纳米结构钴薄膜电极的制备及其异常红外性能研究

用循环伏安电沉积法在玻碳基底上制备纳米结构钴薄膜, 扫描电子显微镜研究结果表明, 纳米结构钴薄膜主要由平均粒径为150 nm的钴粒子组成, 同时还有为数不多的粒径在400~500 nm的钴粒子. 以CO为探针分子, 结合原位傅里叶变换红外反射光谱研究结果, 发现所制备的纳米结构钴薄膜具有异常红外效应. 吸附态CO发生异常红外吸收, 谱峰增强了26.2倍, 测得线型吸附态COL的Stark系数为77.5 cm-1·V-1.     

钴铂合金薄膜的循环伏安电沉积及其异常红外性能研究

运用循环伏安电沉积在玻碳基底上制得纳米结构钴铂合金薄膜,扫描电子显微镜和X-射线能量散射谱研究表明,钴铂薄膜主要由平均粒经为139 nm的纳米粒子组成,钴和铂的原子比为3:5. 以CO为探针分子,电化学原位FTIR反射光谱研究发现钴铂薄膜具有异常红外效应. 吸附态CO发生异常红外吸收,谱峰比本体钴和铂分别增强了34和43倍.     

银岛膜中银颗粒间表面电磁波的耦合

自从Hartstcil。等人用衰减全反射技术（AT则得到覆盖在银岛膜上的有机超薄膜的表面增强红外吸收光谱以来山，对其增强机理及应用的研究一直是人们关注的热点．人们不论是从实验上还是从理论上都通过种种努力来探索表面增强红外光谱的机理，但仍然没有给出一个清晰的图象．一般     

磺化双酞菁钴自组装膜结构的表面增强拉曼光谱

采用自组装的方法构建了双核磺化酞菁钴轴向配位有序排列的膜层结构. 结合双核磺化酞菁钴分子体系自身所具有的性质及其和桥联分子四巯基吡啶之间相互作用的信息, 对其自组装膜的表面增强拉曼光谱进行了分析, 探讨了其自组装行为, 合理地解释了本自组装体系的膜层结构. 研究结果表明, 双核磺化酞菁钴分子(Bi-CoPc)在这种自组装膜中是以与基底平面存在一定夹角的倾斜的方式排列的.     

表面增强红外吸收光谱——表面敏感的原位免标记光谱电化学技术

表面增强红外吸收光谱（尤其衰减全反射表面增强红外吸收光谱）是一种超灵敏的红外光谱技术,能够实现亚单层膜水平的表面选择性探测. 由于增强基底可同时作为工作电极实现电化学调制,衰减全反射表面增强红外吸收光谱是一种表面敏感的原位免标记光谱电化学技术. 本文首先简要介绍了表面增强红外吸收光谱的基本原理和技术特点,之后通过代表性研究工作着重介绍近年衰减全反射表面增强红外吸收光谱电化学的应用和发展,最后展望了表面增强红外光谱所面临的挑战和潜在的研究方向.     

纳米钯膜电极的制备、结构表征和特殊反应性能

用循环伏安方法制备纳米钯膜电极,运用扫描隧道显微镜和原位红外光谱等方法研究其结构和反应性能.STM图像表明,制备的纳米钯膜具有特殊的层状结构,纳米级厚度的层状晶体由直径6nm左右的Pd微晶聚集而成.发现当钯膜厚度为几个纳米时,CO的吸附表现出异常红外效应,即红外谱峰反向和红外吸收显著增强(增强因子可达42.6).纳米钯膜电极对氢的反应也具有特殊的性能,与氢向钯晶格扩散吸收过程相比较,氢吸脱附的表面过程成为主要反应.研究结果还指出,纳米钯膜电极的异常红外效应和对氢反应的特殊性能与钯膜厚度密切关联,并可归结为钯膜材料的纳米尺度效应.     

金纳米粒子组装体系粒子密度与SERS强度的关系

利用纳米粒子组装技术制备出金基底／巯基苯胺自组装膜偶联层／金纳米粒子的“三明治”结构。实验结果显示,该结构对偶联层分子的喇曼光谱显示出很好的增强效应,增强因子可达１０＾５;在表面粒子密度（粒子覆盖度）较低时,表面增强喇曼散射（ＳＥＲＳ）强度与表面粒子密度近似呈线性关系;随着表面粒子密度的增加,这种线性关系出现负偏差并在表面粒子密度较高区域出现一个平台;在６０￣１１０ｎｍ范围内大粒径金粒子对喇曼光谱     

表面增强喇曼光谱检测卟啉单分子膜

利用轴向配位作用将5,10,15－20－四苯基钴（Ⅱ）卟啉（CoTPP)固定在4－巯基吡啶自组装膜表面上,形成CoTPP单分子膜,通过组装金纳米粒子的方法,成功地获得了膜中CoTPP分子的喇曼光谱。研究结果表明,CoTPP分子是通过钴原子与氮原子之间的配位作用与巯基吡啶分子结合的,且其分子平面与基底表面近似平行。     

Ag_核Au_壳金属复合纳米粒子的制备及表面增强拉曼光谱研究

在已制备好的Ag纳米粒子表面,通过化学还原的方法沉积生长Au包裹层,制备了粒子尺寸为50-70nm的Ag核Au壳复合纳米粒子.通过改变AuCl₄^-量,使Ag_100-xAu_x中Au的含量由x=0变为x=30.用UV-Vis吸收光谱和透射电子显微镜(TEM)对该结构纳米粒子进行了表征,并以对巯基苯胺(PATP)为探针分子进行表面增强拉曼光谱(SERS)研究.表面拉曼光谱表明,该结构的纳米粒子具有比Ag更强的SERS活性,随着Au:Ag比例的逐渐增加,其活性呈现先增大后减小的趋势,其最大增强约为Ag纳米粒子的10倍.     

多孔硅上银纳米粒薄膜的制备及其表面增强红外光谱

通过简便的化学沉积法在多孔硅上制备银纳米粒薄膜用于表面增强红外光谱检测。通过Ag⁺与多孔硅表面的SiHx发生氧化还原反应将银纳米粒子沉积在多孔硅表面。红外探针分子溶解于无水乙醇中进而被均匀分散在多孔硅表面,实验结果显示：对氨基苯硫酚、对氨基苯甲酸和对氟苯硫酚3个探针分子的红外峰分别最大增强了10、85和21倍。银纳米粒的大小和形状等物理特性、探针分子是否有与银表面进行强结合的基团和芳烃结构、以及表面选律等因素影响表面增强红外的吸收效应。     

Surface Area Study of High Area Cobalt Aluminate Particles Prepared by the Sol-Gel Method

Cobalt aluminate particles were prepared by the sol-gel method, starting from aluminum sec-butoxide and cobalt salts with a Co:Al ratio of 1:3. Samples with the same composition were also prepared by the citrate-gel method from cobalt and aluminum nitrates and citric acid. The particles were calcined to temperatures between 400 and 1000°C, for the formation of the mixed oxide having spinel structure. The surface properties of the different samples (BET surface area and pore size distribution) were measured. The highest BET surface area obtained (about 339 m²/g) corresponds to a sample prepared by cobalt acetate and aluminum sec-butoxide, calcined at 400°C. The surface area of the sample is reduced progressively as the sample is calcined to higher temperatures (to about 65 m²/g at 1000°C). Narrow pore size distributions were observed with average pore radius ranging from 17–20 Å, for samples heated to 400°C, to about 55–65 Å, for samples heated to 1000°C. The different surface areas and porosities obtained for particles prepared by different methods, different precursors or calcination temperatures, are discussed.     

Electroless deposition of gold thin films on silicon for surface-enhanced infrared spectroelectrochemistry

Electroless (or chemical) deposition technique has been used in preparing Au island film electrodes on Si for in situ infrared spectroscopic studies of the electrochemical interface in attenuated total reflection mode. Owing to surface-enhanced infrared absorption (SEIRA) effect, absorption bands of molecules adsorbed on the chemically deposited films were one order of magnitude as large as those observed on smooth Au electrode surfaces. Although the enhancement factor was identical to that observed on vacuum evaporated Au island films, this simple method is superior to vacuum evaporation method with respect to the adhesion of the film, surface contamination, reproducibility, and cost.     

1-Dodecanethiol self-assembled monolayers on cobalt

Cobalt and its alloys are used in a broad range of application fields. However, the use of this metal is especially limited by its strongly oxidizable nature. The use of alkanethiol self-assembled monolayers (SAMs) is a very efficient way to protect against such oxidation and/or to inhibit corrosion. This surface modification method has been particularly applied to oxidizable metals such as copper or nickel, yet the modification of cobalt surfaces by alkanethiol SAMs received limited attention up to now. In this work, we study the influence of parameters by which to control the self-assembly process of 1-dodecanethiol monolayers on cobalt: nature of the surface pretreatment, solvent, immersion time, and concentration. Each of these parameters has been optimized to obtain a densely packed and stable monolayer able to efficiently prevent the reoxidation of the modified cobalt substrates. The obtained monolayers were characterized by X-ray photoelectron spectroscopy (XPS), polarization modulation infrared reflection-absorption spectroscopy, and contact angle measurements. The stability of the optimized 1-dodecanethiol monolayer upon air exposure for 28 days has been confirmed by XPS.     

Promoting effect of doped cobalt on catalysis of SiO2-supported rhodium for propylene hydroformylation

According to infrared spectroscopy and temperature programmed reduction (TPR), doped Co^o to Rh^o/SiO₂ can play an electron-donating role and prevent the oxidation of Rh^o by surface OH⁻. The interaction between monometallic cobalt and rhodium particles which are probably in close contact results in a strong enhancement of catalytic propylene hydroformylation.     

Nanophase cobalt, nickel and zinc ferrites: synchrotron XAS study on the crystallite size dependence of metal distribution

Nanophase cobalt, nickel and zinc ferrites, in which the crystallites are in the size range 4-25 nm, were synthesised by coprecipitation and subsequent annealing. X-Ray absorption spectroscopy using synchrotron radiation (supported by X-ray powder diffraction) was used to study the effects of particle size on the distributions of the metal atoms over the tetrahedral and octahedral sites of the spinel structure. Deviations from the bulk structure were found which are attributed to the significant influence of the surface on very small particles. Like the bulk material, nickel ferrite is an inverse spinel in the nanoregime, although the population of metals on the octahedral sites increases with decreasing particle size. Cobalt ferrite and zinc ferrite take the inverse and normal forms of the spinel structure respectively, but within the nanoregime both systems show similar trends in being partially inverted. Further, in zinc ferrite, unlike the normal bulk structure, the nanophase system involves mixed coordinations of zinc(ii) and iron(iii) consistent with increasing partial inversion with size.     

Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film

Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8 V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co²⁺ concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3 V for 40 s in pH 4.6 acetate buffer containing 10 mM Co(NO₃)₂, possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1 mg L⁻¹. The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method.     

Influence of local structure on local electric field in Island‐like silver films

The infrared absorption enhancement phenomenon in the normal configuration of vacuum‐evaporated metal films on a transparent substrate is known to depend not only on the metal film morphology but also on the local structures of metal particles. To date, however, few studies have examined the effect of local structure on the phenomenon. Size distributions of islands and gaps, along with the volume fractions of Ag in thin films, were measured using scanning electron microscopy as a function of film thickness. The local structure of Ag nano clusters deposited on silicon substrates was investigated using a total conversion electron yield X‐ray absorption fine structure (XAFS) method at the Ag K‐edge. We observed a correlation between the electromagnetic field intensity at the surface as evaluated by IR measurement and the coordination numbers evaluated by XAFS. We found that the film morphology had a greater effect on resonant and nonresonant contributions than did the local structure of a particle. Copyright © 2006 John Wiley & Sons, Ltd.     

Cathodic etching for fabrication of super-hydrophobic aluminum coating with micro/nano-hierarchical structure

A facile method for fabricating super-hydrophobic surfaces on the magnetron sputtering aluminum film by cathodic electrochemical etching followed by the modification of myristic acid was presented in this article. The morphologies and the compositions of the films were characterized by means of scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), respectively. The corrosion behavior of the super-hydrophobic film was evaluated by potentiodynamic polarization measurement, linear polarization measurement, and electrochemical impedance spectroscopy. After the treatment with cathodic electrochemical etching, the thin aluminum film remained unbroken and the bulk structure of the aluminum coating maintained a microcrystalline morphology while the surface of the coating presented a petal-shaped microstructure dotted with nano-sized floccules. Aluminum myristate was formed on the nano/microstructural surface of the coating when the sample was modified in melting myristic acid. The static water contact angle on the surface was larger than 165°, which demonstrated that a super-hydrophobic film was prepared on the magnetron sputtering aluminum coating. The corrosion resistance of the aluminum coating was enhanced remarkably because of the super-hydrophobic modification.