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

Abstract

Ozone is an oxidizing molecule used for disinfecting a wide variety of environments, such as in dental clinics, and has most recently been promoted as a sanitizing agent to prevent coronavirus transmission. The easy access to ozone-generating sources also enables their ubiquitous use. However, exposure to ozone may seriously affect human health by amplifying or inducing respiratory diseases and distress syndromes and has been associated with premature deaths from other diseases. In this scenario, miniaturized, low-cost, and portable optical sensors based on the absorption signature of ozone in the ultraviolet (UV) range of the electromagnetic spectrum are an innovative approach for providing real-time monitoring of gaseous ozone, ensuring the safety of indoor and workplace environments. In this paper, a miniaturized ozone sensor based on the absorption signature of ozone at deep-UV frequencies was developed by integration of so-called substrate-integrated hollow waveguides (iHWG) with a miniaturized ultraviolet lamp and a fiber-optic USB-connected spectrophotometer. The innovative concept of iHWGs facilitates unprecedented compact dimensions with a high degree of flexibility in the optical design of the actual photon absorption path. 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 limit of detection was determined at 29.4 ppbv, which renders the device suitable for measurements in the threshold range of the main regulatory agencies. Given the adaptability and modularity of this platform, we anticipate the application of this innovative concept to be equally suitable for the in situ and real-time analysis of other relevant gases providing suitable UV absorption signatures.

Recent trends in ozone sensing technology

“…Several countries across the globe have similar air quality standards for health safety. 1,2 At the ground level, the air quality standard for ozone is 60 ppb for 8 h. The concentration range recognized by OSHA for workstations as the occupational exposure limit (OEL) is 50-200 ppb, which is the recommended contact duration. 3,4 The primary source of ozone in the troposphere is the stratosphere, 5,6 while its second source is the photochemical reactions of NO x and volatile organic compounds (VOCs).…”

Wearable Nano-Based Gas Sensors for Environmental Monitoring and Encountered Challenges in Optimization

“…Researchers have developed an ozone sensor utilizing a UV sensor [239]. The developed sensor uses an aluminum-coated substrate-integrated hollow waveguide (iHWG) and a portable spectrophotometer for real-time ozone monitoring.…”

Fabrication of Low-Cost Miniaturized Gas Cells via SLA 3D-Printing for UV-Based Gas Sensors

“…The development of an iHWG for the ultraviolet (UV) range represents a challenging but promising opportunity, especially for gas-sensing applications. , The UV spectrum covers a broad spectrum of gaseous molecules that exhibit pronounced absorption characteristics in the 190–400 nm range, which includes specific hydrocarbons, volatile organic compounds, and certain atmospheric pollutants. Accordingly, optical sensors operating in the UV range have the potential to offer fast response times, suitable sensitivity, and minimal cross-reactivity with other substances. − …”