Pyridine derivative-induced fluorescence in multifunctional modified carbon dots and their application in thermometers

We present a simple hydrothermal method to fabricate multifunctional modified carbon dots (with -COOH, -OH, -SH, and -NH2 groups, named NS-Cdots) using citric acid and l-cysteine as raw materials. The functional NS-Cdots exhibit high fluorescent quantum yield (38.9%), low cytotoxicity and good biocompatibility. A reasonable photoluminescence mechanism of the NS-Cdots was proposed in which the pyridine derivatives serve as conjugating units and dominate the main emission behavior. The NS-Cdots can also be used as excellent fluorescent probes for cell imaging in vitro and as effective thermometers with a wide temperature detection range from 20 °C to 95 °C.