Temperature triggered high-performance carbon dots with robust solvatochromic effect and self-quenching-resistant deep red solid state fluorescence for specific lipid droplet imaging

Developing high-performance carbon dots (CDs) with new structure and establishing the linkage with synthetic conditions remain challenging. In this work, we develop a simple one-pot solvothermal strategy to synthesize high-performance CDs by rationally controlling carbonized core and polymer structure. The obtained CDs not only show robust solvatochromic effect with emission shift up to ~132 nm from green to far-red region meanwhile accompanied with quantum yield (QY) decreasing from 73 to 1% as solvent polarity increase, but also possess rare deep red self-quenching-resistant solid state fluorescence (λem = 660 nm). Extensive characterizations reveal that the thermal-triggered unique polymer features composed of carbonized core and the shell of intertwined polymer chains account for the unprecedented photophysical behaviors. Moreover, the CDs display ultrabright yellow emission in oil media (QY up to 51.6%) with an impressive fluorescence enhancement up to 140-fold compared to aqueous media, making them an efficient probe for specifically staining lipid droplets (LDs). In contrast with commercially LDs marker BODIPY 493/503, the CDs-based probe can provide long emission, large Stokes shifts (>100 nm), superior photostability, and especially overcome aggregation-caused-quenching. Consequently, the CDs-based marker successfully achieves real-time monitoring of LDs-related physiological process in living cells, diagnosing fatty liver and visualizing lipid-rich tissues in zebrafish. We believe the developed CDs-based LDs probe is more competitive against organic dyes due to their high efficiency, simple one-pot preparation and low-cost.