聚甲基丙烯酸甲酯间隔的金纳米立方体与金膜复合结构的表面增强拉曼散射研究

Surface-enhanced Raman scattering effect of composite structure with gold nano-cubes and gold film separated by polymethylmethacrylate film

金属纳米颗粒与金属薄膜的复合结构由于其局域表面等离子体和传播表面等离子体间的强共振耦合作用,可作为表面增强拉曼散射(SERS)基底,显著增强吸附分子的拉曼信号.本文提出了一种聚甲基丙烯酸甲酯(PMMA)间隔的90 nm金纳米立方体与50 nm金膜复合结构的SERS基底,通过有限元方法数值模拟,得到PMMA的最优化厚度为15 nm.实验制备了PMMA间隔层厚度为14 nm的复合结构,利用罗丹明6G (R6G)为拉曼探针分子, 633 nm的氦氖激光器作为激发光源,研究了复合结构和单一金纳米立方体的SERS效应,发现复合结构可以使探针分子产生比单一结构更强的拉曼信号.在此基础上,研究了不同浓度金纳米立方体水溶液条件下复合结构中R6G的拉曼光谱.结果表明,当金纳米立方体水溶液浓度为5.625μg/mL的条件下复合结构中R6G的拉曼信号最强,且可测量R6G的最低浓度达10^(–11) mol/L.

The composite structure of metal nanoparticle and metal film can be used as a surface-enhanced Raman scattering(SERS)substrate to significantly enhance the Raman signal of adsorbed molecules due to the strong coupling between local surface plasmons and propagating surface plasmons.An SERS substrate of the composite structure with gold nano-cubes and gold film separated by polymethylmethacrylate(PMMA)film is proposed.The optimum thickness of PMMA is 15 nm obtained by numerical simulation through using finite element method.The composite structure of PMMA spacer with a thickness of 14 nm is prepared experimentally.Using R6 G as the Raman probe molecules and He-Ne laser with a wavelength of 633 nm as an excitation source,the SERS effect of the composite structure and single gold nano-cubes are studied.It is found that the composite structure can make the probe molecules produce a stronger Raman signal than the single structure.Furthermore,the SERS spectra of R6 G molecules on the composite structure under the condition of aqueous solution of gold nano-cubes with different concentrations are studied.The results show that when the concentration of gold nano-cubes’aqueous solution is 5.625μg/mL,the SERS signal of the R6 G molecules on the composite structure is strongest.The lowest concentration of R6 G molecules which can be detected is about 10-11 mol/L.