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1.
The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff’s base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H2L) and its metal complexes with Zn2+, Cu2+ and Ag+ ions. This study aims to investigate the behavior of H2L and the binuclear Zn2+ complex (1) as fluorescent probes for the detection of metal ions (Zn2+, Cu2+ and Ag+) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H2L ligand were optimized using the B3LYP/6–311?+??+?G** level of theory, while the L?2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6–311?+??+?G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6–311?+??+?G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn2+, Cu2+ and Ag+). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag+ and Cu2+ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch “On–Off-On” via the replacement of Cu2+ by Ag+ ions, as proved experimentally. 相似文献
2.
Arrays of Ag/Cu alloy nanowires embedded in anodic alumina membranes (AAMs) were synthesized by directly electrodepositing from a mixing electrolyte solution containing Ag + and Cu 2+ ions. Manipulations of optical properties of the resulting samples were successfully achieved by tuning the molar ratio of Ag + and Cu 2+ ions in the starting materials. When the ratio is less than 2:20, two surface plasma resonance (SPR) peaks corresponding to Ag and Cu appear, respectively. After annealing treatment, the SPR peak corresponding to Cu disappears, and that of Ag presents a red shift. Furthermore, this red shift can be up to 85 nm when the molar ratio of Ag + and Cu 2+ reduce to 1:20, which is attributed to the transferable electrons from Cu atoms. 相似文献
3.
Facial synthesis of cuprous oxide (Cu 2O) nanowires by directly heating copper substrates is difficult; however, in this study, it was successfully done by thermal oxidation followed by a plasma reduction process. The preparation of CuO nanowires with an average diameter of 76.2?nm supported on the surface of copper substrate was conducted first in air at 500?°C for 3?hrs, and then the CuO nanowires were reduced into Cu 2O in 15?min using either radio frequency (RF) N 2 plasma or microwave (MW) N 2 plasma. The characteristics of CuO and Cu 2O nanowires were analyzed using XRD, FE-SEM, and TEM. The results showed that Cu 2O nanowires can be successfully reduced from CuO nanowires by a simple, promising, and fast nitrogen plasma process. Moreover, in RF plasma, narrower and longer Cu 2O nanowires can be produced as compared to MW plasma, because energetic N-containing species can reduce the nanowires at a relatively lower temperature. 相似文献
4.
We grew Cu 2S nanowires vertically on Cu foil by gas–solid reaction with a gas mixture of O 2 and H 2S. The electrical contact properties between the Cu 2S nanowires and Cu foil were investigated using a modified current–voltage–temperature plot. The Cu/Cu 2S layer exhibited the characteristics of a Schottky barrier with a barrier height of ∼0.72 eV, which was closer to the value for Cu/Cu 2O than to Cu/Cu 2S. Energy dispersive spectroscopy results showed the presence of Cu-oxide between the Cu 2S nanowires and Cu foil. The overall structure was Cu/Cu-oxide/Cu 2S and the electrical properties were controlled by the Cu/Cu-oxide. 相似文献
5.
The absorption spectra of thin films of ( MI) 1 ? y (Ag 1 ? x Cu xI) y solid solutions ( M = Rb, Cs) with the initial molar concentration y = 0.33 have been investigated. It is established that, at low concentrations x, a local exciton band due to Cu + ions is split off from the main long-wavelength exciton bands. In Rb 2Ag 1 ? x Cu xI 3 solutions, the concentration shift of exciton bands indicates the formation of a persistent-type exciton spectrum. However, in Rb 2Ag 1 ? x Cu xI 3 with x ≥ 0.5 and in Cs 2Ag 1 ? x Cu xI 3 with x > 0.2, exciton spectra of amalgamation type are observed, which are related to the formation of more stable M 3Ag 2 ? 2x Cu 2x I 5 solid solutions. The formation of these solutions leads to broadening of the exciton bands and to the concentration transition from persistent-to amalgamation-type exciton spectra. 相似文献
6.
Environmentally friendly Cu 2?x S compounds exist in many different mixed phases in nature, while their nanoscale counterparts can be pure phase with interesting localized surface plasmon resonance properties. Because of the complexity of composition and phase, controllable synthesis of Cu 2?x S nanocrystals becomes an important scientific issue in colloidal chemistry. In this work, a hot‐injection method is developed to synthesize Cu 2?x S nanocrystals by injecting a sulfur precursor into a copper precursor using oleylamine and octadecene as solvents. By varying the reaction parameters (temperature, volume ratio of oleylamine/octadecene, molar ratio of Cu/S in the precursors), hexagonal CuS, monoclinic Cu 1.75S, and rhombohedral Cu 1.8S, nanocrystals can be selectively synthesized, providing a platform to illustrate the mechanism of crystal phase control. The crystal phase control of Cu 2?x S nanocrystals is oleylamine‐determined by controlling the molar ratio of Cu/S in the reaction precursors as well as the ratio of Cu 2?x S clusters/Cu + in the subsequent reaction. More importantly, temperature plays an important role in varying the molar ratio of Cu/S and Cu 2?x S clusters/Cu + in the reaction system, which significantly influences the crystal phase of the resulting Cu 2?x S nanocrystals. The understanding into crystal control provides a guideline to realize reproducible phase‐selective synthesis and obtain well‐defined high‐quality materials with precise control. 相似文献
7.
A new pyrene derivative (chemosensor 1) containing a picolinohydrazide moiety exhibits high selectivity for Cu 2+ ion detection in mixed aqueous media (CH 3OH:H 2O = 7:3). Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu 2+. However, the metal ions Ag +, Ca 2+, Cd 2+, Co 2+, Cu 2+, Fe 2+, Fe 3+, Hg 2+, K +, Mg 2+, Mn 2+, Ni 2+, Pb 2+, and Zn 2+ produced only minor changes in fluorescence for the system. The apparent association constant ( K
a) of Cu 2+ binding in chemosensor 1 was found to be 2.75*10 3 M −1. The maximum fluorescence enhancement caused by Cu 2+ binding in chemosensor 1 was observed over the pH range 5–8. Moreover, by means of fluorescence microscopy experiments, it is demonstrated that 1 can be used as a fluorescent probe for detecting Cu 2+ in living cells. 相似文献
8.
Self‐assembly of metal nanoclusters into 3D ordered superstructures and the exploration of their electrochemical properties are highly significant for fundamental research and practical application. In this study, atomically precise Ag 6(NALC) 5 nanoclusters are successfully synthesized and their structure is determined carefully. It is interesting that the prepared Ag 6(NALC) 5 nanoclusters can be self‐assembled into ultrafine nanowires, long ribbons, and finally 3D porous network in the mixed solution of water and ethanol, which can be attributed to the solvent polarity, static electricity interaction between ligands, and the possible Van der Waals attractions. Such assembly phenomenon lays a foundation for the future fabrication of silver clusters‐based nanodevices. In addition, the synthesized silver nanoclusters can be used for electrochemical sensing of glucose with high detection sensitivity, selectivity, and low limit of detection. This work is expected to be helpful for the synthesis of atomically precise metal nanoclusters and their applications in fabrication of nanodevices for chemical sensors. 相似文献
9.
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
10.
Canonical ensemble Monte Carlo simulations are applied to investigate the
melting of the icosahedral 55-atom Ag-Cu-Au clusters. The clusters are
modeled by the second-moment approximation of the tight-binding (TB-SMA)
many-body potentials. Results show that the introduction of the only Cu atom
of the third alloying metal in the bimetallic Ag 43Au 12 cluster,
forming the Ag 42Cu 1Au 12 cluster, can greatly increase the
melting point of the cluster by about 100 K. It is also found that the
substitution of the only Cu atom of the third alloying metal in the
Ag 1Au 54 clusters, forming the Ag 1Cu 1Au 53 cluster,
can result in an increase of 40 K in the melting point. It can be concluded
that the melting points of the bimetallic clusters can be tuned by the third
metal impurities doping. In addition, the surface segregation of Ag atoms in
the Ag-Cu-Au trimetallic clusters occurs even after melting. 相似文献
11.
The surface electric property of Cu 2O microcrystal affects the interaction of facets with substance in the aqueous solution, and hence plays a key role in determining the photocatalytic activity. In this paper, the capability of Cu 2O microcrystals with exclusive {111}, {110} or both lattice surfaces in reducing Ag + to Ag 0 were investigated. Ag particles selectively deposited on {111} surfaces of Cu 2O, while not on {110} surfaces. The different behaviors of the two surfaces are mainly attributed to their different electric properties: negatively-charged {111} surfaces absorb Ag + ions while positively-charged {110} surfaces repel them. Raman scattering of Cu 2O {111} surfaces was enhanced by the photo-deposition of Ag particles. 相似文献
12.
M 2Mn 3O 8 (M = Ca 2+, Cu 2+) compounds were synthesized and characterized in lithium cells. The M 2+ cations, which reside in the van der Waals gaps between adjacent sheets of Mn 3O 84−, may be replaced chemically (by ion-exchange) or electrochemically with Li. More than 7 Li +/Cu 2Mn 3O 8 may be inserted electrochemically, with concomitant reduction of Cu 2+ to Cu metal, but less Li can be inserted into Ca 2Mn 3O 8. In the case of Cu 2+, this process is partially reversible when the cell is charged above 3.5 V vs. Li, but intercalation of Cu + rather than Cu 2+ and Li +/Cu + exchange occurs during the subsequent discharge. If the cell potential is kept below 3.4 V, the Li in excess of 4 Li +/Cu 2Mn 3O 8 can be cycled reversibly. The unusual mobility of + 2 cations in a layered structure has important implications both for the design of cathodes for Li batteries and for new systems that could be based on M 2+ intercalation compounds. 相似文献
13.
(Ag 2) xCu 1?xS, x = .2, .4, .6 and .8 nanoparticles were synthesized by the solvothermal method. The as-synthesized nanoparticles were characterized by X-ray diffraction to study the crystal structure and size. The surface morphologies of the above samples were studied using scanning electron microscope. As there is continuous shift in the lower wavelength absorption edge of the UV–VIS spectrum of these samples with concentration, (Ag 2) xCu 1?xS nanoparticles can be tuned to different band gap energies by varying the composition. The D.C. electrical resistance was measured in the temperature range 310–485 K. As Ag 2S transforms from monoclinic to bcc at around 450 K, copper sulfide nanoparticles also shows a phase transition at around 470 K, the effects of these two transitions are seen in the resistance measurements and in the UV–VIS spectra of the entire system. The electrical resistance of (Ag 2) xCu 1?xS nanoparticles rapidly reduces as more and more copper sulfide is added. 相似文献
14.
Cu 7PSe 6 is a mixed conductor that crystallizes in the simple cubic structure at room temperature. Structural transitions above and below room temperature are accompanied by step-like changes in electrical conductivity. The substitution of Ag + for Cu + in Cu 7PSe 6 stabilized the simple cubic structure over a wider range of temperatures than is observed for the pure compound. A disproportionate decrease in electrical conductivity accompanies modest levels of silver substitution. The prominent step in electrical conductivity associated with the low-temperature crystallographic phase transition disappears in (Ag xCu 1−x) 7PSe 6 solid solutions for a composition parameter x=0.20, replaced by two distinct changes in the slope of conductivity below room temperature. 相似文献
15.
Ionic motion in superionic conductors, Ag 2S, Ag 2Se and Ag 3SI was investigated by γ-γ PAC on 111Cd. Diffusion constant measurements showed that probe ions migrate almost as fast as Ag + ions above 500K in Ag 2S and Ag 2Se and above 700K in Ag 3SI. Multivalent impurities were found to be unstable in AgI and Ag 2Te. The correlation time of ionic motion was deduced from the observed relaxation rate together with the diffusion constants. The correlation time and its activation energy increase in order of Ag 2S, Ag 2Se and Ag 3SI.The flight distance of Ag + ions remains almost constant in the measured temperature range. 相似文献
16.
CoCu alloy nanowire arrays embedded in anodic alumina template were fabricated by ac pulse electrodeposition. Different off-times between pulses in an electrolyte with constant concentration of Co +2 and Cu +2 and acidity of 4 were employed. The effect of deposition parameters on the alloy contents, microstructures and magnetic properties of Co xCu 1−x nanowires were studied. It is shown that Co content decreased by increasing the off-time between pulses in a wide range ( x = 0.53-0.07). These results are in consistence with saturation magnetization, which was reduced with increase in the off-time between pulses. It was also found that by optimizing the off-times, it is possible to fabricate CoCu nanowires with mixed phase of hcp Co, fcc Cu and fcc CoCu crystal phase. 相似文献
17.
The cross conductivities in the ionic-electronic conduction have been measured for α Ag 2Se at 162°C and β Cu 2S at 340°C, and it has been found that the Onsager reciprocal relation is satisfied in the whole measured range of the nonstoichiometry. The measured cross conductivities are smaller than the ionic conductivity by the factor 10 ?2 to 10 ?3. 相似文献
18.
197Au and 125Te Mössbauer spectroscopy has been applied for the low-temperature β-phases of Ag 3AuX 2 (X=S, Se, and Te). The values of I. S. and Q. S. for 197Au suggest that the gold atoms, linearly coordinated by two chalcogen atoms in these phases, exist as monovalent cations. The 125Te Mössbauer spectra suggest that the tellurium atoms are substantially ionic for both Ag 2Te and Ag 3AuTe 2. The nature of X-Au-X bonds is discussed on the basis of the Mössbauer data and the bond distances. 相似文献
19.
It has recently been shown that lustre decoration of medieval and Renaissance pottery consists of silver and copper nanoparticles dispersed in the glassy matrix of the ceramic glaze. Here the findings of an X-ray absorption fine structure (XAFS) study on lustred glazes of shards belonging to 10th and 13rd century pottery from the National Museum of Iran are reported. Absorption spectra in the visible range have been also measured in order to investigate the relations between colour and glaze composition. Gold colour is mainly due to Ag nanoparticles, though Ag +, Cu + and Cu 2+ ions can be also dispersed within the glassy matrix, with different ratios. Red colour is mainly due to Cu nanoparticles, although some Ag nanoparticles, Ag + and Cu + ions can be present. The achievement of metallic Cu and the absence of Cu 2+ indicate a higher reduction of copper in red lustre. These findings are in substantial agreement with previous results on Italian Renaissance pottery. In spite of the large heterogeneity of cases, the presence of copper and silver ions in the glaze confirms that lustre formation is mediated by a copper- and silver-alkali ion exchange, followed by nucleation and growth of metal nanoparticles. 相似文献
20.
We investigate the frequency dependent conductivity σ(ω) for ω in the vicinity of the jump rate Γ 0. The most general model based on hopping diffusion predicts a σ(ω) consistent with experiment for β-Al 2O 3 but qualitatively at odds for Ag + and Cu + conductors. We consider the coupling of the transition rate to an external variable such as a long lived, low frequency lattice mode and show that this mechanism can give structure in σ(ω) of the form observed in Ag + and Cu + conductors. 相似文献
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