三维石墨烯的制备及其在电化学生物传感器中的研究现状

三维石墨烯具有多孔网络结构、大的比表面积、高的导电性、优异机械性能和良好的生物相容性,作为电化学生物传感器电极材料在检测生物分子方面表现出优异的性能,是一种非常理想的电化学生物传感器电极材料。本文综述了三维石墨烯的制备方法及其在电化学生物传感器中最新的研究进展。     

用单次电化学实验求电极邻近区域三维扩散方程的通解

电化学问题中的三维扩散方程一般都很难求解,即使是微园盘电极,也多采用数值计算或近似方法来处理。若电极形状不规则,严格求解将更困难,即便借助计算机也是件耗时而麻烦的工作。为解决这一困难,本文提出用单次电化学实验求电极邻近区域三维扩散方程通解的设想:     

三维结构泡沫Co3O4的制备及电化学性能

通过电化学沉积方法在三维结构泡沫镍基体上沉积金属钴层, 利用固相氧化方法制备了三维结构泡沫Co3O4负极. XRD和SEM结果显示, 电化学沉积制备得到具有纳米结构的金属钴层, 经固相氧化处理, 在泡沫镍基体表面形成了Co3O4微米级的致密活性氧化层. 通过充放电和循环伏安以及电化学阻抗等方法研究了电极的电化学性能, 结果表明, 当放电电位区间为0.05~3.2 V时, 三维泡沫Co3O4于0.2 C倍率下充放电, 初始容量损失为29%, 经50次循环后, 质量比容量为824 mA·h/g, 三维泡沫结构提高了Co3O4电极的循环容量保持性能和倍率性能.     

金属氧化物电化学电容器

电化学电容器是一类利用电化学双电层或电极材料在电极表面及体相发生的氧化还原反应而存储能量的装置，具有高比能量、良好的可逆性和长循环寿命。金属氧化物电极目前主要有贵金属氧化物和过渡金属氧化物。本文简要介绍了金属氧化物电化学电容器的储能机理、特点及应用，总结了电极材料的制备及改性方法；并简要评述了电极材料的研究进展。     

用于储锂电池的三维碳结构集流体

三维碳结构材料具有轻质、优异的热学和电学性质,良好的机械性能和电化学稳定性等特点,用作电化学储能器件的集流体能够优化电极材料层中的导电网络同时缓解体积膨胀,实现电极能量密度、功率密度和循环稳定性的同时提升,在电化学储能领域展现出了巨大的应用潜力.本文结合本课题组在碳材料方面的部分研究工作,概述了当前三维碳结构集流体在锂离子电池中的最新研究进展.根据三维网络结构基元之间的连接方式,从共价键组装和非共价键组装的三维碳网络两个方面进行了分类总结,并对碳集流体在锂离子电池中存在的问题及发展方向进行了阐述,从而为进一步设计和优化新型的三维碳结构集流体提供新思路.     

复合金属氧化物Sn-Sb-Mn/陶瓷粒子电极体系的电催化性能

通过热分解法制备了复合金属氧化物Sn-Sb-Mn/陶瓷粒子电极, 分别采用扫描电子显微镜(SEM)、能量色散X 射线能谱(EDS)、X射线衍射(XRD)和N2吸附-脱附等技术对电极的形貌、晶相组成、比表面积和孔径分布进行了表征. 考察了该三维粒子电极系统的析氧特性, 采用循环伏安法分析了三维系统的电催化性能, 并且进行了电化学催化降解苯酚的试验. 结果表明, 制备的陶瓷粒子电极涂层比表面较大、孔结构发达, 有利于电催化反应; 电催化降解主要发生在电化学析氧区; 粒子电极系统对苯酚降解作用显著, 明显高于二维电极系统, 苯酚的去除率为92.3%, 总有机碳(TOC)的去除率为66.7%. 研究结果表明, 该三维粒子电极系统具有优良的电催化性能.     

载钯聚苯胺/聚砜复合膜修饰电极对甲酸的电催化氧化

采用电化学聚合法在铂电极表面制备了三维网状结构的聚苯胺(PAN)/聚砜(PSF)复合膜,并以此为载体制备了Pd/PAN/PSF复合膜电极,并用扫描电子显微镜对复合膜的微观形貌进行了表征。结果显示,此复合膜具有双层多孔结构,Pd纳米粒子在复合膜上平均粒径小、分散性好,有效地改善了Pd粒子的分散度和电极结构。电化学测试结果表明,Pd/PAN/PSF复合膜修饰电极对甲酸的电催化性能明显优于直接电沉积Pd的聚苯胺电极,并且表现出较高的稳定性。     

有关电极电位概念的一些问题

有关电极电位概念的一些问题李爱昌（廊坊师专化学系廊访１０２８４９）关键词电极电位，化学位，电化学位电极电位（势）是电化学中最基本的概念，此概念具有一定的复杂性。近期出版的一些物理化学教科书、文献甚至某些专著在此概念及其相关问题上说法不一，这在一定程度...     

纳米碳管电极上氧的电催化还原

以聚四氟乙烯为粘结剂制成了多壁纳米碳管（MWNT）电极.采用恒电位阶跃法和循环伏安法研究了MWNT电极在碱性溶液中的电化学行为，并对碱性溶液中溶解氧在该电极上的电化学还原行为进行了研究.实验结果表明： MWNT电极具有比石墨电极更高的孔隙率和电化学表面积；MWNT电极上O2还原成的反应为准可逆过程；在5～50 mV•s－1的扫描速率范围内，阴极峰电流与扫描速度成线性关系，表明MWNT电极上O2还原成的反应受吸附控制；对碱性溶液中的氧还原反应， MWNT比石墨具有更高的催化活性.     

新型三维网状锡-钴合金负极材料的结构与性能

应用电沉积技术制备了三维网状结构的Sn-Co合金负极材料, 采用XRD、SEM和电化学方法考察了该负极材料的结构和性能. XRD分析表明, 该三维网状结构的Sn-Co合金镀层为六方固溶体结构. 其电化学性能测试表明: 三维网状结构Sn-Co合金微晶电极的性能稳定, 其首次放电容量高达493.4 mAh•g−1, 首次库仑效率达80.03％, 而平面结构Sn-Co合金电极的首次库仑效率为63.47％. 经50周充放电循环后, 三维网状结构Sn-Co合金电极的放电容量为329.6 mAh•g−1, 放电容量保持率为66.8％；SEM分析表明: 三维网状Sn-Co合金电极表面是由大小不一、高低不同的“岛”紧密排列在一起；“岛”和多孔结构的存在, 缓冲了锂嵌入时体积的膨胀, 部分抑制了材料结构的变化, 减缓了电极容量的衰减, 改善了电极的循环性能.     

Implementation of a Chloride‐selective Electrode Into a Closed Bipolar Electrode System with Fluorimetric Readout

Applicability of a bipolar electrode system was tested for arrangements containing a typical ion‐selective electrode (ISE) connected with an electrode coated by a conducting polymer characterized by electroluminescence. In this case a selective response of the ISE membrane at one pole of the bipolar electrode is transduced to a fluorimetric signal obtained by reduction of the conducting polymer at the second pole. This signal transformation mode was studied on example of a simple closed bipolar electrode system composed of all‐solid‐state chloride‐selective electrode with polypyrrole transducer as the sensing pole and the reporting pole represented by electrode coated by poly(3‐octylthiophene) (POT) layer characterized by fluorescence in the neutral state. In this system selective and linear dependences of fluorimetric signal on logarithm of chloride ions concentration in turn‐on mode were recorded for optimized external voltage applied. Alternatively, a concept of cascade bipolar electrode system with incorporation of additional bipolar electrode being a polarization source for the sensing bipolar electrode with ISE and POT layer was also tested. A significant advantage of the cascade system is its possibility to work spontaneously without external polarization. For this case also linear calibration plots of fluorimetric signal vs. logarithm of analyte concentration were recorded.     

A method for the determination of speed-dependent semi-classical vector correlations from sliced image anisotropies

We present analytical expressions relating the bipolar moment β(Q)(K)(k(1)k(2)) parameters of Dixon to the measured anisotropy parameters of different pump/probe geometry sliced ion images. In the semi-classical limit, when there is no significant coherent contribution from multiple excited states to fragment angular momentum polarization, the anisotropy of the images alone is sufficient to extract the β(Q)(K)(k(1)k(2)) parameters with no need to reference relative image intensities. The analysis of sliced images is advantageous since the anisotropy can be directly obtained from the image at any radius without the need for 3D-deconvolution, which is not applicable for most pump/probe geometries. This method is therefore ideally suited for systems which result in a broad distribution of fragment velocities. The bipolar moment parameters are obtained for NO(2) dissociation at 355 nm using these equations, and are compared to the bipolar moment parameters obtained from a proven iterative fitting technique for crushed ion images. Additionally, the utility of these equations in extracting speed-dependent bipolar moments is demonstrated on the recently investigated NO(3) system.     

Shaping and exploring the micro- and nanoworld using bipolar electrochemistry

Bipolar electrochemistry is a technique with a rather young history in the field of analytical chemistry. Being based on the polarization of a conducting object which is exposed to an external electric field, it allowed recently the development of new methods for controlled surface modification at the micro- and nanoscale and very original analytical applications. Using bipolar electrodes, analyte separation and detection becomes possible based on miniaturized systems. Moreover, the modified objects that can be created with bipolar electrochemistry could find applications as key components for detection systems. In this contribution, the principles of bipolar electrochemistry will be reviewed, as well as recent developments that focus on the modification of objects at the nano- and microscale and their potential application in miniaturized analytical systems.     

Coherent and incoherent orientation and alignment of ICN photoproducts

We report extended measurements of the rotational polarization and correlated angular distribution of CN photofragments from ICN photodissociation, with a particular emphasis on the creation and detection of molecular orientation with circularly-polarized light. Doppler profiles of the nascent photoproducts are measured by Frequency-Modulated (FM) transient absorption, and the resulting high signal-to-noise data are valuable for verifying the form of the angular correlations between the recoil velocity, the photofragment rotational angular momentum, and the space-fixed frame defined by the dissociation polarization. A space-fixed bipolar moment notation can be used for an unambiguous characterization of the maximal set of polarization properties that can be created with one-photon excitation and detected with one-photon Doppler-resolved absorption spectroscopy. Relating the observed polarization moments to the various coherent and incoherent, adiabatic and non-adiabatic mechanisms, that have been derived and verified extensively in the case of diatomic photodissociation to polarized atomic fragments, is not unambiguous in the case of diatomic fragments from triatomic precursors. Constraints among various polarization moments confirmed in the case of diatomic dissociation are not confirmed in this triatomic case, where the perpendicular transitions to non-degenerate A' and A' components of a linear Omega = 1 state are qualitatively different from excitation to degenerate Omega = +/-1 states in a diatomic molecule.     

13C N.M.R. and 14N N.Q.R. in ferroelectric liquid crystals Polar versus quadrupolar ordering

¹³C nuclear magnetic resonance and ¹⁴N nuclear quadrupole resonance spectra of ferroelectric smectic C*liquid crystals and their non-chiral analogues allow for a microscopic determination of the polar and quadrupolar (or bipolar) biasing of rotation around the long molecular axis as well as for a determination of the anisotropy in the fluctuations of this axis. The results show that the microscopic origin of the biquadratic coupling between the polarization and the tilt, which has been recently introduced into the extended Landau model of the S_A-S*_C transition, is the quadrupolar (or bipolar) rotational bias induced by the anisotropy in the fluctuations of the long molecular axis. The tilt induced anisotropy in the fluctuations is practically identical in chiral and non-chiral smectic C phases.     

Effects of inorganic substances on water splitting in ion-exchange membranes; II. Optimal contents of inorganic substances in preparing bipolar membranes

An approach to enhancing the water-splitting performance of bipolar membranes (BPMs) is introducing an inorganic substance at the bipolar (BP) junction. In this study, the immobilization of inorganic matters (i.e., iron hydroxides and silicon compounds) at the BP junction and the optimum concentration have been investigated. To immobilize these inorganic matters, novel methods (i.e., electrodeposition of the iron hydroxide and processing of the sol-gel to introduce silicon groups at the BP junction) were suggested. At optimal concentrations, the immobilized inorganic matters significantly enhanced the water-splitting fluxes, indicating that they provide alternative paths for water dissociation, but on the other hand possibly reduce the polarization of water molecules between the sulfonic acid and quaternary ammonium groups at high contents. Consequently, the amount of inorganic substances introduced should be optimized to obtain the maximum water splitting in the BPM.     

Control of retention and fatigue-free characteristics in CaBi4Ti4O15 thin films prepared by chemical method

Ferroelectric CaBi₄Ti₄O₁₅ (CBTi144) thin films were deposited on Pt/Ti/SiO₂/Si substrates by the polymeric precursor method. The films present a single phase of layered-structured perovskite with polar axis orientation after annealing at 700 °C for 2 h in static air and oxygen atmosphere. The a/b-axis orientation of the ferroelectric film is considered to be associated with the preferred orientation of the Pt bottom electrode. It is noted that the films annealed in static air showed good polarization fatigue characteristics at least up to 10¹⁰ bipolar pulse cycles and excellent retention properties up to 10⁴ s. On the other hand, oxygen atmosphere seems to be crucial in the decrease of both, fatigue and retention characteristics of the capacitors. Independently of the applied electric field, the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.     

Effect of electrode material on contact high-voltage polarization in a vinylidene fluoride-hexafluoropropylene copolymer

High-voltage polarization processes occurring in alternating fields of various frequencies in extruded films of vinylidene fluoride-hexafluoropropylene copolymers are studied. Remanent polarization typical for ferroelectric polymers with a polar cell appears during crystallization in the nonpolar α phase. This effect is associated with the presence of a highly imperfect ferroelectric (or antiferroelectric) phase in the copolymer, where chains assume planar zigzag conformations. The magnitude of remanent polarization depends on the frequency of the applied bipolar sawtooth voltage. This observation may be explained by the fact that the resulting field is created not only by the external source but also by the space charge that is contributed by carriers injected from electrodes. With the use of deposited Au and Al, the role of electrode material in polarization and conduction processes is ascertained. In the case of Al, Al₂O₃ and new Al-C chemical bonds are formed on the polymer surface. Owing to formation of these additional dielectric layers at the copolymer/metal interface, electrodes may be blocked partially. The above new chemical bonds facilitate formation of deeper surface traps for carriers; as a result, the remanent surface potential appears in polarized samples even after storage in the short-circuit mode.     

Spatially-resolved multicolor bipolar electrochemiluminescence

Here we describe a new aspect of multicolor potential-resolved electrochemiluminescence (ECL) based on bipolar electrochemistry (BPE). BPE involves a potential gradient established along a polarized conducting object which thus acts as a bipolar electrode (BE). The resulting driving force can induce electron-transfer reactions, necessary for processes such as ECL occurring at different longitudinal locations along the same BE. In this work, we exploit the entire spatial domain where anodic polarization occurs to demonstrate, for the first time, how the potential gradient along a BE may be used to simultaneously resolve the emissions of ECL-active luminophores with differing oxidation potentials. The control of both size and position of the ECL-emitting domains was achieved by tuning the applied electric field. Multicolor light-emission was analyzed in detail to demonstrate spatial and spectral resolution of a solution containing different emitters.     

Speed dependent rotational angular momentum polarization of the O2 (a 1Deltag) fragment following ozone photolysis in the wavelength range 248-265 nm

The translational anisotropy and rotational angular momentum polarization of a selection of rotational states of the O2 (a 1Deltag; v=0) photofragment formed from ozone photolysis at 248, 260, and 265 nm have been determined using the technique of resonance enhanced multiphoton ionization in combination with time of flight mass spectrometry. At 248 nm, the dissociation is well described as impulsive in nature with all rotational states exhibiting similarly large, near-limiting values for the bipolar moments describing their angular momentum alignment and orientation. At 265 nm, however, the angular momentum polarization parameters determined for consecutive odd and even rotational states exhibit clear differences. Studies at the intermediate wavelength of 260 nm strongly suggest that such a difference in the angular momentum polarization is speed dependent and this proposal is consistent with the angular momentum polarization parameters extracted and reported previously for longer photolysis wavelengths [G. Hancock et al., Phys. Chem. Chem. Phys. 5, 5386 (2003); S. J. Horrocks et al., J. Chem. Phys. 126, 044308 (2007)]. The alternation of angular momentum polarization for successive odd and even J states may be a consequence of the different mechanisms leading to the formation of the two O2 (a 1Deltag) Lambda doublets. Specifically, the involvement of out of plane parent rotational motion is proposed as the origin for the observed depolarization for the Delta- relative to the Delta+ state.