Four fluorescent sensors designed for Zn(II) detection that contain a fluorescein reporting group and a pyridylamine-thioether derivatized ligand moiety were prepared and their photophysical properties characterized. These "Zinspy" sensors are water soluble and generally display similar to1.4- to similar to4.5-fold fluorescence enhancement upon Zn(II) coordination, depending upon fluorescein halogenation and the number and nature of the zinc-binding appendages. The Zinspy sensors exhibit improved selectivity for zinc compared to the di-(2-picolyl)amine-based Zinpyr family.