苯硫酚吸附在新型Ag-Au合金纳米粒子上的表面增强拉曼光谱研究

Surface-Enhanced Raman Spectroscopic Studies on the Thiophenol Adsorbed on Novel Ag-Au Alloy Nanoparticles

以柠檬酸钠同时还原制备的Ag-Au合金纳米粒子为种子,用盐酸羟胺进一步使其生长得到粒径为40～60nm的新型Ag-Au合金纳米粒子,采用UV-Vis光谱和TEM对纳米种子和再生长后的纳米粒子分别进行表征。两种粒子的UV-Vis光谱均只观察到一个等离子体共振峰,其频率随金的摩尔分数(xAu)增加而红移,且TEM图像表明这两种粒子的颜色均一,因此判断这两种粒子均为合金结构。以苯硫酚为探针分子,研究了该新型合金纳米粒子的表面增强拉曼光谱(SERS),结果表明吸附了苯硫酚的合金纳米粒子的紫外最大吸收峰红移,并在近红外区出现聚集体的吸收峰。在632·8nm波长激发下,由于表面等离子体共振效应Au上的SERS信号最强,而合金纳米粒子上的SERS信号随xAu增大而增强。

Ag-Au alloy seeds were prepared by the simultaneous reduction of Ag and Au salts. The seeds were grown via NH2OH ·HCl-growth method to obtain novel Ag-Au alloy nanoparticles with diameters of 40-60 nm. The nanoseeds and novel nanoparticles were characterized by UV-Vis spectroscopy and TEM respectively. The observation of one surface plasma resonance absorption band, the redshift in their frequencies, and the uniform color of the nanoparticles shown in TEM images indicated the formation of alloy structure for both the nanoseeds and the novel nanoparticles. By using thiophenol（TP） as probe molecules, SERS studies were performed on the novel nanopartlcles. The absorption bands of the nanoparticles red shifted with the addition of TP, and new bands were detected in the near infrared region, which were attributed to the aggregation of TP covered nanoparticles. With the excitation line of 632. 8 nm, the SERS intensity of TP on Au was most largely enhanced, and that on alloy nanoparticles were increased as XAu increased.