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Visible Spectroscopy (visible + spectroscopy)
Selected AbstractsDimeric 2,2,-Bipyridylruthenium(II) Complexes Containing 2,2,-Bis(1,2,4-triazin-3-yl)-4,4,-bipyridine-Like Bridging Ligands: Syntheses, Characterization and DNA BindingEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004Cai-Wu Jiang Abstract Three new bridging ligands 2,2,-bis(1,2,4-triazin-3-yl)-4,4,-bipyridine (btb), 2,2,-bis(1,2,4-triazino[5,6-f]acenaphthylen-3-yl)-4,4,-bipyridine (btapb), 2,2,-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4,-bipyridine (bdptb) and their dimeric 2,2,-bipyridylruthenium(II) complexes [Ru(bpy)2(btb)Ru(bpy)2]4+ (1), [Ru(bpy)2(btapb)Ru(bpy)2]4+ (2), [Ru(bpy)2(bdptb)Ru(bpy)2]4+ (3) have been synthesized and characterized by elemental analysis, fast atom bombardment (FAB) mass spectrometry or electrospray mass spectrometry (ES-MS), 1H NMR and UV/Visible spectroscopy. The binding behavior of these dimeric complexes with calf thymus DNA (CT-DNA) was investigated by electronic absorption spectroscopy, viscosity measurements, and equilibrium dialysis experiments. The hypochromism of the metal-ligand charge transfer (MLCT) band in the electronic absorption spectra of the dinuclear complexes 1, 2, and 3 is 8.7%, 19% and 33%, respectively, with bathochromic shifts of 5, 5 and 14 nm, respectively. The binding constants are 7.5×104M,1, 4.8×105M,1 and 7.6×105M,1, respectively. Increasing the size of the plane of the bridging ligand increases the hydrophobicity of their complexes, leading to stronger binding by the complexes to calf thymus DNA. The effect of increasing concentrations of these novel dimeric ruthenium(II) complexes on the relative viscosities of CT-DNA is less notable than that of well-known intercalators such as [Ru(bpy)2(dppz)]2+. The equilibrium experiments showed that ,,,3 binding is stronger than ,,,3 binding to CT-DNA. This is the first example of a dinuclear complex binding enantioselectively to CT-DNA measured by equilibrium dialysis. The experiments suggest that the three complexes may be DNA groove binders. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Design, synthesis and properties of synthetic chlorophyll proteinsFEBS JOURNAL, Issue 11 2001Harald K. Rau A chemoselective method is described for coupling chlorophyll derivatives with an aldehyde group to synthetic peptides or proteins modified with an aminoxyacetyl group at the ,-amino group of a lysine residue. Three template-assembled antiparallel four-helix bundles were synthesized for the ligation of one or two chlorophylls. This was achieved by coupling unprotected peptides to cysteine residues of a cyclic decapeptide by thioether formation. The amphiphilic helices were designed to form a hydrophobic pocket for the chlorophyll derivatives. Chlorophyll derivatives Zn-methylpheophorbide b and Zn-methyl-pyropheophorbide d were used. The aldehyde group of these chlorophyll derivatives was ligated to the modified lysine group to form an oxime bond. The peptide,chlorophyll conjugates were characterized by electrospray mass spectrometry, analytical HPLC, and UV/visible spectroscopy. Two four-helix bundle chlorophyll conjugates were further characterized by size-exclusion chromatography, circular dichroism, and resonance Raman spectroscopy. [source] Dependence on substrate temperature of the conformation and structure of a poly[3-(4-octyloxyphenyl)thiophene] (POOPT) thin film obtained by matrix assisted pulsed laser evaporation (MAPLE)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009Valeria Califano Abstract In this paper, the substrate temperature influence on the structural and main opto-electronic properties of poly[3-(4-octyloxyphenyl)thiophene] (POOPT) films, deposited by matrix assisted pulsed laser evaporation (MAPLE), was analyzed. Fourier transform infrared analysis of films was performed to verify that laser irradiation has not induced polymer modifications or decomposition, confirming the reliability and high control of the MAPLE deposition technique. UV,Visible spectroscopy allowed gaining insights about films conformation and packing, while conductivity values have been measured by basic current,voltage measurements. In agreement with the experimental observations reported for other growth techniques, our results highlight the substrate temperature effect in promoting the film structural organization and improving their charge transport capability. At substrate temperature of 453,K, films deposited by MAPLE show a higher conjugation length in comparison with spin-coated films. The substrate temperature increase also favors side-chains commutation to different steric configurations. [source] ZnO nanocrystallites obtained by oxidation of zinc arachidate , arachidic acid composite multilayersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007Sukhvinder Singh Abstract ZnO nanocrystallites were prepared by the oxidation of Zinc Arachidate,Arachidic Acid (ZnA,AA) composite multilayers grown on quartz and freshly cleaved mica substrates. Control of zinc content in the multilayers was achieved by the manipulation of the subphase pH and the variation in the number of monolayers transferred. FTIR studies of multilayers show a gradual decrease in ZnA content as the subphase pH is reduced. X-ray reflection studies show the presence of a single layered structure in all the as-deposited multilayers transferred at different subphase pH. These observations suggest molecular level mixing of ZnA and arachidic acid molecules. The precursor multilayers were oxidized in the temperature range of 100,700 °C. The formation of ZnO is confirmed by UV,Visible spectroscopy. Atomic force micrographs show that the oxidation treatment resulted in either large agglomerates of ZnO nanocrystallites or isolated nanocrystallites, depending on the zinc content of the precursor multilayers. Typically, 7 monolayers ZnA,AA transferred at subphase pH of 5.0 on mica and oxidized at 700 °C resulted in uniformly distributed, isolated and nearly mono-dispersed nanocrystallites of size 11 ± 3 nm. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ZnO nanostructures for photovoltaic cellsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010Belete A. Gonfa Abstract In this work the use of different ZnO nanostructures has been studied to assess the effect of morphology and surface modification on the performance of photovoltaic devices. ZnO nanostructures (nanoparticles, nanowires and nanofibres) have been produced by different techniques, and surface modified with pyrene-1-carboxylic acid (PCA). The materials prepared were characterized by XRD, UV,Visible spectroscopy, TEM and SEM. The photovoltaic devices have been prepared in two different configurations: glass/ITO/PEDOT:PSS/photoactive layer/Al and glass/ITO/ZnO/photoactive layer/PEDOT:PSS/Ag paste using spin coating and were characterized by current,voltage characteristics measurement under simulated standard illumination conditions. Whilst ZnO nanoparticles yielded the best results, surface modification with PCA resulted in solar cells with higher short circuit current densities but lower open circuit voltage pointing to a better carrier collection but also higher recombination. [source] Characterization of an unusual folding pattern in a catalytically active guanine quadruplex structureBIOPOLYMERS, Issue 6 2006Pinaki R. Majhi Abstract In the presence of certain metal ions, DNA and RNA can form guanine quadruplex structures, which have been proposed to play a functional role in a variety of biological processes. An 18-nucleotide DNA oligomer, PS2.M, d(GTG3TAG3CG3T2G2), was previously reported to bind hemin and the resulting complex exhibited peroxidase activity. It was proposed that PS2.M folds unimolecularly into an antiparallel quadruplex with unusual, single-base loops and terminal guanines positioned in adjacent quartets. Here we describe structural and stability properties of PS2.M alone in different buffers and metal ions, using gel electrophoresis, circular dichroism (CD), ultraviolet (UV)-visible spectroscopies, and one-dimensional 1H nuclear magnetic resonance (NMR). Native gel behavior of PS2.M in the presence of either Na+ or Pb2+ suggests the formation of unimolecular structures but, in the presence of K+, both unimolecular and multistranded structures are observed. In the presence of Pb2+ ions, PS2.M forms a unimolecular quadruplex containing three guanine quartets. CD titrations reveal that binding of Pb2+ ions to PS2.M is stoichiometric, and a single lead cation suffices to fully fold PS2.M. The PS2.M,Na+ system also forms a similar unimolecular quadruplex. In the presence of K+, the PS2.M,K+ system forms mixed species. With increasing time and PS2.M concentration, the contribution of unimolecular species decreases while that of multimolecular species increases, and this behavior is independent of buffer media. These results suggest that the catalytically active form, studied in the presence of K+, may be a parallel, multistranded quadruplex rather than an antiparallel, unimolecular quadruplex. © 2006 Wiley Periodicals, Inc. Biopolymers 82:558,569, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Helical- and ahelical-dependent chiral recognition mechanisms in capillary electrophoresis using amylose as the selectorELECTROPHORESIS, Issue 8 2009Weili Wei Abstract The present study discovered that helical structures of amylose were not always responsible for its chiral recognition abilities in CE. Several enantiomers with different structures were selected as models. Based on ultraviolet,visible spectroscopy and 13C NMR measurements, it was found that helical structures were gradually destroyed by temperature elevation and almost entirely transformed to extended ahelical structures above 60°C. Then, CE and 1H NMR chiral recognitions were investigated at different temperatures; chiral selectivity of the enantiomers varied in two different ways. Summarily, helical structures were necessary only for chiral separations of the enantiomers with small (<0.78,nm) and flexible molecular structures. However, for the gauche enantiomers (>0.78,nm) with high steric hindrances over their chiral centers, ahelical structures alone can realize chiral recognitions. By using iodine as a helix including competitor, it was further proved that helical structures functioned through the inclusive complexations only in the chiral separations of small enantiomers and had no effect for the others. The underlying mechanisms of the functions of helical and ahelical structures in molecular level were discussed as well. [source] Reactivity of the heme,dioxygen complex of the inducible nitric oxide synthase in the presence of alternative substratesFEBS JOURNAL, Issue 1 2006David Lefèvre-Groboillot Single turnover reactions of the inducible nitric oxide synthase oxygenase domain (iNOSoxy) in the presence of several non ,-amino acid N -hydroxyguanidines and guanidines were studied by stopped-flow visible spectroscopy, and compared with reactions using the native substrates l -arginine (l -arg) or N, -hydroxy- l -arginine (NOHA). In experiments containing dihydrobiopterin, a catalytically incompetent pterin, and each of the studied substrates, l -arg, butylguanidine (BuGua), para -fluorophenylguanidine (FPhGua), NOHA, N -butyl- and N -(para -fluorophenyl)- N,-hydroxyguanidines (BuNOHG and FPhNOHG), the formation of a iron(II) heme,dioxygen intermediate (FeIIO2) was always observed. The FeIIO2 species then decayed to iron(III) iNOSoxy at rates that were dependent on the nature of the substrate. Identical reactions containing the catalytically competent cofactor tetrahydrobiopterin (BH4), iNOSoxy and the three N -hydroxyguanidines, all exhibited an initial formation of an FeIIO2 species that was successively converted to an FeIIINO complex and eventually to high-spin iron(III) iNOSoxy. The formation and decay kinetics of the FeIIINO complex did not vary greatly as a function of the N -hydroxyguanidine structure, but the formation of FeIIINO was substoichiometric in the cases of BuNOHG and FPhNOHG. Reactions between BH4 -containing iNOSoxy and BuGua exhibited kinetics similar to those of the corresponding reaction with l -arginine, with formation of an FeIIO2 intermediate that was directly converted to high-spin iron(III) iNOSoxy. In contrast, no FeIIO2 intermediate was observed in the reaction of BH4 -containing iNOSoxy and FPhGua. Multi-turnover reaction of iNOS with FPhGua did not lead to formation of NO or to hydroxylation of the substrate, contrary to reactions with BuGua or l -arg. Our results reveal how different structural and chemical properties of NOS substrate analogues can impact on the kinetics and reactivity of the FeIIO2 intermediate, and support an important role for substrate pKa during NOS oxygen activation. [source] Binding of ligands originates small perturbations on the microscopic thermodynamic properties of a multicentre redox proteinFEBS JOURNAL, Issue 9 2005Carlos A. Salgueiro NMR and visible spectroscopy coupled to redox measurements were used to determine the equilibrium thermodynamic properties of the four haems in cytochrome c3 under conditions in which the protein was bound to ligands, the small anion phosphate and the protein rubredoxin with the iron in the active site replaced by zinc. Comparison of these results with data for the isolated cytochrome shows that binding of ligands causes only small changes in the reduction potentials of the haems and their pairwise interactions, and also that the redox-sensitive acid,base centre responsible for the redox,Bohr effect is essentially unaffected. Although neither of the ligands tested is a physiological partner of cytochrome c3, the small changes observed for the thermodynamic properties of cytochrome c3 bound to these ligands vs. the unbound state, indicate that the thermodynamic properties measured for the isolated protein are relevant for a physiological interpretation of the role of this cytochrome in the bioenergetic metabolism of Desulfovibrio. [source] Comparison of poly(o -anisidine) and poly(o -anisidine- co -aniline) copolymer synthesized by chemical oxidative methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010J. Longun Abstract In this study, poly(o -anisidine) [POA], poly(o -anisidine- co -aniline) [POA- co -A], and polyaniline [PANi] were chemically synthesized using a single polymerization process with aniline and o -anisidine as the respective monomers. During the polymerization process, p -toluene sulfonic acid monohydrate was used as a dopant while ammonium persulfate was used as an oxidant. N -methyl-pyrolidone (NMP) was used as a solvent. We observed that the ATR spectra of POA- co -A showed features similar to those of PANi and POA as well as additional ones. POA- co -A also achieved broader and more extended UV,vis absorption than POA but less than PANi. The chemical and electronic structure of the product of polymerization was studied using Attenuated Total Reflectance spectroscopy (ATR) and UV,visible spectroscopy (UV,vis). The transition temperature of the homopolymers and copolymers was studied using differential scanning calorimetry and the viscosity average molecular weight was studied by using dilute solution viscometry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis of metal (Fe or Pd)/alloy (Fe,Pd)-nanoparticles-embedded multiwall carbon nanotube/sulfonated polyaniline composites by , irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Kakarla Raghava Reddy Abstract Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5-diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe,Pd alloy nanoparticles were embedded into the MWCNT,SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with , radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of , radiation. The existence of metallic/alloy particles in the MWCNT,SPAN matrix was further ascertained through characterization by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet,visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe,Pd nanoparticles of various sizes in the MWCNT,SPAN matrices. There were changes in the electronic properties of the MWCNT,SPAN,M composites due to the interaction between the metal nanoparticles and MWCNT,SPAN. Metal-nanoparticle-loaded MWCNT,SPAN composites (MWCNT,SPAN,M; M = Fe, Pd, or Fe,Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT,SPAN,M composites was approximately 1.5 S cm,1, which was much higher than that of SPAN (2.46 × 10,4 S cm,1). Metal/alloy-nanoparticle-embedded, MWCNT-based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355,3364, 2006 [source] Facile synthesis, characterization, and potential applications of two kinds of polymeric pH indicators: Phenolphthalein formaldehyde and o -cresolphthalein formaldehydeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005Zhihong Liu Abstract Two kinds of applicable polymeric pH indicators were synthesized by the reaction of phenolphthalein and o -cresolphthalein with formaldehyde under alkaline conditions by a one-pot method. The synthesized products were fully characterized with Fourier transform infrared, 1H NMR, ultraviolet,visible spectroscopy, and gel permeation chromatography. The results indicated that the reaction was a typical phenol formaldehyde reaction. The dosage of formaldehyde and the reaction time were well controlled to obtain soluble polymers, instead of crosslinked products. The polymeric-pH-indicator-immobilized poly(vinyl alcohol) (PVA) membranes were easily fabricated and had good long-term stability under highly basic conditions and a fast equilibrium response. Moreover, the phenolphthalein formaldehyde immobilized PVA membrane had a linear response from pH 10.0 to 14.0, and so it has promise as a optical transducer for high pH value determinations. The o -cresolphthalein formaldehyde immobilized PVA membrane had a nonlinear response from pH 9.0 to 13.0. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1019,1027, 2005 [source] 1,5-Diphenyl-1,4-diyn-3-one: A highly efficient photoinitiatorJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2005Robert Liska Abstract In a continuation of our research on new chromophores for photoinitiators (PIs), we investigated a triple-bond-containing benzophenone derivative. 1,5-Diphenyl-1,4-pentadiyn-3-one (2) was prepared from phenylacetylene and ethyl formate by a one-pot reaction. Differential scanning photocalorimetry experiments in lauryl acrylate of 2 showed surprisingly high activity for the double-bond conversion and rate of polymerization at the lowest PI concentrations and even without any coinitiator. By the application of monomers with abstractable hydrogens, significant improvement in the photoreactivity was observed. Ultraviolet,visible spectroscopy revealed strong absorption up to 350 nm. Steady-state photolysis experiments proved that the photochemistry of this compound was faster than that of benzophenone. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 101,111, 2005 [source] Synthesis and characterization of electrically conducting poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004P. Savitha Abstract A series of poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymers combining the features of high conductivity and processibility are synthesized and characterized by a number of techniques including 1H NMR; thermogravimetry; IR, Raman, and UV,visible spectroscopy; scanning electron microscopy; and X-ray diffraction. The copolymers are synthesized by the emulsion and inverse emulsion methods using conventional ammonium persulfate and a new oxidant, benzoyl peroxide, respectively. The influence of the polymerization conditions such as the monomer feed ratios, solvent, and the nonsolvent is investigated. The composition of the resulting copolymers is determined by 1H NMR analysis. The conductivity of the copolymers varies with the aminoacetophenone content in the feed and the polymerization conditions. It is interesting that the conductivity of the copolymers is higher than that of the corresponding homopolymers. The results are rationalized on the basis of the effect of the COCH3 substituent on the polymer structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4300,4310, 2004 [source] Synthesis and characterization of epoxidized polybutadiene/polyaniline graft conducting copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2004F. R. De Risi Abstract In this article the synthesis and characterization of an elastomeric conducting material, obtained by grafting polyaniline (EB) on commercial cis -1,4-polybutadiene (PB), are described. PB was first partially epoxidized in chloroform solution using meta-chloroperbenzoic acid (MCPBA). The conducting polymer was then grafted to the activated polybutadiene (EPB) via the aminolysis reaction between the polyaniline NH2 terminal groups and the oxirane rings. The material so obtained (EPBPAN) and the epoxidized intermediate product were characterized by 1H NMR, 13C NMR, Fourier transform infrared, and ultraviolet,visible spectroscopy, thermal and mechanical analysis, and electrical conductivity measurements. The effect of the sample deformation on conductivity also was analyzed. The HCl doping of the EPBPAN film induced crosslinking reactions, generated by the acid cleavage of unreacted oxirane groups. The electrical conductivity of the doped material reached values of about 10,5 ,,1 cm,1. The key characteristics of our elastomeric conducting material are its simple synthesis, its starting as a commercial product, and the solubility of its undoped form in a common low-boiling organic solvent like chloroform. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3082,3090, 2004 [source] Solid-Solution Formation in the Synthesis of Fe-ZirconJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2004Enrique Carreto Cortés To investigate solid-solution formation in the iron-doped silicate (zircon) system, different samples were prepared by the ceramic method with addition of LiF as a mineralizer. The results of X-ray powder diffraction (XRD), 57Fe Mössbauer, and UV,visible spectroscopy showed that in the as-prepared samples, only a small fraction of iron, i.e., about 2.5 mol%, is hosted in the zircon structure as paramagnetic Fe3+ species, while the remaining Fe3+ cations form magnetic ,-Fe2O3 particles that are trapped in the zircon matrix. [source] Low-temperature Spectroscopy of Met100Ala Mutant of Photoactive Yellow Protein,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Yasushi Imamoto The trans -to- cis photoisomerization of the p -coumaroyl chromophore of photoactive yellow protein (PYP) triggers the photocycle. Met100, which is located in the vicinity of the chromophore, is a key residue for the cis -to- trans back-isomerization of the chromophore, which is a rate-determining reaction of the PYP photocycle. Here we characterized the photocycle of the Met100Ala mutant of PYP (M100A) by low temperature UV,visible spectroscopy. Irradiation of M100A at 80 K yielded a 380 nm species (M100ABL), while the corresponding intermediate of wild type (WT; PYPBL) is formed above 90 K. The amounts of redshifted intermediates produced from M100A (M100AB, and M100AL) were substantially less than those from WT. While the near-UV intermediate (PYPM) is not formed from WT in glycerol samples at low temperature, M100AM was clearly observed above 190 K. These alterations of the photocycle of M100A were explained by the shift in the equilibrium between the intermediates. The carbonyl oxygen of the thioester linkage of the cis -chromophore in the photocycle intermediates is close to the phenyl ring of Phe96 (<3.5 Å), which would be displaced by the mutation of Met100. These findings imply that the interaction between chromophore and amino acid residues near Met100 is altered during the early stage of the PYP photocycle. [source] Nonlinear optical properties of poly-ortho-toluidine films implantated by N+ ions with different energyPOLYMER COMPOSITES, Issue 10 2009Yan Shaolin This article reports experimental work on the effect of N+ ion implantation on third-order nonlinear optical properties of POT films. Using K2Cr2O7 as oxidizing agent, poly- ortho -toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin-coating method and then implantated by N+ ions (15,30 KeV) at a dose 1.9 × 1016 ions/cm2. The films were characterized by FT-IR spectroscopy, visible spectroscopy and SEM, their third-order nonlinear optical susceptibility (,(3)) were also examined by a degenerate four-wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The ,(3) value of implantated POT films increased from 3.31 × 10,10 esu to 4.04 × 10,9 esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] A convenient synthesis of nanocrystalline chalcopyrite, CuFeS2 using single-source precursorsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2009Sujit D. Disale Abstract Nanocrystalline chalcopyrite (CuFeS2) have been synthesized using single-source precursors, CuL2 and Cu(LH)2Cl2 (where LH = monoacetylferrocene thiosemicarbazone) by pyrolysis and solvothermal decomposition methods. The nanocrystals were characterized by UV,visible spectroscopy, X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray analysis. The magnetic character was determined by the hysteresis loop. CuFeS2 nanocrystallites prepared by the pyrolysis of CuL2 and Cu(LH)2Cl2 have a cubic phase and rod-like morphology with diameters of about 18 and 15 nm, respectively, and lengths of about 195,390 and 100,145 nm, respectively. However, CuFeS2 nanoparticles obtained by solvothermal route from CuL2 and Cu(LH)2Cl2, which are capped with ethylene glycol, possess a nearly spherical shape with an average grain size of 16 and 11 nm, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] UV,visible spectroscopy for zirconocene activation by MAO in olefin polymerization: activity versus wavenumberAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2009Carlos Alonso-Moreno Abstract Activation of ansa -zirconocenes of the type Rac [Zr{1-Me2Si(3-R-(,5 -C9H5))(3-R,-(,5 -C9H5))}Cl2] [R = Et, R, = H (1); R = Pr, R, = H (2); and R = Et, R, = Pr (3), R, R, = Me (4) and R, R, = Bu (5)] by MAO has been studied by UV,visible spectroscopy. Compounds 1,3 have been tested in the polymerization of ethylene at different Al:Zr ratios. UV,vis spectroscopy was used to determine a correlation between the electronic structures of (1,5) and their polymerization activity. Copyright © 2009 John Wiley & Sons, Ltd. [source] Shuttling Gold Nanoparticles into Tumoral Cells with an Amphipathic Proline-Rich PeptideCHEMBIOCHEM, Issue 6 2009Sílvia Pujals Abstract Golden bullets: The amphipathic proline-rich cell-penetrating peptide sweet arrow peptide (SAP) is able to transport 12 nm gold nanoparticles efficiently into HeLa cells, as observed by three microscopy techniques: transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM) and transmission X-ray microscopy (TXM). Multiconjugation to such nanoparticles may provide a convenient method for unifying the key drug properties of high activity, capacity to home onto targets and delivery to therapeutic places of action. Cell-penetrating peptides (CPPs) are a potential tool for intracellular delivery of different kinds of cargoes. Because of their growing use in nanobiomedicine, both for diagnostics and for treatment, metal nanoparticles are an interesting cargo for CPPs. Here, gold nanoparticles (AuNps) and the amphipathic proline-rich peptide SAP have been used. Conjugation of the peptide onto the AuNps was achieved by addition of a cysteine to the SAP sequence for thiol chemisorption on gold, and the attachment was confirmed by visible spectroscopy, dynamic light scattering (DLS), ,-potential (ZP), stability towards ionic strength (as high as 1,M NaCl), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM) coupled to electron energy loss spectroscopy (EELS). AuNp-C-SAP internalization in HeLa cells was observed by three different microscopy techniques,TEM, confocal laser scanning microscopy (CLSM) and transmission X-ray microscopy (TXM),and all of them have confirmed the effective intracellular delivery of AuNps by SAP. [source] | |||||||||||||||||||