Design and Synthesis of Nanostructured Porous SnO<sub>2</sub> with High Surface Areas and Their Optical and Dielectric Properties

A new structure-directing agent, hexadecyl-2-pyridinyl-methylamine, L<sub>16</sub>, was prepared through Schiff base condensation between pyridine-2-carboxaldehyde and hexadecylamine followed by reduction of the imine with NaBH<sub>4</sub>. Mesoporous and supermicroporous tin oxide particles with crystalline pore walls were obtained through a low-temperature sol–gel synthesis process by using an anionic surfactant, sodium dodecylsulfate, and hexadecyl-2-pyridinyl-methylamine, respectively, as templates. Powder X-ray diffraction, transmission electron microscopy−energy-dispersive spectrometry, field emission scanning electron microscopy, CHN chemical analysis, N<sub>2</sub> sorption, <sup>1</sup>H and <sup>13</sup>C NMR, high-resolution mass spectrometry, Fourier transform infrared spectroscopy, and UV–vis absorption spectroscopic tools were employed to characterize L<sub>16</sub> and nanostructured SnO<sub>2</sub> materials. X-ray diffraction and transmission electron microscopy image analyses suggested that these porous materials have a wormhole-like disordered arrangement of pores, whereas the pore walls are crystalline. Nitrogen physisorption studies show high specific surface areas up to 555 m<sup>2</sup> g<sup>−1</sup>, and the uniform nanoscale pore size distribution ranged from supermicropore to mesopores for these materials. These SnO<sub>2</sub> materials showed drastic reduction of dielectrics with the induction of porosity vis-à-vis bulk SnO<sub>2</sub>. These unique optical and electrical properties of porous SnO<sub>2</sub> materials over bulk SnO<sub>2</sub> could be attributed to the quantum confinement effect.