Surface-Enhanced Raman Spectroscopy Study Of Hexanethiol Self-assembled Monolayer And Surface-Hybrid Monolayer Films

In this paper, SERS was used to study the adsorption and assembly process of HT (hexanethiol) on silver substrate. Meanwhile, the surface was hybridized after silver nanoparticles were embellished on HT so as to study SERS spectrum. According to the characteristic spectrum information of trans form and gauche form of C-S, C-C and CH3 structures, and identification on the Raman of HT and SERS spectrum of self-assembled film, the conformation of HT adsorbed on the surface of silver nanoparticle was studied, including the structural order of self-assembled film. Besides, impact of adsorption time and concentration on the law of film formation was studied. After HT molecule was embellished, a layer of probe molecules were adsorbed to have surface hybridization, by which some interesting phenomena were reached. See the details as follows:(1) When HT was adsorbed on silver nanoparticle, several characteristic peaks of HT molecule were understood by spectrum identification. These groups of characteristics were the key characteristic peaks were about the orientation of HT molecule on the surface adsorption of silver nanoparticle. By measuring the peak intensity of spectrum, it was found that the adsorption state of HT molecule tended to an ordered structure gradually in 4 h when the concentration was high. However, when the adsorption time was increased to a certain extent, the ordering of HT would be damaged. Meanwhile, it was found by observing the adsorption at different concentrations that the formation speed of single film was fast when the concentration was high, and the ordering was good. However, the formation speed of film was slow when the concentration was low, and the ordering was poor.(2) When HT was embellished, PATP and MPY adsorbed on the surface were hybridized. First, when PATP was adsorbed on silver nanoparticles where HT molecule was embellished, SERS spectrum of PATP could be seen clearly from the spectrum. Besides, after the ordering of HT molecule was damaged, the damaged HT film on the layer where PATP was adsorbed was ordered. In addition, when MPY was adsorbed on silver nanoparticles where HT was embellished, SERS characteristic peak of MPY could be seen from the spectrum. Besides, it was found that there was S-H vibration, and the relative intensity of 8b2 and 8a1 changed. The research above showed that HT exists functionally when the surface is hybridized, and it can be demonstrated by the spectrum of MPY that MPY is adsorbed on the single-layer film surface of HT.