A new 1,8-naphthalimide-based colorimetric and "turn-on" fluorescent Hg2+ sensor

A new fluorescent molecule 4-(bis(2-(ethylthio)ethyl)amino)-N-n-butyl-1,8-naphthalimide (BTABN) was reported. Its UV-vis absorption and fluorescence spectra were almost not dependent on the pH, but remarkably and selectively affected by Hg(2+). Upon the addition of Hg(2+) in EtOH/H(2)O (1/2,v/v), the absorption wavelength maxima were blueshifted from 436 nm to 376 nm with a naked-eye observed color change, and the fluorescence was greatly enhanced with a 14 nm blueshift within 1 min. Na(+), K(+), Ca(2+), Mg(2+), Cu(2+), Zn(2+), Cr(3+), Pb(2+), Ni(2+), Fe(2+), Mn(2+), Co(2+), Cd(2+) showed no obvious interferences with the detection. The binding stoichiometry indicates that a 1:1 complex is formed between Hg(2+) and BTABN. The response of the UV-vis absorption and the fluorescence spectra to Hg(2+) can be attributed to the joint contribution of the PET and ICT process.