Synthesis and properties of carbon quantum dots from flue ash of biomass

Carbon quantum dots (CQDs) with a good water solubility and stability were produced from cheap and easy available flue ash produced by burning straw and wood by refluxing it in an acid mixture (HNO₃:H₂SO₄=1:3 v/v). They were characterized by XRD, HRTEM, FTIR, XPS and Raman spectroscopy. Results indicate that the CQDs are spherical particles whose cores are less than 1 nm across and are poorly crystallized with a large number of defects. The CQDs emit yellow light with emission wavelengths over 500 nm and their fluorescence quantum yield is as high as 3.83%. They are of potential use in a variety of fields such as bioimaging.