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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.

, respectively. Strong correlations between NO 2 with O 3 and between NO 2 with PM 10 were found. Results: These results showed that NO 2 was the precursor of the photochemical reaction and generate O 3 . NO 2 concentrations are found to be corresponding with both O 3 and PM 10 . The directions of O 3 emission sources were the southwest, south and southeast due to wind direction, whereas the PM 10 are originated from the northwest. The microscopic structures of TSP provided various shapes and dimensions from 0.1 to greater than 100 µm, while the microstructures of PM 10 presented the needle-like and spherical shape. SEM-EDS analysis was able to detect some element (C, O, F, Na, Al, Si and K), while the ICP-AES showed that there were other heavy metals present in the filter sample (Ni, Cu, Zn, Pb and Se). Conclusion: Among the amounts of selected heavy metals, Zn is the most probable among all metals with the value of 1.3891±1.6198 µg .g , the others were almost in the same levels and much lower than in TSP. Correlation coefficient between each metal can be estimate the emission source of their particulate matter together with the wind speed and wind direction.

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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.