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Abstract: The hydroxide of meso-tetraphenylporphyrin derivatives functionalized carbon nanotubes (CNTs) was fabricated in our research to explore the interaction between porphyrin and explosive. It was turned out that in the formation of grid porphyrin film, carbon nanotubes as a cruciul base materials promoted the electron transfer rate. Most of important, the results also showed that the electrochemical response was enhanced through increasing the number of –OH substitution in porphyrin. Such information provides the platform for a practical strategy for rational design of the sensor of explosives. [Copyright &y& Elsevier]

Abstract: A novel nanocomposites film of conducting polymers including single-walled carbon nanotubes (SWCNTs), polypyrrole (PPy) and gold nanoparticles (AuNPs) modified electrode has been applied in voltammetric sensors to detect epinephrine (EP) sensitively when ascorbic acids (AA) and uric acids (UA) exist. The nanocomposites film of conducting polymers which show an excellent electrocatalystic activity for the oxidation of EP and UA was characterized by scanning electron microscopy (SEM) and electrochemical methods. The catalytic peak currents obtained from differential pulse voltammetry (DPV) increased linearly with increasing EP concentrations in the range of 4.0×10−9–1.0×10−7 M with a detection limit of 2.0×10−9 M (S/N=3), respectively. The results showed that the nanocomposites of conducting polymers can selectively determine EP in the coexistence of a large amount of UA and AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The PPy/AuNPs/SWCNTs nanocomposites film can also be satisfactorily used for detecting EP in epinephrine hydrochloride injection when contain AA and UA, which also shows good recovery for determination of EP in some biological fluids. [Copyright &y& Elsevier]

In this study, a carboxylated carbon nanotube-grafted Ag3PO4@AgIO4 (CNT-COO−/Ag3PO4@AgIO4) composite was synthesized through an in situ electrostatic deposition method. The synthesized composite was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and energy-dispersive X-ray spectroscopy (EDS). The electron transfer ability of the synthesized composite was studied using electrochemical impedance spectroscopy (EIS). The CNT-COO−/Ag3PO4@AgIO4 composite exhibited higher activity than CNT/Ag3PO4@AgIO4, Ag3PO4@AgIO4, and bare Ag3PO4. The material characterization and the detailed study of the various parameters thataffect the photocatalytic reaction revealed that the enhanced catalytic activity is related to the good interfacial interaction between CNT-COO and Ag3PO4. The energy band structure analysis is further considered as a reason for multi-electron reaction enhancement. The results and discussion in this study provide important information for the use of the functionalized CNT-COOH in the field of photocatalysis. Moreover, providinga new way to functionalize CNT viadifferent functional groups may lead to further development in the field of photocatalysis. This work could provide a new way to use natural sunlight to facilitate the practical application of photocatalysts toenvironmental issues. [ABSTRACT FROM AUTHOR]

Tyrosine is the precursor of some neurotransmitters such as thyroxine and dopamine. It has the effect of regulating emotions and stimulating the nervous system. Changes in tyrosine levels in the human body are associated with certain diseases. Therefore, it is very necessary to prepare a new type of tyrosine sensor. In this work, an enzyme-free electrochemical sensor based on MXene/CNTs/CuMOF composite was developed for the detection of tyrosine. Embedding carbon nanotubes (CNTs) into MXene effectively prevented the aggregation of MXene sheets. Further modification of MXene/CNTs materials with CuMOF octahedral particles with porous structure can improve the porosity and catalytic capability of the composites. Under the optimal detection conditions, the prepared sensor has good linearity in the detection of tyrosine within range 0.53 μM–232.46 μM with a limit of detection (LOD) of 0.19 μM. The stability and selectivity of the sensor is high, and can be used to detect tyrosine in human serum. [Display omitted] [ABSTRACT FROM AUTHOR]

A new kind of NiFe2O4-based magnetic covalent organic framework nanocomposites (NiFe2O4@COFs) was fabricated through facile synthesis approach under room temperature. The NiFe2O4@COFs exhibited higher adsorption capacity for brominated flame retardants than carbon nanotube material based on hydrophobic interactions, π-π stacking interaction, and van der Waals forces. In addition, the adsorption isotherm and the kinetic model were more suitable for Langmuir and pseudo-second-order model, respectively. NiFe2O4-based magnetic covalent organic framework nanocomposites combined with HPLC-UV (absorption wavelength: 214 nm) technology has excellent adsorption performance, which exhibited low detection limits (0.03–1.9 μg L−1), wide linear range (0.11–1000 μg L−1), good recoveries (91.5–102%) with a relative standard deviation of less than 2.9%. Finally, the prepared magnetic material was successfully used asadsorbents of magnetic solid-phase extraction and applied to the determination of five BFRs from the real water samples. [ABSTRACT FROM AUTHOR]

Considering the crucial roles of superoxide anion (O 2 − ) in pathological conditions, it is of great urgency to establish a reliable approach for real-time determination of O 2 − . Herein, a sensitive non-enzymatic sensor was constructed based on silver nanoparticles (AgNPs) and sodium dodecyl sulfate functionalized carbon nanotubes (SDS-MWCNTs) composites to measure the release of O 2 − from living cells. As an analytical and sensing platform, the AgNPs/SDS-MWCNTs modified glassy carbon electrode exhibited excellent electrochemical performance toward O 2 − with a determination limit as low as 0.0897 nM and wide linear range of 6 orders of magnitude, which was superior to other O 2 − electrochemical sensors. The excellent performance was attributed to the SDS-MWCNTs composites being used as effective load matrix for the deposition of AgNPs. Importantly, this novel non-enzymatic sensor could be applied to determination of O 2 − released from living cells, and the amount of flux of O 2 − increased accordingly with the improving of the concentration of AA, which has the possibility of application in clinical diagnostics to assess oxidative stress of living cells. [ABSTRACT FROM AUTHOR]

In this paper, a novel and facile electrochemical sensor for the simultaneous detection of adenine and guanine was fabricated based on 3,4,9,10-perylene tetracarboxylic acid noncovalently modified multiwalled carbon nanotubes. It exhibited good electrochemical responses toward the oxidation of adenine and guanine with a linear ranges covering 1.74 × 10 − 7 –2.09 × 10 − 5 M and 7.59 × 10 − 8 –2.09 × 10 − 5 M, and the corresponding detection limit of 5.81 × 10 − 8 M and 2.53 × 10 − 8 M (S/N = 3), respectively. Moreover, the fabricated sensor was employed for the exploration the possible electrochemical reaction mechanism of guanine supported by cyclic voltammetry experiments (CV). Eventually, the proposed sensor was applied in the determination of adenine and guanine contents in calf thymus DNA with satisfactory results, which has the great potential application in the sensitive monitoring of electroactive bio-molecules. [ABSTRACT FROM AUTHOR]

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is commonly identified as a biomarker of oxidative DNA damage. In this work, a novel and facile 8-OHdG sensor was developed based on the multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE). It exhibited good electrochemical responses toward the oxidation of 8-OHdG, and the linear ranges were 5.63×10 −8 −6.08×10 −6 M and 6.08×10 −6 −1.64×10 −5 M, with the detection limit of 1.88×10 −8 M (S/N=3). Moreover, the fabricated sensor was applied for the determination of 8-OHdG generated from damaged DNA and guanine, respectively, and the oxidation currents of 8-OHdG increased along with the damaged DNA and guanine within certain concentrations. These results could be used to evaluate the DNA damage, and provide useful information on diagnosing diseases caused by mutation and deficiency of the immunity system. [ABSTRACT FROM AUTHOR]

A sensitive and selective imprinted electrochemical sensor for the determination of aflatoxin B (AFB) was constructed on a glassy carbon electrode by stepwise modification of functional multiwalled carbon nanotubes (MCNTs), Au/Pt bimetallic nanoparticles (Au/PtNPs), and a thin imprinted film. The fabrication of a homogeneous porous poly o-phenylenediamine (POPD)-grafted Au/Pt bimetallic multiwalled carbon nanotubes nanocomposite film was conducted by controllable electrodepositing technology. The sensitivity of the sensor was improved greatly because of the nanocomposite functional layer; the proposed sensor exhibited excellent selectivity toward AFB owing to the porous molecular imprinted polymer (MIP) film. The surface morphologies of the modified electrodes were characterized using a scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. A linear relationship between the sensor response signal and the logarithm of AFB concentrations ranging from 1 × 10 to 1 × 10 mol L was obtained with a detection limit of 0.03 nmol L. It was applied to detect AFB in hogwash oil successfully. [ABSTRACT FROM AUTHOR]

We report on a new approach for the electrochemical detection of hydrogen peroxide (H2O2) based on Cytochrome C (Cyt c) immobilized ionic liquid (IL)-functionalized multi-walled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE). Functionalization of multi-walled carbon nanotube with amine-terminated ionic liquid materials was characterized using fourier transform infrared spectroscopy (FTIR), UV–vis spectra, and electrochemical impedance spectroscopy (EIS), and the results showed that the covalent modification of MWCNTs with ILs exhibited a high surface area for enzyme immobilization and provided a good microenvironment for Cyt c to retain its bioelectrocatalytic activity toward H2O2. Amperometry was used to evaluate the catalytic activity of the cyt c towards H2O2. The proposed biosensor exhibited a wide linear response range nearly 4 orders of magnitude of H2O2 (4.0×10−8 M–1.0×10−4 M) with a good linearity (0.9980) and a low detection limit of 1.3×10−8 M (based on S/N=3). Furthermore, the biosensor also displays some other excellent characteristics such as high selectivity, good reproducibility and long-term stability. Thus, the biosensor constructed in this study has great potential for detecting H2O2 in the complex biosystems. [ABSTRACT FROM AUTHOR]

Abstract: Development of a highly sensitive nanostructured electrochemical biosensor based on the integrated assembly of horseradish peroxidase (HRP) and single-walled carbon nanotubes (SWNTs) is described. In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the horseradish peroxidase (HRP) onto single-walled carbon nanotubes (SWNTs). We demonstrate that HRP–SWNTs conjugates can be assembled into amperometric biosensors which l-cysteine were assembled on a gold electrode through the covalent bond of S–Au and was used as a substrate for the immobilization of enzymes. Direct electron transfer of HRP is realized at SWNTs, and both anodic and cathodic currents of the redox reaction at the l-cysteine–HRP–SWNTs-modified gold film upon electrocatalysis are amplified. Meanwhile, experimental results reveal that HRP is stably immobilized onto the SWNTs and maintains inherent enzymatic activity toward H2O2. The modified electrode shows high sensitivity toward H2O2. A linear response to hydrogen peroxide measurement is obtained over the range from 1.0×10−12 to 1.0×10−11 M and an amperometric detection limit of 2.1×10−13 M due to its bioelectrocatalytic reduction based on direct electron transfer between gold electrode and the active site of the HRP. The biosensor displays excellent operational, storage stability and highly sensitive. The excellent performance validates the integrated assembly as an attractive sensing element for the development of a new hydrogen peroxide amperometric biosensor. [Copyright &y& Elsevier]

Abstract: The combination of biomolecules-functionalized multiwalled carbon nanotube (MWNTs) and ionic liquid (IL) yields nanostructured biointerfaces, formed a novel kind of structurally uniform and bioelectrocatalytic activity material. Rutin was chosen as a model biomolecules to investigate the composite system. The MWNTs–Rutin–IL composite film was characterized by different methods including thermogravimetric analysis (TGA), UV–vis spectra, electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscope (SECM). A pair of well-defined quasi reversible redox peaks of rutin was obtained at the MWNTs–Rutin–IL composite film modified glassy carbon electrode (GCE) by direct electron transfer between the rutin and the GCE electrode. Dramatically enhanced biocatalytic and electrocatalytic activity was exemplified at the MWNTs–Rutin–IL/GCE electrode by the oxidized of tryptophane. The oxidation peak currents of tryptophane in such modified electrode increased linearly with the concentrations of tryptophane in the range from 8×10−8 to 2×10−5 molL−1 with a detection limit of 3.0×10−8 molL−1. The unique composite material based on biomolecules-functionalized carbon nanotube and ionic liquid have wide potential applications in direct electrochemistry, biosensors, and biocatalysis. [Copyright &y& Elsevier]

Abstract: MWNTs-IL-Gel/GCE, a glassy carbon electrode modified with multiwalled carbon nanotubes (MWNTs) and ionic liquids (IL), was developed to serve as a sensor for simultaneous determination of Hydroquinone (HQ) and catechol (CC) in this paper. The modified GCE showed two well-defined redox waves for HQ and CC in both CV and DPV with a peak potential separation of ca. 0.1V, which was large enough for simultaneous detection. The results revealed that the oxidation of HQ and CC with the enhancement of the redox peak current and the decrease of the peak-to-peak separation exhibit excellent electrocatalytic behaviors. A high sensitivity of 1.8×10−7 M with detection limits of 6.7×10−8 M and 6.0×10−8 M (S/N=3) for HQ and CC were obtained. Moreover, the constants of apparent electron transfer rate of HQ and CC at MWNTs-IL-Gel/GCE were calculated as 7.402s−1 and 8.179s−1, respectively, and the adsorption quantity of HQ and CC was 1.408×10−6 molcm−2 with chronocoulometry. The developed sensor can be applied to determinate directly of HQ and CC in aqueous solution. [Copyright &y& Elsevier]

Abstract: In this paper, the electrochemical behaviors of rutin at the MWNTs-IL-Gel/glassy carbon electrode (GCE) were investigated. Good electrocatalysis behavior towards the oxidation of rutin with enhancement of the redox peak current and decrease of the peak-to-peak separation was demonstrated. The electrochemical parameters of rutin were calculated giving values of the charge-transfer coefficient (α) and the electrode reaction standard rate constant (k s) as 0.47 and 0.2s−1, respectively. In addition, the MWNTs-IL-Gel/GCE was characterized by different methods including electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), clay film thickness, and UV–vis spectra. The oxidation peak currents of rutin in such modified electrode increased linearly with the concentration of rutin in the range from 7.2×10−8 to 6.0×10−6 molL−1 with a detection limit of 2.0×10−8 molL−1. These results suggest that the proposed electrode can be used for sensitive, simple and rapid determination of rutin. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical behavior of hydroquinone (HQ) was studied by cyclic voltammetry at a glassy carbon electrode (GCE) modified by a gel containing multi-walled carbon nanotubes (MWNTs) and room temperature ionic liquid (RTIL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6). At the modified electrode, HQ showed a pair of quasi-reversible redox peaks. The cathodic peak current value (I pc) of HQ was 9.608×10−4 A, which is 43 times larger than the one at the GCE, and 11 times larger than that of I pc at the MWNTs/GCE. Furthermore, the capabilities of electron transfer on these three electrodes were also investigated by electrochemical impedance spectroscopy (EIS), and the similar conclusion as cyclic voltammetry has drawn. Besides, we also characterized the surface morphology of the prepared composite film using the scanning electronic microscopy (SEM). The MWNTs were pulled away from the tangle in RTIL. The solvent effect of RTIL may be the reason of higher adsorption amount. [Copyright &y& Elsevier]