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31.
Vaughn AE Bassil DB Barnes CL Tucker SA Duval PB 《Journal of the American Chemical Society》2006,128(33):10656-10657
Photolysis of the uranyl(VI) Schiff base complex UO2(tBu4-salphen)(THF) (1a) with cobaltocene in THF affords [Cp2Co][UO2(tBu4-salphen)(OH)] (2) in high yield while irradiation in toluene yields no reaction. Electronic emission spectra of 1a reveal a large Stokes' shift in toluene similar to that observed in the free ligand, while in THF the structural rearrangement responsible for this shift is blocked. Instead, the ligand-centered excited state is redirected to the uranyl(VI) center by way of energy transfer, thus generating 2 from the intramolecular activation of a coordinated THF molecule. 相似文献
32.
Kannan S Vaughn AE Weis EM Barnes CL Duval PB 《Journal of the American Chemical Society》2006,128(43):14024-14025
In a dramatic reversal of the normal trend of observed reactivity in uranyl(VI) coordination chemistry, an unprecedented retention of the normally labile equatorial coordination plane accompanies facile and reversible axial oxo/alkoxide exchange during both the photochemical reduction of cationic uranyl(VI) phosphine-oxide complexes with organic substrates and subsequent hydrolysis of the uranium(IV) alkoxide complexes to regenerate the uranyl(VI) starting complex. 相似文献
33.
Ring shaped dots were patterned with mercaptohexadecanoic acid ink by dip-pen nanolithography. These dots have an ink-free inner core surrounded by an inked annular region, making them different from the filled dots usually obtained. This suggests a different transport mechanism than the current hypothesis of bulk water meniscus transport. A meniscus interface ink transport model is proposed, and its general applicability is demonstrated by predicting the patterned dot radii of chemically diverse inks. 相似文献
34.
Vaughn DD Patel RJ Hickner MA Schaak RE 《Journal of the American Chemical Society》2010,132(43):15170-15172
Narrow-band-gap IV-VI semiconductors offer promising optoelectronic properties for integration as light-absorbing components in field-effect transistors, photodetectors, and photovoltaic devices. Importantly, colloidal nanostructures of these materials have the potential to substantially decrease the fabrication cost of solar cells because of their ability to be solution-processed. While colloidal nanomaterials formed from IV-VI lead chalcogenides such as PbS and PbSe have been extensively investigated, those of the layered semiconductors SnS, SnSe, GeS, and GeSe have only recently been considered. In particular, there have been very few studies of the germanium chalcogenides, which have band-gap energies that overlap well with the solar spectrum. Here we report the first synthesis of colloidal GeS and GeSe nanostructures obtained by heating GeI(4), hexamethyldisilazane, oleylamine, oleic acid, and dodecanethiol or trioctylphosphine selenide to 320 °C for 24 h. These materials, which were characterized by TEM, SAED, SEM, AFM, XRD, diffuse reflectance spectroscopy, and I-V conductivity measurements, preferentially adopt a two-dimensional single-crystal nanosheet morphology that produces fully [100]-oriented films upon drop-casting. Optical measurements indicated indirect band gaps of 1.58 and 1.14 eV for GeS and GeSe, respectively, and electrical measurements showed that drop-cast films of GeSe exhibit p-type conductivity. 相似文献
35.
36.
The title compound is monoclinic,M
r
=337.8,P21/c-C
2h
5
(No. 14),a=5.508(2),b=13.944(6),c=18.238(5) Å,=95.99(3)°,V=1393.1(9) Å3,Z=4,D
x
=1.61 g cm–3, (MoK)=0.71073 Å,F(000)=660.0,=10.3 cm–1, finalR=0.051 for 2122 observed [I>3(I)] reflections. The two six-membered rings resulting from the coordination of the 1,3-propanediamine ligands to the chromium atom are in the chair conformation. The Cr-N and Cr-F distances average 2.085(4) and 1.876(3) Å, respectively. 相似文献
37.
John B. Phillips Richard B. Gaines Jan Blomberg Frans W. M. van der Wielen Jean-Marie Dimandja Vaughn Green James Granger Don Patterson Laell Racovalis Henk-Jan de Geus Jacob de Boer Peter Haglund John Lipsky Veena Sinha Edward B. Ledford 《Journal of separation science》1999,22(1):3-10
In comprehensive two-dimensional gas chromatography (GC×GC), two capillary columns are connected in series through an interface known as a “thermal modulator”. This device transforms effluent from the first capillary column into a series of sharp injection-like chemical pulses suitable for high-speed chromatography on the second column. Dramatic increases in the resolving power, sensitivity, and speed of the gas chromatograph result. This paper describes the development of a robust and reliable thermal modulator for GC×GC. 相似文献
38.
Vaughn Climenhaga Dmitry Dolgopyat Yakov Pesin 《Communications in Mathematical Physics》2016,346(2):553-602
We prove the existence of SRB measures for diffeomorphisms where a positive volume set of initial conditions satisfy an “effective hyperbolicity” condition that guarantees certain recurrence conditions on the iterates of Lebesgue measure. We give examples of systems that do not admit a dominated splitting but can be shown to have SRB measures using our methods. 相似文献
39.
40.
Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献