Uranium biomineralization by a metal resistant Pseudomonas aeruginosa strain isolated from contaminated mine waste

Uranium biomineralization by a metal-resistant Pseudomonas aeruginosa strain isolated from uranium mine waste was characterized for its potential in bioremediation. Uranium resistance, its cellular localization and chemical nature of uranium-bacteria interaction were elucidated. Survival and uranium biomineralization from mine water were investigated using microcosm experiments. The selected bacterium showed U resistance and accumulation (maximum of 275 mg U g(-1)cell dry wt.) following incubation in 100 mg U L(-1), pH 4.0, for 6 h. Transmission electron microscopy and X-ray diffraction analyses revealed that bioaccumulated uranium was deposited within the cell envelope as needle shaped U-phosphate compounds that attain crystallinity only at pH 4.0. A synergistic involvement of deprotonated phosphate and carboxyl moieties in facilitating bioprecipitation of uranium was evident from FTIR analysis. Based on these findings we attribute the localized U sequestration by this bacterium as innocuous complex to its possible mechanism of uranium resistance. Microcosm data confirmed that the strain can remove soluble uranium (99%) and sequester it as U oxide and phosphate minerals while maintaining its viability. The study showed that indigenous bacteria from contaminated site that can survive uranium and other heavy metal toxicity and sequester soluble uranium as biominerals could play important role in uranium bioremediation.     

Preparation of silica hollow fibers by surface-initiated atom transfer radical polymerization from electrospun fiber templates

Silica hollow fibers were produced by surface-initiated atom transfer radical polymerization (ATRP) from poly(methyl methacrylate-co-vinylbenzyl chloride) (P(MMA-co-VBC)) electrospun fibers combined with sol-gel process and subsequent calcination. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to characterize the intermediate products and the silica hollow fibers. The resulting silica hollow fibers are of high purity with amorphous morphology. The thickness of the hollow fibers is approximately 0.25 µm.     

The analysis of the immobilization mechanism of Ni(II) on Bacillus cereus

This work focused on the identification of biosorption mechanism of Ni(II) by living Bacillus cereus (B. cereus) based on batch experiments and a variety of microscopic equipments. The adsorption equilibrium reached rapidly in 2 h and the maximum nickel adsorption capability of B. cereus was 17.7 mg x g(-1) (dry weight). Atomic force microscopy (AFM) analysis showed that the bacterial surface roughness increased from 7.9 +/- 0.5 nm to 12.6 +/- 1.6 nm during this process. Scanning electron microscopy (SEM) observation confirmed that there was Ni(II) on the bacterial surface. However, transmission electron microscopy (TEM) thin section analysis coupled with energy dispersive X-ray spectroscopy (EDS) revealed that Ni(II) could also be found in the inner portions of the bacteria. Inductive coupled plasma emission spectrometer (ICP-OES) quantitative analysis elucidated that over 70% of the immobilized Ni(II) was binding on the surface of bacteria. X-ray diffraction (XRD) analysis showed that the Ni(II) collected by the bacteria was amorphous. Fourier transform infrared (FT-IR) analysis indicated that amides and carboxylation functional groups might be involved in the coordination of Ni(II).     

Studies on the preparation and characterization of gold nanoparticles protected by dendrons

The preparation and characterization of a group of new composites, namely, gold nanoparticles-cored dendrimers were reported. These materials were obtained by the reduction of hydrogen tetrachloroaurate phase-transferred into organic phase in the presence of poly(benzyl ether) alcohol dendrons with generation 2. These materials, possessing nanometer-sized gold particles at the core and dendritic wedges radially connected to the core by Au-O bonds, were analyzed by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). A possible mechanism of the formation of Gold nanoparticles-cored dendrimers was proposed.     

Production and characterization of nanosized Cu/O/SiC composite particles in a thermal r.f. plasma reactor

An inductively coupled thermal plasma process was used to produce nanosized Cu/SiC composite particles. The powders were characterized by means of chemical analysis, energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), specific surface measurements (BET), X-ray powder diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). X-ray absorption fine structure analysis (EXAFS) was performed to determine the near range order structure of the nanosized particles.     

<Emphasis Type="Italic">In vitro</Emphasis> bioactivity studies of larnite and larnite/chitin composites prepared from biowaste for biomedical applications

Larnite (Ca₂SiO₄) was synthesized by the sol–gel combustion process by using raw eggshell powder as a calcium source and urea as a fuel. The main focus of this work is to convert biowaste into a biomedical material at a low-processing temperature. X-ray diffraction (XRD) pattern confirms the phase purity of the larnite and Fourier transform infrared (FTIR) spectra confirms the presence of characteristic functional groups of larnite. Scanning electron microscopy (SEM) image shows agglomerated particles with cauliflower-like morphology and energy dispersive X-ray spectroscopy (EDX) confirms the presence of the stoichiometric ratio of required elements. Atomic force microscope (AFM) images reveal the presence of pores on the surface of spherical particles. Larnite/chitin composites were fabricated into scaffold with different ratios of bioceramic to biopolymer (70:30, 80:20) to investigate the influence of the polymer content on the apatite formation ability in simulated body fluid (SBF) medium. XRD pattern and FTIR spectra of the scaffold immersed in SBF shows apatite deposition within 5 days. The deposition of hydroxyapatite (HAP) on the scaffold surface increases with the increase in polymer content of the composite.     

Effect of Deposition Time on Properties of Ni–Cu Alloy Films Electrodeposited on ITO Coated Glass Substrates

The structural, magnetic, and surface morphological properties of Ni–Cu films electrodeposited on ITO (indium tin oxide) glass substrates at different deposition times ranging between 2 s and 600 s have been investigated. The structure of the films was studied using X-ray Diffraction (XRD). The XRD results showed that all samples have a face-centered cubic (FCC) structure. From the XRD patterns, it was also found that the crystallographic structure of the films strongly depends on the deposition time. Compositional analysis of Ni–Cu films carried out by energy dispersive X-ray spectroscopy (EDX) indicated that the Ni content within the films increases with increasing deposition time and then almost saturates at deposition time of 600 s. The result of the vibrating sample magnetometer (VSM) measurements revealed that the saturation magnetization increases with increasing Ni content within the film. Atomic force microscopy (AFM) was used to study the topographic properties of Ni–Cu films. It was found that the surface roughness of Ni–Cu alloy films increases with increasing deposition time. Furthermore, the surface texture was found to be isotropic for all films grown at different deposition times.     

A versatile approach for the fabrication of Au hollow nanoparticles based on poly(styrene-co-2-aminoethyl methacrylate) template

The hollow Au nanospheres were successfully prepared by the template method. The poly(styrene-co-2-aminoethyl methacrylate hydrochloride) (P(St-co-AEMH)) nanoparticles synthesized by the emulsion polymerization were used as the templates. After coating by Au colloidal nanoparticles and the formation of Au shells, the interior templates were etched out by sulfuric acid, leading to the formation of Au hollow nanospheres. The structure and morphology of the nanoparticles and hollow nanospheres were carefully investigated by the fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), wide-angle X-ray diffractometer (WAXD), and thermal gravimetric analysis (TGA) techniques.     

Citric acid/ZrO2 nanocomposite inducing thermal barrier and self-cleaning properties on protein fibers

The present research carried out to stabilize nano-ZrO₂ on the wool fabric using citric acid (CA) as a crosslinking agent and sodium hypophosphite (SHP) as a catalyst under UV irradiation. The influence of the amount of nano-ZrO₂ on the performance of wool fiber was investigated by the use of Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDX) and reflectance spectrophotometer (RS). The possible interactions between nano-ZrO₂ particles, cross-linking agent and wool free radicals were elucidated by the FTIR spectroscopy. Results indicated that the stabilized nano-ZrO₂ enhances the thermal stability of wool. Photo-catalytic activities of the coated wool were evaluated through degradation of methylene blue (MB) under UV irradiation.     

Microstructure and composition of biosynthetically synthesised hydroxyapatite

Biosynthetic hydroxyapatite (HA) manufactured utilising the bacterium Serratia sp. NCIMB40259 was characterised using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), energy dispersive X-ray analysis (EDX) scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED). SEM/EDX showed that the non-sintered material consisted mainly of calcium-deficient HA (CDHA) with a Ca/P ratio of 1.61 +/- 0.06 and crystal size (from TEM) of 50 +/- 10 nm. ED analysis of non-sintered powder showed resolvable ring patterns ascribed to (0002), ([Formula: see text]) and (0006) planes of crystalline HA. The crystallinity of the samples improved with heat treatment from approximately 9.4% (non-sintered) to 53% (1,200 degrees C). Samples heated at 600 degrees C and sintered at 1,200 degrees C were identified by XRD and FTIR as mainly CDHA with some sodium calcium phosphate in the sintered samples. Ca/P ratios (SEM/EDX) were 1.62 and 1.52, respectively. Single crystal spot patterns characteristic of HA were seen with commercial HA and Serratia HA heated at 600 degrees C. After sintering at 1,200 degrees C the material consisted of needle-like crystals with a length between 86 and 323 nm (from TEM) or 54-111 nm (from XRD) and lattice parameters of a = 9.441 A and c = 6.875 A. This study indicated that the material produced by Serratia bacteria was initially mainly nanophase calcium deficient hydroxyapatite, which sintered to a more highly crystalline form. With further refinements the method could be used as an inexpensive route for hydroxyapatite production for biomaterials applications.