Multi-shelled copper oxide hollow spheres and their gas sensing properties

In this work, multi-shelled copper oxide hollow composite microspheres with tunable shell number and composition were successfully synthesized by means of hard template method. The source for the carbonaceous microspheres templates affects the compositions of the final copper oxides spheres critically. When changing the sucrose to glucose, the composite hollow spheres of cupric oxide (CuO) and cuprous oxide (Cu2O) were synthesized instead of the pure CuO hollow spheres. The structure of products can be tuned from single-, double- to triple-shelled hollow spheres by precisely increasing the calcination rate. The pure CuO hollow-shell spheres had uniform diameters of about 900 nm and an average shell thickness of 45 nm. While the diameters and thicknesses of Cu2O/CuO composite hollow-shell spheres are 90–500 nm and 15–35 nm, respectively. Both of these two kinds of hollow-shell spheres showed much improved response to ethanol gas as gas sensors, the triple-shelled CuO/Cu2O hollow spheres exhibited the highest response at 140 °C, 1000 ppm.