Polymer films containing chemically anchored diazonium salts with long-term stability as colorimetric sensors.

•Film shaped sensory polymeric materials change their color in presence of phenols.•The polymers main chains have pendant diazonium moieties.•The sensory materials are manageable and stable along time.•The detection is achieved visually and also using pictures taken with smartphones.•The limits of detection were of the order of ppb.