Transparent film materials with excellent mechanical and thermal properties were elaborated by drying a latex suspension of armored polymer/Laponite composite particles. Low‐temperature TEM observation of ultrathin cross‐sections of the films indicated a unique network morphology characterized by a “honeycomb” distribution of the Laponite platelets remindful of the original particles morphology.
This study establishes structure–property relationships for four synthetic flavin molecules as bioinspired redox mediators in electro‐ and photocatalysis applications. The studied flavin compounds were disubstituted with polar substituents at the N1 and N3 positions (alloxazine) or at the N3 and N10 positions (isoalloxazines). The electrochemical behavior of one such synthetic flavin analogue was examined in detail in aqueous solutions of varying pH in the range from 1 to 10. Cyclic voltammetry, used in conjunction with hydrodynamic (rotating disk electrode) voltammetry, showed quasi‐reversible behavior consistent with freely diffusing molecules and an overall global 2e?, 2H+ proton‐coupled electron transfer scheme. UV/Vis spectroelectrochemical data was also employed to study the pH‐dependent electrochemical behavior of this derivative. Substituent effects on the redox behavior were compared and contrasted for all the four compounds, and visualized within a scatter plot framework to afford comparison with prior knowledge on mostly natural flavins in aqueous media. Finally, a preliminary assessment of one of the synthetic flavins was performed of its electrocatalytic activity toward dioxygen reduction as a prelude to further (quantitative) studies of both freely diffusing and tethered molecules on various electrode surfaces. 相似文献
We present a computational study of new copper complexes with potential applications as sensitisers for solar cells. The applied methodology for this study is based on the density functional theory (DFT) and time-dependent DFT, using the B3LYP, PBE0 and M06 functionals with the LANL2DZ (D95V on first row), 6-31G(d,p), 6-311G(d,p) and DZVP basis sets. Optimised molecular structure, the absorption spectra, the molecular orbitals energies and the chemical reactivity parameters that arise from conceptual DFT were calculated. Solvent effects have been taken into account by an implicit approach, namely, the polarisable continuum model (PCM), using the non-equilibrium version of the integral equation formalism of the PCM model. Interesting work for experimentalists in the dye sensitised solar cells’ field. 相似文献
Intramolecular rhodium(II)-catalysed aromatic addition (Buchner) reactions of a range of α- and β-substituted α-diazoketones are reported. Both steric and electronic effects are evident for the aromatic additions investigated. In general, highly efficient aromatic addition is achieved through use of rhodium carboxylates bearing electronegative ligands, such as rhodium trifluoroacetate, while aromatic addition employing rhodium catalysts with more electron-donating ligands, such as rhodium caprolactam, is less efficient. Excellent levels of diastereoselectivity are possible for this process in the presence of rhodium acetate and rhodium caprolactam, however, a reduction in diastereocontrol is generally associated with use of the more reactive, electronegative catalysts. Interestingly, these catalyst effects can be overcome through the steric effects of the substituents on the α-diazoketone substrates, with the presence of sterically bulky substituents at the 2- or 3-position rendering the aromatic addition essentially catalyst independent in terms of efficiency and diastereocontrol. 相似文献
Summary. Let (Xt,t∈Z) be a linear sequence with non-Gaussian innovations and a spectral density which varies regularly at low frequencies. This
includes situations, known as strong (or long-range) dependence, where the spectral density diverges at the origin. We study
quadratic forms of bivariate Appell polynomials of the sequence (Xt) and provide general conditions for these quadratic forms, adequately normalized, to converge to a non-Gaussian distribution.
We consider, in particular, circumstances where strong and weak dependence interact. The limit is expressed in terms of multiple
Wiener-It? integrals involving correlated Gaussian measures.
Received: 22 August 1996 / In revised form: 30 August 1997 相似文献
This note uses Clarke's decoupling technique to obtain necessary conditions for the generalized problem of Bolza with Lipschitz continuously varying delay in both the state and velocity variables. 相似文献
The synthesis and electronic and IR spectra of CuL2(NO3)2 and CuL4(NO3)2, where L stands for morpholine, are described. The thermal behaviour of the complexes is also discussed. The solids contain distorted octahedral Cu(II) bonded to morpholine through nitrogen only. In aqueous solutions only the species CuL3(aq)2+ is stable in the concentration range 0.5 < [L] < 2 mol dm?3, its stability constant being log K3 = 14.64 ± 0.15 at 25.00°C and ionic strength 1 mol dm?3; at very high morpholine concentrations, 3.4 < [L] < 6 mol dm?3, evidence is also found for CuL4(aq)2+, the value log K4 = 15.5 being estimated. The aggressiveness of morpholine-H2O2 towards metallic copper is compared with that of ammonia-H2O2, both on thermodynamics and kinetics grounds; experimental results seems to be dominated by kinetics factors. The relevance of these results to water treatment in secondary systems of nuclear power reactors is discussed. 相似文献
The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles. 相似文献