How to prepare exposed facet fiber-like hierarchical arrays: a facile scalable aqueous route to thermodynamically stable biphasic TiO2(A)/TiO2(R) exposed multiple facets

Abstract

The fundamental importance and practical applications of engineered well-defined exposed crystal facets have attracted intensive research interest. Herein, for the first time, a versatile corrosive-free capping agent procedure was explored to synthesize hierarchical fiber-like constructed 2D mixed thermally stable TiO₂(A)/TiO₂(R) assemblies possessing various well-defined sheet-shaped structures with exposed multiple facets. Co-axial electrospinning followed by direct sintering at different temperatures of 400 °C, 700 °C and 900 °C under conditions of acidic, natural and basic media was applied as an outstanding strategy for synthesis of the well-integrated porous TiO₂ hierarchical nanostructure arrays with different tailored/controlled-phase frameworks. The systematic study exhibited that the shell-constructed TiO₂ architecture in the co-axial electrospinning is strongly engineered by regulating the pH of the core material and the subsequent annealing temperature, where, at basic pH, a well-designed nanocrystal multi-facet TiO₂(A)/TiO₂(R) fiber-like assembly is prepared. The results are confirmed by FT-IR, XRD, FE-SEM and HR-TEM analyses. Our study is envisaged to extend the possibility of controlled single crystal growth to a range of functional ceramics and semiconductors toward advanced applications.