金膜表面等离激元诱导邻巯基苯甲酸脱羧反应的表面增强拉曼光谱研究

Surface Enhanced Raman Spectroscopic Investigation on SPR Catalyzed Decarboxylation of Ortho-Mercaptobenzoic Acid at Au Nanoparticles Monolayer Film

贵金属纳米结构表面等离激元共振(SPR)因其广泛的用途而备受关注,它不仅可以催化某些特殊的表面反应,同时还能产生表面增强拉曼散射效应(SERS),极大增强分子的表面拉曼信号,因此两者结合后可在纳米结构表面采用SERS光谱跟踪SPR催化反应。目前此类研究主要集中在氮氮(N N)偶联,因此亟待拓展SPR反应种类及提高催化活性和效率。采用SERS光谱研究邻巯基苯甲酸(OMBA)分子在金纳米粒子单层膜(Au MLF)表面的脱羧行为。通过气液界面组装法制备“热点”分布均匀的金纳米粒子单层膜,以此作为基底,探讨了溶液pH值、激光功率及激光照射时长对该基底表面脱羧反应的影响。研究结果表明,吸附在Au MLF表面的OMBA分子在表面等离激元驱动下碱性和中性介质中发生脱羧基反应,生成苯硫酚(TP),且碱性中反应活性大于中性溶液。在酸性介质中几乎不发生脱羧反应。较强的激光功率,脱羧反应的活性越高;产物SERS强度的增加与激光照射时间成线性关系,时间延长可提高脱羧反应的产率。这为拓展SPR驱动的光催化反应及深入理解其反应机理提供了实验依据。

The surface plasmon resonance(SPR)of noble metallic nanostructures has attracted considerable attention due to its wide application.It plays a dual roles in catalyzing special surface reactions and inducing surface-enhanced Raman spectroscopy(SERS)effect.For the latter,the surface Raman signal is enhanced dramatically.It allows monitoring the SPR catalysis reaction by SERS at nanostructures with extremely high sensitivity.However,the SERS investigation of SPR catalysis reaction is still significantly restricted to the N N coupling.The extension on the reaction type and improvement in the catalytic activity and efficiency are highly desired.Herein,the SERS technique is employed to investigate the decarboxylation reaction of Ortho-mercaptobenzoic acid(OMBA)adsorbed on Au nanoparticles monolayer film(Au MLF).The self-assembly fabricated the Au MLF at air/liquid interface,and it exhibited uniform distribution of“hot spots”.By using as substrate,the influence of solution pH,laser power and irradiation duration on the surface decarboxylation reaction was explored accordingly.The results demonstrated that the decarboxylation reaction of OMBA was occurred in the neutral or alkaline solution at Au MLF,and the product was thiophenol(TP).It was absent in the acidic solution and the activity of decarboxylation reaction activity in the alkaline solution was higher than that in the neutral solution.The stronger laser power brought the higher activity of decarboxylation.It indicated the linear relationship between the SERS intensities and laser irradiation duration,and the efficiency of SPR catalyzed decarboxylation was improved by prolonging the irradiation duration.The preliminary results are beneficial for extending the SPR catalyzed surface reaction and understanding of the surface reaction mechanisms.