Template-free solvothermal synthesis of hollow hematite spheres and their applications in gas sensors and Li-ion batteries

Abstract

Magnetite (Fe(3)O(4)) hollow spheres were prepared by solvothermal reaction of ethanol solution containing Fe-acetate and L-lysine, and were subsequently transformed into hematite (Fe(2)O(3)) hollow spheres with nanoscale (20-30 nm) thin shells by heat treatment at 500 degrees C for 2 h. Both the as-prepared and heat-treated hollow spheres contained another small sphere within each shell, which was attributed to the following solvothermal self-assembly reactions: (1) the nucleation of Fe(3)O(4) spheres, (2) lysine capping on the nuclei, (3) the growth of lysine-capped particles by cross-linking between lysine molecules, and (4) the formation of Fe shell layers by the interaction between Fe ions and outer lysine molecules. In the assembly reaction, L-lysine with amino and carboxyl radicals played the key role. The heat-treated Fe(2)O(3) hollow spheres showed significantly enhanced C(2)H(5)OH sensing characteristics and promising Li-ion intercalation behaviors.