A study of light induced surface reactions of sildenafil citrate on hybrid AgCl/Ag nanoparticle dimers by surface enhanced Raman scattering and pulse radiolysis techniques

AgCl/Ag nanoparticle dimers (NPD) are important from photocatalysis point of view as it is reported to show photocatalytic activity in visible region. In this work, AgCl/Ag NPDs were synthesized by controlling the concentration of available chloride ions as well as the capping agent, sildenafil citrate (SC). Transmission electron microscopy (TEM), selected area electron diffraction (SAED) and UV-vis absorption property was used to probe morphology, lattice structure and optical property of as synthesized AgCl/Ag NPDs. SERS spectrum of SC adsorbed on the AgCl/Ag NPD excited at 632 nm, which is energetically closer to the coupled plasmon peak at 605 nm, showed some unexplained vibrational peaks. The above system was probed further by using pulse radiolysis technique and time-dependent density functional theory (TD-DFT) calculations. The results suggest that a direct electron transfer reaction from AgCl/Ag NPD to SC is involved in appearance of anomalous features in SERS spectrum.