Easy and inexpensive method for the visual and electronic detection of oxidants in air by using vinylic films with embedded aniline

Highlights: • Sensory polymeric materials change their colour in presence of oxidant atmospheres. • The sensory materials are films shaped with embedded aniline. • The detection and quantification are based both on optical and electrical methods. • The detection is achieved visually and also using conventional and simple devices. • The presence of oxidants Cl₂ and H₂O₂ in air is detected in the ppb_v range. -- Abstract: Conventional nonconductive vinylic films with dispersed aniline change their color and become conductive in the presence of specific oxidant gases, namely, chlorine and hydrogen peroxide. The color change arises from the polymerization of the aniline to yield the conjugated polymer polyaniline, which at the same time renders the flexible vinylic films conductive. We present a simple and straightforward method using both colorimetric and electrical responses to detect and quantify the presence of oxidants (Cl₂ and H₂O₂) in the air. Using RGB analysis (red, green and blue parameters defining the colors in digital pictures on a computer display) based on different pictures taken with a smartphone of discs extracted from the films and by measuring the UV–vis spectral variation in the presence of different concentrations of Cl₂ and H₂O₂, we obtained limits of detection and quantification between 15 and 200 ppb_v for H₂O₂ and between 37 and 583 ppb_v for Cl₂. Additionally, the electrical response was measured using a fabricated device to visually detect the electrical conductivity activation of the sensor in the presence of oxidant atmospheres, detecting a rapid decrease in resistivity (three orders of magnitude) when the polymerization of aniline began, changing the film from non-conductive to conductive.