分子结构对硫脲类化合物在铜表面自组装能力的影响

利用电化学阻抗谱和极化曲线研究了硫脲、烯丙基硫脲、苯基硫脲在金属铜表面上的自组装膜的质量和缓蚀效率, 并通过量子化学计算进一步研究了各种分子和金属铜的相互作用. 结果表明硫脲类分子在金属铜表面上的成膜能力顺序为: 苯基硫脲＞烯丙基硫脲＞硫脲, 并揭示了分子结构对硫脲类化合物在金属铜表面自组装影响的本质, 为进一步寻找和制备优良的缓蚀功能自组装膜提供理论依据.     

负载苯基硫脲酚醛型螯合树脂对Ag+的吸附与实验室应用

在四丁基溴化铵(TBAB)相转移催化条件下,线形环氧酚醛树脂(F44)与苯基硫脲(PTU)发生开环加成,合成了负载苯基硫脲的酚醛型螯合树脂(F44-PTU).研究了该树脂对Cu2 、Ni2 、Pb2 、Hg2 、Au3 的吸附容量及温度、离子浓度、pH值对Ag 吸附性能的影响.结果表明,该树脂对Ag 具有较好的吸附性能,吸附符合Freundlich等温式.吸附树脂在5%硫脲～1mol/L HNO3时可洗脱再生,再生后树脂的吸附能力下降,可能在Ag 的吸附过程中伴随有氧化还原作用.将合成树脂处理实验室含银废液,银的回收率可达93.8%.     

对甲苯基硫脲和对溴苯基硫脲的晶体结构和电子结构

本文测定了对甲苯基硫脲(1)和对溴苯基硫脲(2)的晶体结构,并用 CNDO/2程序对生物活性较大的对甲苯基硫脲分子进行了量子化学计算。1属单斜晶系,空间群 P2_1/n,a=0.5618(1),b=0.8487(4),c=1.7865(3)nm,Bβ=93.53(1)°,Z=4,D。=1.298 g·cm~(-3),最终偏离因子 R=0.0396;2属单斜晶系,空间群 P 2_1/n,a=0.9096(6),b=0.8991(4),c=1.0659(8)nm,β=105.59(6)°,Z=4,D。=1.836g·Cm~(-3),最终偏离因子R=0.073。晶体结构测定结果表明,硫脲部分的四个原子组成平面三角形,苯环平面与硫脲平面的夹角分别为63.5°和68.6°。量化计算结果和晶体结构测定相吻合。     

苯基硫脲接枝壳聚糖的合成及其对金属离子吸附性能的研究

苯基硫脲与经氨基保护的Schiff碱壳聚糖进行接枝反应，合成了一种对金属离子具有优良螯合性能的苯基硫脲壳聚糖。主要中间体和目标产物经IR光图谱分析表征与预期结构一致，并研究了目标产物对Cr^6 ，Cu^2 的吸附性能。     

硫脲衍生物及其Cu+配合物的NMR研究

对新的配体硫脲衍生物及其Ｃｕ（Ⅰ）配合物Ｎ－（邻硝基苯基）－Ｎ′－（乙氧基羰基）硫脲（Ｈ２ｏｅｔ）（１）,Ｎ－（对硝基苯基）－Ｎ′－（乙氧基羰基）硫脲（Ｈ２ｐｅｔ）（２）,Ｎ－（对硝基苯基）－Ｎ′－（丁氧基羰基）硫脲（Ｈ２ｐｂｔ）（３）和Ｃｕ（Ｈ２ｏｅｔ）２Ｃｌ（４）,［Ｃｕ（Ｈ２ｐｅｔ）２Ｃｌ］·ＣＨ２Ｃｌ２（５）,［Ｃｕ（Ｈ２ｐｂｔ）２Ｃｌ］２（６）作了１Ｈ、１３Ｃ－ＮＭＲ测定,化合物（１）和（６）还进行了Ｈ－ＨＣＯＳＹ（氢－氢相关二维谱）和ＨＭＱＣ（氢核检测的异核多量子相关谱）２ＤＮＭＲ实验,归属了全部的Ｈ、Ｃ谱线;简单讨论了配合物的配位行为。     

TTF、TCNQ及电荷转移复合物TTF-TCNQ在Au（111）表面吸附的ECSTM研究

研究发现当电极电位处于双层区时,三种分子在Au（111）电极表面均可形成高度有序的吸附结构.TTF与TCNQ分子有序吸附层的单胞结构分别为（6×3）和（4×7）,如图1中的模型所示,分子均是以平躺的方式吸附在Au（111）电极表面.而当电极电位向负方向移至0.08V（RHE）时,TCNQ分子的吸附结构发生了相转变,形成了一种单胞为（3√3×12）的新型结构.这是由于在较负的电位下,TCNQ分子与金电极之间的作用减弱,而相邻分子之间的排斥作用占据主导地位,使得相邻分子间的角度由原来的60°增大至90°,单胞结构发生了相应的改变.电荷转移复合物TTF-TCNQ在Au（111）表面则构筑了层状吸附结构,而且分子不再以平躺形式进行吸附,而是采取肩并肩站立的方式堆积成有序结构,与单纯两种分子在吸附结构和吸附方式上均不相同,如图2所示.此时π-π堆积作用在分子的组装过程中占据主导地位,该堆积方式与TTF-TCNQ单晶和薄膜的结构具有一定的相似性.     

meso-四(对甲氧基苯基)卟啉钴在货币金属单晶表面的吸附与自组装研究

利用超高真空低温扫描隧道显微镜系统研究了meso-四对甲氧基苯基卟啉钴分子在Au（111）、Ag（111）和Cu（111）表面的吸附与自组装.该分子在金属表面可以形成两种组装结构A和B.在结构A中,分子间的相互作用主要为π-π堆叠,仅在Au（111）和Ag（111）表面被实验观察到;在结构B中,分子间的相互作用为氢键,仅在Ag（111）和Cu（111）表面被实验观察到.分子-衬底相互作用的差异所引起的分子吸附构象变化被认为是导致不同衬底上的分子形成不同组装结构的原因.研究发现在不同衬底上,分子形成自组装结构的行为存在明显差异.在相近覆盖度下,未参与组装的分子的比例在Cu（111）表面最高,Au（111）次之,Ag（111）最低.表面上参与形成两种组装结构的分子与未参与组装的分子的比例还可通过覆盖度和退火来进行调控.     

金/巯基环肽单层膜的循环伏安和交流阻抗初步研究

用电化学方法初步研究了巯基环肽的在金基底上形成的吸附层,结果表明硫基环肽（CPCBC）可以在金表面形成成具有一定覆盖度的吸附膜;与烷基硫醇单层膜不同的是,该吸附膜十分松散。我们初步认为巯基环肽分子采用“直立式吸附”并且巯基环肽分子结构的复杂性是造成吸附膜松散的原因。     

苯基硫脲—磷酸三丁酯—醋酸丁酯体系对铂萃取作用的研究

本文研究了苯基硫脲（ＰＴＵ）－磷酸三丁酯（ＴＢＰ）－醋酸丁酯体系对Ｐｔ（Ⅳ）的萃取作用，发现在１￣６ｍｏｌ／Ｌ ＨＣＬ介质中，若先使Ｐｔ（Ⅳ）与ＰＴＵ（６ｍｏｌ／Ｌ ＨＣＬ溶液）在水相中反应，然后用ＴＢＰ－醋酸丁酯溶液萃取，则铂可被定量萃取至有机相中。用斜率法测得萃合物的组成为Ｐｔ：ＰＴＵ：ＴＢＰ＝１∶１∶２，借助吸收光谱和红外光谱探讨了萃合物的可能结构，并对协同萃取机理进行了讨论。     

用苯基硫脲—磷酸三丁酯体系连续萃取分离钯（II）,铂（IV）,铑（Ⅲ）

研究了用苯基硫脲－磷酸三丁酯体系对Ｐｄ（Ⅱ），Ｐｔ（Ⅳ），Ｒｈ（Ⅲ）进行连续萃取分离的新方法。在ＨＣｌ介质中，控制不同的萃取条件，可将Ｐｄ（Ⅱ）、Ｐｔ（Ⅳ）、Ｒｈ（Ⅲ）按顺序定量分离。确定了萃取分离的适宜条件，当Ｐｄ（Ⅱ）、Ｐｔ（Ⅳ）、Ｒｈ（Ⅲ）三者含量比例在１００：１：１，１：１０：１及１：１：１００范围内，均可得到定量分离。常见贱金属不影响萃取分离，贵金属中Ｏｓ（Ⅳ）、Ｉｒ（Ⅳ）允许相当量存在     

Quantification of fluorine density in the outermost atomic layer

The outermost atomic layer of perfluorinated thiol monolayers on gold and poly(tetrafluoroethylene) (PTFE) is analyzed by low-energy ion scattering. Absolute quantification of fluorine density in this layer was achieved after calibrating the fluorine signal with a freshly cleaved LiF(100) single crystal. The fluorine density of monolayers of a C8F17-thiol on gold was 1.48 x 10(15) F atoms/cm2, whereas for PTFE a value of 1.24 x 1015 F atoms/cm2 was observed. This difference was explained by the different tilt angles of the thiol on gold and PTFE chains with respect to the surface normal. Both a configurational and a molecular interpretation on the perfluorinated thiol monolayer on gold are given.     

Packing density and structure effects on energy-transfer dynamics in argon collisions with organic monolayers

A combined experimental and molecular-dynamics simulation study has been used to investigate energy-transfer dynamics of argon atoms when they collide with n-alkanethiols adsorbed to gold and silver substrates. These surfaces provide the opportunity to explore how surface structure and packing density of alkane chains affect energy transfer in gas-surface collisions while maintaining the chemical nature of the surface. The chains pack standing up with 12 degrees and 30 degrees tilt angles relative to the surface normal and number densities of 18.9 and 21.5 A(2)molecule on the silver and gold substrates, respectively. For 7-kJmol argon scattering, the two surfaces behave equivalently, fully thermalizing all impinging argon atoms. In contrast, these self-assembled monolayers (SAMs) are not equally efficient at absorbing the excess translational energy from high-energy, 35 and 80 kJmol, argon collisions. When high-energy argon atoms are scattered from a SAM on silver, the fraction of atoms that reach thermal equilibrium with the surface and the average energy transferred to the surface are lower than for analogous SAMs on gold. In the case of argon atoms with 80 kJmol of translational energy scattering from long-chain SAMs, 60% and 45% of the atoms detected have reached thermal equilibrium with the monolayers on gold and silver surfaces, respectively. The differences in the scattering characteristics are attributed to excitation efficiencies of different types of surface modes. The high packing density of alkyl chains on silver restricts certain low-energy degrees of freedom from absorbing energy as efficiently as the lower-density monolayers. In addition, molecular-dynamics simulations reveal that the extent to which argon penetrates into the monolayer is related to packing density. For argon atoms with 80-kJmol incident energy, we find 16% and 7% of the atoms penetrate below the terminal methyl groups of C(10) SAMs on gold and silver, respectively.     

Near-IR luminescence of monolayer-protected metal clusters

Visible-near-IR luminescence spectra of gold MPCs that are similar, irrespective of the number of core atoms (all <2 nm diameter) and different monolayers, are reported. The luminescence can be quantitatively invoked by introducing polar ligands into nonpolar MPC monolayers and by galvanic exchange of metal atoms on the MPC core surface with different metals. The observed emissions are believed to result from surface-localized states that depend on both the core metal of the nanoparticle and the ligands attached to the metal surface.     

Synthesis and self-assembling properties on gold of 2-methyl-1,4-naphthoquinone derivatives containing ω-mercaptoalkylalkanoate groups

The synthesis of a series of 2-methyl-1,4-naphthoquinone (2-MeNQ) derivatives containing surface active ω-mercaptoalkylalkanoate groups with 5-12 atoms in the side-chains is reported. The compounds form stable self-assembled monolayers (SAMs) on gold. The complete reduction of the terminal 2-MeNQ group in the SAMs was confirmed by in situ Fourier-transform surface-enhanced Raman spectroscopy (FT-SERS). The basic electrochemical properties of the monolayers were determined by cyclic voltammetry (CV).     

Atomically dispersed copper species on ceria for the low-temperature water-gas shift reaction

The structure of copper species, dispersed on nanostructured ceria(particles, rods and cubes), was analyzed by scanning transmission electron microscopy(STEM) and X-ray photoelectron spectroscopy(XPS). It was interestingly found that the density of surface oxygen vacancies(or defect sites), induced by the shape of ceria, determined the geometrical structure and the chemical state of copper species. Atomically dispersed species and monolayers containing few to tens of atoms were formed on ceria particles and rods owing to the enriched anchoring sites, but copper clusters/particles co-existed, together with the highly dispersed atoms and monolayers, on cubic ceria. The atomically dispersed copper sites and monolayers interacted strongly with ceria, involving a remarkable charge transfer from copper to ceria at their interfaces. The activity for the low-temperature watergas shift reaction of the Cu/CeO_2 catalysts was associated with the fraction of the positively-charged copper atoms, demonstrating that the active sites could be tuned by dispersing Cu species on shape-controlled ceria particles.     

STM study of mixed alkanethiol/biphenylthiol self-assembled monolayers on Au(111)

A method is presented for depositing mixed self-assembled monolayers (SAMs) of dodecanethiol (C12) and 4'-methyl-1,1'-biphenyl-4-butane (H3C-C6H4-C6H4-(CH2)4-SH, BP4) by insertion of BP4 into a closely packed SAM of dodecanethiol on Au(111). Insertion takes place at defect sites such as domain boundaries or etch pits in the gold surface that are characteristic of C12 monolayers on gold. With a lower probability, insertion also occurs beside defect sites inside dodecanethiol domains. Insertion at defect sites results in domains of BP4, whereas insertion into C12 domains leads to isolated BP4 molecules. The isolated BP4 molecules are shown not to move at room temperature. By comparing the apparent height of the isolated BP4 molecules and BP4 domains, it is proposed that the isolated molecules have the same conformation as in the full-coverage phase. A simple two-layer model is proposed to characterize the current transport through BP4. The decay constant beta for the phenylene groups is deduced from the apparent STM heights of the inserted BP4 islands compared to the STM heights of the C12 closely packed monolayers.     

Electrochemical Fabrication of Nanostructured Surfaces for Enhanced Response

The objective of this work is to explore approaches to enhance electrochemical signals through sequential deposition and capping of gold particles. Gold nanoparticles are electrodeposited from KAuCl₄ solution under potentiostatic conditions on glassy carbon substrates. The number density of the nanoparticles is increased by multiple deposition steps. To prevent secondary nucleation processes, the nanoparticles are isolated after each potentiostatic deposition step by self‐assembled monolayers (SAMs) of decanethiol or mercaptoethanol. The increasing number of particles during five deposition/protection rounds is monitored by assembling electroactive SAMs using a ferrocene‐labeled alkanethiol. A precise estimation of the surface area of the gold nanoparticles by formation of an oxide layer on gold is difficult due to oxidation of the glassy carbon surface. As an alternative approach, the charge flow of the electroactive SAM is used for surface measurement of the gold surface area. A sixfold increase in the redox signal in comparison to a bulk gold surface is observed, and this increase in redox signal is particularly notable given that the surface area of the deposited nanoparticles is only a fraction of the bulk gold surface. After five rounds of deposition there is a gold loading of 1.94 μg cm^?2 of the deposited nanoparticles as compared to 23.68 μg cm^?2 for the bulk gold surface. Remarkably, however, the surface coverage of the ferrocene alkanethiol on the bulk material is only 10 % of that achieved on the deposited nanoparticles. This enhancement in signal of the nanoparticle‐modified surface in comparison to bulk gold is thus demonstrated not to be attributable to an increase in surface area, but rather to the inherent properties of the surface atoms of the nanoparticles, which are more reactive than the surface atoms of the bulk material.     

Carboranethiol-modified gold surfaces. A study and comparison of modified cluster and flat surfaces

Four different carboranethiol derivatives were used to modify the surfaces of gold nanoparticles and flat gold films. The novel materials engendered from these modifications are extraordinarily stable species with surfaces that support self-assembled monolayers of 1-(HS)-1,2-C2B10H11, 1,2-(HS)2-1,2-C2B10H10, 1,12-(HS)2-1,12-C2B10H10, and 9,12-(HS)2-1,2-C2B10H10, respectively. Surprisingly, characterization of these materials revealed that a number of molecules of the carboranethiol derivatives are incorporated inside the nanoparticles. This structural feature was studied using a number of techniques, including X-ray photoelectron spectroscopy (XPS), UV-vis, and IR spectroscopies. Thermal desorption experiments show that carborane molecules detach and leave the nanoparticle surface mostly as 1,2-C2B10H10 isotopic clusters, leaving sulfur atoms bound to the gold surface. The surfaces of both the gold nanoparticles and the flat gold films are densely packed with carboranethiolate units. One carborane cluster molecule occupies an area of six to seven surface gold atoms of the nanoparticle and eight surface gold atoms of the flat film. XPS data showed that molecules of 1,12-(HS)2-1,12-C2B10H10 bind to the flat gold surface with only half of the thiol groups due to the steric demands of the icosahedral carborane skeleton. Electrochemical measurements indicate complete coverage of the modified gold surfaces with the carboranethiol molecules.     

An Experimental and Theoretical Approach to Investigate the Effect of Chain Length on Aminothiol Adsorption and Assembly on Gold

Despite the numerous studies on the self‐assembled monolayers (SAMs) of alkylthiols on gold, the mechanisms involved, especially the nature and influence of the thiol–gold interface are still under debate. In this work the adsorption of aminothiols on Au(111) surfaces has been studied by using surface IR and X‐ray photoelectron spectroscopy (XPS) as well as by density functional theory (DFT) modeling. Two aminothiols were used, cysteamine (CEA) and mercaptoundecylamine (MUAM), which contain two and eleven carbon atoms, respectively. By combining experimental and theoretical methods, it was possible to draw a molecular picture of the thiol–gold interface. The long‐chain aminothiol produced better ordered SAMs, but, interestingly, the XPS data showed different sulfur binding environments depending on the alkyl chain length; an additional peak at low binding energy was observed upon CEA adsorption, which indicates the presence of sulfur in a different environment. DFT modeling showed that the positions of the sulfur atoms in the SAMs on gold with similar unit cells [(2√3×2√3)R30°] depended on the length of the alkyl chain. Short‐chain alkylthiol SAMs were adsorbed more strongly than long‐chain thiol SAMs and were shown to induce surface reconstruction by extracting atoms from the surface, possibly forming adatom/vacancy combinations that lead to the additional XPS peak. In the case of short alkylthiols, the thiol–gold interface governs the layer, CEA adsorbs strongly, and the mechanism is closer to single‐molecule adsorption than self‐assembly, whereas for long chains, interactions between alkyl chains drive the system to self‐assembly, leading to a higher level of SAM organization and restricting the influence of the sulfur–gold interface.     

Tyrosine derivatives assembled on gold

Two different tyrosine derivatives, one with the OH group free and one with the OH group phosphorylated, linked to 3-mercaptopropionic acid through an amide bond are adsorbed to gold surfaces. The adsorbates are studied by means of X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IRAS). The techniques are used to investigate the coordination to the surface and the molecular orientation of adsorbates relative to the surface. Molecular surface interactions, causing chemical shifts in the core level XPS spectra of the adsorbates on gold, are investigated using multilayer films as references. Angle-dependent XPS, XPS(theta), and IRAS are used to estimate molecular orientation relative to the surface. The tyrosine derivatives adsorb chemically to the surface through the sulfur atoms and highly organized monolayers are formed with the OH and the PO(2-)(3) exposed to the air/vacuum interface.