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1.
In the FBX dosimeter solution, the excitation of xylenol orange (XO) produces maximum emission at 550–575 nm both at room and liquid nitrogen temperatures (about 85%) having a lifetime of 0.20–0.36 ns. In addition, at room temperature there is an emission at 350 nm for the excitation at 260 nm (about 15%) having a longer lifetime of 3.71–4.01 ns. Benzoic acid (BA) has excitation at 284–295 nm and emission at 320–365 nm having a lifetime of 1.38 ns. In an aqueous solution containing 5×10 −3 mol dm −3 BA, 2×10 −4 mol dm −3 XO and 0.04 mol dm −3 H 2SO 4 there is no XO emission at 550 nm due to UV absorption at 260 nm by BA. In this solution, 2 emissions are observed near 350–360 nm, having lifetimes of 1.25 ns (89%) and 2.86 ns (11%). The wavelengths for the emission of XO and absorption of ferric-XO complex are nearly the same. Excited XO produces oxidation of ferrous ions and BA increases the chain length. 相似文献
2.
Reactions of OH radicals and some one-electron oxidants with 2-aminopyridine (2-AmPy) and 3-aminopyridine (3-AmPy) were studied in aqueous solutions using pulse radiolysis technique. The OH adduct of 2-AmPy at pH 9 has an absorption maximum at 360 nm along with a weak absorption band in the visible region and was found to be reactive with oxygen. The rate constant for its reaction with O 2 was determined to be 1.0×10 8 dm 3 mol −1 s −1. At pH 4 also, the OH adduct of 2-AmPy has an absorption band at 360 nm. However, there are differences in the absorption at other wavelengths. From the plot of ΔOD vs. pH at 340 nm, the p Ka of the OH adduct was determined to be 6.5. Among the specific oxidants, only SO 4−√ radicals were able to oxidize 2-AmPy. In the case of 3-aminopyridine (3-AmPy), the transient species formed by OH radical reaction at pH 9 has an absorption maximum at 410 nm with shoulder bands on both the sides. Its absorption spectrum at pH 4 was different indicating the existence of a p K value for the OH adduct. p Ka of 3-AmPy-OH radical adduct species was evaluated to be 5.7. This adduct species was also found to be reactive with oxygen ( k=7.6×10 6 dm 3 mol −1 s −1). Specific one-electron oxidants like N 3√, Br 2−√ C 2−√ and SO 4−√ were able to oxidize 3-AmPy indicating that it is easier to oxidize 3-AmPy as compared to 2-AmPy. 相似文献
3.
Two novel Cd(II)-citrate complexes were obtained with different metal/ligand ratios through hydrothermal method. Their structures were determined by single-crystal X-ray diffraction analysis. Although their topological structures are both 2-D layer network assemblies, both central Cd(II) ions and Hcit 3− ligands display completely different coordination modes. In polymeric complex 1, Hcit 3− serves as a μ 10-bridged and central Cd(II) ions adopt 6- and 8-coordinated configurations. In contrast, a μ 9-bridged and 6- and 7-coordinated environments between Cd(II) and Hcit 3− are established in the polymeric complex 2. Two Complexes remain stable up to approximately 300 °C. The complex 1 exhibits strong fluorescent emission band at 450 nm ( λ=346 nm) as well as complex 2 exhibits strong fluorescent emission band at 430 ( λ=346 nm). 相似文献
4.
The emission intensity at 517 nm from Pt 2(pop) 44− (pop = P 2O 5H 22−) is quenched by the addition of sulphur dioxide. The sulphur dioxide coordinates at the axial platinum(II) sites by a η 1-SO 2 bond. This coordination is supported by 31p NMR and Raman spectroscopy of aqueous solutions. The electronic spectrum of a sulphur dioxide saturated solution of Pt 2(pop) 44− shows an absorption at 428.5nm ( = 4.1 × 10 4). From the decrease in the chromophore for uncomplexed Pt 2(pop) 44− the equilibrium constant for SO 2 binding is estimated to be 1.74 M 2l −2. The effect of adding different quenchers to aqueous solutions of Pt 2(pop)44− is discussed. The compound Pt 2(pop) 44− will undergo 2-electron reduction with chromous ion. 相似文献
5.
The infrared spectra of phosphinic acid R 2POOH dimers (R=CH 3, CH 2Cl, C 6H 5) have been studied in CCl 4 and CH 2Cl 2 solutions ( T=300 K). The infrared spectra of deuterated R 2POOD dimers (R=CH 3, CH 2Cl) were also studied in the gas phase ( T=400–550 K) and solid state ( T=100–300 K). They are compared with previously studied spectra of the light (non-deuterated) dimers in the gas phase, in the solid state and in low-temperature argon matrices ( T=12–30 K) in the 4000–400 cm −1 spectral region. It is found that the strong and broad ν(OH) dimer bands have similar shapes, nearly equal values of bandwidth and low-frequency shift, and possess the Hadzi ABC structure irrespective of the type of acid, significant differences of dimerization enthalpies, influence of solvent, the type of H-bonded complexes (cyclic dimers in the gas phase, in solutions, and in inert matrices, and infinite chains in the solid state), and temperature in the range 12–600 K. Isotopic ratio of the first moments of light and deuterated acid bands has been measured. Analysis of the ν(OH/OD) band of hydrogen bonded dimers of phosphinic acids shows that the interaction between the two intermolecular bonds O–HOP in a cyclic complex plays virtually no role in the mechanism of the ν(OH/OD) band formation; the shape of ν(OH/OD) band is controlled mainly by the POOH(D)O fragment; and the band shape of strong hydrogen bonded complexes is formed by a number of vibrational transitions from the ground state to different combination levels in the region 3500–1500 cm −1. 相似文献
6.
The collisional behaviour of Ba[6s5d( 3D J)], 1.151 eV above the 6s 2( 1S 0) electronic ground state, in the presence of atomic strontium, has been investigated in the ‘long-time domain' (ca. 100 μs–1 ms) following the pulsed dye-laser excitation of barium vapour at elevated temperature at λ = 553.5 nm (Ba[6s6p( 1P 1)] ← Ba[6s 2( 1S 0)]. Ba( 3D J) is subsequently produced from the short-lived 1P 1 state ( τe = 8.37 ± 0.38 ns) by a number of radiative and collisional processes. It may then be monitored in the ‘long-time domain' by atomic spectroscopic marker methods involving either collisional activation of Ba( 3D J) by Ba( 1S 0) and He buffer gas to yield Ba[6s6p( 3P J)] with subsequent emission from the 3P 1 state ( τe = 1.2 ± 0.1 μs): Ba[6s6p( 3P 1)] → Ba[6s 2( 1S 0)] + hv ( λ = 791.1 nm). Alternatively, emission from Ba( 1P 1) may be monitored at long times following the generation of this short-lived state by energy pooling following self-annihilation of Ba( 3D J) + Ba( 3D J) from Ba[6s6p( 1P 1)] → Ba[6s 2( 1S 0)] + hv ( λ = 553.5 nm). The generation of Ba( 3D J) in the presence of atomic strontium yields emission in the long-time domain from Sr[5s5p( 3P 1)] ( τe = 19.6 μs): Sr[5s5p( 3P 1)] → Sr[5s 2( 1S0)] + hv ( λ = 689.3 nm). Whilst the decay profiles at short times are complex in form, at long times all these atomic profiles show first-order kinetic removal with the decay coefficients for λ = 791.1 nm, 689.3 nm and 553.5 nm emissions in the ratio 1 : 2 : 2, consistent with overall third-order activation of the form: Ba( 3D J) + Ba( 3D J) + Sr( 1S 0) → Sr( 3P J) + 2Ba( 1S 0). The mechanism is modelled in detail, including measurement of integrated emission intensities, yielding kinetic data for fundamental collisional processes. The overall rate constant for the third-order collisional activation of Sr[5s5p( 3P J])from 2Ba[6s5d( 3D J)] + Sr[5s 2( 1S 0)] takes the upper limit of 5.8 × 10 −27 cm 6 atom −2 s −1 ( T = 900 K). The rate constant for the two body collisional quenching of Ba[6s5d( 3D J)] by ground state atomic strontium, Sr[5s 2( 1S 0)], is found to be (2.0 ± 0.1) × 10 −12 cm 3 atom −1 s −1 ( T = 900 K). 相似文献
7.
The evaporation of the species Ga 3+, In 3+, PO 3−4, AsO 3−4, Ga 3+/AsO 3−4, Ga 3+/PO 3−4 and In 3+/AsO 3−4 in HCl and HNO 3 medium was investigated by measurement of the non-specific absorption at 250 nm, in a graphite cuvette, with a continuum light source. The maximum of the non-specific absorption is given for the ashing and atomizing phases as a function of the ashing temperatures. Ashing temperatures for analytical determinations can be derived from the results. The mechanisms of evaporation of the substances were investigated by means of extinction-time curves. Absorption spectra of the matrices and of the pure acids used were measured between 190 and 330 nm in the graphite cuvette at different ashing and atomizing temperatures. The InCl- and GaCl-bands of the C-system and new bands of GaO- and InO-molecules were found. The PO-band at 246 nm was detected. The results are discussed and can be applied for thermal fractionation and for background correction by the two-line method in trace analysis by electrothermal AAS. 相似文献
8.
Two Schiff bases N, N′-(bis(pyridin-2-yl)benzylidene)propane-1,3-diamine (pbpd) and N, N′-(bis(pyridin-2-yl)formylidene)butane-1,4-diamine (pfbd) have been prepared and used to synthesize copper(II) complexes. Four complexes of the type [Cu(L)(N 3)]X (1–4) [L = pbpd; X = ClO 4 (1); L = pbpd; X = PF 6 (2); L = pfbd; X = ClO 4 (3); L = pfbd; X = PF 6 (4)] have been synthesized and characterized on the basis of microanalytical, spectroscopic, magnetic, electrochemical, luminescence and other physicochemical properties. Two representative complexes of the series, 2 and 3, have been characterized by single crystal X-ray diffraction measurements which reveal that in each complex the copper(II) ion assumes a distorted trigonal bipyramidal environment through coordination of the metal centre by two pyridine N atoms and two imine N atoms of the Schiff base with the fifth position occupied by a N atom of a terminal . They display intraligand 1(π–π *) fluorescence at room temperature and intraligand 3(π–π *) phosphorescence in glassy solutions (MeOH at 77 K). A band (492 nm) observed for the complexes in their solid-state emission spectra is an excimeric emission arising due to an aromatic π–π interaction. Electrochemical electron transfer study reveals Cu II–Cu I reduction in methanolic solutions. 相似文献
9.
Pulse radiolysis technique has been employed to study the reactions of oxidizing ( √OH, N 3√) and reducing radicals (e −aq, CO 2√−, acetone ketyl radical) with 2-hydroxy-3-methoxybenzaldehyde ( o-vanillin) at different pH. Hydroxyl radicals react mostly by addition reaction forming radical adducts (λ max=420 nm) and the oxidation is only a minor process even in the alkaline region. The reaction with azide radicals produced phenoxyl radicals (λ max=340 nm), which are formed on fast deprotonation of solute radical cation. Using PMZ √+/PMZ and ABTS √−/ABTS 2− as the reference couple, different methods are employed to determine the one-electron reduction potential of o-vanillin and the average value is estimated to be 1.076±0.004 V vs. NHE at pH 6. The phenoxyl radicals of o-vanillin were able to oxidize ABTS 2− quantitatively. The e aq− is observed to react with o-vanillin with rate constant value of 2×10 10 dm 3 mol −1 s −1. CO 2√− and acetone ketyl radical are also observed to react with o-vanillin by electron transfer mechanism and showed the formation of transient absorption bands with λ max at 350 and 390 nm at pH 4.5 and 9.7, respectively. The p Ka of the one-electron reduced species was determined to be 8.1. The results indicate that the aldehydic group is the most preferred site for electron addition. 相似文献
10.
A series of Ce xPr 1−xO 2−δ mixed oxides were synthesized by a sol–gel method and characterized by Raman, XRD and TPR techniques. The oxidation activity for CO, CH 3OH and CH 4 on these mixed oxides was investigated. When the value x was changed from 1.0 to 0.8, only a cubic phase CeO 2 was observed. The samples were greatly crystallized in the range of the value x from 0.99 to 0.80, which is due to the formation of solid solutions caused by the complete insertion of Pr into the CeO 2 crystal lattices. Raman bands at 465 and 1150 cm −1 in Ce xPr 1−xO 2−δ samples are attributed to the Raman active F 2g mode of CeO 2. The broad band at around 570 cm −1 in the region of 0.3 ≤ x ≤ 0.99 can be linked to oxygen vacancies. The new band at 195 cm −1 may be ascribed to the asymmetric vibration caused by the formation of oxygen vacancies. The TPR profile of Pr 6O 11 shows two reduction peaks and the reduction process is followed: . The reduction temperature of Ce xPr 1−xO 2−δ mixed oxides is lower than those of Pr 6O 11 or CeO 2. TPR results indicate that Ce xPr 1−xO 2−δ mixed oxides have higher redox properties because of the formation of Ce xPr 1−xO 2−δ solid solutions. The presence of the oxygen vacancies favors CO and CH 3OH oxidation, while the activity of CH 4 oxidation is mostly related to reduction temperatures and redox properties. 相似文献
11.
The use of ICP/AES for the determination of zinc, in low concentration levels, in matrices containing high levels of copper is difficult because copper interferes in the zinc main emission wavelength (213.856 nm). In the present work, a separation of zinc from copper matrices was possible, using the reaction of zinc(II) cation with 1-(2-tiazolylazo)-2-naphthol (TAN), in the pH range of 6.5–8.0, resulting in a stable red complex. Copper also reacts with TAN but its interference was avoided by the addition of ascorbic acid and thiosulphate in the reaction medium. In this way, the aqueous solution was passed through a SEP PAK C18 cartridge, in which the zinc(II)–TAN complex was quantitatively retained, but it did not occur with copper which passes through the cartridge, as [Cu 2(S 2O 3) 2] 2−, with the aqueous solution. The cartridge was washed with water and the complex eluted with ethanol. Then, the alcohol was evaporated and the complex decomposed by nitric acid. It results in both zinc pre-concentration and separation from copper. The zinc quantification was carried out by ICP/AES at 213.856 nm. The relative standard deviations, for ten different aliquots, were 5.7% and the average recovery found for zinc was 96%, even when the concentration ratio Cu/Zn was up to 500/1 (mg l −1:mg l −1). Other metals, like nickel, for example, can react with TAN in the same way as zinc but they do not interfere in the emission wavelength 213.856 nm. 相似文献
12.
The absorption, fluorescence and excitation fluorescence spectra dipyrido[3,4-b:2,3-d]-phenazine (DPPZ1) have been measured in non-polar and polar matrices at room temperature, and were taken into account to explain the origin of the relatively weak emission of this molecule in both type of environment. The electronic structure of DPPZ1 was calculated using a modified INDO CI method. The geometry optimization has been performed using the MNDO method. According to the spectra and the results of calculations, the lowest excited singlet state S 1 of DPPZ1 molecule is of n,π *-type and the next one, S 2 state, is of π,π *-type. The energy gap Δ Ecalc
is equal 4770 cm −1. The low efficiency of the emission observed in the hydroxylic solvent can be interpreted in terms of thermal quenching of the π,π *-type fluorescence. However, experimental results obtained suggest that in nonpolar solvents the emission of the molecule examined is an anomalous S 2→S 0 fluorescence. 相似文献
13.
A new uranium (III) fluoro-complex of the formula K 5Li 2UF 10 has been synthesised and characterised by X-ray powder diffraction and electronic absorption spectra measurements. The compound crystallises in the orthorhombic system, space group Pnma, with a = 20.723, b = 7.809, c = 6.932 Å, V = 1121.89 Å 3, Z = 4 and is isostructural with its K 5Li 2NdF 10 and K 5Li 2LaF 10 analogous. The absorption spectrum of a polycrystalline sample of K 5Li 2UF 10 was recorded at 4.2 K in the 3500–45,000 cm −1 range and is discussed. The observed crystal-field levels were assigned and fitted to parameters of the simplified angular overlap model (AOM) and next to those of a semi-empirical Hamiltonian, which was representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab initio calculations. The analysis of the spectra enabled the assignment of 71 crystal-field levels of U 3+ with a relatively small r.m.s. deviation of 37 cm −1. The total splitting of 714 cm −1 was calculated for the 4I 9/2 ground multiplet. 相似文献
14.
The infrared spectra of 3-pentyn-2-ol, CH 3CCCH(OH)CH 3, have been recorded as a vapour and liquid at ambient temperature, as a solid at 78 K in the 4000–50 cm −1 range and isolated in an argon matrix at ca. 5 K. Infrared spectra of the solid phase at 78 K were obtained before and after annealing to temperatures of 120 and 130 K. The IR spectra of the solid were quite similar to that of the liquid. Raman spectra of the liquid were recorded at room temperature and at various temperatures between 295 and 153 K. Spectra of an amorphous and annealed solid were recorded at 78 K. In the variable temperature Raman spectra, some bands changed in relative intensity and were interpreted in terms of conformational equilibria between the three possible conformers. Complete assignments were made for all the bands of the most stable conformer in which OH is oriented anti to C1(aMe). From various bands assigned to a second conformer in which OH is oriented anti to Hgem(aH), the conformational enthalpy differences was found to be between 0.4 and 0.8 kJ mol−1. The highest energy conformer with OH anti to C3(aC) was not detected. Quantum-chemical calculations have been carried out at the MP2 and B3LYP levels with a variety of basis sets. Except for small basis set calculations for which the aH conformer had slightly lower energy, all the calculations revealed that aMe was the low energy conformer. The B3LYP/cc-pVTZ calculations suggested the aMe conformer as more stable by 0.8 and 8.3 kJ mol−1 relative to aH an aC, respectively. Vibrational wavenumbers and infrared and Raman band intensities for two of the three conformers are reported from B3LYP/cc-pVTZ calculations. 相似文献
15.
The objective of this study was to investigate the retention of phosphate anions, H 2PO 4− and HPO 42−, by nanofiltration. The first part of this study deals with the characterisation of the NF200 membrane used in permeation experiments with aqueous solutions of neutral organic and charged inorganic solutes. In the second part the effects of feed pressure, ionic strength, concentration and pH on the retention of phosphate anions were investigated. Results show that the membrane is negatively charged, its pore radius is around 0.5 nm and the retention order for the salts tested was R(Na 2SO 4) > R(NaCl) > R(CaCl 2). The retentions of phosphate anions are in the order of 85% for H 2PO 4− and 96% for HPO 42−. They are relatively high when compared to retentions of other anions with the same charge. The retentions of phosphate anions, particularly the monovalent species, depend on the chemical parameters (feed concentration, ionic strength, and pH) and applied pressure. The experimental data were analysed using the Speigler–Kedem model and the transport parameters, i.e., the reflection coefficient ( σ) and solute permeability ( Ps) have been determined. 相似文献
16.
Raman spectra were measured of highly fluorinated graphite samples prepared at room temperature, 380 and 515 °C. C xF prepared at room temperature showed a novel downshifted band at 1555–1542 cm −1 along with G band at 1593–1583 cm −1. Similar behavior is also observed for samples prepared at 380 and 515 °C at early stages of fluorination, after which the Raman shifts completely disappeared. Raman spectra as well as X-ray diffraction (XRD) analysis suggest that graphite fluorides, (CF) n and (C 2F) n are formed via fluorine-intercalated phase with planar graphene layers. 相似文献
17.
The importance of atmospheric hydrogen peroxide (H 2O 2) in the oxidation of SO 2 and other compounds has been well established. A spectrophotometric method for the determination of hydrogen peroxide in rainwater is proposed. This method is based on selective oxidation of hydrogen peroxide using an on-line tubular reactor containing peroxidase immobilized on Amberlite IRA-743 resin. The hydrogen peroxide in the presence of phenol, 4-aminoantipyrine and peroxidase, produces a red compound ( λ = 505 nm). Beer's law is obeyed in a concentration range of 1–100 μmol l −1 hydrogen peroxide with an excellent correlation coefficient ( r = 0.9991), at pH 7.0, with a relative standard deviation (R.S.D.) <2%. The detection limit of the method is 0.7 μmol l −1 (4.8 ng of H 2O 2 in a 200 μl sample). Measurements of hydrogen peroxide in rain samples were carried out over the period from November 2003 to January 2005, in the central area of the Juiz de Fora city, Brazil. The concentration of H 2O 2 varied from values lower than the detection limit to 92.5 μmol l −1. The effects of the presence of nonseasalt (NSS) SO 42−, NO 3− and H + in the concentration of hydrogen peroxide in the rainwater had been evaluated. The average concentrations of H 2O 2, NO 3−, NSS SO 42− and SO 42− are 23.4, 18.9, 7.9 and 10.3 μmol l −1, respectively. The pH values for 82% of the collected samples are greater than 5.0. The spectrophotometeric method developed in this work that uses enzyme immobilized on the resin ion-exchange compared with the amperometric method did not present any significant difference in the results. 相似文献
18.
The one-electron oxidation of Mitomycin C (MMC) as well as the formation of the corresponding peroxyl radicals were investigated by both steady-state and pulse radiolysis. The steady-state MMC-radiolysis by OH-attack followed at both absorption bands showed different yields: at 218 nm G i (-MMC) = 3.0 and at 364 nm G i (-MMC) = 3.9, indicating the formation of various not yet identified products, among which ammonia was determined, G(NH 3) = 0.81. By means of pulse radiolysis it was established a total κ (OH + MMC) = (5.8 ± 0.2) × 10 9 dm 3 mol −1 s −1. The transient absorption spectrum from the one-electron oxidized MMC showed absorption maxima at 295 nm (ε = 9950 dm 3 mol −1 cm t-1), 410 nm (ε = 1450 dm 3 mol −1 cm −1) and 505 nm ( ε = 5420 dm 3 mol −1 cm −1). At 280–320 and 505 nm and above they exhibit in the first 150 μs a first order decay, κ 1 = (0.85 ± 0.1) × 10 3 s −1, and followed upto ms time range, by a second order decay, 2κ = (1.3 ± 0.3) × 10 8 dm 3 mol -1 s −1. Around 410 nm the kinetics are rather mixed and could not be resolved. The steady-state MMC-radiolysis in the presence of oxygen featured a proportionality towards the absorbed dose for both MMC-absorption bands, resulting in a Gi (-MMC) = 1.5. Among several products ammonia-yield was determined G(NH3) = 0.52. The formation of MMC-peroxyl radicals was studied by pulse radiolysis, likewise in neutral aqueous solution, but saturated with a gas mixture of 80% N2O and 20% O2. The maxima of the observed transient spectrum are slightly shifted compared to that of the one-electron oxidized MMC-species, namely: 290 nm (ε = 10100 dm3 mol−1 cm−1), 410 nm (ε = 2900 dm3 mol−1 cm−1) and 520 nm (ε = 5500 dm3 mol−1 cm−1). The O2-addition to the MMC-one-electron oxidized transients was found to be at 290 to 410 nm gk(MMC·OH + O2) = 5 × 107 dm3 mol−1 s−1, around 480 nm κ = 1.6 × 108 dm3 mol−1 s−1 and at 510 nm and above, κ = 3 × 108 dm3 mol−1 s−1. The decay kinetics of the MMC-peroxyl radicals were also found to be different at the various absorption bands, but predominantly of first order; at 290–420 nm κ1 = 1.5 × 103 s−1 and at 500 nm and above, κ = 7.0 × 103 s−1. The presented results are of interest for the radiation behaviour of MMC as well as for its application as an antitumor drug in the combined radiation-chemotherapy of patients. 相似文献
19.
A series of γ-Al 2O 3 samples modified with various contents of sulfate (0–15 wt.%) and calcined at different temperatures (350–750 °C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al 2O 3 methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO 42−/γ-Al 2O 3 for methanol dehydration increased significantly when the content of sulfate increased to 10 wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO 42−/γ-Al 2O 3 was further increased to 15 wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO 2. On the other hand, when the calcination temperature of SO 42−/γ-Al 2O 3 increased from 350 °C to 550 °C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO 2. Nevertheless, a further increase in calcination temperature to 750 °C remarkably decreased the catalytic activity of SO 42−/γ-Al 2O 3 for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO 42−/γ-Al 2O 3 with 10 wt.% sulfate and calcined at 550 °C exhibited the highest selectivity and yield for the synthesis of DME. 相似文献
20.
The three cyanocuprate(I) complexes, Cu(CN) 2−, Cu(CN) 32−, and Cu(CN) 43−, photoeject electrons with high efficiency when excited in aqueous solution by 266 nm laser pulses of 7 ns duration with quantum yields of 0.37±0.06, 0.224±0.021, and 0.240±0.005, for Cu(CN) 2− (at 2 M ionic strength), Cu(CN) 32−, and Cu(CN) 43− (both measured at 1 M ionic strength). Along with hydrated electrons, two transient intermediates, absorbing at 460 and 340 nm, respectively, form consecutively after excitation through bimolecular reactions with ground-state Cu(I) in solutions of Cu(CN) 2−, and Cu(CN) 32−, but not in Cu(CN) 43−. All photoprocesses are essentially monophotonic. A mechanism is proposed that suggests the formation of a dinuclear excited-state complex such as an excimer. 相似文献
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