A CRITICAL COMPARISON OF DIFFERENT SOLID SUPPORTS TO DEVELOP ROOM-TEMPERATURE PHOSPHORESCENCE SENSING PHASES OF AIR MOISTURE

The metal chelates of 8-hydroxy-7-iodo-5-quinolinesulfonic acid (ferro n) with Al(III) exhibit strong room-temperature phosphorescence (RTP) when adsorbed on different solid supports. Moisture is a strong quench er of the solid-surface RTP emitted due to weakening of the bonds betw een the metal chelates and the solid support by water molecules. This effect can be exploited for moisture sensing. Different materials incl uding anion-exchange resins and membranes or xerogel are described her e to immobilize the Al-ferron chelate. The resulting active phases are compared in terms of the intensity of the corresponding RTP emissions and their phosphorescent lifetimes, and the effect of moisture is stu died over a wide range of humidities. Both argon and air gaseous media have been investigated for relative humidity (RH) sensing by RTP-quen ching measurements. Results demonstrate that the nature of the solid s upport plays a critical role in the efficiency of the humidity quenchi ng and so in the RTP sensing response. Air humidity sensing is describ ed in more detail. Anion-exchange resins and membranes require lifetim e measurements for reliable sensing instead of RTP intensity measureme nts. Linear dynamic ranges, however, are wider using anion-exchange re sins or membranes as solid supports of the RTP metal chelates. The sen sing phases prepared using sol-gel techniques show better potential fo r the RTP analytical quantification of humidity in gaseous media in bo th continuous and flow-injection systems. Detection limits observed ar e around 0.09% RH in air, while the precision is +/-3.2% at 8% RH leve ls using the sol-gel active phase in a flow-cell system.