Biomimetic Synthesis, Characterization, and Evaluation of Fluorescence Resonance Energy Transfer, Photoluminescence, and Photocatalytic Activity of Zinc Oxide Nanoparticles

Owing to the development of nanotechnology, biosynthesis of nanoparticles (NPs) is gaining considerable attention as a cost-effective and eco-friendly approach that minimizes the effects of toxic chemicals used in NP fabrication. The present work reports low-cost phytofabrication of zinc oxide (ZnO) NPs employing aqueous extracts of various parts (leaves, stems, and inflorescences) of Tephrosia purpurea (T. purpurea). The formation, structure, morphology, and other physicochemical properties of ZnO NPs were characterized by ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS). UV–Vis spectral analysis revealed sharp surface plasmon resonance (SPR) at around 250–280 nm, while the XRD patterns confirmed distinctive peaks indices to the crystalline planes of hexagonal wurtzite ZnO NPs. TEM analysis confirmed the presence of spherical-shaped ZnO NPs with average particle sizes (PS) between 25–35 nm, which was in agreement with the XRD results. FTIR analysis revealed that phenolics, flavonoids, amides, alkaloids, and amines present in the plant extract are responsible for the stabilization of the ZnO NPs. Further, the hydrodynamic diameter in the range of 85–150 nm was measured using the DLS technique. The fluorescence resonance energy transfer (FRET) ability of biogenic ZnO NPs was evaluated, and the highest efficiency was found in ZnO NPs synthesized via T. purpurea inflorescences extract. Photoluminescence (PL) spectra of biogenic ZnO NPs showed three emission peaks consisting of a UV–Vis region with high-intensity compared to that of chemically synthesized ZnO NPs. The biosynthesized ZnO NPs showed photocatalytic activity under solar irradiation by enhancing the degradation rate of methylene blue (MB). Among the prepared biogenic ZnO NPs, T. purpurea leaves mediated with NPs acted as the most effective photocatalyst, with a maximum degradation efficiency of 98.86% and a half-life of 84.7 min. This is the first report related to the synthesis of multifunctional ZnO NPs using T. purpurea, with interesting characteristics for various potential applications in the future.

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

10.21203/rs.3.rs-309748/v1 ◽

2021 ◽

Author(s):

Udari Wijesinghe ◽

Gobika Thiripuranathar ◽

Haroon Iqbal ◽

Farid Menaa ◽

Anam Razaaq

Keyword(s):

Zinc Oxide ◽

Energy Transfer ◽

Fluorescence Resonance Energy Transfer ◽

Average Particle Size ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Solar Irradiation ◽

Average Particle ◽

Zno Nps ◽

Fluorescence Resonance

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.

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