Structural, spectral and electrical properties of green synthesized ZnS nanoparticles using Elaeocarpus floribundus leaf extract

Abstract

The present study reports an environment friendly method for the synthesis of zinc sulphide (ZnS) nanoparticles using an aqueous extract of Elaeocarpus floribundus (Indian olive) leaf that acts as a capping as well as a stabilizing agent. X-ray diffraction and selected area electron diffraction studies confirm cubic structure of the nanoparticles. Transmission electron microscopy shows spherical in shape of the particles with diameter ranging from 8 to 3 nm. Static and high frequency optical dielectric constants are determined for all the samples. The optical band gap calculated from Tauc's plot is found to increase from 3.8 to 4.1 eV. The refractive index of the samples is calculated using Moss and Herve-Vandamme models. The room temperature photoluminescence spectra of the samples show a broad peak centred at 440 nm. The biomolecules involve in the formation of ZnS nanoparticles are studied by Fourier transform infrared spectroscopy analysis. The possible growth mechanism of the synthesized ZnS nanoparticles is also discussed. Current-voltage characteristics under illumination exhibit anomalous behaviour, it shows peak through sudden rise and fall of current with increase of voltage.

Synthesis and characterization of biopolymer protected zinc sulphide nanoparticles

“…The average crystallite size for the four samples is found to be 3.2, 2.9, 2.3 and 1.8 nm respectively. The inter planer spacing (d) and the lattice constant (a) are calculated from the standard relations [22,10]. The FWHM of the XRD peaks may also contain contribution from lattice microstrain.…”

“…Two peaks at 342 nm (3.6 eV) and 422 nm (2.9 eV) are observed for all the samples. The broad peak centred at 422 nm is attributed to the presence of sulphur vacancies in the lattice [10,29]. This emission has been known due to the recombination between the sulphur vacancies related donor and the valence band.…”

“…This is in good agreement with the XRD result. The average size estimated from TEM micrographs are larger than those obtained from XRD patterns, because the electron microscopy in the regime of extremely small sizes may lead to an over estimation of the contribution of larger particles for the given size distribution [10]. The selected area diffraction (SAED) patterns (shown inset of Fig.…”

“…The estimated band gap of ZnS nanoparticles is much larger than that of bulk ZnS due to quantum confinement effect. The band gap variation is due to presence of trapp levels within the band gap [10]. The quantum confinement effect allows us to tune the emission and excitation wavelengths of nanoparticles by tuning particle size d(E).…”

“…Green chemical route for the synthesis of ZnS nano have been in practice [6,7]. In some of our resent works also, we have reported on such preparations using edible mushrooms [8,9] and Elaeocarpus floribundus leaf extract [10].…”