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1.
Tungsten oxide nanoparticles were fabricated by a pulsed laser ablation method in deionized water using the first harmonic of a Nd:YAG laser ( λ=1064 nm) at three different laser pulse energies (E1 =160, E2 =370 and E3 =500 mJ/pulse), respectively. The aim is to investigate the effect of laser pulse energy on the size distribution and gasochromic property of colloidal nanoparticles. The products were characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The results indicated that WO 3 nanoparticles were formed. After ablation, a 0.2 g/l PdCl 2 solution was added to activate the solution against hydrogen gas. In this process Pd 2+ ions were reduced to deposit fine metallic Pd particles on the surface of tungsten oxide nanoparticles. The gasochromic response was measured by H 2 and O 2 gases bubbling into the produced colloidal Pd–WO 3. The results indicate that the number of unreduced ions (Pd 2+) decreases with increasing laser pulse energy; therefore, for colloidal nanoparticles synthesized at the highest laser pulse energy approximately all Pd 2+ ions have been reduced. Hence, the gasochromic response for this sample is nearly reversible in all cycles, whereas those due to other samples are not reversible in the first cycle. 相似文献
2.
Binary Au-Pd nanoparticles were synthesized by ultrasonic irradiation of solutions containing Au 3+ and Pd 2+ ions (the ion ratio from 0.3:0.7 to 0.9:0.1 mM) and cationic surfactant (SDS: sodium dodecyl sulfate). In each case the core-shell structure (Au core, Pd shell) was confirmed by scanning transmission electron microscopy (STEM). The mean diameters of them were all about 9 nm, and the thickness of the Pd shell depends on the ratio of Pd 2+ and Au 3+ ions in solution. In order to study the electronic states of core-shell nanoparticles and their dependence on shell thickness, Doppler broadening measurements were performed for Au-Pd core-shell nanoparticles by using slow positron beam technique. The ratio curves of Au-Pd particles did not match with those of pure Pd and pure Au, but a small difference in the low electron momentum region was observed among nanoparticles depending on Pd shell thickness. 相似文献
3.
The acyclic tridentate blue luminescent ligand ( λex=300 nm, λem=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd 2+. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd 2+ that was further reflected in the solid phase fluorescence microscopic study.Ligand formed 1:1 complexes with Ni 2+, Cu 2+, Zn 2+, Pd 2+ and 1:2 complexes with Co 2+, Fe 2+ as obtained from Job's plot of continuous variation. The binding constants of different metal complexes (Fe 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+ and Pd 2+) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd 2+ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd 2+ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu 2+ and Zn 2+ and 100-fold excess addition of Co 2+, Fe 2+ and Ni 2+over the Pd 2+ ion concentration (1.0×10 −3 M). 相似文献
4.
Microcrystalline cellulose is a porous natural material which
can be used both as a support for nanoparticles and as a reducer of metal ions.
Cellulose supported nanoparticles can act as catalysts in many reactions.
Cu, CuO, and Cu 2O particles were prepared in microcrystalline cellulose
by adding a solution of copper salt
to the insoluble cellulose matrix and by reducing the copper ions
with several reducers.
The porous nanocomposites were studied using anomalous small angle X-ray
scattering (ASAXS), X-ray absorption spectroscopy, and X-ray diffraction.
Reduction of Cu 2+ with cellulose in ammonium hydrate medium
yielded crystalline CuO nanoparticles and
the crystallite size was about 6–20 nm irrespective of
the copper concentration. The size distribution of the CuO particles
was determined with ASAXS measurements and
coincided with the crystallite sizes.
Using sodium borohydrate or hydrazine sulfate as a reducer
both metallic Cu and Cu 2O nanoparticles
were obtained and the crystallite size and the oxidation state
depended on the amount of reducer. 相似文献
5.
Pd and Fe exchanged NaX and NaZSM-5 catalysts (Pd/Fe=5) were studied. The components formed in the course of hydrogen activation
at 720 K and their transformations taking place during treatments in CO+H 2 at 570 and 500 K are described. Pd xFe, Fe 2+ ions in octahedral and tetrahedral environments and x-iron carbide components are identified. The bimetallic component is
not affected by the CO+H 2 treatment. The Fe 2+ ions located only in tetrahedral environment were transformed into iron carbide in the X zeolite framework, while the Fe 2+ ions of octahedral environment were also transformed in part to carbide in the ZSM-5 lattice. 相似文献
6.
This paper reports on parallel EPR studies of high-temperature superconductors based on the cuprate perovskites RBa 2Cu 3O 6+x ( R=Y, Gd, Nd) and of KTaO 3: Cu, which also has a perovskite structure. EPR measurements performed on copper-doped KTaO 3 crystals revealed Cu 2+-Cu 2+ copper pair centers. The copper ions making up pairs are assumed to occupy adjacent tantalum sites. The pair centers are chains consisting of two equivalent Cu 2+ ions and three oxygen vacancies aligned in the 〈100〉 direction. The crucial point in the model proposed is the presence of an oxygen vacancy sandwiched between two Cu 2+ ions, whereas the outer vacancies do not necessarily occupy neighboring sites. In this structure, complete charge compensation is achieved. Ferromagnetic exchange coupling takes place between the two copper ions. An investigation of the exchange and superhyperfine interactions of copper centers in crystalline potassium tantalate has permitted the estimation of the respective interactions in crystals of the cuprate superconductors which exhibit magnetic resonance signals due to exchange-coupled copper clusters in the case of oxygen deficiency. 相似文献
7.
The spectrum of standing spin waves has been detected by the ferromagnetic resonance method in NiFe(740 Å)/Cu/NiFe(740 Å) three-layered film structure in the perpendicular configuration for the copper thickness d Cu ≤ 30 Å. At thicknesses d Cu > 30 Å, the resonance absorption curve is a superposition of two spinwave resonance spectra from individual ferromagnetic NiFe layers. For Co/Pd multilayer films, united spinwave responance spectra have also been observed at thicknesses of the paramagnetic palladium layer up to d Pd < 30 Å. The partial exchange stiffness has been calculated for a spin wave propagating across the Pd layer ( A Pd = 0.1 × 10 ?6 erg/cm). This value is always positive (up to the critical thickness of the palladium interlayer d Pd < d c) or equal to zero ( d Pd > d c). 相似文献
8.
The results of EPR and magnetic susceptibility studies on xCuO·(1? x)? [2 B2O3· Li2O] glasses with , are reported. The modification of EPR spectra with the increasing of CuO content are explained supposing that these are the result of the superposition of two EPR signals, one showing the hyperfine structure typical for isolated Cu 2+ ions and other consisting from a broad line centered at g ~ 2 typical for the clustered Cu 2+ ions. The values of the EPR parameters prove that the coordination of isolated Cu 2+ -complexes remains approximately the same and show that Cu 2+ ions are situated in axially distorted octahedral vicinities. EPR measurements have shown that the Cu 2+ ions are present mostly as the isolated species when . Beside the dipole-dipole coupling between Cu 2+ ions, the magnetic measurements suggest that for x>10 mol % superexchange interactions appear, too. From Curie constant is established that in this glass system the copper ions are in Cu 2+ and Cu + valence states. Also, the amounts of the copper ions in bivalent state are determined. 相似文献
9.
A simple uracil-appended fluorescent sensor (1) has been developed by one pot reaction and characterized by using common spectroscopic methods such as UV-vis, Fluorescence, HRMS and FT-IR analyses. Upon addition of various metal ions to the CH3CN solution of sensor 1, the fluorescence was quenched in the presence of Cu2+ / Hg2+ ions. The limit of detection for Cu2+ and Hg2+ was calculated to be 3.31 and 0.316 µM, respectively. Further, the sensor was applied for real-life applications in the determination of Vitamin B2 (riboflavin) and its presence in milk products. With the incorporation of different sources of vitamin-B to acetonitrile solution of it, there was discernible fluorescence enhancement only in the presence of vitamin B2. Also, it has been successfully applied for the detection of Vitamin B2 (riboflavin) in milk and curd. Moreover, based on the fluorescent color changes, the sensor was utilized for invisible ink applications. 相似文献
10.
Silica glass was implanted with 50 keV Cu + ions at various fluences from 6×10 15 to 8×10 16 ions/cm 2 and thermally-annealed in air between room temperature to 1200 °C. UV/visible spectroscopy measurements reveal absorption bands at characteristics surface plasmon resonance (SPR) frequencies, signifying the formation of copper colloids in silica, even without thermal treatments. Such copper nanoclusters can be attributed to the relatively high mobility of copper atoms, even at ambient conditions. Using the equation derived from the framework of free-electron theory, the average radii of the Cu particles were found to be in the range 2-4 nm from the experimental surface plasmon absorption peaks. Radioluminescence (RL) spectra exhibited broad bands at 410 and 530 nm, associated with the presence of Cu + ions in the as-implanted samples. The effect of thermal annealing in air on absorption and emission spectra of these Cu-implanted samples, as well as the formation of copper nanoclusters from original Cu + ions, is discussed. 相似文献
11.
The equilibrium and photoinduced absorption spectra of copper-and silver-doped Bi 12SiO 20 crystals are studied. It is demonstrated that the impurity absorption is due to Ag 2+, Ag +, Cu 3+, Cu 2+, and Cu + ions occupying almost octahedral Bi 3 positions. A mechanism of photochromism is suggested, involving changes in the charge states of copper and silver impurity ions according to schemes Cu 2+- e → Cu 3+ and Ag +- e → Ag 2+. 相似文献
12.
A trace amount (0.5 mol%) of CuO-doped 40Li 2O–32Nb 2O 5–28SiO 2 glass (mol%) exhibits the formation of copper metal layers at the glass surface by annealing at temperatures (530 °C) below the glass transition temperature (544 °C) in the reduced atmosphere of 7% H 2–93%Ar. The coordination state of copper ions is examined from optical absorption and Fourier transform infrared (FT-IR) spectrum measurements, indicating the formation of Si–OH and Si–H bonds due to the diffusion of hydrogen into the inside of the glass and the reduction of Cu + and Cu 2+ ions. The mechanism of the formation of copper metals at the surface is proposed, in which the key points are the reduction of Cu 2+ to Cu + ions due to the hydrogen and the migration of Cu + ions in the interior of the glass to the surface. The first finding on copper metal layers at the glass surface might have a potential for practical applications such as electrodes in glass. 相似文献
13.
The duplex oxide film potentiostatically formed on copper in concentrated alkaline media has been investigated by XRD, XPS, negative-going voltammetry and cathodic chronopotentiometry. The interfacial capacity was also measured using fast triangular voltage method under quasi-stationary condition. The obvious differences in the thickness, composition, passivation degree and capacitance behavior were observed between the duplex film formed in lower potential region (−0.13 to 0.18 V versus Hg|HgO electrode with the same solution as the electrolyte) and that formed in higher potential region (0.18-0.60 V). Cuprous oxides could be formed and exist stably in the inner layer in the both potential regions, and three cupric species, soluble ions and Cu(OH) 2 and CuO, could be independently produced from the direct oxidation of metal copper, as indicated by three pairs of redox voltammetric peaks. One of the oxidation peaks appeared only after the scan was reversed from high potential and could be attributed to CuO formation upon the pre-accumulation of O 2− ions within the film under high anodic potentials. A new mechanism for the film growth on the investigated time scale from 1 to 30 min is proposed, that is, the growth of the duplex film in the lower potential region takes place at the film|solution interface to form a thick Cu(OH) 2 outer layer by field-assisted transfer of Cu 2+ ions through the film to solution, whereas the film in the higher potential region grows depressingly and slowly at the metal|film interface to form Cu 2O and less CuO by the transfer of O 2− ions through the film to electrode. 相似文献
14.
The effect of laser irradiation using three different wavelengths (IR, visible and UV) generated from Nd:YAG laser on the local glass structure as well as on the valence state of the copper ions in copper phosphate glass containing CuO with the nominal composition 0.30(CuO)-(0.70)(P 2O 5), has been investigated by X-ray photoelectron spectroscopy (XPS). The presence of asymmetry and satellite peaks in the Cu 2p spectrum for the unirradiated sample is an indication of the presence of two different valence states, Cu 2+ and Cu +. Hence, the Cu 2p 3/2 spectrum was fitted to two Gaussian-Lorentzian peaks and the corresponding ratio, Cu 2+/Cu total, determined from these relative areas clearly shows that copper ions exist predominately (>86%) in the Cu 2+ state for the unirradiated glass sample under investigation. For the irradiated samples the symmetry and the absence of satellite peaks in the Cu 2p spectra indicate the existence of the copper ions mostly in Cu + state. The O 1s spectra show slight asymmetry for the irradiated as well as unirradiated glass samples which result from two contributions, one from the presence of oxygen atoms in the P-O-P environment (bridging oxygen BO) and the other from oxygen in an P-O-Cu and PO environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with laser power. 相似文献
15.
The Cu + ion solid electrolyte 47Cu Br·3(CH 3) 2 C 6H 12N 2Br 2 was prepared by hot-pressing and characterised by X-ray analysis and electrical measurements. Novel cell arrangements were used to study the electrochemical behaviour of interfaces between this electrolyte and copper metal and also between this electrolyte and two well known solid solution electrodes (SSEs) for copper, Cu 2Mo 6S 7.59 and Cu 1.8S. The behaviour of the electrolyte/copper interface was correlated with scanning electron microscope (SEM) examinations showing the growth of copper dendrites at the interface. Results from the electrolyte/SSE interfaces showed that there is no interfacial polarisation and that the electrode polarisation is controlled solely by the diffusion of Cu + ions in the SSE. These experiments allowed estimates of the chemical diffusion coefficient for Cu + ions in each material to be made. 相似文献
16.
The electron paramagnetic resonance (EPR) and dielectric properties of Pb 5Ge 3O 11 crystals activated by copper ion are investigated. It is shown that Cu 2+ ions replace Pb 2+ in trigonal symmetry positions and occupy three off-center positions displaced from a crystal lattice site in a plane perpendicular to the polar axis C. The temperature variation of EPR spectra and dielectric properties indicates the presence of thermally activated jumps of Cu 2+ ions between off-center positions. The EPR and dielectric data are used to determine the activation energy W=0.24 eV and the eigenfrequency τ 0 ?1 ~ 10 12 Hz of local dynamics of Cu 2+ ions. 相似文献
17.
ESR spectra of Cu 2+ in LiKSO 4 have been studied at different temperatures. The measured g-values suggest a rhombic field for Cu 2+ ion in the lattice. Optical absorption spectra of the crystal have been studied at room and liquid nitrogen temperatures. From the nature and position of the observed bands, they have been attributed to Cu 2+ ions in D 2h symmetry. The orbital reduction parameters obtained indicate a substantial degree of covalency in the bonding of the copper ion. 相似文献
18.
The cyclohexane solution of TTA (trifluorothenoyl-acetone), phen (8-hydroxylquinoline) and PS (polystyrene), the ethyl acetate solution of TTA, phen and PMMA (polymethyl methacrylate) were used as flowing liquid, the coordinated Eu 2O 3/polymer hybrid colloids were successively produced by focused pulsed laser ablation of Eu 2O 3 target in interface of solid and flowing liquid. As solvent in the hybrid colloids has volatilized, the coordinated Eu 2O 3/polymer hybrid films were obtained. The hybrid colloids and films were characterized by TEM, UV-vis spectrum, fluorescence spectrum, TG-FTIR and X-ray photoelectron spectrum. The results show the coordinated Eu 2O 3 nanoparticles with average size of less than 20 nm are surrounded by the three-dimensional network and are properly incorporated into the PMMA and PS matrix, the hybrid films can emit intense red light under ultraviolet radiation, and their emission fluorescence spectra display same characteristic emission peaks of Eu 3+ ions. The Eu 2O 3 hybrid films have better thermo stability than the related pure polymers because of strong interaction between surface europium ions of the nanoparticles and polymer. Because the coordinated Eu 2O 3 nanoparticles were wrapped by polymer, they have higher chemical stability than the related europium complex. 相似文献
19.
In the article, the Co/Pd/TiO 2, Co/TiO 2 and Pd/TiO 2 catalysts prepared by the impregnation and sol–gel method are studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The result shows that Co 2+ and metal Pd may act as the active center for the direct synthesis of acetic acid from CH 4 and CO 2 by a two-step reaction sequence. When the catalysts are prepared by the sol–gel, Co 2+ can enter the crystal lattice of the TiO 2, causing the phase transition from anatase to rutile at lower temperature, but existence of Pd 2+ can prevent from the phase transition. When the catalysts are prepared by the impregnation, the phase transition is inhibited not only Co 2+ but also Pd 2+. 相似文献
20.
The effect of atomic disordering and alloying with d elements (Fe, Pd, Cu) on the transport and magnetic properties of Cu 3Pd alloys has been investigated at low temperatures ( T < 80 K) in strong magnetic fields ( H ≤ 8 MA/m). The specific features of the crystal structure and temperature and field dependences of the electrical resistance, magnetoresistance, Hall effect, and magnetic susceptibility of Cu 72Pd 28, Cu 75Pd 25, Cu 80Pd 20 and Cu 74.5Pd 24.5Fe 1 alloys are discussed. 相似文献
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