Sol-gel-derived Mg(OH)(2) gel was coated onto TiO(2) nanoparticles, and the subsequent thermal topotactic decomposition of the gel formed a highly nanoporous MgO crystalline coating. The specific surface area of the electrode that was prepared from the core-shell-structured TiO(2) nanoparticles significantly increased compared with that of the uncoated TiO(2) electrode. The increase in the specific surface area of the MgO-coated TiO(2) electrode was attributed to the highly nanoporous MgO coating layer that resulted from the topotactic reaction. Dye adsorption behavior and solar cell performance were significantly enhanced by employing the MgO-coated TiO(2) electrode. Optimized coating of a MgO layer on TiO(2) nanoparticles enhanced the energy conversion efficiency as much as 45% compared to that of the uncoated TiO(2) electrode. This indicates that controlling the extrinsic parameters such as the specific surface area is very important to improve the energy conversion efficiency of TiO(2)-based solar cells. 相似文献
A fast multi‐residue screening method for determining pesticides in tea is described. Pesticides are extracted from tea with acetone and methylene chloride, then enriched and cleaned up with solid phase extraction (SPE) prior to gas chromatographic determination. The fast screening is achieved by a gas chromatograph system equipped with dual‐column, dual‐tower auto‐sampler and both electron capture detector (ECD) and flame photometric detector (FPD). Optimal conditions are investigated for the prospective pesticides including column selection, detection mode, the retention behaviors, quantitative calibration, as well as the recoveries and repeatability of pesticides from tea samples. Under the optimal conditions, with the FPD‐P detector accompanied CP‐SIL 13CB column, 48 pesticides can be separated well and detected within 38 min; and with a DB‐5 column, 35 ECD‐detectable pesticides can be separated and detected within 46 min. The recoveries of 84 pesticides in tea samples are 65–120% with 0.34–16% RSD for spiking 0.02–3.0 mg/kg standard species. Because of the thermal instability of most pesticides, direct cold extraction of pesticides from a tea sample is recommended. The proposed method provided a very fast and efficient procedure to screen 84 pesticides from a complicated tea sample matrix. 相似文献
meso-Tetraphenylporphyrinatothallium(III) cyanide, Tl(tpp)(CN), was previously assumed to be monomeric and has been confirmed by X-ray analysis to exist as two independent molecules in one asymmetric unit. This unit displays two square-pyramidal coordination geometries for the thallium atoms with the cyano ligand coordinated to both Tl atoms. It crystallizes in the triclinic space group P
, with a 10.003(3), b 16.231(7), c 21.277(8) Å, 89.98(3), β 90.57(3), γ 90.31(3)°' and z = 4. The structure was solved by direct methods. A total of 7995 unique reflections having I > 3σ(I) was measured with an automated diffractometer and used to refine the crystal structure to a conventional R factor of 6.05 %. The thallium-cyanide distances are 2.140(14) Å (for thallium(I)) and 2.277(14) Å (for thallium(2)) respectively, with thallium(1) situated 0.908 Å above the porphyrin ring and thallium(2) located 1.027 Å below the ring. IR and NMR spectroscopy p rovide complementary methods for investigation of the CN ligand. The characteristic band observed at 2160 cm−1 in the FTIR spectrum is assigned to the CN stretching in the Tl(tpp)(CN) complex. The 13C resonance of axial cyano ligand is observed with a pulse delay of 3.5 s at 24°C at 139.2 ppm (with 1J(205Tl-13C) 5394 and 1J(203Tl-13C) 5344 Hz). This observation disagrees with the conclusion, drawn from previous work, in that an exchange process involving the apical ligand explains the invisibility due to line broadening at 35°C of the 13C signal. 相似文献
[reaction: see text] The tricyclic benzothiazine 15 was prepared in a straightforward fashion via a completely stereoselective intramolecular Friedel-Crafts alkylation. This compound represents a potential precursor to the antitubercular agent, pseudopteroxazole. Its synthesis proceeded via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an alpha,beta-unsaturated ester, followed by functional group manipulations. 相似文献
Cellulose nanofibril (CNF) aerogels have attracted great interests in recent years due to the low cost, sustainability and biocompatibility of raw CNF. However, the poor thermal stability and flammable feature of CNF aerogels have limited their wider applications. In this paper, polydopamine/CNF composite aerogels with good comprehensive properties are fabricated by modification of CNF with polydopamine and metal coordination bonds crosslinking. The microstructure and properties of composite aerogels are thoroughly characterized by a variety of tests. It is found that the microstructure of aerogels are more regular and the compressive strength of aerogels are enhanced by the incorporation of polydopamine and Fe3+ crosslinking. Importantly, the thermal stability and flame resistance of aerogels are significantly improved, which permit the application of composite aerogels in high-temperature thermal insulation. In addition, the reversible characteristic of metal coordination bonds allows the water induced healing of fractured composite aerogels. This study is expected to provide information for future development of green and high-performance aerogels.