Papers by Keyword: Zinc Sulphide

Abstract: In this work, pure ZnS and Mn doped ZnS nanoparticles are synthesized by simple chemical precipitation method. The structure of pure zinc sulphide and Mn doped zinc sulphide sample are analyzed by X-ray diffraction technique. The morphological structure of zinc sulphide and Mn²⁺ doped zinc sulphide nanoparticles are studied using scanning electron microscope (SEM). The average particle sizes of pure ZnS nanoparticles are determined to be from 29 nm to 44 nm and Mn doped ZnS nanoparticles are determined to be from 99 nm to 135 nm. The optical properties of pure and Mn doped ZnS nanoparticles have been investigated by photoluminescence (PL) spectroscopy. The emission spectrum of Mn²⁺ doped with ZnS particles of the present study shows blue shift of the yellow-orange emission peak at 590 nm. Nanofluids are prepared for six different concentrations by dispersing pure and Mn²⁺ doped ZnS nanoparticles in de-ionized water. Thermal conductivity studies are carried out for both nanofluid systems and the results are discussed.

Abstract: Pure and doped Zinc Sulfide (ZnS) quantum dots have attracted increasing interest from researchers working on various scientific and engineering applications in electronics, nonlinear optical devices for communication, and optical computers. In this study, ZnS nanoparticles doped with lanthanum (ZnS:La) with approximately 11 nm size was produced at 150°C by chemical precipitation route. Zinc Sulphide is an extensively studied group II-VI semiconductor with wide application in field of Photo Luminescence (PL),Electro Luminescence(EL) and Cathodo Luminescence (CL). It is an excellent light transmission material with high refractive index 2.27. XRD, SEM, FTIR UV-Vis and EDS characterize the samples.In this study, the UV–Visible absorption spectra of ZnS:La showed a red shift in the absorption shoulder compared with the spectra of undoped samples. ZnS nanoparticles could be doped with lanthanum ions during synthesis without altering the X-ray diffraction (XRD) patterns of ZnS. Also, the XRD pattern of the powders showed cubic crystal structures for ZnS:La. The Optical band gap has been found to be 2.7 eV. It was found that energy Band gap Eg decreases with doping of La.

Abstract: In the present investigation the photocatalytic activity of zinc sulphide has been enhanced using KCl in different molar ratios. The progress of the reaction was monitored spectrophotometrically. The effect of various parameters like pH, concentration of dye, amount of semiconductor, light intensity etc. upon the rate of photocatalytic bleaching of eosin Y has been observed. The molar ratio of KCl: ZnS = 0.25 was found to be a most efficient mixture for bleaching of eosin Y. A tentative mechanism for the photocatalytic bleaching of the dye has also been proposed.

Abstract: Zinc sulfide is inorganic material for electroluminescent applications. This work examines the possibility of obtaining good luminescent properties of the zinc sulfide mixture by double implosion experiment at elevated temperature.

Abstract: Electroluminescent, EL, materials are of interest in providing high brightness for display screens found in portable electronic devices, where the battery life is limited. Currently organic luminescent materials are being used, but the lifetime is low due to the degradation of the organic material under electric field over time. Some recent work with inorganic material of zinc sulfide has indicated high brightness at very long life times. This work focuses on the thermal processing of the zinc sulfide based EL material with trinitrotoluene, TNT. The zinc sulfide based phosphor and TNT are placed in a stainless steel container that can withstand high pressure. After closing, the chamber was evacuated and subsequently heated to over 300°C. The ZnS based phosphor was heated to a high temperature as the TNT decomposed. The sample was recovered after cooling and separated by optical observation of photoluminescence with a ultraviolet lamp. X-ray diffraction analysis showed that some transformation to hexagonal wurtzite phase occurred and was retained after cooling. EL and photoluminescence, PL, measurements were performed to characterize the luminescent properties of the material. Results of SEM observations of the particle sizes are discussed. The most recent data shows that blue luminescence at 450nm can be obtained by the treatment of ZnS phosphor with TNT in this high pressure containment device.

Abstract: The synthesis of fluorescent nanocrystals is receiving a lot of attention for potential application in biological labeling as well as phosphors for field emission devices. Zinc sulphide doped with manganese (ZnS:Mn2+) is one of the most efficient electroluminescent phosphor displaying a wide emission band centred around 590 nm resulting from the intra-ionic transition in Mn2+ ions. We report a unique synthesis of zinc sulphide nanoparticles doped with manganese using a biocompatible passivating agent ‘chitosan’, with bright luminescence peaking at 590 nm. This high luminescence efficiency of the synthesized nanocrystals are ideal for quantum dot based bio-labeling applications. Synthesis of the nanoparticles was carried out by precipitation reaction in aqueous media of zinc acetate and sodium sulphide where manganese acetate was added as the dopant. The obtained nanoparticles were around 4 to 6 nm in size and were found to be stable for months of shelf life. The photoluminescence intensity did not degrade when the colloid was heated up to 65 oC for prolonged periods.

Abstract: An upflow fixed-bed sulphate-reducing reactor has been set up and monitored for the treatment of metal-bearing wastewater. Zinc has been chosen as the target metal to be sequestered from influent water stream at initial concentrations ranging from 50 to 400 mg/l and initial pH values ranging from 3 to 5. Main operating parameters of the reactor, such as the composition and content of electron donor, electron acceptor, sulphate and metal removal capacity, have been monitored during ten months of continuous operation. The results obtained have shown that the reactor has a considerable capacity of completely reducing sulphates for initial concentrations up to 7,200 mg/l, completely removing soluble zinc for initial concentrations up to 400 mg/l and completely removing Total Organic Carbon (TOC), for initial concentrations up to 1,500 mg/l.