摘要/Abstract
等离激元纳米结构因其通过改变纳米结构的尺寸、形貌和组成成分，可以在紫外-可见-近红外范围内实现对光的操控从而提高能量利用率而受到人们的广泛关注.在光的激发下，等离激元纳米结构可以产生高能热电子，并驱动光化学反应，但其利用效率较低.因此，如何提升热电子的激发效率成为了一个亟待解决的关键问题.本工作制备了三维壳层隔绝银纳米粒子载金（3D Ag SHINs-Au）超结构，以对巯基苯胺（pATP）为探针分子，结合原位表面增强拉曼光谱技术和三维有限时域差分法研究不同电场强度对等离激元诱导的热电子激发效率的影响.实验结果显示电场强度越强，热电子激发效率越高，pATP催化速率越快.此外，带内跃迁比带间跃迁更有利于热电子的激发.本研究有助于人们理解电场强度如何影响热电子的激发效率.
关键词: 表面增强拉曼光谱, 等离激元, 热电子, 电场强度, 对巯基苯胺
The plasmonic nanostructures have attracted particular attention due to their superior ability to capture and modulate light in ultraviolet-visible and near-infrared range, by changing the size, morphology, and the composition of nanostructures. Especially in plasmon-driven chemical reactions, plasmon-induced hot electrons (HEs) can be transferred from the surface of metal nanostructures to the lowest unoccupied molecular orbital (LUMO) of the adsorbate molecule or the conduction band of the semiconductor to achieve catalytic reaction. Therefore, how to improve the excitation efficiency of HEs has become a key problem to be solved urgently. In this paper, 120 nm Ag nanoparticles (NPs) were synthesized by seed growth method using 45 nm Au as seed. Subsequently, (3-aminopropyl)trimethoxysilane as coupling agent and sodium silicate as the silicon source were used to prepare the shell-isolated Ag NPs with 2~3 nm SiO2 shell (Ag SHINs). Finally, Ag SHINs were modified with poly(allylamine hydrochloride), then small Au (ca. 15 nm) as satellites were electrostatic self-assembled onto the surface of Ag SHINs to form a 3D Ag SHINs-Au superstructure. Using p-aminothiophenol (pATP) as probe molecule, in-situ surface-enhanced Raman spectroscopy (SERS) was employed to real-timely monitor the catalytic reaction processes from pATP to DMAB, using 532, 638, and 785 nm lasers for excitation, respectively. The results showed that the highest conversion efficiency was achieved when 638 nm laser was applied. In addition, the reaction rate under 785 nm excitation was faster than that under exposure to 532 nm laser. Then, we used three dimensional (3D) finite-difference time-domain (FDTD) to simulate the electric field distribution of 3D Ag SHINs-Au superstructure. The electric field simulation results are consistent with the experimental results. In consequence, the stronger the electric field intensity, the higher the HEs excitation efficiency. On the other hand, the intra-band transitions produce HEs more efficiently than inter-band transitions. Therefore, this study is helpful for understanding how the electric field intensity affect the excitation efficiency of the HEs.
Key words: SERS, plasmonics, hot electrons, electric field intensity, p-aminothiophenol
PDF全文下载地址:
点我下载PDF
