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.