A Water-Soluble Luminescence Oxygen Sensor

We developed a water-soluble luminescent probe for dissolved oxygen. This probe is based on (Rudpp(SO₃Na)₂]₃) Cl₂, which is a sulfonated analogue of the well-known oxygen probe (Rudpp]₃)Cl₂. The compound dpp is 4,7-diphenyl-1,10-phenanthroline and dpp(SO₃Na)₂ is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Rudpp(SO₃Na)₂]₃)Cl₂ displays a lifetime of 3.7 μs that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern–Vohner quenching constant is 11330 M^?1. This high oxygen-quenching constant means that the photoluminescence of Ru(dppSO₃Na]₂)₃Cl₂ is 10% quenched at an oxygen concentration of 8.8 x 10^?6 M , or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl-L-α-phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes'shift allow this probe to be used with simple instrumentation based on a light-emitting diode light source, allowing low-cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water-soluble oxygen sensor.