Mediatorless amperometric bienzyme glucose biosensor based on horseradish peroxidase and glucose oxidase cross-linked to multiwall carbon nanotubes

We report on a bienzyme-channeling sensor for sensing glucose without the aid of mediator. It was fabricated by cross-linking horseradish peroxidase (HRP) and glucose oxidase (GOx) on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWNTs). The bienzyme was cross-linked with the MWNTs by glutaraldehyde and bovine serum albumin. The MWNTs were employed to accelerate the electron transfer between immobilized HRP and electrode. Glucose was sensed by amperometric reduction of enzymatically generated H₂O₂ at an applied voltage of ?50 mV (vs. Ag/AgCl). Factors influencing the preparation and performance of the bienzyme electrode were investigated in detail. The biosensor exhibited a fast and linear response to glucose in the concentration range from 0.4 to 15 mM, with a detection limit of 0.4 mM. The sensor exhibited good selectivity and durability, with a long-term relative standard deviation of <5 %. Analysis of glucose-spiked human serum samples yielded recoveries between 96 and 101 %.

基于硫堇/碳纳米管修饰电极的新型过氧化氢电化学传感器

基于碳纳米管(CNTs)和硫堇(Th)的协同效应,将辣根过氧化物酶(HRP)通过戊二醛(GA)交联作用固定在硫堇(Th)/CNTs修饰电极上,构造了一种新型酶电极(HRP/GA-Th/CNTs/GC)。CNTs静电吸附正电荷的Th,而Th不仅可以促进电极和酶的氧化还原活性中心之间的电子传递,而且能使CNTs氨基(—NH2)功能化,从而利于HRP的固定。基于HRP/GA-Th/CNTs/GC电极的过氧化氢传感器具有较好的传感性能,且检出限低(0.3μmol.L-1)、响应时间短(5 s内)、抗干扰能力强。     

THERMAL DECOMPOSITION AND FLAMMABILITY OF ACRYLONITRILE-BUTADIENE-STYRENE/MULTI-WALLED CARBON NANOTUBES COMPOSITES

Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied.ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass.Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere,and both onset and maximum degradation temperature were lower than those of pure ABS.The destabilizat...     

单斜与锐钛矿双晶相TiO2/MWNTs复合材料的制备及其可见光光催化活性

以超强耐酸碱的表面活性剂-丁基封端脂肪醇聚氧乙烯醚作为晶型调节剂,利用钛酸丁酯和氢氧化钠的水热反应制备了单斜相与锐钛矿相双晶相TiO₂/多壁碳纳米管(简称MWNTs)复合材料,并考察了复合材料的可见光光催化活性。结果显示:MWNTs的加入可调控TiO₂的晶相组成,增强TiO₂的光催化活性,其中含5%MWNTs的样品具有较高的催化降解效率;随煅烧温度的升高,样品的光催化活性大幅提升。其机理归因于(1)促进单斜相和锐钛矿相双晶相结构的形成;(2)碳纳米管优良的导电作用及碳纳米管/TiO₂间的异质结效应;(3)高温下碳纳米管分解产生的碳元素掺杂作用。     

单斜与锐钛矿双晶相TiO2/MWNTs复合材料的制备及其可见光光催化活性

以超强耐酸碱的表面活性剂-丁基封端脂肪醇聚氧乙烯醚作为晶型调节剂,利用钛酸丁酯和氢氧化钠的水热反应制备了单斜相与锐钛矿相双晶相TiO2/多壁碳纳米管(简称MWNTs)复合材料,并考察了复合材料的可见光光催化活性。结果显示:MWNTs的加入可调控TiO2的晶相组成,增强TiO2的光催化活性,其中含5%MWNTs的样品具有较高的催化降解效率;随煅烧温度的升高,样品的光催化活性大幅提升。其机理归因于(1)促进单斜相和锐钛矿相双晶相结构的形成;(2)碳纳米管优良的导电作用及碳纳米管/TiO2间的异质结效应;(3)高温下碳纳米管分解产生的碳元素掺杂作用。     

Behavior of stabilized multiwalled carbon nanotubes in a FeCl3 coagulation system and the structure characteristics of the produced flocs

The understanding of the fate and the transport of carbon nanotubes (CNTs) in the water treatment process will provide important information for assessing the environmental risks of CNTs. To fill the knowledge gap, this study investigated the removability of multiwalled carbon nanotubes (MWNTs) stabilized by humic acid (HA) during the coagulation-flocculation-sedimentation (CFS) process. The structure characteristics of the produced flocs were systematically investigated using a variety of characterization approaches. The configuration resembling a root-soil system is shown in the images of scanning and transmission electron microscopy (SEM and TEM). With the incorporation of HA-MWNTs into the produced flocs, the X-ray diffraction (XRD) patterns of MWNTs completely disappeared. Fourier transform infrared spectra (FT-IR) and M?ssbauer spectra suggested that the intervention of HA-hinged MWNTs increased the degree of polymerization and the particle size of the produced hydrous ferric oxide (HFO). Finally, both the effective sequestration of MWNTs by CFS demonstrated here and the high sorption capacity of MWNTs for phenanthrene implied that MWNTs might be used as a potential coagulant aid in water processing for the enhanced removal of hydrophobic organic chemicals.     

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using polytetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2 is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.     

A novel H2O2 sensor based on the enzymatically induced deposition of polyaniline at a horseradish peroxide/aligned single-wall carbon nanotubes modified Au electrode

A novel H(2)O(2) sensor based on enzymatically induced deposition of electroactive polyaniline (PANI) at a horseradish peroxide (HRP)/aligned single-wall carbon nanotubes (SWCNTs) modified Au electrode is fabricated, and its electrochemical behaviors are investigated. Electrochemical impedance spectroscopy of the sensor confirmed the formation of PANI on SWCNTs through the HRP catalytic reaction. Cyclic voltammograms of PANI/HRP/SWCNTs modified Au electrodes showed a pair of well-defined redox peaks of PANI with reduction peak potentials of 0.211 and oxidation peak potentials of 0.293 V in 0.1 M HOAc-NaOAc (pH 4.3) solution. The oxidation peak current response of PANI is linearly related to H(2)O(2) concentration from 2.5 μM to 50.0 μM with a correlation coefficient of 0.9923 and a sensitivity of 200 μA mM(-1). The detection limit is determined to be 0.9 μM with a signal-to-noise ratio of 3. Thus, the synergistic performance of the enzyme, the highly efficient polymerization of PANI, and the templated deposition of SWCNTs provided an extensive platform for the design of novel electrochemical biosensors.     

Magnetic carbon nanotubes: synthesis by electrostatic self-assembly approach and application in biomanipulations

Magnetic multiwalled carbon nanotubes (MWNTs) were facilely prepared by the electrostatic self-assembly approach. Poly(2-diethylaminoethyl methacrylate) (PDEAEMA) was covalently grafted onto the surfaces of MWNTs by MWNT-initiated in situ atom transfer radical polymerization (ATRP) of 2-diethylaminoethyl methacrylate (DEAEMA). The PDEAEMA-grafted MWNTs were quaternized with methyl iodide (CH(3)I), resulting in cationic polyelectrolyte-grafted MWNTs (MWNT-PAmI). Magnetic iron oxide (Fe(3)O(4)) nanoparticles were loaded onto the MWNT surfaces by electrostatic self-assembling between MWNT-PAmI and Fe(3)O(4), affording magnetic nanotubes. The assembled capability of the nanoparticles can be adjusted to some extent by changing the feed ratio of Fe(3)O(4) to MWNT-PAmI. The obtained magnetic nanotubes were characterized with TEM, EDS, STEM, and element mapping analyses. TEM and EDS measurements confirmed the nanostructures and the components of the resulting nanoobjects. The magnetic nanotubes were assembled onto sheep red blood cells in a phosphate buffer solution, forming magnetic cells. The blood cells attached with or without magnetic nanotubes can be selectively manipulated in a magnetic field. These results promise a general and efficient strategy to magnetic nanotubes and the fascinating potential of such magnetic nanoobjects in applications of bionanoscience and technology.     

明胶固定辣根过氧化物酶制备H_2O_2传感器

用明胶将辣根过氧化物酶(HRP)固定于多壁碳纳米管(MWNT)和茜素红(AR)修饰的玻碳(GC)电极上,制成HRP生物传感器(HRP/AR/MWNT/GC),然后在3%戊二醛(GA)中进行交联改性,以克服明胶膜易溶胀的缺点,并提高膜的稳定性.同时详细探讨了该传感器对H2O2的响应性能,并优化了实验条件.结果表明,该传感器对H2O2的线性响应范围为5.0×10-6～1.0×10-3mol/L,线性相关系数为0.9932,检出限为1.0×10-7mol/L,且放于4℃环境30d后,峰电流值约为原来的72.1%.该传感器响应快速,灵敏度高,且具有良好的重现性、稳定性及较长的使用寿命,具有潜在的应用价值.     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H₂O₂ in the absence of a mediator. The linear range of detection towards H₂O₂ (applied potential: −0.2 V) was from 1.67 × 10⁻⁵ to 7.40 × 10⁻⁴ M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H₂O₂. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.     

Controlled modification of multi-walled carbon nanotubes with CuO,Cu2O and Cu nanoparticles

Multi-walled carbon nanotubes (MWNTs) have been successfully modified with CuO, Cu₂O and Cu nanoparticles via a simple method, and the calcination temperature, the amount of NH₃·H₂O and soaking time play critical roles in controlling the final products. The modified MWNTs have been characterized by X-ray diffraction, infrared spectrum, scanning electron and transmission electron microscopies. Optical absorption of the obtained products has also been investigated, and the quantum confinement effect was illustrated in the absorption spectra.     

氧化时间对多壁纳米碳管结构与性能的影响

氧化时间对多壁纳米碳管结构与性能的影响;碳纳米管; 氧化; 透射电镜; 核磁共振; 电阻     

Nanostructure PtRu/MWNTs as anode catalysts prepared in a vacuum for direct methanol oxidation

Platinum and ruthenium nanoparticles that are uniformly dispersed on multiwalled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using Pt(acac)2 and Ru(acac)3 as the metal precursors. The resulting nanocomposites were characterized by transmission electron microscopy and X-ray diffraction. The Pt, Pt45Ru55, and Ru nanoparticles had mean diameters of 3.0 +/- 0.6, 2.7 +/- 0.6, and 2.5 +/- 0.4 nm and the same mole number as their metal precursors at 500 degrees C. The electrocatalytic activity of the Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs exhibited a high level of catalytic activity for methanol oxidation as a result of the large surface area of the supporting carbon nanotubes and the wide dispersion of the Pt and Ru nanoparticles. Compared with the Pt/MWNTs, the onset potential for methanol oxidation of the PtRu/MWNTs was significantly lower, and the ratio of the forward anodic peak current to the reverse anodic peak current during methanol oxidation was somewhat higher. The Pt45Ru55/MWNTs displayed the best electrocatalytic activity of all of the carbon-nanotube-supported Pt and PtRu catalysts.     

The combined catalytic action of solid acids with nickel for the transformation of polypropylene into carbon nanotubes by pyrolysis

The effects of both organically modified montmorillonite (OMMT) and Ni₂O₃ on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni₂O₃ led to high‐yield formation of MWNTs. X‐ray powder diffraction (XRD) and GC–MS were used to investigate the mechanism of this combination for the high‐yield formation of MWNTs from PP. Brønsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride‐transfer reactions. The XRD measurements showed that Ni₂O₃ was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.     

Antibacterial effects of carbon nanotubes: size does matter!

We provide the first evidence that the size (diameter) of carbon nanotubes (CNTs) is a key factor governing their antibacterial effects and that the likely main CNT-cytotoxicity mechanism is cell membrane damage by direct contact with CNTs. Experiments with well-characterized single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) demonstrate that SWNTs are much more toxic to bacteria than MWNTs. Gene expression data show that in the presence of both MWNTs and SWNTs, Escherichia coli expresses high levels of stress-related gene products, with the quantity and magnitude of expression being much higher in the presence of SWNTs.     

原位缩聚法制备碳纳米管/尼龙11复合材料

用原位缩聚法制备了碳纳米管增强的尼龙11复合材料,用X射线衍射仪、红外(FTIR)、扫描电镜(SEM)、热重(TGA)、机械拉伸测试仪等对其结构、形貌、热性能及机械性能进行了表征测试.扫描电镜结果显示碳纳米管均一地分散在尼龙11/碳纳米管复合材料中.复合材料的拉伸模量比纯尼龙11有较大的提高.当复合材料中碳纳米管含量分别为1%,5%,10%时,材料的拉伸模量分别提高了34.5%,92.9%和113,7%.同时,复合材料的储能模量也有提高.热分析结果显示当复合材料中碳纳米管含量为1%时,其失重5%和10%的温度分别由纯尼龙11的404℃、424℃提高到414℃和437℃.示差扫描量热分析(DSC)显示复合材料的结晶温度随碳纳米管的加入而升高,而结晶度则降低.     

A hydrogen peroxide biosensor based on multiwalled carbon nanotubes-polyvinyl butyral film modified electrode

A novel approach to construct a amperometric biosensor for determination of H₂O₂ is described. Horseradish peroxidase (HRP) as a base enzyme was immobilized into the mixture of multiwalled carbon nanotubes (MWNTs) and polyvinyl butyral (PVB). Taking the classical hydroquinone as mediator, cyclic voltammetry and amperometric measurements were used to study and optimize the performance of the resulting H₂O₂ biosensor. The effect of the concentration of MWNTs, HRP, hydroquinone, solution pH, and the working potential of amperometry on the electrochemical biosensor was systematically studied. The results showed that the fabricated biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with wide linear range from 0.000832 to 0.6 mM, and low detection limit 0.000167 mM (S/N = 3) with fast response time less than 8 s. The apparent Michaelis–Menten constant was determined to be 0.049 mM. Additionally, the biosensor exhibited high sensitivity, rapid response and good long-term stability.     

Nanostructured films from phthalocyanine and carbon nanotubes: surface morphology and electrical characterization

We report on the investigation of the surface morphology and DC conductivity of nanostructured layer-by-layer (LbL) films from nickel tetrasulfonated phthalocyanine (NiTsPc) alternated with either multi-walled carbon nanotubes (MWNTs/NiTsPc) or multi-walled carbon nanotubes dispersed in chitosan (MWNTs+Ch/NiTsPc). We have explored the surface morphology of the films by using fractal concepts and dynamic scale laws. The MWNTs/NiTsPc LbL films were found to have a fractal dimension of ca. 2, indicating a quasi Euclidean surface. MWNTs+Ch/NiTsPc LbL films are described by the Lai-Das Sarma-Villain (LDV) model, which predicts the deposition of particles and their subsequent relaxation. An increase in the wetting contact angle of MWNTs+Ch/NiTsPc LbL films was observed, as compared with MWNTs/NiTsPc LbL films, which presented an increase in the fractal dimension of the first system. Room temperature conductivities were found be ca. 0.45 S/cm for MWNTs/NiTsPc and 1.35 S/cm for MWNTs+Ch/NiTsPc.