Air moisture sensing materials based on the room temperature phosphorescence quenching of immobilized mercurochrome Original Research Article

2′,7′-Dibromo-5′-[hydroxymercuri]fluorescein (mercurochrome) exhibits intense long-decay room-temperature phosphorescence (RTP) in ambient air when immobilized on solid supports. Luminescence from these materials is very sensitive to the humidity (water) content in air streams. In this paper, air moisture optically active phases based on the RTP quenching of immobilized mercurochrome (retained on a Dowex 1X2-200 organic polymeric resin or trapped in a inorganic matrix prepared by using sol–gel technology) have been characterized. Experiments on the quenching of the luminescence of such active phases, over a wide range of relative humidities are discussed. The developed RTP optical sensing materials have been investigated in terms of intensity of the RTP emission and of their phosphorescence lifetime changes as a function of humidity levels in air. Results demonstrated that the nature of the solid support and the immobilization procedure play a critical role in the RTP signals from the immobilized mercurochrome and also in the efficiency of the RTP quenching by moisture and so in the RTP sensing response. Air humidity sensing is described in detail. The solid sensing material prepared using sol–gel technology showed better potential for RTP analytical quantification of air relative humidity (RH). A detection limit (3 × background) of 0.11% of RH in air was found and relative standard deviation values of ca. 4.4% (n = 5, at a 8% RH level) were achieved.