Search

Carbon-based structures have attracted attention due to their unique properties, combining excellent chemical, thermal mechanical, and electrical features. The use of microwave irradiation has been used to produce graphene materials and the identification of optimum synthesis parameters is crucial for the production of high-quality carbon structures. Herein, we describe a detailed temperature study for the production of expanded graphite nanosheets (GNs) via intercalation of sulfuric and nitric acids, followed by a rapid and energy-efficient process of microwave-assisted expansion and exfoliation. The results demonstrate that the proposed methodology was efficient in producing high-quality GNs with a size of approximately 1 nm. The temperature investigation revealed that heat treatment of 800 °C was the best, resulting in a high-quality material, achieving maximum expansion with the lowest weight loss related to thermal degradation. Thus, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests confirmed good electrochemical features of the sample produced at a temperature of 800 °C. [ABSTRACT FROM AUTHOR]

Lithium niobate (LiNbO3) is an important ferroelectric material with a wide range of applications. In this work, the use of microwave radiation to improve the conditions of hydrothermal synthesis of pure nanocrystalline LiNbO3 was proposed. The structural characterization showed that nanoparticles of a pure LiNbO3 phase were synthesized. The scanning electron microscopy and transmission electron microscopy analysis revealed a high-quality nanoparticle with an average diameter of ca. 42 and 65 nm for 2 and 3 h of synthesis time, respectively. These results represent a time-saving using a microwave-assisted hydrothermal method for LiNbO3 preparation, with excellent quality at the nanometer scale. The nanoparticles were employed as photocatalysts for hydrogen evolution reaction through water splitting, reaching the rate of 10.5 µmol h−1 g−1. It had shown to be a potential candidate for water photolysis due to the small particle size and high crystallinity. Moreover, it also allows the direct and fast synthesis of LiNbO3 on carbon fiber, multi-walled carbon nanotubes and nanocellulose, which were used as supporting materials for the fabrication of novel nanocomposites. [ABSTRACT FROM AUTHOR]

In this work, Ag-doped CeO2 samples containing 0.5 mol% Ag+ were successfully synthesized by the polymeric precursor method and then calcined at 400, 500, 600 and 700 °C for 2 h. X-ray diffraction and Raman spectra indicated that the crystals have a fluorite-type structure without the presence of other phases. The size of the Ce0.95Ag0.05O1.9−δ crystals increased from 6.61 to 27.46 nm upon increasing the thermal treatment temperature. The decomposition of the samples was examined by differential thermal analysis to determine the most suitable calcination temperature to apply to the materials and indicate the steps involved in obtaining Ag-doped ceria. Scanning electron microscopy images revealed small crystallite sizes, the presence of oxygen vacancies, structural stability and homogeneity. The Ag-doped ceria have shown effective and efficient antimicrobial activity, inhibiting the growth of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa bacteria. However, pure CeO2 displayed no antibacterial activity. Therefore, the satisfactory antimicrobial activity reported here can be attributed to the partial substitution of cerium ions by silver ions. [ABSTRACT FROM AUTHOR]