Real-Time Monitoring of Low Pressure Oxygen Molecules over Wide Temperature Range: Feasibility of Ultrathin Hybrid Films of Iridium(III) Complexes and Clay Nanosheets

An ultrathin film was prepared by hybridizing a cationic Ir(III) complex with exfoliated nanosheets of clay minerals such as natural montmorillonite (denoted by MON) or synthetic saponite (denoted by SAP). The utilized Ir(III) complex with two long alkyl chains was [Ir(dfppy)(2)(dc9bpy)](+) (fppyH = 2-(2',4'-difluorophenyl)pyridine; dc9bpy = 4,4'-dinonyl-2,2'-bipyridine) (denoted by DFPPY). Hybridization was performed at an air-water interface between a floating monolayer of the Ir(III) complex and the nanosheets exfoliated in an aqueous subphase. The hybrid floating film thus formed was transferred onto a hydrophilic quartz plate by a vertical dipping method. The emission from the deposited films exhibited rapid reversible change of intensity in response to the introduction or evacuation of oxygen gas in the pressure range of 0.1-101.3 kPa and the temperature range from 253 K to 313 K. The lifetime of the emission decay was measured as a function of oxygen pressure, confirming the occurrence of dynamic quenching of excited Ir(III) complexes by oxygen molecules.