含酰胺结构的巯基自组装膜的设计与结构表征

提出了一种简便通用的合成巯基化合物的途径，以分子中的羧基CO2H为起始基团，与2-流基乙胺的氨基选择性缩合；合成了一系列具有RC（O）NHCH2CH2SH（R分别为偶氯苯衍生物，双炔衍生物及直链烷基）结构的化合物，并用接触角测量，电化学和掠角反射红外光谱（GIR-IR）等手段对这些化合物在金表面形成的自组装单分子膜进行了表征。发现4-（N－（2‘-巯基已基））酰胺偶氮苯的自组装膜表现出良好的电活性，电化学测定表面浓度为4．21×10(－10)mol·cm(-2)．当R为烷基链时，随烷基链的增长，膜的致密度与有序度增加GIR-IR证明在自组装腹中CH3（CH2）6C（O）NHCH2CH2SH的C＝O和N－H键与Au表面平行，分子轴线与Au表面近似垂直．     

偶氮苯衍生物-β-环糊精包合物的自组装行为

研究了4-N（2’-巯基-乙基）羧基酰胺偶氮苯（Azo）与β-环糊精（β-CD）形成的包合物在金表面上的自组装行为．X射线光电子能谱（XPS）结果证实,Azo和Azo与β-CD形成的包合物均可在金表面上自组装形成单分子层膜．在包合物形成的自组装膜中,Azo与β-CD的摩尔比约为1：1．Azo自组装膜的电化学反应表现速率常数（Kobs）随组装时间的延长而明显减小,反映出自组装膜的排列随时间延长而趋于更加致密,从而抑制了偶氮苯基团的电化学诱导构型转化,降低了其电活性．而Azo与β-CD包合物自组装膜的Kobs值随组装时间变化不大,在组装76h以后,包合物自组装膜的Kobs比单纯偶氮苯自组装膜的Kobs高2个数量级以上．表明环糊精能够将偶氮苯分子隔开,从而抑制了偶氮苯在自组装膜中的聚集作用,有效地提高其电化学活性．     

金表面偶氮苯自组装膜的光电化学响应

金表面偶氮苯自组装膜的光电化学响应王永强，王健，于化忠，蔡生民，刘忠范（北京大学化学与分子工程学院智能材料研究中心，北京，１００８７１）关键词偶氮苯，自组装膜，光致异构化，电化学偶氮苯基团特征的光致异构化及电化学响应在分子开关器件和超高密度信息存储等...     

自组装膜结构与电化学行为的关系

报导了组装时间对４－乙氧基－４＇－Ｎ（２″－巯基－乙基）羧基酰胺－偶氮苯（Ｃ２ＡｚｏＣ２）自组装膜电化学行为的影响。接触角与界面电容的数据表明，组装时间的增长使自组装膜表面覆盖度增加。从循环伏安图中可以观察到氧化峰与还原峰之间的距离增大，同时计算得到的表观电极反应速率常数显著减小。基于偶氮苯基团的自身结构及其在电化学反应过程中所经历的构型改变，认为有序体系中组装结构的致密性阻碍偶氮苯基团的构型变化     

新型偶氮苯自组装一LB组合有序膜的构造与表征

偶氮兹及其衍生物具有独特的光致异构化和电化学反应机制,其LB单分子膜作为一种高度有序的分子组装体系,以其诱人的应用前景引起了人们的极大兴趣．然而在这方面的研究中,LB膜通常是沉积在SnO。或镀金的基片上,其结构的相对木稳定性限制了实际应用的可能性．我们利用自组装技术,在金基底表面组装了具有特定末端基团的自组装单分子膜,然后利用LB技术构造偶氮苯衍生物的单分子膜,以期得到稳定而有序的偶氮苯LB膜,且不影响其光化学和电化学活性．本文报道了这种新型偶氮苯自组装一LB组合股的结构表征及其电化学行为．亚实验部分偶…     

偶氮苯自组装单分子膜中长程电子转移机理

利用自组装技术在金电极表面构造了具有不同前端健长度偶氮苯功能化的单分子膜体系：Au／S（CH2）nNHCO-N＝N-OCH2CH3（n＝2，3，4，6）．研究结果表明，仍氮苯到金电极的表现电子转移速率随它们之间的距离长度的增加而呈指数性的下降趋势．基于Marcus电子隧穿理论，得到了此自组装膜体系的长程电子隧穿系数ρ＝（1．35±0．2）／CH2在和可逆电活性分子自组装膜体系及理论计算相比较的基础上，从偶氮苯分子自组装膜结构与电子转移过程的关系角度对这一结果进行了分析和说明．     

席夫碱自组装单分子膜的电化学行为

利用自组装技术将席夫碱硫醇衍生物在金表面形成自组装单分子膜,并初步研究了此自组装单分子膜的电化学行为,发现该席夫碱分子在0.1 mol•L－1的KCl溶液中具有电化学不可逆氧化还原行为，且随着自组装时间的增加表观电极反应速率常数值显著减小,最后减小为0,并对此进行了解释.     

一种新型C60-硫醚衍生物分子在金表面上的自组装

报导了一种新型C60 硫醚分子在金表面上自组装膜的形成,并通过接触角、扫描隧道显微术（STM）、X射线光电子能谱（XPS）、电化学和光电化学手段对其进行表征.高分辩STM形貌图证明,在Au(111)基底上C60基团存在并直观显示出特殊的单层膜结构. XPS分析表明,这一新型C60 硫醚分子是通过金硫键固定在金表面上的,并且在组装过程中存在分子内碳硫键断裂步骤.     

化学吸附自组装偶氮苯小分子单层膜及表面浸润性研究

通过化学吸附自组装的方法, 将小分子量的偶氮苯分子自组装到平滑硅基底表面, 其表面接触角为83.7°. 微结构化硅基底表面的偶氮苯单层膜上表现出超疏水的特性, 接触角达到了151.9°. 经过紫外光照射后, 该表面的接触角没有发生明显的降低.     

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57.4 eV下降到57.1 eV;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-0.66 V,与在溶液中用裸金电极测得的还原峰电位基本一致.     

Contact-Angle Titrations of Cysteamine Selfassembled Monolayers on Gold--A Sensitive Tool for Monitoring the Surface Modification Process

The self-assembled monolayers (SAMs). which were prepared by spontaneous adsorption of cysteamine on gold surface, were characterized using contact-angle titrations. Contact-angle titration data acquired for the cysteamine SAMs exhibited a smooth transition in contact angle between plateau regions at low and high pH value. The surface pK_b, was estimated to be 1.8±0.2, much lower than that in solution. The electroactive azobenzene group was anchored to the monolayer via amide surface reaction. Thus the formed SAMs were further subjected to exchange in dilute pentanethiol soluition. At each stage of modification, the surface was monitored by con-tact-angle titration and cyclic voltanimetry. It was found that the titration curves obviously shifted to the higher contact-angle direction with the increase of surface hydrophobicity. The results are in good agreement with the cyclic voltammetric measurements, demonstrating that the contact-angle titration is a useful technique for monitoring the step by step surface reactions.     

Influence of alkyl chain length on the structure of dialkyldithiophosphinic Acid self-assembled monolayers on gold

We report the formation and characterization of self-assembled monolayers (SAMs) based on dialkyldithiophosphinic acid adsorbates {[CH(3)(CH(2))(n)](2)P(S)SH (n = 5, 9, 11, 13, 15)} on gold substrates. SAMs were characterized using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact angle measurements, and electrochemical impedance spectroscopy. Data show that there is a roughly 60:40 mixture of bidentate and monodentate adsorbates in each of these SAMs. The presence of monodentate adsorbates is due to the numerous and deep grain boundaries of the underlying gold substrate, which disrupt chelation. Comparing the characterization data of dialkyldithiophosphinic acid SAMs with those of analogous n-alkanethiolate SAMs shows that both SAMs follow a similar trend: The alkyl chains become increasingly organized and crystalline with increasing alkyl chain length. The alkyl groups of dialkyldithiophosphinic acid SAMs, however, are generally less densely packed than those of n-alkanethiolate SAMs. For short alkyl chains (hexyl, decyl, and dodecyl), the significantly lower packing densities cause the alkyl chains to be liquid-like and disorganized. Long-chain dialkyldithiophosphinic acid SAMs are only slightly less crystalline than analogous n-alkanethiolate SAMs.     

Study on self-assembled monolayers of functionalized azobenzene thiols on gold: XPS,electrochemical properties,and surface-enhanced Raman spectroscopy

Self-assembled monolayers (SAMs) of 4-acetamino-4'-(4-mercaptobutoxy)azobenzene (CH3)CONH-ph-N=N-ph-O(CH2)(4)SH, abbr. aaAzoC4SH) and 4-mercaptobutoxy azobenzene (ph-N=N-ph-O(CH2)(4)SH, abbr. AzoC4SH) on a gold surface have been studied by X-ray photoelectron spectroscopy (XPS), FT Raman spectroscopy, and electrochemistry. A surface-enhanced Raman scattering (SERS)-active system with a "sandwiched" structure of Ag/R-Azo-C4S-/Au was conveniently obtained by the method of Tollen's test. The relationship between the SERS effect and the structural nature of the system indicates that the enhancement correlates to both the silver islands above and the gold substrate underneath. The redox behaviors of the self-assembly on gold electrodes showed that the SAMs of the two compounds exhibit well-behaved voltammetric responses in a Britton-Robinson buffer corresponding to the irreversible two-electron, two-proton reduction-oxidation of azobenzene. The apparent electron-transfer rate kinetics is very sluggish, and the rate constant k(app) of aaAzoC4SH/Au (1.34 x 10(-6) s(-1)) is lower than that of AzoC4SH/Au (1.63 x 10(-4) s(-1)), which may be attributed to the different spatial restriction of close-packing structures on the conformational change accompanied by electron and proton transfer in the SAMs.     

The effect of the surface coverage of the phosphonic acid terminated self-assembled monolayers on the electrochemical behavior of dopamine

The surface coverage of 3-mercaptopropylphosphonic acid (HS-CH₂CH₂CH₂-PO₃H₂, MPPA) self-assembled monolayers (SAMs) on gold surface can be controlled by the dissociation degree of phosphonic acid groups (-PO₃H₂) in the bulk solution and adsorption time of MPPA molecules under the basic condition. Electrochemical measurements show that the low-density MPPA-SAMs modified gold electrode enhances significantly the kinetics of electron transfer of dopamine (DA), and improves the antifouling capability of modified electrode towards DA oxidation. The present results offer crucial information for design and optimization of the electrochemical sensors for DA determination.     

Inhibition of copper corrosion by self-assembled monolayers of triazole derivative in chloride-containing solution

The self-assembled monolayers (SAMs) derived from 3-undecane-4-amino-5-mercapto-1,2,4-triazole (UAMT) on copper surface have been characterized by contact angle test, X-ray photoelectron spectroscopy, and electrochemical techniques. It is found that the UAMT molecules can spontaneously adsorb to copper surface to form compact and oriented monolayers, which can prevent the corrosion of copper in chloride-containing solution effectively. The electrochemical measurements prove that the adsorption of UAMT molecules on copper surface typically processes with a two-step adsorption consisting of a fast initial adsorption and a slowly following reorganization in 10^?4-M UAMT solution, and the adsorption of UAMT obeys the Langmuir model in the initial adsorption process. Furthermore, the effects of the immersion time, ultrasonic irradiation, and UAMT concentration on the anticorrosion property of SAMs are studied, and the adsorption isotherm of UAMT on copper is followed.     

Modification of gold electrode by self-assembled 2-mercapto benzothiazole for the determination of Hg2+

An electrochemical method was developed for the determination of mercury using polycrystalline gold electrode modified by self-assembled monolayers (SAMs) of 2-mercaptobenzothiazole (MBTH). Morphological and electrochemical characterisation of the self-assembled structure of MBTH was performed using atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements. The monolayer of MBTH has shown high affinity for Hg²⁺. The limit of detection for the determination of Hg²⁺ using the MBTH SAMs modified gold electrode was obtained as 0.421 μg L^?1. The pre-concentration of Hg²⁺ at open circuit potential is beneficial for the onsite monitoring of mercury concentration in water samples.     

Self-assembly and multistage redox chemistry of strong electron acceptors on metal surfaces: polynitrofluorenes on gold and platinum

Nitrofluoren-9-one and nitrofluoren-9-dicyanomethylene electron acceptors 7, 8, and 11 functionalized with a terminal thioctic acid unit have been synthesized from 2,4,5,7-tetranitrofluorenone. The self-assembled monolayers (SAMs) of these compounds on gold, formed via gold-sulfur interaction, have been fully characterized by electrochemical, FTIR, ellipsometry, and contact angle measurements. Cyclic voltammetry of SAMs reveals two reversible single-electron reduction waves for fluorenone derivatives 7a,b and 11, and three single-electron reductions for the dicyanomethylene-fluorene 8b, providing the first observation of a radical trianion species in SAMs. The tendency of the thioctic anchor to form multilayers via disulfide links is noted.     

Electroactive dipyrromethene-Cu(II) self-assembled monolayers: complexation reaction on the surface of gold electrodes

In the work presented, thiol- and COOH-terminated dipyrromethene derivatives have been applied for gold electrode modification. Dipyrromethene deposited onto a solid support, after binding Cu2+, can act as a redox active monolayer. The complexation of Cu(II) ions has been performed on the surface of gold electrodes modified with dipyrromethene. The characterization of dipyrromethene-Cu(II) self-assembled monolayers (SAMs) has been done by cyclic voltammetry (CV), wettability contact angle measurements, and atomic force microscopy (AFM). The new electroactive monolayer could be applied for the immobilization of proteins and ssDNA or for electrochemical anion sensing without redox markers in the solution.     

Formation of ordered self-assembled monolayers by adsorption of octylthiocyanates on Au(111)

Self-assembled monolayers (SAMs) were formed by the spontaneous adsorption of octythiocyanate (OTC) on Au(111) using both solution and ambient-pressure vapor deposition methods at room temperature and 50 degrees C. The surface structures and adsorption characteristics of the OTC SAMs on Au(111) were characterized by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The STM observation showed that OTC SAMs formed in solution at room temperature have unique surface structures including the formation of ordered and disordered domains, vacancy islands, and structural defects. Moreover, we revealed for the first time that the adsorption of OTC on Au(111) in solution at 50 degrees C led to the formation of SAMs containing small ordered domains, whereas the SAMs formed by vapor deposition at 50 degrees C had long-range ordered domains, which can be described as (radical3 x 2 radical19)R5 degrees structures. XPS measurements of the peaks in the S 2p and N 1s regions for the OTC SAMs showed that vapor deposition is the more effective method as compared to solution deposition for obtaining high-quality SAMs by adsorption of OTC on gold. The results obtained will be very useful in understanding the SAM formation of organic thiocyanates on gold surfaces.     

偶氮苯硫醇衍生物自组装成膜过程考察

The formation kinetics of the self-assembled monolayer (SAM) of an azobenzenealkanethiol, denoted as AzoC2SH on surface was studied using electrochemical techniques, and the monolayers prepared at different assembly times and concentration were also investigated. A two-step adsorption kinetics has been confirmed: the fast adsorption process and the following long-term reorganization. The equilibrium constant(K)for the adsorption and the interaction factor between adsorbate-adsorbate molecules (δ) were evaluated based on the Frumkin isotherm and determined to be (3. 17±0. 13)× 106 mol•L(-1) and -0.34±0.04, respectively. The Gibbs free energy (G)of SAM was determined to be -(37. 07±0. 13)kJ•mol(-1).