Kinetic Modeling and Effect of Process Parameters on Selenium Removal Using Strong Acid Resin

Heavy metal pollution due to the contamination of Selenium above the tolerable limit in the natural environment is a challenging issue that environmental scientists face. This study is aimed at identifying ion exchange technology as a feasible solution to remove selenium ions using 001x7 resin. Parametric experiments were conducted to identify the optimal pH, sorbent dose and speed of agitation. Selenium removal efficiency of 85% was attained at pH 5.0 with 100 mg/L selenium concentration. The increase in resin dose was found to increase removal efficiency. However, metal uptake decreased. The experiments on the effect of concentration proved the negative effect of higher concentrations of selenium on removal efficiency. The ion exchange process was proved to be optimal at an agitation speed of 200 rpm and a temperature of 35 °C. Pseudo second order model was found to fit the kinetic data very well compared to the pseudo-first order model and the pseudo second order rate constant was estimated as 8.725x10-5 g mg-1 min-1 with a solution containing 100 mg/L selenium

A Novel Method to Monitor Sequential Displacement of Capped Ligands in Gold Nanoparticles [abstract]

Nanoscience Poster SessionNanochemistry of ligand displacement reactions has attracted much attention in recent years for the development of myriad of new gold nanomaterials. Gold nanoparticles have shown applications ranging from tumor imaging agent in nanomedicine to single electron devices in information technology. New gold materials are synthesized by exchange of neutral or anionic ligands with thiolated molecules. Completion of ligand substitution reactions in gold nanoparticles are monitored by using UV-Vis spectrometry. However, there are no methods available to monitor the sequence of the ligand substitution reactions. Monitoring and predicting the sequence of ligand substitutions would provide a convenient handle for the design and development of hybrid nanomaterials containing two or more ligands. In this context, we have developed a novel technique utilizing disc centrifuge systems to monitor the sequential displacement of ligands in various gold nanoconstructs. In our studies, we have used gold nanoparticles stabilized with both anionic and neutral ligands. Gold nanoparticles of various different substitutions have been identified and characterized by disc centrifuge systems. Details of substitution reactions and mechanism on monitoring the sequential displacement using strong ligands will be presented

An Effective Strategy for the Synthesis of Biocompatible Gold Nanoparticles Using Cinnamon Phytochemicals for Phantom CT Imaging and Photoacoustic Detection of Cancerous Cells

This is a post-print version of the Pharmaceutical Research Article. The original publication is available at www.springerlink.com. DOI 10.1007/s11095-010-0276-6Purpose: The purpose of the present study was to explore the utilization of cinnamon coated gold nanoparticles (Cin-AuNPs) as CT/optical contrast enhancement agent for detection of cancer cells. Methods: Cin-AuNPs were synthesized by a “Green” procedure and the detailed characterization has been performed by physic-chemical analysis. Cytotoxicity and cellualar uptake studies were carried out in normal human fibroblast and cancerous (PC-3 and MCF-7) cells respectively. The efficacy of detecting cancerous cells was monitored using photoacoustic technique. In vivo biodistribution was studied after IV injection of Cin-AuNPs in mice and a CT phantom model was generated. Results: Biocompatible Cin-AuNPs were synthesized with high purity. Significant uptake of these gold nanoparticles was observed in PC-3 and MCF-7 cells. Cin-AuNPs internalized in cancerous cells facilitate detectable photoacoustic signals. In vivo biodistribution in normal mouse shows steady accumulation of gold nanoparticles in lungs and rapid clearance from blood. Quantitative analysis of CT values in phantom model reveals that the cinnamon phytochemicals coated AuNPs has reasonable attenuation efficiency. Conclusions: The results indicate that these non-toxic Cin-AuNPs can serve as excellent CT/ photoacoustic contrast enhancement agents and may provide a novel approach toward the tumor detection through nanopharmaceuticals.This work has been supported by grants from the National Institutes of Health/National Cancer Institute under the Cancer Nanotechnology Platform program (grant number: 5R01CA119412-01), NIH - 1R21CA128460-01; NIH-SBIR-Contract no. 241, and University of Missouri-Research Board - Program C8761 RB 06-030

Intrinsic electrochemical activity of single walled carbon nanotube–Nafion assemblies

The intrinsic electrochemical properties and activity of single walled carbon nanotube (SWNT) network electrodes modified by a drop-cast Nafion film have been determined using the one electron oxidation of ferrocene trimethyl ammonium (FcTMA+) as a model redox probe in the Nafion film. Facilitated by the very low transport coefficient of FcTMA+ in Nafion (apparent diffusion coefficient of 1.8 × 10−10 cm2 s−1), SWNTs in the 2-D network behave as individual elements, at short (practical) times, each with their own characteristic diffusion, independent of neighbouring sites, and the response is diagnostic of the proportion of SWNTs active in the composite. Data are analysed using candidate models for cases where: (i) electron transfer events only occur at discrete sites along the sidewall (with a defect density typical of chemical vapour deposition SWNTs); (ii) all of the SWNTs in a network are active. The first case predicts currents that are much smaller than seen experimentally, indicating that significant portions of SWNTs are active in the SWNT–Nafion composite. However, the predictions for a fully active SWNT result in higher currents than seen experimentally, indicating that a fraction of SWNTs are not connected and/or that not all SWNTs are wetted completely by the Nafion film to provide full access of the redox mediator to the SWNT surface