Role of gold nanocolloids on the photostability of 2-hydroxy-5-methyl benzaldehyde molecule and evidence of excited state intramolecular proton transfer process aided by DFT, non-adiabatic Ab Initio molecular dynamics simulations

Abstract

The role of gold nanocolloids (AuNCs) on the photostability of 2-hydroxy-5-methyl benzaldehyde (HMBZ) molecule under UV exposures has been investigated using UV–vis absorption and fluorescence spectroscopic techniques. The experimental observations indicate the prominent role of AuNC towards controlling the photoproduct formations and rupture of intramolecular hydrogen bond (IHB) in the ‘CE’ conformeric form of the molecule. The rationale behind the experimental observations has been suggested to be due to the absorption of incident UV radiations by the nanoparticles, leaving behind only insignificant fraction of it for inducing photodegradation of HMBZ molecule. The photophysical behaviors of HMBZ molecule in different solvents and in varied pH media are also explicitly studied for the first time. Evidences of excited state intramolecular proton transfer (ESIPT) species of the molecule are estimated from the experimental observations aided by non-adiabatic Ab Initio molecular dynamics and density functional theory (DFT) calculations.