Deivasigamani Ranjith Kumar

Au–ZnO bullet-like heterodimer nanoparticles: synthesis and use for enhanced nonenzymatic electrochemical determination of glucose

In this work, the gold nanoseed mediated growth of bullet-like gold–zinc oxide (Au–ZnO) heterodimer nanoparticles has been reported. A formation pathway for the bullet-like morphology has been proposed. The heterojunction effect of the Au–ZnO nanoparticles was studied using UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and electrochemical impedance spectroscopy (EIS). The bullet-like Au–ZnO heterodimer nanoparticles were effectively employed as a sensor for the nonenzymatic determination of glucose (GLU) in a Au–ZnO/MWCNTs/GC modified electrode. This showed good sensitivity and a wide linear range of 19–291 μM with a sensitivity of 0.0447 μA μM−1 and a limit of detection of 0.19 μM. The resulting sensor displayed excellent repeatability and long-term stability.

Electrostatic fabrication of oleylamine capped nickel oxide nanoparticles anchored multiwall carbon nanotube nanocomposite: A robust electrochemical determination of riboflavin at nanomolar levels

A simple and strong electrostatic adsorption of oleylamine (OLA) capped nickel oxide (NiO) nanoparticles (oleylamine–amine group) onto the acid functionalized multiwalled carbon nanotubes (MWCNTs) (–COOH group) through coulombic interaction, leads to the construction of OLA–NiO/MWCNTs nanocomposite. The optimum loading of OLA–NiO nanoparticles on to the acid functionalized MWCNTs is investigated by Fourier transform infrared spectroscopy. Moreover, the optimum amount of loading and stability of the modified electrodes were studied by using linear sweep voltammetry and conductivity of optimum loadings are also studied by electrochemical impedance spectroscopy. OLA–NiO/MWCNTs nanocomposite was fabricated on glassy carbon electrode for the electrochemical determination of riboflavin (RF) at nanomolar levels. The results show a dynamic linear range of 0.009–55.9 μM with excellent sensitivity of 0.489 μA μM−1 and the limit of detection was found to be 1 nM (S/N = 3). The developed OLA–NiO/MWCNTs composite decorated GC exhibited good sensitivity, stability, and reproducibility for the determination of RF in differential pulse voltammetry. The OLA–NiO/MWCNTs/GC modified electrode was applied for the determination of RF in pharmaceutical formulation tablet and syrup samples.

Potentiodynamic formation of diaminobenzene films on an electrochemically reduced graphene oxide surface: Determination of nitrite in water samples

An electrode comprised of a polydiaminobenzene (p-DAB) film formed on electrochemically reduced graphene oxide (ERGO) on a glassy carbon (GC) (p-DAB@ERGO/GC) was fabricated using a potentiodynamic method for the sensitive and selective determination of nitrite in the presence of a common interference. The p-DAB@ERGO/GC film-modified electrode surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The film fabrication was initiated via the NH2 groups of DAB, which was confirmed by XPS from the peaks corresponding to NH (396.7eV), NH (399.4eV), NN (400.2eV), and N+H (402.2eV). The Raman spectra revealed the characteristic D and G bands at 1348 and 1595cm-1, respectively, which confirmed the fabrication of GO on the GC electrode, and the ratio of the D and G bands was increased after the electrochemical reduction of GO. The surface coverage of the modified electrode was 8.16×10-11molcm-2. The p-DAB@ERGO/GC film-modified electrode was used successfully for the determination of nitrite ions. The p-DAB@ERGO/GC film-modified electrode exhibited superior activity for the determination of nitrite compared to the bare GC and p-DAB@GC electrodes. The amperometric current increased linearly with increasing nitrite concentration from 7.0×10-6 to 2.0×10-2M. The detection limit was 30nM (S/N=3). In addition, the modified electrode was used successfully to determine the nitrite ion concentration in the presence of a 100-fold excess of common interferents. The practical application of the modified electrode was demonstrated by determining the nitrite ion concentration in water samples.

Flower-like Bi2S3 nanostructures grown on nitrogen-doped reduced graphene oxide for electrochemical determination of hydrogen peroxide

This paper reports a facile solvothermal method for the synthesis of Bi2S3 flower-like nanostructures grown in situ on a nitrogen-doped reduced graphene oxide (Bi2S3@N-G) surface. Thiourea was used as the nitrogen source and reducing agent for graphene oxide. The surface morphology of the as-prepared Bi2S3@N-G composites was analyzed by field emission scanning electron microscopy and transmission electron microscopy. The crystalline structure and surface chemical states were examined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The as-prepared Bi2S3@N-G composite was deposited on a glassy carbon (GC) electrode, and the modified electrode was employed for the electrocatalytic detection of H2O2. The calculated diffusion coefficient and catalytic rate constant of the Bi2S3@N-G modified electrode were 4.9 × 10-6 cm2 s-1 and 5671 M-1 s-1, respectively. The Bi2S3@N-G/GC electrode demonstrated a wide concentration range for H2O2, from 10 to 42,960 μM, with a sensitivity of 0.1535 μA μM-1 and an obtained limit of detection of 1.9 μM.