C层包覆Ag纳米颗粒基底的表面增强拉曼散射研究

C shell coated Ag nanoparticles-based substrates for surface-enhanced Raman scattering

Ag纳米结构是最常用的表面增强拉曼散射(SERS)活性基底,缺点是Ag的化学稳定性和生物相容性比较差。为此,利用化学方法合成了一种新型的SERS活性基底—纳米碳层包覆的Ag(Ag@C)纳米颗粒。利用透射电子显微镜(TEM)和紫外-可见吸收光谱对制备的核壳结构纳米颗粒进行了表征,并研究了颗粒的SERS活性。结果表明,罗丹明6G(R6G)、结晶紫(CV)和孔雀石绿(MG)分子在Ag@C悬浮液中的SERS光谱强度与在Ag胶中的SERS光谱强度相比显著增强。根据光谱的变化规律推断,额外的增强来自于化学增强。由于C层的存在,相比于Ag纳米颗粒,Ag@C颗粒的化学稳定性和生物相容性都有所改进。

Ag is the most common surface-enhanced Raman scattering （SERS） active element because of its great enhancement.ability in the visible spectrum region. However,Ag has its serious drawbacks as SERS substrate . bad chemical stability and biological compatibility. In order to overcome these disadvantages,we propose a new kind of SERS-active Ag substrate in this work,C shell coated Ag （Ag@C） nanoparticles. Ag nanoparticles were prepared by Leers method and then C shells were coated on them in hydrothermal condition. To characterize the prepared core-shell nanoparticles, UV-vis absorption spectra,transmission electron micrograph （TEM） and SERS spectra are used. UV-VIs absorption spectra show that when the Ag nanoparticles are not coated with C shell, the highest absorption peak is located at 417 nm,corresponding to the typical absorption band of Ag nanoparticles. As the Ag nanoparticles in the same size are coated with C shell, the peak is red-shifted to 426 nm due to the variation of dielectric constant induced by the presence of C shell. The results of the SERS experiment show that the SERS intensities of Rhodamine 6G （R6G） ,crystal violet （CV） and malachite green （MG） in Ag@C suspension can be significantly increased, as compared with that in Ag colloids. In addition, the variations of the intensities of different vibration hands in SERS spectra are distinguished. All the results indicate that extra enhancement should be attributed to chemical enhancement. The newly developed substrate has better chemical stability and biological compliance due to the presence of C. So the Ag@C nonoparticles are the potential SERS-active substrates.