Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.     

Fabrication of an Electrochemical Sensor Based on Multiwalled Carbon Nanotubes for Almotriptan

In the present work, the electrochemical behavior of an antimigraine drug, almotriptan malate (ALM), on a multiwalled carbon nanotube (MWCNT) film modified glassy carbon electrode under cyclic voltammetry was described for the first time. A significant enhancement in the oxidation peak current of ALM was noticed at MWCNT‐GCE. This property was exploited to develop a simple, sensitive and time‐saving differential pulse voltammetric method for the determination of ALM in bulk and pharmaceutical samples. A linear relationship was observed between concentration and peak current with a correlation coefficient of 0.9915 in the range of 0.25–37.5 µM ALM.     

多壁纳米碳管固相萃取测定水中的有机氯农药

对于水样中的有机氯农药的净化方法主要是采用传统的液液分配的方法,缺点是溶剂使用量和前处理复杂。近年来固相萃取及固相微萃取等技术被应用到水样中的有机污染物的测定。如利用键合在硅胶上的非极性(C18,LC18等)或极性物质(LC-CN,LC-NH2)对水中有机物进行富集,用GDX或XAD自填的固相柱的报道也很多。纳米技术和纳米材料的发展为开发固相萃取材料带来新契机。纳米材料是指尺寸大小在从1～100m之间物质。与普通的块体材料相比,纳米材料具有较大的比表面,因而有可能具有较大吸附容量。纳米材料在环境有机污染物分离富集方面的应用研究才刚刚开始。本文主要就纳米碳管对水样中的有机氯农药进行研究,优化固相萃取条件。     

A New Indirect Electrochemical Method for Determination of Ozone in Water Using Multiwalled Carbon Nanotubes

A new electrochemical methodology has been developed for the detection of ozone using multiwalled carbon nanotubes (MWCNT). The method presented here is based on the reaction of ozone with indigo blue dye producing anthranilic acid (ATN). The electrochemical profile of ATN on an electrode of glassy carbon (GC) modified with MWCNT showed an oxidation peak potential at 750 mV vs. Ag/AgCl. An analytical method was developed using differential pulse voltammetry (DPV) to determine ATN in a range of 50–400 nmol L^?1, with a detection limit of 9.7 nmol L^?1. Ozonated water samples were successfully analyzed by GC/MWCNT electrode and the recovery procedure yielded values between of 96.5 and 102.3 %.     

The Heterogeneity of Multiwalled and Single‐Walled Carbon Nanotubes: Iron Oxide Impurities Can Catalyze the Electrochemical Oxidation of Glucose

It is well established that the heterogeneity of carbon nanotubes must be determined before the origin of the electrochemical performance can be attributed. Recently it has been diligently reported that for the case of multiwalled carbon nanotube modified electrodes, copper oxide impurities are responsible for the electrochemical activity facilitating a nonenzymatic sensing strategy towards glucose. We have explored both commercially available multiwalled and single‐walled carbon nanotubes for the sensing of glucose and find that iron oxide impurities remaining from the fabrication process are the electroactive sites facilitating the nonenzymatic detection of glucose. Given that the multiwalled carbon nanotubes in this work are purchased from the same leading supplier as that used recently, discrepancies in the fabrication process exist which clearly has implications in the commercialization of electrochemical sensors based on multiwalled carbon nanotubes.     

A Novel Amperometric Hydrogen Peroxide Biosensor Based on Horseradish Peroxidase Incorporated in Organically Modified Sol-Gel Glass Matrix/Graphite Paste with Multiwalled Carbon Nanotubes

We herein report an electrochemical hydrogen peroxide sensor based on horseradish peroxidase immobilized in organically modified sol-gel glass (ormosil) with mediator ferricyanide along with multiwalled carbon nanotubes (mwcnts). The ormosil material is converted to fine powder followed by incorporation within graphite paste electrode. The electrochemistry of redox materials encapsulated within ormosil has been studied. The requirement of mwcnts is examined. The ormosil prepared with optimum concentration of mwcnts shows better redox electrochemistry as compared to that made without mwcnts. The biosensor has been characterized by cyclic voltammetry and chroanoamperometry. The performance, stability, and reproducibility of a new peroxide biosensor are reported.     

Fabrication of Nickel Tetrasulfonated Phthalocyanine Functionalized Multiwalled Carbon Nanotubes on Activated Glassy Carbon Electrode for the Detection of Dopamine

The nickel tetrasulfonated phthalocyanine (NiTsPc) functionalized multiwalled carbon nanotube (MWCNT) nanocomposite was prepared by a simple sonochemical method. Here, NiTsPc served as a dispersing agent for MWCNT via π? π interaction between MWCNT and NiTsPc. The activated glassy carbon electrode (AGCE) modified with MWCNT‐NiTsPc composite exhibited a good electrocatalytic ability toward dopamine and displayed a good linear dependence in the concentration range of 20 nM–1.384 mM with a sensitivity of 0.17 µA µM^?1 cm^?2. The detection limit is 1 nM based on the signal‐to‐noise ratio of 3.     

Use of Mercury Film Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotubes in Electrochemical Analysis of DNA

Mercury film plated on a glassy carbon electrode modified with multiwalled carbon nanotubes (MF/MWNTs/GCE) was used for the analysis of single (ss) and double stranded (ds) DNA, as well as for Jurkat genomic DNAs methylated to different degrees. The results indicated that the DNA molecules adsorbed quite strongly on the MF/MWNTs/GCE surface allowing ex situ adsorption and produce well developed peaks (due to cytosine and adenine) by using adsorptive stripping (Ads, ex situ) square wave voltammetry (SWV). Also, SWV of Jurkat DNA mixtures methylated to different degrees revealed a linear decrease of the peak height with increasing methylation indicating an increase of structural rigidity.     

碳纳米管上分子印迹微反应器的构建及催化Diels-Alder反应研究

分子印迹聚合物（MIP）在合成与催化方面的应用受到越来越多的关注.传统的本体聚合生成的聚合物往往具有活性中心的利用率低、活性中心不均一、底物难以到达等问题.由于纳米材料具有很高的比表面积,将MIP制备成纳米级别的材料将有可能解决这些问题.本研究的目的是在纳米材料上构建分子印迹微反应器(MIM).通过多壁碳纳米管(MWNTs)上羟基的酯化反应在碳纳米管表面枝接双键,以蒽和马来酸的加成反应产物为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,通过微波辐射聚合在碳纳米管表面枝接一层厚度约为30 nm 的分子印迹催化剂. 该催化剂对蒽和马来酸的加成反应具有明显的催化作用,反应开始后的180min内,催化反应速率是不加催化剂反应速率的1.77倍. 催化动力学遵守Michaelis-Menten方程,催化反应最大速率（vmax）为0.713 umolL-1S-1,米氏常数（KM）为17735.24 umolL-1.     

Facile and Simultaneous Stripping Determination of Zinc,Cadmium and Lead on Disposable Multiwalled Carbon Nanotubes Modified Screen‐Printed Electrode

Screen‐printed electrodes (SPEs) are cheap and disposable. But their application for heavy metal detection is limited due to the low sensitivity and poor selectivity. Here we report the ultrasensitive and simultaneous determination of Zn²⁺, Cd²⁺ and Pb²⁺ on a multiwalled carbon nanotubes and Nafion composite modified SPE with in situ plated bismuth film (MWCNTs/NA/Bi/SPE). The linear curves range from 0.5–100 µg L^?1 for Zn²⁺ and 0.5–80 µg L^?1 for Cd²⁺. Uniquely, the linear curve for Pb²⁺ ranges from 0.05–100 µg L^?1 with a detection limit of 0.01 µg L^?1. The practical application was verified in real samples with satisfactory results.     

Platinum Nanoparticles Decorated Multiwalled Carbon Nanotubes – Ionic Liquid Composite Film Coated Glassy Carbon Electrodes for Sensitive Determination of Theophylline

Platinum nanoparticles (Pt_nano) decorated multiwalled carbon nanotubes (MWCNTs)–1‐octyl‐3‐methylimidazolium hexafluorophosphate ([omim][PF₆]) composite material (MWCNTs‐Pt_nano‐[omim][PF₆]) was fabricated and characterized for the first time. In the presence of [omim][PF₆], more Pt_nano could deposit on MWCNTs. The average diameter of the deposited Pt_nano was about 5 nm. The composite material film coated glassy carbon electrode (GCE) exhibited sensitive voltammetric response to theophylline (TP). Under the optimized conditions (i.e., preconcentration for 2 minutes on open circuit in 0.10 M pH 3.0 phosphate buffer), the anodic peak current of TP at about 1.1 V (vs. SCE) was linear to TP concentration over the range of 1.0×10^?8–1.0×10^?5 M. The detection limit was estimated to be 8.0×10^?9 M. The modified electrode was successfully applied to the determination of TP in medicine tablet and green tea. In addition, the voltammetric responses of hypoxanthine (HX), xanthine (Xan) and uric acid (UA) on the MWCNTs‐Pt_nano‐[omim][PF₆]/GCE were also discussed.     

A Nitrite Biosensor Based on the Direct Electron Transfer of Hemoglobin Immobilized on Carboxyl‐Functionalized Multiwalled Carbon Nanotubes/Polyimide Composite

The high electrically conductive carboxyl‐functionalized multiwalled carbon nanotubes (COOH‐MWCNTs) were used to combine with nonconducting polyimide (PI) to generate a PI/COOH‐MWCNTs membrane. PI served as a matrix to entrap COOH‐MWCNTs and hemoglobin (Hb). COOH‐MWCNTs can improve the conductivity of the composite. The direct electrochemistry measurement indicated that the PI/COOH‐MWCNTs composite enhanced the immobilization of Hb significantly. Besides, the Hb/PI/COOH‐MWCNTs/GCE biosensor possessed excellent electrocatalytic activity for the detection of nitrite. Therefore, PI is a good matrix for Hb immobilization and it has application in sensor construction. This work is promising in the development of sensitive biosensors based on PI/COOH‐MWCNTs composite film.     

Comparison of the Enrichment Efficiency of Multiwalled Carbon Nanotubes, C18 Silica, and Activated Carbon as the Adsorbents for the Solid Phase Extraction of Atrazine and Simazine in Water Samples

Multiwalled carbon nanotubes with exceptional merits as SPE adsorbents for enrichment of environmental pollutants have absorbed much attention. The goal of this paper was to make a comparison with it and regular adsorbents such as C18 silica and activated carbon in the extraction capacity of atrazine and simazine. The results indicated that multiwalled carbon nanotubes were very suitable for determination of atrazine and simazine because of an enrichment performance similar to that of C18 silica. In contrast, the spiked recovery of simazine was higher than that of atrazine using multiwalled carbon nanotubes as packing material for SPE. However, reverse results were obtained when the extraction was performed with packing of C18 silica. Moreover, as the extraction of simazine was concerned, multiwalled carbon nanotubes were much better than C18 silica. As for the enrichment of atrazine, C18 silica achieved greater extraction factor than multiwalled carbon nanotubes. Activated carbon did not give the expected extraction efficiency because of its large size and blank volume and less active sites for adsorption. All these experimental results indicated that multiwalled carbon nanotubes could be used as a valuable alternative adsorbent for SPE of atrazine and simazine in many real water samples.     

Understanding the Electrochemical Reactivity of Bamboo Multiwalled Carbon Nanotubes: the Presence of Oxygenated Species at Tube Ends May not Increase Electron Transfer Kinetics

The result of acid washing multiwalled carbon bamboo nanotubes is explored with voltammetry and X‐ray Photoelectron Spectroscopy; it is found that the presence of oxygenated species formed as a result at the ends of the nanotubes does not measurably change the heterogeneous charge transfer kinetics.     

Some Properties of Sodium Dodecyl Sulfate Functionalized Multiwalled Carbon Nanotubes Electrode and Its Application on Detection of Dopamine in the Presence of Ascorbic Acid

A sodium dodecyl sulfate (SDS) functionalized multiwalled carbon nanotubes (MWNTs) electrode (SDS/MWNTs) was successfully constructed in this study. The electrochemical property of the SDS/MWNTs electrode has been characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Nyquist plots suggest that the immersion time of SDS affects the resistances of the MWNTs electrodes. The thickness of adsorbed SDS on MWNTs surface is estimated to be 1.23 nm, which is close to the value of SDS monolayer. CV results demonstrate a 5‐fold enhanced response for dopamine (DA) at the SDS/MWNTs electrode compared to the bare MWNTs one. DPV results illustrate that DA can be selectively determined in the presence of high concentration ascorbic acid (AA) with a linear range from 20 μM to 0.20 mM and a sensitivity of 0.024 μA μM^?1 at the SDS/MWNTs electrode.     

Room Temperature Ionic Liquids (RTILs) and Multiwalled Carbon Nanotubes (MWCNTs) as Modifiers for Improvement of Carbon Paste Ion Selective Electrode Response; A Comparison Study with PVC Membrane

Room temperature ionic liquids (RTILs), 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmim]BF₄, and multiwalled carbon nanotubes (MWCNTs) were used for improvement of a praseodymium carbon paste ion selective sensor response. [bmim]BF₄ can be a better binder than mineral oils. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The characteristics of these electrodes as potentiometric sensors were evaluated and compared with PVC membrane sensor. The results indicate that potentiometric sensor constructed with ionic liquid shows an increase in performance in terms of Nernstian slope, selectivity, response time, and response stability compared to Pr(III) PVC membrane sensor.     

Grafting of Molecularly Imprinted Polymers on to Carboxyl-Modified Multiwalled Carbon Nanotubes for the Extraction of Rhodamine B from Dried Chili Powder

Molecularly imprinted polymers grafted on to the surface of carboxyl-modified multiwalled carbon nanotubes were developed using methacrylic acid as a functional monomer and trihydroxymethylpropyl trimethylacrylate as a crosslinker for application to rhodamine B determination. The synthesis, characteristics, and evaluation of the molecularly imprinted polymer are described. The apparent morphology of the polymers was characterized by scanning electron microscopy. To evaluate the binding ability of the molecularly imprinted polymers, equilibrium binding experiments were conducted and revealed the maximal binding capacity to be 561.54 µg g^?1. The introduction of nanomaterials into the polymer composite made important contributions to the affinity enhancement and recognition properties of the molecularly imprinted polymers. Moreover, the polymers were preliminarily applied as an adsorbent for separation and extraction of Rhodamine B from dried chili powder samples, based on solid phase extraction technology. The calibration curve was linear in the range of 0–7 µg mL^?1. For all tested samples, recoveries were reliable and in the range of 101.75–109.73%. The relative standard deviation ranged from 6.43–14.32%, which demonstrated that the polymer has potential for preconcentration of Rhodamine B from chili powder samples.     

Multiwalled Carbon Nanotubes Encased in Ruthenium Oxide Film as a Hybrid Material for Neurotransmitters Sensor

A hybrid film (MWCNTs‐RuO_x?nH₂O) which contains multiwalled carbon nanotubes (MWCNTs) along with the incorporation of ruthenium oxide (RuO_x?nH₂O) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of MWCNTs in the hybrid film enhances surface coverage concentration (Γ) of RuO_x?nH₂O to ≈2100%. The surface morphology of the hybrid film deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy. These two techniques reveal that the RuO_x?nH₂O incorporated on MWCNTs. Electrochemical quartz crystal microbalance study too reveals the incorporation of MWCNTs and RuO_x?nH₂O. The MWCNTs‐RuO_x?nH₂O hybrid film exhibits promising enhanced electrocatalytic activity towards the biochemical compounds such as epinephrine and norepinephrine. The electrocatalytic responses of these analytes at RuO_x?nH₂O, MWCNTs and MWCNTs‐RuO_x?nH₂O hybrid films have been measured using cyclic voltammetry. The obtained sensitivity values from electrocatalysis studies of analytes for MWCNTs‐RuO_x?nH₂O hybrid film are higher than the RuO_x?nH₂O and MWCNTs films. Finally, the flow injection analysis has been used for the amperometric studies of analytes at MWCNTs‐RuO_x?nH₂O hybrid film modified SPCEs.     

Novel Composite of Multiwalled Carbon Nanotubes and Gold Nanoparticles Stabilized by Chitosan and Hydrophilic Ionic Liquid for Direct Electron Transfer of Glucose Oxidase

A novel composite was fabricated through dispersing multiwalled carbon nanotubes (MWNTs) in gold nanoparticle (GPs) colloid stabilized by chitosan and ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium tetrafluoroborate, BMIMBF₄). Transmission electron microscopy (TEM) experiment showed that the GPs highly dispersed on the MWNTs probably due to the electrostatic interaction among GPs, MWNTs and the imidazolium cation of BMIMBF₄. X‐ray photoelectron spectroscopy (XPS) indicated that thus‐formed gold nanostructure was mediated by BMIMBF₄. When glucose oxidase (GOD) was immobilized on the composite (MWNTs‐GPs) its ultraviolet‐visible absorption spectrum kept almost unchanged. The immobilized GOD coated glassy carbon electrode (GOD/MWNTs‐GPs/GC) exhibited a pair of well‐defined peaks in 0.10 M pH 7.0 phosphate buffer solution (PBS), with a formal potential of ?0.463 V (vs. SCE). The electrochemical process involved two‐electron transfer. The electron transfer coefficient was ca.0.56 and the electron transfer rate constant was 9.36 s^?1. Furthermore, the immobilized GOD presented good catalytic activity to the oxidation of glucose in air‐saturated PBS. The K_m and I_m values were estimated to be 13.7 μM and 0.619 μA. The GOD/MWNTs‐GPs/GC electrode displayed good stability and reproducibility.     

Simultaneous Determination of Cyanazine, Chlorotoluron and Chlorbenzuron in Environmental Water Samples with SPE Multiwalled Carbon Nanotubes and LC

In this paper, a new method based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials for sensitive determination of cyanazine, chlorotoluron and chlorbenzuron in environmental water samples was demonstrated. Related parameters that may influence the enrichment efficiency of multiwalled carbon nanotubes such as the kind and volume of elute, sample flow rate, sample pH, and volume of the water samples were investigated. Under the optimum conditions, the detection limits of cyanazine, chlorbenzuron and chlorotoluron were 0.015, 0.012, 0.034 ng mL⁻¹, respectively. The experimental results indicated a good linearity (R ² > 0.9947) over the concentration range of 0.4–40 ng mL⁻¹ for cyanazine and chlorotoluron, and 0.8–80 ng mL⁻¹ for chlorbenzuron. The relative standard deviations of the three analytes were 3.54, 1.55 and 1.38%, respectively. The established method also was applied to the analysis of the real-world water samples and excellent achievements were obtained with average spiked recoveries from 87.8 to 110.1%. All the results indicated that this procedure could allow the simultaneous determination of these three compounds in environmental water samples at trace levels.