V. I. Fediv

Synthesis of Capped AII

The conditions for growing CdS nanoparticles suitable for the visualization of biological tissues were theoretically studied and experimentally checked. The optimal ranges for pH values and precursors’ concentrations were determined. The applicability of the mercaptoethanol-capped nanoparticles for in vitro luminescence visualization of several cellular forms in histological specimens of human placenta has been proven.

Enhancement of polymer endurance to UV light by incorporation of semiconductor nanoparticles

Improvement of polyvinyl alcohol stability against ultraviolet (UV) illumination is achieved by introducing cadmium sulfide (CdS) nanoparticles into the polymeric matrix. Enhancement of stability is analyzed by optical characterization methods. UV protection is achieved by diminishing the probability of photo-activated formation of defects in polymer. The sources of polymer protection are the lowering of the efficiency of polymer excitation via partial absorption of incident light by the embedded nanoparticles as well as the de-excitation of the macromolecules that have already absorbed UV quanta via energy drain to nanoparticles. Within the nanoparticles, the energy is either dissipated by conversion to the thermal energy or reemitted as visible-range photoluminescence quanta.

Interfacial bonding in a CdS/PVA nanocomposite: A Raman scattering study.

Raman spectroscopy is employed to characterize the bonding between CdS nanoparticles (NPs) and a polyvinyl alcohol (PVA) as well as structural changes in the polymeric matrix caused by incorporation of NPs. It is shown that after the formation of CdS NPs the vibrations of carbonyl groups in acetate residuals of PVA and of C-O groups at the macromolecules ends disappear. Formation of NPs also leads to an increased degree of hydrogen bonding and crystallinity of the hybrid material as compared with the unloaded polymer. The observed changes are ascribed to the formation of coordinative bonds and hydrogen between the CdS nanoparticles and polymeric macromolecules. The scheme of this interfacial bonding is also proposed.

Magnetic and magneto-optical properties of CdS:Mn quantum dots in PVA matrix

We have studied the magnetic and magneto-optical properties of CdS:Mn quantum dots in polyvinyl alcohol matrix synthesized by co-precipitation method. The size of quantum dots was estimated by means of absorption spectroscopy. The results of measurements of magnetic susceptibility as a function of temperature and spectral dependence of the Faraday rotation of CdS:Mn quantum dots / polyvinyl alcohol composites are presented. In this work magnetic susceptibility was investigated by Faradays method at the temperatures of (78-300) K in magnetic fields of (0.05-0.8) T. The inverse magnetic susceptibility as a function of temperature follows a Curie Weiss law. Formation of ferromagnetic coupling between magnetic ions is supposed. Magneto-optical Faraday rotation has been investigated in the wavelength region (400-700) nm at temperature 300 K in a magnetic field up to 5 T. Sign of the Verdet constant is found to be negative.

Retardation of nanoparticles growth by doping

The process of doping of CdS nanoparticles with Mn during colloidal synthesis is analyzed by EPR and optical studies. Analysis of EPR results demonstrated that Mn2+ ions are successfully incorporated into the nanoparticles and occupy the crystal sites both in the bulk of a NP and near the surface of a NP. Optical absorption measurements revealed the retardation of absorption edge shift during the growth for Mn-doped CdS NPs as compared to the undoped CdS NPs. It was concluded that the presence of Mn in the solution leads to the inhibition of NPs growth.

Optical and magneto-optical diagnostics of polymer/nanoparticles colloidal solutions and composites

In this work we report on peculiarities of technique for correct measurements of optical transmittance, optical density and Faraday rotation spectra of colloidal semiconductor nanoparticles and nanocomposites. As an example we have used CdS:Mn nanoparticles embedded in polyvinylalcohol (PVA) matrix. With the decrease of the size of CdS:Mn nanoparticles, the absorption exciton band was shifted to shorter wavelengths as a result of quantum confinement effect. In order to observe clearly this shift we have used several samples with the same average nanoparticle size, but with different sample thicknesses. It was made analysis of the obtained data on optical spectra for nanocomposites with comparison for bulk semiconductor materials. Similar methodology was applied for magneto-optical spectra of colloidal solutions and nanocomposites.

Photoluminescence Excitation in Nanocomposites Polyvinylpyrrolidone/ZnO

ZnO nanoparticles embedded in polyvinylpyrrolidone matrix were fabricated in situ by colloidal method with environmentally friendly reaction conditions. The colloid was used to form solid nanocomposite polyvinylpyrrolidone/ZnO, and optical properties of the material were studied. Two types of emission were identified in the nanocomposite: one originates from the polymeriс matrix another is related the defect states in ZnO nanoparticles. Specific way of light emission excitation via energy transfer from the polymeric matrix to nanoparticles was observed.

Luminescent and Optically Detected Magnetic Resonance Studies of CdS/PVA Nanocomposite

A series of solid nanocomposites containing CdS nanoparticles in polymeric matrix with varied conditions on the interface particle/polymer was fabricated and studied by photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. The results revealed interface-related features in both PL and ODMR spectra. The revealed paramagnetic centers are concluded to be involved in the processes of photo-excited carriers relaxation.

Synthesis of Capped AIIBVI Nanoparticles for Fluorescent Biomarkers

The conditions for growing CdS nanoparticles suitable for the visualization of biological tissues were theoretically studied and experimentally checked. The optimal ranges for pH values and precursors’ concentrations were determined. The applicability of the mercaptoethanol-capped nanoparticles for in vitro luminescence visualization of several cellular forms in histological specimens of human placenta has been proven.

Effects of codoping in ZnO-based semimagnetic semiconductor thin films

Single doped Zn1−xMnxO, Zn1−xFexO and codoped Zn1−x−yMnxFeyO, Zn1−x−yMnxSnyO, Zn1−x−yMnxLiyO, Zn1−x−yFexAlyO thin films were grown on sapphire and glass substrate by pulsed laser deposition and RF sputtering techniques. No secondary phases was detected from XRD analysis. Among the studied oxide films single doped with Fe and codoped with (Mn,Fe) and (Fe, Al) exhibit n-type conductivity and room temperature ferromagnetic behaviour. For the films codoped with (Mn, Sn) formation of clusters including nanowire-like structures was shown from AFM analysis. Optical and magnetooptical studies suggest of Mn, Fe, Sn and Li substitution for Zn2+ ions in ZnO lattice.