Evolution of Nanoscale SnO₂ Grains, Flakes, and Plates into Versatile Particles and Films through Crystal Growth in Aqueous Solutions

Abstract

Hierarchically structured porous particles and films consisting of nanocrystalline SnO 2 were spontaneously grown by gradual oxidation of tin(II) in a simple aqueous system at a low temperature. The nanoscale shape and macroscopically assembled architecture of SnO 2 crystallites were totally controlled by preparation conditions for crystal growth. Spherical and prickly particles exhibiting a high specific surface area in the range of 120-230 m 2 /g were produced by organized growth of nanoscale SnO 2 grains and flakes, respectively. Porous SnO 2 films consisting of the nanograins and nanoflakes were directly grown on a glass substrate through heterogeneous nucleation promoted by addition of urea. Cellular aggregates and films composed of platy subunits were constructed in the solutions under an oxygen-deficient condition. Amorphous and monoxide phases contained in as-deposited particles and films were easily transformed into SnO 2 crystals without deformation of the macroscopic architecture by subsequent hydrothermal treatment at 150 °C in water and calcination at 500 °C in air, respectively. The easyto-handle nanocrystalline SnO 2 with hierarchical and porous architectures would be utilized for various practical applications.

Morphology Control of Metal Oxide Nanocrystals

“…A variety of SnO 2 nanostructures including nanowires, nanobelts 165 , nanotubes 150,166,167 , nanorods 168,169 , spirals, nanorings 170 , zigzag nanobelts 171 , grains 172 , flakes 172 , plates 172 , meshes 173 and columnar thin film 149 were synthesized. Tin chlorides (SnCl 2 or SnCl 4 ) were commonly used in many reports.…”

Nanofabrication of Metal Oxide Patterns Using Self-Assembled Monolayers

“…106 and so on. Various kinds of tin oxide nano-structures such as nano-fibers 107 , nano-wires 108,109 , nano-belts 110 , nano-tubes 111 , nano-rods 112,113 , spirals, nano-rings 114 , zigzag nano-belts 115 , grains 116 , flakes 116 , plates 116 , meshes 117 and columnar thin films 118 were reported. Surface coating of substrates with tin oxide nano-structures are strongly required for the future devices.…”

Characterization of SnO2 thin films prepared by a liquid phase deposition method and dynamic responses to alcohol vapors

“…Actually, the oxidation state of tin changed from +2 in SnF2 to +4 in SnO2 but it was not clear which stage the oxidation took place. Some authors suggested that the dissolved oxygen related to the valence change from Sn 2+ to Sn 4+ as 23) -26) SnF2 + H2O + 1/2O2 SnO2 + 2HF…”