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There has been a growing interest in the field of transition metal dichalcogenide (TMD) materials and their potential applications in the field of electrochemical sensors. In the present work, molybdenum diselenide (MoSe2), as a typical representative of TMD, was prepared using a facile hydrothermal method and characterized in terms of its morphological and structural properties. Then, the obtained MoSe2 was dispersed in various solvents to investigate its electrocatalytic properties towards dopamine (DA), ascorbic acid (AA), and uric acid (UA). The electrochemical measurements revealed that deionized water is an effective solvent to disperse the MoSe2 and modify electrodes with the MoSe2 for electrochemical applications. Furthermore, the glassy carbon electrode (GCE) modified with the MoSe2, referred as GCE-MoSe2, was used as an electrochemical sensor to simultaneously detect the DA, AA, and UA. The GCE-MoSe2 exhibited wide linear detection with concentration ranges of 1–333 µM for DA, 50–3440 µM for AA, and 5–1146 µM for UA in phosphate buffer solution and low detection limits (LODs) of 0.57 µM, 13.7 µM, and 1.75 µM, respectively. The electrode further displayed good selectivity, reproducibility, and stability. This work provides valuable insights on constructing electrochemical sensing devices with high analytical performance using the important two-dimensional (2D) TMD materials. [ABSTRACT FROM AUTHOR]

A novel cobalt-doped two-dimensional molybdenum diselenide/polypyrrole hybrid-based carbon nanofiber (Co/MoSe2/PPy@CNF) was prepared using the hydrothermal method followed by electrospinning technique. The structural and morphological properties of the 2D-TMD@CNF-based hybrids were characterized through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and transmission electron microscopy (TEM). The Co-MoSe2/PPy@CNF exhibited large surface area, porous structure, and improved active sites due to the synergistic effect of the components. The electrochemical and electrocatalytic characteristics of the 2D-TMD@CNF-modified electrodes were also investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Co/MoSe2/PPy@CNF electrode was used as an electrochemical sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) and showed enhanced catalytic activity and sensitivity. Using DPV measurements, the Co/MoSe2/PPy@CNF demonstrated wide linear ranges of 30–3212 μM for AA, 1.2–536 μM for DA, and 10–1071 μM for UA with low detection limits of 6.32, 0.45, and 0.81 μM, respectively. The developed sensor with the Co/MoSe2/PPy@CNF-modified electrode was also applied to a human urine sample and gave recoveries ranging from 94.0 to 105.5% (n = 3) for AA, DA, and UA. Furthermore, the Co/MoSe2/PPy@CNF-based sensor exhibited good selectivity and reproducibility for the detection of AA, DA, and UA. [ABSTRACT FROM AUTHOR]

A new lactose biosensor was developed by preparing a suitable copolymer of polypyrrole and poly(3,4-ethylenedioxythiophene) synthesized using the electropolymerization method. Pyrrole and 3,4-ethylenedioxythiophene monomers were deposited in the presence of sodium dodecylbenzene sulphonic acid on a platinum disc electrode, which was used as the working electrode. The sensor is based on the serial reactions of [beta]-galactosidase and galactose oxidase immobilized on a copolymermodified platinum disc electrode. Successful synthesis of the enzyme-immobilized copolymer was confirmed by FTIR spectrometry, SEM, and electrochemical analysis. The response of the enzyme electrode to lactose was determined by cyclic voltammetry at + 0.40 V. The response time of the biosensor was found to be from 8 to 10 s, and the upper limit of the linear working portion was found to be at a lactose concentration of 2.30 mM with a detection limit of 1.4 x [10.sup.-5] M. The apparent Michaelis-Menten constant was found to be 0.65 mM of lactose. The effects of interferents were also investigated. Lactose concentrations determined by the biosensor were in good agreement with those measured by the reference methods. Our results show that the developed biosensor has a significant potential to the determination of lactose concentration in milk. POLYM. ENG. SCI., 58:839-848, 2018. [C] 2017 Society of Plastics Engineers, INTRODUCTION Lactose (or milk sugar), a significant component of milk and whey, is a disaccharide composed of d-glucose and d-galactose bonded by a [beta]-1,4 glycosidic linkage [1]. Lactose concentration in [...]

The development of sensitive and selective electrodes for electrochemical detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) is essential for early diagnosis and effective treatment. In this work, a nanocomposite of two-dimensional WSe2 nanosheets with carbon black (WSe2@C) was prepared by facile hydrothermal method and used to modify a glassy carbon electrode (GCE) to fabricate an electrochemical sensing platform for simultaneous determination of AA, DA and UA. The as-prepared nanocomposite was characterized in terms of structural and morphological analyses through X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical and electrocatalytic behaviors of the modified electrode (GCE-WSe2@C) were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The sensing performance of GCE-WSe2@C electrode was tested against AA, DA and UA, resulting in enhanced electrocatalytic properties compared to GCE-WSe2 and GCE-C electrodes. The GCE-WSe2@C electrode displayed wide linear ranges of 8.0 - $2456 \mu \text{M}$ for AA, 1.0 - 49.0 & 72.8 - $381.4 \mu \text{M}$ for DA and 1.0– 24.8 & 36.9– $185.2 \mu \text{M}$ for UA with low detection limits of 3.2, 0.18 and $0.42 \mu \text{M}$ , respectively. In addition, the developed electrode demonstrated high reproducibility and stability for electrochemical detection of AA, DA and UA. [ABSTRACT FROM AUTHOR]

An electrochemical-sensing platform for determination of dopamine (DA) was fabricated using MnO2–polyaniline (MnO2–PANI) composite. The MnO2–PANI composite was prepared through in situ radio-frequency plasma polymerization of aniline monomer over MnO2 under rotating conditions and followed by external iodine doping to boost conductivity of final I2–MnO2–PANI sample. The structural and morphological analyses of the composite were carried out using Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Differential pulse voltammetry was used as an effective electrochemical method for detection of dopamine. I2–MnO2–PANI composite-based sensor shows enhanced electrocatalytic activity and high selectivity towards DA in the presence of its major interferences, which are ascorbic acid and uric acid. The sensor showed a linear detection range from 12.4 to 185.2 μM with a detection limit of 2.4 μM. The sensor also exhibited long-term stability and reproducibility. Plasma process offers facile and fast production of electrode materials. [ABSTRACT FROM AUTHOR]

Defect and interface engineering have been shown as effective strategies towards sustainable hydrogen production, but detailed descriptions of the origin of performance enhancements is not established. Here, we synthesize a model heterostructure interface, CoSe2−MoSe2/PEDOT, to unravel its bifunctional capability. Low η10 of −0.20 V for HER and 1.53 V for OER verified the electrocatalytic performance of this catalyst. We systematically reveal intrinsic point defects and lattice dislocations in these heterostructures. Atomic scale electron microscopy studies disclose presence of VSe and Mo−Mo bond defects. Spectroscopic techniques are employed to show the altered electronic properties that promote surface oxidation due to the presence of defects. In contrast to MoSe2 or MoSe2/PEDOT, defect rich CoSe2−MoSe2/PEDOT showed accelerated reaction kinetics with much lower Tafel slopes. Essentially, generation of anion vacancies and metallic Mo−Mo bonds provide additional sites with improved adsorption properties of the reaction intermediates. This catalyst exhibits excellent electrocatalytic stability upon cycling for both half‐cell reactions. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is biologically important molecule, which plays a vital role in hormonal, renal, cardiovascular, and central nervous systems. Since abnormal level of this biological molecule leads to several diseases, its accurate and fast monitoring is of great importance for clinical diagnosis and treatment. The electrochemical approaches have become of significant interest to fulfill the requirements of DA detection. The electrode modifications play a crucial role in sensitive and selective detection of DA. This review presents the progress of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials modified electrodes for electrochemical determination of DA in the presence of interferents such as AA and UA. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotube (MWCNT) was modified through plasma polymerization of aniline by applying different radio frequency (radio frequency (RF): 13.56 MHz) powers. The modified MWCNTs were investigated in terms of morphology, chemical structure, and thermal behaviors, indicating the formation of composites based on the surface modification of MWCNT with polyaniline (PANI). These composites were then used in amperometric glucose biosensor, which was constructed by immobilizing glucose oxidase on premodified Pt electrode with PANI/MWCNT composites. The biosensor based on the composite obtained under RF power of 60 W exhibited the high sensitivity of 54.91 µA mM−1 cm−2 to glucose. [ABSTRACT FROM AUTHOR]