Discriminating between Different Heavy Metal Ions with Fullerene-Derived Nanoparticles

A novel type of graphene-like nanoparticle, synthesized by oxidation and unfolding of C(60) buckminsterfullerene fullerene, showed multiple and reproducible sensitivity to Cu(2+), Pb(2+), Cd(2+), and As(III) through different degrees of fluorescence quenching or, in the case of Cd(2+), through a remarkable fluorescence enhancement. Most importantly, only for Cu(2+) and Pb(2+), the fluorescence intensity variations came with distinct modifications of the optical absorption spectrum. Time-resolved fluorescence study confirmed that the common origin of these diverse behaviors lies in complexation of the metal ions by fullerene-derived carbon layers, even though further studies are required for a complete explanation of the involved processes. Nonetheless, the different response of fluorescence and optical absorbance towards distinct cationic species makes it possible to discriminate between the presence of Cu(2+), Pb(2+), Cd(2+), and As(III), through two simple optical measurements. To this end, the use of a three-dimensional calibration plot is discussed. This property makes fullerene-derived nanoparticles a promising material in view of the implementation of a selective, colorimetric/fluorescent detection system.