Acid-modified Carbon Nanotubes Research Articles

Hyaluronic acid modified carbon nanotubes using for photothermal therapy by promoting apoptosis of nasopharyngeal carcinoma cells.

Background: The present work illustrates the role of multi-walled carbon nanotubes in photothermal therapy. Nasopharyngeal carcinoma (NPC) is a malignant tumor of the head and neck with significant ethnic and geographic differences, and conventional treatment options are no longer suitable to improve the prognosis and survival of patients. Photothermal therapy (PTT) has emerged as a new strategy for oncology treatment in recent years and is now used in the treatment of many common cancers. Multi-walled carbon nanotubes (MWCNT) have been used to advantage in several fields due to their excellent thermal conductivity. The aim of this paper is to investigate the promotion of apoptosis of nasopharyngeal cancer cells by multi-walled carbon nanotubes as an adjuvant nanomaterial for nasopharyngeal cancer photothermal therapy. Methods: Carboxylated multi-walled carbon nanotubes and prepared multi-walled carbon nanotube-hyaluronic acid (MWCNT-HA) composites were used for cell proliferation-related experiments such as CCK-8 assay, live-dead staining and flow cytometric analysis and inverted fluorescence microscopy to determine the expression level of apoptotic factors and confocal microscopy cell morphology analysis on nasopharyngeal carcinoma CNE-1 cells under near-infrared laser irradiation. The effects of multi-walled carbon nanotubes on the proliferation and apoptosis of tumor cells under NIR response were elucidated, and the mechanism of apoptosis was explored. Results: TEM and SEM demonstrated that MWCNT had good appearance morphology and the temperature rise curve indicated excellent photothermal stability. And MWCNT and MWCNT-HA could significantly inhibit the proliferation of tumor cells and change the normal morphology of cells under NIR laser irradiation. Cellular immunofluorescence analysis confirmed that MWCNT-HA significantly upregulated the expression level of apoptosis factor Caspase-3 and significantly downregulated the expression level of anti-apoptosis factor Bcl-2. Conclusion: In this study, MWCNT inhibited the proliferation of tumor cells and promoted apoptosis through the use of multi-walled carbon nanotubes as an adjuvant nanomaterial for photothermal therapy. In addition, multi-walled carbon nanotubes could inhibit the mitochondrial pathway of CNE-1 cells to cause cell death. These studies suggest that multi-walled carbon nanotubes can function as efficient photothermal conversion materials for tumor photothermal therapy.

Fabrication of highly dispersed carbon doped Cu-based oxides as superior selective catalytic oxidation of ammonia catalysts via employing citric acid-modified carbon nanotubes doping CuAl-LDHs

In this work, the CuAl-LDO/c-CNTs catalyst was fabricated via in situ oriented assembly of layered-double hydroxides (LDHs) and citric acid-modified carbon nanotubes (c-CNTs) followed by annealing treatment, and evaluated in the selective catalytic oxidation (SCO) of NH3 to N2. The CuAl-LDO/c-CNTs catalyst presented better catalytic performance (98% NH3 conversion with nearly 90% N2 selectivity at 513 K) than other catalysts, such as CuAlOx/CNTs, CuAlOx/c-CNTs and CuAl-LDO/CNTs. Multiple characterizations were utilized to analyze the difference of physicochemical properties among four catalysts. XRD, TEM and XPS analyses manifested that CuO and Cu2O nanoparticles dispersed well on the surface of the CuAl-LDO/c-CNTs catalyst. Compared with other catalysts, larger specific surface area and better dispersion of CuAl-LDO/c-CNTs catalyst were conducive to the exposure of more active sites, thus improving the redox capacity of the active site and NH3 adsorption capacity. In-situ DRIFTS results revealed that the internal selective catalytic reduction (iSCR) mechanism was found over CuAl-LDO/c-CNTs catalyst.

Mussel‐inspired double cross‐linked interpenetrating network with unique mechanical properties using di‐diol complexation

AbstractPolymer nanocomposites with exceptionally high mechanical properties owing to strong interfacial attraction have garnered tremendous interest in the research community. In general, tough and robust polymer nanocomposites are usually obtained via dispersing a nano‐flaky filler in the polymer matrix, although the strategy is only sometimes practically viable. To this end, in this work, a facile strategy has been adopted to achieve a strong and tough polymer nanocomposite. A novel mussel‐inspired full interpenetrating polymeric network (IPN) consisting of polyvinylalcohol and polydopamine was prepared. This technique helped integrate the advantages of dopamine chemistry with forming a full IPN using Borax as a common crosslinker. The infusion of 1 wt% acid‐modified carbon nanotubes (ACNT) in the IPN matrix helped greatly improve the current state‐of‐the‐art. The synergistic effect of nano‐reinforcement and formation of ester linkage through a substantial amount of di‐diol complexation dominated and accounted for the significant enhancement of mechanical properties. This is further supported by decreased intensity of free OH groups in the FTIR investigations, viscosity enhancement from rheological behavior, and temperature‐dependent dynamic mechanical property analysis. Such an IPN structure is a promising way to enhance mechanical properties.

Coaxial electro-spun stretchable nanofiber electrode at wide electrochemical voltage

Flexible supercapacitors have important implications in the field of smart clothing and wearables due to the ultra-fast charging/discharging rate, long cycle life, environmental friendliness and sustainability. However, a simple method is lacking to synthesize wearable electrodes with both wide electrochemical voltage and high capacitance performance in one step. A coaxial electrospinning method is applied herein for preparation of self-supported nanofiber electrode with polycaprolactone (PCL) as the core and Na-MnO2 as the sheath combined with impregnation of acid-modified carbon nanotubes (CNTs). Na-MnO2 prepared by hydrothermal method provides extra pseudo-capacitance and wide working window, polycaprolactone (PCL) and acid-modified CNTs further guarantee the stretchability and electrical conductivity. The stretchable symmetric supercapacitors based on the nanofiber electrodes with elongation at break of 62.39 % are further assembled with a capacitance of 0.655 mF/cm2 at 100 mV/s and excellent tensile properties at the wide working voltage of 0–1.2 V. The stretchability and wide voltage of the devices constructed herein only by one-step core-shell spinning demonstrate the great potential of the doped MnO2-based nanofiber for applications in wearable energy storage field.

Ultra-robust, stretchable electrodes based on superamphiphobic surface for personal exercise monitoring

The exploration of flexible electronic technology has been paid great attention recently, due to their promising applications such as health monitors and artificial electronic skins. To satisfy the requirement of practical applications, flexible and stretchable electrodes need to be further optimized in terms of mechanical robustness, sensing performance, and stability in extreme environments. Here, an ultra-robust and stretchable electrod is rationally designed and successfully fabricated via the synergistic combination of in situ growing silver nanoparticles (AgNPs)/acid-modified carbon nanotubes (ACNTs) conductive networks and superamphiphobic 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane modified carbon nanotubes-silica nanoparticles (FCNTs-SiO2). The obtained electrode shows a skin-like Young's modulus (2.3 MPa), high tensile strength (21.7 MPa), and good gas permeability. Owing to the conductive paths of ACNTs-bridged AgNPs, the strain sensor delivers a wide detection range of 155 %, a high gauge factor (denoted as GF) value up to 6.6 × 104 and a fast response time of 62 ms. The re-entrant structure constructed by spraying FCNTs-SiO2 along with chemcial composition endows the sensor with superamphiphobicity, which allows the sensor to fulfill its function under extreme environments (such as −60 ℃ to 60 ℃, corrosive liquids and non-polar liquids). The strain sensor can be used for monitoring high-frequency exercise and human health, indicating its potential application.

An In Situ Self‐Assembly Dual Conductive Shell Nanofiber Strain Sensor with Superior Sensitivity and Antibacterial Property

AbstractAt the moment, flexible, stretchable, and wearable strain sensors have extensive application prospect in medical healthcare for their abilities to instantly and accurately monitor human health and body movements, particularly suitable for patients with joint injury and movement disorder, which have attracted more and more attention. Hence, a multifunctional conductive nanofiber composite (M‐CNC) strain sensor with reliable antibacterial property is put forward. The thermoplastic polyurethane (TPU) nanofiber is served as the substrate, decorated by acid‐modified carbon nanotubes (ACNTs) and in situ self‐assembled silver nanoflowers (AgNFs), entitling the M‐CNC with double‐shell conductive networks. The M‐CNC (TPU/ACNT/AgNF) has a stable conductivity, which is up to 7.5 × 105 S m−1. Further, the double‐shell conductive networks have greatly enhanced the sensing performance of the M‐CNC strain sensor, possessing a useful gauge factor of 55 352, during the strain of 42% to 100%. Additionally, the outer AgNF shell structure is stable even after the cyclic test for 1000 times under the strain of 50%. The AgNF also endows the M‐CNC with great antibacterial property, indicating brilliant growth inhibition effects on Gram‐negative Pseudomonas aeruginosa and Gram‐positive Staphylococcus aureus.

Superhydrophobic and wearable TPU based nanofiber strain sensor with outstanding sensitivity for high-quality body motion monitoring

Nowadays, stretchable, flexible and wearable strain sensors are becoming more and more important for their abilities to monitor human health and body motions. However, it still exists some challenges to develop a new type of strain sensor with high sensitivity, the properties of anti-harsh environments and multidirectional monitoring. Here, we put forward a flexible, multi-functional, wearable and conductive nanofiber composite (WCNC) strain senor with handy preparation method, consisting of elastic thermoplastic polyurethane (TPU) with decorated acid modified carbon nanotubes (ACNTs), coupled silver nanowires (AgNWs) and solidified polydimethylsiloxane (PDMS). The sequential decorations of ACNTs, AgNWs and PDMS enhance the conductivity, superhydrophobicity, and strain sensing performance of the TPU-based nanofibrous membrane. The WCNC (TPU/ACNTs/ AgNWs/ PDMS) possesses a quite low resistance about 1.22 Ω/cm2 (conductivity is up to 3506.8 S/m), superior superhydrophobicity (contact angle is up to 153.04°) and self-cleaning property. Furthermore, the WCNC strain sensor possesses high sensitivity and large working strain (gauge factor is nearly 1.36 × 105 with the working strain ranging from 38% to 100%), which illustrates that the WCNC has a quite large work strain under extremely high GF, and has never been reported before. On account of its outstanding sensing performance, the WCNC can be used to monitor the different movements of human bodies and simultaneously monitor sensor signals in multiple vertical directions, achieving more accurate results.

Electrochemical sensing of adrenaline using surface modified carbon nanotube paste electrode

A new interesting insight into the construction of a voltammetric sensor for the detection of Adrenaline (AD) has been presented. Poly oxalic acid modified carbon nanotube paste electrode (POXMCNTPE) exhibited the boosted detecting ability towards the AD compared to the bare CNTPE (BCNTPE) as a sensing device. The detection of AD (pH 6.5) has been executed through the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) approaches. The surface morphological features, elemental analysis and electrochemical properties of the proposed electrode are revealed by Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDS), Electrochemical impedance spectroscopy (EIS), and CV technique. The number of electropolymerisation cycles were optimized. The few factors influencing the voltammetric signal of AD, such as the impact of pH and the effect of scan rate were examined. The detection limit (DL) 3.1 × 10−8 M and quantification limit (QL) 1.0 × 10−7 M was gained from the proposed method. The designed sensor displayed the superb selectivity, good reproducibility, repeatability and an excellent antifouling property. Hence, the proposed procedure was effectively implemented to detect the AD in the injection sample and as well as in the blood serum sample. The accomplished outcome from the proposed electrode reveals that it is a favourable candidate for electrochemical sensing of AD.

Dual conductive network enabled superhydrophobic and high performance strain sensors with outstanding electro-thermal performance and extremely high gauge factors

Conductive nanofiber composites (CNCs) are promising as wearable strain sensors (WSSs) due to their unique porous structure and thus good breathability, flexibility, skin affinity, and so forth. It still remains a great challenge to develop flexible and stretchable CNCs for high performance WSSs that possess a high sensitivity, large working strain and can also be applied in various harsh conditions such as extremely cold and corrosive environment. Here, we propose a facile strategy for preparation of superhydrophobic and multi-functional CNCs with a dual conductive network by sequential decoration of acid modified carbon nanotubes (ACNTs), Ag nanoparticles (AgNPs) and polydimethylsiloxane (PDMS) onto the elastic thermoplastic polyurethanes (TPU) nanofiber surface. The introduction of ACNTs, AgNPs and PDMS significantly improves the Young’s modulus and tensile strength while maintaining the superelasticity of the TPU nanofibrous membrane. The multi-functional CNCs possess high conductivity (up to 3031.5 S/m) and thus the excellent electro-thermal effect and deicing performance. The CNC based strain sensor possesses an extremely large gauge factor of 1.04 × 105 (with the strain ranging from 20% to 70%), which is the highest value ever reported for the CNC strain sensors. Thanks to the high sensitivity, the sensor can be used to monitor and distinguish various body motions including large and subtle human joint movement even in a corrosive condition. The superhydrophobic and multi-functional CNC has potential application prospects in water proof wearable electronics and heaters.

Flexible, superhydrophobic, and electrically conductive polymer nanofiber composite for multifunctional sensing applications

Sensor materials that can detect chemical vapors or mechanical deformation have wide applications in the field of healthcare, flexible electronics, environmental protection, etc. However, it is still challenging to prepare stretchable and multifunctional sensors that can be served as both chemical vapor and strain sensors. Here, a superhydrophobic and stretchable nanofiber composite is prepared by acid modified carbon nanotubes (ACNTs) decoration onto the polyurethane (PU)/ polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (SEBS) nanofibers, followed by the hydrolysis of methyltrichlorosilane (MTS) on the ACNT surface. The introduction of ACNTs and hydrolysate of MTS, namely the polysiloxane, significantly improves the mechanical properties of the blend nanofibrous membrane including the Young’s modulus, tensile strength and elongation at break. The superhydrophobicity can be maintained even under corrosive conditions. When served as the chemical vapor sensor, the nanofiber composite displays good selectivity, high sensitivity and low detection limit (1 ppm for the toluene vapor). Also, the nanofiber composite can be used as wearable strain sensors that can detect various body motions. The multifunctional nanofiber composite has potential applications in wearable electronic, electrical nose for gas leakage and smart textile.

Amino acid modified carbon nanotubes with optimal pore size for chiral separation

ABSTRACTPrecisely controlling pore size of porous materials is of great importance for chiral separation, but a great challenge in practical applications. In contrast, the molecular dynamics (MD) simulation can be quite a convenient way to determine the effect of the pore dimension on the chiral resolution performances and thus to define the optimal pore size. In this work, inner-wall functionalised carbon nanotubes (CNTs) were used as porous materials and D- and L-phenylalanine were selected as chiral probes. The enantioseparation behaviour was investigated via varying the pore diameter of CNTs, controlling the grafting amount of chiral selectors and tuning the spacer length. Results show that varying the pore size has a significant effect on the enantioselectivity. Additionally, the effect of the introduction of varying the grafting ratio and tuning the spacer length on the chiral separation performance was also examined in this work. It was found that varying the grafting ratio, especially the spacer length between substrates and selectors, could also be one of the most effective alternatives to improving enantioselectivity. Our findings can provide a guidance for the practical applications in the chiral separation.

A novel heteropolyacid-doped carbon nanotubes/Nafion nanocomposite membrane for high performance proton-exchange methanol fuel cell applications

A novel proton-exchange polymer composite membrane was synthesized using Nafion®, tetraethoxysilane-modified carbon nanotubes (CNTs) and phosphotungstic acid-modified carbon nanotubes with the aim of using direct methanol fuel cells (DMFCs). Physicochemical properties of the modified CNTs and fabricated composite membranes were investigated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, water uptake, thermogravimetric analysis, ion exchange capacity, proton conductivity and methanol permeability tests. It was demonstrated that chemical surface modification of CNTs and introduction of the phosphotungstic acid (PWA) groups effectively improved the performance of DMFC. It was found that the presence of PWA groups on the surface of CNTs led to the formation of strong electrostatic interactions between the PWA groups and clusters of sulfonic acid in Nafion® macromolecules. Hence, the incorporation of inorganic phosphotungstic super-acid-doped silicon oxide-covered carbon nanotubes (CNT@SiO2-PWA) into Nafion® matrices enhanced the proton conductivity of the prepared membranes. Moreover, the methanol permeability was reduced to 2.63 × 10−7 cm2 s−1 in comparison with the recast Nafion® membrane (2.25 × 10−6 cm2 s−1). Enhancing the proton conductivity and reducing the methanol permeability, the selectivity of the prepared nanocomposite membranes was enhanced to a greater value of 330,700 S s cm−3 as compared to the value of 38,222 S s cm−3 for recast Nafion®.

Thermodynamic Study of Methylene Blue Adsorption on Carbon Nanotubes Using Isothermal Titration Calorimetry: A Simple and Rigorous Approach

In this article, a thermodynamic study of the methylene blue (MB) adsorption on carbon nanotubes (CNT), a known model system, was carried out by using a simple and rigorous experimental approach based on adsorption and isothermal titration calorimetry (ITC) experiments. Considering the thermodynamics of the process, the classical approach using the van’t Hoff approximation provided endothermic values for ΔadsH0 while the ITC measurements revealed that the adsorption of MB on both unmodified and acid-modified CNTs is an exothermic process. The thermodynamic parameters for the systems were obtained using the infinite dilution regime and ITC data: ΔadsH0 = −9.13 ± 0.02 kJ mol–1, ΔadsG0 = −21.18 ± 0.61 kJ mol–1, and ΔadsS0 = 40.42 ± 0.61 J K–1 mol–1 for u-CNT and ΔadsH0 = −11.49 ± 0.34 kJ mol–1, ΔadsG0 = −27.88 ± 0.18 kJ mol–1, and ΔadsS0 = 54.97 ± 0.38 J K–1 mol–1 for f-CNT. The process is both enthalpically and entropically driven, having a more negative ΔadsG0 for the system based on a modified nanotube. W...

1,5-Dinitronaphthalene hydrogenation to 1,5-diaminonaphthalene over carbon nanotube supported non-noble metal catalysts under mild conditions

Carbon nanotubes (CNTs) were firstly thermal treated and then acid treated in HNO3 or mixture of HNO3 and H2SO4. The treated carbon nanotubes were used as support to load nickel to prepare non-noble metal hydrogenation catalysts. These catalysts were characterized and applied in 1,5-dinitronaphthalene hydrogenation. The characterization results indicate that acid modified carbon nanotubes not only possess a more hydrophilic surface by introducing a variety of oxygen-containing functional groups, but also improve the nickel dispersion, hydrogen uptake quantity and metallic surface area. The Ni/CNTs catalysts show good catalytic activity in 1,5-dinitronaphthalene hydrogenation under mild reaction conditions, and the Ni/CNTs-4 gives the best result of 100% conversion of 1,5-dinitronaphthalene and 92.04% selectivity to 1,5-diaminonaphthalene under 0.6MPa and 393K. The influences of reaction conditions and metal loading amount are discussed, and a possible reaction routes of 1,5-dinitronaphthalene hydrogenation is proposed. Such non-noble metal hydrogenation catalysts are expected to replace the present supported palladium or platinum noble catalysts in industry.

Synthesis and Characterization of Fe<sup>2+</sup>-CTS/CA-CNTs Composite and its Magnetic Properties

A novel biocompatible Fe2+-chitosan (CTS)/citric acid modified carbon nanotube (CA-CNTs) composite (Fe2+-CTS/CA-CNTs) has been successfully synthesized by covalent bonding and crosslinking chemistry, followed by the reduction. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectrum, X-ray diffraction (XRD), inductively coupled plasma (ICP), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) techniques. The results show that the CTS has been successfully grafted to the CA-CNTs carrier and Fe2+ ions are absorbed on the CTS by coordination bond mode. It was found that the Fe2+-CTS/CA-CNTs composite shows good magnetic properties with a low ratio of remanence to saturation magnetization and is in a superparamagnetic state at room temperature. It is believed that the Fe2+-CTS/CA-CNTs composite will be potential for application in MRI.

Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (P(O)(OH)2). Strong covalent CP bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (OH, CO, C(O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests.

Synthesis, Characterization, and Catalytic Performance of Highly Dispersed Supported Nickel Catalysts from Ni–Al Layered Double Hydroxides

Highly dispersed nickel nanoparticles were successfully prepared by reduction of Ni–Al layered double hydroxide precursor (NiAl-LDH) supported on nitric acid modified carbon nanotubes (HCNTs). The physicochemical properties of materials were investigated by powder X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed decomposition (TPDE), temperature programmed desorption (TPD), transmission electron microscopy (TEM), low-temperature nitrogen adsorption–desorption experiments, and X-ray photoelectron spectroscopy (XPS). The results revealed that in the synthesis process of NiAl-LDH and HCNTs composite, l-cysteine could improve the attachment of NiAl-LDH on the HCNTs as bridging linker and inhibit the growth of NiAl-LDH crystallites, thus leading to the formation of highly dispersed and uniform Ni nanoparticles with the small particle sizes. Compared with HCNTs-supported Ni catalyst prepared without the addition of l-cysteine, this highly dispersed Ni catalyst exhibited en...

Electrochemical and catalytic investigations of levodopa and folic acid by modified carbon nanotube paste electrode

A sensitive and selective electrochemical method for the determination of levodopa (LD) was developed using a ferrocenemonocarboxylic acid modified carbon nanotubes paste electrode (FMCNPE). The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of LD at pH 7.0 phosphate buffer solution. The diffusion coefficient (D = 1.44 × 10−6 cm2 s−1), and the kinetic parameters such as the electron transfer coefficient (α = 0.4) and catalytic rate constant (k = 1.8 × 10 3 M−1 s−1) of LD at the surface of FMCNPE were determined using electrochemical approaches. Differential pulse voltammetry (DPV) of LD at the modified electrode exhibited linear dynamic range with a detection limit (3σ) of 70 nM. DPV was used for simultaneous determination of LD and FA at the modified electrode. Finally, this modified electrode was also examined for the determination of LD and FA in urine samples.

Multi-wall carbon nanotubes as a sensor and ferrocene dicarboxylic acid as a mediator for voltammetric determination of glutathione in hemolysed erythrocyte

A sensitive and selective electrochemical method was developed for determination of glutathione (GSH) in hemolysed erythrocyte using a ferrocene dicarboxylic acid modified carbon nanotubes paste electrode (FDCCNTPE). Cyclic voltammetry (CV), double potential-step chronoamperometry and differential pulse voltammetric (DPV) were used to investigate the suitability of ferrocene dicarboxylic acid at the surface of a multi-wall carbon nanotubes paste electrode as a mediator for the electrocatalytic oxidation of glutathione in aqueous solutions with various pH. The results showed that FDCCNTPE had high electrocatalytic activity for the electrooxidation of glutathione. Under optimum conditions (pH 7.00), oxidation of GSH occurs at a potential about 230 mV less positive than that at the unmodified carbon nanotubes paste electrode. The catalytic reaction rate constant, kh was calculated (1.98 × 104 M−1 s−1) using chronoamperometry. The electrocatalytic oxidation peak current of GSH showed two linear dynamic ranges with a detection limit of 0.2 μmol L−1 GSH. The linear calibration ranges were obtained between 0.5–24 μmol L−1 and 24–122 μmol L−1 GSH using the DPV method. Finally, the proposed method was also examined as a selective, simple and precise electrochemical sensor for the determination of GSH in real samples such as hemolysed erythrocyte.

Sensitive and Selective Determination of Phenylhydrazine in the Presence of Hydrazine at a Ferrocene Monocarboxylic Acid Modified Carbon Nanotube Paste Electrode

In the present paper, the use of a carbon paste electrode modified by ferrocene monocarboxylic acid (FMC) and carbon nanotubes prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of phenylhydrazine (PHZ) and hydrazine (HZ) with a 300 mV separation of both peaks. Differential pulse voltammetric peak currents of PHZ and HZ increased linearly with their concentrations at the range of 0.8 µM to 700 µM and 16 µM to 800 µM and the detection limits (3σ) were determined to be 0.42 µM and 14 µM, respectively.