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

The structure, electrostatic properties, and Raman spectra of aflatoxin B-1 (AFB(1)) and AFB(1)-Ag complex are studied by density functional theory with B3LYP/6-311G(d,p)/Lanl2dz 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 of the incident light. The SERS factors are found to enhance 10(2)-10(3) order compared to normal Raman spectrum of AFB(1) 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 AFB(1)-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.