Chen Y, Chen S J, Li S, Wei J J
Yangtze University College of Physical Science and Technology Jingzhou China.
Yangtze University College of Physical Science and Technology Jingzhou China csj@yangtzeu.edu.cn.
Cell Mol Biol (Noisy-le-grand). 2015 Oct 16;61(5):11-5.
In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.
在本研究中，测量了对羟基苯甲酸（PHBA）粉末的正常拉曼光谱及其在银胶体溶液中的表面增强拉曼散射（SERS）光谱，测量条件为近红外激发。在理论计算中，建立了PHBA吸附在银纳米颗粒表面的两种模型。使用密度泛函理论（DFT）方法计算了这两种模型的拉曼频率，并与实验结果进行了比较。结果发现，计算得到的拉曼频率与实验值吻合良好，这表明在银胶体溶液中，关于SERS效应存在两种增强机制，即物理（电磁，EM）增强和化学（电荷转移，CT）增强。此外，从在银胶体中获得的高质量PHBA的SERS光谱，我们推断银胶体中的PHBA分子通过羧基以垂直取向吸附在金属表面。因此，SERS光谱和DFT计算相结合对于研究分子在金属胶体上的吸附取向是有用的。
