Theoretical and experimental investigations of nitropyrene on silver for nonlinear optical and metal ion sensing applications

Abstract

Adsorption of nitropyrene (NPy) on silver has been analysed through theoretical and experimental techniques. Using density functional theory (DFT), variations in geometrical parameters were identified in regions of NPy near the silver cluster. Theoretical investigations on the plot of molecular electrostatic potential (MEP) and its charges, Fukui calculations and the overlap of natural bond orbitals(NBO) confirm charge transfer from silver to NPy. Using XRD technique, the average crystallite size of the NPy-Ag NPs has been calculated as 18.4 nm. The UV–Vis spectra of the investigated systems have been simulated theoretically and observed experimentally. Nonlinear optical (NLO) behaviour of NPy-Ag is predicted by theoretical studies and confirmed experimentally using the open aperture Z-Scan technique. Downshifting of theoretical and experimental C–N and NO2 stretching vibrational modes together with the additional in-plane CH bending vibrations of NPy-Ag strongly confirms the process of adsorption. Using calorimetric detection based on the plasmonic response of NPy-Ag NPs, a sensing mechanism for mercury ions is proposed based on both theoretical and experimental results. The study indicates that NPy-Ag NPs is a promising candidate for NLO and sensor devices.