Polarity-sensitive dual emissive fluorescent carbon dots as highly specific targeting probes for lipid droplets in live cells

Polarity-sensitive fluorescent nanoparticles with intrinsic dual emission are invaluable tools for investigating microenvironmental polarity. Ratiometric fluorescent sensors, with their built-in self-calibration characteristics, offer higher sensitivity and more obvious visual detection in qualitative and quantitative analysis. In this context, we report the synthesis of polarity-sensitive, dual-emitting carbon dots <i>via</i> a solvothermal method and demonstrate their application in ratiometric polarity sensing. These carbon dots exhibit characteristic solvatochromic effects with emissions in both the blue and red spectral regions. Notably, we observed a remarkable 30-fold enhancement in the red-to-blue emission intensity ratio as the solvent polarity shifted from 0.245 to 0.318. The dual-emitting carbon dots demonstrate the highly sensitive and inherently reliable (self-calibration) polarity dependence of the emission spectra, facilitating their application in ratiometric polarity sensing. These dual-emitting carbon dots exhibited a strong affinity for lipid droplets in live cells, demonstrating their potential as highly specific targeting probes for imaging lipid droplets in live cells, without the need for additional targeting ligands. The characteristics of excellent biocompatibility, photostability, and good cellular imaging capabilities make these dual-emitting carbon dots highly promising for biomedical and sensing applications.