Flower-like NiO microspheres modified glassy carbon electrode for enzyme- free detection of L-Glutamic acid

In the present work, flower-like nickel oxide microspheres (fl-NiO) were synthesized via a hydrothermal route combined with and calcination process. Morphological characterization of fl- NiO was carried out using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The as-prepared microspheres modified a glassy carbon electrode by drop casting and exhibited remarkable electro-catalytic activity of fl-NiO towards L-glutamic acid oxidation in ۱ M NaOH solution. Electrochemical measurements were performed using cyclic voltammetry (CV) and Chrono-amperometry (CA) in ۱ M NaOH solutions, revealing a well- defined redox couple of Ni۲+/Ni۳+. So NiO is oxidized to NiOOH in the presence of ۱ M NaOH, which electrogenerated Ni۳+ species on the electrode surface act as an excellent catalyst toward the L-glutamic acid oxidation reaction (Fig۱). Amperometric responses for fl-NiO/GCE were recorded during the sequential addition of ۱۰۰ μM L-glutamic acid in ۱ M NaOH at an applied potential of۰.۵۵ V(Fig ۲). The electrochemical response of the sensor was found to be linear in the range of ۱۰۰ μM - ۸۰۰ μM. The sensitivity of the electrode is found to be ۰.۲ μAμM-۱cm-۲. The detection limit is estimated to be ۱۹ μM by using signal-noise ratio of ۳. The proposed L-glutamic acid sensor was successfully used to analyze the blood serum sample and had shown excellent reproducibility and good stability. Thus, this methodology for developing free enzyme sensors could be a simple and efficient route in the field of detection sector on a wide scale.