Fabrication of Gd2O3 Nanosheet-Modified Glassy Carbon Electrode for Nonenzymatic Highly Selective Electrochemical Detection of Vitamin B2.

A novel Gd2O3 nanosheet was synthesized by the template-free chemical coprecipitation method. Interestingly, upon calcination at 600 °C, nanoparticles were transformed into a nanosheet, as observed from field emission scanning electron microscopy (FESEM) images. An increase in the calcination temperature to 600 °C increases the particle size to 50 nm, which results in aggregation. A sheetlike Gd2O3 exhibits superparamagnetism from 300 K. The highly selective nonenzymatic sensing of riboflavin (RF) was studied using a modified glassy carbon electrode with Gd2O3 nanosheets, and its various applications were made possible by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The redox behavior of the RF was determined. The newly fabricated sensor showed high sensitivity, stability, and reproducibility and was also tested with a commercial vitamin B2 tablet and a milk powder sample.

Ni-CeO2 spherical nanostructures for magnetic and electrochemical supercapacitor applications.

The synthesis of nanoparticles has great control over the structural and functional characteristics of materials. In this study, CeO2 and Ni-CeO2 spherical nanoparticles were prepared using a microwave-assisted method. The prepared nanoparticles were characterized via thermogravimetry, X-ray diffraction (XRD), Raman, FTIR, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and cyclic voltammetry (CV). The pure CeO2 sample exhibited a flake-like morphology, whereas Ni-doped CeO2 showed spherical morphology with uniform shapes. Spherical morphologies for the Ni-doped samples were further confirmed via TEM micrographs. Thermogravimetric analyses revealed that decomposition varies with Ni-doping in CeO2. XRD revealed that the peak shifts towards lower angles for the Ni-doped samples. Furthermore, a diamagnetic to ferromagnetic transition was observed in Ni-doped CeO2. The ferromagnetic property was attributed to the introduction of oxygen vacancies in the CeO2 lattice upon doping with Ni, which were confirmed by Raman and XPS. The pseudo-capacitive properties of pure and Ni-doped CeO2 samples were evaluated via cyclic voltammetry and galvanostatic charge-discharge studies, wherein 1 M KOH was used as the electrolyte. The specific capacitances were 235, 351, 382, 577 and 417 F g-1 corresponding to the pure 1%, 3%, 5% and 7% of Ni doped samples at the current density of 2 A g-1, respectively. The 5% Ni-doped sample showed an excellent cyclic stability and maintained 94% of its maximum specific capacitance after 1000 cycles.