Dependence of surface-enhanced Raman scattering from Calf thymus DNA on anions

Dependence of surface-enhanced Raman scattering (SERS) from Calf thymus DNA on anions is investigated. With the silver colloid, the bands at 732, 960 and 1333 cm(-1) for adenine (A), 1466 cm(-1) for deoxyribose, and 1652 cm(-1) for the C=O group of thymine (T) are observably enhanced. With the presence of the Cl- or SO42- anions, the bands at 732 and 1326/1329 cm(-1) for the symmetric stretching and skeletal vibrational modes of adenine (A) are dramatically enhanced, and the enhancement effect with the SO42- ion is more than that with the Cl- ion. The experimental results show that the DNA molecule can be adsorbed on the silver colloid particles through the C6N and N-7 of adenine (A), the C=O of thymine (T) and deoxyribose. Moreover, the formed hydrogen bonding of the Cl- or SO42- ions to the C6NH2 group of adenine (A) can induce larger C6N electronegativity, which is favor for the C6N/N-7 cooperative adsorption on the (Ag)(n)(+) colloid particles.