Synthesis of graphenized Au/ZnO plasmonic nanocomposites for simultaneous sunlight mediated photo-catalysis and anti-microbial activity

Highlights: • One pot green synthesis of ternary/binary NC of defined morphology in water (solvent/reaction medium) at lower temperature. • Template free anisotropic synthesis of highly crystalline structures excludes post sintering processes. • Ternary NCs (AZG) has broader light sensitivity, increased utility, applicability and cost effectiveness. • Multi-functional sunlight induced activities: Dye degradation (MB) and anti-bacterial activity (S. aureus). • 60 μg/ml AZG can achieve 100% efficiency for bacterial killing (2 h) and dye degradation (5 μM/30 min). - Abstract: Sunlight mediated photo-degradation and anti-bacterial activity of hetero junctioned plasmonic binary (Au/ZnO, RGO/ZnO) and ternary (RGO/Au/ZnO) nanocomposites (NC) have been reported. Higher photo-charge carrier generation, increased charge separation, improved active sites for catalysis, enhanced LSPR and larger photo-response regions have been achieved. Decoration with Au nanoparticles (ca. 11 ± 3 and 48 ± 5 nm) and RGO of ZnO (3D/1D) microstructures (aspect ratio 15.18) provides ternary NCs an edge over mono/bi component catalysts. The ternary NC have shown improved dye degradation capacity with 100% efficiency (5 μM MB solution) and average adsorption degradation capacity (Q°) of 83.34 mg/g within 30 min of sunlight exposure (900 ± 30 Wm⁻²). Elaborated studies by varying reaction parameters like initial dye concentration, contact time, type of NCs and initial loading of NCs reveals pseudo first order degradation kinetics. 100% microbial killing of Gram positive S.aureus strain with 60 μg/ml of NC using sunlight as activator has proven the simultaneous multiple functionality of the NC. Further, facile green one pot hydrothermal synthesis with water as reaction medium, absence of photo-corrosion of NCs, regeneration ability (ca. 90% for 10 μM solution) of NCs, projects a broader potential application of the synthesized NCs and could reduce the continuous requirement of such material, limiting the environmental toxicity.