Green synthesis of ZnO-QDs using aqueous Ficus nitida leaf extract: phytochemical assessment and biological activity study

Abstract

Quantum dots (QDs) are highly intriguing due to their distinct electronic, optical, and structural characteristics. Most of them still adhere to the old preparation methods that must be extremely precise to achieve this very tiny size of particles. Developing cost-effective, simple, and efficient methods for the preparation of quantum dots would be a breakthrough in nanotechnology. Zinc oxide quantum dots (ZnO-QDs) were successfully prepared employing a green synthesis approach when mediated by aqueous Ficus nitida leaf extract. Phytochemical analysis of the Ficus nitida leaf extract, including total phenolic content (TPC), total flavonoid content (TFC), DPPH, ABTS, and FRAP assays, showed that the extract contained the necessary phytochemicals and antioxidants for reducing, stabilizing, and capping ZnO-QDs. ZnO-QDs were characterized using XRD, FTIR, SEM, EDX, TEM, XPS, fluorescence spectroscopy, BET and TGA. TEM results showed that the zinc oxide particles formed ranged in size from 2–10 nm. Fluorescence spectra had an emission peak at 423.8 nm confirming the presence of ZnO-QDs at less than 2 nm. The ability to produce quantum dots with biological properties is a significant advantage. The biological activity of the ZnO-QDs against S. aureus and C. albicans was investigated and validated through molecular docking, yielding auspicious outcomes. Evaluation of the antiviral potential of the ZnO-QDs was conducted through molecular docking analyses against SARS-COV-2 virus with SARS-CoV-2 RNA polymerase and SARS-CoV-2 spike protein.