Recent Improvements on Double-Parametric Optical Sensing of O2 Exploiting Near-Infrared Luminescence of Mixed-Phase Anatase/Rutile TiO2 Nanoparticles

Mixed-phase titanium dioxide (TiO2) can be effectively employed as photoluminescence (PL) based ratiometric optical sensor of O2, thanks to its peculiar “anti-correlated” PL responses to O2 of anatase and rutile TiO2 polymorphs. We discuss how to exploit the simultaneous detection of luminescence arising from anatase and rutile TiO2 nanoparticles to obtain a responsivity which is, by construction, larger than the one obtainable through other gas-responsive oxides via the same PL-based approach. Furthermore, we illustrate our recent improvements on sensor sensitivity and stability for O2 concentrations ranging in the 10–100 ppm interval.