Mohamed A Basyooni had completed his MSc from Nanophotonics and Applications (NPA) Lab, Department of Physics, Faculty of Science, Beni-Suef University. Currently, he is pursuing PhD in nanocomposites for satellite and space applications.
CO2 is considered as one of the primary greenhouse gases in the Earth’s atmosphere, Nevertheless, monitoring the content of the CO2 in the environment and emissions is important. There is a highly significant need for CO2 sensors for space and commercial application, as well. Those applications include low-false-alarm fire detection which detect chemical species indicative of a fire (e.g., CO2 and CO). In this work, we are focusing on the carbon dioxide chemiresistive sensor under practical environment, i.e., atmospheric pressure, oxgygen free environment and room temperature by ZnO and ZnO: Na wrinkle network structure. The structural, optical, electrical properties using scan electron microscope and X-ray diffraction of the prepared film were studied. Sensor parameters such as dynamic response, response magnitude, response time and recovery time were studied at room temperature for different concentrations of CO2 gas. The detection limit of the sensor from the sensor’s signal processing performance was calculated to be 0.42 sccm. The dynamic response curves for ZnO and ZnO: Na for gas volumes of 20, 30, 40, and 50 cm3 of CO2 for 5 minutes in an inert environment at room temperature have been demnostrated. It can be observed for both cases that upon exposure to CO2, the increased resistance of the ZnO film confirmed its n-type semiconducting behavior. For such new technique of gas sensing in room temperature, the sensor response mechanism can be attributed to direct charge transfer on metal conductivity with additional electron hopping effects on intertube conductivity through physically adsorbed molecules between the network nanostructur, another reson is the smaller particle size and thus larger surface-to-volume ratio of ZnO:Na in addition to the small band gap which enable ZnO: Na sensor to operate at room temperature.
Panta P C is Postdoctoral student in the Department of Materials Engineering at the Federal University of Rio Grande do Sul, Brazil.
Nanoparticles of iron oxide (Fe3O4) were obtained by co-precipitation with synthesis time of 30, 60 and 90 min. The morphology of the samples was investigated by transmission electron microscopy (TEM) and structural characteristics were obtained by X-ray diffraction (XRD). The crystallite size was calculated from the spectrum Xray diffraction with the application of the Scherrer equation and Winfit. The crystallite size varied from 4.6 to 14.4 nm when calculated by Scherrer equation and when calculated by the single line ranged from 7.5 to 22.3 nm Winfit. The degree of graphitization was studied by Raman spectroscopy where spectrums were analyzed with different lasers: 514 nm (0.75 mW power used) and 785 nm (1.2 mW power used). The dominant structures of the spectra are in 215, 276, 398, 487, 654 and 1300 cm-1 when using the laser 514 nm. The spectrum produced with laser 514 nm is characteristic peak of magnetite in 654 cm-1. The spectrum produced by laser 785 nm has a peak at 670 cm-1, shifted relative to the laser 514 nm. The spectrum generated by laser 785 nm peaks characteristic of maghemiteen countered due to possible oxidation of the sample caused by the high power laser. The experimental results were satisfactory and are according to the survey.