A highly sensitive carbon quantum dots sensor for hypochlorite ion detection through fluorescence-off method

Hypochlorite ions have a key role in the biological immune system. As soon as the body detects an attack by bacteria or viruses, it produces, by some complex reaction mechanism, hypochlorite ions (ClO^-). These ions are very powerful oxidizing agents and can kill bacteria or viruses by digesting their (virus, bacteria) constituent proteins or other biomolecules. Due to this, detection of hypochlorite ions is very important. Here we have synthesized Cu-doped CQDs from succinic acid and cupric acetate through a simple aqueous reflux method at 90 °C. The prepared CQD showed good fluorescence properties (quantum yield (QY) ∼31.33%). Hypochlorite ions quenched the emission intensity of the CQD, exclusively. The probe was good enough to detect a very low concentration of the hypochlorite ions, as low as 5.76 nM. Synthesized CQDs can be used to sense hypochlorite ions in real water samples also. The linear range of the detection was 0-400 nM. The prepared CQDs have been characterized by UV-vis spectrophotometer, fluorimeter, FT-IR (Fourier transform infrared spectroscopy), Dynamic Light Scattering, XRD (X-ray Diffraction) and TEM (transmission electron microscopy), EDX, and TCSPC. From the TEM images it is clear that the CQDs are spherical. We measured their diameters to be in the range 2-5 nm.