Orientation Control (Horizontal and Vertical) of TiO2 Single-Crystalline Nanowire Arrays for High-performance Gas Sensing: A Surface Supersaturation-driven Approach

Abstract

In the field of advanced functional nanoarrays, the development of one-dimensional (1D) single crystalline nanoarrays (SCNAs) with high-orientated alignment is of paramount significance due to their essential roles in batteries, catalysis, and sensing applications. However, controlling the SCNAs with uniform orientation presents an extremely challenge. Herein, a surface supersaturation-driven hydrothermal growth approach is proposed which successfully modulates the growth directions of TiO2 nanowires. By precisely tuning the concentrations of crystal seed solution, a series of highly-aligned TiO2 SCNAs are achieved which grow horizontally (TiO2-H-NAs) or vertically (TiO2-V-NAs) on sapphire. Compared with TiO2-V-NAs, TiO2-H-NAs shows better sensing performances towards ethanol at room temperature, which represents one of the highest responses among various material categories, including metal oxides semiconductors, metal organic frameworks, 2D materials and polymers. Demonstrating its practical utility, TiO2-H-NAs has showcased an obvious response value (288%) to a mimic of exhalation detection after drinking wine, underscoring its potential in real-time monitoring applications. This study offers a promising pathway to overcome the synthetic challenges and unlock the full potential of 1D nanowires for various chemical applications.