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1.
P. G. Royall D. Q. M. Craig M. Reading T. J. Lever 《Journal of Thermal Analysis and Calorimetry》2000,60(3):795-805
The purpose of this study was to investigate the feasibility of modulating the temperature programme of a conventional DSC
by use of an alternating gas-flow system. Modulated temperature differential scanning calorimetry (MTDSC) is an important
thermal analysis technique but suffers from a limited applicable frequency range due to the mass of the sample and DSC cell
leading to the impingement of thermal conductivity effects. We suggest that the frequency limit can be increased by replacing
the cell as the source of temperature modulation with an external gaseous source, directed towards the sample and reference
pans. In this evaluation, an alternating gas-flow was passed through a line to a forced gas-flow accessory (FGFA). The FGFA
consisted of two matched cylinders containing chambers that allowed pre-temperature-equilibration of the stream of gas before
it was passed over the sample and reference pans. The development of this device revealed the essential practical requirements
of gas-flow modulation for high-frequency temperature modulation. These include the following: an appropriately sealed tunable
gas supply to both sample and reference pans, an effective method for high-frequency cycling of the gas-flow rate, a small
aperture to deliver the flowing gas directly over the pan and a temperature equilibration chamber. The results from samples
of quenched PET and amorphous Saquinavir indicate that gas-flow modulation is indeed feasible, with the FGFA able to raise
the attainable temperature modulation frequency by an order of magnitude compared to conventional MTDSC.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
The reaction of the [Ru(bpy)2(MeOH)2]2+ cation (bpy = 2,2'-bipyridine) with 1,2,4,5-tetraaminobenzene in the presence of trace water and oxygen yields the cation [(bpy)2Ru(1,2,4,5-tetraimino-3,5-diketocyclohexane)Ru(bpy)2]4+. This binuclear species undergoes ligand-based reductions, giving the 3+ and 2+ charged species. The X-ray structure, electrochemistry, ZINDO calculations, and NMR, ESR, UV/vis, and IR spectra were analyzed where possible, giving an electronic model of the binuclear species and some of its redox products. The X-ray structure reveals the [(bpy)2Ru] fragments symmetrically disposed across the 1,2,4,5-tetraimino-3,5-diketocyclohexane bridge in a molecule with Cs symmetry. 相似文献
3.
S. Zecevic B. Simic-Glavaski E. Yeager A.B.P. Lever P.C. Minor 《Journal of Electroanalytical Chemistry》1985,196(2):339-358
Cyclic voltammetric measurements of adsorbed Fe- and Co-tetrasulfonated phthalocyanine (TsPc) and Co-phthalocyanine (Pc) have been carried out on ordinary pyrolytic graphite and silver electrodes at different solution pH ranging from 1 to 13. Many voltammetric peaks were found to be pH dependent with a slope of ?59 mV/ unit pH. In some instances this dependence was observed in alkaline or acid solutions only. The influence of oxygen has been also examined. 相似文献
4.
Requejo-Isidro J McGinty J Munro I Elson DS Galletly NP Lever MJ Neil MA Stamp GW French PM Kellett PA Hares JD Dymoke-Bradshaw AK 《Optics letters》2004,29(19):2249-2251
We report the development of a high-speed wide-field fluorescence-lifetime imaging (FLIM) system that provides fluorescence-lifetime images at rates of as many as 29 frames/s. A FLIM multiwell plate reader and a potentially portable FLIM endoscopic system operating at 355-nm excitation have been demonstrated. 相似文献
5.
A.B.P. Lever 《Coordination chemistry reviews》2010,254(13-14):1397-1405
Density functional theory (DFT) calculations are carried out on an extensive series of ruthenium complexes with the non-innocent (redox active) o-benzoquinonediimine (bqdi) ligand, namely [Ru(WXYZ)(bqdi)]n+ where WXYZ are a range of spectator ligands including ammonia, phosphines, 2,2′-bipyridine, 2,2′,2″-terpyridine, carbon monoxide, water, halide, acetonitrile, triazacyclononane, nitrosyl, cyclam, etc. In addition, a smaller series, Ru(acac)2(R-bqdi) is explored, where acac = 2,4-pentanedionate, and R = H, Cl, Me, NO2 and N-SO2Me. A range of properties including Mulliken and Natural population analysis (NPA) charges, Mayer bond orders (Ru–N, CN, CC, etc.), net σ-donation and net π-back donation, and percentage Ru 4dπ in the LUMO, are derived and correlated with experimental properties including oxidation and reduction potentials and ligand electrochemical parameters, EL(L). The various properties are understood in terms of the primary involvement of π-back donation to the π*-LUMO of bqdi. Net π-back donation is derived from the contribution of the π*-LUMO (and higher virtual orbitals) of bqdi, to filled molecular orbitals of the complex. The question of whether these species should be considered exclusively as being represented as [RuIIL4(bqdi)] or [RuIIIL4(sqdi)] (sqdi = o-benzosemiquinonediimine) is briefly considered and evidence presented for the former electronic structure. This is written as a pedagogical treatise rather than a detailed research discussion of the electronic properties of these molecules. 相似文献
6.
S. E. D. Webb S. Lévêque-Fort D. S. Elson J. Siegel T. Watson M. J. Lever M. Booth R. Juskaitis M. A. A. Neil L. O. Sucharov T. Wilson P. M. W. French 《Journal of fluorescence》2002,12(2):279-283
We have developed a compact system for wide-field fluorescence imaging, resolved in three spatial dimensions, lifetime and wavelength, that is based on a gated optical intensifier and an all-solid-state diode pumped Cr:LiSAF oscillator-amplifier system. Exploiting spectral separation, the system has been applied to human teeth, obtaining good lifetime contrast between enamel, dentin and caries. Exploiting spectral separation combined with depth resolution, the study of fluorescent microspheres led to an enhancement in both lifetime contrast and lateral resolution. 相似文献
7.
Primary alkyl halides and epoxides react with 1-lithiocyclopropyl phenyl sulfide to give derivatives suitable for transformation to carbonyl compounds or for desulfurization. 相似文献
8.
A range of α-alkoxyphosphine oxides, including novel α-methoxyallyl oxides, are readily prepared from chlorodiphenylphosphine and acetals. 相似文献
9.
In the study of ion implantation, electrically active ions or noble gas ions are often used for damage study, range profiling, etc. Very seldom are both electrically active ions and noble gas ions implanted at about the same depth. In the work reported here, argon and arsenic ion implants and their interference in diffusion were studied by using backscattering, electrical measurements, and transmission electron microscopy (TEM). Several unexpected phenomena were observed. First, when both Ar and As are implanted in high doses (about 1016/cm2), at depths around a few hundred nanometers, the Ar significantly hampers the As diffusion, and the As prevents the outdiffusion of the Ar. The interference occurs regardless of which ion is implanted first. Second, when Si wafers uniformly doped with about 4 × 1019 As/cm3 are ion-implanted with log16 Ar/cm2 at 130 keV, the As atoms stay uniformly distributed. When the sample is annealed at a temperature between 900 and 1100°C in a nitrogen ambient, however, double peaks for both Ar and As are observed by backscattering. The nonuniform distribution of As after the heat treatment of the uniformly distributed As is puzzling. Finally, the As profile for an As capsule diffused on a silicon wafer is greatly altered when the wafer has been pre-implanted with Ar. Arsenic atoms tend to build up at the same depth as the Ar atoms. Several other observations concerning Ar and As are equally puzzling. This paper discusses the observations and some plausible explanations. 相似文献
10.
The reaction of Mo2(SCH2CH2S)2Cp2 (1; Cp=eta-C5H5) with an excess of an alkyne in refluxing dichloromethane affords the bis(dithiolene) complexes Mo2(micro-SCR1=CR2S)2Cp2 (2a, R1=R2=CO2Me; 2b, R1=R2=Ph; 2c, R1=H, R2=CO2Me) whereas with 1 equiv of alkyne at room temperature the mixed dithiolene-dithiolate species Mo2(micro-SCR1=CR2S)(micro-SCH2CH2S)Cp2 (3a, R1=R2=CO2Me; 3b, R1=R2=Ph) are formed. The remaining dithiolate ligand in 3 can then be converted into a different dithiolene by reaction with a second alkyne. Applying this methodology, we have used bis(diphenylphosphino)acetylene to prepare the first examples of complexes containing phosphine-substituted dithiolene ligands: Mo2{micro-SC(CO2Me)=C(CO2Me)S}{micro-SC(PPh2)=C(PPh2)S}Cp2 (2g) and Mo2{micro-SC(PPh2)=C(PPh2)S}2Cp2 (2h). Tri- and tetrametallic complexes can then be assembled by coordination of these diphosphines to CpRuCl units by reaction with CpRu(PPh3)2Cl. Electrochemical studies of the Ru(II)/Ru(III) couple in Mo2{micro-SC(PPh2)=C(PPh2)S}2Cp2(RuClCp)2 (4b) reveals that the two separate ruthenium centers are oxidized electrochemically at different potentials, demonstrating communication between them through the dimolybdenum bis(dithiolene) core. Density functional theory calculations were carried out to explore the electronic structures of these species and to predict and assign their electronic spectra. 相似文献