Eco Friendly Zinc Oxide Wurtzite Nanostructures and their Efficacy for Photocatalysis, Photoluminescence and Fluorescence Resonance Energy Transfer

Abstract

In recent years, biosynthesized zinc oxide nanoparticles (ZnO NPs) are gaining importance due to their unique properties and tremendous applications. This study aimed to fabricate ZnO NPs by using extracts from various parts (i.e. stems, leaves, and inflorescences) of the traditional medicinal plant Heliotropium indicum (H. indicum) and to identify their photocatalysis, photoluminescence, and fluorescence resonance energy transfer (FRET) efficacy. The Ultraviolet-Visible (UV-Vis) spectrum was used to monitor the nanoparticles (NPs) formation, which exhibited a hypsochromic shifted absorption band between 360-370 nm. Fourier transform infrared (FTIR) analysis was carried out for the plant extracts and NPs to identify possible functional groups involved in the capping process. Transmission electron microscopy (TEM) analysis revealed NPs were spherical in shape and X-ray diffraction (XRD) results shown their wurtzite, hexagonal crystalline nature. Further, TEM and XRD consistently determined the average particle size ranging from 19 to 53 nm with more accuracy than scanning electron microscope (SEM). Dynamic light scattering (DLS) showed that the particles were well distributed and monodispersed. The maximum photocatalytic degradation of 95% was evaluated for biogenic ZnO NPs spectrophotometrically by monitoring the degradation of methylene blue (MB) dye (λmax = 662.8 nm) under solar irradiation. Photoluminescence (PL) analysis, revealed differentiated spectra with high-intensity emission peaks for biogenic ZnO NPs compared to chemically synthesized ZnO NPs. Eventually, the highest efficiency of FRET (80%) was found in ZnO NPs synthetized from the leaves. This remains the first attempt to synthesize multifunctional ZnO NPs using H. indicum for potential environmental and biomedical applications.