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141.
Partha Sarathi Roy Joyeeta Bagchi Swapan Kumar Bhattacharya 《Transition Metal Chemistry》2009,34(4):447-453
In order to synthesize stable, catalytically active palladium nanoparticles with low polydispersity, a one-pot synthesis by
the facile reduction of palladium chloride with citric acid in an aqueous solution of steric stabilizer polyvinyl alcohol
(PVA) has been developed. The resulting nanoparticles are highly water-dispersible, excellent electro-catalysts, and have
long shelf life. The palladium nanoparticles have been characterized by physico-chemical, spectroscopic, microscopic, and
CV studies. The average size of the nanoparticles can be readily tuned from 8.1 to 53 nm by controlling the extent of reflux
for mixtures containing suitable concentrations of metal ion, reducing agent and capping polymer, which also influence the
size. Despite the surface-protecting action of PVA, the palladium nanoparticles are electro-catalytically active and exhibit
size-dependent electro-catalytic behavior. 相似文献
142.
Nandini Nag 《Annals of Physics》2009,324(3):499-522
The effect of strong quantizing magnetic field on the equation of state of matter at the outer crust region of magnetars is studied. The density of such matter is low enough compared to the matter density at the inner crust or outer core region. Based on the relativistic version of semi-classical Thomas-Fermi-Dirac model in presence of strong quantizing magnetic field a formalism is developed to investigate this specific problem. The equation of state of such low density crustal matter is obtained by replacing the compressed atoms/ions by Wigner-Seitz cells with nonuniform electron density. The results are compared with other possible scenarios. The appearance of Thomas-Fermi induced electric charge within each Wigner-Seitz cell is also discussed. 相似文献
143.
Jaydeep Paul Apratim Nag Himadri Sekhar Das 《Chinese Journal of Physics (Taipei)》2018,56(3):1121-1125
In this study, we have tried to investigate the generation of sheath in magnetized plasma rotating with a uniform angular velocity about an axis making an angle with the direction of plasma-acoustic wave propagation. In a marked contrast to the earlier studies, here the simultaneous impact of slow rotation and external magnetic field has been taken into consideration. Previous studies have revealed that the Coriolis force generated from rotation has a tendency to produce an equivalent magnetic field effect as and when the ionized medium rotates. The variations of sheath potential with normalized distance for different values of angles of rotation as well as for different values of Mach number have also been investigated for typical plasma parameters. 相似文献
144.
Habibul Arfin Jagjit Kaur Tariq Sheikh Sudip Chakraborty Angshuman Nag 《Angewandte Chemie (International ed. in English)》2020,59(28):11307-11311
Bi3+ and lanthanide ions have been codoped in metal oxides as optical sensitizers and emitters. But such codoping is not known in typical semiconductors such as Si, GaAs, and CdSe. Metal halide perovskite with coordination number 6 provides an opportunity to codope Bi3+ and lanthanide ions. Codoping of Bi3+ and Ln3+ (Ln=Er and Yb) in Cs2AgInCl6 double perovskite is presented. Bi3+‐Er3+ codoped Cs2AgInCl6 shows Er3+ f‐electron emission at 1540 nm (suitable for low‐loss optical communication). Bi3+ codoping decreases the excitation (absorption) energy, such that the samples can be excited with ca. 370 nm light. At that excitation, Bi3+‐Er3+ codoped Cs2AgInCl6 shows ca. 45 times higher emission intensity compared to the Er3+ doped Cs2AgInCl6. Similar results are also observed in Bi3+‐Yb3+ codoped sample emitting at 994 nm. A combination of temperature‐dependent (5.7 K to 423 K) photoluminescence and calculations is used to understand the optical sensitization and emission processes. 相似文献
145.
Nag K Fritzen-Garcia M Devraj R Panda AK 《Langmuir : the ACS journal of surfaces and colloids》2007,23(8):4421-4431
Pulmonary surfactants stabilize the lung by way of reducing surface tension at the air-lung interface of the alveolus. 31P NMR, thin-layer chromatography, and electrospray ionization mass spectroscopy of bovine lipid extract surfactant (BLES) confirmed dipalmitoylphosphatidylcholine (DPPC) to be the major phospholipid species, with significant amounts of palmitoyl-oleoylphosphatidylcholine, palmitoyl-myristoylphosphatidylcholine, and palmitoyl-oleoylphosphatidylglycerol. BLES and DPPC spread at the air-water interface were studied through surface pressure area, fluorescence, and Brewster angle microscopy measurements. Langmuir-Blodgett films of monomolecular films, deposited on mica, were characterized by atomic force microscopy. BLES films displayed shape, size, and vertical height profiles distinct from those of DPPC alone. Calcium ions in the subphase altered BLES film domain structure. The addition of cholesterol (4 mol %) resulted in the destabilization of compressed BLES films at higher surface pressures (>40 mN m-1) and the formation of multilayered structures, apparently consisting of stacked monolayers. The studies suggested potential roles for individual surfactant lipid components in supramolecular arrangements, which could be the contributing factors in pulmonary surfactant to attain low surface tension at the air-water interface. 相似文献
146.
Dramatic influence of the orientation of linker between hydrophilic and hydrophobic lipid moiety in liposomal gene delivery 总被引:1,自引:0,他引:1
Rajesh M Sen J Srujan M Mukherjee K Sreedhar B Chaudhuri A 《Journal of the American Chemical Society》2007,129(37):11408-11420
A number of prior studies have demonstrated that the DNA-binding and gene transfection efficacies of cationic amphiphiles crucially depend on their various structural parameters including hydrophobic chain lengths, headgroup functionalities, and the nature of the linker-functionality used in tethering the polar headgroup and hydrophobic tails. However, to date addressing the issue of linker orientation remains unexplored in liposomal gene delivery. Toward probing the influence of linker orientation in cationic lipid mediated gene delivery, we have designed and synthesized two structurally isomeric remarkably similar cationic amphiphiles 1 and 2 bearing the same hydrophobic tails and the same polar headgroups connected by the same ester linker group. The only structural difference between the cationic amphiphiles 1 and 2 is the orientation of their linker ester functionality. While lipid 1 showed high gene transfer efficacies in multiple cultured animal cells, lipid 2 was essentially transfection incompetent. Findings in both transmission electron microscopic and dynamic laser light scattering studies revealed no significant size difference between the lipoplexes of lipids 1 and 2. Findings in confocal microscopic and fluorescence resonance energy transfer (FRET) experiments, taken together, support the notion that the remarkably higher gene transfer efficacies of lipid 1 compared to those of lipid 2 presumably originate from higher biomembrane fusogenicity of lipid 1 liposomes. Differential scanning calorimetry (DSC) and fluorescence anisotropy studies revealed a significantly higher gel-to-liquid crystalline temperature for the lipid 2 liposomes than that for lipid 1 liposomes. Findings in the dye entrapment experiment were also consistent with the higher rigidity of lipid 2/cholesterol (1:1 mole ratio) liposomes. Thus, the higher biomembrane fusibility of lipid 1 liposomes than that of lipid 2 liposomes presumably originates from the more rigid nature of lipid 2 cationic liposomes. Taken together, the present findings demonstrate for the first time that even as minor a structural variation as linker orientation reversal in cationic amphiphiles can profoundly influence DNA-binding characteristics, membrane rigidity, membrane fusibility, cellular uptake, and consequently gene delivery efficacies of cationic liposomes. 相似文献
147.
Rath H Sankar J Prabhuraja V Chandrashekar TK Nag A Goswami D 《Journal of the American Chemical Society》2005,127(33):11608-11609
The third-order nonlinear optical response through measurement of two-photon absorption cross-sections (TPACS) for aromatic core-modified expanded porphyrin analogues by a femtosecond open aperture Z-scan method is reported. The values reported here are among the largest known so far in the literature for any organic molecules. 相似文献
148.
Kalyan Raidongia Angshuman Nag Dr. K. P. S. S. Hembram Dr. Umesh V. Waghmare Prof. Dr. Ranjan Datta Dr. C. N. R. Rao Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):149-157
A new analogue of graphene containing boron, carbon and nitrogen (BCN) has been obtained by the reaction of high‐surface‐area activated charcoal with a mixture of boric acid and urea at 900 °C. X‐ray photoelectron spectroscopy and electron energy‐loss spectroscopy reveal the composition to be close to BCN. The X‐ray diffraction pattern, high‐resolution electron microscopy images and Raman spectrum indicate the presence of graphite‐type layers with low sheet‐to‐sheet registry. Atomic force microscopy reveals the sample to consist of two to three layers of BCN, as in a few‐layer graphene. BCN exhibits more electrical resistivity than graphene, but weaker magnetic features. BCN exhibits a surface area of 2911 m2 g?1, which is the highest value known for a BxCyNz composition. It exhibits high propensity for adsorbing CO2 (≈100 wt %) at 195 K and a hydrogen uptake of 2.6 wt % at 77 K. A first‐principles pseudopotential‐based DFT study shows the stable structure to consist of BN3 and NB3 motifs. The calculations also suggest the strongest CO2 adsorption to occur with a binding energy of 3.7 kJ mol?1 compared with 2.0 kJ mol?1 on graphene. 相似文献
149.
150.
Summary We study the electronic contribution to the second- and third-order elastic constants in strained quantum wire superlattices
of non-parabolic semiconductors with graded structures and compare the same with the constituent materials, by formulating
the appropriate dispersion laws. It is found, taking InSb/GaSb quantum wire superlattice as an example, that the said contributions
increase with decreasing thickness and with increasing electron concentration in oscillatory manners together with the fact
that the influence of the finite interface width enhances their numerical values. An experimental method is suggested for
determining the electronic contribution to the elastic constants in materials having arbitrary dispersion laws. In addition,
the well-known results for constituent semiconductors in the absence of stress have also been obtained as special cases of
our generalized formulations. 相似文献