DFT, TD-DFT and SERS analysis of a bioactive benzohydrazide’s adsorption in silver hydrosols at various concentrations

SERS was used to analyze the surface adsorption of a benzohydrazide derivative on silver nanoparticles. Density functional theory (DFT) calculations were used to determine the vibrational assignments in the surface-enhanced Raman scattering (SERS) spectra of (E)-4-methyl-Nˈ-[4-(trifluoromethyl)benzylidene]benzohydrazide (TFB) at various concentrations. TFB mostly adsorbs through C=O group and rings with silver. On the silver surface, however, the adsorption takes place through the ring’s π-electrons. As concentration of silver hydrosol changes, changes in orientation of TFB occur. TFB is adsorbed with a binding affinity of −131.74 kcal mol−1, suggesting a chemisorption process according to theoretical analysis. The time dependent-DFT analysis gives an adsorption of 310 nm for TFB while with silver complex there is a peak to higher values as a doublet at 520 and 688 nm with lowering of intensity as expected. The changes of thermodynamical parameters during adsorption are all are negative suggesting the adsorption process is spontaneous and exothermic.