Exploring the nonlinear optical limiting activity of para-aminobenzoic acid by experimental and DFT approach

Abstract

The present study accounts for the nonlinear optical behavior of para-aminobenzoic acid. The intramolecular charge transfer was established using electrostatic potential and Hirshfeld’s surfaces. The fingerprint plots identified that the bonds associated with the functional groups of para-aminobenzoic acid (amino and carboxyl) have major contributions to the total intramolecular charge transfer. It was observed that the para-aminobenzoic acid gave a broad absorption spectrum between 240 and 310 nm wavelength experimentally as well as computationally. From Tauc’s plot, the obtained direct band gap of para-aminobenzoic acid is 3.66 eV. The vibrational peaks of experimental FT-IR spectra were also found similar to the peaks observed in computational FT-IR. Moreover, high-frequency peaks were observed for the associated functional groups. The first-order hyperpolarizability of para-aminobenzoic acid was computed around 29.99 × 10–30 esu. We derived from the open-aperture Z-scan data that the para-aminobenzoic acid exhibits strong reverse saturable absorption. The positive value of the nonlinear absorption coefficient established the potential application of para-aminobenzoic acid in strong multi-photon absorption. Theoretical fit and intensity dependent Z-scan experiment confirm the occurrence of excited absorption (or) sequential two-photon absorption. The present study promises para-aminobenzoic acid for optical limiting applications.