Chitosan‐Functionalized Carbon Nanotubes as Support for the High Dispersion of PtRu Nanoparticles and their Electrocatalytic Oxidation of Methanol

Carbon nanotubes (CNTs) were non‐covalently functionalized with chitosan (Chit) and then employed as the support for PtRu nanoparticles. The functionalization was carried out at room temperature without the use of corrosive acids, thereby preserving the integrity and the electronic conductivity of the CNTs. Transmission electron microscopy reveals that PtRu nanoparticles were highly dispersed on the surface of Chit‐functionalized CNTs (CNT‐Chit) with small particle‐size. Cyclic voltammetry studies indicated that the PtRu nanoparticle/CNT‐Chit nanohybrids have a higher electrochemical surface area, electrocatalytic performance, and stability towards methanol oxidation compared to PtRu nanoparticles supported on the pristine CNTs.     

Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes

The confinement of air‐protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer‐precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface‐modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT‐confined iron nanoparticles coated with a polyisoprene air barrier. This approach constitutes a proof of concept for the development of smart materials for use in medicine or composites.     

A general route to prepare one- and three-dimensional carbon nanotube/metal nanoparticle composite nanostructures

Adsorption of polyethyleneimine (PEI)-metal ion complexes onto the surfaces of carbon nanotubes (CNTs) and subsequent reduction of the metal ion leads to the fabrication of one-dimensional CNT/metal nanoparticle (CNT/M NP) heterogeneous nanostructures. Alternating adsorption of PEI-metal ion complexes and CNTs on substrates results in the formation of multilayered CNT films. After exposing the films to NaBH4, three-dimensional CNT composite films embedded with metal nanoparticles (NPs) are obtained. UV-visible spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy are used to characterize the film assembly. The resulting (CNT/M NP)n films inherit the properties from both the metal NPs and CNTs that exhibit unique performance in surface-enhanced Raman scattering (SERS) and electrocatalytic activities to the reduction of O2; as a result, they are more attractive compared to (CNT/polyelectrolyte)n and (NP/polyelectrolyte)n films because of their multifunctionality.     

Antibacterial activity of pH‐sensitive genipin cross‐linked chitosan/poly(ethylene glycol)/silver nanocomposites

Novel nanocomposites consisting of genipin cross‐linked chitosan (GC), poly(ethylene glycol) (PEG), and silver nanoparticles were prepared for such biomedical applications as the wound‐healing materials. Various amounts of silver nanoparticles were dispersed in the GC/PEG hydrogel matrix without severe aggregation. The effects of composition and silver nanoparticles on the physico‐chemical properties of samples were evaluated by infrared analysis, contact angle measurements, and swelling tests. The GC/PEG/Ag nanocomposite showed a pH‐sensitive swelling behavior. The surface hydrophilicity of GC/PEG/Ag nanocomposites was improved with the increase of silver nanoparticle content. L929 cell attachment was improved in the presence of silver nanoparticles. The antimicrobial function was assessed for the GC/PEG/Ag nanocomposites containing the silver content over 100 ppm. The silver nanoparticles had the dual functions of reinforcing structural stability and enhancing antimicrobial activity of GC/PEG/Ag nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.     

Assembly of metal nanoparticle-carbon nanotube composite materials at the liquid/liquid interface

Carbon nanotubes (CNTs)-mediated self-assembly of metal (Au and Ag) nanoparticles at the liquid/liquid interface in the form of a stable nanocomposite film is reported. The metallic luster results from the electronic coupling of nanoparticles, suggesting the formation of closely packed nanoparticle thin films. The interfacial film could be transferred to mica substrates and carbon-coated transmission electron microscopy (TEM) grids. The transferred films were very stable for a prolonged time. The samples were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), TEM, and X-ray photoelectron spectroscopy (XPS). SEM and TEM results show that the films formed at the liquid/liquid interface are indeed composite materials consisting of CNTs and nanoparticles. XPS measurements further indicate the presence of the interaction between nanoparticles and CNTs.     

Low‐Temperature Growth of Carbon Nanotubes Catalyzed by Sodium‐Based Ingredients

Synthesis of low‐dimensional carbon nanomaterials such as carbon nanotubes (CNTs) is a key driver for achieving advances in energy storage, computing, and multifunctional composites, among other applications. Here, we report high‐yield thermal chemical vapor deposition (CVD) synthesis of CNTs catalyzed by reagent‐grade common sodium‐containing compounds, including NaCl, NaHCO₃, Na₂CO₃, and NaOH, found in table salt, baking soda, and detergents, respectively. Coupled with an oxidative dehydrogenation reaction to crack acetylene at reduced temperatures, Na‐based nanoparticles have been observed to catalyze CNT growth at temperatures below 400 °C. Ex situ and in situ transmission electron microscopy (TEM) reveal unique CNT morphologies and growth characteristics, including a vaporizing Na catalyst phenomenon that we leverage to create CNTs without residual catalyst particles for applications that require metal‐free CNTs. Na is shown to synthesize CNTs on numerous substrates, and as the first alkali group metal catalyst demonstrated for CNT growth, holds great promise for expanding the understanding of nanocarbon synthesis.     

A direct route toward assembly of nanoparticle-carbon nanotube composite materials

The preparation of nanocomposite materials from carbon nanotubes (CNTs) and metal or metal oxide nanoparticles has important implications to the development of advanced catalytic and sensory materials. This paper reports findings of an investigation of the preparation of nanoparticle-coated carbon nanotube composite materials. Our approach involves molecularly mediated assembly of monolayer-capped nanoparticles on multiwalled CNTs via a combination of hydrophobic and hydrogen-bonding interactions between the capping/mediating shell and the CNT surface. The advantage of this route is that it does not require tedious surface modification of CNTs. We have demonstrated its simplicity and effectiveness for assembling alkanethiolate-capped gold nanoparticles of 2-5 nm core sizes onto CNTs with controllable coverage and spatially isolated character. The loading and distribution of the nanoparticles on CNTs depend on the relative concentrations of gold nanoparticles, CNTs, and mediating or linking agents. The composite nanomaterials can be dispersed in organic solvent, and the capping/linking shells can be removed by thermal treatment to produce controllable nanocrystals on the CNT surfaces. The nanocomposite materials are characterized using transmission electron microscopy and Fourier transform infrared spectroscopy techniques. The results will be discussed in terms of developing advanced catalytic and sensory nanomaterials.     

Carbon nanotube film by filtration as cathode catalyst support for proton-exchange membrane fuel cell

A simple filtration method is developed to prepare a partially oriented superhydrophobic film of carbon nanotubes (CNTs) that have been catalyzed with uniform small Pt nanoparticles (2.8 nm) at high metal loading (30 wt %). A proton-exchange membrane fuel cell with the oriented CNT film as the cathode achieves higher single-cell performance than those with carbon black and a disordered CNT-film-based cathode probably because of the enhanced electrocatalytic activity of Pt/CNT and improved mass transport within the oriented film.     

Efficient anchorage of Pd nanoparticles on carbon nanotubes as a catalyst for hydrazine oxidation

A simple method is devised to deposit well-dispersed Pd nanoparticles on multi-walled carbon nanotubes (CNTs). Pd nanoparticles (1–3 nm) prepared in ethanol were transferred to toluene solution and modified by organic molecule benzyl mercaptan which acts as a cross linker between Pd nanoparticles and CNTs. The morphology and structure of the resulting Pd/CNT nanocomposite were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that Pd nanoparticles were highly dispersed and effectively anchored on CNTs. The excellent electrocatalytic activity of the Pd/CNT nanocomposite for the oxidation of hydrazine was demonstrated by cyclic voltammetry.     

Humic acid particle embedded super porous gum Arabic cryogel network for versatile use

Super porous gum Arabic (GA) cryogels were synthesized by crosslinking of natural GA with divinyl sulfone at cryogenic conditions, −20°C for potential biomedical applications. Humic acid (HA) nanoparticles were also prepared by using degradable and biocompatible crosslinkers such as trimethylolpropane triglycidyl ether, poly(ethylene glycol) diglycidyl ether, and trisodium trimetaphosphate in a single step and then entrapped within GA cryogel network as GA/HA particle cryogel. Furthermore, GA/HA cryogel was used as a template for Ag, Cu, and Fe nanoparticle preparation, and their antimicrobial properties were tested against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis strains. The minimum inhibition concentration values of Ag and Cu nanoparticle‐loaded GA/HA cryogel composites were determined as 10 mg mL⁻¹. Furthermore, the blood compatibility tests such as hemolysis and blood clotting indexes were determined for GA cryogels and found to be more compatible with 0.08 ± 0.01% hemolysis and 89.4 ± 6.1 blood clotting values, whereas the hemolysis of the Ag, Cu, and Fe nanoparticle‐loaded GA/HA Ag, Cu, and Fe metal nanoparticle cryogel composites decreased in the order of Fe > Cu > Ag nanoparticles.     

Nanoparticle‐enhanced bamboo‐like tubular nanofibers for active capture of particulate matter

We proposed a thought of active capture of particles by improving the interaction force between fibers and particles. Nanoparticle‐enhanced tubular nanofibers (Ag‐SPNTs) were prepared by template‐free cationic polymerization followed by surface modification. Ag‐SPNTs have coarse surface and bamboo‐like tubular structure with a diameter of approximately 80‐150 nm. Ag nanoparticles were embedded on the nanofibers surface, and the content of Ag nanoparticles in the nanofibers could be tuned by changing the concentration of [Ag(NH₃)₂]⁺ in the preparation process. f‐d curve measured by AFM showed that increasing the content of Ag nanoparticles in the nanofibers resulted in the enhanced interaction force between the nanofiber surface and particles. Particle matter capture test showed that the number of captured microscaled/naonoscaled particles on the fiber surface increased obviously for the nanoparticle‐enhanced tubular nanofibers (Ag‐SPNTs) compared to the nanofibers without nanoparticle (SPNTs), probably due to the increased interaction force and adhesion energy between fiber surface and particles. Filtration property test showed that the Ag‐SPNTs fiber films had a better filtration performance with a higher filter efficiency and QF value than that of SPNTs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

基于弱相互作用的石墨化CNT/PMMA复合材料的热电传输性能

从理论上计算了碳纳米管(CNT)与聚甲基丙烯酸甲酯(PMMA)的相互作用及浸润性, 并测试了CNT/PMMA复合材料的电学、热学和光学性能. 发现石墨化CNT/PMMA复合材料具有较好的导热和导电性能, 其渗流阈值在0.8%左右, 当CNT质量分数为3%时, 复合材料的导热系数提高193%. 这种电学及热学性能的提高一方面与石墨化CNTs的规整结构有关, 另一方面与石墨化CNT-PMMA体系的弱相互作用、CNT间的有效接触以及高效的CNT网络输运性能有密切关系. 研究结果表明, 通过调控CNT与聚合物基体的表面性质、相互作用及浸润性, 可以有效地构建优化的CNT输运网络, 获得性能优异的功能复合材料.     

Ag/CNT‐catalyzed hydroamination of activated alkynes with aromatic amines

As a nanoparticle support material, carbon nanotubes (CNTs) provide a certain potential activation of catalysis in heterogeneous catalytic organic reactions. Herein, an efficient Ag/CNT‐catalyzed synthesis of enamines via hydroamination of activated alkynes with aromatic amines has been described. This catalyst still retains catalytic activity after being recycled and reused three times. In addition, it represents a green and environmentally friendly process for preparation of enamines. Copyright © 2013 John Wiley & Sons, Ltd.     

碳纳米管的宏量制备及产业化

作为纳米材料的代表之一,碳纳米管因其独特的一维结构具备了优异的力学、电学、热学、光学和反应性能,使其在能源存储与转化、复合材料、多相催化、环境保护及生物医药等领域具有大量的应用潜力.本文总结了多种类型碳纳米管宏量制备的化学及工程原理,并对多壁碳纳米管、单壁碳纳米管、双壁碳纳米管、定向碳纳米管、超顺排碳纳米管、水平超长碳纳米管、掺杂碳纳米管、螺旋碳纳米管、碳纳米管结及碳纳米管/石墨烯杂化物的宏量制备方法进行了评述.同时,对碳纳米管产业化中新的工程问题,如工业标准、环境评估以及产业化进展进行了分析.目前,碳纳米管已经具有成千吨的产能,并广泛应用于锂离子电池电极、导电复合材料、汽车配件和体育用品等领域.尽管如此,高性能的碳纳米管的宏量制备及其配套产业化技术仍有待深入开发,产品需要进一步丰富、市场需要进一步拓展,以望形成大规模纳米产业,促进社会的可持续发展.     

In situ fabrication of silver nanoarrays in hyaluronan/PDDA layer-by-layer assembled structure

We present a simple in situ method to fabricate silver (Ag) nanoparticle arrays in a layer-by-layer (LBL) assembled hyaluronan (HA)/poly(dimethyldiallylammonium chloride) (PDDA) multilayer structure, in which the LBL multilayered film is constructed by electrostatic attraction between positively charged PDDA and negatively charged HA, followed by in situ synthesis of embedded Ag nanoparticle arrays in the LBL "nanoreactors," where the abundant negatively charged carboxyl groups of HA bind and further reduce Ag(+) ions under UV-irradiating. The arrays morphology is highly dependent on the number of bilayers, and the surface density of nanoparticles in the arrays can be simply tailored by the number of irradiation/drying cycles during fabrication. The embedded Ag nanoparticle arrays possess good stability for localized surface plasmon resonance (SPR) absorption spectrum-based biosensors and superior antimicrobial capability. These render great potentials for the films in both biosensing and antimicrobial applications.     

Titania-silver and alumina-silver composite nanoparticles: novel, versatile synthesis, reaction mechanism and potential antimicrobial application

Titania-silver (TiO(2)-Ag) and alumina-silver (Al(2)O(3)-Ag) composite nanoparticles were synthesised by a simple, reproducible, wet chemical method under ambient conditions. The surface of the oxides was modified with oleic acid, which acted as an intermediate between the oxide surface and the silver nanoparticles. The resulting composite nanoparticles were thoroughly characterised by XRD, TEM, XPS, FTIR and TGA to elucidate the mode of assembly of Ag nanoparticles on the oxide surfaces. Epoxy nanocomposites were formulated with TiO(2)-Ag and Al(2)O(3)-Ag to examine potential applications for the composite nanoparticles. Preliminary results from disc diffusion assays against Escherichia coli DH5α and Staphylococcus epidermidis NCIMB 12721 suggest that these TiO(2)-Ag and Al(2)O(3)-Ag composite nanoparticles have potential as antimicrobial materials.     

Templated synthesis of single-walled carbon nanotube and metal nanoparticle assemblies in solution

Carbon nanotube (CNT) and metal nanoparticle (NP) assemblies are conjugated nanosystems with potential applications in catalysis, sensing, and light harvesting. Due to poor solubility of CNTs, previously reported synthetic approaches are limited to large multi-walled CNTs, bundles of single-walled CNTs (SWNTs), or surface-bound CNTs. Here we report a solution-phase synthesis of SWNT-metal NP assemblies that is generally applicable to common metal elements. Key to the process is the poly(styrene-alt-maleic acid) surfactant which disperses SWNTs in aqueous solutions and acts as templates for the binding of metal ions and metal NPs.     

水溶液中碳纳米管的表面增强拉曼光谱研究

合成了碳纳米管和金纳米颗粒的复合物, 测量了水溶液相中复合物的表面增强拉曼光谱, 结果表明, 碳纳米管的巯基化修饰可以提高碳纳米管与金纳米颗粒复合的效率, 随着金纳米颗粒负载量的增加, 碳纳米管的拉曼信号逐渐增强. 加入己二胺分子可以减小金纳米颗粒之间的距离使表面增强效应更显著, 碳纳米管的拉曼光谱得到进一步的增强. 还可进一步在复合体系中加入对巯基苯胺和罗丹明B等小分子拉曼探针, 利用金纳米颗粒的表面增强效应, 这种多元复合体系有望作为多通道拉曼成像探针材料.     

Development and thermal behaviour of ternary PLA matrix composites

Biodegradable PLA composites were prepared using microcrystalline cellulose (MCC) and silver (Ag) nanoparticles. The main objective of the present study is to develop new biopolymer composites with good mechanical properties, thermal stability, maintaining the optical transparency and also providing antimicrobial properties through silver nanoparticle introduction. Composites were prepared with 1%wt of Ag nanoparticles and 5%wt of MCC using a twin-screw microextruder; film parameters were optimized in order to obtain a thickness range between 20 and 60 μm.PLA composites maintained optical transparency properties of the matrix, while MCC was able to reduce polymer permeability. Thermal analysis revealed that MCC increased PLA crystallinity and the mechanical properties of the composites demonstrated that tensile modulus was improved by microcrystalline cellulose.     

Novel in situ fabrication of chestnut-like carbon nanotube spheres from polypropylene and nickel formate

A novel in situ approach to mass fabrication of carbon nanotubes was reported. Composites of polypropylene (PP)/organomontmorillonite (OMMT)/nickel formate (NF) were prepared by mixing these components in a Brabender mixer at an elevated temperature. Chestnut-like carbon nanotube (CNT) spheres were in situ fabricated in high yields by heating the PP/OMMT/NF composites at 900 degrees C without adding any additional pre-synthesized nickel nanocatalysts. The products were studied by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and N2 adsorption-desorption measurements. The results showed that nickel nanoparticles were in situ produced, which catalyzed the formation of multiwalled carbon nanotubes (MWNTs) in an autoclave-like microreactor formed by OMMT. These in situ formed nickel nanoparticles were found to be more catalytically active than pre-synthesized nickel nanocatalysts, resulting in higher yields of CNTs. The obtained CNT spheres have a high surface area, which makes them a good catalyst support. Loading of metal nanoparticles was preliminarily tried, and Pt nanoparticles of ca. 2.65 nm in size were successfully deposited on CNTs. The applications of these nanocatalysts in chemical reactions are currently being studied in our laboratory.