Synthesis route and optical characterization of CdS:Mn/polyvinyl alcohol nanocomposite

CdS nanoparticles doped with Mn have been synthesized in aqueous solution by using polyvinyl alcohol (PVA) as a capping reagent. Influence of the polymer concentration on the size and concentration of the nanoparticles was studied using transmission electron microscopy and optical absorption. Incorporation of Mn2+ ions into CdS nanoparticles was confirmed by photoluminescence (PL) intensity increase and band shift with Mn concentration. The PL studies proved that localization of Mn ions (inside the nanoparticles or on the surface) depends on the sequence of synthesis steps. The bleaching of the low-energy PL band of the low-doped CdS:Mn nanoparticles by surface modification with a Cd(OH)2 layer proves suppression of the emission related to surface states

Tunable electrophysical properties of composites nano-CdS/polyvinyl alcohol

Electrical d.c. conductivity of nano-CdS/polyvinyl alcohol composites with different nanoparticle concentrations and its temperature dependence were studied. The composites demonstrate increasing resistivity with CdS nanoparticles content. The currentevoltage characteristics of composites exhibit non-ohmic superlinear behavior that is interpreted in terms of space-charges-limited currents. Temperature dependence of resistivity is characterized by high temperature coefficient of resistivity which is favorable for applications in flexible, easy-to-shape thermistors. The tunability of the thermal sensitivity of CdS/polyvinyl alcohol composites was analyzed

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 prove

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

“Multicoloured” superradiance in quantum heterostructures

The analysis of photoluminescence of heterostructures with single elastic-strained In₀.₁₆Ga₀.₈₄As quantum wells is carried out in this work. It is shown, that filling of a quantum well with many quantum subbands results in appearance multicolour superradiance

Analysis of conditions for synthesis of CdS:Mn nanoparticles

The detailed analysis of the synthesis of CdS:Mn nanoparticles in polyvinyl alcohol polymeric matrix is presented and the ranges of optimal growth parameters are determined. The estimated values of parameters were used to produce solutions of CdS:Mn nanoparticles and corresponding solid composites. The sizes of nanoparticles and structure of composite films were characterized by electron microscopy methods, optical properties were probed using photoluminescence methods

Evolution of CdS:Mn nanoparticle properties caused by pH of colloid solution and ultrasound irradiation

The effects of pH value and precursors concentrations in the growth solution as well as of ultrasound irradiation on the properties of CdS:Mn nanoparticles in PVA matrix are studied. Analysis of the photoluminescence spectra indicates that the increase of the pH value in the growth solution leads to the increase of the density of surface electron states that participate in radiative transitions and to the enlargement of CdS:Mn nanoparticles.We discuss a stabilization of the sizes of CdS:Mn nanoparticles at pH=6 and change of nanoparticle size with decreasing pH value at elevated concentrations of ions HS- . It is shown that in the ultrasound-treated samples the size of the particles does not depend on pH value. The effects of ultrasound result primarily from acoustic cavitation. It is demonstrated that the action of two external factors (the value of the medium pH and ultrasound treatment) on the characteristics of nanoparticles is correlated

Synthesis of Mn2+-doped CdS nanoparticles covered with different adsorptive layers and their application as biosensors

Colloidal CdS:Mn nanoparticles were synthesized in water solutions of the polymer polyvinyl-pyrrolidone (PVP), the surfactant cetyl-trimethyl-ammonium bromide (CTAB) and the mixture of PVP and CTAB. The sizes of nanoparticles were determined by electron microscopy and optical absorption methods. The growth media influence on photoluminescence of nanoparticles has been studied. It has been shown that the chemical composition and structure of the adsorptive layer on the surface of nanoparticles can be used as a technological tool to control their light emission. The possibility to use CdS:Mn NPs grown in PVP as light-emitting labels in biological media has been demonstrated

Instability of homogeneous composition of highly strained quantum wells in heterostructures GaAs/InxGa₁₋xAs/GaAs

InxGa₁-xAs QW-layers embedded in GaAs matrix have been characterized by photoluminescence (PL). The relation between the PL parameters and mismatch of the lattice parameters of the layer and matrix was established. In highly strained layers several PL bands were observed instead one band. This is probably a result of alternating content of In raised only in highly strained layers

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