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排序方式: 共有342条查询结果,搜索用时 15 毫秒
1.
Atomic layer deposition in nanometer-level replication of cellulosic substances and preparation of photocatalytic TiO2/cellulose composites 总被引:4,自引:0,他引:4
Kemell M Pore V Ritala M Leskelä M Lindén M 《Journal of the American Chemical Society》2005,127(41):14178-14179
TiO2 replicas of filter paper with nanometer-level accuracy were prepared by atomic layer deposition of thin conformal TiO2 coating, followed by a removal of the paper by air-anneal at 450 degrees C. Photocatalytic anatase TiO2/cellulose composites were also made by leaving the paper intact. The TiO2 films were deposited from Ti(OMe)4 and H2O at 150-250 degrees C. The photocatalytic activity of the TiO2/cellulose composite was verified by photocatalytic reduction of Ag(I) from an aqueous solution to Ag nanoparticles on the TiO2 surface. The TiO2/cellulose composites are mechanically more stable than the free-standing TiO2 replicas and are therefore potentially suitable as lightweight, high surface area photocatalysts. 相似文献
2.
The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford [(Ph(3)PO)(2)H](2)[Te(2)X(10)] [X = Cl (1), Br (2)] and [(Ph(3)PO)(3)(OH(3)])(2)[TeI(6)] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te(2)X(10)](2-) anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and [Ph(3)POH...OPPh(3)](+) cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and [(Ph(3)PO)(3)(OH(3))](+) cations. The reaction of TeBr(4) and PPh(3) also results in the formation of formally zwitterionic Ph(3)PO(CH(2))(4)TeBr(4) (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr(4). The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C(4)H(8)TeI(2) (5). The reaction may initially lead to Ph(3)PI(2) that reacts with THF yielding Ph(3)PO and ICH(2)(CH(2))(2)CH(2)I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C(4)H(8)TeI(2) (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI(4) and PPh(3): Both are formally 1:1 adducts of 5 and TeI(4), but they differ considerably in their structures. 6a can be formulated as [C(4)H(8)TeI(+)](2)[Te(2)I(10)(2-)] and 6b as [C(4)H(8)TeI(+)](2)(TeI(3)(+))(2)(I(-))(4). The latter compound exhibits framework similar to that of the tetramers in gamma- and delta-TeI(4). 相似文献
3.
Conversion of adsorption properties of activated charcoal (C∗) by metal modification towards selenite, selenate and seleno-dl-methionine (Se-Met) was studied. Several metals were included in modification studies and also a procedure was developed for the separation and independent determination of microgram quantities of these selenium species in aqueous solution. Selenium species were collected one by one from the same sample solution onto collector material by adsorbing them directly or after complex formation onto different metal-loaded activated charcoals (MgC∗ and FeC∗). The mass of selenium in these collectors was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). Detection limits for all three selenium species were better than 6 μg corresponding to concentration of 60 μg/l with 0.100 l of initial sample volume. 相似文献
4.
Tanskanen H Khriachtchev L Lundell J Räsänen M 《The Journal of chemical physics》2004,121(17):8291-8298
We investigate the formation mechanism of HXeCCXeH in a Xe matrix. Our experimental results show that the HXeCCXeH molecules are formed in the secondary reactions involving HXeCC radicals. The experimental data on the formation of HXeCCXeH is fully explained based on the model involving the HXeCC+Xe+H-->HXeCCXeH reaction. This reaction is the first case when a noble-gas hydride molecule is formed from another noble-gas molecule. In addition, we investigate the (12)C/(13)C isotope effect on the vibrational properties of organo-noble-gas hydrides (HKrCCH, HXeCCH, HXeCC, and HXeCCXeH) in noble-gas matrixes. The present experimental results and ab initio calculations on carbon isotope shifts of the vibrational modes support the previous assignments of these molecules. Upon (12)C to (13)C isotope substitution, we observed a pronounced effect on the H-Kr stretching mode of HKrCCH (downshift of 1.0-3.6 cm(-1), depending on the matrix site) and a small anomalous shift (+0.1 cm(-1)) of the H-Xe stretching mode of HXeCCH and HXeCCXeH. 相似文献
5.
Sharp peaks were observed in the IR spectra of allyl alcohol dimers in the νOH and τOH regions in low-temperature Ar and N2 matrices. In Ar a peak at 3587 cm?1 was found to increase in intensity upon annealing and decrease upon IR irradiation; it is concluded that this peak is due to an OH...π interaction (of a cyclic structure) present in part of the dimers. This is the first time such an interaction and photoprocess have been found for an alcohol in matrices. Also a faster photo-process was found. Confomer changes in the monomers accompany the photoprocess in allyl alcohol dimers. 相似文献
6.
Kalevi Pihlaja Reijo Sillanpää Martti Dahlqvist Géza Stájer Markku Ahlgren 《Structural chemistry》1993,4(3):203-210
3-Oxo-1,3-oxathiane (1) and its monomethyl derivatives were prepared by oxidation of the corresponding 1,3-oxathianes. The structural analysis was carried out by1H and13C NMR, FTIR, and mass spectrometry. At 298 K compound1 was a 1 1 (at 173 K a 3 1) mixture of the SO(ax) and SO(eq) chair forms. The major oxidation products of methyl 1,3-oxathianes attained exclusively the SO(ax), Me(eq) chair forms except that of the 5-methyl derivative, which consisted of 7% of the SO(eq), Me(ax) chair conformation in CDCl3 solution. The minor products of oxidation existed in anancomeric SO(eq), Me(eq) chair conformations. The oxidation of 2-methyl- 1,3-oxathiane, however, led to 3,3-dioxo derivative (6) in addition to thetrans [SO(eq)] monoxide. The crystal structures of6 andtrans-3-oxo-5-methyl-1,3-oxathiane were solved by X-ray diffractometry. 相似文献
7.
Peter Segl'a Martina Palicov Dusan Miklos Marian Koman Milan Melník Maria Korabik Jerzy Mrozinski Tadeusz Glowiak Markku R. Sundberg Peter Lnnecke 《无机化学与普通化学杂志》2004,630(3):470-478
Synthesis and characterization of seven new complexes [Cu(2‐MeSnic)2(CH3OH)]2 (where 2‐MeSnic is 2‐methylthionicotinate), [Cu(2‐MeSnic)2L2]2 (where L is pyridine — py, ethylnicotinate — Etnic and butylnicotinate — Bunic), [Cu(2‐MeSnic)2L2(H2O)2] (where L is py and nicotinamide — nia) and [Cu(2‐MeSnic)2(N‐Menia)2(H2O)2]·2H2O (where N‐Menia is N‐methylnicotinamide) are reported. The characterization were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic susceptibility measurements over a temperature range of 1.8 — 300 K or 70 — 300 K. Three complexes of different type were studied by X‐ray analysis. The molecule of [Cu(2‐MeSnic)2(CH3OH)]2 has dimeric paddle‐wheel cage structure with a tetragonal pyramidal arrangement around CuII. The dimer results from the fact that carboxyl groups of four 2‐MeSnic anions function as bridging in a syn‐syn arrangement. On the other hand [Cu(2‐MeSnic)2(py)2]2 forms dimers with hexacoordinated CuII atoms in highly distorted coordination octahedra, each with two oxygen atoms of bridging carboxyl groups in an anti‐anti arrangement of two 2‐MeSnic anions, with two oxygen atoms of one asymmetrically chelating 2‐MeSnic anion and with two nitrogen atoms of two pyridine ligands. The temperature independent EPR spectrum for this complex exhibits an axial signal which corresponds to almost isolated S = 1/2 magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic interaction between the two metal ions with J = —0.65 cm—1. The CuII atom in complex [Cu(2‐MeSnic)2(py)2(H2O)2] is hexacoordinated in an elongated centrosymmetrical tetragonal‐bipyramidal arrangement (4 + 2). Based on the molecular structure the electronic, infrared, electron paramagnetic resonance spectra and magnetic properties are discussed and stereochemistry as well as the mode of ligand coordination in new solid complexes under study have been determined. 相似文献
8.
Tanskanen H Khriachtchev L Räsänen M Feldman VI Sukhov FF Orlov AY Tyurin DA 《The Journal of chemical physics》2005,123(6):64318
Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (nu7 and nu5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the nu7 mode is in agreement with previous experimental and theoretical results whereas the nu5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results. 相似文献
9.
Nemukhin AV Grigorenko BL Khriachtchev L Tanskanen H Pettersson M Räsänen M 《Journal of the American Chemical Society》2002,124(36):10706-10711
Theoretical and matrix-isolation studies of intermolecular complexes of HXeOH with water molecules are presented. The structures and possible decomposition routes of the HXeOH-(H(2)O)(n)(n = 0, 1, 2, 3) complexes are analyzed theoretically. It is concluded that the decay of these metastable species may proceed through the bent transition states (TSs), leading to the global minima on the respective potential energy surfaces, Xe + (H(2)O)(n+1). The respective barrier heights are 39.6, 26.6, 11.2, and 0.4 kcal/mol for n = 0, 1, 2, and 3. HXeOH in larger water clusters is computationally unstable with respect to the bending coordinate, representing the destabilization effect. Another decomposition channel of HXeOH-(H(2)O)(n), via a linear TS, leads to a direct break of the H-Xe bond of HXeOH. In this case, the attached water molecules stabilize HXeOH by strengthening the H-Xe bond. Due to the stabilization, a large blue shift of the H-Xe stretching mode upon complexation of HXeOH with water molecules is featured in calculations. On the basis of this computational result, the IR absorption bands at 1681 and 1742 cm(-1) observed after UV photolysis and annealing of multimeric H(2)O/Xe matrixes are assigned to the HXeOH-H(2)O and HXeOH-(H(2)O)(2) complexes. These bands are blue-shifted by 103 and 164 cm(-1) from the known monomeric HXeOH absorption. 相似文献
10.
The luminescence properties of Eu2+, Sn2+, and Pb2+ in SrB6O10 have been studied both at room-temperature and liquid-helium temperature and the decay times of Sn2+ and Pb2+ in this matrix have been measured and analyzed. According to the emission spectrum of Eu2+ there seems to be three different cation sites in SrB6O10. Europium, tin, and lead were also used as sensitizers for Mn2+ and the energy transfer processes were characterized. Eu2+-Mn2+ energy transfer was inefficient due to the transfer within different Eu2+ centers. The sensitization action of Sn2+ and Pb2+ on Mn2+ was different because lead-lead energy transfer occurs (even at 4.2 K) but tin-tin transfer can be neglected. A fast diffusion model for the Pb2+ system is suggested. 相似文献