Fluorescent Sensor Based on BINOL for Recognition of Cysteine, Homocysteine, and Glutathione

A new and simple fluorescent sensor based on unmodified BINOL was developed. The fluorescence of BINOL could be turned off with high selectivity toward Cu­(II) among 27 metal ions. Meanwhile, it was found that BINOL was oxidized to dibenzo­[<i>a</i>,<i>kl</i>]­xanthen-1-ol (<b>A</b>) by Cu­(NO₃)₂. A new peak appeared at ∼482 nm upon addition of thiol-containing cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Thus, a cascade recognition of Cu­(II) and Cys, Hcy, and GSH are well presented