In this article, we present the optical properties of thin films containing Mn-doped ZnS nanocrystals synthesised by the chemical method. The ZnS nanoparticles within the polymer matrix (polyvinyl alcohol) were investigated by SEM and TEM images and analysed by X-ray diffraction. The effect of polymer concentration on the direct band gap of Mn-doped ZnS thin films was calculated from the data for absorption measurements. The values of the band gap are in the range of 3.73-3.90 eV. In addition, we discuss the photoluminescence of these films.
IntroductionZnS nanomaterials are semiconductor materials with direct band gap larger than that of ZnO. The direct band gap of ZnS is 3.6 eV for a bulk ZnS material, and this can reach 3.98 eV for a ZnS nanomaterial at 300 K [1], or 4.4 eV [2] in a Wurzite structure. Moreover, the melting temperatures of A II B VI materials are very high. ZnS is therefore considered one of the most promising materials which find applications in optoelectronic devices, blue emitting diodes, electroluminescent devices and others [3,4].ZnS nanoparticles radiate luminescence with a wavelength of 420-480 nm. In order to receive radiation in the visible region, ZnS used to be doped by transition metals, such as Mn 2þ , Cu 2þ and Ni 2þ [5][6][7][8]. It is known that the optical properties of nanomaterials show they are highly sensitive to synthesis conditions [9][10][11] and are dependent on the type on precursor used, pH level, doping concentration and temperature regime. It is also known that the direct band gap of nanomaterials can be controlled by doping, using polymer coating [12] and manipulating synthesis conditions. As certain polymers (polyvinyl alcohol (PVA), polyacrylic, polystyrene) are transparent to visible light, they will not have any effect on the emission wavelengths of ZnS nanoparticles when they are being diffused into the polymer matrix. On the contrary, these polymers can prevent nanoparticles from aggregating, in the mechanism of steric and electrostatic stabilisation. Thus, polymer coating plays a role in providing a protective environment for ZnS nanoparticles [1,2].Previous results on the optical properties of ZnS:Mn showed that the luminescence intensity increased considerably with an optimal nominal Mn concentration of about 9-10% [13].
Arsenic and heavy metals present in wastewater were determined before and after treatment on the adsorbent column is significant science in Vietnam. In this study, we used the available natural materials, it is powdered and Fe (0) yellow sand, MnO2 powder under the granules used as adsorbent in the column. The survey materials were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM). These study showed that the material consists of magnetite Fe3O4 38.18 %, hematite Fe2O3 12.73 %, wuestite FeO 16.36 % of the beneficial minerals for the adsorption of heavy metals. The results showed that the material can remove As and some heavy metals out of the environment, in particular: arsenic adsorption capacity (169.65 mg/kg) and some metals such as Mn, Fe, Cu, Pb, Cd, respectively: 6616.05, 6664.24, 426.07, 143.06 and 120.21 mg/kg and maintained for a period of 4 days. This shows good potential applications of sand and iron powder Fe (0) in the treatment of heavy metal pollution by column adsorption method.
This paper reports the application of the Ru 2þ , Cu þ , and Fe 2þ complexes in form of RuL 2 (SCN) 2, CuL 2 (SCN) 2 À for dye-sensitized solar cell (DSSC) development. The calculation results, given by quantum chemistry, demonstrated that the complex containing copper is more suitable than the one containing iron. The modification of Cu(I) complex by using various numbers of ligands enhanced photon absorption capacity as well as the absorption range. The addition of an organic ligand such as an electron attraction group to the benzene ring gave a better result as compared to the inorganic ones. Based on the analysis conducted, CuM 2 (SCN) 2 À is considered as potential material for N3 replacement.
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