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排序方式: 共有572条查询结果,搜索用时 31 毫秒
1.
Brandon Howe 《Journal of luminescence》2004,109(1):51-59
Host-lattice emission, energy transfer and degradation processes are characterized in undoped and Eu-doped BaMgAl10O17. Undoped BaMgAl10O17 exhibits a broad emission centered at 265 nm when excited at wavelengths shorter than 190 nm. This emission is assigned to exciton recombination at Ba-O groups in the cation layer of the lattice. The emission exhibits excellent overlap with the excitation band of Eu2+ in this host, providing a means of host-to-activator energy transfer in the doped phosphor. The exciton emission is relatively stable to thermal damage, but undergoes a peak shift and significant decrease in intensity after exposure to VUV radiation. Heating of VUV-damaged materials in air leads to some repair of the spectral properties. 相似文献
2.
A. W. Flounders D. L. Brandon A. H. Bates 《Applied biochemistry and biotechnology》1995,50(3):265-284
Monoclonal antibodies specific for thiabendazole were immobilized to silicon, silicon dioxide, stoichiometric silicon nitride,
and silicon-rich silicon nitride surfaces. This work provides the foundation for the development of a homogeneous sensor system
for rapid detection and quantification of thiabendazole residues in produce and animal tissue. Immobilization was performed
via aqueous silanization of the substrate followed sequentially by treatment with glutaraldehyde and contact with antibody
solution in the presence of detergent. Surfaces were challenged with thiabendazole-horseradish peroxidase conjugate in an
ELISA format to estimate immobilized antibody load. A stable and reproducible surface loading of 2 x 1011 antibodies/cm2 was obtained only after surfaces received postimmobilization treatments to remove nonspecifically adsorbed antibody. No difference
in surface loading was noted when using 30% hydrogen peroxide rather than nitric acid for silanol activation. Little difference
was noted among the antibody loadings achieved on the various silicon substrates. Bound antigen-enzyme conjugate was eluted
with 0.1N acetic acid and reproducible surface activity was measured for up to four consecutive antigen challenges. Immobilized
antibody surfaces were stabilized with 2% sucrose, dehydrated at 37‡C and stored in vacuum or stored at 4‡C in phosphate buffered
saline containing 0.01% sodium azide without significant loss of activity. 相似文献
3.
Applications of chalcogenide glass optical fibers 总被引:2,自引:0,他引:2
Chalcogenide-glass fibers based on sulfide, selenide, telluride and their rare-earth-doped compositions are being actively pursued worldwide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, chalcogenide-glass fibers are enabling numerous applications that include laser power delivery, chemical sensing, and imaging, scanning near field microscopy/spectroscopy, IR sources/lasers, amplifiers and optical switches. 相似文献
4.
Brandon D. ConleyBurl C. Yearwood Sean ParkinDavid A. Atwood 《Journal of fluorine chemistry》2002,115(2):155-160
The preparation and characterization of the ammonium hexafluorosilicate salts, 2[R]+ [SiF6]2− (where R=piperidinium (2), methylammonium (3), quinolinium (4), acridinium (5), 2,2,6,6-tetramethylpiperidinium (6), and propylammonium (7)) is described.The salts were prepared from the reaction of the corresponding alkylammonium fluoride with silica gel. The compounds were characterized by NMR, IR, mass spectrometry and in the case of 1 (piperidinium fluoride), 2-4 by X-ray crystallography. Compounds 1-3 crystallize in the orthorhombic crystal system (space groups Iba2, Fdd2, and Pnnm, respectively), with Z=8, 14, and 4, respectively. Compound 4 crystallizes in the triclinic space group P-1, with Z=2. Compounds 1-4 exhibit hydrogen bonding. 相似文献
5.
Gregory M. Su Han Wang Brandon R. Barnett Jeffrey R. Long David Prendergast Walter S. Drisdell 《Chemical science》2021,12(6):2156
Metal–organic frameworks are promising materials for applications such as gas capture, separation, and storage, due to their ability to selectively adsorb small molecules. The metal–organic framework CuI-MFU-4l, which contains coordinatively unsaturated copper(i) centers, can engage in backbonding interactions with various small molecule guests, motivating the design of frameworks that engage in backbonding and other electronic interactions for highly efficient and selective adsorption. Here, we examine several gases expected to bind to the open copper(i) sites in CuI-MFU-4l via different electronic interactions, including σ-donation, π-backbonding, and formal electron transfer. We show that in situ Cu L-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy can elucidate π-backbonding by directly probing excitations to unoccupied backbonding orbitals with Cu d-character, even for gases that participate in other dominant interactions, such as ligand-to-metal σ-donation. First-principles calculations based on density functional theory and time-dependent density functional theory additionally reveal the backbonding molecular orbitals associated with these spectroscopic transitions. The energies of the transitions correlate with the energy levels of the isolated small molecule adsorbates, and the transition intensities are proportional to the binding energies of the guest molecules within CuI-MFU-4l. By elucidating the molecular and electronic structure origins of backbonding interactions between electron rich metal centers in metal–organic frameworks and small molecule guests, it is possible to develop guidelines for further molecular-level design of solid-state adsorbents for energy-efficient separations of relevance to industry. In situ near edge X-ray absorption fine structure spectroscopy directly probes unoccupied states associated with backbonding interactions between the open metal site in a metal–organic framework and various small molecule guests. 相似文献
6.
The adsorption, desorption, and clustering behavior of H2O on Pt111 has been investigated by specular He scattering. The data show that water adsorbed on a clean Pt111 surface undergoes a structural transition from a random distribution to clustered islands near 60 K. The initial helium scattering cross sections as a function of temperature are found to be insensitive to the incident H2O flux over a range of 0.005 monolayers (ML)/s-0.55 ML/s indicating that the clustering process is more complex than simple surface diffusion. The coarsening process of an initially random distribution of water deposited at 25 K is found to occur over a broad temperature range, 60相似文献
7.
[Rh(CO)(2)Cl](2) has been found to possess the unusual property of catalyzing allylic alkylations of unsymmetrical allylic carbonates with high levels of regioselectivity to provide products arising from substitution at the carbon atom bearing the leaving group, irrespective of the structure of the starting carbonate. The substitution reaction occurs with retention of stereochemistry at the reacting center, and the carbon-carbon double-bond stereochemistry of primary (Z)-allylic carbonates is maintained. [reaction: see text] 相似文献
8.
John A. McLean Brandon T. Ruotolo Kent J. Gillig David H. Russell 《International journal of mass spectrometry》2005,240(3):301
Matrix-assisted laser desorption/ionization (MALDI) coupled with ion mobility–mass spectrometry (IM–MS) provides a rapid (μs–ms) means for the two-dimensional (2D) separation of complex biological samples (e.g., peptides, oligonucleotides, glycoconjugates, lipids, etc.), elucidation of solvent-free secondary structural elements (e.g., helices, β-hairpins, random coils, etc.), rapid identification of post-translational modifications (e.g., phosphorylation, glycosylation, etc.) or ligation of small molecules, and simultaneous and comprehensive sequencing information of biopolymers. In IM–MS, protein-identification information is complemented by structural characterization data, which is difficult to obtain using conventional proteomic techniques. New avenues for enhancing the figures of merit (e.g., sensitivity, limits of detection, dynamic range, and analyte selectivity) and optimizing IM–MS experimental parameters are described in the context of deriving new information at the forefront of proteomics research. 相似文献
9.
2-(2-Pyridyl)benzo[b]selenophene has been investigated as a possible reagent for palladium. From a consideration of its reactions with diverse metal ions, and the probable structure of the complex formed between the compound and palladium(II) it is postulated that the group may be highly selective for palladium. From the experimental evidence it is suggested that the delocalization of the metal electron density by pi-bond formation between the palladium and selenium atoms is a major factor in determining the stability of the chelated complex. 相似文献
10.
Capillary sodium dodecyl sulfate (SDS)-DALT electrophoresis (SDS-DALT-CE) refers to CE separation of proteins based on their size; DALT is the abbreviation for Dalton, the unit used to describe molecular weight. In this work, seven proteins from 18 to 116 kDa were denatured by SDS, labeled by 3-(2-furoyl) quinoline-2-carboxaldehyde, separated by SDS-DALT-CE in polyethylene oxide sieving matrix, and detected by laser-induced fluorescence (LIF) in a sheath flow cuvette. This method was combined with detergent differential fractionation, which is a protein fractionation method using a series of detergent-containing buffers to sequentially extract protein fractions from cells, to analyze the proteins in HT29 human colon adenocarcinoma cells. In addition, on-column labeling was demonstrated for protein analysis by SDS-DALT-CE with LIF, and applied to analysis of proteins in a single HT29 cancer cell. Most proteins had molecular masses from 10 to 120 kDa. Similar protein profiles were obtained for single cells and protein extract of a large cell population. 相似文献