聚合物纳米复合材料微孔发泡成型技术的研究进展

介绍了一种结合纳米材料和微孔发泡两种技术得到的设计和控制微孔结构的新技术,并详细介绍了该技术的最新进展。     

生物大分子介导仿生矿化制备磁性纳米粒子的研究进展

相比其他纳米材料,磁铁矿（Fe₃O₄）纳米粒子由于具有磁响应性而被广泛应用于酶固定化、定向给药及核酸提取等方面。不同大小和形状的磁铁矿纳米颗粒可用于不同的领域,如晶体尺寸越小的Fe₃O₄对人体副作用越小,有望用于疾病高效、靶向治疗。近年来,控制Fe₃O₄纳米粒子大小和形貌的新方法研究逐步成为热点。因此,本文回顾了传统的共沉淀制备磁性纳米颗粒的方法,这些方法需要使用有机溶剂或高温等条件控制,介绍了这些方法存在的环境污染和安全性问题。在此基础上,本文深入介绍了近年来出现的一种受自然界生物矿化启发的生物大分子介导的仿生矿化制备磁性纳米粒子的新趋势,综述了生物大分子蛋白质（或多肽）介导的仿生矿化的最新研究进展,阐释了该方法在磁铁矿（Fe₃O₄）纳米粒子的大小和形貌控制方面的优缺点,并对其应用前景及面临的挑战进行了展望。     

聚碳酸酯微孔泡沫塑料研究进展

阐述了聚碳酸酯(PC)微孔泡沫塑料的制备方法,包括间歇成型法、连续挤出成型法、模压成型法;综述了PC纳米复合微孔泡沫塑料的制备;介绍了PC微孔泡沫塑料的拉伸性能、疲劳性能、时温效应及电性能;并提出了PC微孔泡沫塑料的应用前景和研究方向。     

纳米结构TiO2微孔复合膜的研制

本文用异丙醇钛经溶胶－凝胶过程制得了二氧化钛粒子溶胶，确定成膜时的烧结温度，制得的膜经SEM测试具有典型的不对称结构，用压汞法测量孔径分布在2．7－11nm范围内。     

纳米流体中纳米颗粒微运动的分子动力学模拟

建立了以水分子为基础液、以铜纳米颗粒为悬浮粒子的纳米流体模型,利用分子动力学模拟方法对纳米颗粒的微运动行为进行分析。研究发现纳米颗粒在基础液中具有高速的随机旋转与平移运动,旋转运动的角速度为1×10⁹~1×10¹⁰ rad·s^-1,平移运动的速度为1~10 m·s^-1。纳米流体速度分布与温度分布主要区别于单相基础液的位置在近壁面附近,纳米流体无论是速度梯度还是温度梯度均比单相流体的情况大,其主要原因是纳米颗粒在基础液中的随机运动,而改变的流体速度特性又会进一步影响传热过程。     

碳基纳米填料增强微孔发泡电磁屏蔽材料的研究进展

航空航天等新兴行业以及电子等领先行业的发展对聚合物特殊性能的要求越来越高,将微孔发泡和具有功能特性的碳基纳米填料结合形成的导电聚合物泡沫具有优异的电子传输特性,有利于在较低渗透阈值下获得均匀的导电网络,提高材料的电导率与介电常数,在电磁屏蔽等领域有广阔的应用前景.介绍了导电复合材料的电磁屏蔽原理以及碳基纳米填料与发泡的...     

新型耐迁移橡胶防老剂的研究进展

首先介绍了橡胶防老剂的相关理论研究,橡胶材料老化的本质为自由基反应,其防护机理主要是抑制自由基的形成,实验研究集中于差示扫描量热、核磁、紫外分光、红外光谱等分析橡胶材料以及防老剂的结构变化,而理论研究则集中于分子模拟,包括解离能、溶解度、均方位移等参数计算。其次,通过对国内外商业化橡胶防老剂的使用现状进行追踪,分析了新型橡胶防老剂的开发与应用情况,包括胺类防老剂的改性方法、防老剂的复配研究以及具备特殊功能的新型防老剂应用等,结合几类耐迁移橡胶防老剂的结构特点和应用结果,指出具备耐迁移和低毒性等特点的新型橡胶防老剂是未来发展方向。最后,总结了新型耐迁移橡胶防老剂应集中于发挥防老剂大分子化和多官能化的协同作用,可以更好地适应橡胶工业的持续发展。     

微孔纳米复合塑料的研究进展

综述微孔纳米复合塑料的成型方法、介绍微孔纳米复合塑料成型时所用的发泡剂以及特点,分析纳米填料对纳米复合微孔塑料泡孔结构的影响,综述纳米填料对纳米复合微孔塑料性能的影响,并对聚合物纳米微孔发泡塑料的研究及应用前景进行展望.     

共轭微孔聚合物材料的研究进展

共轭微孔聚合物(CMPs)是一类由共价键结合的3D网络结构化合物,由于其热稳定性好,比表面积高以及结构可控等优点,作为一类具有潜在应用前景的多孔材料日益受到重视。重点介绍了CMPs的性质、制备方法和综合应用,并对CMPs在储氢方面存在的不足和未来的研究方向做出了总结和展望。     

分子模拟二氧化碳在狭缝炭微孔中的吸附

Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.     

Polymer translocation through a nanopore in mesoscopic simulations

Dissipative particle dynamics (DPD) simulations are carried out to study the translocation of a single polymer chain through a pore under fluid field. The influences of the field strength E, the chain length N, the solvent quality α_sp, and the pore size h on the translocation time are evaluated. The translocation time τ, which is defined as the time that the chain moves through the pore completely in the direction of the driving force, scales with the field strength E as τ ∼ E^{−0.48±0.01}. We find that the translocation time is proportional to the chain length, which is in agreement with the experimental results and theoretical predictions. Tracing the variation of the square radius of gyration, , and the polymer configuration during translocation, we observe that the chain is elongated when it is passing through the pore, which manifests that the chain is not in equilibrium during the translocation process. We also find that the worse the solvent quality is, the less time it will take to translocate, no matter what the size of the pore is. If the size of the pore is enlarged, the translocation time will be shorter. The information we gain from this study may benefit to the DNA sequencing.     

Electrically facilitated translocation of protein through solid nanopore

Nanopores have been proven as versatile single-molecule sensors for individual unlabeled biopolymer detection and characterization. In the present work, a relative large nanopore with a diameter of about 60 nm has been used to detect protein translocation driven by a series of applied voltages. Compared with previous studied small nanopores, a distinct profile of protein translocation through a larger nanopore has been characterized. First, a higher threshold voltage is required to drive proteins into the large nanopore. With the increase of voltages, the capture frequency of protein into the nanopore has been markedly enhanced. And the distribution of current blockage events is characterized as a function of biased voltages. Due to the large dimension of the nanopore, the adsorption and desorption phenomenon of proteins observed with a prolonged dwell time has been weakened in our work. Nevertheless, the protein can still be stretched into an unfolded state by increased electric forces at high voltages. In consideration of the high throughput of the large nanopore, a couple of proteins passing through the nanopore simultaneously occur at high voltage. As a new feature, the feasibility and specificity of a nanopore with distinct geometry have been demonstrated for sensing protein translocation, which broadly expand the application of nanopore devices.     

Voltage-driven translocation behaviors of IgG molecule through nanopore arrays

Nanopore-based biosensing has attracted more and more interests in the past years, which is also regarded as an emerging field with major impact on bio-analysis and fundamental understanding of nanoscale interactions down to single-molecule level. In this work, the voltage-driven translocation properties of goat antibody to human immunoglobulin G (IgG) are investigated using nanopore arrays in polycarbonate membranes. Obviously, the background ionic currents are modulated by IgG molecules for their physical place-holding effect. However, the detected ionic currents do ‘not’ continuously decrease as conceived; the currents first decrease, then increase, and finally stabilize with increasing IgG concentration. To understand this phenomenon, a simplified model is suggested, and the calculated results contribute to the understanding of the abnormal phenomenon in the actual ionic current changing tendency.     

Slowing and controlling the translocation of DNA in a solid-state nanopore

DNA sequencing methods based on nanopores could potentially represent a low-cost and high-throughput pathway to practical genomics, by replacing current sequencing methods based on synthesis that are limited in speed and cost. The success of nanopore sequencing techniques requires the solution to two fundamental problems: (1) sensing each nucleotide of a DNA strand, in sequence, as it passes through a nanopore; (2) delivering each nucleotide in a DNA strand, in turn, to a sensing site within the nanopore in a controlled manner. It has been demonstrated that a DNA nucleotide can be sensed using electric signals, such as ionic current changes caused by nucleotide blockage at a constriction region in a protein pore or a tunneling current through the nucleotide-bridged gap of two nanoelectrodes built near a solid-state nanopore. However, it is not yet clear how each nucleotide in a DNA strand can be delivered in turn to a sensing site and held there for a sufficient time to ensure high fidelity sensing. This latter problem has been addressed by modifying macroscopic properties, such as a solvent viscosity, ion concentration or temperature. Also, the DNA transistor, a solid state nanopore dressed with a series of metal-dielectric layers has been proposed as a solution. Molecular dynamics simulations provide the means to study and to understand DNA transport in nanopores microscopically. In this article, we review computational studies on how to slow down and control the DNA translocation through a solid-state nanopore.     

Electrokinetic DNA transport in a nanopore membrane

There is tremendous current interest in transporting DNA molecules through nanopores. This interest stems from the possibility of using nanopores for characterization/sequencing, separation, and sensing of DNA. In the presence of a transmembrane electric field, typically used in such applications, DNA chains can be driven through the nanopore via the electrokinetic transport processes of electrophoresis and electroosmotic flow, as well as by diffusion. To our knowledge there have been no quantitative studies of the relative importance of the electrokinetic and diffusive components for DNA transport in a nanopore system. We describe such quantitative studies here. We report on the transport of a series of single-stranded homo-oligonucleotides made of thymidine bases through nanopores in a polycarbonate filter membrane. We show that when an ionic current is passed through the nanopores, transmembrane DNA electrophoresis is the dominant transport process. Finally, the pores in these membranes have conical constrictions at both membrane faces. The effect of this interesting pore geometry on DNA transport is also discussed.     

Translocation of compact polymer chains through a nanopore

We perform dynamical Monte Carlo simulation to study the forced translocation of compact polymer chains in three-dimensional lattices. The chains are driven through a nanopore connecting two infinite channels by an external field. The scaling properties of average translocation time τ and translocation time distribution (TTD) are studied. The effects of contact energy (?_C), electric field strength (E), and nanopore width (L) on the scaling exponent (α) of average translocation time τ ∼ N^α and the TTD are investigated. For the scaling behavior of τ ∼ N^α, we have found that there is no crossover behavior with weak field strength when the nanopore width is one lattice spacing, which is less than average bond length, while crossover behaviors are observed for larger nanopore widths. The scaling exponent α also depends on contact energy ?_C and electric field strength E. For the TTD, it shifts from the Gaussian to a right-skew distribution with the electric field E increasing for short chains; while for long chains, multi-peak distributions are observed. As a primary and simple model, compact polymer chains are extensively used to capture the structure and thermodynamic properties of proteins, therefore we can investigate the protein translocation by simulating compact chain translocation, and this study will be useful for exploring the complex translocation behaviors of proteins.     

Fast and automatic processing of multi-level events in nanopore translocation experiments

We have developed a method to analyze in detail, translocation events providing a novel and flexible tool for data analysis of nanopore experiments. Our program, called OpenNanopore, is based on the cumulative sums algorithm (CUSUM algorithm). This algorithm is an abrupt change detection algorithm that provides fitting of current blockages, allowing the user to easily identify the different levels in each event. Our method detects events using adaptive thresholds that adapt to low-frequency variations in the baseline. After event identification, our method uses the CUSUM algorithm to fit the levels inside every event and automatically extracts their time and amplitude information. This facilitates the statistical analysis of an event population with a given number of levels. The obtained information improves the interpretation of interactions between the molecule and nanopore. Since our program does not require any prior information about the analyzed molecules, novel molecule-nanopore interactions can be characterized. In addition our program is very fast and stable. With the progress in fabrication and control of the translocation speed, in the near future, our program could be useful in identification of the different bases of DNA.     

细菌DNA疫苗的研究进展

DNA疫苗是20世纪90年代初出现的一种新型疫苗,近年来发展迅速,在预防和治疗病毒性疾病及肿瘤等方面效果显著。随着DNA疫苗研究的不断深入,很多细菌DNA疫苗相继出现。本文就细菌DNA疫苗的研究进展作一综述。     

DNA纳米组装的研究进展

DNA参与的纳米组装的研究是近年来在化学,生物学和材料科学领域广受关注的研究方向之一。由于所获得的纳米组装体具有系列特殊的环境响应和量子效应,在生物检测,诊断和传感等方面相对于传统材料均表现高的效率,具有潜在的应用前景。对该领域的研究工作作了比较详细的总结并按照其特点对工作内容进行了分类阐述。