Electrocatalytic Properties of a BaTiO3/MWCNT Composite for Citric Acid Detection

Although barium titanate (BaTiO3) shows prominent dielectric properties for fabricating electronic devices, its utilization in electrochemical applications is limited. Thus, this study examined the potential of a BaTiO3-based composite in the detection of a food additive, i.e., citric acid. First, a submicron-scale BaTiO3 powder was synthesized using the solution combustion method. Then, a BaTiO3/multiwalled carbon nanotube (MWCNT) composite was hydrothermally synthesized at BaTiO3:MWCNT mass ratios of 1:1 and 2:1. This composite was used as a working electrode in a nonenzymatic sensor to evaluate its electrocatalytic activity. Cyclic voltammetric measurements revealed that the BaTiO3/MWCNT composite (2:1) exhibited the highest electrocatalytic activity. Reduction reactions were observed at applied voltages of approximately 0.02 and −0.67 V, whereas oxidation reactions were detected at −0.65 and 0.47 V. With acceptable sensitivity, decent selectivity, and fair stability, the BaTiO3/MWCNT composite (2:1) showed good potential for citric acid detection.

Sol-Gel Combustion Synthesis, Crystal Structure and Luminescence of Cr3+ and Mn4+ Ions in Nanocrystalline SrAl4O7

A series of strontium dialuminate SrAl4O7 nanopowders with the grossite-type structure doped with chromium and manganese ions were synthesized by the combined sol–gel solution combustion method with use of two different strontium salts. The Cr3+ and Mn4+ ions concentrations were varied from 0.05 to 5 at.%. Evolution of phase composition, crystal structure, and microstructural parameters of the nanocrystalline materials depending on the synthesis conditions, temperature of thermal treatment, and dopant content were investigated by the X-ray powder diffraction and the scanning electron microscopy techniques. Photoluminescent properties of SrAl4O7 nanophosphors activated with Cr3+ and Mn4+ ions were studied at room temperature. The samples exhibit typical photoluminescence in the deep-red spectral region, corresponding to d-d transitions in Cr3+ or Mn4+ ions. The intensity of this deep-red emission is dependent on the dopant concentration and annealing temperature. Features of the formation of octahedral surroundings around Cr3+ or Mn4+ ions are discussed.

Green Synthesis of Ni-Cu-Zn Based Nanosized Metal Oxides for Photocatalytic and Sensor Applications

The preparation, characterization, and application of Nickel oxide (NiO)–Copper oxide (CuO)–Zinc oxide (ZnO) transition nanometal oxides have significantly enhanced their tunable properties for superior multifunctional performances compared with well-known metal oxides. NiO–CuO–ZnO nano transition metal oxides were synthesized by a simple eco-friendly solution combustion method. X-ray diffraction studies revealed distinct phases such as monoclinic, cubic, and hexagonal wurtzite for CuO, NiO, and ZnO, respectively, with NiO having the highest composition. The particle sizes were found to be in the range between 25 and 60 nm, as determined by powder X-ray diffraction. The energy bandgap values were found to be 1.63, 3.4, and 4.2 eV for CuO, ZnO, and NiO, respectively. All metal oxides exhibited a moderate degradation efficiency for AR88 dye. The results of ultraviolet–visible absorption spectra helped identify the bandgap of metal oxides and a suitable wavelength for photocatalytic irradiation. Finally, we concluded that the electrochemical studies revealed that the synthesized materials are well suitable for sensor applications.

Preparation of NiFe2O4 Nanoparticles by Solution Combustion Method as Photocatalyst of Congo red

NiFe2O4 nanoparticles had been successfully synthesized by solution combustion method using urea fuel (organic precursor). The synthesized NiFe2O4 were characterized by X-ray diffraction (XRD), Scanning electron microscopy-Electron Dispersive X-ray Spectroscopy (SEM-EDs), Transmission Electron Microscopy (TEM), Fourier Transform Infra-Red (FTIR), Vibrating Sample Magnetometer (VSM), UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS), and Point of Zero Charge (pHpzc). NiFe2O4 nanoparticles irradiated with visible light were employed to degrade Congo red dye with the following variable: solution pH (3–8), H2O2 concentration (0.5–3 mM), and Congo red concentration (100–600 mg/L). XRD analysis results showed that the NiFe2O4 nanoparticles had a cubic spinel structure. The particle sizes are in the range of 10–40 nm. The magnetic properties of NiFe2O4 nanoparticles determined using VSM showed a magnetization saturation value of 47.32 emu/g. UV-Vis DRS analysis indicated that NiFe2O4 nanoparticles had an optical band gap of 1.97 eV. The success of synthesis was also proven by the EDS analysis results, which showed that the synthesized NiFe2O4 nanoparticles composed of Ni, Fe, and O elements. The removal efficiency of Congo red dye was 96.80% at the following optimum conditions: solution pH of 5.0, H2O2 concentration of 2 mM, Congo red dye concentration of 100 mg/L, and contact time of 60 min. The study of the photodegradation kinetics follows a pseudo-first order reaction with a rate constant value of 0.0853 min−1. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).