Synthesis of hierarchical TiO2 nanotube arrays assembled by anatase single crystal nanoparticles

Abstract

Hierarchical TiO2 nanotube (HTNT) arrays assembled by anatase single crystal nanoparticles (NPs) were synthesized via in situ chemical etching of anodic TiO2 nanotube (TNT) arrays. The process starts with the fabrication of smooth and crack-free anodic TNT arrays by employing an improved anodization method, which is used both as the starting material and a template for the synthesis of HTNT. The as-fabricated HTNT retains the tubular array structure as in the original anodic TNT, and the walls of HTNT possess a porous structure, consisting of anatase TiO2 single crystal NPs. The formation mechanism of the HTNT was thoroughly investigated, proposing that a dissolution–recrystallization procedure of the anodic TNT under in situ chemical etching of hydrofluoric acid leads to the transformation from TNT arrays to HTNT arrays. Such HTNT structure has higher specific surface area and better crystallinity than the original anodic TNT, and possess one-dimensional passageways resulting in prominent advantages for the exchange and transportation of charge or mass, and could be an ideal candidate for many practical applications.