An “on–off–on” fluorescence assay based on silicon nanoparticles for selective detection of manganese(II)

Highly blue luminescent and water-soluble silicon nanoparticles (Si NPs) are prepared by an efficient one-pot hydrothermal route from (3-aminopropyl) trimethoxysilane and ascorbic acid at 160 degrees C. The label-free Si NPs are demonstrated as an effective fluorescent probe for selective recognition of Mn2+. The linear range is from 2.5 to 250 mu M and the detection limit is calculated to be 1.1 mu M due to Mn2+ induced Si NP aggregation (turn-off). Additionally, the quenched fluorescence can be restored in the presence of EDTA because the EDTA can grab Mn2+ from the aggregated Si NPs-Mn2+ system owing to its strong chelating ability (turn-on). This sensing system based on the "on-off-on" fluorescence switching method can facilitate further development in Mn2+ detection.