Bose Dinesh

Direct electrochemistry of myoglobin at reduced graphene oxide-multiwalled carbon nanotubes-platinum nanoparticles nanocomposite and biosensing towards hydrogen peroxide and nitrite

We described the preparation of a novel nanobiocomposite, reduced graphene oxide- multiwalled carbon nanotubes-platinum nanoparticles/myoglobin (RGO-MWCNT-Pt/Mb) for the direct electrochemistry of myoglobin and its application towards determination of hydrogen peroxide (H2O2) and nitrite (NO2(-)). RGO-MWCNT-Pt nanocomposite has been prepared by simple solution based approach and its structure was characterized. RGO-MWCNT-Pt/Mb nanobiocomposite was prepared and attained the direct electrochemistry of Mb with pair of well-defined redox peaks with the formal potential of -0.33 V and peak to peak separation of 22 mV. Amount of electroactive protein (Г) and heterogeneous electron transfer rate constant (ks) were calculated to be 1.04 × 10 (-9) mol cm(-2) and 9.47 s(-1). The sensor displayed lowest detection limit (LOD) of 6 pM which is the lowest LOD ever achieved for the detection of H2O2. Two linear ranges were observed for the detection of H2O2: (1) 10 pM-0.19 nM with sensitivity of 1.99 (± 0.058) µA pM(-1)cm(-2) and (2) 0.25 nM-2.24 µM with sensitivity of 0.037 (± 0.081) µA nM(-1)cm(-2). In addition, the biosensor offered good analytical parameters towards determination of NO2(-) with wide linear range of 1 µM to 12 mM and high sensitivity of 0.1651 (± 0.026) µA µM(-1) cm(-2). The sensor acquires good selectivity, repeatability, reproducibility and stability. The practical feasibility of the sensor has been addressed.

Direct electrochemistry of cytochrome c immobilized on a graphene oxide–carbon nanotube composite for picomolar detection of hydrogen peroxide

We describe the fabrication of an amperometric biosensor based on cytochrome c (Cyt c) immobilized graphene oxide–multiwalled carbon nanotube (GO–MWCNT) composite on a nano Au modified glassy carbon electrode for trace level detection of H2O2. Morphology and surface characterization of the nanocomposite reveal the successful formation of a highly conducting MWCNT network on the GO surface. Electrochemical impedance studies indicate a lower charge transfer resistance compared to the bare electrode. Cyclic voltammetry studies clearly demonstrate an enhanced direct electrochemistry of Cyt c with a high electron transfer rate constant (ks) value of 3.4 s−1. An amperometric H2O2 biosensor has been fabricated with an excellent current sensitivity of 0.533 μA pM−1 cm−2 and a very low detection limit of 27.7 pM. The fabricated sensor shows exceptional selectivity to H2O2 in the presence of a high concentration of some likely interferents. Moreover, the sensor exhibits high stability with appreciable repeatability and reproducibility.

An electrochemical synthesis strategy for composite based ZnO microspheres–Au nanoparticles on reduced graphene oxide for the sensitive detection of hydrazine in water samples

An electrochemical synthesis strategy has been developed to prepare a novel composite viz. reduced graphene oxide nanosheets/ZnO microspheres (∼0.6 μm)–Au nanoparticles (∼50 nm) modified glassy carbon electrode (GCE/RGO/ZnO–Au) for the trace level detection of hydrazine. Scanning Electron Microscopy (SEM) along with Energy Dispersive X-ray (EDX) analysis, confirming the presence of Au nanoparticles along with globular ZnO microspheres embedded over the entire surface of graphene nanosheets. The electrochemical detection of hydrazine is performed by cyclic voltammetry and chronoamperometry methods. Fascinatingly, the oxidation peak current of hydrazine at RGO/ZnO–Au modified GCE is 4.1 fold higher than that of RGO–Au modified GCE and 2.4 fold higher than ZnO/Au-modified GCE in addition to a favorable lower overpotential at 0.1 V. The chronoamperometric hydrazine sensor shows a very low detection limit of 18 nM with a high sensitivity of 5.54 μA μM−1 cm−2. The excellent analytical parameters of the RGO/ZnO–Au modified electrode over the various related modified electrodes suggest that the electrode can be advantageous for use in trace level detection of hydrazine in several industrial applications with low cost, ease of preparation, repeatability and long-term stability.

Electrochemical synthesis of Au–MnO2 on electrophoretically prepared graphene nanocomposite for high performance supercapacitor and biosensor applications

Herein, we report a facile electrochemical synthesis of an Au–MnO2 nanocomposite highly dispersed on an electrophoretically prepared graphene surface for the first time. Fascinatingly, we obtained a nanowires-like morphology for the MnO2 by using a simple in situ electrochemical deposition method. The as-synthesized Au–MnO2–graphene nanocomposite is characterized by various analytical and spectroscopic techniques viz. SEM, EDX, TEM, XRD, Raman spectroscopy and XPS. The as-prepared nanocomposite is employed in an electrochemical supercapacitor and for the sensitive detection of epinephrine. The supercapacitor performance is evaluated in 0.5 M NaOH by both cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) methods. The MnO2 : Au ratio during deposition plays a vital role to influence the capacitance properties. The highest specific capacitance of 575 F g−1 for 1 : 0.01 (MnO2 : Au) at a current density of 2.5 A g−1 has been obtained. The effect of current density, MnO2 : Au ratio, scan rate, mass loading and electrolyte concentration were also optimized and good cycle stability was demonstrated. The comparison of specific capacitance over MnO2–graphene and Au–MnO2–graphene nanocomposites suggests that the incorporation of Au nanoparticles on MnO2–graphene surfaces has a highly substantial effect for enhancement of capacitive behaviour. Furthermore, the epinephrine sensor performance of an Au–MnO2–graphene nanocomposite modified glassy carbon electrode is evaluated by CV and differential pulse voltammetry (DPV) techniques. Interestingly, the DPV sensor exhibited a very low detection limit of 24 nM and an excellent current sensitivity value of 35.6 μA μM−1 cm−2, surpassing several related modified electrodes and demonstrating several practical industrial applications.

Two-dimensional metal chalcogenides analogous NiSe2 nanosheets and its efficient electrocatalytic performance towards glucose sensing

Recently, 2D layered transition-metal dichalcogenide materials have received great consideration because of their unique electronic properties, large surface area and high electrocatalytic activity. In this connection, for the first time the similar nanostructured material of NiSe2 nanosheets (NiSe2-NS) has been synthesized by a facile hydrothermal method for electrocatalytic applications. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray analysis (EDX), X-ray diffraction spectrum (XRD) results confirmed the formation of NiSe2-NS with required stoichiometry and morphology. Electrochemical Impedance Spectroscopy (EIS) data indicate that electron transfer is facile at the NiSe2-NS modified glassy carbon electrode (GCE). It has been as an electrode modifier for glucose sensing applications. The electrochemical studies were performed for NiSe2-NS modified GCE using Cyclic Voltammetry (CV) and amperometric i-t techniques. The results are suggesting the effective response of NiSe2-NS/GCE with a very low limit of detection (LOD) and sensitivity of 23nM and 5.6μAμM-1cm-2 respectively. Moreover, the selectivity data exhibited excellent anti-interference property of NiSe2-NS/GCE towards glucose in the presence of possible interfering agents viz. Ascorbic acid, dopamine, glucose.

Entrapment of bimetallic CoFeSe 2 nanosphere on functionalized carbon nanofiber for selective and sensitive electrochemical detection of caffeic acid in wine samples

The ever-increasing requirement of an electrochemical sensor in various paramedical and industrial applications, the recent research is motivated to fabricate a new type of electrode material with unique electrochemical properties for quantitative detection of various target analytes. Recently, the metal diselenides have been interested in a broad range of electrochemical applications due to their interesting electrocatalytic performances. Despite the metal diselenides have been widely focused on hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), it is not much focused on electrochemical sensor. For the first time, the bimetallic cobalt-iron diselenide nanosphere entrapped functionalized carbon nanofiber (CoFeSe2/f-CNF) composite have been synthesized by using simple hydrothermal synthesis and used as an electrode material for efficient electrochemical detection of caffeic acid (CA). The functionalization of CNF and the formation of CoFeSe2/f-CNF nanocomposite have been successfully scrutinized by using Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. In addition, the electrochemical properties of CoFeSe2/f-CNF modified glassy carbon electrode (GCE) towards CA sensing were investigated by using cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. As the result of the electrochemical studies, the developed CoFeSe2/f-CNF/GCE sensor exhibits very low detection limit (0.002 μM) and better sensitivity (2.04 μA μM-1 cm-2) of CA. And also, CoFeSe2/f-CNF/GCE sensor shows the feasible detection of CA in red wine samples, it reveals the excellent practicability of CoFeSe2/f-CNF/GCE.

Hexagonal Co3O4 anchored reduced graphene oxide sheets for high-performance supercapacitors and non-enzymatic glucose sensing

Reduced graphene oxide (RGO) incorporated onto metal–organic framework (MOF)-derived Co3O4 hexagons is prepared via a hydrothermal route for supercapacitor and glucose sensor applications. Various analysis techniques demonstrate that the Co3O4 hexagons were uniformly spread over the thin graphene sheets to assist the electron accessibility of the electrode materials. Under optimized conditions, using 0.1 M KOH electrolyte at a current density of 4 A g−1, a specific capacitance value of 1300 F g−1 is obtained. The fabricated asymmetric supercapacitor cycled reversibly and exhibits high energy and power density values of 65.8 W h kg−1 and 2048 W kg−1, respectively, over the voltage range of −0.1 V to 0.4 V. The asymmetric supercapacitor shows 80.5% capacitance retention even after 5000 cycles at a current density of 4 A g−1, which indicates its high cycling stability in view of the fact that it is binder-free. Furthermore, the RGO–Co3O4 hexagon-modified electrode was optimized to realize the reliable amperometric determination of glucose concentration with a very low detection limit and excellent sensitivity value of 0.4 μM and 1.315 mA mM−1 cm−2, respectively. All of these remarkable performance indicators suggest that RGO–Co3O4 is a promising electrode material for next-generation energy storage devices and electrochemical sensors.