A facile large-scale microwave synthesis of highly fluorescent carbon dots from benzenediol isomers

A fast large-scale synthesis of fluorescent carbon dots (CDs) has been developed in this work without high temperature or high pressure. Using benzenediols (catechol, resorcinol and hydroquinone) as the carbon precursor and sulfuric acid as the catalyst, three distinct CDs with strong and stable luminescence were prepared via a microwave-assisted method within 2 min. Characterizations through high-resolution transmission electron microscopy, X-ray diffraction, elemental analysis and infrared spectroscopy indicated the as-prepared CDs are dispersed spherical oxygenous carbon nanoparticles with 0.5-6 nm sizes. The structure differences caused by the isomer precursors were reflected in the chemical and fluorescent properties of CDs. The quantum yields of the three kinds of CDs derived from catechol, resorcinol and hydroquinone are 9.2%, 42.8% and 26.5%, respectively, and the fluorescence lifetimes of these CDs are on the nanosecond scale. The CDs derived from hydroquinone could easily penetrate into cells in a short time (30 min) and possess low cytotoxicity and good biocompatibility which may have great potential for bioimaging applications.