Polymeric carbon dot/boehmite nanocomposite made portable sensing device (Kavach) for non-invasive and selective detection of Cr(VI) in wastewater and living cells

This work reports a handheld fluorometric probe, namely ‘Kavach’ for monitoring hexavalent chromium in industrial wastewater and living systems. Kavach is capable to detect chromium contamination in a rapid and facile way. The device is made of a thin layer (~1 mm) of carbon dot decorated boehmite nanostructure (BH@CD) incorporated in a layer of poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membrane. The doped membrane has an excellent blue fluorescence upon UV excitation (355 nm) and alters its fluorescence level when exposed to Cr(VI). In reality, tiny carbon dots leach out from the nano-matrices to produce secondary contamination. Incorporation of the BH@CD into the polymeric matrix of PVDF-HFP significantly reduces such contamination and makes this material a potential sensing probe. This photoinduced electron transfer (PET) based sensor is tremendously selective and sensitive (LOD ~66 nM) towards aqueous chromium. The performance of the probe remains unaltered in different pH and water qualities. Additionally, this material can sense chromium in living cells, which has been validated theoretically using molecular docking and observed experimentally using fluorescence microscopy. Kavach is truly a handheld, reusable and non-invasive sensing probe against Cr(VI), which can be employed for on-site low-cost detection.