Adsorption mechanism of p- aminophenol over silver-graphene composite: A first principles study

Herein, we report the theoretical insight into the adsorption mechanism of p-Aminophenol on graphene, silver cluster and silver graphene composites. DFT calculations are performed at M06-2X/LANL2DZ level of theory to explore the adsorption mechanism of p-Aminophenol (p-AP) over a bare coronene, a coplanar silver cluster (Ag-6), and two isomers of silver-graphene composites (isomer 1 and isomer 2). The highest E-int is found in p-AP@Ag-6 (-15.15 kcal mol(-1)) while the lowest is calculated for isomer 2 (-12.31 kcal mol(-1)). NCI results show that electrostatic forces have a strong influence on the stability of p-AP@Ag-6 and also of isomer 1, which results in their higher stability. Additionally, MD simulations confirmed that the adsorption of p-Aminophenol over silver-graphene composite is stable and efficient at room temperature. The adsorption mechanism in these complexes is further explored through variations in; absorption maximum (lambda(max)), excitation energies, and oscillator strength (f(o)). The values of E-int and shift of lambda(max) decreases in the order p-AP@Ag-6 > isomer 1 > p-AP@coronene. isomer 2. NBO and CDA analysis are performed to gain a deeper insight into the direction and amount of charge transfer between donor and acceptor units. The degree of charge transfer as measured by the NBO charges decreases in the order isomer 1 > p-AP@Ag-6 > isomer 2 > p-AP@coronene. The transfer of electron density from the analyte in the complexes is solely due to the contribution of the p-orbital in the HOMO. Orbital hybridization in the complexes results in the generation of new occupied and virtual energy states, and the appearance of new energy states close to the Fermi level causes a reduction in HOMO-LUMO gaps, and hence enhanced conductivity of p-Aminophenol complexes. The outcome of the current study will provide useful guidelines in the development of promising sensing material for p-Aminophenol. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study provides theoretical insight into the adsorption mechanism of p-Aminophenol on graphene, silver cluster, and silver graphene composites. The research shows that electrostatic forces play a significant role in the stability of the complexes, and MD simulations confirm the stability and efficiency of adsorption at room temperature. NBO and CDA analysis reveal the direction and amount of charge transfer between donor and acceptor units in the complexes.