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

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.