Luminescence from excited tris(2,2′-bipyridine)-ruthenium(II) incorporated into a silk fibroin membrane

Abstract

Luminescence from the excited state of Ru(bpy) 3 2+ (bpy, 2,2′-bipyridine) incorporated into a silk fibroin membrane was studied. The emission lifetime of the ruthenium complex incorporated into a silk fibroin membrane was longer (1700 ns) than the value (598 ns) in aqueous solution, suggesting the presence of a rigid binding site for the complex, probably composed of tyrosine residues. The mobility of the tyrosine residue was studied by electron spin resonance spectroscopy of a spin-labelled silk fibroin membrane. Quenching of the emission from the ruthenium complex/silk membrane by oxygen in the water phase was demonstrated. The emission intensity and lifetime were dependent on the humidity of the membrane. The emission is discussed in comparison with emission from other matrices such as a Nafion membrane.