitive electron transfer to the gold nanocore dominates in polar solvents.