密度泛函理论研究黄曲霉素B1的表面增强拉曼散射效应

用密度泛函理论B3LYP方法和6—311G（d，p）／Lan12DZ优化得到黄曲霉素B1（AFBI）分子及其复合物AFB1-Ag的稳定结构，并计算了复合物的表面增强拉曼光谱和预共振拉曼光谱．结果表明，AFB1分子的拉曼光谱很大程度依赖于吸附位点以及入射光的激发波长．与分子的常规拉曼光谱相比，复合物表面增强拉曼光谱中C=O伸缩振动模的增强因子约为10^2—10^3，是由于复合物的极化率增强而导致的静态化学增强，并分析了振动模式的振动方向与其拉曼强度的关系．选择复合物最大吸收峰附近激发光266和482nm以及远离共振吸收波长785和1064nm作为入射光，计算得到不同入射光激发下复合物的预共振拉曼光谱．结果表明其增强因子最大达N100量级，主要是由电荷转移产生的共振增强引起的．

Surface-enhanced Raman Scattering of Aflatoxin B1 on Silver by DFT Method

The structure, electrostatic properties, and Raman spectra of aflatoxin B1 （AFB1） and AFB1-Ag complex are studied by density functional theory with B3LYP/6- 311G（d,p）/Lan12dz basis set. The results show that the surface-enhanced Raman scattering （SERS） and pre-resonance Raman spectra of AFB1-Ag complex strongly depend on the adsorption site and the excitation wavelength found to enhance 102-103 order compared to of the incident light. The SERS factors are normal Raman spectrum of AFB1 molecule due to the larger static polarizabilities of the AFB1-Ag complex, which directly results in the stronger chemical enhancement in SERS spectra. The pre-resonance Raman spectra of AFB1-Ag complex are explored at 266, 482, 785, and 1064 nm incident light wavelength, in which the enhancement factors are about 10^2-10^4, mainly caused by the charge-transfer excitation resonance. The vibrational modes are analyzed to explain the relationship between the vibrational direction and the enhanced Raman intensities.