Monitoring Ozone Using Portable Substrate-Integrated Hollow Waveguide-Based Absorbance Sensors in the Ultraviolet Range

Ozone is an oxidizingmolecule used for disinfecting a wide varietyof environments, such as in dental clinics, and has most recentlybeen promoted as a sanitizing agent to prevent coronavirus transmission.The easy access to ozone-generating sources also enables their ubiquitoususe. However, exposure to ozone may seriously affect human healthby amplifying or inducing respiratory diseases and distress syndromesand has been associated with premature deaths from other diseases.In this scenario, miniaturized, low-cost, and portable optical sensorsbased on the absorption signature of ozone in the ultraviolet (UV)range of the electromagnetic spectrum are an innovative approach forproviding real-time monitoring of gaseous ozone, ensuring the safetyof indoor and workplace environments. In this paper, a miniaturizedozone sensor based on the absorption signature of ozone at deep-UVfrequencies was developed by integration of so-called substrate-integratedhollow waveguides (iHWG) with a miniaturized ultraviolet lamp anda fiber-optic USB-connected spectrophotometer. The innovative conceptof iHWGs facilitates unprecedented compact dimensions with a highdegree of flexibility in the optical design of the actual photon absorptionpath. The proposed device rapidly responded to the presence of ozone(<1 min) and revealed a suitable linearity (r (2) > 0.99) in the evaluated concentration range. The limitofdetection was determined at 29.4 ppbv, which renders the device suitablefor measurements in the threshold range of the main regulatory agencies.Given the adaptability and modularity of this platform, we anticipatethe application of this innovative concept to be equally suitablefor the in situ and real-time analysis of other relevant gases providingsuitable UV absorption signatures.