SnO2 Quantum Dots and Quantum Wires: Controllable Synthesis, Self-Assembled 2D Architectures, and Gas-Sensing Properties

Abstract

SnO₂ quantum dots (QDs) and ultrathin nanowires (NWs) with diameters of ∼0.5−2.5 and ∼1.5−4.5 nm, respectively, were controllably synthesized in a simple solution system. They are supposed to be ideal models for studying the continuous evolution of the quantum-confinement effect in SnO₂ 1D → 0D systems. The observed transition from strong to weak quantum confinement in SnO₂ QDs and ultrathin NWs is interpreted through the use of the Brus effective-mass approximation and the Nosaka finite-depth well model. Photoluminescence properties that were coinfluenced by size effects, defects (oxygen vacancies), and surface capping are discussed in detail. With the SnO₂ QDs as building blocks, various 2D porous structures with ordered hexagonal, distorted hexagonal, and square patterns were prepared on silicon-wafer surfaces and exhibited optical features of 2D photonic crystals and enhanced gas sensitivity.