Hydrophobicity-induced drying transition in alkanethiol self-assembled monolayer—water interface

During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance. This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading to the possible creation of a hydrophobic interfacial gap.     

量子点器件的三端电测量研究

利用三端电测量方法，研究了调制掺杂二维电子气结构的量子点器件输运特性.报道了可分别测量二维电子气电阻和量子点隧穿电阻的实验方法.实验结果表明：量子点的横向耦合控制了量子点器件在小偏压下的电输运特性. 关键词： 自组装量子点 二维电子气 量子隧穿 肖特基接触     

自组装双硫醇分子膜阻抗谱的研究

对交流电场下双巯基烷烃硫醇自组装分子膜的阻抗谱进行了研究.利用汞金属作为衬底,制备出双巯基烷烃硫醇自组装分子膜,并通过交流频谱仪对其进行频谱的扫描．明确了膜的作用范围为阻抗谱中频部分为了解释该阻抗谱,提出了一种串联的等效电路来进行了拟合,并与其他的模型进行比较.同时,观察到在损耗谱中损耗峰随硫醇碳链原子数的增加而向低频方向移动并得出双巯基硫醇(C6-C10)在交流电场下的激活能为23～39 meV．     

Preparation of Nanoelectrode Ensembles by Assembly of Nano—Silver Colloid on Gold Surface

A novel method for preparing silver nanoelectrode ensembles(SNEEs) and gold nanoelectrode ensembles (GNEEs) has been developed. Silver colloid particles were first absorbed to the gold electrode surface to form a monolayer silver colloid. N-hexadecyl nercaptan was then assembled on the electrode to form a thoil monolayer on which hydrophilic ions cannot be transfered. The SNEEs was prepared by removing thiol from silver colloid surface through applying and AC voltage with increasing frequency at 0.20V(vs.SCE). Finally,GNEEs was obtained by immersing a SNEEs into 6 mol/L HNO3 to remove the silver colloid particles. By comparison with other methods such as template method ect., this method enjoys some advantages of lower resistance, same diameter,easy preparation,controllable size and density.     

2-巯基乙醇自组装膜电极对多巴胺电催化氧化及其分析应用

在裸金电极上制备了 2 巯基乙醇自组装膜电极 (ME AuSAMs) ,研究了多巴胺 (DA)在ME AuSAMs上的电化学行为 ,发现该膜电极对DA的氧化具有良好的电催化作用 ,氧化过电位降低了 3 94mV ,测得DA的扩散系数D为 9.1 4 5× 1 0 - 7cm2 s,初步探讨了电催化机理。采用水平衰减全反射 傅里叶变换红外光谱 (ATR FTIR)技术对ME AuSAMs进行了表征 ;方波伏安法 (squarewavevoltammetry ,SWV)测定DA ,其氧化峰电流与DA浓度在 2 .0 0× 1 0 - 6 ～ 1 .0 0× 1 0 - 4 mol L范围内呈线性关系 ;相关系数为 0 .9998,检出限为 4 .0 0× 1 0 - 7mol L。该电极用于DA药物针剂的测定 ,结果满意     

自组装合成纳米复合TiO2-ZnO介孔材料及其光催化性能

以TiCl₄, ZnSO₄•7H₂O为原料, 尿素为沉淀剂, 利用可溶性淀粉大分子链的空间位阻效应和高分子网络的阻隔作用, 以纳米级碳黑为模板, 采用微波加热、均相沉淀法合成出了一系列纳米TiO₂-ZnO复合介孔材料. XRD分析证明反应前驱体为非晶态, 500 ℃以上转变为锐钛矿结构的TiO₂和ZnTiO₃, 当Ti∶Zn＝1(摩尔比)时, 产物全部为ZnTiO₃ (TiO₂•ZnO). TEM形貌观察结合N₂吸附表明, 基本粒子为球形, 粒径15～20 nm. 最可几孔径8～10 nm. EDS分析证明产品中Ti∶Zn的分析测定值与实际的投料值基本一致, 并且掺杂均匀性好. 光吸收及光催化实验发现Zn含量为50%时, 光催化效果最好, 在日光照射90 min后, 此TiO₂-ZnO复合材料对藏蓝染料溶液降解率可达到100%, 其光催化反应符合一级动力学方程.     

Selective determination of uric acid in the presence of ascorbic acid using a penicillamine self-assembled gold electrode

The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode (Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry (CV). The diffusion coefficient D of UA is 6.97 × 10⁻⁶ cm² s⁻¹. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit was 1 × 10⁻⁶ mol L⁻¹. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties.     

超分子自组装合成杯[4]芳烃黄原酸镍(Ⅱ)配合物

利用二维和三维的大环及笼状主体分子与金属离子直接进行自组装反应合成新型有机无机杂化分子是当前超分子领域的研究热点之一。这类分子不仅具有新奇的光、电、磁等特性，而且还可作为新型的主体分子在客体识别、催化、吸附与分离等方面有广阔的应用前景。杯芳烃是有机超分子领域广受     

Molecular Dynamics Simulation of the Self-assembled Monolayers of 1-Adamantanethiolate and Its Derivatives on Au（111） Surfaces

The self-assembled monolayers （SAMs） of 1-adamantanethiolate and its derivatives on Au（111） surface were investigated. Density functional theory （DFT） calculation indicates that the most stable configuration for absorption is at the face centered cubic （fcc）-bridge site. Canonical ensemble molecular dynamics （MD） simulations were carried out to study the structures and energies of the SAMs. The ordered structures of the SAMs were analyzed by means of radial distribution function and the relative stability of the SAMs was compared. It was concluded by the comparison of various contributions to the SAM formation energy that the formation of the SAMs was determined by the intermolecular nonbonding interaction and the chemical bonding interaction of sulfur and gold.     

Characterization of self-assembled monolayers of thiols on Au(111)

Self-assembled monolayers (SAMs) of n-butanethiol, n-dodecanethiol and their equimolar mixture on Au(111) were prepared and characterized by ellipsometry, contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results revealed that these SAMs are oriented ultrathin films with the thickness of nanometer scale, and the SAMs were influenced by the molecular chain length, the lattice orientation and cleanliness of the substrates. The surface of the longer chain SAM is hydrophobic. The thicknesses of three SAMs of n-butanethiol, n-dodecanethiol and their mixture revealed by ellipsometry and XPS are about 0.59 - 0.67nm, 1.60- 1.69 nm and 1.23 - 1.32nm, respectively. AFM images further demonstrated that the SAM formed by the mixture has some microdomains with two different thicknesses.