Green fluorescent carbon dots functionalized MoO3 nanoparticles for sensing of hypochlorite

In this study, three different colored blue (B-), green (G-) and yellow (Y-) fluorescent carbon dots (CDs) were synthesized by using natural precursor Annona squamosa fruit via acid oxidation method. The as-synthesized B-, G- and Y-CDs displayed intense emission peaks at 445, 514 and 558 nm upon the excitations at 360, 420 and 440 nm, respectively. The functionalization of molybdenum oxide nanoparticles (MoO3 NPs) with three color emissive CDs allows well dispersability in aqueous media and converts the non-fluorescent nature of MoO3 NPs to blue, green and yellow color emissions, which is beneficial for the sensitive assay of hypochlorite (ClO-). It was found that the emission intensity of G-CDs functionalized MoO3 NPs at 516 nm was remarkably quenched by ClO-, whereas ClO- showed least quenching ability towards blue- and yellow- MoO3 NPs. Based on these observations, MoO3 NPs-G-CDs showed a linear fluorescence quenching at 516 nm in the range of 0.010–200 µM with detection limit of 6.8 nM for ClO-. The developed optical sensor affords good selectivity for the detection of ClO- in water samples with good recoveries, which demonstrates great promise of MoO3 NPs-G-CDs in assaying ClO- in complex samples at minimal volume of samples.