The mechanism of tuning the morphology of bio-conjugated ZnO nanoparticles with citrate coated gold nanoparticles for degradation of EBT: DFT and experimental study

Abstract

The electronic structure and the structural properties of the citrate capped gold (Au/Cit) adsorbed on the amino acids (AA) [Histidine (His), Arginine (Arg) and Aspartic acid (Asp)] conjugated Zinc Oxide (ZnO) nanoparticles (NPs), ZnO/AA are studied using the Density Functional Theory (DFT) simulations. On the basis of first principles calculation, we find that there is an exceptional high interaction between Au/Cit and Asp conjugated ZnO NPs (ZnO/Asp). This attaching mode can substantially change the morphology of the ZnO/Asp. On the other hand, the morphology of the Arg and His conjugated ZnO NPs (ZnO/Arg & ZnO/His) do not undergo considerable change because of the comparatively less binding between Au/Cit and ZnO/AA (Arg and His). Our conclusions of theoretical modelling are supported by the experimental results. The experimental work highlights the importance of the morphology of ZnO/AA, coated with Au/Cit (ZnO/AA-Au/Cit) nanocomposites in increasing the photocatalytic activity, opening applications for the degradation of Eriochrome Black T (EBT) in aqueous solution. Based on photodegradation studies and first principles calculations, it is observed that ZnO/Arg-Au/Cit is more effective photocatalyst for the degradation of EBT in aqueous solution as compared to ZnO/Asp-Au/Cit and ZnO/His-Au/Cit.