Green synthesis of ZnO and Cu-doped ZnO nanoparticles from leaf extracts of Abutilon indicum, Clerodendrum infortunatum, Clerodendrum inerme and investigation of their biological and photocatalytic activities

In the present study, green synthesis and determination of the antioxidant, antibacterial, antifungal, anticancer and photocatalytic properties of the resultant Cu-doped zinc oxide nanoparticles (NAPs) were carried out. A superficial method (solution combustion method) was employed for the synthesis of un-doped ZnO NAPs from aqueous extract of Abutilon indicum, and synthesis of Cu-doped ZnO NAPs from aqueous extracts of Clerodendrum infortunatum (M1 NAPs) and Clerodendrum inerme (M2 NAPs). The synthesized un-doped ZnO, M1 and M2 NAPs were characterized by different spectroscopic techniques like Ultraviolet-visible (UV-Vis), Fourier Transform-Infrared (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The antibacterial and antifungal activities of M1 and M2 NAPs were determined by agar diffusion method, while their antioxidant properties were assessed through DPPH radical scavenging and ferric thiocyanate (FTC) and assays. Under sunlight irradiation, photocatalytic disintegration potential of M1 and M2 NAPs were determined by the degradation of Acid Black 234 dye. Results from FT-IR, XRD, EDX and SEM confirmed successful synthesis, crystalline nature, and spheroid-to-rod-like shapes of un-doped ZnO, M1 and M2 NAPs, with grain sizes of 16.72nm, 17.49nm and 20.73nm; and band gap energies of 3.37eV, 3.36eV and 3.31eV, respectively. The NAPs were good catalysts for effective degradation of Acid Black 234. They also exhibited remarkable antioxidant and anticancer activities. Significant antibacterial activity was shown by M2 NAPs against E. coli, S. aureus, Klebsiella and B. subtilis, with zones of inhibition (ZOIs) of 13±0.09, 14±0.01, 18±0.07 and 20±0.10, respectively. Significant antifungal potential was also produced by M2 NAPs at 5mg with ZOIs of 17±0.07 and 24±0.08 against A. niger and T. harzianum, respectively. These results indicate that aqueous extracts of A. indicum, C. infortunatum and C. inerme are effective reducing agents for green synthesis of un-doped ZnO, and Cu-doped ZnO NAPs with significant antimicrobial, antioxidant, and antifungal potential. Thus they are good candidates for future therapeutic applications.