聚苯胺类/n-Si(111)单晶硅复合电极:制备与光电性质

在过氧化月桂酰作用下,于n-Si(111)型单晶硅表面上分别嫁接苯胺及烷基取代苯胺,进而实现晶体硅表面上聚苯胺和烷基取代聚苯胺的原位聚合,制备得到了系列聚苯胺(或烷基取代聚苯胺)/n-Si(111)单晶硅复合电极。此外,对上述合成电极表面苯胺链进行磺化,得到系列磺酸基化的单晶硅复合电极。电化学研究结果显示,聚苯胺直接嫁接于晶体硅表面所得到的复合电极光电转化效率最高,苯胺聚合链通过碳碳双键桥连于单晶硅表面所得到复合电极的光电转化效率高于通过碳碳单键桥连得到的复合电极,但其光电转化效率低于苯胺聚合链直接桥连于晶体硅表面而得到的复合电极。另外发现,苯环磺酸基化有利于提高复合电极的光电转化效率。     

聚苯胺类/n-Si(111)单晶硅复合电极:制备与光电性质

在过氧化月桂酰作用下,于n-Si(111)型单晶硅表面上分别嫁接苯胺及烷基取代苯胺,进而实现晶体硅表面上聚苯胺和烷基取代聚苯胺的原位聚合,制备得到了系列聚苯胺(或烷基取代聚苯胺)/n-Si(111)单晶硅复合电极。此外,对上述合成电极表面苯胺链进行磺化,得到系列磺酸基化的单晶硅复合电极。电化学研究结果显示,聚苯胺直接嫁接于晶体硅表面所得到的复合电极光电转化效率最高,苯胺聚合链通过碳碳双键桥连于单晶硅表面所得到复合电极的光电转化效率高于通过碳碳单键桥连得到的复合电极,但其光电转化效率低于苯胺聚合链直接桥连于晶体硅表面而得到的复合电极。另外发现,苯环磺酸基化有利于提高复合电极的光电转化效率。     

纳米纤维聚苯胺膜在不锈钢电极表面的生长过程

研究了脉冲电流法(PGM)聚合苯胺时, 纳米纤维聚苯胺(PANI)膜在不锈钢(SS)电极表面的生长过程. 用计时电位法和扫描电子显微镜(SEM)表征了聚苯胺生长过程的电化学特征和微观形貌; 并通过循环伏安(CV)法研究了苯胺的聚合速率. 结果表明, 聚苯胺的生长经历了两个阶段, 首先是在裸不锈钢电极表面上形成颗粒状聚苯胺, 此时聚合电位约为1.10 V, 经历了30 s后, 电极表面被一层颗粒状聚苯胺膜所覆盖; 在此基础上, 聚苯胺以纳米纤维状结构继续生长, 当颗粒状聚苯胺被纳米纤维状聚苯胺膜完全覆盖时, 聚合电位降至0.75 V左右并保持稳定.     

聚苯胺修饰电极上的电催化

研究了聚苯胺修饰电极对抗坏血酸，多巴胺，溴，铊及铁离子的电催化作用。实验分析了影响电催化的几个因素，并通过控制聚合方法，制得了电催化性质相异的聚苯胺修饰电极。     

电化学制备有序聚苯胺纳米线阵列

以有序碳纳米管阵列电极为基底电极,在硫酸或高氯酸溶液中,分别探明不同电化学聚合方法以及苯胺单体浓度对聚苯胺形貌的影响. 结果表明：采用循环伏安法无法制备出聚苯胺纳米线;而应用恒电位法虽可制得聚苯胺纳米线,但纳米线不能形成有序阵列;只有应用恒电流方法,并且以高浓度苯胺的高氯酸溶液作为聚合溶液,方能制得有序聚苯胺纳米线阵列.     

沸石分子筛孔道中聚苯胺的选择性掺杂研究

用电化学方法聚合分子筛孔道内的苯胺, 根据聚苯胺在无机质子酸中的掺杂反应研究了ZSM-5,Y型分子筛对磷钼杂多酸的形状选择作用     

分子筛修饰电极上离子交换过程的电化学考察

用循环伏安法研究了以１３Ｘ型分子筛修饰的玻碳电极在含Ｆｅ＾２＋溶液中的电化学行为，考察了电极浸入溶液时间，电位扫描速度、溶液的温度对Ｆｅ＾２＋／Ｆｅ＾３＋电对的电响应的影响。     

低电流密度下恒电流法制备的聚苯胺修饰电极

研究了低电流密度下恒电流法制备的聚苯（ＰＡ）修饰电极的性质及其影响因素，探讨了低电流密度聚合的ＰＡ膜的优点。发现此种条件下聚合的ＰＡ膜具有较好的电荷传输能力，它不仅对Ｂｒ＾－，Ｔｌ＾＋／Ｔｌ等电对的氧化还原反应有更好的电催化活性，而且对Ｈ＾＋的Ｎｅｒｎａｓｔ响应也更接近理论值。     

聚苯胺修饰电极制备过程中几个问题的探讨

报道聚苯胺修饰电极制备中尚须引起人们重视的几个问题。主要包括：循环伏安法扫描电位上限对聚合的影响，恒电位法最佳的聚合电位，以及仅具２００ｍＶ和９００ｍＶ两峰聚苯胺膜的制备，聚合电量对不同制备方法影响的差异性等等。并对制备聚苯胺修饰电极的几种方法进行了比较，从而指出了最佳的聚合方法和条件。     

聚苯胺薄膜电极上循环伏安法可逆波理论和验证

提出了聚苯胺薄膜电极上循环伏安法可逆波方程式，对伏安曲线的性质进行了详细的讨论。聚苯胺薄膜电极是利用浓度为１．０９ｍｏｌ／Ｌ苯胺溶液（内含２．０ｍｏｌ／Ｌ ＨＣｌ）在铂电极上用恒电流（０．０１－０．１ｍＡ／ｃｍ＾２）使苯胺发生氧化反应进而经聚合获得。结果表明，该法得到的聚苯胺膜具有良好的均匀度和单一性。在１０ｍｏｌ／Ｌ ＨＣｌ底液中获得的循环伏安曲线与理论结果相符合。     

Self‐Assembly Film of Zeolite Y Nanocrystals Loading Palladium on an Au Electrode for Electrochemical Applications

Nano‐scale zeolite Y crystals were synthesized, and palladium nanoparticles were prepared in the supercage of the zeolite by “ship‐in‐a‐bottle” approach. A novel method to fabricate zeolite‐modified electrode (ZME) loading Pd nanoparticles was developed, in which the zeolite Y loading Pd²⁺ ions was self‐assembled on (3‐mercaptopropyl) trimethoxysilane‐attached Au surface to form the stable and density packed multilayers (SAM‐ZME). The structures of zeolite Y and the SAM‐ZME were investigated by using TEM, XRD and SEM techniques. Pd²⁺ ions in the SAM‐ZME were converted into Pd nanoparticles (Pd_n⁰) by two steps consisting of the electrochemical reduction as well as the succeeding admission and release of CO. The redox couple [Fe(CN)₆]^3?/4? was used to probe the electron‐transfer barrier properties during self‐assembling process. Moreover, the special properties of the SAM‐ZME loading Pd_n⁰ were studied by using cyclic voltammetry and CO‐probe in situ FTIR spectroscopy. The results illustrated that Pd_n⁰ in the SAM‐ZME exhibits higher electrocatalytic activity for oxidation of adsorbed CO than that of ZME prepared in our previous study by zeolite coating method. The present study is of importance in design and preparation of SAM‐ZME, which poccesseses excellent properties for the immobilization of electrocatalysts or biomolecules.     

Factors affecting the analytical applications of zeolite-modified electrodes preconcentration of electroactive species

The influence of various experimental parameters on the electrochemical response of zeolite-modified electrodes (ZMEs) have been studied using ion-exchange voltammetry, with regard to their application as amperometric sensors. In order to cover a large range of parameters, the investigations were carried out using three zeolites (A, X and Y), selected for their different cation-exchange capacities and ion-sieving properties; four electroactive species (silver(I), copper(II), dopamine and methylviologen) chosen on the basis of their size, charge and inorganic or organic nature; and two kinds of ZMEs: the zeolite-modified carbon-paste electrode (ZMCPE) and the zeolite monograin layers coated on glassy carbon electrode (ZMGCE). Compared to the corresponding unmodified electrodes, improvements in sensitivity were observed when using ZMEs, due to analyte accumulation at the electrode's surface by ion exchange in zeolite particles. The concentration process, and the subsequent voltammetric response of ZMEs, were found to be strongly affected by the accessibility of the analytes to the ion-exchanging sites and their mobility within the zeolite framework. Good correlation was found between results obtained in ion-exchange voltammetry and conventional ion-exchange characterization. The advantage of these fundamental studies for electroanalytical purposes was exemplified for the determination of copper(II) ions, using both ZMCPE and ZMGCE, zeolites A, X and Y, and the following analytical scheme: “preconcentration/voltammetric detection”.     

Photochemical studies with a zeolite Y membrane formed via secondary growth

Zeolite membranes offer an attractive feature in design of artificial photosynthetic assemblies because they can keep the charge separated species apart, yet allow for communication between the two sides via the intervening zeolite channels and cages. However, such a strategy would require that the zeolite membrane be pinhole-free. In an earlier paper (J. Phys. Chem. B 106, 11898 (2002)), we have shown that nanocrystalline zeolite Y can be spin-coated on porous substrates to form membranes, and the pinholes can be plugged by a photoresist. Such membranes do not allow manipulation at higher temperatures or even in solution chemistry because of the thermal instability and solubility characteristics of the photoresist. In this paper, we report on a zeolite Y membrane made by the secondary growth method. The growth process leads to minimal pinholes as determined by leak tests. The sturdiness of the membranes allows for manipulation and we have shown that organic reactions can be carried out in the zeolite pores. Charge transport through the membrane by an electron hopping process mediated via self-exchange of ion-exchanged bipyridinium ions are demonstrated. The electron transfer was initiated using a photochemical Ru(bpy)²⁺₃-EDTA system.     

Synthesis and Characterization of the Host-Guest NanocompositeMaterial Zeolite Y-Iron Bipyridine

Zeoliteshavethedefinedcrystallinestructureswiththechannelsorcagesofnanoscaledimensions.Thesechannelsorcagesofzeolitescanoffertheloadingsitestoselfassembleandstabilizetheentrappedguestwithinthezeolitesthatcanbeusedforusefulmatrixestoproducenanoguestsmaterialsl.Becausethiskindofmaterialsshowedsomespecialproperty=,ithasarousedmuchinterest3.Anewfieldofinvestigationfortheentrappedmetalcomplexeshasbeendevelopedinelectro-assistedcatalysisoforganicreaction'.Atpresent,therearethreeapproachestotheprepar…     

A new experimental protocol for intrazeolite photooxidations. The first product-based estimate of an upper limit for the intrazeolite singlet oxygen lifetime

The intrazeolite photooxidations of several alkenes have been examined in hexane and in perfluorohexane slurries. The ability of perfluorohexane to increase the affinity of alkenes for the interior of the zeolite was documented. The nearly identical reaction rates in the two slurry solvents are attributed to a leveling of the singlet oxygen lifetime by the zeolite framework. A consideration of the rates of the various intrazeolite processes was used to estimate an upper limit for the intrazeolite lifetime of singlet oxygen.     

抗坏血酸在铂纳米粒子/碳纳米管/聚吡咯复合修饰电极上的电化学行为

研究了抗坏血酸在铂纳米粒子/碳纳米管/聚吡咯复合膜修饰电极上的电化学行为,发现复合修饰电极对抗坏血酸的电化学反应具有较好的电催化作用,与空白电极相比电化学氧化电流增加了7倍。用电化学阻抗谱研究了电子在修饰电极界面上的传输过程,发现修饰电极的电催化性能与修饰电极可以提高界面电子传输能力是相关的。同时研究了碳纳米管用量、支持电解质、扫速、电沉积条件等因素对抗坏血酸在修饰电极上电化学行为的影响。     

A comparison of intrazeolite and solution singlet oxygen Ene reactions of allylic alcohols

The singlet oxygen ene reactions of four allylic alcohols and for comparison an allylic ether have been examined both in solution and in zeolite Y. Brønsted acid sites in the zeolite were shown to induce decomposition of several of the allylic alcohols. Treatment of the zeolites with pyridine removed these acid sites and allowed intrazeolite reactions of the allylic alcohols without interference from decomposition. Control reactions with an allylic alcohol that is inert to decomposition provided evidence that the presence of pyridine in the zeolite labyrinth does not influence the product composition.     

A study on the photophysical properties of anthracene in zeolite

The photophysical behaviours of anthracene in zeolite Y were investigated using various steady state spectroscopic methods and a picosecond time-resolved fluorescence spectroscopic technique. A ¹²⁹Xe nuclear magnetic resonance (NMR) study shows that anthracene molecules can be optimally intercalated into the supercages of Na⁺- and Cu²⁺-exchanged zeolite Y at 570 and 520 K respectively. Anthracene introduced into the supercage of Na⁺-exchanged zeolite Y shows excimeric fluorescence with a lifetime of several nanoseconds, as well as monomeric fluorescence with a lifetime of 300 ps. The excimer forms immediately on absorption of a photon. Cu²⁺-exchanged zeolite Y with anthracene intercalation shows electron spin resonance (ESR) signals and absorption bands attributable to the stable, ground state anthracene cation radical, the Cu⁺ ion and the trapped electron in the copper ion cluster, indicating charge transfer from anthracene to the Cu²⁺ ion or copper ion cluster. The excitation energy of anthracene is quenched rapidly by the presence of copper ion.     

Electrochemistry of zeolites on thickness shear mode oscillators

This paper describes electrochemical studies of thickness shear mode (TSM) acoustic wave oscillators coated with zeolites. The frequency response of gold on AT-cut 9 MHz quartz oscillators of silver-ion-exchanged zeolite-modified electrodes (ZMEs) under an electrochemical bias is interpreted. This is achieved using a combination of cyclic voltammetry, double-potential-step chronocoulometry (DPSC), and the frequency and resistance responses of the quartz crystal oscillators. Three ZMEs were investigated including fully exchanged Ag(12)A plus partially exchanged Ag(6.4)A and Ag(3.5)A. In all cases, the frequency response of the quartz crystal nanobalance (QCN) could only be interpreted when motional resistance changes were considered. This determines the importance of energy storage and energy dissipation of the shear wave produced by the oscillator in the zeolite film, which was affected by the deposition of silver at the zeolite-electrode-solution interface. The silver deposit formed via the reduction of silver ions originally within the zeolite phase mechanically couples the zeolite film to the underlying substrate. The resistance changes occurring during redox are thus linked to an inner interfacial slip between the zeolite film and the underlying oscillating surface. The data presented are consistent with an extrazeolite redox mechanism.     

Dye-sensitized intrazeolite photooxygenation of 4-substituted cyclohexenes. Remote substituent effects in regioselectivity and diastereoselectivity

The product distribution in the dye-sensitized photooxygenation of α-terpinyl acetate and terpinen-4-ol is quite similar in solution, however, by zeolite Y confinement, is substantially influenced by the position of the remote polar substituents relative to the reacting double bond. The intrazeolite results were rationalized in terms of Na⁺-substrate and Na⁺-singlet oxygen interactions.