共查询到20条相似文献，搜索用时 15 毫秒
1.
An extremely small, conically shaped Pt microelectrode tip (with a radius of 30 nanometers) and the precise positioning capabilities of the scanning electrochemical microscope were used to penetrate a thin (200 nanometers) polymer film and obtain directly the standard potential and kinetic parameters of an electrode reaction within the film. The thickness of the film was determined while it was immersed in and swollen by an electrolyte solution. The film studied was the perfluorosulfonate Nafion containing Os(bpy)(3)(2+) (bpy, 2,2'-bipyridine) cast on an indium tin oxide surface. The steady-state response at the ultramicroelectrode allowed direct determination of the rate constant for heterogeneous electron transfer K(o) and the diffusion coefficient D without complications caused by transport in the liquid phase, charge exchange at the liquid-polymer interface, and resistive drop. 相似文献
2.
Huang JY Zhong L Wang CM Sullivan JP Xu W Zhang LQ Mao SX Hudak NS Liu XH Subramanian A Fan H Qi L Kushima A Li J 《Science (New York, N.Y.)》2010,330(6010):1515-1520
We report the creation of a nanoscale electrochemical device inside a transmission electron microscope--consisting of a single tin dioxide (SnO(2)) nanowire anode, an ionic liquid electrolyte, and a bulk lithium cobalt dioxide (LiCoO(2)) cathode--and the in situ observation of the lithiation of the SnO(2) nanowire during electrochemical charging. Upon charging, a reaction front propagated progressively along the nanowire, causing the nanowire to swell, elongate, and spiral. The reaction front is a "Medusa zone" containing a high density of mobile dislocations, which are continuously nucleated and absorbed at the moving front. This dislocation cloud indicates large in-plane misfit stresses and is a structural precursor to electrochemically driven solid-state amorphization. Because lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical effects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, our observations provide important mechanistic insight for the design of advanced batteries. 相似文献
3.
以尿素为氮源,采用Sol-gel法及浸渍-提拉法制备氮杂化TiO2-N薄膜,并运用正交试验法优化TiO2-N薄膜的最佳制备条件;利用AFM分析技术对TiO2-N薄膜表面形貌进行表征;在太阳光光催化反应器中,探讨TiO2-N薄膜对饮用水供水水源水体中大肠菌群的杀菌作用。结果表明,热处理条件是影响TiO2-N薄膜制备的关键因素,各个影响因素的主次顺序为热处理温度〉停留温度〉热处理时间,在最佳条件下制备的TiO2-N薄膜,在太阳光作用下光解30min时,对饮用水供水水源水体中大肠菌群的杀菌率达到57.7%以上;Ag的协同掺杂（Ag-TiO2-N）或在TiO2-N薄膜表面的沉积（Ag/TiO2-N）,显著提高了TiO2-N薄膜的杀菌作用,对大肠菌群的杀菌率可达90%以上。 相似文献
4.
为采用绿色环保的高效方法去除海洋柴油污染,在实验室条件下,采用化学沉淀法制得半导体纳米SnO_2光催化剂,并利用SEM、XRD测试等方法,对其结构、晶粒尺寸等进行了表征,实验室内配制柴油污染海水,通过改变试验条件,对影响纳米SnO_2光催化剂及其光催化降解海水中柴油污染物效果的因素进行了研究,并通过正交试验优化了纳米SnO_2光催化剂及其光催化降解海水中柴油污染物的试验条件。结果表明:所制备的样品为金红石样的SnO_2粒子,平均直径为40.3 nm;正交试验结果显示,当纳米SnO_2光催化剂的煅烧温度为500℃、添加量为0.2 g/L、柴油初始浓度为0.2 g/L、过氧化氢溶液浓度为0.3 g/L、紫外光照时间为4 h、海水p H值为7.9时,用纳米SnO_2光催化剂光催化降解海水中柴油污染物的降解率达到98.01%。研究表明,使用纳米SnO_2作为光催化剂,可以明显提高海洋柴油污染的降解率。 相似文献
5.
[目的]研究用铋膜电极代替汞膜电极同时测定食物中锌和铜元素含量的新方法。[方法]以预镀铋膜的玻碳电极作为工作电极,饱和甘汞电极作为参比电极,铂电极作为辅助电极,采用差分脉冲溶出伏安法同时测定黄豆和板栗样品中锌和铜元素的含量。考察了镀铋液浓度、底液的种类和浓度、初始电位、电沉积电位、终止电位及电位增量等对试验结果的影响。[结果]在1.0 mol/L硫氰化钾底液中,锌和铜均有灵敏的溶出峰,线性范围分别为0.20～12.00和0.10～6.00μg/ml,检出限分别为2.08、5.49μg/L,回收率为91.20%～104.50%。在所选择的电位范围内,铋膜稳定性较好,多次测定锌和铜的峰电流基本不变。[结论]铋膜电极差分脉冲溶出伏安法简便快速、灵敏度高,适合于食物中锌和铜元素含量的同时分析。 相似文献
6.
利用直流磁控溅射Ta膜和阳极氧化法制备Ta2O5薄膜,能谱分析（EDS）和X射线衍射仪（XRD）研究表明,在H3PO4电解液中添加少量的乙二醇制备的Ta2O5薄膜,呈非晶态,没有β-Ta2O5晶相出现.利用电击穿场强测试系统研究Ta-Ta2O5-Al复合薄膜制备FED器件（MIM结构）的绝缘性,证明采用磁控溅射和阳极氧化法成功制备了漏电流密度低、耐击穿场强高的Ta2O5薄膜. 相似文献
7.
A device configuration for light emission from electroactive polymers is described. In these light-emitting electrochemical cells, a p-n junction diode is created in situ through simultaneous p-type and n-type electrochemical doping on opposite sides of a thin film of conjugated polymer that contains added electrolyte to provide the necessary counterions for doping. Light-emitting devices based on conjugated polymers have been fabricated that operate by the proposed electrochemical oxidation-reduction mechanism. Blue, green, and orange emission have been obtained with turn-on voltages close to the band gap of the emissive material. 相似文献
8.
采用化学溶液沉积法在石英衬底上制备纳米颗粒ZnO/Bi3.6Eu0.4Ti3O12(BEu T)铁电复合薄膜.光致发光研究结果表明,通过引入ZnO纳米颗粒,BEuT薄膜中Eu3+的发光大大增强,其强度大约是单纯BEu T薄膜的35倍.这种发光强度的极大改善归因于从ZnO到Eu3+的能量传递效率高. 相似文献
9.
The use of bismuth-layered perovskite films for planar-type nonvolatile ferroelectric random-access memories requires films with spontaneous polarization normal to the plane of growth. Epitaxially twinned a axis-oriented La-substituted Bi4Ti3O12 (BLT) thin films whose spontaneous polarization is entirely along the film normal were grown by pulsed laser deposition on yttria-stabilized zirconia-buffered Si(100) substrates using SrRuO3 as bottom electrodes. Even though the (118) orientation competes with the (100) orientation, epitaxial films with almost pure (100) orientation were grown using very thin, strained SrRuO3 electrode layers and kinetic growth conditions, including high growth rates and high oxygen background pressures to facilitate oxygen incorporation into the growing film. Films with the a-axis orientation and having their polarization entirely along the direction normal to the film plane can achieve a remanent polarization of 32 microcoulombs per square centimeter. 相似文献
10.
以单层聚对苯乙炔（PPV）薄膜发光二极管为例，研究其薄膜中的电场分布，探讨其电场分布对载流子注入、输运和复合的影响，研究结果有助于揭示其发光机理，为提高发光效率提供了有益的启示。 相似文献
11.
将四(5,6-二氢-1,4-二噻英)四氮杂卟啉(FePz(dtn)4)通过电沉积的方式固载在玻碳电极上,该电极在抗坏血酸(AA)和尿酸(UA)等干扰物存在下,可选择性地检测多巴胺(DA).对比裸电极,在循环伏安测量中修饰过后的电极在氧化电位处对DA表现出良好的电催化活性.并且出现一对可逆的氧化还原峰,阳极和阴极的电位值分别为0.182V和0.142V.在电解质溶液中氧化峰电流随着DA的浓度线性增加.两个线性范围分别是1～10和10～200μg/mL,相关系数分别为0.996 7和0.998 8.检出限为0.3μg/mL. 相似文献
12.
The photosynthetic characteristics of strawberry(Fragaria x ananassa Duch. cv. Toyonoka)leaves under illumination of identical light intensity(55-57% natural light)with different light quality were studied. It was showed that the chlorophyll content,maximal photochemical efficiency of PS Ⅱ(Fv/Fm),Fm/Fo,amount of inactive PS Ⅱ reaction centers(Fi-Fo)and rate of QAreduction were positively correlated with the red-light/blue-light ratios,but the chlorophyll(a/b)ratios were negatively correlated with them. Carotenoid content of the leaves was maximum under the blue film,than under green film,red film,white film and yellow film,and negatively correlated with the red/farred ratios. The apparent quantum yield(AQY),photorespiratory rate(Pr)and carboxylation efficiency(CE)were also strongly affected by light quality. The photosynthetic rate(Pn)in strawberry leaves under green film was significantly lower than under all other film. Our results suggested that light quality is an essential factor regulating the development of PS Ⅱ and phytochrome and an independent blue light photoreceptor,possibly a cryptochrome,can regulate photosynthetic performance. 相似文献
13.
Damped voltage oscillations occur when current steps are applied to a cell consisting of a thin layer of Fe(111)/Fe(11) electrolyte sandwiched between horizontal, parallel, platinized platinum electrodes. The upper electrode must be the anode, and the magnitude of the current must be larger than a threshold value. The oscillations signal the onset of convection in the fluid. The experiment provides a new method for investigating transient convection processes. 相似文献
14.
Nelson CT Gao P Jokisaari JR Heikes C Adamo C Melville A Baek SH Folkman CM Winchester B Gu Y Liu Y Zhang K Wang E Li J Chen LQ Eom CB Schlom DG Pan X 《Science (New York, N.Y.)》2011,334(6058):968-971
The utility of ferroelectric materials stems from the ability to nucleate and move polarized domains using an electric field. To understand the mechanisms of polarization switching, structural characterization at the nanoscale is required. We used aberration-corrected transmission electron microscopy to follow the kinetics and dynamics of ferroelectric switching at millisecond temporal and subangstrom spatial resolution in an epitaxial bilayer of an antiferromagnetic ferroelectric (BiFeO(3)) on a ferromagnetic electrode (La(0.7)Sr(0.3)MnO(3)). We observed localized nucleation events at the electrode interface, domain wall pinning on point defects, and the formation of ferroelectric domains localized to the ferroelectric and ferromagnetic interface. These results show how defects and interfaces impede full ferroelectric switching of a thin film. 相似文献
15.
The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 +/- 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 +/- 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 +/- 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30 degrees rotation of the Cu monolayer lattice from the Au lattice is clearly visible. 相似文献
16.
A Fluorite Isotype of SnO2 and a New Modification of TiO2: Implications for the Earth's Lower Mantle
Liu LG 《Science (New York, N.Y.)》1978,199(4327):422-425
The existence of a cubic fluorite-type SnO(2) and a hexagonal TiO(2) (which may be related to the fluorite structure) have been demonstrated by an in situ x-ray diffraction study in which a diamond-anvil pressure cell was used after the samples had been heated by a continuous yttrium-aluminum-garnet laser. At room temperature, the lattice parameter for SnO(2) (fluorite) is a = 4.925 +/- 0.005 angstroms and those for TiO(2) (fluorite-related) are a = 9.22 +/- 0.01 angstroms and c = 5.685 +/- 0.006 angstroms at about 250 kilobars. The volume change associated with the transition from rutile to fluorite (or related structure) is about -8 percent for SnO(2) and -10.5 percent for TiO(2) at transition. Upon release of pressure, both the fluorite-type SnO(2) and the TiO(2) reverted to the alpha-PbO(2) structure at room temperature. The hypothesis that the earth's lower mantle is composed of oxide phases might be feasible if it were possible for SiO(2) to possess the fluorite structure or its related forms at high pressure, as shown for SnO(2) and TiO(2) in this study. The oxide hypothesis proposed here differs from that postulated by Birch in that the primary coordination of silicon is 6 for Birch's hypothesis and 8 for the hypothesis presented here. 相似文献
17.
Johnson M 《Science (New York, N.Y.)》1993,260(5106):320-323
A thin ferromagnetic film can be used to polarize the spin axes of the electrons carrying an electric current in a manner loosely analogous with a light polarizer. When such a film is fabricated on a gold film, a nonequilibrium population of spin-polarized electrons is built up in the gold causing a "spin bottleneck" effect. The addition of a second ferromagnetic film results in a device whose output voltage depends on the orientation of the spins. 相似文献
18.
Hickman JJ Ofer D Laibinis PE Whitesides GM Wrighton MS 《Science (New York, N.Y.)》1991,252(5006):688-691
Self-assembly of a ferrocenyl thiol and a quinone thiol onto Au microelectrodes forms the basis for a new microsensor concept: a two-terminal, voltammetric microsensor with reference and sensor functions on the same electrode. The detection is based on measurement of the potential difference of current peaks for oxidation and reduction of the reference (ferrocene) and indicator (quinone) in aqueous electrolyte in a two-terminal, linear sweep voltammogram in which a counterelectrode of relatively large surface area is used. The quinone has a half-wave potential, E((1/2)), that is pH-sensitive and can be used as a pH indicator; the ferrocene center has an E(1/2) that is a pH-insensitive reference. The key advantages are that such sensors require no separate reference electrode and function as long as current peaks can be located for reference and indicator molecules. 相似文献
19.
【目的】制备磷钼酸复合膜修饰电极,并对其电化学性质和果蔬维生素C含量的测定进行相关探究,为深色果蔬中维生素C的测定提供理论依据。【方法】利用电化学沉积法在E=+0.26 V恒电位下制备磷钼酸复合膜修饰电极,并在不同条件下对其电化学性质进行检测,再以水果和蔬菜为研究对象,检验磷钼酸复合膜修饰电极对维生素C含量测定的效果。【结果】制备所得的磷钼酸具有稳定的Keggin结构;磷钼酸修饰后的电极在-0.4~+0.6 V内具备可逆的氧化还原峰;磷钼酸复合膜修饰电极的电催化能力与磷钼酸浓度呈正相关,且在高酸环境中电化学催化能力更强;该修饰电极对维生素C的氧化催化活性较明显,氧化催化活性随磷钼酸氧化程度和扫速的增加而提高,在连续增加维生素C浓度的过程中,修饰电极能快速响应维生素C,最短响应时间仅需3 s;以该电极为工作电极检测获得橙子、胡萝卜和青椒3种样品维生素C含量分别为45.32、71.16和96.99 mg/100 g,3次测定结果平均值的相对标准偏差（RSD）均未超过5.0%,且最低检测限为1.1×10-8 mol/L（S/N=3）。【结论】磷钼酸复合膜修饰电极的氧化催化活性良好,对深色果蔬维生素C的检测具有灵敏度高、检出限低和测定结果误差较小等特点。 相似文献
20.
针对贵州开阳县茶叶生长的环境特点,以5年生龙井43号绿茶为实验材料,研究不同覆盖方式对茶园土壤水分及茶叶产量的影响。结果表明:采用稻草+薄膜覆盖方式对贵州开阳县春茶的生长环境是最好方式,使得茶园土壤水分达到最高为22.87%,茶叶鲜重产量达到最高为179.88 kg/667m2。其它4种方式与清耕(CK)相比,茶叶的叶面积、茶叶的干物质量有显著提高,稻草+薄膜处理增产最高,同比增长26.92%,薄膜处理增长最低。采用稻草+薄膜覆盖是贵州喀斯特地区春季茶园提高土壤水分、增加茶叶产量的有效方式。 相似文献