Highly sensitive and selective ratiometric fluorescence and colorimetric detection of Cr(VI) via in situ encapsulation of green/red carbon quantum dots in zeolite

To overcome the limitations arising from non-uniform particle size and solid-state aggregation of carbon quantum dots (CQDs), a novel dual-emissive ratiometric fluorescence probe, GCQDs@SBA-15/RCQDs@SBA-15 (G-RCQDs@SBA-15), has been successfully constructed by simplifying the synthesis process through in situ synthesis of CQDs in SBA-15 to further enhance their optical properties for highly sensitive detection of Cr(VI). The probe G-RCDs@SBA-15, based on green-emission carbon quantum dots (GCQDs) encapsulated in mesoporous molecular sieves SBA-15, provides the response signal, while red-emission carbon quantum dots (RCQDs) encapsulated in SBA-15 serve as an internal reference. The probe exhibits a satisfactory limit of detection (LOD) of 0.336 mu M, which is 52 % lower than GCQDs/RCQDs. Importantly, the probe shows superior selectivity in detecting Cr(VI) compared to other metal ions. The fluorescence signal ratio of the probe decreases with increasing Cr(VI) concentration, resulting in a distinct change of fluorescence color from green to red. Based on UV-vis and fluorescence lifetime analysis, Inner filter effect (IFE) is considered the primary potential mechanism for the fluorescence color transition of G-RCDs@SBA-15 following the addition of Cr(VI). G-RCQDs@SBA-15 not only inherits the excellent optical properties of GCQDs and RCQDs but also shows high fluorescence and chemical stability. Considering the sensitive photoconversion properties of G-RCQDs@SBA-15, a smartphone