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1.
Nanoscopic impedance measurements were carried out on silver ion conducting glasses by coupling an impedance spectrometer with an atomic force microscope. When ac voltages were applied to a conducting AFM tip being in contact with the glass surface, silver nanoparticles were formed during the cathodic half cycle, which were not completely reoxidized in the anodic half cycle. We describe two protocols allowing for a controlled particle growth. The electrochemical oxidation/reduction processes led to low tip/sample interfacial impedances, and the formed silver particles acted as nanoelectrodes sensing the spreading resistance of the glass below the particles. We made a quantitative check of the spreading resistance formula under the assumption that spreading of the electric field is governed by the lateral diameter of the particles and found good agreement between the mean value of the local conductivities obtained at different tip positions and the macroscopic conductivity.  相似文献   

2.
Ag_2O胶体粒子的自组装单层膜和多层膜   总被引:4,自引:0,他引:4  
徐冉  李薇 《光散射学报》1999,11(2):151-154
本文制备了Ag2O胶体粒子的自组装单层膜和多层膜。运用接触角测量、红外吸收光谱和紫外可见吸收光谱等手段证实了Ag2O胶体粒子能够组装在具有羧基的基底上,在有1,18 十八烷基二羧酸做为交联剂的情况下还可形成自组装多层膜  相似文献   

3.
The purpose of this study was to find relationships between subglottal pressure (P(s)) and fundamental frequency (F(0)) of phonation in excised larynx models. This included also the relation between F(0) and its rate of change with pressure (dFdP). Canine larynges were prepared and mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottal adduction was accomplished either by using two-pronged probes to press the arytenoids together or by passing a suture to simulate lateral cricoarytenoid muscle activation. The pressure-frequency relation was obtained through a series of pressure-flow sweep experiments that were conducted for eight excised canine larynges. It was found that, at set adduction and elongation levels, the pressure-frequency relation is nonlinear, and is highly influenced by the adduction and elongation. The results indicated that for the lower phonation mode, the average rate of change of frequency with pressure was 2.9+/-0.7 Hzcm H(2)O, and for the higher mode was 5.3+/-0.5 Hzcm H(2)O for adduction changes and 8.2+/-4.4 Hzcm H(2)O for elongation changes. The results suggest that during speech and singing, the dFdP relationships are taken into account.  相似文献   

4.
Xiao Q  Ye S  Zheng D  Zhang L  Wu J 《Molecular diversity》2012,16(2):261-268
Diverse 1-imidazolylisoquinolines are generated through a silver triflate-catalyzed cascade reaction of 2-alkynylbenzaldoxime with imidazole or benzoimidazole using parallel diversity-oriented synthesis. A small library of 1-imidazolylisoquinolines can be constructed efficiently under mild conditions. A plausible mechanism is proposed. We discovered that the presence of silver triflate and bromotrispyrrolidinophosphonium hexafluorophosphate (PyBroP) is essential for the reaction transformation. In the reaction process, treatment of 2-alkynylbenzaldoxime with silver triflate affords isoquinoline-N-oxide. Then, isoquinoline-N-oxide acts as a nucleophile to attack PyBroP to replace the bromide. Subsequently, an intermolecular nucleophilic addition of imidazole and further deprotonation take place to produce the desired 1-imidazolylisoquinolines. A range of great diversity could be easily introduced under the standard conditions during the reaction process.  相似文献   

5.
铕激活银离子导电玻璃的白光发射   总被引:1,自引:1,他引:0  
空气气氛下在铕激活银离子导电玻璃中,实现了Eu3+→Eu2+的还原。通过改变基质中Ag2O的含量,能够调整Eu3+/Eu2+比率,从而实现白光发射。在Ag2O的摩尔分数为30%时,发射光的色坐标为(x=0.31,y=0.36),色温为5 000 K。对Ag2O的引入引起Eu3+→Eu2+还原的机理进行了分析。可以相信铕激活银离子导电玻璃将成为白光LED理想的基质材料。  相似文献   

6.
郝艳玲  张星  方炎 《光谱实验室》2011,28(4):2019-2024
通过表面增强拉曼散射研究了胞嘧啶、胸腺嘧啶和尿嘧啶在粗糙银电极表面上的吸附形态随电极电位的变化关系.大量的结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得.分析表明在电极电位负移过程中,胞嘧啶一直通过N3位垂直吸附于纳米银颗粒表面;而胸腺嘧啶分子和尿嘧啶分子在表面的吸附状态都随电位改变发生了变化,较正电位下...  相似文献   

7.
AgI-doped silver oxide glasses are of interest both for their possible applications in electrochemical devices, and as a model system to study the transport/structure relationships in ionic glasses. Here we summarize the information given by 1-D and 2-D solid-state NMR measurements on both the cations dynamics and short (and medium) range structure of several glassy systems. Emphasis is given to understand how AgI enters into the glass matrix. A new and careful analysis of our previously reported 109Ag 1-D data shows that the glass matrix plays a relevant role in determining the efficiency of carriers formation, as well as their mobility. Finally, as an example of a modern 2-D NMR application to these materials, we report the first 11B and 17O Multiple Quantum MAS study on a glass of the system AgI:Ag2O:2B2O2, which confirms the nearly complete absence of non-bridging oxygens (NBOs) in the silver diborate composition.  相似文献   

8.
A polycrystalline silver surface has been studied by synchrotron radiation photoelectron spectroscopy after deep oxidation by microwave discharge in an O2 atmosphere. Oxidized structures with high oxygen content, AgOx with x > 1, have been found on the silver surface after oxidation at 300–400 K. The line shapes observed in the O1s spectra were decomposed into five components and indicated that complex oxidized species were formed. An analysis of the oxidized structures with binding energies, Еb(O1s), greater than 530 eV pointed to the presence of both Ag–O and O–O bonds. We have carried out a detailed experimental study of the valence band spectra in a wide spectral range (up to 35 eV), which has allowed us to register the multicomponent structure of spectra below Ag4d band. These features were assigned to the formation of Ag–O and O–O bonds composed of molecular (associative) oxygen species. DFT model calculations showed that saturation of the defect oxidized silver surface with oxygen leads to the formation of associative oxygen species, such as superoxides, with electrophilic properties and covalent bonding. The high stability of oxygen-rich silver structures, AgOx, can be explained by the formation of small silver particles during the intensive MW oxidation, which can stabilize such oxygen species.  相似文献   

9.
Paul W. Wang   《Applied Surface Science》1997,120(3-4):291-298
The structural and compositional changes of the soda-lime glasses during the formation of the silver colloids were analyzed by the X-ray Photoelectron Spectroscopy (XPS) in order to examine the silver colloid formation mechanism. The in situ behavior of silver and SiO2 networks on the surfaces of silver ion-exchanged soda-lime glasses during heating and cooling processes in ultra-high vaccum was monitored. The results showed that silver diffuses toward the surface, precipitates, and crystallizes during heating and the total silver surface concentration is slowly increased during cooling. The concentration changes of oxidized and neutral Ag, a new non-bridging oxygen species (NBO*), and a new silicon species (Si[a]) were applied to deduce a disappropriation reaction mechanism of Ag+ on the surface during annealing. The SiO2 network is modified at temperatures below 350°C to accommodate more silver on the surface and to balance the extra charge carried by the Ag+. That the SiO2 network polymerizes during annealing was deduced from the results of the higher binding energies of Si2p and O1s after annealing. This observation suggests that the reduction of the Gibbs free energies and the relaxation of tensile stress result in the formation of the silver colloids under thermal annealing.  相似文献   

10.
A new two step oxidation model is proposed that describes the mechanism of internal oxidation of the non-noble impurities antimony and indium in silver. We have found that internal oxidation at 550 K leads to the formation of isolated SbO2 or InO2 molecules, respectively. The commonly used model of Wagner treats the oxidation as a one step process, which means that in the case of antimony and indium two oxygen atoms must be trapped effectively in one step. Assuming a trapping radius of one lattice constant this model predicts an oxidation front that is much steeper than observed experimentally. The two step oxidation model assumes that first one oxygen atom is trapped at the non-oxidized impurity to form a relatively unstable complex. If within the lifetime of this complex a second oxygen atom is trapped, a stable and completely oxidized complex is formed in the silver matrix. The two step oxidation model predicts the shape of the oxidation front during internal oxidation at 550 K of antimony or indium in silver single crystals correctly, when a dissociation energy of 0.60(5) eV for the unstable complex is taken.  相似文献   

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