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1.
Yu Li Bijaya Thapa Hua Zhang Xuefei Li Fanghua Yu Eun-Kee Jeong Zhigang Yang Zhong-Xing Jiang 《Tetrahedron》2013
A family of fluorinated gemini surfactants derived from perfluoropinacol has been synthesized as novel 19F magnetic resonance imaging (19F MRI) agents. These fluorinated surfactants with 12 symmetric fluorine atoms and one singlet 19F MR peak can be conveniently prepared from perfluoropinacol and oligo(ethylene glycols) on multi-gram scales. Solubility, hydrophilicity (log P), and critical micelle concentration (CMC) measurements of these fluorinated surfactants indicated that high aqueous solubility can be achieved by introducing oligo(ethylene glycols) with appropriate length into perfluoropinacol, i.e., manipulating the fluorine content (F%). One of these fluorinated surfactants with high aqueous solubility and excellent 19F MR properties has been identified by 19F MRI phantom experiments as a promising 19F MRI agent. 相似文献
2.
Rules of Boron–Nitrogen Doping in Defect Graphene Sheets: A First‐Principles Investigation of Band‐Gap Tuning and Oxygen Reduction Reaction Catalysis Capabilities
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Introduction of defects and nitrogen doping are two of the most pursued methods to tailor the properties of graphene for better suitability to applications such as catalysis and energy conversion. Doping nitrogen atoms at defect sites of graphene and codoping them along with boron atoms can further increase the efficiency of such systems due to better stability of nitrogen at defect sites and stabilization provided by B?N bonding. Systematic exploration of the possible doping/codoping configurations reflecting defect regions of graphene presents a prevalent doping site for nitrogen‐rich BN clusters and they are also highly suitable for modulating (0.2–0.9 eV) the band gap of defect graphene. Such codoped systems perform significantly better than the platinum surface, undoped defect graphene, and the single nitrogen or boron atom doped defect graphene system for dioxygen adsorption. Significant stretching of the O?O bond indicates a lowering of the bond breakage barrier, which is advantageous for applications in the oxygen reduction reaction. 相似文献
3.
Transparent and highly conducting thin films of cadmium oxide (CdO) with titanium doping were synthesized by using radio frequency magnetron sputtering technique. The thin films were deposited on glass and silicon substrates with different percentages of titanium at a fixed substrate temperature 473 K and a fixed pressure of 0.1 mbar in Ar atmosphere. The deposited films were characterized by studying their crystallographic structure, optical and electrical properties. X-ray diffractometer, atomic force microscope, UV–Vis–NIR spectrophotometer, and X-ray photoelectron spectrophotometer were used for different characterizations. All the films have a rock-salt structure. A systematic increase in the optical bandgap was found for the CdO thin films with Ti doping, so that it can be considered as a candidate material for different optoelectronic device applications. Electrical conductivity was also found to increase with Ti doping concentration. 相似文献
4.
Thin films of p-type transparent conducting CuAlO2 have been synthesized through reactive radio frequency magnetron sputtering on silicon and glass substrates at substrate
temperature 300°C. Reactive sputtering of a target fabricated from Cu and Al powder (1:1.5) was performed in Ar+O2 atmosphere. The deposition parameters were optimized to obtain phase pure, good quality CuAlO2 thin films. The films were characterized by studying their structural, morphological, optical and electrical properties. 相似文献
5.
Calbindin D9k is a member of the S100 subfamily of EF-hand calcium binding proteins, and has served as an important model system for biophysical studies. The fast timescale dynamics of the calcium-free (apo) state is characterized using molecular dynamics simulations. Order parameters for the backbone NH bond vectors are determined from the simulations and compared with experimentally derived values, with a focus on the dynamics of calcium-binding site I. There is a significant discrepancy between simulated and experimental order parameters for site I residues in the case of no ion bound in site I. However, it was found in the simulations that a Na+ ion can bind in site I, and the resulting order parameters determined from the simulations are in excellent agreement with experiment. Comparisons are made to X-ray structures of other S100 family members in which Na+ ions were observed or suggested to be bound in site I. © 2019 Wiley Periodicals, Inc. 相似文献
6.
G.M. Prinz A. Ladenburger M. Feneberg M. Schirra S.B. Thapa M. Bickermann B.M. Epelbaum F. Scholz K. Thonke R. Sauer 《Superlattices and Microstructures》2006,40(4-6):513
Strained AlN layers grown by MOVPE on sapphire and nominally unstrained AlN single crystals were studied employing photoluminescence, cathodoluminescence, and reflectance spectroscopy in the near-band edge range. The data allow one to determine fundamental optical parameters such as the band edge energy with its crystal field splitting and strain dependence which are still under discussion. Reflection measurements performed on crystal facets with different orientations and subjected to varying selection rules serve to assign the observed transitions to valence band states with specific symmetries.Near-band edge excitonic luminescence at around 6 eV was recorded as a function of temperature (). Fits to the data using standard models from the literature yield the temperature dependence Eg(T) of the band gap. 相似文献
7.
Karki Surya B. Gupta Tripti Thapa Yildirim-Ayan Eda Eisenmann Kathryn M. Ayan Halim 《Plasma Chemistry and Plasma Processing》2020,40(1):99-117
Plasma Chemistry and Plasma Processing - Non-thermal plasma has been a promising new cancer treatment modality in plasma oncology field. It generates extracellular and intracellular reactive... 相似文献
8.
Krishan K. Narang Ram A. Lal Ram K. Thapa Vijai K. Gautam 《Transition Metal Chemistry》1988,13(3):212-216
Summary Some copper(II) complexes of the type Cu(HL)X·nH2O (where H2L = benzoin thiosemicarbazone; X=NO3; Cl, Br, SCN, ClO4 or 1/2SO4; n=O–2) have been prepared and characterized. All complexes have tetragonally distorted octahedral stereochemistry except the sulphatocomplex which is square pyramidal. The i.r. spectra reveal that HL acts as a monobasic tridentate ligand coordinating through the azine group nitrogen atom, thiocarbonyl sulphur atom and hydroxylic oxygen atom while NO3, Cl, Br and ClO4 act as terminal monodentate ligands and SCN and SO4 act as bidentate bridging ligands. The polycrystalline e.s.r. spectra suggest tetragonal symmetry for the copper(II) ion, involving a dx
2–y2 ground state. 相似文献
9.
B. Indrajit Sharma Jameson Maibam R. S. Paul R. K. Thapa R. K. Brojen Singh 《Indian Journal of Physics》2010,84(6):671-674
Energy band structure of NbC and NbN are calculated using generalized gradient approximation (GGA) within density functional
theory (DFT) including five high symmetry points W, L, Γ, X and K. The lowest band corresponds to 2s band of non metal (C and N) atoms and the next lowest band is formed by 2p nonmetal. The decomposing points of t
2g
states (Γ
25), e
g
states (Γ
12) and C or N 2p states (Γ
15) show interesting behavior different from earlier reports. 相似文献
10.
Nanocrystalline AlN thin films were prepared via DC sputtering technique at different substrate temperature. The crystal orientation
and particle size of aluminum nitride thin films were investigated by XRD analysis. Study indicated that the sample contained
pure phase hexagonal AlN nanoparticles with a single peak corresponding to the (100) planes. The peak at 665 cm−1 in the FTIR spectrum of film was assigned to the LO phonon of hexagonal AlN. The particle size of the film, prepared at substrate
temperature 200°C was about 9.5 nm, as investigated by atomic force microscope. Field emission study indicated that it can
be used as a good field emitter. Turn-on field (Eto) of 15.02 V/μm was observed for the AlN films synthesized at substrate temperature 200°C. Dielectric constant of the AlN
film was found nearly independent of frequencies in the measured frequency range 1 KHz to 1 MHz, i.e. in the audio frequency range. The values of dielectric constant (ε) were 10.07, 9.46 and 8.65 for the film prepared at 70°C, 150°C and 200°C, respectively, at frequency 1 KHz. 相似文献