STUDY OF MICROSTRUCTURE AND OPTICAL PROPERTIES OF PVA-CAPPED ZnS: Cu NANOCRYSTALLINE THIN FILMS

Abstract

A study has been carried out on the Cu doping and PVA capping induced optical property changes in ZnS : Cu nanocrystalline powders and thin film. For this study, ZnS : Cu nanopowders with Cu concentrations of 0.1%, 0.15%, 0.2%, 0.3% and 0.4% are synthesized by the wet chemical method. The polyvinyl alcohol (PVA)-capped ZnS thin film with 0.2% Cu concentration and various PVA concentrations are prepared by the spin-coating method. The microstructures of the samples are investigated by the X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM). The results show that the prepared samples belong to the wurtzite structure with the average particle size of about 3–7 nm. The optical properties of samples are studied by measuring absorption and photoluminescence (PL) spectra in the wavelength range from 300 nm to 900 nm at 300 K. It is shown that the luminescent intensity of ZnS : Cu nanopowders reaches the highest intensity for optimal Cu concentration of 0.2% with the corresponding values of its direct band gap estimated to be about 3.90 eV. While the PVA coating does not affect the microstructure of ZnS nanometerials, the PL spectra of the samples are found to be affected by the PVA concentration as well as the exciting power density. The influence of the polymer coating on the optical properties can be explained by the quantum confinement effect of ZnS nanoparticles in the PVA matrix.

Energy transfer and luminescence enhancement of Cu2+ ions in polyvinyl pyrrolidone caped ZnS:Cu nanoparticles

“…(2) below. In research results of the previous work 5) ZnS:Cu nanoparticles were prepared by co-precipitation method, in which the doped Cu content does not affect PL peak position, but PL peak intensity increases with Cu content doping. So in this work, ZnS:Cu nanoparticles (C Cu = 0.5 mol%) also were synthesized by the co-precipitation method and coated by PVP using the following procedure:…”

“…[1][2][3][4] To synthesization ZnS:Cu nanoparticles it is can use chemical methods such as sol-gel, hydrothermal, co-precipitation. 5,6) However, during the process of forming and developing crystals, the orientation binding and Ostwald ripening often occur, so the nanoparticles are clustered together and the not uniform particle size. [7][8][9][10] Besides that, due to Cu element has many different oxidation states, so recently the nature of the green photoluminescence (PL) band still exists two different perspectives, in which they can be characteristic of Cu + ions (3d 10 ) 11,12) or Cu 2+ ions (3d 9 ) or the interstitial atoms.…”

“…Although some of works 5,9,[23][24][25][26][27]34) have studied the ZnS coating by PVA, PVP polymers, there are only very few studies on the effect of PVP 9,25,27,34) on Mn, Cu, Ni-doped ZnS nanoparticles. Especially, the role of PVP, luminescent enhancement of Cu 2+ ions and the energy transfer mechanism between PVP polymer and ZnS:Cu nanoparticles has not been systematically studied.…”

Luminescence performance of poly(aryl ether)s membranes with different morphologies

“…In fact, size and shape of the luminescent materials have an important influence on the photochemical stability, emission intensity, emission bandwidth and the efficiency of the device. Currently, there is growing interest in exploring novel micro‐ or nanometer scale luminescent materials . Different from bulk counterparts, the micro‐ or nanostructure materials possess fascinating physical and optical properties, for example a broad visible spectrum and increased luminescence efficiencies.…”

An Analysis of Structural and Optical Properties Undoped ZnS and Doped (with Mn, Ni) ZnS Nano Particles

“…Photo luminescent properties and efficiency of ZnS depend on intrinsic surface states of the particles, and nature of the chemicals treatment employed in their fabrication. Research is also noticed on the application of these types of films in light-emitting materials as well as on their optical properties [2]. The optical light emission in blue-red spectral region is characterized by blue shift at smaller crystallite dimension.…”