硫醇在金属表面自组装成膜的研究进展

金属表面自组装分子膜的研究近年来受到广泛关注,对金属表面自组装单分子膜的研究具有广泛的使用价值与应用价值。本以Au、Ag、Cu、Fe为代表,介绍了硫醇在其表面硫醇自组装成膜的过程、表面膜的结构、表面膜的特点和成膜的机理的研究进展,并且对其发展前景作了展望。     

Au（111）表面磺酸甜菜碱自组装单层膜的分子模拟

旨在探索磺酸甜菜碱型材料阻抗蛋白质吸附的微观机理,以更好地指导新型无生物污染材料的设计和开发.采用分子力学和分子动力学方法,对磺酸甜菜碱在Au（111）表面的分子自组装结构和性能进行研究.研究结果表明,磺酸甜菜碱在Au（111）表面可形成7×7的稳定结构,真空模拟中分子平均倾斜角为23,°水溶剂化模拟中则为25°,两性离子端基偶极方向趋于平行;水和磺酸甜菜碱的两性离子基团相互作用而吸附于表面上,形成一层牢固的水膜,从而有效地阻止蛋白质吸附到材料表面上.     

载金属离子的氧化铝吸附净化汽油中硫醇

采用载金属离子的氧化铝吸附净化汽油中硫醇。在微波条件下负载不同离子 ,从净化效果和吸附速率等方面选择了适宜的金属离子 ,实验测定了静态吸附平衡数据和动态吸附透过曲线 ,在本文所测的浓度范围内 ,静态吸附平衡数据符合线性关系 ,研究结果表明 :吸附剂具有净化汽油中硫醇和总硫的双重效果 ,可以为吸附过程的设计提供基础数据     

密度泛函理论研究NO在CuO(111)的表面吸附

为了深入研究纳米CuO与含能材料分解产生的NO间的相互作用,采用密度泛函理论研究了NO在CuO(1 1 1)表面的吸附行为,同时在NO吸附的最稳定位点研究NO_2在Cu表面的吸附及其对NO的影响;通过DMol~3模块中广义梯度密度泛函理论(GGA)的Perdew-Burke-Ernzerh (PBE)方法对吸附构型进行了计算。结果表明,NO以分子形式吸附在CuO(1 1 1)表面,较为稳定的吸附构型为NO的N原子与CuO表面的Cu、O原子相互作用,均为化学吸附;最稳定的吸附构型为NO吸附在Cu1位点上,吸附能为-0.89eV;HOMO-LUMO轨道能隙值和态密度图分析均表明NO和CuO表面有强烈相互作用;Mulliken电荷布局分析显示,电荷从NO转移到Cu表面,NO带部分正电荷;在含能材料分解过程中,NO气体稳定吸附在CuO表面,但当存在NO_2时,NO的吸附位点可能会被吸附能力更强的NO_2占据。     

十八硫醇自组装膜对银的缓蚀作用

在银电极表面制备了十八硫醇自组装膜,采用极化曲线、交流阻抗等电化学方法研究了不同浓度的十八硫醇对银的缓蚀作用的影响。结果表明:在温度50℃,自组装时间4h,十八硫醇0.05mol/L的条件下,缓蚀效率达到97.1%,覆盖度达到97.8%,十八硫醇在银电极表面形成了致密的自组装膜,有效地抑制了银的腐蚀。     

SDS表面活性剂在纳米尺度多层石墨烯的吸附自组装分子模拟

采用分子动力学模拟分别研究了纯水和电解质溶液中SDS表面活性剂在纳米尺度石墨烯表面的自组装结构,考察了不同石墨烯层数对自组装吸附形态和SDS/石墨烯复合物悬浮密度的影响。模拟结果揭示了上述两种溶剂介质中,SDS的表面自组装结构形态与石墨烯的结构层数有关,增加石墨烯的层数能够加大吸附表面活性剂向溶液中的伸展程度,使表面活性剂自组装结构膨胀。此外电解质存在能够导致SDS表面活性剂在石墨烯表面吸附形态由多层结构向半圆胶束转化。模拟计算进一步发现SDS/石墨烯超分子复合物的悬浮密度随石墨烯层数的增加呈近似线性增加。     

三(乙烯醇)单-11-十一烷基硫醇的合成研究

研究了一种合成三(乙烯醇)单-11-十一烷基硫醇的新方法,即以三乙二醇和1,11-二溴十一烷为底物,经过去质子化、取代、水解3步反应得到目标化合物三(乙烯醇)单-11-十一烷基硫醇.目标产物的总收率为16.5％,其结构经1H NMR确证.考察了氢化钠用量和水解反应催化剂对产物收率的影响.结果 表明,当n(三乙二醇)∶n(氢化钠)=1.00∶1.00时,水解反应催化剂选用浓氨水时,3步反应的收率较高.方法 副产物少,污染小,操作简单,适合小批量生产.     

第一性原理计算B在TiN(111)表面的吸附特性

利用第一性原理赝势波方法计算了B原子在TiN(111)表面的吸附特性。给出了B原子位于顶位、面心立方位、六方密堆位和桥位时,各吸附构型的吸附能、层间距、键长、电子结构计算结果。     

磷酸活化制备废筷子活性炭及其对硫醇吸附的研究

废筷子采用磷酸活化法在不同操作条件下制备得到各种活性炭。分别研究了磷酸活化法制备活性炭的主要操作参数,如浸渍比、磷酸浓度、活化温度和活化时间对活性炭收率和活性炭对碘的吸附值的影响。实验结果表明,在最佳工艺条件：磷酸浓度70％,浸渍比2．5：1,活化温度500℃,活化时间60min下,所制得活性炭的碘吸附值为885．23mg／g。另外,实验测定了废筷子采用磷酸活化法制备的活性炭对硫醇的吸附性能。结果发现活性炭的碘吸附值越高对硫醇的吸附效果越好。     

汽油中不同结构硫醇氧化行为的研究

在高剪切分散乳化机的作用下对含有不同结构硫醇的油样进行脱臭,通过改变加入硫醇的种类和含量,考察了不同结构硫醇脱臭的差别及其相互作用。实验结果表明,不同结构的硫醇其氧化脱除速度不同,碳链越长,异构程度越大,氧化脱除的速度越慢。但由于高剪切分散乳化机高效的混合效率,提高了脱臭效率,彼此间的差别大大减小。向叔丁硫醇中加入其它结构简单的硫醇后,可以促进叔丁硫醇的氧化脱除,并利用负离子-自由基机理对上述现象进行了解释。     

Creation of Low-Coordination Gold Sites on Au(111) Surface by 1,4-phenylene Diisocyanide Adsorption

The adsorption of CO on a saturated overlayer of 1,4-phenylene diisocyanide (PDI) adsorbed on a Au(111) surface at 300 K is studied using scanning tunneling microscopy (STM), density functional theory (DFT) calculations and reflection absorption infrared spectroscopy (RAIRS). The PDI forms closed-packed rows of gold-PDI chains by extracting gold atoms from the Au(111) substrate. They are imaged by STM and the structure calculated by DFT. The adsorption of CO is studied on the low-coordination gold sites formed on the PDI-covered surface where it adsorbs exhibiting a CO stretching frequency of 2004 cm^?1, consistent with adsorption on an atop site. It is found that CO is stable on heating the sample to ~150 K and is only removed from the surface by heating to ~180 K. Since low-coordination gold atoms are suggested to be the active catalytic sites on supported gold nanoclusters, ??embossing?? the surface to form similar low-coordination sites using PDI might offer a strategy for tailoring the catalytic activity of gold.     

In/Au(111)和Ir/Au(111)面上巴豆醛选择加氢的机理研究及比较

基于巴豆醛在M/Au（111）合金表面（M=In,Ir）垂直吸附的最稳定吸附结构,采用密度泛函理论对其不完全加氢的反应机理进行探究。从不同加氢机理下各基元反应的活化能、反应热计算以及构型变化分析中可知,巴豆醛在M/Au（111）面上均优先对距离合金表面较近的C＝O进行加氢,且以C为活性中心优先进行加氢为最优机理,其中第1步加氢反应的活化能较高,是该机理的控速步骤。反应物巴豆醛的O原子与合金的掺杂原子M形成较强的化学吸附,提高了M/Au（111）面对C＝O加氢的选择性。巴豆醛按最优机理加氢的基元反应中在In/Au（111）面上最高反应能垒为0.969 eV,比在Ir/Au（111）面的最高反应能垒1.332 eV低,因此认为In/Au合金对其不完全加氢有更好的催化活性。     

Adsorption characteristics of OH-terminated alkanethiol and arenethiol on Au(111) surfaces

Adsorption behaviors of hydroxyl-terminated alkanethiol, 3-mercapto-1-propanol (MPO), and arenethiol, 4-mercaptophenol (MPH), on Au(111) electrodes were studied by cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). The effects of the molecular structure and the chain length on the characteristics of the self-assembled monolayers (SAMs) were investigated by comparison with the results of 11-mercapto-1-undecanol (MUO) and 6-mercapto-1-hexanol (MHO) reported in the literature. All the alkanethiol SAMs have the same coverage ratio (0.33 ML). For MUO which has a longer chain length, a hexagonal lattice, the (√3 ×√3) structure was observed. However, for shorter thiols (MHO and MPO), the adsorbed molecules exhibit different contrasts under the imaging of STM, ascribed to the different conformations of adsorbed molecules. The CV results indicated that a longer chain length triggers a SAM with higher adhesion and higher resistance to the charge transfer across a SAM. For the SAM of arenethiol, MPH, the π-π stacking interaction of the phenyl ring leads to a lower surface mobility of thiol/Au complexes, lower coverage ratio, and less uniform structure of the adlayer. Furthermore, the vacancy islands commonly observed on alkanethiol-modified Au(111) electrodes do not appear on the MPH-modified surface. Instead, 2-dimensional patch islands formed on the terrace due to the aggregation of moveable MPH/Au complexes.     

Modeling of NC-AFM Imaging of Alkanethiols on the Au (111) Surface

We investigate the mechanisms of contrast formation in NC-AFM imaging of self-assembled monolayers of alkanethiols on the Au (111) surface. Comparing the potential models with implicit and explicit electrostatics, we demonstrate that, similar to the imaging of polar solid surfaces, the electrostatic interaction plays the central role in contrast formation. Careful comparison of several tip models showed that the model of a clean SiO₂ tip gives the closest agreement with the experimental data.     

Light Emission from M-Type Enantiomer of 2,13-bis(hydroxymethyl)[7]-thiaheterohelicene Molecules Adsorbed on Au(111) and C60/Au(111) Surfaces Investigated by STM-LE

Light emission from the M-type enantiomer of a helicene derivative (2,13-bis(hydroxymethyl)[7]-thiaheterohelicene) adsorbed on the clean Au(111) and the C₆₀-covered Au(111) surfaces were investigated by tunneling-current-induced light-emission technique. Plasmon-originated light emission was observed on the helicence/Au(111) surface and it was strongly suppressed on the area where the helicene molecules were adsorbed at the edges of the Au(111) terraces. To avoid luminescence quenching of excited helicene molecules and to suppress strong plasmon light emission from the Au(111) surface, C₆₀ layers were used as decoupling buffer layers between helicene molecules and the Au(111) surface. Helicene molecules were adsorbed preferentially on the Au(111) surface rather than on the C₆₀ buffer layers due to the small interaction of the molecules and C₆₀ islands. This fact motivated us to deposit a multilayer of helicene molecules onto the C₆₀ layers grown on the Au(111) surface, leading to the fact that the helicene/C₆₀ multilayer showed strong luminescence with the molecules character. We consider that such strong light emission from the multilayer of helicene molecules has a plasmon origin strongly modulated by the molecular electronic states of (M)-[7]TH-diol molecules.     

Adsorption and Decomposition of Glycerol on Pristine and Oxygen Modified Au(111) Surfaces

Topics in Catalysis - Research on biomass derived raw materials for conventional catalytic processes, especially those directed to replace human dependence on fossil-based energy, is a high...     

DFT研究钌配合物[Ru（bpy）2（o—R—pip）]^2＋与DNA键合

理论运用密度泛函（DFT）方法,计算钌（Ⅱ）配合物[Ru（bpy）2（o-R-pip）]^2＋（R=-OH,-H,-OCH3）的电子结构和与DNA键合倾向。证实了引入取代基（-OH）导致分子内氢键形成进而导致插入配体共轭面积的增大以及配合物最低空轨道LUMO和相邻的最低空轨道（LUMO＋x,X=0,1,2）的能量明显降低,可大大改善配合物与DNA的键合常数（Kb）。钌配合物与DNA的键合倾向,即Kb（3）〈Kb（2）〈Kb（1）,得以理论解释。     

水分子在高岭石(001)面吸附的密度泛函计算

为研究高岭石(001)面与水分子的相互作用机理,用Material studio 8.0构建了高岭石(001)面的晶体模型,使用GGA-PBE优化高岭石(001)面,分别计算(001)面和含有1、2、4个水分子的分子团吸附构型和平均结合能.结果表明,随着水分子数量的增加,结合能绝对值从35.87 kJ/mol增加到53.94 kJ/mol,复合体系稳定性增加.通过静电势分析可知,高岭石表面主要是负静电势区域略大于正静电势区域.当水分子数量由1个增加到4个时,静电势绝对值较大(>188.18 kJ/mol)的面积由7.99％增加到8.49％,整体静电势水平提高,有利于后续水分子吸附.运用RDG函数,展示了高岭石和水分子之间的弱相互作用,结果表明高岭石和水分子主要通过氢键方式结合.由AIM分析的结果可知,高岭石-水的氢键键能弱于水-水的氢键,当水分子数量增加时,高岭石-水氢键键能会进一步减弱.