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31.
Copper‐Doped CdSe/ZnS Quantum Dots: Controllable Photoactivated Copper(I) Cation Storage and Release Vectors for Catalysis 下载免费PDF全文
Joseph C. Bear Dr. Nathan Hollingsworth Dr. Paul D. McNaughter Dr. Andrew G. Mayes Dr. Michael B. Ward Prof. Thomas Nann Dr. Graeme Hogarth Prof. Ivan P. Parkin 《Angewandte Chemie (International ed. in English)》2014,53(6):1598-1601
The first photoactivated doped quantum dot vector for metal‐ion release has been developed. A facile method for doping copper(I) cations within ZnS quantum dot shells was achieved through the use of metal‐dithiocarbamates, with Cu+ ions elucidated by X‐ray photoelectron spectroscopy. Photoexcitation of the quantum dots has been shown to release Cu+ ions, which was employed as an effective catalyst for the Huisgen [3+2] cycloaddition reaction. The relationship between the extent of doping, catalytic activity, and the fluorescence quenching was also explored. 相似文献
32.
Mark D. Hollingsworth Kenneth D. M. Harris William Jones John M. Thomas 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(2):273-277
Electron spin resonance (ESR) spectroscopy was used to study the photodecomposition of long-chain diacyl peroxides trapped in channels within zeolites (silicalite and ferrierite) and urea clathrates. ESR spectra of radical pairs in single crystals of the urea clathrates of diundecanoyl peroxide (UP), lauroyl peroxide (LP) andbis(6-bromohexanoyl) peroxide (6-BrHP) show that the alkyl radicals respond to the CO2 stress field by recoiling along the channel. In each clathrate, the inter-radical distance for the most relaxed pair is approx. 9.5 Å, suggesting nearly complete relaxation of stress from the CO2s. The rotational mobility and exceptional kinetic stability of the radicals is attributed to relaxation of stress and the lack of a convenient escape route for the CO2s. X-ray diffraction indicates one-dimensional ordering of guests in 6-BrHP/urea and 3-dimensional ordering of guests in UP/urea. Solid state NMR experiments on LP/urea suggest high guest mobility under ambient conditions. When UP and 6-BrHP were intercalated into silicalite, photolysis yielded isolated radicals, but no radical pairs, even as low as 20 K. 相似文献
33.
Chen Y Vela J Htoon H Casson JL Werder DJ Bussian DA Klimov VI Hollingsworth JA 《Journal of the American Chemical Society》2008,130(15):5026-5027
Semiconductor nanocrystal quantum dots (NQDs) comprise an important class of inorganic fluorophores for applications from optoelectronics to biology. Unfortunately, to date, NQD optical properties (e.g., their efficient and particle-size-tunable photoluminescence) have been susceptible to instabilities at the bulk and single-particle levels. Specifically, ensemble quantum yields (QYs) in emission are dependent upon NQD surface chemistry and chemical environment, while at the single-particle level, NQDs are characterized by significant fluorescence intermittency (blinking) that hinders applications as single-photon light sources for quantum informatics and biolabels for real-time monitoring of single biomolecules. Furthermore, while NQDs are significantly more photostable than their organic dye counterparts, traditional NQDs photobleach over periods of seconds to many minutes. Here, we demonstrate for the first time that by encapsulating the NQD core in a sufficiently thick inorganic shell, we are able to divorce NQD function from NQD surface chemistry and chemical environment. We show that our "giant" NQDs (g-NQDs) are functionally distinct from standard core-only, core/shell and even core/multishell NQDs. g-NQDs are substantially less sensitive to changes in surface chemistry. They do not photobleach under continuous laser excitation over periods of several hours repeated over several days, and they exhibit markedly different blinking behavior; >20% of the g-NQDs do not blink, while >40% have on-time fractions of >80%. All of these observations are in stark contrast with control samples comprising core-only and standard, thinner core/multishell NQDs. 相似文献
34.
35.
The novel methylcadmium aminoalkoxides MeCd(dmae) (Hdmae = dimethylaminoethanol), MeCd(bdmap) [Hbdmap = 1,3- bis-(dimethylamino)-propan-2-ol], and MeCd(tdmap) [tdmap = 1,3- bis(dimethylamino)-2-(dimethylaminomethyl)-propan-2-ol] have been synthesized and structurally characterized. MeCd(dmae) (1) forms a tetrameric heterocubane with a Cd4O4 core, while MeCd(bdmap) (2) is trimeric and MeCd(tdmap) (3) is a dimer. Only in the case of MeCd(dmae) are all the ligand donors fully utilized. In solution, MeCd(tdmap) undergoes a Schlenk equilibrium, with Me2Cd and Cd(tdmap)2 evident at 218 K. The structure and solution-state chemistry of Cd(tdmap)2 (5) have been independently studied and, in the solid-state, found to exist as a dimer whose coordination number at cadmium (CN = 6) is greater than in the organocadmium complexes (CN = 4, 5). MeCd(tdmap) has been used as a single-source precursor for CdO films by LPCVD with a glass substrate temperature of only 140 degrees C. Evidence is also presented for the formation of a heterometallic precursor, [(MeZn)(MeCd)(tdmap)2] (6), which has been used to deposit films of CdO mixed with ZnO by LPCVD at 140 degrees C. The structure of Me4Cd4(tdmap)2Cl2 (4), obtained serendipitously, is also included. Crystal data: 1, C20H52Cd4N4O4, FW 862.26, triclinic, P1, a = 11.47560(10), b = 13.55400(10), c = 21.5966(2) A, alpha = 99.7869(4), beta = 90.7476(4), gamma = 98.7823(4) degrees, V = 3268.82(5) A(3), Z = 4; 2, C27H67Cd3N6O3, FW 861.07, triclinic, P1, a = 11.4148(2), b =13.1886(2), c = 14.3139(3) A, alpha = 102.1962(10), beta = 108.3064(10), gamma = 100.8446(10) degrees, V = 1923.09(6) A(3), Z = 4; 3, C22H54Cd2N6O2, FW 659.51, monoclinic, P2(1)/n, a = 10.2912(1), b = 13.46930(1), c = 11.79130(1) A, beta = 112.8051(1) degrees, V = 1506.59(2) A(3), Z = 2; 4, C24H60Cd4Cl2N6O2, FW 985.28, monoclinic, P2(1)/c, a = 10.89780(10), b = 20.3529(2), c = 16.5317(2) A, beta = 94.8550(10) degrees, V = 3653.61(7) A(3), Z = 4; 5, C40H96Cd2N12O4, FW 1034.09, orthorhombic, P2(1)cn, a = 12.33290(10), b = 14.25060(10), c = 29.9003(2) A, V = 5255.01(7) A(3), Z = 4. 相似文献
36.
Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid 下载免费PDF全文
Dr. Nathan Hollingsworth Dr. S. F. Rebecca Taylor Miguel T. Galante Dr. Johan Jacquemin Dr. Claudia Longo Dr. Katherine B. Holt Prof. Nora H. de Leeuw Prof. Christopher Hardacre 《Angewandte Chemie (International ed. in English)》2015,54(47):14164-14168
A new low‐energy pathway is reported for the electrochemical reduction of CO2 to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P66614][124Triz] is able to chemisorb CO2 through equimolar binding of CO2 with the 1,2,4‐triazole anion. This chemisorbed CO2 can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO2 within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P66614][NTf2]) undergoes reduction at significantly increased overpotentials, producing only CO as the product. 相似文献
37.
Changyou YuanRawle I. Hollingsworth 《Tetrahedron letters》2011,52(42):5421-5423
The important d-glucose and d-glucose 6-phosphate analogues 1,5-anhydro-d-glucitol and 1,5-anhydro-d-glucitol 6-phosphate were prepared from methyl-d-glucoside in high yield and purity. Protecting of the hydroxyl groups as their allyl ether followed by reductive cleavage of the glycosidic linkage with triethylsilane formed the protected anhydroglucitol. No ring rearrangement or ring contraction was observed during the reduction step. Using the PdCl2-CuCl2-activated charcoal system, the allyl ether bond was cleaved with a low loading of the catalyst (0.0025 equiv per allyl group). 1,5-Anhydro-d-glucitol 6-phosphate was prepared by the phosphylation of 1,5-anhydro-d-glucitol. 相似文献
38.
Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
39.
KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
40.
Hollingsworth KG Sederman AJ Buckley C Gladden LF Johns ML 《Journal of colloid and interface science》2004,274(1):244-250
Emulsion droplet sizing using pulsed field gradient (PFG) nuclear magnetic resonance (NMR) is a well-established technique. Traditionally these measurements require total acquisition times of typically 5-20 min per sample, which severely limits our ability to use this method to study dynamic processes. Here we present the application and verification of an NMR pulse sequence, Difftrain, which enables emulsion droplet size distributions to be measured in 3-10 s. We have previously introduced applications of Difftrain (C. Buckley, K.G. Hollingsworth, A.J. Sederman, D.J. Holland, M.L. Johns, L.F. Gladden, J. Magn. Reson. 161 (2003) 112-117), including the droplet sizing of a single unimodal emulsion sample. In this paper, several model emulsions containing different oils are measured and the results compared directly with sizing provided by laser scattering. In this manner, the Difftrain method is verified and its possibilities and limitations are explored. Guidelines are proposed for the range of droplet sizes for which accurate results can be produced. The Difftrain technique opens up the possibility of studying non-equilibrium emulsions; a study of the in situ emulsification of a 21% v/v water-in-silicone oil emulsion is presented. 相似文献