Room temperature optical detection of ultra-low ozone concentration using photoluminescent ZnO nanohybrids

The highly sensitive room temperature (RT) photoluminescence (PL) emission of zinc oxide (ZnO) in the presence of ozone (O3) is demonstrated for the first time. The optical materials examined consist of commercially available luminescent ZnO nanoparticles (ZnO NPs), as well as ZnO/polymer nanohybrids, with different polymeric matrices (poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) and polydimethylsiloxane (PDMS)), which are excited with a UV pulsed laser source (λex= 248 nm, τex= 15 ns). The PL emission of the ZnO NPs and their nanohybrids (ZnO/PPEGMA, ZnO/PDMS) is investigated upon exposure to ozone gas and their sensing characteristics, such as response (%ΔI), reversibility, response/recovery time are determined, as a function of ozone concentration in synthetic air. Sensing tests revealed that all materials allowed the detection of ozone gas in a wide range of concentrations in synthetic air (1600 down to 50 ppb), with the ZnO/PDMS nanohybrid exhibiting the highest response and recovery time of about 50 s (at 750 ppb ozone concentration) and 100 s, respectively. Finally, its remarkable optical response of about 20% at 50 ppb ozone concentration at RT, underlines the great potential of the ZnO/PDMS nanohybrid to serve as a sensitive probe for ozone detection, thereby introducing new developments in optosensing applications.