Abstract
Sensitive and selective personal exposure monitors are needed to assess ozone (O3) concentrations in the workplace atmosphere in real time for the analysis and prevention of health risks. Here, a cumulative gas sensor using visible spectroscopy for real-time O3 determination is described. The sensing chip is a mesoporous silica thin film deposited on transparent glass and impregnated with methylene blue (MB). The sensor is reproducible, stable for at least 50 days, sensitive to 10 ppb O3 (one-tenth of the occupational exposure limit value in France, Swiss, Canada, U.K., Japan, and the USA) with a measurement range tested up to 500 ppb, and insensitive to NO2 and to large variation in relative humidity. A model and its derivative as a function of time are proposed to convert in real time the sensor response to concentrations, and an excellent correlation was obtained between those data and reference O3 concentrations. This sensor is based on a relatively cheap sensing material and a robust detection system, and its analytical performance makes it suitable for monitoring real-time O3 concentrations in workplaces to promote a safer environment for workers.
Highlights
Ozone (O3 ) is a powerful oxidizing gas and a strong disinfectant used in different processes, including water treatment, gas purification, textile bleaching, and food industries
The visible spectra of methylene blue adsorbed in mesoporous silica show two characteristic absorption peaks of MB at 620 and 665 nm (Figure 3A), similar to the literature [38]
When the relative humidity was varied between 2% and 77%, a significant decrease in absorbance was observed at these two wavelengths (Figure 3A), in agreement with previous reports [46]
Summary
Ozone (O3 ) is a powerful oxidizing gas and a strong disinfectant used in different processes, including water treatment, gas purification, textile bleaching, and food industries. O3 is mainly emitted into the atmosphere from the processes of UV radiation and electric arc welding [1]. Another source of exposure in tertiary and service sectors is the extensive use of laser printers and photocopiers [2]. In France, the occupational exposure limits values (OELs) for O3 exposure are 100 ppb and 200 ppb for exposure times of 8 h and 15 min, respectively [3]. These values are consistent with other European or international OELs (see Table S1 in Supporting Information).
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