Polymer-Supported pH Sensors Based on Hydrophobically Bound Luminescent Ruthenium(II) Complexes

A new luminescence intensity-based sensor-polymer support system is described. The pH-sensitive element is [Ru(phen) 2 [phen(OH) 2 ]] 2+ or [Ru(Ph 2 phen) 2 [phen(OH) 2 ]] 2+ (phen = 1,10-phenanthroline, Ph 2 phen = 4,7-diphenyl-1,10-phenanthroline, and phen(OH) 2 = 4,7-dihydroxy-1,10-phenanthroline) immobilized on a polymer built from a four-function cyclic methyl siloxane ring polymer having (SiRCH 3 O) 4 units with poly(ethylene oxide) cross-linkers. Hydrophobic binding of the sensor to the polymer is used to avoid the need for covalent chemistry. These sensor systems have a usable sensitivity over the 2−8 pH range, but are most usable in the 2−6 pH range. Response times for thick films (250 μM) are rapid (several minutes).