纳米结构分子吸附引起的表面增强拉曼散射研究

Surface enhanced Raman scattering of molecules adsorbed on metal nanostructures

利用模板印刷技术,制备了具有不同局域表面等离子体共振(LSPR)峰的Au纳米空心半球壳结构,并以4-巯基苯胺(4-ATP)为探针分子研究了纳米结构表面吸附分子对表面增强拉曼散射(SERS)强度的影响。结果表明,当纳米结构的LSPR峰位处于激发光波长的短波长或"马鞍型"位置时,SERS强度随吸附分子数的增加而增大;当处于长波长位置时,SERS强度呈现先增大后减小的趋势。利用分子吸附理论和纳米结构表面局域场强度变化,对此现象进行了解释。

The gold hollow-core semi-shell nanostructures with different localized surface plasmon resonance（LSPR）properties were fabricated by nanolithography technique through depositing gold film onto a cleaned glass support covered with a close-packed monolayer of 200nm diameter polystyrene（PS）spheres and subsequently by the removal of the PS spheres.The optical properties of gold nanostructures can be controlled by the deposition time.Then,using 4-aminothiophenol（4-ATP）as the probe molecule,the surface enhanced Raman scattering（SERS）signals of 4-ATP adsorbed on the gold nanostructures with different LSPR peak wavelengths were measured by Raman spectroscopy.The changes of SERS properties due to different number of adsorbed 4-ATP molecules are experimentally investigated.The results show that the SERS signal intensities depend on the LSPR properties of metal nanostructures and the numbers of adsorbed molecules.In the case of LSPR peak wavelength of the nanostructures located at the left side of ideal excitation wavelength arrangement or saddle type arrangement,the SERS intensity increases monotonically with the number of adsorbed molecules,the SERS intensity increases first and then decreases if the LSPR peak wavelength located at right side of the excitation wavelength.The changes of SERS intensities are ascribed to the local electric field excited by incident light and molecule adsorbed theory.