Preparation And Characterization Of The Properties Of Co (sub) 3 O ₄ Nanomaterials

Among the toxic gases of interest, ammonia is a prominent instance for its wide usage in industrial coolant and IC manufacturing. In addition, ammonia pollutions through three major origins including aerosols from atmospheric depositions, ammonification by nitrogen cycle and combustion of chemical materials will cause dramatic environmental problems in daily life. Therefore, there is a practical meaning to fabricate sensitive, stable, and low cost sensors ensuring NH3 monitor working at room temperature for the prosperous applications of environmental surveillance. High active surface areas and easy gas transmission structures of the sensor materials are key factors for improved sensing performance. In this paper, we prepared Co3O4 nanomaterials by different methods. The main research contents are as following.(1) A 1D Co3O4/polyethyleneimine-carbon nanotubes composites(CoPCNTs) have been successfully synthesized via hydrothermal method at different temperature. The PCNTs was used as growth guider and electron transfer path. The Co3O4 nanoparticles(NPs) loaded on the PCNTs surface liked a snake winding around CNTs, and the size was about 5~10 nm. The CoPCNTs sensors grown at 160 ℃ exhibited the highest response to 1000 ppm NH3 gases with response time of 4.3 s at room temperature.(2) Polystyrene(PS) spheres are widely used as a template to build a porous structure, because of its high dispersibility and controlled synthesis of different sizes. In the simple synthesis, Co(NO3)2 precursor was promoted full infusion into the gap of polystyrene sphere template under vacuum-assisted conditions, and then Co3O4 nanoparticles grow in the gap of polystyrene sphere template under calcination condition to form monodisperse Co3O4 nanoparticles. By changing the concentration of precursor can be prepared ordered porous structure. Studies have shown that the improvement of room temperature NH3 gas sensing performance for the synthesized products is due to the special porous structure. The Co-0.4M sensor has higher gas response of 146.0% and the response time of 2 s to 100 ppm NH3 at room temperature.(3) “Green” colloidal carbon spheres were prepared by hydrothermal method, and modified by NaOH. Co3O4 hollow spheres were synthesized by a carbon spheres templated strategy. The size and surface morphology of hollow spheres can be controlled by changing the concentration of precursor and aging time. The synthesis of Co-48h-0.1M materials has good gas response to 100-0.5 ppm NH3 gases at room temperature, and response time for all cycles are within 10 s. The gas sensitivity to 100 ppm NH3 is 155.8% and the response time is 1.3 s.