纳米结构自组装和分子自组装体系

系统地总结并评述了纳主结构和自组装体系和分子自组装体系的最新进展,介绍了纳米结构自组装和分子自组装的基本概念,总结了几类自组和分子自组装体系的合成方法,例举了这类自组装体系的新特性及与下一代纳米结构器件之间的联系。     

分子组装体的谱学研究

红外光谱、拉曼光谱、荧光光谱、紫外可见吸收光谱等是研究结构的主要手段。由于振动光谱得到的是力常数的信息 ,因而可以直接获得分子内、分子间键的信息 ,电子光谱则可以获取体系电子结构的信息 ,因而是分子组装体研究的重要方法手段。然而分子光谱也有其自身的限制 ,由于需要了解单层膜、单层膜与基底、单层膜与多层膜之间相互作用的信息 ,这些体系由于样品量小、信号弱 ,因此需要建立相应的适用于分子组装体的高灵敏度的特殊检测方法和实验技术 ,并发展分析分子间弱相互作用的光谱分析理论。本文综述了吉林大学超分子结构与谱学开放实验室近几年在超薄膜谱学方面的研究工作和进展。     

NaOH溶液表面PARC18自组装手性的变化

具有共轭结构的非手性分子在界面通过自组装能够形成手性超分子,这种自发对称性破缺的过程为解释生命起源提供了线索,相关研究具有重要的科学意义。目前,尽管文献中对于界面手性自组装的机理有了详细的探讨,但对于手性结构的动力学过程缺乏深入的研究。为了阐明界面自组装手性是否会随时间变化,利用二次谐波-线二色谱方法(SHG-LD)研究了偶氮苯衍生物PARC18在气/液界面的超分子自组装手性。结果表明,PARC18在纯水表面形成了手性状态稳定的宏观结构,而在亚相为NaOH溶液时,界面形成的手性结构状态随时间变化。此外,在纯水表面,谐波信号主要源于电偶极矩的贡献,而在NaOH溶液表面,磁偶极距对谐波信号,尤其是手性信号的贡献占主导。推测这是由于在碱性条件下,界面的PARC18分子发生构型异构化,分子中的两个发色团相互耦合,导致手性结构发生变化,同时增强了磁偶极的贡献。     

基于金纳米棒组装的半胱氨基酸分子同手性识别

摘要:本文通过半胱氨酸分子诱导金纳米棒自组装形成一维线性链状结构,利用停留装置观察了不同手性的半胱氨酸分子（L/D-半胱氨酸）诱导金纳米棒自组装的动力学过程。通过调控CTAB浓度,首次发现在组装速率很快的情况下,L-半胱氨酸分子诱导金纳米棒自组装的组装速率慢于D-半胱氨酸分子。而在组装速率较慢的情况下,这种情况不存在。通过分析揭示了为什么在慢速动力学和快速动力学会出现这种差异。并对在快速动力学下不同手性分子在诱导纳米颗粒组装上不同动力学行为作出讨论。这一工作可能为进一步解释生命的单一手性现象提供线索。     

基于金纳米棒组装的半胱氨基酸分子同手性识别

本文通过半胱氨酸分子诱导金纳米棒自组装形成一维线性链状结构,利用停留装置观察了不同手性的半胱氨酸分子(L/D-半胱氨酸)诱导金纳米棒自组装的动力学过程.通过调控CTAB浓度,首次发现在组装速率很快的情况下,L-半胱氨酸分子诱导金纳米棒自组装的组装速率慢于D-半胱氨酸分子.而在组装速率较慢的情况下,这种情况不存在.通过分析揭示了为什么在慢速动力学和快速动力学会出现这种差异.并对在快速动力学下不同手性分子在诱导纳米颗粒组装上不同动力学行为作出讨论.这一工作可能为进一步解释生命的单一手性现象提供线索.     

功能分子结构的组装和单分子物性:基于密度泛函理论的第一性原理计算与扫描隧道显微学(I)

在单个分子的层次上研究低维分子纳米结构的生长,理解组装机制并实现结构与特性的有效控制,是低维体系物理及其器件研究的重要内容。本文在基于密度泛函的第一性原理计算的基础上,对功能分子在金属表面上的自组装特性等进行了综述。对理论方法作了简要介绍后,综述了第一性原理计算方法在研究金属基底上分子自组装结构、界面特性、结构控制、单分子成像机制、单分子量子调控以及单分子输运性能等方面的应用。最后对基于密度泛函的第一性原理计算在解释功能分子组装与界面物理化学特性方面的发展前景进行了展望。     

DNA诱导金纳米粒子自组装及其SERS表征

首先将巯基DNA分子与金纳米粒子偶联,并用琼脂糖凝胶电泳分离出含不同DNA分子数目的金纳米粒子,最后将修饰有互补DNA链的Au纳米粒子进行组装,得到组装体(五聚体)。透射电子显微镜(TEM)研究表明,DNA-Au纳米组装体被成功地获得;表面增强拉曼光谱(SERS)研究表明,与未组装的金纳米粒子相比,DNA-Au纳米组装体具有更强的SERS活性。     

分子筛组装单质半导体碲的拉曼光谱

无机介孔材料MCM41是高有序,直孔道介孔分子筛,具有孔径约4nm的一维均匀孔道,孔壁厚约1nm,介孔体积可达40%,是一种很理想的组装材料主体。半导体碲位于第Ⅵ族,其六方相的晶格排列呈螺旋链状结构。本文采用固相合成反应方法,将单质半导体碲成功地组装在MCM41介孔分子筛中。在组装体中,单质半导体碲保持着六方相的晶体结构,其拉曼晶体振动表现出纳米晶体的结构特征。真空热处理实验表明,组装体具有良好的热稳定性。Te的六方相和所具有的独特的螺旋链状结构使Te分子很容易进入MCM41的直孔道内,同时MCM41均匀而规则的直孔道限制了Te螺旋链的随机排列,因而被组装在直孔道内的Te能螺旋链式生长,形成一维半导体纳米晶体,排列均匀,尺寸单一,具有稳定的空间构型     

基于Logistic函数模型的纳米自组装动力学分析

利用快速混合停流吸收(stopped-flow absorption)技术,研究了半胱氨酸分子介导的金纳米棒线性自组装过程的动力学性质.通过观测金纳米棒的表面等离激元动态吸收光谱,分析其自组装动力学行为及其与组装结构之间的关系.研究表明,传统的二阶反应动力学理论模型在描述金纳米棒自组装动力学行为上存在明显的局限性.由此,我们提出了基于Logistic函数的新的动力学分析模型.与传统的理论模型相比,新的理论模型具有更好的普适性,不仅适用于定量分析不同速率的金纳米棒自组装动力学特征,还提供了一种更加准确地描述组装初期动力学行为的方法.此外,这种新的动力学分析方法还有助于理解和建立金纳米棒组装动力学特征与组装体结构之间的关联.     

Self-assembly of Polyaniline: Mechanism Study

在水热环境下合成出\掺杂电荷诱导自组装纳米纤维阵列结构的聚苯胺平板,并通过一系列设计实验研究了这种自组装微观结构的形成机理,例如在反应溶液中引入不参与反应、对电荷组装起干扰作用的电解质,以及用计算模拟体系静电能与纳米纤维阵列夹角的相互关系等实验．实验结果发现,由掺杂离子引起的静电相互作用在形成聚苯胺自组装结构的过程中起了重要的作用．     

Quantitativer Vergleich von berechneten und gemessenen Elektronen-Energieverlustspektren an Silber

Energy loss measurements on the plasma loss of silver have been carried out with monochromatic 51 keV electrons. The loss spectra were compared with calculated ones. If retardation is taken into account, the intensity formula describes the experimental results correctly. The experiments were extended to silver foils with extremely fine crystallites. These films have a dielectric constant with a higher imaginary part (?₂) than the usual silver foils. The calculated spectra are again in good agreement with the observed ones, if retardation is taken into account.     

Coupled chemical reactions in dynamic nanometric confinement: Ag2O membrane formation during ion track etching

In this study, continuous swift heavy ion tracks in thin polymer foils were etched from both sides to create two conical nanopores opposing each other. Shortly before both cones merged, one of the nanopores was filled with a silver salt solution, whereas etching of the other cone continued. At the moment of track breakthrough, the etchant reacted with the silver salt solution by forming an impermeable and insulating membrane. Continued etching around the thus-created obstacle led to repetitive {etchant – silver salt solution} interactions. The coupling of the two chemical reactions, {etchant – polymer} and {etchant – silver salt solution}, within the confinement of etched tracks, with continuously changing shapes, showed a highly dynamic nature as recorded by measuring both the electrical current and the optical transmission across the foils. At low etching speeds, a central membrane that grew in radius and thickness with time until, at a critical thickness, the membrane became rather impermeable was formed. However, at high etching speeds, the emerging reaction products exhibited a sponge-like consistency, which allowed for their infinite growth. This precipitation was accompanied by a pronounced current spike formation. A simple theoretical model explains, at a minimum, the basic features.     

Use of chemical etching of CR-39 foils at elevated temperature for fast neutron personnel monitoring in India

CR-39 Solid State Nuclear Track Detecting foils (SSNTD), along with 1 mm thick polyethylene radiator, sealed in triple laminated pouches, are used for country wide Fast Neutron Personnel Monitoring in India. With the present system of processing by elevated temperature electrochemical etching (ETECE) and evaluation using automatic image analysis, only 16 foils are processed at a time and it is useful over the dose equivalent range 0.2 mSv to 10 mSv. It has been reported that, by processing CR-39 of good detection efficiency by chemical etching at elevated temperature, more numbers of foils can be processed simultaneously. In the present study, CR-39 foils from Pershore Moulding (UK) have been chemically etched using 7 N KOH under various conditions of temperature and etching durations and evaluated using high magnification microscope. The duration of chemical etching, has been optimized at a constant temperature of 60°C for chemical etching process. The characteristics of the chemically etched CR-39 foils are compared with the characteristics of the CR-39 foils processed by the existing system of ETECE and the detailed results are presented in the full text of the paper. It has been observed that by chemical etching process, the dose equivalent range of CR-39 foils can be extended above 60 mSv.      

Influence of silver nanoparticles on Er3+ up-conversion in CaF2 precipitated oxyfluoride glass-ceramics

The influence of silver nanoparticles on Er3＋ up-conversion in CaF2 precipitated oxyfluoride glass-ceramics is investigated. After heat-treatments, transmission electron microscopy images show that CaF2 nano- crystals precipitate in the glass matrix uniformity, and sliver nanoparticles are spread around the CaF2 nano-crystals simultaneously. Comparing with the samples without Ag doped, high efficiency up-conversion luminescences of Er3＋ at 540 and 658 nm are distinctly observed in the silver nanopartieles containing glass-ceramics by the 980-nm excitation. Moreover, since the intensity ratio of green and red emissions changes after silver nanopartieles precipitation, the up-conversion mechanism of Er3＋ is discussed.     

The pore opening process of etching polymer films irradiated by single and multiple heavy ions. The etching process in the range of the track core radius (10 nm)

The technique of electrochemical etching of irradiated polymer films is an useful method to investigate structures of the track cores. In the case of the investigation of multiple track foils, the mean effective radius corresponds to the average of all synchron etching pores. On the other hand, the etching cones of all tracks do not break through to conducting micro channels coincidentally. The statistical character of this pore opening (break through) process is still unexplained, although several effects concerning this topic have been observed in the past. Another computer program simulates by way of the Monte Carlo Method the etching process of an ensemble of tracks within a thin polymer film. The conductivity of the multiple track etching foil can be described by the convolution between the conductivity of a single pore and the time dependent breakthrough rate. By way of the Laplace Transforms the measurements of the multiple and single track etching polymer films can be deconvoluted and yield the statistical nature of the pore opening process.     

Energy loss dependent transversal etching rates of heavy ion tracks in plastic

By the method of electrolytical etching track etching rates V_t and corresponding transversal track etching rates V_trans of single heavy ion tracks in thin Makrofol KG foils have been measured at ion energies from 10–480 MeV/u. Makrofol KG foils of 8 μm thickness were irradiated perpendicular to the surface with ⁷⁹Au and ⁵⁴Xe ions at specific energies with energy loss values of REL=(10–90) ^*10³ MeVcm²/g at GSI Darmstadt, Germany, and Lawrence Berkeley Lab., Cal., USA. Using the electrolytical etching method by measuring the resistance of the foil during the etching process (etching conditions: 6n NaOH, room temperature and controlled 50° C) the breakthrough time and track etching rates V_t, V_trans and V_m (bulk etching rate) were analysed. Response curves (V_t/V_m)-1 as a function of Restricted Energy Loss (REL), the maximum extension of the ion induced damage perpendicular to the ion path and the dimension of the ion track core depending on the deposited energy can be estimated.     

惯性约束聚变实验用平面薄膜的制备及其表面图形的引入

平面薄膜是ICF分解实验的重要靶型,以半导体技术结合重掺杂自截止腐蚀制备厚度为3－4um的Si平面薄膜,以热蒸发结合脱膜工艺制备Al平面薄膜,两者的表面粗糙度分别为30nm和10nm左右;进一步采用离子束刻蚀在平面薄膜的表面引入网格或条状图形,获得测量成像系统像传递函数的刻蚀膜,控制离子束刻蚀工艺的参数以实现图形的精确转移。     

类Ni稀土X光激光波段衰减膜的设计与研究

 对类Ni稀土X光激光波段衰减膜进行了设计,并根据设计结果,利用磁控溅射和旋转涂覆法分别制备了自支撑的Ag衰减膜和聚苯乙烯(C₈H₈)衰减膜。利用真空α能谱测厚仪和α-step100台阶仪分别对衰减膜的质量厚度和均匀性进行了测量,用Auger电子能谱(A ES)对Ag衰减膜进行了表面杂质分析。     

Influence of preparation techniques on the structure of amorphous metallic alloy (Mo0.6Ru0.4)82B18

We report X-ray diffraction studies and density measurements on liquid quenched foils and sputter deposited films of the amorphous metallic alloy, (Mo_0.6Ru_0.4)₈₂B₁₈. The crystallization temperature (T_x) for both the films and the foils is ～800 ± 10°C. The density of the as-sputtered films is ～4% less than that of the foils. The annealing of these films at $\text{～}\text{T}{}_{\mathrm{x}}\text{2}$ increases the density to within ～1.7% of the value for the foils. The X-ray diffractionpatterns for both the foils and films are similar and show the amorphous nature of the samples. The reduced radial distribution functions suggest that as-sputtered films have noticably larger second and third nearest neighbor distances, probably due to excess residual stresses and voids in them.     

Crystallization and surface segregation in CuIn0.7Ga0.3Se2 thin films on Cu foils grown by pulsed laser deposition

This work reports unexpected crystallization and segregation behavior of CuIn_0.7Ga_0.3Se₂ (CIGS) thin films deposited on flexible Cu foils by pulsed laser deposition. A composite-type microstructure containing nanometer-scaled CIGS crystallites embedded in amorphous Cu-rich matrix is observed even at the high temperature of 500 °C. The findings are attributed to very fast condensation of the ablated species and random nucleation induced from the amorphous matrix. Cu-rich particulates tend to precipitate on the film surface, and their average size, shape, number density and composition exhibit a strong dependence on the substrate temperature up to 500 °C. The similar crystallization properties of the films on Cu foils and glass substrates are noticeable to the use of Cu foils for flexible solar cells.