和频振动光谱研究多晶金电极/溶液界面乙腈分子取向的flip-flop行为

用和频振动光谱研究乙腈/金电极界面,观测到乙腈的甲基振动峰强度随施加的电极电势而变化.当电极电势越过零电荷电势（pzc）时,甲基振动峰符号发生反转,这意味着基团取向发生反转（flip-flop）.由此推断出乙腈分子在金电极界面的吸附构型.即在零电荷电势下,电极界面吸附的乙腈分子构型为甲基靠近电极表面而腈基远离电极表面;而高于零电荷电势则电极界面吸附的乙腈分子构型发生反转,变为腈基靠近电极表面而甲基远离电极表面的构型.     

异质结界面修饰对TiO2/P3HT杂化太阳电池光电性能的增强作用

采用水热法在F-SnO₂(FTO)导电玻璃上制备了一维TiO₂纳米棒阵列, 将一种两亲有机三苯胺染料M分子吸附在其表面, 进而旋涂有机聚合物聚3-己基噻吩P3HT, 构建结构为FTO/TiO₂/M/P3HT/PEDOT:PSS/Au的杂化太阳电池. 瞬态光电流谱反映在杂化电极中存在pn异质结. 接触角测试表明TiO₂表面吸附有机M分子后, 亲水性表面转变为疏水性表面, 利于与聚合物P3HT的进一步接触; 稳态荧光发射光谱表明经修饰的杂化电极的荧光发射强度降低, 由荧光衰减曲线拟合得到的荧光寿命降低, 说明在TiO₂与P3HT之间存在有效的电荷转移, 电荷复合被抑制. 电化学阻抗分析表明界面修饰后电子复合电阻和电子寿命增大. 电池的特性参数均比界面修饰前有所提高, 光电转换效率为1.61%. 另外, 对该电池的工作机理、电荷传输过程进行了初步探讨.     

蛋白质在固体表面吸附的研究进展

蛋白质在固体表面的吸附有多种理论模型和实验分析.蛋白质吸附主要包括分子传递、吸附、重排、交换、解吸等步骤.蛋白质在表面的状态由表面性能、静电作用及蛋白质自身性质等因素决定.蛋白质分子在界面吸附后发生构象改变,引起熵增.     

环状构象PEG改性表面及其优越的抗凝血性能

聚乙二醇(PEG)因其优异的抗蛋白质吸附能力成为抗凝血材料的首选.目前,多数研究都集中在PEG链长和接枝密度对蛋白质吸附的影响,鲜有关注PEG链构象影响的研究.本文利用硫金键在石英晶体微天平金片表面构建了两种不同分子量(MW=1000和MW=5000)的环状(SH-PEG-SH)和线型(m PEG-SH)构象的PEG改性表面,并研究了其抗纤维蛋白原吸附机理和抗凝血性能.X射线光电子能谱仪和原子力显微镜确定了不同表面的组成及其相结构.结果发现,环状构象的PEG表面相对于线型PEG构象能更加有效地抑制纤维蛋白原的吸附,同时具有更加优异的抗血小板和红细胞黏附性能.分析其蛋白质吸附机理发现,当PEG分子量较低时(MW=1000),其环状构象PEG表面抗纤维蛋白原吸附机理源于较高的表面覆盖率;当PEG分子量较高时(MW=5000),其抗纤维蛋白原吸附机理源于高黏弹性和高表面覆盖率共同作用的结果.本工作为构建抗凝血涂层提供了新的思路,并为制备高性能生物医用材料提供了理论基础.     

氢酶分子聚集体薄膜的组装及其在催化产氢中的应用*

氢气作为一种可再生和零排放的清洁能源,在全球能源和环境双重危机的今天倍受各国政府、企业和研究人员的关注。自然界中存在于藻类和细菌中的氢酶是高效的催化氢气氧化和质子还原的氧化还原酶,在生物产氢和能量转换过程中发挥着重要的作用。近年来涌现出了许多基于氢酶及其模型化合物的仿生产氢和生物燃料电池方面的研究工作。本文综述了氢酶及其分子聚集体薄膜在电极表面的组装技术,如吸附法、自组装法、Langmuir-Blodgett法和溶胶－凝胶法等,并讨论了分子聚集体薄膜中氢酶的结构、生物活性、电化学性质及其在催化产氢方面的应用。     

纳米材料-蛋白质界面相互作用的分子机制

纳米材料由于其优异的性能在化工、电子、机械、环境、能源、航天等各个领域已经得到了广泛的应用,并且在生物医学方面的应用越来越受到重视。纳米材料-蛋白质界面相互作用是纳米生物医学领域重要的科学问题,对于纳米材料的生物医学应用以及生物安全性评价至关重要。蛋白质分子与纳米材料在界面的相互作用,一方面可以诱导蛋白质的构象、组装结构甚至功能的改变,另一方面可以引起纳米材料的表面亲疏水性、电荷性质等表面物理化学性质的改变。基于蛋白质与纳米材料相互作用检测技术及结果,本文从分子水平阐述了纳米材料与蛋白质分子在界面之间的相互作用机理及相应的结构与性质的变化,从而可以深化对两者之间复杂的相互作用机制的理解,对于推进纳米材料在生物医学的应用及健康、安全、持续发展具有重要意义。     

血红蛋白在自组装单层修饰电极上的直接电化学研究

对于氧化还原蛋白质在电极界面上的直接电子转移的研究对于生物传感器的构建,生物材料的发展和生物系统的认识有很重要的作用~([1]).虽然许多方法已经实现了蛋白质的直接电子传递,这些方法多数侧重于生物传感器的构建,对如何通过控制蛋白质的吸附状态来实现直接电子传递并没有系统的报道.蛋白质在吸附到电极表面的过程中,许多因素都能影响蛋白质的电子传递,如蛋白质的取向,蛋白质的活性中心与电极的距离等.     

单分子电子器件电极-分子界面设计和调控

电极-分子接触界面在单分子器件中扮演着至关重要的作用.通过对电极、分子的锚定基团以及电极与分子间作用方式进行设计和调控,可以有效控制电极-分子界面结构和性质,从而影响单分子器件的性能和功能.本文从单分子器件研究的常用技术手段出发,综述单分子器件中常见的电极-分子接触界面类型及构建方式,并进一步阐述机械力、电化学及电场等...     

化学功能化增强贵金属纳米晶电催化性能（英文）

基于电催化过程的可再生和清洁能源的生产、转换和储存技术(如水电解和燃料电池)是缓解全球能源短缺和环境污染问题的有效手段.目前,水电解和燃料电池技术的实际应用缺乏高效、稳定的电催化剂来驱动动力学迟缓的阴极和阳极反应.贵金属纳米晶由于其独特的电子结构和高化学惰性而具有高电催化活性和稳定性.为了提升贵金属纳米晶的本征电催化性能,大量研究聚焦在利用面积效应、晶面效应和不同组分之间的协同效应来调控贵金属的粒径、形貌和化学成分.事实上,贵金属纳米晶的电催化性能也与其表/界面性质密切相关.电催化剂表面的化学功能化可以改变电极/电解质界面结构,从而提高电催化活性和选择性,这对开发新型高效的电催化剂具有重要的理论意义.本文系统介绍了本课题组开发的聚胺(PAM)功能化贵金属纳米电催化剂的合成方法及其在燃料电池和电解池等能源转换装置中的应用,具体包括:通过引入PAM控制反应动力学来调控纳米晶体的结构和形态,构建界面功能化贵金属纳米电催化剂;利用金属表面修饰的PAM分子改变表面催化位点的电子结构、配位环境等物理化学性质来控制反应物和中间体等的吸附行为,从而达到调节催化活性的目的;采用PAM分子来隔离特定活性位...     

抗污界面构建及其电化学生物传感应用进展

电化学生物传感器具有灵敏度高、便携性好、响应快速和易于集成等优点,在临床检测方面有很大应用潜力,并在可穿戴健康监测领域得到了快速发展。但在实际临床生物样本检测中,非靶标生物物质会在电极表面产生非特异性吸附（即生物污染）,影响了电化学生物传感器的性能。因此,构建具有防污染能力的传感界面（抗污界面）,防止非靶标物质吸附到电极表面,对于扩大电化学生物传感器的实际应用范围,实现在复杂生物样本中的检测至关重要。本文概述了物理、化学和生物抗污电极界面的构建及其在临床相关生物标志物检测中的应用,为电化学生物传感器实际应用性能的提升提供技术参考,并通过对界面抗污原理和存在问题的探讨,对抗污界面发展前景和未来趋势予以展望。     

Surface electric field manipulation of the adsorption kinetics and biocatalytic properties of cytochrome c on a 3D macroporous Au electrode

Upon adsorbing on a solid-state substrate, water-soluble proteins are prone to denaturation and deterioration of their functions due to the conformation change. The surface electric field of a conductive substrate is one of the important factors that influence the character of adsorbed proteins. In this work, a 3D macroporous gold electrode has been prepared and served as the working electrode to study the influence of surface electric field on the adsorption kinetics and conformation of the adsorbed cytochrome c (cyt-c) with the help of electrochemical, in situ electrochemical IR spectroscopic, atomic force microscopic, and contact angle measurements. The external electric field creates excess surface charge which can manipulate the adsorption rate of proteins on the substrate by the enhanced electrostatic interactions between the electrode and protein patches by coupling with complementary charges. The amount of immobilized cyt-c with electrochemical activity on the 3D macroporous gold electrode showed a minimum at potential of zero charge (PZC) and it increased with increasing net excess surface charge. Higher electric field could influence the conformation and the corresponding properties such as direct electrochemistry, bioactivity, and surface character of the adsorbed cyt-c molecules. However, high external electric field leads to damage of the protein secondary structure. This study provides fundamentals for the fabrication of biomolecular devices, biosensors, and biofuel cells through electrostatic interactions. Figure Two cases are illustrated for the protein immobilized on electrode surfaces: a retention of protein structure under moderate excess surface charge, b denaturation and conformation change of proteins adsorbed at high excess surface charge, e.g., due to the higher external electric field.     

Electrostatic and dispersion interactions during protein adsorption on topographic nanostructures

Recently, biomaterials research has focused on developing functional implant surfaces with well-defined topographic nanostructures in order to influence protein adsorption and cellular behavior. To enhance our understanding of how proteins interact with such surfaces, we analyze the adsorption of lysozyme on an oppositely charged nanostructure using a computer simulation. We present an algorithm that combines simulated Brownian dynamics with numerical field calculation methods to predict the preferred adsorption sites for arbitrarily shaped substrates. Either proteins can be immobilized at their initial adsorption sites or surface diffusion can be considered. Interactions are analyzed on the basis of Derjaguin-Landau-Verway-Overbeek (DLVO) theory, including electrostatic and London dispersion forces, and numerical solutions are derived using the Poisson-Boltzmann and Hamaker equations. Our calculations show that for a grooved nanostructure (i.e., groove and plateau width 8 nm, height 4 nm), proteins first contact the substrate primarily near convex edges because of better geometric accessibility and increased electric field strengths. Subsequently, molecules migrate by surface diffusion into grooves and concave corners, where short-range dispersion interactions are maximized. In equilibrium, this mechanism leads to an increased surface protein concentration in the grooves, demonstrating that the total amount of protein per surface area can be increased if substrates have concave nanostructures.     

Protein-coated beta-ferric hydrous oxide particles. An electrokinetic and electrooptic study

Using microelectrophoresis and electric light scattering techniques, we investigated the adsorption characteristics, surface coverage and surface electric parameters of superstructures from two isoforms of plastocyanin, PCa and PCb, in an oxidized state adsorbed on beta-ferric hydrous oxide particles. The surface electric charge and electric dipole moments of the composite particles and the thickness of the protein adsorption layer are determined in a wide pH range, at different ionic strengths and concentration ratios of PC to beta-FeOOH. The adsorption of the two proteins was found to shift the particles' isoelectric point and to alter the total electric charge and the electric dipole moments of the oxide particles to different extent. A "reversal" in the direction of the permanent dipole moment is observed at lower pH for PCb- than for PCa-coated oxide particles. Strict correlation is found between the changes in the electrokinetic charge of the composite particles and the variation in their "permanent" dipole moments. Data suggest that the adsorption of the proteins is driven by electrostatic and/or hydrophobic interactions with the oxide surfaces dependent on pH. The adsorption behaviour is consistent with the involvement of the "eastern" and "northern" patches of the plastocyanin molecules in their adsorption on the oxide surfaces that are differently charged depending on pH.     

Protein-coated β-ferric hydrous oxide particles: An electrokinetic and electrooptic study

Using microelectrophoresis and electric light scattering techniques, we investigated the adsorption characteristics, surface coverage and surface electric parameters of superstructures from two isoforms of plastocyanin, PCa and PCb, in an oxidized state adsorbed on β-ferric hydrous oxide particles. The surface electric charge and electric dipole moments of the composite particles and the thickness of the protein adsorption layer are determined in a wide pH range, at different ionic strengths and concentration ratios of PC to β-FeOOH. The adsorption of the two proteins was found to shift the particles’ isoelectric point and to alter the total electric charge and the electric dipole moments of the oxide particles to different extent. A “reversal” in the direction of the permanent dipole moment is observed at lower pH for PCb- than for PCa-coated oxide particles. Strict correlation is found between the changes in the electrokinetic charge of the composite particles and the variation in their “permanent” dipole moments. Data suggest that the adsorption of the proteins is driven by electrostatic and/or hydrophobic interactions with the oxide surfaces dependent on pH. The adsorption behaviour is consistent with the involvement of the “eastern” and “northern” patches of the plastocyanin molecules in their adsorption on the oxide surfaces that are differently charged depending on pH.     

The impact of ionic strength on the adsorption of protons, Pb, Cd, and Sr onto the surfaces of Gram negative bacteria: testing non-electrostatic, diffuse, and triple-layer models

Bacterial surface adsorption reactions are influenced by electric field effects caused by changes in ionic strength; however, existing datasets are too sparse to definitively constrain these differences or to determine the best way to account for them using thermodynamic models. In this study, we examine the ionic strength dependence of proton and metal adsorption onto the surfaces of Pseudomonas mendocina and Pseudomonas putida by conducting proton, Cd(II), Pb(II), and Sr(II) adsorption experiments over the ionic strength range of 0.001 to 0.6 M. Chosen experimental results are thermodynamically modeled using a non-electrostatic approach, a diffuse layer model (DLM), and a triple-layer model (TLM). The results demonstrate that bacterial surface electric field effects are negligible for proton, Cd, and Pb adsorption onto P. putida and P. mendocina, and that the discrete site non-electrostatic model developed in this study is adequate for describing these reactions. The extent of Sr adsorption is influenced by changes in the bacterial surface electric field; however, the non-electrostatic model better describes Sr adsorption behavior than the DLM or TLM. The DLM and TLM greatly overpredict the effect of the electric field for all adsorption reactions at all ionic strengths tested.     

Bioinert surface to protein adsorption with higher generation of dendrimer SAMs

Interactions between proteins and biomaterial surfaces correlate with many important phenomena in biological systems. Such interactions have been used to develop various artificial biomaterials and applications, in which regulation of non-specific protein adsorption has been achieved with bioinert properties. In this research, we investigated the protein adsorption behavior of polymer brushes of dendrimer self-assembled monolayers (SAMs) with other generations. The surface adsorption properties of proteins with different pI values were examined on gold substrates modified with poly(amidoamine) dendrimer SAMs. The amount of fibrinogen adsorption was greater than that of lysozyme, potentially because of the surface electric charge. However, as the generations increased, protein adsorption decreased regardless of the surface charge, suggesting that protein adsorption was also affected by density of terminal group.     

Two-step elution of human serum proteins from different glass-modified bioactive surfaces: a comparative proteomic analysis of adsorption patterns

Plasma protein adsorption patterns on surfaces may give vital information to evaluate biocompatibility of biomaterials designed for direct blood-contacting applications or tissue integration. Adsorption of human serum proteins on four different types of biomaterials (glass, aminosilanized glass, hyaluronan and sulfated hyaluronan) was analyzed by two-dimensional electrophoresis. Desorption of proteins from the surfaces was first classically achieved by sodium dodecyl sulfate (SDS) elution. We introduced a second elution step (by use of isoelectric focusing (IEF) sample buffer consisting of urea, 3-[(3-cholamidopropyl)dimethylammonio]-1-propansulfonate, and dithioerythritol) which allows more stringent elution conditions and is a tool to evaluate the protein adsorption strength to biomaterials. Moreover, the two-step elution may discriminate between irreversible and reversible adsorption of plasma proteins for biomaterials, thus helping to elucidate the structure of protein multilayers which form a complex system at the surfaces. The IEF sample buffer proved not to alter the biomaterial structure and integrity. Hydrophobic bonds resulted to be the main strength driving protein adsorption onto our biomaterials. Apolipoproteins were the most important proteins interacting with the surfaces suggesting that high-density lipoprotein (HDL) particles could play a role in biocompatibility due to their beneficial effects on endothelial cells.     

Theoretical study of the adsorption and dissociation of oxygen on Pt(111) in the presence of homogeneous electric fields

The effect of homogeneous electric fields on the adsorption energies of atomic and molecular oxygen and the dissociation activation energy of molecular oxygen on Pt(111) were studied by density functional theory (DFT). Positive electric fields, corresponding to positively charged surfaces, reduce the adsorption energies of the oxygen species on Pt(111), whereas negative fields increase the adsorption energies. The magnitude of the energy change for a given field is primarily determined by the static surface dipole moment induced by adsorption. On 10-atom Pt(111) clusters, the adsorption energy of atomic oxygen decreased by ca. 0.25 eV in the presence of a 0.51 V/A (0.01 au) electric field. This energy change, however, is heavily dependent on the number of atoms in the Pt(111) cluster, as the static dipole moment decreases with cluster size. Similar calculations with periodic slab models revealed a change in energy smaller by roughly an order of magnitude relative to the 10-atom cluster results. Calculations with adsorbed molecular oxygen and its transition state for dissociation showed similar behavior. Additionally, substrate relaxation in periodic slab models lowers the static dipole moment and, therefore, the effect of electric field on binding energy. The results presented in this paper indicate that the electrostatic effect of electric fields at fuel cell cathodes may be sufficiently large to influence the oxygen reduction reaction kinetics by increasing the activation energy for dissociation.     

The effect of electric field and Al doping on the sensitivity of hexa‐peri‐hexabenzocoronene nanographene to chloropicrin

It has been previously reported that the recently synthesized hexa‐peri‐hexabenzocoronene (HBC) nanographene cannot detect toxic chloropicrin (CP) gas. To overcome this problem, we examined the effect of Al doping and applying an electric field on the sensitivity of HBC towards CP gas by means of density functional theory calculations. We found that the Al‐doping process significantly increases the adsorption energy of CP gas from ?7.1 to ?39.9 kcal mol^?1 but decreases the sensitivity of HBC. By applying an electric field, the HBC is polarized with two different electrostatic potentials on its different surfaces, which increases the adsorption energy. By increasing the electric field strength, the adsorption energy and electronic sensitivity of HBC are increased. We predicted that in the presence of an electric field of about ?0.025 au, HBC can act as an electronic senor or a work function‐type sensor with a short recovery time. At this field, the electrical conductivity of HBC is significantly increased on CP adsorption which generates an electrical signal. Increasing the electric field to higher intensities is not favourable because of increasing recovery times, and decreasing it to lower intensities reduces the sensitivity of HBC.     

Streaming potential and electroosmotic flow in heterogeneous circular microchannels with nonuniform zeta potentials: requirements of flow rate and current continuities

Real surfaces are typically heterogeneous, and microchannels with heterogeneous surfaces are commonly found due to fabrication defects, material impurities, and chemical adsorption from solution. Such surface heterogeneity causes a nonuniform surface potential along the microchannel. Other than surface heterogeneity, one could also pattern the various surface potentials along the microchannels. To understand how such variations affect electrokinetic flow, we proposed a model to describe its behavior in circular microchannels with nonuniform surface potentials. Unlike other models, we considered the continuities of flow rate and electric current simultaneously. These requirements cause a nonuniform electric field distribution and pressure gradient along the channel for both pressure-driven flow (streaming potential) and electric-field-driven flow (electroosmosis). The induced nonuniform pressure and electric field influence the electrokinetic flow in terms of the velocity profile, the flow rate, and the streaming potential.