Preparation of boron-doped carbon dots for fluorometric determination of Pb(II), Cu(II) and pyrophosphate ions

The authors report on the synthesis of boron-doped carbon nanodots (B-C-dots) by a hydrothermal method using ascorbic acid and boric acid as the precursors. The dots have an irregular shape with a typical diameter of 10 nm and display strong fluorescence, with excitation/emission maxima of 350/440 nm. Fluorescence is quenched by Cu(II) and Pb(II) ions due to the formation of nonfluorescent metal complexes between chelating oxygen atoms on the surface of the dots. The findings were used to design a fluorometric method for the determination of the two ions. Linear relationships exist between the drop in fluorescence intensity and the concentrations of Cu(II) and Pb(II) ions in the range from 50 nM to 300 μM and from 25 nM to 250 μM, respectively. The fluorescence of the Cu(II)-quenched B-C-dots is restored in addition of pyrophosphate (PPi) as a result of coordination/chelation interactions between these ions and PPi. This was exploited to develop an assay for PPi that works in the of 25 to 500 μM PPi concentration range.