General Synthesis of Doped Quasi‐Single‐Crystalline TiO ₂ Nanowires With Ultra‐High Length‐to‐Diameter Ratios for Building Gas Sensor Arrays

ABSTRACT Titanium dioxide (TiO 2 ), a versatile inorganic semiconductive material with a wide band gap and various crystal structures, has attracted a great deal of research interest and is used in a wide variety of fields. To build the gas sensor arrays that are the building blocks of artificial olfaction, gas‐sensitive materials with particular properties are especially desirable to introduce diverse interactions between gases and materials, transducing them into differentiated resistive changes for pattern recognition. Therefore, it is important for researchers to develop new synthesis methods in pursuit of TiO 2 nanowires (NWs) with small diameters, high length‐to‐diameter ratios, and arbitrary doping. In this study, a general and versatile method was developed for synthesizing quasi‐single‐crystalline doped TiO 2 (QSDTO) NWs with ultra‐high length‐to‐diameter ratios (ca. 200–730), small diameters (ca. 55–210 nm), and, critically, arbitrary elemental doping. The morphology, crystal phase, band gap, and elemental composition of QSDTO NWs were systematically investigated. The tunability of their physical and chemical properties through transition metal doping, which is a valuable essential feature for the gas‐sensitive materials used in sensor array applications, was clearly demonstrated. These results underscore the potential of this approach not only for the controlled synthesis of TiO 2 NWs but also for their implementation in advanced gas sensing technologies.