Microwave-assisted green synthesis of asphaltene-based carbon dots for micelle sensitized fluorescent probes

Development of inexpensive and environmentally friendly chemical sensors can help improve the global ecological environment and reduce pollutant emissions. In this work, asphaltene of coal liquefaction by-product was employed as the carbon source to fabricate carbon dots (CDs) by straightforward microwave radiation. The asphaltene-based CDs gave out blue emission under UV light excitation. Interestingly, the CDs are highly lipophilic because of its carbonized structure and insufficient hydrophilic groups. Based on these findings, an outstanding fluorescent sensor for 2,4,6-trinitrophenol (TNP) was developed by loading asphaltene-based CDs into polymeric micelles. The micelle formed by nonionic tri-block copolymers exhibited a hydrophobic inner cavity and hydrophilic surface. Due to the protection of the micelles, the emission of asphaltene-based CDs was enhanced by 2.89 times. But the fluorescence was significantly quenched by TNP through energy transfer and electron transfer mechanism, showing high sensitivity to TNP with a detection limit of 0.21 μM. The findings presented here provide a green method to synthesize fluorescent CDs and a promising strategy to design fluorescent probes. Graphical abstract