Fluorescence Quenching by Metal, Semiconductor and Insulator Surfaces.

Distance-dependence of fluorescent intensity emitted by Eu('3+) ions of europium (III) thenoyltrifluoroacetonate located on metal, semiconductor and insulator surfaces has been studied. On the basis of the classicial energy flux method and conservation of energy a many-dipole model was established and a measurable quantity i.e., apparent quantum yield q(,a) was derived. Comparison between the experiment and the theory shows that the distance-dependence of fluorescent intensity can be qualitatively explained by classical electromagnetic theory and that the fluorescent intensity varies roughly as one over distance squared. At short distances fluorescence quenching is strong for almost all materials, even the transparent conductors commonly used in commercial electroluminescent displays. For example, an emitting center within 20 (ANGSTROM) of an In(,2)O(,3) surface will be quenched to below 1% of its normal fluorescence.