Screen-Printed Sensors for Colorimetric Detection of Hydrogen Sulfide in Ambient Air

A fast and sensitive method to monitor hydrogen sulfide (H₂S) in ambient air based on a visible color change of a printed disposable sensor has been developed. As gas-sensitive material, an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphtol (H-PAN) was synthesized and prepared in an ethyl cellulose matrix for screen printing. If H₂S is present in ambient air, the gas sensitive layer changes its color from purple to yellow. A pre-primed polyethylene (PE) foil and a coated offset paper served as the printing substrate. The colorimetric response to the target gas was measured by UV/Vis spectroscopy in reflection at H₂S concentrations between 1 to 20 ppm. Possible cross-sensitivities of the printed sensors towards methane (CH₄), formaldehyde (CH₂O), carbon monoxide (CO), ammonia (NH₃), and nitrogen dioxide (NO₂), as well as the long-term stability was investigated. Furthermore, reflection measurements of the Cu-PAN complex on an amorphous silica powder under gas admission served as preliminary test for the subsequent paste development.