金溶胶中邻羟基苯甲酸吸附行为的密度泛函理论与实验研究

摘要

研究了邻羟基苯甲酸(OHBA)的常规拉曼散射(NRS)光谱以及其吸附在Au纳米颗粒上的表面增强拉曼散射(SERS)光谱.以氯金酸为原料,柠檬酸三钠为还原剂,用化学还原法制备了球形的金纳米粒子溶胶,采用激光显微拉曼光谱仪(激发波长为785 nm),测定OHBA分子的NRS光谱及其吸附在Au纳米颗粒上的SERS光谱.同时,应用密度泛函理论(DFT),在B3LYP/6-31+G??(C,H,O)/LANL2DZ(Au)水平上,对OHBA分子进行了结构优化,在此基础上计算了OHBA分子的NRS光谱以及其吸附在Au纳米颗粒上两种不同吸附构型下的SERS光谱,并和实验值进行比较.结果表明,OHBA分子通过羧基吸附构型的计算值比通过羟基吸附构型的计算值与实验值符合的更好.最后,利用GaussView可视化软件对其振动模式进行了全面归属.通过对邻羟基苯甲酸分子拉曼谱峰的详细指认能够得出:Au溶胶中的邻羟基苯甲酸分子,是通过羧基倾斜地吸附在Au纳米颗粒表面的.可视化软件直观形象地展示出了该分子的结构特征和分子基团振动情况,对其振动峰位的归属提供了重要依据.本文工作对推进邻羟基苯甲酸在生物医药等领域进一步的应用具有重要作用.%In this paper,Normal Raman Scattering (NRS)spectroscopy of o-hydroxybenzoic acid (OHBA)and Surface-enhanced Raman Scattering (SERS)spectroscopy of OHBA adsorbed on gold nanoparticles were studied.The spherical gold nanoparticles were prepared by chemical reduction method with gold chloride acid as precursor and trisodium citrate as reductant.The NRS spectroscopy of OHBA and the SERS spectroscopy of OHBA adsorbed on gold nanoparticles were collected by laser Raman spec-trometer,and the laser beam (785nm)was used as the excitation light source.Meanwhile,density functional theory (DFT) method at the B3LYP/6-31 + G ? ? (C, H,O)/LANL2DZ (Au)level was used to optimize molecular configurations of o-hydroxybenzoic acid.Base on the optimized structure,the NRS spectroscopy of OHBA and the SERS spectroscopy by different adsorption configurations of OHBA adsorbed on gold nanoparticles were all calculated.Compared with the experimental data, the results showed that the calculation results using OHBA molecular adsorption configuration through carboxyl were much more matched with the experimental values than those of using OHBA molecules adsorption configurations through hydroxyl.At the end,comprehensive assignments of the vibration mode for OHBA were studied by GaussView.According to the identification analysis of OHBA molecular Raman peaks,it could be drawn that,in gold colloids,the OHBA molecule would be tipsily ad-sorbed on the surface of gold nanoparticles through the carboxyl.The visualization software displayed the structure characteris-tics and molecular group vibration of this molecular and provided important basis for assigning the vibrational peaks.This work has important effect on the further applications of o-hydroxybenzoic acid in biomedicine and other fields.