Bioinspired Conyza bonariensis-mediated ZnO/rGO NCs for effective degradation of toxic compounds under visible-light irradiation

Abstract

This study reports a green, cost-effective synthesis of ZnO/rGO nanocomposites (NCs) using Conyza bonariensis leaf extract as a novel bio-reducing agent. The nanocomposites were prepared via a simple hydrothermal method. Extensive characterization techniques including XRD, FT-IR, EDS, UV-DRS, XPS, BET, SEM, TEM, and AFM were employed to evaluate the crystallite size, phase structure, chemical composition, surface morphology, porosity, and particle size of the synthesized material. XRD analysis confirmed the formation of a hexagonal wurtzite ZnO phase with an average crystallite size of approximately 17.22 nm, calculated using the Debye-Scherrer equation. SEM revealed a distinctive "tuberose flower"-like morphology of ZnO particles distributed on the reduced graphene oxide (rGO) sheets, with flower diameters ranging from 1 to 2 μm and petal widths of 40-70 nm. Further, TEM supported the uniform distribution of ZnO tubular petals on graphene nanosheets. BET analysis demonstrated the mesoporous nature of NCs. Remarkably, the bioinspired ZnO/rGO NCs exhibited excellent photocatalytic activity under visible-light irradiation, effectively degrading industrial dyes such as Congo red (CR), Methylene blue (MB), and Thymol blue (TB). The enhanced photocatalytic performance is attributed to the nanocomposites' unique scaffold-like architecture, increased light absorption, and efficient charge separation.