Carbon dots as smart optical sensors

Of late, carbon dots (CDs) have attracted tremendous attention owing to their excellent and distinctive properties, such as stable and tunable photoluminescence (PL), easy surface functionalization, low toxicity, good biocompatibility, to name a few. After the accidental but groundbreaking discovery in 2004, CDs are prepared using many different carbon precursors, and they present extensive applications in the field of optoelectronic devices, solar cells, sensors, photocatalysis, cellular imaging, etc. In this chapter, we intend to cover the most recent developments of CDs as photoluminescent sensors of various analytes such as important heavy metal ions, toxic food colorant, and trace amount of water contamination in organic solvents, using fluorescence technique. Various other analytical techniques such as dynamic light scattering (DLS), ultraviolet–visible (UV-Vis), x-ray diffraction (XRD), fourier-transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and1H nuclear magnetic resonance (NMR) spectroscopy are also discussed in detail for the characterization study of the prepared CDs. Finally, concluding remarks with some potential development for future uses of CDs are presented.