Calcination-influenced interfacial structures and gas-sensing properties of multi-walled carbon nanotube-tin oxide p-n heterojunctions

Multi-walled carbon nanotube-tin oxide (MWCNT-SnO2) p-n heterojunctions were synthesized using the SnCl2 solution method. The influence of the calcination on the interfacial structure was investigated using scanning and transmission electron microscopy, Raman spectroscopy, X-ray diffraction, thermal analysis, and N-2 adsorption-desorption isotherms. The interfacial structure influenced gas-sensing properties were revealed. The heterojunctions calcined at 550 degrees C under an Ar atmosphere show the strongest interactions between the MWCNTs and SnO2. The strong interactions favored electron transfer, and also resulted in improved gas-sensing properties. After calcination at 650 degrees C, the increased pore diameter and pore volume, and the improved crystallinity play key roles in the improvement of gas-sensing properties.