Fluorescent nanoparticles as selective Cu(II) sensors

Latex nanoparticles functionalized with cyclam (1,4,8,11-tetraazacyclotetradecane), a copper chelator, have been doped with a fluorescent dye 1 (BODIPY derivative: 4,4-difluoro-8-(2,4,6-trimethyl)phenyl- 2,6-diethyl-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene). The bulky, hydrophobic fluorophore 1 dissolves within the nanoparticles' polymer core up to a concentration of about 88.4 lmol g-1. At this concentration the fluorescence yield is about 0.80. Adding Cu2+ ions to the solution decreases the fluorescence because of the energy transfer between the dye and the violet copper cyclam complexes. The response is fast: 90% of the quenching occurs within 1 s. The Cu2+ detection threshold is of 1 nanomolar. No interferences were observed with zinc and nickel ions.