Constructing Thin Polythiophene Film Composed of Aligned Lamellae via Controlled Solvent Vapor Treatment

Thin poly(3-butylthiophene) (P3BT) film composed of aligned lamellae attached to the edge of the original film has been achieved via a controlled solvent vapor treatment (C-SVT) method. The polarized optical microscopy operated at both single-polarization and cross-polarization modes has been used to investigate the alignment of the fiber-like lamellae. A numerical simulation method is used to quantitatively calculate angle distributions of the lamellae deviated from the film growth direction. Prepatterned P3BT film edge acts as nuclei which densely initialize subsequent crystal growth by exhausting the materials transported from the partially dissolved film. The growth of new film upon crystallization is actually a self-healing process where the two-dimensional geometric confinement is mainly responsible for this parallel alignment of P3BT crystals. The solvent vapor pressure should be carefully chosen so as to induce crystal growth but avoid liquid instability which will destroy the continuity of the film.

群组通信环境中的密钥管理协议

随着群组通信业务的普及，群组通信的相关安全研究也随之兴起。群组密码学的概念首先由 Desmedt 提出。与传统通信中的密码学方案相比，群组密码学具有很多优点，并已经成功地运用到视频点播和分布式系统等一些应用场景中。群签名，环签名，广播加密等密码学体制作为群组密码学的重要分支都得到了学术界的密切关注。本文的研究工作集中在群组密码学的一个重要组成部分：群组密钥管理，即多个（群组）用户在不安全的开放网络环境中通过一定的协议产生一个共享的会话密钥，为后面的通信提供各种安全性保护。 本文的研究工作主要包含两个方面，群组密钥分发协议和可证明安全的认证群组密钥协商协议。在对已有的群组密钥管理方案进行了大量的调查与分析后，我们在此基础上提出了一些有价值的研究成果。本文的主要成果包括： 1. 在第二章中，提出了一种高效的长期 self-healing 群组密钥分发方案。和已有方案相比，新方案的优势包括：（1）我们避免了使用指数运算, 而只是域上多项式的相关运算；（2）群组管理者广播消息次数比 Staddon 等人和Blundo 等人的方案少一次；（3）用户端存储私钥数目比 Staddon 等人的方案少将近一半；（4）新协议的安全性为无条件安全。 2. 在第三章中，构造了一个从一般群组密钥协商协议向基于口令认证的群组密钥协商协议转换的编译器。编译器的构造利用了对称加密体制，NM-CCA2 和 IK-CCA2 安全的公钥加密体制，以及 UF-CMA 安全的数字签名体制，从而使得编译器可以避免在线/离线字典攻击。 3. 在第四章中，提出了一个基于口令认证的群组密钥协商协议，使得网关在认证服务器的协助下和多个用户之间建立一个会话密钥，同时认证服务器不知道此会话密钥的任何信息（网关和认证服务器之间的信道是专用信道）。由于意识到口令的泄露往往是由于用户的不当使用造成的，所以，不同于已有的基于口令认证的门限密钥协商机制，我们的门限方案是在用户端实施。我们的门限方案要求把用户群组和认证服务器预先共享的口令（称之为群组口令）以秘密共享方式分散共享在群组用户之间，并且每个用户所存储口令的子秘密（share）值依然是一个易记忆的口令（称之为用户口令）。只有不少于 k 个用户一起才能恢复出群组口令。 4. 在第五章中，利用了Unified 模型（把用户长期私钥嵌入到密钥协商过程）构造了一个在 Strong Corruption 模型下可证明安全的强健的认证群组密钥协商协议。和已有类似方案相比，新方案所需要的签名数量明显减少，从而，计算复杂度和通信复杂度也随之降低。另外，新协议是在 Strong Corruption 模型下可证明安全，在此模型下的类似协议比较少。 5. 在第六章中，对 Desmedt 等人提出的 BD-II（树型）群组密钥协商协议做出改进。利用在树中各个节点上应用遮罩函数，我们把由于群组关系变化而对密钥更新所产生的影响限制在一个比较小的群组范围中，从而提高了协议在动态情况下运行的效率。新协议通过四个子算法：初始化，成员加入，成员撤销，子群组合并来分别应对群组密钥协商过程中所遇到的各种（动态）情况。

Rapidly Infrared-Assisted Cooperatively Self-Assembled Highly Ordered Multiscale Porous Materials

In this paper, cooperative self-assembly (CSA) of colloidal spheres with different sizes was studied. It was found that a complicated jamming effect makes it difficult to achieve an optimal self-assembling condition for construction of a well-ordered stacking of colloidal spheres in a relatively short growth time by CSA. Through the use of a characteristic infrared (IR) technique to significantly accelerate local evaporation on the growing interface without changing the bulk growing environment, a concise three-parameter (temperature, pressure, and IR intensity) CSA method to effectively overcome the jamming effect has been developed. Mono- and multiscale inverse opals in a large range of lattice scales can be prepared within a growth time (15-30 min) that is remarkably shorter than the growth times of several hours for previous methods. Scanning electron microscopy images and transmittance spectra demonstrated the superior crystalline and optical qualities of the resulting materials. More importantly, the new method enables optimal conditions for CSA without limitations on sizes and materials of multiple colloids. This strategy not only makes a meaningful advance in the applicability and universality of colloidal crystals and ordered porous materials but also can be an inspiration to the self-assembly systems widely used in many other fields, such as nanotechnology and molecular bioengineering.

Nucleobase-metal hybrid materials: Preparation of submicrometer-scale, spherical colloidal particles of adenine-gold(III) via a supramolecular hierarchical self-assembly approach

We report a simple and effective supramolecular route for facile synthesis of submicrometer-scale, hierarchically self-assembled spherical colloidal particles of adenine - gold(III) hybrid materials at room temperature. Simple mixture of the precursor aqueous solutions of adenine and HAuCl4 at room temperature could result in spontaneous formation of the hybrid colloidal particles. Optimization of the experimental conditions could yield uniform-sized, self-assembled products at 1:4 molar ration of adenine to HAuCl4. Transmission electron microscopy results reveal the formation of hierarchical self-assembled structure of the as-prepared colloidal particles. Concentration dependence, ratio dependence, time dependence, and kinetic measurements have been investigated. Moreover, spectroscopic evidence [i.e., Fourier transform infrared (FTIR) and UV-vis spectra and wide-angle X-ray scattering data] of the interaction motives causing the formation of the colloidal particles is also presented.

Thermal annealing of Au nanorod self-assembled nanostructured materials: Morphology and optical properties

Three-dimensional Au nanorod and An nanoparticle nanostructured materials were prepared by layer-by-layer self-assembly. The plasmonic properties of the An nanorod and An nanoparticle self-assembled nanostructured materials (abbreviated as AuNR and AuNP SANMs) are tunable by the controlled self-assenibly process. The effect of thermal annealing at 180 and 500 degrees C to the morphologies, plasmonic properties and surface-enhanced Raman scattering (SERS) responses of these SANMs were investigated. According to the experimental results, these properties correlate with the structure of the SANMs.

Two- and three-dimensional Au nanoparticle/CoTMPyP self-assembled nanotructured materials: Film structure, tunable electrocatalytic activity, and plasmonic properties

Two- and three-dimensional Au nanoparticle/[tetrakis(N-methylpyridyl)porphyrinato]cobalt (CoTMPyP) nanostructured materials were prepared by "bottom-up" self-assembly. The electrocatalytic and plasmonic properties of the Au nanoparticle/CoTMPyP self-assembled nanostructured materials (abbreviated as Au/CoTMPyP SANMs) are tunable by controlled self-assembly of the An nanoparticles and CoTMPyP on indium tin oxide (ITO) electrode. The electrocatalytic activity of the Au/CoTMPyP SANMs can be tuned in two ways. One way is that citrate-stabilized An nanoparticles are positioned first on ITO surface with tunable number density, and then positively charged CoTMPyP ions are planted selectively on these gold sites. The other way is that An nanoparticles and CoTMPyP are deposited by virtue of layer-by-layer assembly, which can also tune the amount of the as-deposited electrocatalysts. FE-SEM studies showed that three-dimensional SANMs grow in the lateral expansion mode, and thermal annealing resulted in both surface diffusion of nanoparticles and atomic rearrangement to generate larger gold nanostructures with predominant (I 11) facets.

Mechanical effects of the self-organization of dislocations and related critical characteristics

The effects of the dislocation pattern formed due to the self-organization of the dislocations in crystals on the macroscopic hardening and dynamic internal friction (DIF) during deformation are studied. The classic dislocation models for the hardening and DIF corresponding to the homogeneous dislocation configuration are extended to the case for the non-homogeneous one. In addition, using the result of dislocation patterning deduced from the non-linear dlislocation dynamics model for single slip, the correlation between the dislocation pattern and hardening as well as DIF is obtained. It is shown that in the case of the tension with a constant strain rate, the bifurcation point of dislocation patterning corresponds to the turning point in the stress versus strain and DIF versus strain curves. This result along with the critical characteristics of the macroscopic behavior near the bifurcation point is microscopically and macroscopically in agreement with the experimental findings on mono-crystalline pure aluminum at temperatures around 0.5T(m). The present study suggests that measuring the DIF would be a sensitive and useful mechanical means in order to study the critical phenomenon of materials during deformation.

Pressure Controlled Self-Assembly of High Quality Three-Dimensional Colloidal Photonic Crystals

A concise pressure controlled isothermal heating vertical deposition (PCIHVD) method is developed, which provides an optimal growing condition with better stability and reproducibility for fabricating photonic crystals (PCs) without the limitation of colloidal sphere materials and sizes. High quality PCs are fabricated with PCIHVD from polystyrene spheres with diameters ranging from 200 nm to 1 mu m. The deep photonic band gap and steep photonic band edge of the samples are most favorable for realizing ultrafast optical devices, photonic chips, and communications. This method makes a meaningful advance in the quality and diversity of PCs and greatly promotes their wide applications.

A generalized model for the effective thermal conductivity of porous media based on self-similarity

A generalized model for the effective thermal conductivity of porous media is derived based on the fact that statistical self-similarity exists in porous media. The proposed model assumes that porous media consist of two portions: randomly distributed non-touching particles and self-similarly distributed particles contacting each other with resistance. The latter are simulated by Sierpinski carpets with side length L = 13 and cutout size C = 3, 5, 7 and 9, respectively, depending upon the porosity concerned. Recursive formulae are presented and expressed as a function of porosity, ratio of areas, ratio of component thermal conductivities and contact resistance, and there is no empirical constant and every parameter has a clear physical meaning. The model predictions are compared with the existing experimental data, and good agreement is found in a wide range of porosity of 0.14-0.80, and this verifies the validity of the proposed model.