三明治结构纳米银/氧化石墨烯基底的制备及SERS性能

采用易操作且低成本的静电自组装方法, 在质子化的玻璃基片上, 通过交替沉积氧化石墨烯(GO) 和带正电荷的银纳米粒子(AgNPs) 获得少数层GO和AgNPs复合薄膜(AgNPs/GO). 采用紫外-可见光吸收光谱、 原子力显微镜和扫描电子显微镜对复合薄膜的生长和表面形貌进行了表征. 结果表明, 通过调控AgNPs 溶胶浓度和自组装循环次数, 可以获得AgNPs/GO/AgNPs 的三明治结构, 并在基底表面形成均匀的AgNPs 聚集体. 表面增强拉曼散射(SERS)研究结果表明, AgNPs/GO-4基底具有最佳的SERS性能, 其对罗丹明6G(R6G) 和结晶紫的平均拉曼增强因子分别为3.4×10⁸和1.3×10⁹, 对R6G的最低检测浓度约为10^-12 mol/L. 多层三明治结构和较小颗粒间距使得AgNPs层之间产生强烈的耦合作用, 并在GO片层间产生大量的“热点”, 显著提高SERS性能, 而少数层GO具有强吸附性, 有利于分子在基底中富集, 从而起到化学增强作用, 提高SERS灵敏度.

Fabrication and SERS Performance of “Sandwich” Structured Silver Nanoparticles/Graphene Oxide Substrates†

Silver nanoparticles/graphene oxide(AgNPs/GO) films with few-layer GO were prepared through alternating deposition of GO sheets and positively charged AgNPs via electrostatic self-assembly approach. The formation and surface morphology of prepared substrates were characterized by UV-Vis spectra, AFM and SEM. The results show that the AgNPs/GO substrates with “Sandwich” structure and AgNPs aggregates can be obtained by the control of concentration of AgNPs colloid and self-assembly cycles. The SERS performances show that the AgNPs/GO-4 substrate has the optimal SERS activity. The average analytical enhancement factors(AEFs) of this substrate towards Rhodamine 6G and crystal violet are 3.4×10⁸ and 1.3×10⁹, respectively, and the minimum detectable concentration of R6G is 10^-12 mol/L. Due to the “Sandwich” structure and strong coupling effect of narrow interparticle distance, abundant “hot spots” can be generated in GO sheets, resulting in improved SERS activity. Furthermore, the strong adsorption ability of few-layer GO is beneficial for enrichment of molecules in substrate, providing the chemical enhancement effect and improving the SERS sensitivity.