硒杂环化合物(4,5-苯并苤硒脑)在金表面上的自组装

为了寻求新的自组装单分子膜体系 ,构建新的功能膜 ,研究了具备平面型的大环共轭硒杂环化合物——— 4,5 苯并苤硒脑 (苯并 [c]硒二唑 ,简称苤硒脑 )在金表面的自组装单分子膜 .通过X射线光电子能谱 (XPS)和电化学手段对其进行表征 .XPS研究结果表明 ,自组装形成单分子膜后 ,苤硒脑分子中Se3d结合能从 5 7.4eV下降到 5 7.1eV ;表明硒杂环化合物是通过金硒键固定在金表面上的 ;电化学循环伏安法实验表明 ,金电极表面上自组装该有机硒后 ,Fe(CN) 63 -/ 4 -的氧化还原峰几乎完全消失 ;以四硼酸钠为底液 ,测得该化合物自组装在金表面上时 ,其还原电位在 - 0 .6 6V ,与在溶液中用裸金电极测得的还原峰电位基本一致 .     

电位平均SERS技术研究二巯基嘧啶与银电极的作用

采用电位平均表面增强拉曼散射(PASERS)新方法研究二巯基嘧啶(2MP)在不同电极电位下与银电极的作用,PASERS 谱的获得是在快速调制两个电极电位的同时记录 SERS 谱。研究表明2MP在—1.1V 以正的电极电位下,通过硫原子以竖立方式作用于银电极表面,在—1.1V 以负的电位下发生电化学还原反应。     

铁电极表面拉曼光谱的初步研究

本文成功地把表面 Raman光谱研究拓宽到重要的过渡金属之一的铁电极上。实验尝试了多种粗糙处理方法 ,如 :化学刻蚀、现场和非现场电化学氧化还原等法对铁电极表面进行处理 ,并首次获得吸附在粗糙铁电极上的吡啶分子的高质量表面拉曼光谱。经过比较发现表面拉曼光谱信噪比的提高与电极表面粗糙度有很大的关系 ,合适的表面粗糙度极有可能诱导出弱的表面增强拉曼散射效应     

对苯醌电化学还原的原位傅里叶变换红外反射光谱的研究

利用傅里叶变换红外光谱法原位记录了对苯醌在Pt电极上还原产生的自由基阴离子的红外光谱,并对自由基阴离子的可能结构进行了初步讨论。这种技术被用于在电化学体系中获取反应中间物和电极表面吸附物的红外差示谱,是一种非常灵敏的光谱电化学技术。     

表面增强喇曼散射(SERS)光谱中影响增强效应因素的实验研究

本文研究了银电极表面的电化学预处理、电极的外加电位和放在卤化物溶液中的银电极在电化学预处理过程中的激光辐照对喇曼光谱表面增强效应的影响。实验结果表明,银电极的电化学预处理有利于吡啶分子的吸附;银电极的外加电位和激光辐照使得吡啶分子吸附于粗糙银电极表面。最后,定性地讨论了电化学预处理,外加电位和激光辐照影响喇曼光谱表面增强效应的实验结果。     

电化学超级电容器电极材料的研究进展

超级电容器是一种利用电化学双电层储能或在电极材料表面及近表面发生快速可逆氧化还原反应而储能的装置,具有高的比功率、比能量和长的循环寿命.文章综述了超级电容器电极材料的储能机理、特点及应用,并重点介绍了石墨烯、二氧化锰及其复合电极材料在超级电容器中应用的最新研究进展.     

纯钛电极上的表面增强拉曼光谱研究

采用机械粗糙、电化学氧化还原、化学刻蚀等方法对纯钛电极表面进行粗糙,在钛基底上获得了表面增强拉曼光谱(SERS)信号。初步的实验结果表明,采用机械粗糙和电化学氧化还原方法能够获得具有一定粗糙度的电极表面,但是该表面并不具有SERS活性。而采用氢氟酸化学刻蚀方法能够获得具有SERS活性的表面,并且成功检测到吡啶分子的表面增强拉曼信号。实验尝试了在不同条件下进行刻蚀,对酸的刻蚀浓度、刻蚀时间、外接电位等影响因素作了研究,结果发现基底的SERS活性随氢氟酸浓度增大而出现最佳条件,即氢氟酸浓度0.33 Wt%,刻蚀时间为5 min时的拉曼信号最好。实验以0.01 mol·L-1吡啶为探针分子,0.1 mol·L-1 KCl为电解质,在开路电位下成功地观察了钛电极上的表面增强拉曼光谱。     

2,3-二巯基丁二酸在银表面的电化学表面增强拉曼光谱及电还原特性

采用原位电化学表面增强拉曼光谱(EC-SERS)和电化学还原方法,研究了内消旋-2,3-二巯基丁二酸(DMSA)在活化的银电极上的吸附行为。通过模型分子DMSA进行结构优化的密度泛函理论计算,得到了理论拉曼光谱。在相同的DMSA自组装时间条件下,其在Ag电极表面的覆盖度倒数与溶液浓度倒数成线性关系,说明DMSA单分子层在活性Ag表面的化学吸附遵循Langmuir等温吸附模型。在酸性介质中,DMSA浸置自组装50 min后,SERS峰强趋于稳定,达到了该浓度下的动态吸附平衡。EC-SERS信号随施加电位的负移逐渐减弱至基本消失。通过计算探针分子DMSA在不同电位下的增强因子(EF),指出较负电位下存在着还原/脱附作用,使得Ag表面的拉曼活性降低,尤其在小于-0.4 V的还原电位时,增强因子显著减小。     

ω-巯基己酸自组装修饰金电极及其对叶绿素的催化氧化还原作用

用自组装技术以ω－巯基己酸（６－ＭＨＡ）对金电极进行修饰。通过表面增强拉曼散射（ＳＥＲＳ）光谱和电化学方法研究了６－ＭＨＡ自组装单分子膜（ＳＡＭ）在金电极表面的形成及由此引起的电极双电层电容的变化,并研究了该自组装单分子膜的结构模型及修饰电极对叶绿素的催化性能。结果表明,６－ＭＨＡ在金电极表面能够形成一层自组装膜,并对叶绿素的氧化还原过程具有明显的催化作用。     

3,3′,5,5′-四甲基联苯胺—β-环糊精包合物的紫外-可见光谱和电化学研究

本文采用紫外 可见光谱和电化学的方法研究了 3,3′,5 ,5′ 四甲基联苯胺 (TMB)和 β 环糊精形成超分子包合物后的氧化还原性质 ,研究结果表明在形成包合物后TMB的氧化还原特性更好 ,尤其是在有酶参与时更易被氧化。在包合物内的氧化产物组分更单纯 ,修饰在电极表面也表现出更好的氧化还原活性。     

Fourier transform infrared studies of cyclohexane and benzene adsorbed on Pt/Al2O3: Evidence for π- and σ-bonded chemisorbed species

Fourier transform infrared spectroscopy has been applied to the study of cyclohexane adsorbed on Al₂O₃ and Pt/Al₂O₃ surfaces. Earlier studies of benzene on these same materials have also been extended to include benzene adsorbed on a Pt/Al₂O₃ surface which contains structured carbon residues. The data provide indirect evidence for the formation of a carbon residue on Pt/Al₂O₃ which retains the six-membered cyclic structure of the parent adsorbates. The carbon residue can be formed upon vacuum heating of the parent C₆ ring molecules chemiorbed on Pt/Al₂O₃. There is spectroscopic evidence that cyclohexane dehydrogenates on Pt/Al₂O₃ at 300 K to form two different chemisorbed species; a π-bonded benzene and a dissociated σ-bonded benzene. These two chemisorbed species have CH stretching vibrations centered at 3030 and 2947 cm^?1, respectively. Benzene added to a clean catalyst surface forms only a π-bonded benzene. However, benzene added to Pt/Al₂O₃ with ordered carbon residues forms both π- and σ-bonded benzenes. The addition of H₂ at 300 K to any of the π- or σ-bonded benzenes or to the carbon residue results in the formation of cyclohexane physisorbed on the catalyst. The absence of CH₃ groups upon hydrogenation suggests the lack of CC bond breaking during adsorption or hydrogenation. Simultaneous infrared and thermal desorption studies on chemisorbed deuterated benzene (from C₆D₁₂) indicate that the a-bonded species exchange H from the surface OH groups of the alumina support more readily than does the π-bonded benzene. In addition to hydrogen exchange with the support, thermal desorption experiments indicate the oxidation of a portion of the chemisorbed hydrocarbons and/or carbon residue by oxygen from the alumina support. Therefore, the support is capable of playing a direct role in reactions occurring on the catalyst surface.     

N，N－二甲基苯胺~1H核磁共振溶剂效应的研究

本文研究了Ｎ，Ｎ－二甲基苯胺分子在环已烷和苯混合溶剂中的１ＨＮＭＲ谱的溶剂效应，观察到Ｎ，Ｎ－二甲基苯胺分子内的两个甲基和混合溶剂中的苯、环己烷的化学位移随苯的摩尔分数增加而逐渐移向高场，ＡＳＩＳ值随苯的摩尔分数增加而增加。得到了所有化学位移值和ＡＳＩＳ值与苯的摩尔分数呈线性关系；尝试用溶剂化作用解释了苯对Ｎ，Ｎ－二甲基苯胺的ＡＳＩＳ效应。     

苯在铂电极上溴代反应的共焦显微拉曼光谱研究

本文主要利用共焦显微拉曼技术检测KBr溶液中苯在光滑铂电极上的取代反应。结果表明 ,苯在 1 2V时将和溴离子在氧化产生的溴自由基发生溴代反应 ,与氯代反应相比 ,溴代反应更剧烈、产物更复杂、更容易受光照影响     

咪唑在铜电极上吸附行为的SERS研究

咪唑在铜电极上吸附行为的ＳＥＲＳ研究张传飞，徐知三，旷富贵，王小华，刘海林（武汉大学分析测试中心武汉４３００７２）（武汉大学环境科学系武汉４３００７２）ＳｔｕｄｙｏｎＴｈｅＡｄｓｏｒｐｔｉｏｎＢｅｈａｖｉｏｕｒｏｆＩｍｉｄａｚｏｌｅｏｎＣｏｐｐｅｒＥ...     

Sound velocity in binary liquid mixtures and the statistical mechanical theories

Sound velocity in three binary liquid mixtures benzene+cyclohexane (I), cyclohexane+carbontetrachloride (II) and benzene+carbontetrachloride (III) has been measured. Significant structure and Flory — Patterson theories have been employed to evaluate ultrasonic velocity in the systems. The values are in good agreement with the experimental ones. A comparative study of significant structure theory and Flory-Patterson Theory has been made. Both the theories give satisfactory results for the three liquid mixtures.     

Ultrafast experiments on intermolecular electron transfer in the benzene - bromine atom charge transfer complex

Ultrafast pump - probe measurements have been made on the benzene - bromine atom charge transfer (CT) complex in CCl₄ and cyclohexane solutions. Ultrafast optical excitation of the CT band of the complex yields an ion pair, which is comprised of a benzene cation and a bromide anion. The rate of charge recombination between the bromide and the benzene cation in the ion pair has been observed to be much faster than the rate of diffusion apart. The charge recombination rate is accelerated at high benzene concentrations as a result of the formation of a benzene dimer cation - bromide ion pair which undergoes much faster charge recombination than the benzene cation - bromide ion pair.     

Ultrasonic study on binary liquid mixtures between some bromoalkanes and hydrocarbons

Densities and ultrasound velocities for the binary mixtures of 1-bromobutane+benzene and 1,4-dimethylbenzene and of 1-bromopentane+cyclohexane and benzene have been measured at 308.15 K. Adiabatic compressibilities (beta(ad)), and Wada's constants (W) have also been evaluated as a function of composition. The ultrasound velocities decrease, attains a minimum and then increase with increase in mole fractions of hydrocarbons in the binary mixtures except in the case of 1-bromopentane+benzene binary mixtures where the variation is just the reverse. Dependence of adiabatic compressibilities with mole fractions of hydrocarbons is sigmoid. The non-ideal behaviour of the systems studied is explained on the basis of dipole-induced dipole interactions.     

Ultrasonic absorption in binary liquid mixtures

Ultrasonic absorption in binary liquid mixtures containing benzene, chloroform, cyclohexane and toluene with triethylamine, a rotational isomeric relaxing liquid, as a common component has been studied at a frequency of 7.56 MHz. A pulse techrique has been used for the measurement of absorption with an accuracy of ±5%. Bauer-Sette formula has been used to calculate the absorption of these liquid mixtures at different concentrations. The theoretical values evaluated on the basis of Bauer-Sette theory appear to have good agreement with experimental values. In view of the discrepancy pointed out by Mallikarjuna Rao and Suryanarayana, the mixtures of benzene and ethylacetate have been studied in this context and found the theoretical values coinciding with experimental values.     

Benzene formation during aquasonolysis of selected cyclic C6Hx hydrocarbons

Yield and selectivity of benzene produced from aquasonolysis of the selected cyclic C6Hx hydrocarbons, i.e., 1,4-cyclohexadiene, 1,3-cyclohexadiene, cyclohexene, cyclohexane, and methylcyclopentane, have been investigated in this work. Benzene cannot be detected during the aquasonolysis of cyclohexane and methylcyclopentane. The order of yield and selectivity of benzene was as follows: 1,4-cyclohexadiene>1,3-cyclohexadiene>cyclohexene. The initial concentrations of substrates can affect the yield of benzene. During the aquasonolysis of 1,3-cyclohexadiene and cyclohexene, other C6 species except benzene were also found. It was suggested that benzene could directly be generated by formal dehydrogenation of cyclic C6Hx hydrocarbons.     

LEED,AES and thermal desorption studies of chemisorbed Hydrogen and hydrocarbons (C2H2, C2H4, C6H6, C6H12) on the (111) and stepped [6(111) × (100)] iridium crystal surfaces; comparison with platinum

The adsorption of hydrogen, ethylene, acetylene, cyclohexane and benzene was studied on both the (111) and stepped [6(111) × (100)] crystal surfaces of iridium. The techniques used were low energy electron diffraction, Auger electron spectroscopy, and thermal desorption mass spectrometry. At 30°C, acetylene, ethylene and benzene are adsorbed with a sticking probability near unity. The sticking probability of cyclohexane is less than 0.1 on both surfaces. Heating the (111) surface above 800°C, in the presence of the hydrocarbons, results in the formation of an ordered carbonaceous overlayer with a diffraction pattern corresponding to a (9 × 9) surface structure. No indication for ordering of the carbonaceous residue was found on the stepped iridium surface in these experimental conditions. The hydrocarbon molecules form only poorly ordered surface structures on both iridium surfaces when the adsorption is carried out at 30°C. Benzene is the only gas that can be desorbed from the surfaces in large amounts by heating. Ethylene remains largely on the surface, only a few percent is removed by heating while acetylene and cyclohexane cannot be desorbed at all. When adsorption is carried out at 30°C and the crystal is subsequently flashed to high temperature, hydrogen is liberated from the surface. The hydrogen desorption spectra from the iridium surfaces exposed to C₂H₄, C₂H₂, or C₆H₆ exhibit two hydrogen desorption peaks, one around 200°C and the second around 350°C. The temperatures where these peaks appear vary slightly with the type of hydrocarbon. The relative intensities of these two peaks depend strongly on the surface used. Arguments are presented that decomposition of the hydrocarbon molecules (C-H bond breaking nd possibly also C-C bond breaking) occurs easier on the stepped iridium surface than on the (111) surface. Hydrogen is desorbed at a higher temperature from an iridium surface possessing a high density of surface imperfections than from a perfect iridium (111) surface. The results are compared with those obtained previously on similar crystal surfaces of platinum. It appears that C-H bond breaking occurs more easily on iridium than on platinum.