Phosphorescence of CdS nanoparticles in polymer matrix as an indication of host-guest interaction

We report on the observation of the long-lasting low-temperature photoluminescence decay in the hybrid system nano-CdS/polyvinyl alcohol with a characteristic time of about 1.7 s. The origin of the phosphorescence is ascribed to the accumulation of photo-excited excitons in the traps within the polymeric matrix with subsequent transfer of the excitation to the embedded CdS nanoparticles

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

Hydrodynamic dispersion in long microchannels under conditions of electroosmotic circulation: II. Electrolytes

This work describes the steady-state transport of an electrolyte due to a stationary concentration difference in straight long channels under conditions of electroosmotic circulation. The electroosmotic flow is induced due to the slip produced at the charged channel walls. This flow is assumed to be compensated by a pressure-driven counterflow so that the net volume flow through the channel is exactly zero. Owing to the concentration dependence of electroosmotic slip, there is an involved coupling between the solute transfer, hydrodynamic flow and charge conservation. Nevertheless, for such a system the Taylor–Aris dispersion (TAD) theory is shown to be approximately applicable locally within an inner part of the channel for a wide range of Péclet numbers (Pe) irrespective of the concentration difference. Numerical simulations reveal only small deviations from analytical solutions for the inner part of the channel. The breakdown of TAD theory occurs within boundary regions near the channel ends and is related to the variation of the dispersion mechanism from the purely molecular diffusion at the channel ends to the hydrodynamic dispersion within the inner part of the channel. This boundary region is larger at the lower-concentration channel edge and its size increases nearly linearly with Pe number. It is possible to derive a simple analytical approximation for the inner profile of cross-section-averaged electrolyte concentration in terms of only few parameters, determined numerically. Such analytical approximations can be useful for experimental studies of concentration polarization phenomena in long microchannels.Peer ReviewedPostprint (author's final draft

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

Effects of Ultraviolet Light on Optical Properties of Colloidal CdS Nanoparticles Embedded in Polyvinyl Alcohol (PVA) Matrix

CdS nanoparticles have been synthesized in aqueous solution using polyvinyl alcohol (PVA) as a capping reagent. The effects of exposure by ultraviolet (UV) light on optical properties of nanocomposites consisting of colloidal CdS nanoparticles and a polymer PVA matrix were studied by employing photoluminescence (PL) spectroscopy. It is shown that UV-induced changes of the photoluminescence intensity in PVA are caused by creation and healing of non-radiative recombination centers. It is also concluded that in the nanocomposites, the UV-induced changes of the PL intensity are predominantly governed by processes at the NP/PVA interfaceFinancial support from the Swedish Institute via Visby program is greatly appreciated

Short Time Dynamic Interfacial Tension as Measured with Capillary Pressure Technique

Dynamic interfacial tension measurements in the short time range are a major request for controlling interfacial processes in modern, highly dynamic technologies. Capillary pressure measurements for growing and oscillating drops represent a good way to fulfil these requirements. The corresponding quantitative data analysis, however, requires the solution of rather complex theories on the hydrodynamics of growing drops and the adsorption dynamics at the drop surface and possible mass transfer across interfaces for liquid/liquid systems

Role of the host polymer matrix in light emission processes in nano-CdS/poly vinyl alcohol composite

Participation of a polymericmedia in light-emitting processes of composite nano-CdS/polyvinyl alcohol is studied by probing different absorption-emission routes via adjustment of excitation wavelengths. It is shown that the polymeric constituent of the composite contributes chiefly to the photoluminescence excitation processes via absorption and excitation transfer to the embedded CdS nanoparticles while the composite emission occurs mostly within the nanoparticles.Financial support from the Swedish Institute via Visby program is greatly appreciated

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

Search for massive WH resonances decaying into the l nu b(b)over-bar final state at root s=8 TeV

Peer reviewe