Hydrocarbon in water sensing with PTFE membranes doped with a luminescent Ru(ii) poly(pyridyl) complex

Abstract

A novel luminescent material for hydrocarbon-in-water sensing has been developed. The reagent layer contains the hydrophobic probe tris(4,4′-dinonyl-2,2′-bipyridine)ruthenium(II) dichloride embedded in a poly(tetrafluoroethylene) matrix. The electronic absorption (459 < λ^abs_max < 466 nm) and emission features (601 < λ^em_max < 617 nm; 452 < τ < 755 ns in deaerated solution) of the engineered indicator dye have been measured in various solvents of very different polarity. The simple Lippert model accounts for medium effects, demonstrating that specific solvent–solute interactions are negligible. The sensitive terminal is interrogated, via optical fibres, with an optoelectronic system based on sinusoidally modulated LED excitation and phase-sensitive detection of the luminescence for the most stable response. The optosensor responds reversibly to both aromatic and aliphatic hydrocarbons in the 5–1500 mg L⁻¹, with response times on the order of 10 min for the most favourable conditions. The effect of a number of factors on the luminescent material response has been investigated, namely the dye loading, excitation modulation frequency, sample temperature, dissolved oxygen, hydrocarbon type and potential interfering compounds. Such material enables another use of modern optosensing instrumentation for dissolved oxygen monitoring.