医用不锈钢的细胞膜仿生表面修饰

利用2-（甲基丙烯酰氧基）乙基-2-（三甲基氨基）乙基磷酸酯（MPC）与316L不锈钢表面上γ-氨基丙基三乙氧基硅烷（KH550）的Michael加成反应,将MPC化学接枝到不锈钢的表面．修饰表面的XPS结果证实了MPC的成功接枝,表明在不锈钢表面构建了仿细胞膜表面．体外血小板粘附实验显示,修饰表面具有明显阻抗血小板的粘附、聚集和激活性能,并具有良好的血液相容性．     

Covalent binding of single-walled carbon nanotubes to polyamide membranes for antimicrobial surface properties

We propose an innovative approach to impart nanomaterial-specific properties to the surface of thin-film composite membranes. Specifically, biocidal properties were obtained by covalently binding single-walled carbon nanotubes (SWNTs) to the membrane surface. The SWNTs were first modified by purification and ozonolysis to increase their sidewall functionalities, maximize cytotoxic properties, and achieve dispersion in aqueous solution. A tailored reaction protocol was developed to exploit the inherent moieties of hand-cast polyamide membrane surfaces and create covalent amide bonds with the functionalized SWNTs. The reaction is entirely aqueous-based and entails activation of the carboxylate groups of both the membrane and the nanomaterials to maximize reaction with ethylenediamine. The presence of SWNTs was verified after sonication of the membranes, confirming the strength of the bond between the SWNTs and the membrane surface. Characterization of the SWNT-functionalized surfaces demonstrated the attainment of membranes with novel properties that continued to exhibit high performance in water separation processes. The presence of surface-bound antimicrobial SWNTs was confirmed by experiments using E. coli cells that demonstrated an enhanced bacterial cytotoxicity for the SWNT-coated membranes. The SWNT membranes were observed to achieve up to 60% inactivation of bacteria attached to the membrane within 1 h of contact time. Our results suggest the potential of covalently bonded SWNTs to delay the onset of membrane biofouling during operation.     

Covalent coupling of polyacrylic acid coated magnetic-nanoparticles to multi-wall carbon nanotubes for manipulation targets

This research effort investigated the chemical heterojunction between magnetic nanoparticles coated with polyacrylic acid and multi-wall carbon nanotubes (MWCNTs). Here, magnetic nanoparticles were covalently attached to open-ended nanotubes in the presence of diclohexylcarbodiiimide. Initial evidence demonstrated that short functionalised multi-wall nanotubes can be continuously connected at their terminals ends to build-up relatively large nanostructures. It has also been shown that magnetic-carbon nanotubes (CNTs) systems exhibited defined arrangements due to the influence of magnetic fields. Indeed, linear arrays of CNTs interconnected through magnetic nanoparticles were prone to be manipulated in the presence of a magnetic device. A potential application of these kind of magnetic nanostructures was shown here by successfully manipulating agarose beads in a buffer solution. These results suggest that the use of continuously connected magnetic nanostructures with non-modified sidewall surfaces will find potential applications in the area of bio-sensing, force transduction and cancer screening-manipulation among many others.     

Covalent functionalization of carbon nanotubes through organometallic reduction and electrophilic attack

Organometallic reagents such as butyllithium are known to covalently functionalize the sidewalls of carbon nanotubes. The function grafted corresponds to the organic part of the alkali compound, while one negative charge is transferred to the nanotube for each function. Carbon nanotubes reduced by organolithium compounds were used here as nucleophilic reactive species through these transferred and delocalized charges. Various halogenated electrophiles in excess were reacted with them in anhydrous conditions. The grafting of the corresponding chemical function onto the carbon nanotubes through a Lewis metathetic exchange reaction was demonstrated by chemical, thermal, and spectroscopic analyses. This synthetic route applied successfully to both single-walled and multi-walled nanotubes and to a series of electrophiles. The extent of functionalization was found to depend on stoechiometries used, although a direct correlation could not be obtained.     

Crystallographic order in multi-walled carbon nanotubes synthesized in the presence of nitrogen

Multi-walled carbon nanotubes were synthesized by chemical vapor deposition from pure toluene and toluene/diazine mixtures using ferrocene as a catalyst precursor at 760 degrees C. As recently announced, characterization of the resulting nanotube films showed that, unlike pure carbon nanotubes, those grown in the presence of nitrogen have an extremely high degree of internal order, both in terms of the uniform chirality in the nanotube walls and of the crystallographic register between them. Here, the structure, defects, and morphology of the nanotubes were analyzed in depth using advanced electron microscopy techniques, and compared with existing models and observations. Nitrogen, which seems to be responsible for the dramatic structural order, was found to segregate preferentially within the core of the nanotubes.     

Interfacially reinforced methylphenylsilicone resin composites by chemically grafting multiwall carbon nanotubes onto carbon fibers

Both silane and multiwall carbon nanotubes (CNTs) were grafted successfully onto carbon fibers (CFs) to enhance the interfacial strength of CFs reinforced methylphenylsilicone resin (MPSR) composites. The microstructure, interfacial properties, impact toughness and heat resistance of CFs before and after modification were investigated. Experimental results revealed that CNTs were grafted uniformly onto CFs using 3-aminopropyltriethoxysilane (APS) as the bridging agent. The wettability and surface energy of the obtained hybrid fiber (CF-APS-CNT) were increased obviously in comparison with those of the untreated-CF. The CF-APS-CNT composites showed simultaneously remarkable enhancement in interlaminar shear strength (ILSS) and impact toughness. Moreover, the interfacial reinforcing and toughening mechanisms were also discussed. In addition, Thermogravimetric analysis and thermal oxygen aging experiments indicated a remarkable improvement in the thermal stability and heat oxidation resistance of composites by the introduction of APS and CNTs. We believe the facile and effective method may provide a novel interface design strategy for developing multifunctional fibers.     

A facile method to fabricate silica-coated carbon nanotubes and silica nanotubes from carbon nanotubes templates

Silica-coated multiwalled carbon nanotubes (MWCNTs) have been prepared by the sol–gel polymerization of tetraethoxysilane (TEOS) in the presence of the acid-oxidized MWCNTs at room temperature, followed by oxidizing the MWCNTs templates at high temperature in air to produce hollow silica nanotubes. The thickness and architectures of silica shell were well controlled by rationally adjusting the concentration of TEOS, and by adding cationic surfactant as a structure-directing agent. These results also give a clear answer to prove the fact that the structures of spherical silica particles can be fully “copied” to the coating shell and the wall of silica nanotubes when prepared by the same method as the synthesis of silica particles in the presence of templates.     

Theoretical prediction and experimental verification of pulling carbon nanotubes from carbon fiber prepared by chemical grafting method

This article reports on experiments for measuring pulling forces and displacements of a carbon nanotube (CNT) grafted on carbon fibers (CFs) and modeling for predicting the pulling force–displacement curves. In the experiments, the pulling force and displacement for different grafting configurations are measured. In the present analytical model, a power function relationship between a curvature radius and critical failure angle of the CNT was firstly established on the basis of the experimental data, and then the critical failure angle, maximum pulling forces and displacements were determined by using a free length, initial grafting length, initial grafting angle, the Hamaker constant and friction coefficient between the CNT and CF. By using the present model, pulling mechanical behaviors of CNTs with different grafting configurations are investigated and verified with results obtained from images taken in the experiment.     

静电纺PLA/姜黄素复合薄膜血液相容性研究

为了研究静电纺PLA/姜黄素复合薄膜血液相容性,将PLA和姜黄素溶解在三氯甲烷和丙酮体积比为2:1的混合溶剂中,采用静电纺丝技术分别制备纯PLA和姜黄素质量分数为3％的PLA/姜黄素复合薄膜,通过血小板聚集、动态凝血和溶血实验,评价静电纺PLA/姜黄素复合薄膜的血液相容性.实验表明:静电纺复合薄膜的血小板聚集抑制率为53.47％,远大于静电纺纯PLA薄膜的9.43％;复合薄膜的BCI始终大于纯PLA薄膜,且随着时间的延长BCI曲线下降缓慢;PLA/姜黄素复合薄膜的溶血率＜5％,对红细胞的破坏程度很小.故静电纺PLA/姜黄素复合薄膜具备良好的血液相容性,为制备血管支架材料或对现有血管支架材料加膜等方面有潜在的应用价值.     

Silane modification on mesoporous silica coated carbon nanotubes for improving compatibility and dispersity in epoxy matrices

A simple synthetic method for placing a mesoporous silica coating on multi-wall carbon nanotubes (CNTs@MS) was developed to improve the surface compatibility with regard to a polar epoxy matrix. In addition, the mesoporous silica shell with silanol groups on the CNTs provides a platform to attach silane molecules (e.g. 3-glycidoxypropyltrimethoxysilane, GPTMS) that enable the CNTs@MS to be incorporated into the epoxy matrix at a content of up to 20 wt.%. The viscosities of the CNTs@MS- and GPTMS-modified-CNTs@MS–epoxy composites are much lower than that of the CNTs–epoxy, and then the voids in the GPTMS-modified-CNTs@MS–epoxy composites are most significantly reduced. The effects of the CNTs@MS and GPTMS-modified CNTs@MS on the mechanical and thermal properties of the epoxy composite are investigated. The results show that the GPTMS-modified CNTs@MS improved the filler–epoxy matrix interaction, and has better compatibility in epoxy than the CNTs@MS. As the surface compatibility and interaction strength increase in the epoxy matrix, the enhancement in storage modulus, thermal conductivity and reduction in the coefficient of thermal expansion are in the following order: GPTMS-modified CNTs@MS > CNTs@MS ≫ CNTs.     

A novel approach of in situ grafting polyamide 6 to the surface of multi-walled carbon nanotubes

In this report, a novel approach was developed to graft polyamide 6 (PA6) onto the surface of multi-walled carbon nanotubes (MWNTs). MWNTs were covalently functionalized with copoly(styrene-maleic anhydride) (SMA) via free radical polymerization. SMA functionalized MWNTs (MWNTs-g-SMA) were then used as a macromolecular activator of anionic ring-opening polymerization of ε-caprolactam thus to graft PA6 onto the surface of MWNTs. Raman, FTIR spectroscopy and FETEM were used to identify the covalently grafting SMA and PA6 onto the surface of MWNTs. Additionally, the dispersibility of PA6 functionalized MWNTs (MWNTs-g-PA6) in formic acid and melted ε-caprolactam was also demonstrated.     

An attempt to prepare carbon nanotubes by carbonizing polyphosphazene nanotubes with high carbon content

Polyphosphazene nanotubes with about 20 nm in inner diameter and 100-200 nm in outer diameter were fabricated easily and then carbonized at 800 °C in a nitrogen atmosphere. Scanning electron microscopy and transmission electron microscope results showed that the bulk morphology of polyphosphazene nanotubes was retained after carbonization. The carbon content of the carbonized samples reached 93.28%. X-ray diffraction and Raman spectrum showed that the carbonized samples had low graphitization state. The present method can be used for a mass production of carbon nanotubes.     

Analytical and numerical modeling of higher order free vibration characteristics of single-walled carbon nanotubes

In this article, analytical and numerical investigations of small, higher, and asymptotic order vibration eigenmodes and natural eigenfrequencies of single-walled carbon nanotubes (CNT) are elaborated. The nonlocal elasticity theory is used and the numerical simulation is based on the differential quadrature method. Due to numerical instability, the common analytical forms of eigenmodes can be only used for the first 12 modes or so. New mathematical models for higher eigenmodes and associated eigenfrequencies of CNT are developed. The obtained eigenmodes are well conditioned and numerically stable and may be used as modal bases at any required frequency range.     

反应型磷系阻燃剂对多壁碳纳米管的接枝功能化研究

通过氧化、酰氯化以及酯化反应,将多壁碳纳米管与用于阻燃聚酯合成的磷系阻燃剂进行了接枝反应。对得到的接枝改性碳纳米管的结构、热稳定性以及分散性进行了表征分析。结果表明,浓硫酸/浓硝酸可以使碳纳米管表面形成一定数量的羧基,并且羧基的数量随着氧化时间的延长而增多。进一步的酯化反应,可以将磷系阻燃剂化学接枝于碳纳米管上,接枝改性后的碳纳米管在溶剂中的分散性得到明显提高,但热稳定性有所降低。     

Mesh-free simulation of single-walled carbon nanotubes using higher order Cauchy–Born rule

A mesh-free computational framework is developed to study the deformation behavior of single-walled carbon nanotubes (SWCNTs) by considering the effect of the second-order deformation gradient. The analysis is based on a hyper-elastic constitutive model derived from the higher order Cauchy–Born rule, in which the atomic-scale deformed lattice vectors are calculated with both the first- and second-order deformation gradients. Within the theoretical scheme of the higher order Cauchy–Born rule, the structural properties of SWCNTs and the constitutive response of the system are determined by minimizing the energy of the representative cell. The compression and torsion tests of SWCNTs are numerically simulated with the developed method. The numerical computations reveal that a less amount of mesh-free nodes can provide a good simulation for the homogeneous deformation stage, and the buckling pattern can be truly displayed with the application of the increasing amount of nodes.     

Covalent functionalization of single-walled carbon nanotubes with adenosine monophosphate: Towards the synthesis of SWCNT–Aptamer hybrids

Adenosine monophosphate (AMP) has been covalently linked to single-walled carbon nanotubes (SWCNTs) for the first time. SWCNT carboxylic acid moieties were activated through carbodiimide chemistry and acylation procedure. On the one hand, the phosphoramidate salts 12 and 13 were used to directly anchor AMP, and on the other hand a two-step procedure with grafting first the diaminopropane to SWCNTs followed by coupling of AMP. Thermogravimetric as well as elemental analysis, Fourier-transformed infrared and Raman spectroscopies give hints on the characterization of SWCNT–AMP.     

Investigation on the dispersion of carbon nanotubes in nitrile butadiene rubber: Role of polymer-to-filler grafting reaction

This contribution reports on the dispersion by simple melt blending of tiny amounts of carbon nanotubes (CNT) in nitrile butadiene rubbers (NBR). Acrylonitrile (ACN) units of NBR are known to generate free radicals upon heating and/or shearing. This paper highlights elements evidencing a possibility for NBR polymer chains to react by a free-radical mechanism and to graft onto CNT surface all along the process of mechanical blending of NBR with CNTs. More precisely and since the formation of the free-radicals takes place on the ACN units, the influence of the ACN relative content in NBR on the grafted CNT amount has been studied. It comes out that the polymer-grafting rate onto the CNT surface increases with the ACN content in NBR. Interestingly, the nanotubes proved more finely dispersed in NBR containing higher relative ACN content as evidenced by morphological observations as well as electrical measurements.     

An innovative method to improve the electrical conductivity of multi-walled carbon nanotubes filled polyamide 6/polystyrene blends

An innovative method has been successfully developed to improve the electrical conductivity of polyamide 6/polystyrene (PA6/PS) blends in this paper. PA6/PS blends containing multi-walled carbon nanotubes (MWCNTs) are prepared by the radical polymerization of styrene in the presence of ?-caprolactam (CL) and MWCNTs, followed by the in-situ anionic ring-opening polymerization of CL. In the resulted PA6/PS blends, MWCNTs are selectively located at the interface of PA6 and PS. Because the interface of 0.5 and 1.0 wt.% MWCNTs filled blends with PA6/PS weight ratio of 70/30 is continuous, a MWCNTs conductive pathway is formed in these two blends, which results in a decrease of volume resistivity by about 9 orders of magnitude.     

Osteoblast cell response to surface-modified carbon nanotubes

In order to investigate the interaction of cells with modified multi-walled carbon nanotubes (MWCNTs) for their potential biomedical applications, the MWCNTs were chemically modified with carboxylic acid groups (–COOH), polyvinyl alcohol (PVA) polymer and biomimetic apatite on their surfaces. Additionally, human osteoblast MG-63 cells were cultured in the presence of the surface-modified MWCNTs. The metabolic activities of osteoblastic cells, cell proliferation properties, as well as cell morphology were studied. The surface modification of MWCNTs with biomimetic apatite exhibited a significant increase in the cell viability of osteoblasts, up to 67.23%. In the proliferation phases, there were many more cells in the biomimetic apatite-modified MWCNT samples than in the MWCNTs–COOH. There were no obvious changes in cell morphology in osteoblastic MG-63 cells cultured in the presence of these chemically-modified MWCNTs. The surface modification of MWCNTs with apatite achieves an effective enhancement of their biocompatibility.