and L.sup.3 do not conjugate S and D.According to a preferred embodiment of the present invention, S is selected from merocyanine dyes, cyanine dyes, acridine dyes, multi nucleus aromatic compounds, xanthene dyes, coumarin dyes and hetero aromatic compounds.In another preferred embodiment of the present invention, S is a compound of the following formula:In formula (III), R is a substituted or un