Quantum chemical and molecular dynamics simulation approach to investigate adsorption behaviour of organic azo dyes on TiO2 and ZnO surfaces

Abstract

Quantum chemical approaches are very much significant in the field of corrosion chemistry to understand the structure-property relationship of various organic molecules as corrosion inhibitors. Here is the adsorption behavior of three organic azo-dyes, viz. 6-((4-(diethylamino)-2-methylphenyl)diazenyl)benzo[de]isochromene-1,3-dione (named as Dye-1); 4-[6-[2-[4-(N,N-Diethylamino)-2-methylphenyl]diazenyl]-1,3-dioxo-1H-benz[de]isoquinolin-2(3H)-yl]-N-(2-thiazolyl)benzenesulfonamide (named as Dye-2); 4-[6-[2-[4-(N,N-Diethylamino)-2-methylphenyl]diazenyl]1,3-dioxo-1H-benz[de]isoquinolin-2(3H)-yl]-N-(2-pyrimidinyl)benzenesulfonamide (named as Dye-3) on the rutile TiO2 and ZnO surfaces have been explored via quantum chemical approach, i.e. density functional theory (DFT), local reactive sites analysis and molecular dynamic (MD) simulation studies. Global relativities of the dye molecules have been explored by calculating the energy of the frontier molecular orbitals, energy difference (ΔΕ), electronegativity (χ), electron affinity (A), softness (σ), and hardness (η) like quantum chemical parameters. Furthermore, MD simulation study has been performed to comprehend the adsorption behaviour as well as the adsorption configuration of three selective dye molecules on TiO2 and ZnO surfaces mimicking the real adsorption and surface protection phenomenon. HIGHLIGHTS The mechanisms of adsorption behaviour of three organic azo dyes on the TiO2 and ZnO surfaces have been explored at the atomistic level. Fukui indices analysis revealed the presence of locally reactive sites responsible for adsorption. MD simulation results revealed the adsorption of dye molecules onto the metal oxide surfaces occurs in a horizontal fashion. The horizontal adsorption of dye molecules undergoes both physisorption and chemisorption on the metal oxide surface leading to greater surface coverage.