Surfactant-mediated enhanced FRET from a quantum-dot complex for ratiometric sensing of food colorants

Herein we report that a surfactant modified quantum dot-complex (S-QDC; with λ_em-515 nm) nanocomposite, as a donor fluorophore, exhibits enhanced Förster resonance energy transfer (FRET) efficiency to an acceptor organic dye (λ_em-576 nm) in comparison to only the QDC. The proposed S-QDC (consisting of a ZnS quantum dot, zinc quinolate inorganic complex and cetyltrimethylammonium bromide (CTAB) surfactant) provides the unique and selective ratiometric visual detection of organic dyes present as food colorants in commercial chili powder, tomato ketchup and mixed fruit jam. Notably, the S-QDC shows a limit of detection (LOD) as low as 2.2 nM in the linear range of 0.17-4.89 μM for food colorants. Furthermore, the present work will bring new possibilities to unravelling the chemistry among surfactants, inorganic complexes and quantum dots to make newer optical materials with futuristic scope of utilization ranging from optical sensors to light emitting devices.