Growth of novel tin oxide nanocrystals under different pH: Structure evolution, broad spectrum response and photocatalytic activity

Abstract

Two-dimensional (2D) van der Waals (vdW) heterostructures are highly attractive for fabricating nanodevices due to their high surface-to-volume ratio and good compatibility with device design. In this work, without using any surfactant, the different mixed valence tin oxides were prepared by controlling the pH value of the precursor solution under simple hydrothermal condition. When the pH is at 3.22, Sn₃O₄ 2D vdW nanocrystals will be produced, which have the characteristic of layered structure with mixed valence as confirmed by HRTEM and XPS analysis. The Sn₃O₄ nanocrystals show excellent adsorption and photocatalytic activity under the visible and infrared light, which is attributed to two-dimensional layered morphology, especial electrical structure and large mesopores structure. As the pH is increased to 9.72, SnO 2D nanocrystals with a layered structure similar to Sn₃O₄ could be generated, which have an obvious infrared response. Moreover, while the pH is decreased to 0.89, the tetragonal rutile phase SnO_2-x nanocrystals with rich oxygen vacancies can be obtained. These tin oxides with different structures exhibit broad photo-response and high photocatalytic performance respectively.