Absorption Analysis (absorption + analysis)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Layer-By-Layer Dendritic Growth of Hyperbranched Thin Films for Surface Sol,Gel Syntheses of Conformal, Functional, Nanocrystalline Oxide Coatings on Complex 3D (Bio)silica Templates

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
Guojie Wang
Abstract Here, a straightforward and general method for the rapid dendritic amplification of accessible surface functional groups on hydroxylated surfaces is described, with focus on its application to 3D biomineral surfaces. Reaction of hydroxyl-bearing silica surfaces with an aminosilane, followed by alternating exposure to a dipentaerythritol-derived polyacrylate solution and a polyamine solution, allows the rapid, layer-by-layer (LBL) build-up of hyperbranched polyamine/polyacrylate thin films. Characterization of such LBL-grown thin films by AFM, ellipsometry, XPS, and contact angle analyses reveals a stepwise and spatially homogeneous increase in film thickness with the number of applied layers. UV,Vis absorption analyses after fluorescein isothiocyanate labeling indicate that significant amine amplification is achieved after the deposition of only 2 layers with saturation achieved after 3,5 layers. Use of this thin-film surface amplification technique for hydroxyl-enrichment of biosilica templates facilitates the conformal surface sol,gel deposition of iron oxide that, upon controlled thermal treatment, is converted into a nanocrystalline (,9.5,nm) magnetite (Fe3O4) coating. The specific adsorption of arsenic onto such magnetite-coated frustules from flowing, arsenic-bearing aqueous solutions is significantly higher than for commercial magnetite nanoparticles (,50,nm in diameter). [source]

Physically and chemically modified polycarbonate by metal ion implantation

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2008
Rashi Nathawat
Abstract Changes in physical and chemical properties have been studied for polycarbonate (PC) implanted by 100 keV Ni+ with various fluences from 1 × 1014 to 1 × 1016 ions/cm2. Changes in the surface morphology and composition have been observed with atomic force microscopy and X-ray diffraction (XRD). Ni particles as precipitates in PC were observed by cross-section transmission electron microscopy at the 100-nm depth. Ion implantation induces changes in the topography of PC as indicated by a dramatic increase in surface roughness with ion fluence. Implanted metal ions show direct evidence of compound formation on the surface. Chemical changes in the surface region have been observed by Raman spectroscopy and UV,vis spectroscopy. UV,vis absorption analysis indicates a drastic decline in optical band gap from 5.46 to 1.76 eV at an implanted dose of 1 × 1016 ions/cm2. It is shown that partial destruction of the original chemical bonding under ion implantation leads to the creation of new amorphous and graphite-like structures, which are confirmed by Raman spectroscopy. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:143,151, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20130 [source]

Validity of methyl mercury hair analysis: mercury monitoring in human scalp/nude mouse model

JOURNAL OF APPLIED TOXICOLOGY, Issue 4 2008
Grazyna Zareba
Abstract Objective. The grafting of human scalp hair was used as a new application of this method to explore methyl mercury incorporation into human hair and to validate this model for mercury monitoring in hair. Methods. Human scalp grafts were transplanted to athymic BALB/c nude mice. The animals were exposed to methyl mercury either as a single dose i.p. or continuously for 4 months, using ALZET osmotic pumps. The mercury concentration in hair was determined using x-ray fluorescence (XRF) spectrometry by segmental (2 mm) analysis of a single strand, and tissue concentrations were measured by cold vapor atomic absorption analysis. Results. Human scalp hair grown in nude mice showed long-term persistence of human features including the expression of histocompatibility antigens (KAB 3, W 6/32, SF 1-1.1.1) and normal hair morphometry. The disposition of methyl mercury in nude mice followed a one-compartment model with a whole body elimination half-life of 6.7 days (elimination constant, k = 0.1/day). Autoradiographic studies revealed that methyl mercury was rapidly incorporated into areas of the hair follicle undergoing active keratinization. Methyl mercury concentrations in human hair transplanted onto nude mice were two orders of magnitude higher than in blood and attained a mean hair: blood ratio of 217 : 1, similar to ratios reported only in human studies. Conclusions. This study demonstrated that human hair grown on nude mice can record the level of exposure to methyl mercury and can serve as a valuable research tool to study mercury incorporation into human hair. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Probing protein structure and dynamics by second-derivative ultraviolet absorption analysis of cation,, interactions

PROTEIN SCIENCE, Issue 10 2006
Laura H. Lucas
Abstract We describe an alternate approach for studying protein structure using the detection of ultraviolet (UV) absorbance peak shifts of aromatic amino acid side chains induced by the presence of salts. The method is based on the hypothesis that salt cations (Li+, Na+, and Cs+) of varying sizes can differentially diffuse through protein matrices and interact with benzyl, phenyl, and indole groups through cation,, interactions. We have investigated the potential of this method to probe protein dynamics by measuring high resolution second-derivative UV spectra as a function of salt concentration for eight proteins of varying physical and chemical properties and the N -acetylated C -ethyl esterified amino acids to represent totally exposed side chains. We show that small shifts in the wavelength maxima for Phe, Tyr, and Trp in the presence of high salt concentrations can be reliably measured and that the magnitude and direction of the peak shifts are influenced by several factors, including protein size, charge, and the local environment and solvent accessibility of the aromatic groups. Evaluating the empirical UV spectral data in light of known protein structural information shows that probing cation,, interactions in proteins reveals unique information about the influence of structure on aromatic side chain spectroscopic behavior. [source]