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We report the optical properties of polyvinyl-pyrrolidone (PVP) and the influence of PVP concentration on the photoluminescence spectra of the PVP (PL) coated ZnS : Ni nanocrystalline thin films synthesized by the wet chemical method and spin-coating. PL spectra of samples were clearly showed that the 520 nm luminescence peak position of samples remains unchanged, but their peak intensity changes with PVP concentration. The PVP polymer is emissive with peak maximum at 394 nm with the exciting wavelength of 325 nm. The photoluminescence exciting (PLE) spectrum of PVP recorded at 394 nm emission shows peak maximum at 332 nm. This excitation band is attributed to the electronic transitions in PVP molecular orbitals. The absorption edges of the PVP-coated ZnS : Ni0.3% samples that were shifted towards shorter wavelength with increasing of PVP concentration can be explained by the absorption of PVP in range of 350 nm to 400 nm. While the PVP coating does not affect the microstructure of ZnS : Ni nanomaterial, the analyzed results of the PL, PLE, and time-resolved PL spectra and luminescence decay curves of the PVP and PVP-coated ZnS : Ni samples allow to explain the energy transition process from surface PVP molecules to the Ni2+centers that occurs via hot ZnS.

Zn x Fe1−x Fe2O4 nanoparticles (x = 0.0–0.25) were synthesized by the coprecipitation method. Their microstructure was investigated by X-ray diffraction with Rietveld refinement software, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and Fourier transform infrared absorption spectroscopy. Their thermal, magnetic properties were investigated by thermogravimetric analysis and vibrating-sample magnetometer. The nanoparticles exhibited superparamagnetic properties, with a maximum saturation magnetization of 80.2 emu g−1 in H = 11 000 Oe at room temperature for sample with x = 0.20. The Zn nonmagnetic element content is related to the cation distribution in the superlattices and magnetic moment of the particles. The Zn0.15Fe0.85Fe2O4 nanoparticles were coated with polyvinyl pyrrolidone (PVP) with different PVP mass. Their core–shell structure was investigated, the results showed that their chemical stability and saturation magnetization were greater than those of pure Fe3O4. PVP has biological compatibility; thus, Fe0.85Zn0.15Fe2O4/PVP0.75 nanocomposite has the potential to be widely used in medical biology, science and technology.

The synthesis of Fe 3 O 4 /polyaniline (Fe 3 O 4 /PANI) nanomaterials by a chemical method is presented in this paper. The X-ray diffraction (XRD) shows that the lattice constant a = 8.376 A 0 and the particle size of is about 14.5 nm for all samples, since polymer cannot in uence the crystal structure of Fe 3 O 4. The transmission electron microscopy (TEM) images show that the Fe 3 O 4 grain sizes vary from 13 nm to 20 nm. The results of Raman spectral analysis and thermal gravimetric analysis reveal that the PANI partly forms in the Fe 3 O 4 /PANI nanomaterials samples. Thus, the grain size of Fe 3 O 4 /PANI nanomaterials is about of 25-30 nm, which has been con rmed by a scanning electron microscope (SEM). The saturated magnetic moment of Fe 3 O 4 /PANI samples is decreased from 66 emu/g to 39.7 emu/g with PANI content varying from 5% to 15%. However, Fe 3 O 4 /PANI nanomaterials are stable on chemical-physical properties and lead to improve an arsenic adsorption ability. In addition, Fe 3 O 4 /PANI sample with PANI 5% content has the highest arsenic adsorption ability in pH 7. In strong acidic or basic media, the arsenic adsorption of magnetic nanoparticles is insigni cant. The results suggest the desorb can be conducted at pH 14 then the materials could reabsorb in further trials.

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.

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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].

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