Luminescent Silicon Nanocrystals as Metal Ion Sensors.

At relatively low concentrations in aqueous solution, Fe 3+ , Fe 2+ , Cu 2+ , and Ni 2+ quench the photoluminescence (PL) of the undecenoic acid-capped silicon (Si) nanocrystals. The PL could be restored by adding a chelating agent, such as ethylenediaminetetraacetic acid (EDTA), to remove the ions. Fe 3+ and Cu 2+ also significantly increase the PL lifetime. Other metal ions, including Cd 2+ , Mn 2+ , Pb 2+ , Zn 2+ , In 3+ , K + , and Ca 2+ , had no effect on the Si nanocrystal PL. The limits of detection (LODs) for Fe 3+ and Cu 2+ of 370 and 150 nM, respectively, are low enough for metal ion sensing applications.