Highly fluorescent carbon dots from quinoline insoluble residues in coal tar

Abstract Coal is the most abundant and affordable carbonaceous material. However, to use as a combustible energy resource material coal to coke conversion is necessary and during the conversion, coal tar is produced. In this coal tar, Quinoline Insoluble (QI) residues are found as a solid carbon particle. Till date, the utility of the QI particles is very limited. Different spectroscopic characterizations show that QI particles are easy to oxidize and we have successfully synthesized highly fluorescent carbon dots (CDs) from the QI particles using different oxidizing agents. The fluorescent properties of CDs are strongly depended on the degree of oxidation as well as their size. The emission wavelengths, quantum yield can be tuned by changing the oxidizing agents. Further, the excited state lifetime is also determined and the average lifetime of the CD is in nano-seconds region. Therefore, it can be utilized for different optoelectronic and biological imaging applications. Thus, the simple strategy can provide an easy route to bulk scale commercial synthesis of CD materials as its precursor materials are cheap and easily available.