Luminescent Silicon Nanocrystals as Metal Ion Sensors

At relatively low concentrations in aqueous solution, Fe³⁺, Fe²⁺, Cu²⁺, and Ni²⁺ 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. Fe³⁺ and Cu²⁺ also significantly increase the PL lifetime. Other metal ions, including Cd²⁺, Mn²⁺, Pb²⁺, Zn²⁺, In³⁺, K⁺, and Ca²⁺, had no effect on the Si nanocrystal PL. The limits of detection (LODs) for Fe³⁺ and Cu²⁺ of 370 and 150 nM, respectively, are low enough for metal ion sensing applications.