金银合金纳米粒子表面处理及其表面增强拉曼光谱研究

采用水合肼还原的方法制备了金银比例为1∶1的金银合金纳米粒子, 紫外可见吸收光谱显示合成的溶胶只有一个介于金和银之间的吸收峰, 证明了合金结构的形成. 通过氨基耦联方法将合金纳米粒子组装到硅片表面, 利用氯金酸与合金中银的反应对基底上合金纳米粒子表面进行了改性处理. 以吡啶为探针分子, 研究了表面处理前后基底的SERS效应的差别, 结果表明随着浸泡时间延长, 信号强度先逐渐增强后降低至不变, 这与合金纳米粒子表面结构的变化有关, 氯金酸与表面银的反应经历了两个过程, 即粒子表面形成小的孔洞(去合金过程)和AgCl(s)在粒子表面的沉积, 前者有利于SERS效应的提高, 而后者导致SERS效应快速衰减.

Au/Ag alloy; surface treatment; pyridine; surface enhanced Raman spectroscopy

Au-Ag alloy nanoparticles with an atomic ratio of 1∶1 were synthesized by using hydrazine as a reducing agent, and the as-prepared nanoparticles were then assembled on silicon substrate. The surfaces of alloy nanoparticles were treated by immersion into a solution of HAuCl4 to dissolve some Ag atoms from the alloy nanoparticles. With pyridine as the probe, the difference in the SERS effect on the alloy nanoparticles was investigated before and after the surface treatment processes. The results revealed that the SERS signals increased initially and then decreased with the immersion time. The time dependence was mainly attributed to the change of surface micro-structures of the alloy nanoparticles. The surface reaction of the Au-Ag nanoparticles with HAuCl4 underwent two processes involving the formation of surface pinhole (dealloying) and the deposition of AgCl(s) on surface. The former promoted the SERS effect, while the latter attenuated the SERS effect.