Cellulose–halloysite nanotube composite hydrogels for curcumin delivery

Halloysite nanotubes (HNTs) were added to cellulose NaOH/urea solution to prepare composite hydrogels using epichlorhydrine crosslinking at an elevated temperature. The shear viscosity, mechanical properties, microstructure, swelling properties, cytocompatibility, and drug delivery behavior of the cellulose/HNT composite hydrogels were investigated. The viscosity of the composite solution increases with the addition of HNT. The compressive mechanical properties of composite hydrogels are significantly improved compared with pure cellulose hydrogel. The compressive strength of the composite hydrogels with 66.7% HNTs is 128 kPa, while that of pure cellulose hydrogel is only 29.8 kPa in compressive strength. Rheological measurement suggests the resistance to deformation is improved for composite hydrogels. X-ray diffraction and Fourier transform infrared spectroscopy show that the crystal structure and chemical structure of HNT are not changed in the composite hydrogels. Hydrogen bonding interactions between HNT and cellulose exist in the composites. A porous structure of the composite hydrogels with pore size of 200–400 μm was found by scanning electron microscopy. The addition of HNT leads to decreased swelling ratios in NaCl solution and pure water for the composite hydrogels. Cytotoxicity assays show that the cellulose/HNT composite hydrogels have a good biocompatibility with MC3T3-E1 cells and MCF-7 cells. Curcumin is further loaded into the composite hydrogel via physical adsorption. The curcumin-loaded composite hydrogels show a strong inhibition effect on the cancer cells. All the results illustrate that the cellulose/HNT composite hydrogels have promising applications such as anticancer drug delivery systems and anti-inflammatory wound dressings.     

Thermal and electrical properties of poly(l-lactide)-graft-multiwalled carbon nanotube composites

The dispersion of the nanometer-sized carbon nanotubes in a polymer matrix leads to a marked improvement in the properties of the polymer. This approach can also be applied to biodegradable synthetic aliphatic polyesters such as poly(l-lactide) (PLLA), which has received a great deal of attention due to environmental concerns. In this study, PLLA was melt compounded with multiwalled carbon nanotubes (MWCNTs). A high degree of dispersion of the MWCNTs in the composites was obtained by grafting PLLA onto the MWCNTs (PLLA-g-MWCNTs). After oxidizing the MWCNTs by treating them with strong acids, they were reacted with l-lactide to produce the PLLA-g-MWCNTs. The morphology of the composite was observed with scanning electron microscopy. The mechanical properties of the PLLA/PLLA-g-MWCNT composite were higher than those of the PLLA/MWCNT composite. The thermal stability of the composites was studied using thermogravimetric analysis and their activation energy during thermal degradation was determined using the Kissinger and Flynn-Wall-Ozawa methods. The activation energy of PLLA/PLLA-g-MWCNT was higher than that of PLLA/MWCNT, which indicates that the composite made with the PLLA-g-MWCNTs was more thermally stable than the composite made with the MWCNTs.     

Low‐Temperature Synthesis of Crystalline Inorganic/Metallic Nanocrystal‐Halloysite Composite Nanotubes

We have demonstrated a facile approach for the low‐temperature synthesis of crystalline inorganic/metallic nanocrystal‐halloysite composite nanotubes by employing the bulk controlled synthesis of inorganic/metallic nanocrystals on halloysite nanotubes. The halloysite clay nanotubes can adsorb the target precursor and induce inorganic/metallic nanocrystals to grow in situ. The crystalline phase and morphology of the composite clay nanotubes is tunable. By simply tuning the acidity of the titania sol, the crystalline titania‐clay nanotubes with tunable crystalline phases of anatase, a mixture of anatase and rutile or rutile are achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate)‐halloysite composite nanotubes. Metallic nickel nanocrystal can also be grown on the surface of halloysite nanotubes at low temperature. The traditional thermal treatment for crystallite transformation is not required, thus intact contour of halloysite nanotubes and the crystallinity structure of halloysite nanotubes can be guaranteed. The combined properties from inorganic/metallic nanocrystal (high refractive index, high dielectric constant and catalytic ability) and the halloysite clay nanotubes are promising for applications such as photonic crystals, high‐k‐gate dielectrics, photocatalysis and purification.     

功能化碳纳米管的电磁性能研究及进展

碳纳米管是最近发展起来的一种结构独特,性能优异的新材料,已成为当今物理、化学、材料等领域共同关注的课题.而碳纳米管的功能化更是为我们开辟了一个广阔的研究领域.本文总结了近十多年来功能化碳纳米管的研究进展,并侧重对功能化碳管的合成方法及电磁特性以及应用进行了评述.     

Rational chemical strategies for carbon nanotube functionalization

Whereas the chemistry of fullerenes is well-established, the chemistry of single-walled carbon nanotubes (SWNTs) is a relatively unexplored field of research. Investigations into the bonding of moieties onto SWNTs are important because they provide fundamental structural insight into how nanoscale interactions occur. Hence, understanding SWNT chemistry becomes critical to rational, predictive manipulation of their properties. Among the strategies discussed include molecular metal complexation with SWNTs to control site-selective chemistry in these systems. In particular, work has been performed with Vaska's and Wilkinson's complexes to create functionalized adducts. Functionalization should offer a relatively simple means of tube solubilization and bundle exfoliation, and also allows for tubes to be utilized as recoverable catalyst supports. Solubilization of oxidized SWNTs has also been achieved through derivatization by using a functionalized organic crown ether. The resultant adduct yielded concentrations of dissolved nanotubes on the order of 1 g L(-1) in water and at elevated concentrations in a range of organic solvents, traditionally poor for SWNT manipulation. To further demonstrate chemical processability of SWNTs, we have subjected them to ozonolysis, followed by treatment with various independent reagents, to rationally generate a higher proportion of oxygenated functional groups on the nanotube surface. This protocol has been found to purify nanotubes. More importantly, the reaction sequence has been found to ozonize the sidewalls of these nanotubes. Finally, SWNTs have also been chemically modified with quantum dots and oxide nanocrystals. A composite heterostructure consisting of nanotubes joined to nanocrystals offers a unique opportunity to obtain desired physical, electronic, and chemical properties by adjusting synthetic conditions to tailor the size and structure of the individual sub-components, with implications for self-assembly.     

Composite Material that Comprised Metal–Organic Nanotubes and a Sponge as a High‐Performance Adsorbent for the Extraction of Pharmaceuticals and Personal Care Products from Environmental Water Samples

A composite material that comprised metal–organic nanotubes (MONTs) and a sponge, Cu?MONTs?sponge, was synthesized by using a rapid and convenient surfactant‐assisted dip‐coating method and used as a high‐performance adsorbent for the solid‐phase extraction of pharmaceuticals and personal care products (PPCP) from environmental water samples. By adjusting the surfactant concentration, a composite material that contained metal–organic nanotubes and a macroporous 3D porous sponge was constructed. This modified sponge achieved outstanding reproducibility as an adsorbent, with the adsorption of trace or ultratrace amounts of contaminants. Moreover, this composite material was conveniently recycled and its extraction efficiency only decreased by 6.3–12.1 % after 30 adsorption/desorption cycles. The resulting composite exhibited excellent adsorption capacity for PPCPs, which was attributed to its unique porous structure, natural hydrophobicity, and electrostatic interactions between the metal–organic nanotubes and analyte molecules. This Cu?MONTs?sponge material is an ideal adsorbent for the extraction of trace amounts of PPCPs from environmental water samples.     

钛基多孔HA/SiO2复合涂层的制备及性能研究

为了制得表面多孔且与基材结合强度高的羟基磷灰石(HA)涂层,实验中以正丁醇为分散介质,以SiO2粉末为添加剂,纯钛片为基材,电泳沉积制备羟基磷灰石/二氧化硅/壳聚糖/(HA/SiO2/CS)复合涂层,经后续热处理得到多孔HA/SiO2复合涂层,采用扫描电镜(SEM)、傅立叶红外光谱仪(FT-IR)、X射线衍射仪(XRD)、万能材料试验机对涂层的表面形貌、组成、结构和结合强度进行测试和表征,并通过模拟体液(SBF)浸泡法对复合涂层的生物活性进行评价.结果表明:当悬浮液中的HA/SiO2/CS质量比为1∶1∶1时,制得的HA/SiO2/CS涂层经700℃热处理后获得的HA/SiO2复合涂层孔洞分布均匀,大孔孔径在10～15μm,小孔孔径在1～5μm;涂层与基材的结合强度达到25.5 MPa;多孔HA/SiO2复合涂层在SBF中浸泡7 d后,涂层表面碳磷灰石化;说明实验中添加SiO2所制得的多孔HA/SiO2复合涂层与钛基材结合强度高,且具有良好的生物活性.     

Current trends in spinel based modified polymer composite materials for electromagnetic shielding

The present article deals with current trends in spinel based modified polymer composite materials for applications in the field of electromagnetic shielding. The interaction between the various spinel based materials and polymers is an emerging field of studies among various researchers. The thermal stability, electrical conductivity, the bonding between the metal ferrites and the polymer plays an important role in the interaction of electromagnetic radiation. These properties also effect the mechanism of the EM waves for the shielding applications. Considering these all properties, polyaniline appears to be an suitable polymer for electromagnetic shielding applications. Polyaniline composites not only reinforced the properties of spinel materials but also enhanced the dielectric properties of the composite material. When carbon based materials such as graphene, graphene oxide and CNT was added along with spinel material in polyaniline based composite, they accelerate the electrical properties and enhances the shielding applications. In this paper the various synthesis methods, fabrication methods of polyaniline, and the properties of polyaniline based composites have been discussed. In addition, the various salient features and futuristic challenges of polyaniline based composite materials for EMI shielding applications were attempted to make a well equipped material for radar absorption.     

Multiwalled carbon nanotubes with chemically grafted polyetherimides

Covalent attachment of a non-fluorinated polyetherimide onto the surface of carboxylic acid-functionalized multiwalled carbon nanotubes (MWNTs) has been achieved via grafting reactions. This confirms for the first time that the grafting reaction occurs at the nanotube surface when the carboxylic acid-functionalized MWNTs react with the polyetherimide with amine-terminated groups, through both amide and imide linkages formed at the interface between the carbon nanotubes and the polyetherimide. Additionally, an increase in the average molecular weight is detected in gel permeation chromatography when the polyetherimide is chemically attached onto the nanotubes. More interestingly, the chemical bonding at the interface provides much better interfacial adhesion and mechanical stress transfer, evidenced by a significant improvement in mechanical properties. As a result of the chemical attachment, the carbon nanotube-reinforced polyetherimide composite films have enhanced electrical conductivity, thermal deformation temperatures, and mechanical properties.     

纳米尺度电极材料的模板法合成及其电化学性能研究(英文)

本文利用氧化铝模板法合成了不同纳米尺寸的LiMn2 O4 纳米管 /纳米线及碳纳米管 .采用原子力显微镜 (AFM )及高分辨透射电镜 (TEM )表征了相关的模板及纳米管 .同时也报道了以纳米管阵列的LiMn2 O4 电极的循环伏安法的初步研究结果     

Carbon Nanotube and Gold‐Based Materials: A Symbiosis

Carbon nanotubes constitute a novel class of nanomaterials with potential applications in many areas. The attachment of metal nanoparticles to carbon nanotubes is new way to obtain novel hybrid materials with interesting properties for various applications such as catalysts and gas sensors as well as electronic and magnetic devices. Their unique properties such as excellent electronic properties, a good chemical stability, and a large surface area make carbon nanotubes very useful as a support for gold nanoparticles in many potential applications, ranging from advanced catalytic systems through very sensitive electrochemical sensors and biosensors to highly efficient fuel cells. Here we give an overview on the recent progress in this area by exploring the various synthesis approaches and types of assemblies, in which nanotubes can be decorated with gold nanoparticles and explore the diverse applications of the resulting composites.     

Chemically Modified Carbon Nanotubes for Use in Electroanalysis

The discovery of carbon nanotubes has had a profound impact on many areas of science and technology, not least that of electroanalysis. The properties and applications of carbon nanotubes themselves have been well reviewed in the literature and a number of reviews with an electrochemical emphasis have been published. However, the modification of carbon nanotubes has recently been the focus of much research, primarily to improve their solubility in various solvents. Yet modified carbon nanotube electrodes also allow the electrochemist to tailor the properties of the carbon nanotubes, or the electrode surface to impart desired properties such as enhanced sensing capabilities. In this review we attempt to comprehensively cover the different chemical and electrochemical modification strategies and research carried out using modified carbon nanotubes for electroanalytical and bioanalytical applications. Furthermore we also discuss the use of modified carbon nanotubes in electrocatalysis and biocatalysis from an analytical aspect, as well as seeking to dispel some of the myths surrounding the “electrocatalytic” properties of carbon nanotubes.     

Optical properties and photonic devices of doped carbon nanotubes

Chemical doping of carbon nanotubes provides a variety of opportunities for tailoring the physical properties of carbon nanotubes. In this review, we discussed the optical properties of doped carbon nanotubes and the related applications as nanoscale photonic devices. The fundamental optical properties of carbon nanotubes with various chemical doping have been summarized. Novel optoelectronic and photonic devices based on doped carbon nanotubes, such as optical nonlinear materials, optical limiting devices, photovoltaic devices, etc., have been discussed.     

Particle-stabilized surfactant-free medium internal phase emulsions as templates for porous nanocomposite materials: poly-Pickering-Foams

We report on the successful use of particle-stabilized Medium Internal Phase Emulsion (MIPE) templates for the synthesis of porous polymer foams. In this case, carbon nanotubes (CNTs) were used to stabilize the minority phase as the continuous phase, through adsorption at the interface. The addition of the CNTs not only provides processing advantages (no need for traditional non-ionic molecular surfactants) but also enhances the mechanical and electrical properties of the final polyFoams. This approach allows the manufacture of both closed- and open-celled porous polymer foams in a one-pot process with porosities up to 66%.     

Broadband radio-absorbing materials based on porous composites with carbon nanotubes

The reflection coefficient of an electromagnetic wave has been theoretically studied as a function of the thickness of a material and its dielectric properties. Samples based on spheroplastics with noncovalently modified carbon nanotubes have been obtained. The radio-engineering and electrophysical properties of these composites are discussed as well. The prospects for applying porous nanocomposites with carbon nanotubes in the fabrication of radio-absorbing materials are also shown.     

Electrochemical behavior and capacitance properties of carbon xerogel/multiwalled carbon nanotubes composites

The electrochemical behavior of carbon xerogel/multiwalled carbon nanotubes composite in a 6 M KOH solution has been investigated. Three different mixtures of teflonized carbons with varying nanotube content were prepared. The electrodes containing multiwalled carbon nanotubes were found to provide enhanced capacities compared with those prepared with only carbon xerogel. Cyclic voltammetry and charge–discharge experiments reveal the presence of a strong resistive component, which decreases as the amount of nanotubes increases. Electrochemical impedance spectroscopy results analyzed in terms of an adequate physicochemical model of the porous electrode, show that an increasing amount of nanotubes enhances both the effective solid-phase conductivity and the effective liquid-phase conductivity, linked to the porosity of the electrodes.     

Conductive macroporous composite chitosan-carbon nanotube scaffolds

Multiwalled carbon nanotubes (MWCNTs) were used as doping material for three-dimensional chitosan scaffolds to develop a highly conductive, porous, and biocompatible composite material. The porous and interconnected structures were formed by the process of thermally induced phase separation followed by freeze-drying applied to an aqueous solution of 1 wt % chitosan acetic acid. The porosity was characterized to be 97% by both mercury intrusion porosimetry measurements and SEM image analysis. When MWCNTs were used as a filler to introduce conductive pathways throughout the chitosan skeleton, the solubilizing hydrophobic and hydrophilic properties of chitosan established stable polymer/MWCNT solutions that yielded a homogeneous distribution of nanotubes throughout the final composite matrix. A percolation theory threshold of approximately 2.5 wt % MWCNTs was determined by measurement of the conductivity as a function of chitosan/MWCNT ratios. The powder resistivity of completely compressed scaffolds also was measured and was found to be similar for all MWCNT concentrations (0.7-0.15 Omega cm powder resistivity for MWCNTs of 0.8-5 wt %) and almost five times lower than the 20 k Omega cm value found for pure chitosan scaffolds.     

Enhanced electrochemical properties of polyethylene oxide-based composite solid polymer electrolytes with porous inorganic–organic hybrid polyphosphazene nanotubes as fillers

Solid composite polymer electrolytes consisting of polyethylene oxide (PEO), LiClO₄, and porous inorganic–organic hybrid poly (cyclotriphosphazene-co-4, 4′-sulfonyldiphenol) (PZS) nanotubes were prepared using the solvent casting method. Differential scanning calorimetry and scanning electron microscopy were used to determine the characteristics of the composite polymer electrolytes. The ionic conductivity, lithium ion transference number, and electrochemical stability window can be enhanced after the addition of PZS nanotubes. The electrochemical impedance showed that the conductivity was improved significantly. Maximum ionic conductivity values of 1.5 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.8 × 10⁻⁴ S cm⁻¹ at 80 °C were obtained with 10 wt.% content of PZS nanotubes, and the lithium ion transference number was 0.35. The good electrochemical properties of the solid-state composite polymer electrolytes suggested that the porous inorganic–organic hybrid polyphosphazene nanotubes had a promising use as fillers in SPEs and the PEO₁₀–LiClO₄–PZS nanotube solid composite polymer electrolyte might be used as a candidate material for lithium polymer batteries.     

General method for ultrathin free-standing films of nanofibrous composite materials

A simple and general method for the preparation of ultrathin, large-area, free-standing films of nanofibrous composite materials was developed. First, positively charged cadmium hydroxide nanostrands of 1.9 nm in diameter and micrometers in length were prepared by mixing dilute aqueous solutions of cadmium chloride and aminoethanol. Negatively charged dye molecules, proteins, nanoparticles, and water-soluble fullerene or carbon nanotubes were mixed with the nanostrands to give a well-dispersed solution of the corresponding nanofibrous composites. After filtration of the dispersions with a polycarbonate membrane filter, uniform films with a thickness of a few tens to hundreds of nanometers and a diameter of a few centimeters were obtained. The films were readily peeled off from the membrane filter by immersion in ethanol. The resultant free-standing films could be further transferred to other substrates, such as quartz plate, gold electrode, and porous alumina membrane, and were characterized by scanning and transmission electron microscopies. We provide herein various nanofibrous free-standing films with optical, biological, metallic, and magnetic properties.     

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of Au NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAuCl4 to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.