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101.
Au/SnO2 core-shell structure nanoparticles were synthesized using the microwave hydrothermal method. The optical and morphological properties of these particles were examined and compared with those obtained by the conventional hydrothermal method. In microwave preparation, the peak position of the UV-visible plasmon absorption band of Au nanoparticles was red-shifted from 520 to 543 nm, due to the formation of an SnO2 shell. An SnO2 shell formation was complete within 5 min. The thickness of the SnO2 shell was 10-12 nm, and the primary particle size of SnO2 crystallites was 3-5 nm. For the core-shell particles prepared by a conventional hydrothermal method, the shell formed over the entire synthesis period and was not as crystalline as those produced, using the microwave method. The relationship between the morphological and spectroscopic properties and the crystallinity of the SnO2 shell are discussed. 相似文献
102.
Mahato M Pal P Tah B Ghosh M Talapatra GB 《Colloids and surfaces. B, Biointerfaces》2011,88(1):141-149
Nanoscience is now an expanding field of research and finds potential application in biomedical area, but it is limited due to lack of comprehensive knowledge of the interactions operating in nano-bio system. Here, we report the studies on the interaction and formation of nano-bio complex between silver nanoparticle (AgNP) and human blood protein hemoglobin (Hb). We have employed several spectroscopic (absorption, emission, Raman, FTIR, CD, etc.) and electron diffraction techniques (FE-SEM and HR-TEM) to characterize the Hb-AgNP complex system. Our results show the Hb-AgNP interaction is concentration and time dependent. The AgNP particle can attach/come closer to heme, tryptophan, and amide as well aromatic amine residues. As a result, the Hb undergoes conformational change and becomes unfolded through the increment of β-sheet structure. The AgNP-Hb can form charge-transfers (CT) complex where the Hb-heme along with the AgNP involved in the electron transfer mechanism and form Hb-AgNP assembled structure. The electron transfer mechanism has been found to be dependent on the size of silver particle. The overall study is important in understanding the nano-bio system and in predicting the avenues to design and synthesis of novel nano-biocomposite materials in material science and biomedical area. 相似文献
103.
Prabir Nandi Ajaya Bhattarai Bijan Das 《Journal of Polymer Science.Polymer Physics》2007,45(14):1765-1770
Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and in two acetonitrile–water mixtures containing 10 and 20 vol % of acetonitrile have been reported at 35, 40 and 50 °C. Isoionic dilutions were performed with the total ionic strengths of the solutions maintained with sodium chloride at ~4.20 × 10?4 and 1.45 × 10?3 mol dm?3 of NaCl to obtain the intrinsic viscosities. The Huggins constants were also obtained from the experimental results. The influences of the medium, the temperature, and the total ionic strength on the intrinsic viscosities as well as on the Huggins constants have been interpreted from the points of view of the solvodynamic and thermodynamic interactions prevailing in the polyelectrolyte solution under investigation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1765–1770, 2007 相似文献
104.
Prabir K. Mukherjee 《Liquid crystals》2013,40(6):863-869
We propose a Landau-de Gennes phenomenological model to describe the nematic-isotropic phase transition in lyotropic liquid crystals. The possibility of a first or second order transition is explored by means of the variation of the concentration of surfactant. We show that a Landau point on the nematic-isotropic phase transition line can be achieved under certain conditions. The theoretical predictions are found to be in good qualitative agreement with available experimental results. 相似文献
105.
Luc Villeneuve Prabir Pal Gilles Durocher David Migneault Denis Girard Richard Giasson Antonia Balassy Louise Blanchard Louis Gaboury 《Journal of fluorescence》1996,6(4):209-219
Steady-state and time-resolved spectroscopic properties of rhodamine-123 (rh123) and 4,5-dibromorhodamine methyl ester (dbr123) bound to different cell lines are evaluated. Studies are also performed on the dye bound to extracted mitochondria. Results are compared with those obtained in homogeneous and microheterogeneous media. Results suggest that these dyes can specifically bind only with cell mitochondria. As a result of binding, excitation and emission spectra are red shifted by 10 to 12 nm. The fluorescence decay of these dyes bound to mitochondria shows two lifetimes. Values are about 4.0 and 2.0 ns forrh123 and about 1.9 and 0.5 ns fordbr123. Detailed global analysis of emission wavelength and dye concentration dependences of the fluorescence decay is performed. Results indicate that these dyes are bound to two different binding sites at mitochondria. The decay-associated fluorescence spectrum for the species corresponding to each binding site is recovered. Species1, corresponding to the longer lifetime, is found to be more red shifted compared to species2. The fluorescence of species2 is heavily quenched. The origin of this quenching is explained in terms of resonance energy transfer between donor species2 and acceptor species1. The possible nature of the two binding sites is also discussed. 相似文献
106.
107.
Bargellini condensation of coumarins. Expeditious synthesis of o-carboxyvinylphenoxyisobutyric acids
Condensation of coumarins with chloroform and acetone in the presence of a base furnished o-carboxyvinylphenoxyisobutyric acids in good yields. The diacid 7a was transformed in a few high yielding steps to the marine sesquiterpene helianane underscoring the importance of this new protocol. 相似文献
108.
[reaction: see text] The reaction of ketone enolates with phosphonate aldehyde 2 afforded cyclopentenols 3 or keto esters 4 in a one-pot procedure. 相似文献
109.
110.