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Jewett S Zemlyanov D Ivanisevic A 《Langmuir : the ACS journal of surfaces and colloids》2011,27(7):3774-3782
The well-defined structure and high stability of peptides make them attractive biotemplates for low-temperature synthesis of semiconductor nanocrystals. Adsorbed peptide monolayers could also potentially passivate semiconductors by preventing regrowth of the oxide layer. In this work, the adsorption and passivation capabilities of different collagen-binding peptides on InAs surfaces were analyzed by X-ray photoelectron spectroscopy (XPS). Before peptide functionalization, Br(2)- and HCl-based etches were used to remove the native oxide layer on the InAs surfaces. The presence of the N 1s peak for peptide-functionalized samples confirms the adsorption of peptides onto the etched InAs surfaces. Calculated coverages were similar for all peptide sequences and ranged from ~20 to 40% of a monolayer using the deconvoluted C 1s spectra and from ~2 to 5% for the N 1s spectra. The passivation ability of the peptides was analyzed by comparing the ratios of the oxide components to the nonoxide components in the XPS spectra. The thickness of the oxide layer was also approximated by accounting for the attenuation of the substrate photoelectrons through the oxide layer. We find that the oxide layer regrowth still occurs after peptide functionalization. However, the oxide layer thicknesses for peptide-functionalized samples do not reach as received levels, indicating that the peptides do have some passivation ability on InAs. 相似文献
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Frank F. Jewett 《Fresenius' Journal of Analytical Chemistry》1898,37(7):451
Ohne Zusammenfassung 相似文献
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The useful electrophilic fluorinating agent, acetyl hypofluorite, was obtained by passing F2 diluted in N2 through columns containing complexes of alkali metal acetates with acetic acid. Acetyl hypofluorite obtained from KOAc(HOAc)1.5 and 0.14% F2 in N2 was reacted with tri--acetyl-D-glucal in CCl3F to obtain tetra--acetyl-2-deoxy-2-fluoro-D-glucose in 68% yield based on F2. These conditions are appropriate to the radiosynthesis of 18F-labeled 2-deoxy-2-fluoro-D-glucose for positron emission tomography. Important variables were the metal cation used, the ratio of HOAc to MOAc and the water content of the complex. 相似文献
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Gribble GW Switzer FL Bushweller JH Jewett JG Brown JH Dion JL Bushweller CH Byrn MP Strouse CE 《The Journal of organic chemistry》1996,61(13):4319-4327
The (1)H NMR spectra of 10-benzyl-9,11-diphenyl-10-azatetracyclo[6.3.0.0.(4,11)0.(5,9)]undecane (BnPh(2)()) and 10-methyl-9,11-diphenyl-10-azatetracyclo[6.3.0.0.(4,11)0.(5,9)]undecane (MePh(2)()) decoalesce due to slowing inversion at nitrogen and to slowing isolated bridgehead phenyl rotation. The high nitrogen inversion barriers in MePh(2)() (DeltaG() = 12.2 +/- 0.1 kcal/mol at 250 K) and BnPh(2)() (DeltaG() = 10.6 +/- 0.1 kcal/mol at 215 K) are typical of tertiary amines in which at least one C-N-C bond angle is constrained to a small value. Compared to the minuscule rotation barriers about sp(2)-sp(3) carbon-carbon bonds in simple molecular systems, the bridgehead phenyl rotation barriers in MePh(2)() (DeltaG() = 9.8 +/- 0.1 kcal/mol at 210 K) and BnPh(2)() (DeltaG() = 9.8 +/- 0.1 kcal/mol at 210 K) are unusually high. Molecular mechanics calculations (MMX force field) suggest that the origin of the high phenyl rotation barriers lies in the close passage of an o-phenyl proton and a methyl (or benzylmethylene) proton in the transition state. BnPh(2)() crystallized from hexane as white needles in the monoclinic system Pn. Unit cell dimensions are as follows: a = 12.198(1) ?, b = 6.1399(6) ?, c = 14.938(2) ?, beta = 107.470(4) degrees, V = 1067.1(2) ?(3), Z = 2. In the crystal molecular structure, the imine bridge CNC bond angle in BnPh(2)() is constrained to a small value (96 degrees ). The benzylic phenyl group is oriented gauche to the nitrogen lone pair. 相似文献
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