The electrical properties of tin dioxide (SnO2) nanoparticles induced by low calcination temperature were systematically investigated for gas sensing applications. The precipitation method was used to prepare SnO2 powders, while the sol-gel method was adopted to prepare SnO2 thin films at different calcination temperatures. The characterization was done by X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The samples were perfectly matched with the rutile tetragonal structure. The average crystallite sizes of SnO2 powders were 45 ± 2, 50 ± 2, 62 ± 2, and 65 ± 2 nm at calcination temperatures of 300, 350, 400, and 450°C, respectively. SEM images and AFM topographies showed an increase in particle size and roughness with the rise in calcination temperature. The dielectric constant decreased with the increase in the frequency of the applied signals but increased on increasing calcination temperature. By using the UV-Vis spectrum, the direct energy bandgaps of SnO2 thin films were found as 4.85, 4.80, 4.75, and 4.10 eV for 300, 350, 400, and 450°C, respectively. Low calcination temperature as 300°C allows smaller crystallite sizes and lower dielectric constants but increases the surface roughness of SnO2, while lattice strain remains independent. Thus, low calcination temperatures of SnO2 are promising for electronic devices like gas sensors.

In this study, the effect of temperature treatment during the preparation process of calcium carbonate (CaCO 3) nanoparticles was systematically examined for a drug delivery carrier. The CaCO 3 powder was prepared by the precipitation method at different annealing temperatures. The morphologies, elemental compositions and crystal structures of the synthesized CaCO 3 powder were analyzed by Scanning Electron Microscope/Energy-Dispersive Spectroscopy and X-ray Diffractometry (XRD), respectively. The result shows that the particle size increased with an increase in annealing temperature. Based on the crystal structure analyzed from XRD, the sample was perfectly matched with the calcite/ vaterite polymorphs phases. The crystallite size and lattice strains of the CaCO 3 powder were calculated from the full width at half maximum parameter. The results show that the increase in annealing temperature leads to an increase in crystallite size and a decrease in lattice strain. The CaCO 3 powder has a dielectric constant of 6.0-6.8 that reduced with the increase in applied frequency. The crystal structure, crystallite size, lattice strain, and dielectric properties of CaCO 3 powder are dependent of the annealing temperature. Such properties confirm that CaCO 3 powder is suitable for drug delivery carrier application.

Titanium dioxide (TiO2) thin films have been deposited on Si-wafer and glass slide by DC reactive magnetron sputtering technique at different O2 gas flow rates. The crystal structure was characterized by grazing-incidence X-ray diffraction (GIXRD), surface morphology was analyzed by atomic force microscopy (AFM) and disinfection of surfaces by photo catalytic oxidation with TiO2 and UV light irradiation. The results showed that, from GIXRD results, all as-deposited TiO2 films have crystal structure of TiO2 corresponding to the A(101) and A(200). AFM results showed that the film thicknesses increase from 183 nm to 238 nm with increasing of O2 gas flow rate, while the film roughness was in range of 4.8 nm to 5.9 nm. The as-deposited anatase TiO2 thin film in this work can kill the bacteria when expose to the UV light.

No abstract