Catalyzed Microwave-Assisted Preparation of Carbon Quantum Dots from Lignocellulosic Residues

A lignocellulosic residue from the pulp and paper industry (primary sludge) was employed to obtain carbon-based fluorescent nanomaterials. The unprecedented preparation of the carbon quantum dots (CQDs) was carried out using a microwave-assisted reaction catalyzed by a solid acid catalyst, which induced the formation of CQDs. The obtained CDQs were fully characterized using a number of analytical techniques. HR-TEM images depicted particle sizes of average diameter value of 17.5 nm. UV–visible spectra displayed a characteristic peak at 325 nm associated with the formation of CQDs. Fluorescence measurements recorded at 360 nm (excitation wavelength) exhibited an emission band at ca. 435 nm. This emission signal turned out to be dependent on the excitation wavelength that further confirmed the presence of CQDs.