Construction of 0, 1, 2 and 3 dimensional SnO2 nanostructures decorated by NiO nanopetals: Structures, growth and gas-sensing properties

Different morphologies of SnO2 nanostructures, such as zero-dimensional (0D) nanoparticles (np), one-dimensional (1D) nanowires (nw), two-dimensional (2D) nanosheets (ns), and three-dimensional (3D) nanoflowers (nf) were synthesized by a user friendly and facile method just changing the kind of surfactant as morphology-director and structure-growth agent. NiO nanopetals (npe) were also synthesized by a direct precipitation method. Nanostructured SnO2-NiO hybrids with these four morphologies of SnO2 were also synthesized by a precipitation method. The structures, morphologies, and the surface area of the samples were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area analyzer (using BET method), respectively. The surface area of the synthesized SnO2 nanostructures in the forms of particle, wire, sheet and flower were 45, 94, 11 and 33 m2 g−1, respectively. Gas sensing properties of these hybrid nanomaterials and the non-hybrid SnO2 were studied against ammonia gas. The hybrids showed much better performance, which could be related to the role of nickel oxide as a p-type semiconductor in these hybrids. Furthermore, the comparison between the sensitivities of these four hybrids indicated that SnO2 nw-NiO hybrid had the highest sensitivity and the shortest response time, most probably because of its highest surface area and porous structure. This wire-petal hetero-junction also showed good selectivity towards NH3 in presence of other gases including CO, NO, SO2, BTEX and ethanol.