Properties Of ZnS Nanocrystals Research Articles

Influence of structural disorder on the photocatalytic properties of ZnS nanocrystals prepared by the one-pot solvothermal approach

This study focuses on the impact of the sulfur vacancies on the photocatalytic response of the ZnS nanocrystals synthesized by solvothermal method varying the concentration of zinc acetate/thiourea precursors. XRD patterns show that these samples have a hexagonal structure with different degrees of crystallinity, varying the crystallite size from 2.48 to 2.85 nm. The UV-Vis data reveals an absorption peak (at about 320 nm) characteristic of ZnS nanocrystals. As a result, a decrease in the bandgap value of these materials was observed from 3.78 to 3.62 eV. In principle, a comparison of these results and theoretical calculations reveals the formation of intermediate levels inside the bandgap due to structural polarization. These findings also corroborate the zeta potential measured for these samples, evidenced by an increase of positive charge of ZnS surfaces. Also, the low Miller-index surfaces, such as (100), (110) and (0001), were investigated by periodic density functional theory calculations, in nice agreement with the experimental data. A photocatalysis mechanism was investigated and confirmed the formation of reactive oxygen species.

OPTICAL PROPERTIES OF OF ZnS:Fe NANOCHRYSTALLS OBTAINED BY COLLOIDAL METHOD

Iron doped zinc sulfide nanocrystals were obtained by colloidal synthesis using gelatin, lactose or polyvinyl alcohol as a stabilizing matrix. The structure of the nanocrystals was determined using X-ray diffraction (XRD). The influence of the concentration effect on the size and properties of ZnS nanocrystals, the optical absorption spectra and photoluminescence spectra were studied, and the types of optical transitions in these nanocrystals were determined.

Spectral-luminescent characteristics of fluorophosphate glasses with zinc sulfide nanocrystals

Fluorophosphate glasses doped with ZnS are studied. The properties of ZnS nanocrystals formed are determined using X-ray-diffraction analysis and optical spectroscopy. The size and the band-gap width of these crystals are determined by the Tauc method. It is shown that ZnS nanocrystals luminesce in the visible spectral region with a low (2–3%) absolute quantum yield.

Influence of Mn Doping on the Microstructure and Optical Properties of ZnS Nanocrystals

ZnS nanoparticles with Mn2+doping (0–2.5%) were prepared through a simple chemical method. The nanostructures of the prepared undoped ZnS and Mn2+-doped ZnS:Mn nanoparticles had been characterized by X-ray power diffraction (XRD), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), photoluminescence spectra (PL) and UV–vis absorption spectra. The mean size of the particles was found to be approximately 3-5 nm through XRD measurements, TEM and the UV–vis absorption spectra. It was found that the Mn2+4T1→6A1emission intensity of ZnS:Mn nanoparticles was significantly enhanced with the increase of Mn2+concentration, which arrived a maximum value when Mn2+initial doping concentration was 1.5%. Continue increasing the Mn2+concentration, namely more than 1.5%, the Mn2+4T1→6A1emission intensity became weakened. And the resultant ZnS:Mn nanoparticles exhibited high efficiency for degrading methylene blue under UV light irradiation.

Full‐color nanostructured thin‐film electroluminescent device utilizing ZnS nanocrystals doped with activator‐ions

AbstractWe have studied nanostructured (NS‐) thin‐film electroluminescent (TFEL) devices utilizing the ZnS nanocrystals (NCs) with the mean crystal sizes of ca. 2–4 nm doped with activator‐ions. As compared to the conventional TFEL device, we have achieved a remarkable reduction in the operation voltages by >100 V0–p. Moreover, toward full‐color emissions, EL emissions of three primary colors, i.e., red, green, and blue have been derived from Mn2+, Tb3+, and Tm3+ ions, respectively. In this article, we review the studies on the fundamental properties of ZnS NCs as well as the device performance of the NS‐TFEL devices. We also discuss the excitation mechanisms of the activator‐ions in the ZnS NCs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nonlinear optical properties of ZnS nanocrystals incorporated within the polyvinyl alcohole photopolymer matrices

AbstractPhotoinduced nonlinear optical effects in ZnS nanocrystallites incorporated within the photopolymer polyvinyl alcohol matrices were studied. As a basic method we have used photoinduced optical second harmonic generation (SHG). The Q‐switched HF‐laser (λ = 2.64.μm; pulse duration 30‐40 ps) was used as a source of probing (fundamental) light beam and the pulsed nitrogen (λ = 337.7 nm) was applied as a source of the photoinducing pump light. With increasing photoinducing beam power, the output SHG signal (at λ = 1.32 μm) increases. The maximal second‐order non‐linear optical susceptibility corresponds to tensor component d123 = d14 = 3.8 ± 0.2 pm/V at a photoinducing power density equal to about 1.25 GW/cm2. With decreasing temperature, the SHG signal increases within the temperature range 25‐30 K. Time‐dependent pump‐probe measurements of the SHG indicate an existence of the SHG maximum for a pump‐probe delaying time 20 ps. The ZnS hexagonal structural components play a crucial role in the observed photoinduced second‐order non‐linear optical effects. Large values of the non‐linear optical constants as well the good technological parameters open a possibility to enhance the non‐linear optical susceptibilities of the investigated ZnS nanocrystallites.