One-step synthesis of amine-functionalized fluorescent silicon nanoparticles for copper(II) ion detection

Amine-functionalized silicon nanoparticles (A-SiNPs) with intense green fluorescence and photostability are synthesized via a one-step, low-cost hydrothermal method under mild conditions using 3-aminopropyl triethoxysilane (APTES) as a silicon source and L-ascorbic acid (AA) as a reducing reagent. The amine-rich surface not only improves water dispersability and stability of the A-SiNPs but also offers a specific copper(II) ion (Cu²⁺) coordination capability. The as-prepared A-SiNPs can be directly employed for Cu²⁺ detection in "turn-off" mode, resulting from Cu²⁺ coordination-induced fluorescence quenching effect. Under optimal conditions, Cu²⁺ detection was accomplished with a linear range from 1 to 500 μM and a limit of detection (LOD) at 0.1 μM, which was much lower than the maximum level (~ 20 μM) of Cu²⁺ in drinking water permitted by the US Environmental Protection Agency (EPA). In addition, the A-SiNPs were successfully used to detect Cu²⁺ in spiked river water, demonstrating its good selectivity and potential application for analysis of surface water samples. Graphical abstract.