Growth mechanism and cathodoluminescence properties of indium hydroxide nanocubes synthesized from a simple aqueous solution

Abstract

Single-crystalline In(OH)₃ nanocubes were synthesized in a simple aqueous solution, without using a surfactant, at a temperature as low as 90 °C. To elucidate the growth mechanism, the structural evolution of In(OH)₃ nanocubes during the synthesis process were carefully examined. The experimental results showed that the formation of the In(OH)₃ nanocubes is primarily guided by the oriented attachment mechanism, following a zero-dimensional (0D) → one-dimensional (1D) → three-dimensional (3D) mode. The 0D In(OH)₃ nanoparticles will first assemble to form 1D nanorods, then the nanorods will orientedly attach to form 3D nanorod bundles and finally the In(OH)₃ nanorod bundles will fuse into strip-like or square nanocubes. Small strip-like or square nanocubes can further orientedly attach and fuse into big single-crystalline strip-like or square nanocubes. However, the growth of strip-like and square nanocubes may also occur based on the Ostwald ripening. The cathodoluminescence (CL) spectra at room temperature of the as-synthesized In(OH)₃ nanocubes exhibited a weak ultraviolet luminescence at 350 nm (3.54 eV) and a strong blue luminescence at 450 nm (2.75 eV), which can be attributed to the hydroxy ion defects generated by the incomplete reaction of the In³⁺ ions with OH⁻ radicals during the synthesis process.