Adsorption orientation of 8-azaadenine on silver nanoparticles determined by SERS and DFT

8-Azaadenine (8AA) is structurally similar to both adenine and benzotriazole, and therefore, it is reasonable that it could adsorb onto noble metal nanoparticles (NPs) in an orientation analogous to either one. In this study, Raman and surface-enhanced Raman spectroscopy (SERS) of 8AA are investigated to determine its adsorption orientation on Ag NPs. In support of the analysis, the Raman spectra of 8AA and various Ag⁺/8AA complexes were simulated using density functional theory (DFT) at the B3LYP level. For both normal Raman and surface-enhanced Raman spectroscopy, good agreement is observed between the experimental and simulated spectra. Our findings show that 8AA adsorbs onto Ag NPs via its N3 and N9 atoms side in an adenine-like manner. This result may be useful for nanoparticle-mediated drug delivery strategies of 8-azapurines or similar molecules with biological activities.