A Facile and Green Approach for the Controlled Synthesis of Porous SnO2 Nanospheres: Application as an Efficient Photocatalyst and an Excellent Gas Sensing Material

A facile and elegant methodology invoking the principles of Green Chemistry for the synthesis of porous tin dioxide nanospheres has been described. The low-temperature (similar to 50 degrees C) synthesis of SnO2 nanoparticles and their self-assembly into organized, uniform, and monodispersed porous nanospheres with high surface area is facilitated by controlling the concentration of glucose, which acts as a stabilizing as well as structure-directing agent. A systematic control on the stannate to glucose molar concentration ratio determines the exact conditions to obtain monodispersed nanospheres, preferentially over random aggregation. Detailed characterization of the structure, morphology, and chemical composition reveals that the synthesized material, 50 nm SnO2 porous nanospheres possess BET surface area of about 160 m(2)/g. Each porous nanosphere consists of a few hundred nanoparticles similar to 2-3 nm in diameter with tetragonal cassiterite crystal structure. The SnO2 nanospheres exhibit elevated photocatalytic activity toward methyl orange with good recyclability. Because of the high activity and stability of this photocatalyst, the material is ideal for applications in environmental remediation. Moreover, SnO2 nanospheres display excellent gas sensing capabilities toward hydrogen. Surface modification of the nanospheres with Pd transforms this sensing material into a highly sensitive and selective room-temperature hydrogen sensor.