Colorimetric oxygen sensor based on nano-sized black TiO2 catalysts: DFT modeling and experiments

Abstract

There are the imperious demands for novel oxygen (O2) sensors in cutting-edge biochemical technologies and industrial hygiene. Here, we develop a colorimetric O2 sensor based on a spherical nano-sized reduced TiO2 (TiO2 –x) catalyst, which resolves the critical bottlenecks of conventional systems. The sensing mechanism of our O2 sensors relies on two characteristics which are proven by simulations based on density functional theory (DFT) calculations. First, nano-TiO2–x, in the partially reduced form, shows a rapid, reversible O2 uptake at room temperature. Second, the partially reduced form of nano-TiO2–x, called black TiO2, shows a change in the lightness of color. Owing to these characteristics, the developed sensor it is well-suited for use at ambient temperature/pressure in the absence of a reference gas, in contrast with the conventional system. Also, it allows long-term operations and it can withstand degradation because the former comprises solid-state inorganic compounds.