絮凝基因的克隆及其絮凝形态表征

分离出一株具有强絮凝特性的芽孢杆菌Bacillus sp. F2, 其絮凝率达到84%, 并构建了絮凝基因组文库, 从中筛选并获得表达絮凝活性的大肠杆菌阳性克隆子FC2. 絮凝试验测定FC2的絮凝率为90%, 稍高于原絮凝菌F2, 高于受体菌JM109(6.9%), 说明FC2絮凝性状遗传于原絮凝菌F2. 采用轻敲模式下的原子力显微镜成像技术、光学显微镜、ζ电位等对加入FC2与F2及不加入絮凝剂的絮凝微观形貌等进行了测定. 原子力显微成像显示, 加入克隆菌FC2发酵液的高岭土悬浮液形成的絮凝胶体出现大而紧密的球形颗粒结构, 且表面积粗糙, 凹凸程度大, 具有大的比表面积和吸附液体悬浮颗粒的能力. 向高岭土悬浮液中加入克隆菌FC2发酵液后, 絮凝颗粒由松散的不定形结构转变为密集分布、 水平尺寸均匀的球形结构, 表明克隆菌FC2发酵液中的凝集素容易以高岭土悬浮颗粒为中心吸附在其表面, 而且絮凝率达到90%, 进一步证实了克隆菌FC2发酵液的除污染效能. ζ电位测定结果表明, 离子键作用强度不同, 致使絮凝形态存在差异, 为研究生物絮凝剂的絮凝机理提供了有力的依据.     

Planning and control of 3-D nano-manipulation

The use of atomic force microscope (AFM) as a nanomanipulator has been evolving for various kinds of nano-manipulation tasks. Due to the bow effect of the piezo scanner of the AFM, the AFM space is different from the Cartesian space. Traditional nanomanipulation based on AFM is only a 2-D operation and does not consider the bow effect of the piezotube. In this paper, different 3-D nanomanipulation tasks using AFM such as nanolithography, pushing and cutting have been discussed. 3-D path planning is performed directly in the AFM space and the 3-D paths are generated based on the 3-D topography information of the surface represented in the AFM space. This approach can avoid the mappings between the AFM space and Cartesian space in planning. By following the generated motion paths, the tip can either follow the topography of the surface or move across the surface by avoiding collision with bumps. Nanomanipulation using this method can be considered as the “true“ 3-D operations since the cantilever tip can be controlled to follow any desired 3-D trajectory within the range of AFM space. The experimental study shows the effectiveness of the planning and control scheme.     

石墨氧化物分子沉积膜的制备及其摩擦学行为研究

采用分子沉积技术制备了石墨氧化物（GO）－聚二丙烯二甲铵（PDDA）多层超薄膜，用紫外和红外光谱对超薄膜的结构进行了分析，用原了力显微镜考察了薄膜的表面形貌及纳米摩擦学行为。结果表明：石墨氧化物分子沉积膜可以降低玻璃表面的摩擦系数；其摩擦系数随载荷增大而降低；该分子沉积薄膜良好的润滑性能归因于其较低的表面剪切强度。     

Surface Behavior of Polyamide 6 Modified by Barrier Plasma in Oxygen and Nitrogen

Polyamide (PA) 6 was modified by diffuse coplanar surface barrier discharge (DCSBD) plasma in an atmosphere of nitrogen and oxygen. The surface roughness decrease of PA 6 was detected by AFM and nano-indentation after modification in DCSBD plasma. A significant increase in O/C and N/C ratios of plasma-modified PA 6 using XPS analysis was found. The results show the importance of introducing oxygenic polar functional groups on the polymeric surface in order to increase its surface energy during a short time of plasma activation. The modification of PA 6 by DCSBD oxygen plasma was more efficient than by nitrogen plasma.     

Atomic Force Microscopic Investigations of Fibrils Formed by Complexation of Monochelic Polystyrenic Porphyrin and PEGylated Fullerene (C60)

Atomic force microscopic studies have been conducted for insight into the morphological aspects of monochelic porphyrin and fullerene complexes forming fibrils of continuous nature. Alternating dark and bright segments could be envisioned clearly, as individual porphyrin-fullerene repeating units. These fibrils also caused a remarkable red shift in the soret band absorption of porphyrin. Dynamic light scattering analysis was also conducted under different solvent conditions, which showed the swelling of fibrils when the solvent was changed from THF to water.     

Closing the Nanographene Gap: Surface‐Assisted Synthesis of Peripentacene from 6,6′‐Bipentacene Precursors

The thermally induced cyclodehydrogenation reaction of 6,6′‐bipentacene precursors on Au(111) yields peripentacene stabilized by surface interactions with the underlying metallic substrate. STM and atomic‐resolution non‐contact AFM imaging reveal rectangular flakes of nanographene featuring parallel pairs of zig‐zag and armchair edges resulting from the lateral fusion of two pentacene subunits. The synthesis of a novel molecular precursor 6,6′‐bipentacene, itself a synthetic target of interest for optical and electronic applications, is also reported. The scalable synthetic strategy promises to afford access to a structurally diverse class of extended periacenes and related polycyclic aromatic hydrocarbons as advanced materials for electronic, spintronic, optical, and magnetic devices.     

Layer‐by‐layer assembly of weak‐strong copolymer polyelectrolytes: A route to morphological control of thin films

Multilayer films were assembled from a strong polyelectrolyte (poly(diallyldimethylammonium chloride), PDADMAC) and a copolymer containing both strongly charged styrene sulfonate moieties and weakly charged maleic acid moieties (poly(4‐styrenesulfonic acid‐co‐maleic acid), PSSMA). Growth of PSSMA/PDADMAC multilayers was linear, as characterized by UV‐vis spectroscopy and quartz crystal microgravimetry. The influence of both the pH of the PSSMA adsorption solutions and the ratio of SS:MA in the PSSMA on multilayer properties was investigated. Fourier transform infrared spectroscopy results showed that the ionization of carboxylic acid groups in PSSMA/PDADMAC multilayers did not vary significantly with changes in the PSSMA assembly pH. However, the multilayers showed different thicknesses, surface morphologies, and stability to post‐assembly pH treatment. We also demonstrate that PSSMA/PDADMAC multilayers are significantly more stable than PSSMA/PAH multilayers after post‐assembly pH treatment (i.e. the films remain intact when exposed to pH extremes). In addition, the surface morphology of two films (PSSMA 1:1 assembled at pH 5.8, post‐treated at pH 2 and PSSMA 3:1 assembled at pH 5.8, post‐treated at pH 11) changed significantly when the films were exposed to solutions of different pH and, in the former case, this change in film morphology was reversible. The porous morphology after treatment at pH 2 could be reversed to give a significantly smoother film after subsequent exposure to water for 24 h. Our results demonstrate that by the rational choice of the assembly pH of PSSMA, stable and pH‐responsive films can be obtained via the sequential assembly of PSSMA and PDADMAC. These films have potential in controlled release applications where film stability and pH‐responsive behavior are essential. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4341‐4351, 2007     

Hybrid Materials from Carbon Nanotubes,Nickel Tetrasulfonated Phthalocyanine and Thin Polymer Layers for the Selective Electrochemical Activation of Nitric Oxide in Solution

The elaboration of hybrid materials from single‐wall carbon nanotubes (SWCNT) and tetrasulfonated nickel phthalocyanine (NiTSPc) was electrochemically performed to obtain chemically modified electrodes with improved electrocatalytic activity towards the electrooxidation of nitric oxide (NO). The characterization of these hybrid electrodes was achieved by cyclic voltammetry and AFM. The electrochemical performances of the electrodes towards the oxidation of NO were then analyzed by chronoamperometry and the obtained results show that the presence of SWCNT greatly enhances the electrocatalytic performances in terms of current intensity. Additional coatings were then electrodeposited over the hybrid electrodes to act as selective membranes against four major interfering analytes: nitrite, ascorbate, hydrogen peroxide and L ‐arginine. Several polymer coatings were tested to achieve the best balance between sensitivity to NO and selectivity against interferents.     

Branched poly(styrene‐b‐tert‐butyl acrylate) and poly(styrene‐b‐acrylic acid) by ATRP from a dendritic poly(propylene imine)(NH2)64 core

With the aim of creating highly branched amphiphilic block copolymers, the primary amine end groups of the poly(propylene imine) dendrimers DAB‐dendr‐(NH₂)₈ and DAB‐dendr‐(NH₂)₆₄ were converted to 2‐bromoisobutyramide groups. Poly (styrene‐b‐tert‐butyl methacrylate) (PS‐b‐PtBMA) was synthesized by ATRP from the eight end group initiator, and poly(styrene‐b‐tert‐butyl acrylate) (PS‐b‐PtBA) was synthesized from the 64 end group initiator. The tert‐butyl groups were removed to produce poly(styrene‐b‐methacrylic acid) (PS‐b‐PMAA) and poly(styrene‐b‐acrylic acid) (PS‐b‐PAA). Comparison of size exclusion chromatography (SEC) absolute molecular weight analyses of the polystyrenes with calculated molecular weights showed that the eight end group initiator produced a polystyrene with about eight branches, and that the 64 end group initiator produced polystyrene with many fewer than 64 branches. The PS‐b‐PtBA materials also have many fewer than 64 branches. The PS‐b‐PAA samples dissolved molecularly in DMF but formed aggregates in water even at pH 10. AFM images of the PS‐b‐PtBAs spin coated from THF and DMF onto mica showed aggregates. AFM images of the PS‐b‐PAAs spin coated from various mixtures of DMF and water at pH 10 showed flat disks and worm‐like images similar to those observed with linear PS‐b‐PAAs. Use of a PS‐b‐PAA and a PS‐b‐PMAA as templates for emulsion polymerization of styrene produced latexes 100–200 nm in diameter. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4623–4634, 2007