水溶液中碳纳米管的表面增强拉曼光谱研究

Surface-Enhanced Raman Spectroscopy of Carbon Nanotubes in Aqueous Solution

合成了碳纳米管和金纳米颗粒的复合物,测量了水溶液相中复合物的表面增强拉曼光谱,结果表明,碳纳米管的巯基化修饰可以提高碳纳米管与金纳米颗粒复合的效率,随着金纳米颗粒负载量的增加,碳纳米管的拉曼信号逐渐增强.加入己二胺分子可以减小金纳米颗粒之间的距离使表面增强效应更显著,碳纳米管的拉曼光谱得到进一步的增强.还可进一步在复合体系中加入对巯基苯胺和罗丹明B等小分子拉曼探针,利用金纳米颗粒的表面增强效应,这种多元复合体系有望作为多通道拉曼成像探针材料.

Carbon nanotubes （CNTs） exhibit intrinsic spectroscopic properties and are potential Raman and N1R florescence probes for bioimaging. However, the weak Raman intensity greatly obstructs such applications. Surface-enhanced Raman scattering （SERS） has shown to be an effective way to increase the Raman signal. SERS has been widely studied for solid samples. However, solid state is distinctly different from the environment in biosystems. Herein, we studied the SERS of Au- nanoparticle-decorated CNTs in aqueous solution, which offers a similar environment to biosystems. We found that the func- tionalization of CNTs with -SH groups can improve the attachment of Au nanoparticles on tube surfaces thus benefit the SERS effect. The particle size is another important issue for SERS. Particles of 50 nm show much stronger enhancement than those of 12 nm. The Raman intensity of CNTs increases with the increase of the concentration of Au nanoparticles. Hexame- thylene diamine molecules can act as the bi-linkers between Au nanoparticles, compressing the interparticle distance. This was proved by the red-shift of the band at ca. 540 nm and the appearance of a broad band around 700 nm in the absorption spectra of Au nanoparticles. Therefore the addition of hexamethylene diamine can further increase the Raman signal of CNTs by the strong coupling of the surface plasma from the Au nanoparticles with very small interparticle distances. Two kinds of commonly used small molecule Raman probesp-aminothiophenol and Rhodamine B both show remarkably enhanced Raman intensity when added to the aqueous dispersion of Au/CNT hybrids. This shows that these Raman probe molecules can ab- sorb onto the Au/CNT hybrids and their Raman spectra are able to be greatly enhanced by Au nanoparticles decorated on CNTs. Because various Raman bands from either CNTs or Raman probe molecules can be used for Raman imaging, this kind of Raman probe molecule/Au/CNT tri-component hybrid systems may be used as a potential nanostructured platform for multiplexed Raman imaging based on SERS effect.