Carbon quantum dots modified with hyperbranched polyglycerol for bioapplications: improved photostability and temperature selectivity†

There is a growing demand for technologies to accurately measure intracellular temperatures. Carbon quantum dots (CQDs) are promising candidates due to their unique properties, including high biocompatibility and ease of functionalization, attracting notable attention for applications in intracellular temperature measurements. Nevertheless, CQD-based measurements are susceptible to photobleaching and environmental factors beyond temperature (pH, ion concentration, viscosity, and biomolecules), compromising their accuracy. This study demonstrates that modifying the surface of nitrogen- and sulfur-doped CQDs (N,S-CQDs) with hyperbranched polyglycerol (HPG) mitigates the effects of surface-derived fluorescence, emphasizing core-derived fluorescence, which significantly improves their photostability and robustness against environmental changes. These HPG-modified N,S-CQDs, N,S-CQD-HPG, show reliable and repeatable temperature sensing, making them highly suitable for precise temperature measurements in complex biological environments. These findings highlight the importance of strategic surface modification in developing reliable nanometric temperature sensors for diverse applications.