Nonlinear optical response of silver trimer adsorbed para-aminobenzoic acid: A DFT study

Abstract

The reported study is motivated by our previously done experimental demonstration of the optical limiting behavior of para-aminobenzoic acid and enhanced nonlinear optical responses of compounds with Ag3 nanoparticle complex. The present study is a theoretical insight into the nonlinear optical responses of para-aminobenzoic acid adsorbed with Ag3 trimer. The enhancement in the optical nonlinearity of the para-aminobenzoic acid after the adsorption of the silver trimer (Ag3) was accounted in the present study. The density functional theory was used to establish the occurrence of the intra and intermolecular charge transfer between the donor and acceptor moieties of the para-aminobenzoic acid and Ag3 trimer. The molecular electrostatic potential surface and inter-fragment charge transfer analysis were used to establish the donor nature of the Ag3 trimer, amino group, and acceptor of the carboxyl group. The absorption spectra and Fourier-transform infrared spectra were used to account for the electronic and vibrational modes. The value of first-order hyperpolarizability of para-aminobenzoic acid and Ag3 complex was observed to increase by six times that of para-aminobenzoic acid. The high value of first-order hyperpolarizability shows the potential nonlinear optical activity of para-aminobenzoic acid adsorbed with Ag3 trimer. The presented study forms a strong base for experimental demonstration of the nonlinear optical activity of the PABA and the silver nanoparticles and the experimental work will be done in the near future for the NLO responses and optical limiting activity of PABA combined with silver nanoparticles.