Polyamine-functionalized carbon quantum dots for chemical sensing

Polyamine-functionalized carbon quantum dots (CQDs) with high fluorescence quantum yield (42.5%) have been synthesized by the low temperature (<200   °C) carbonization of citric acid with branched polyethylenimine (BPEI) in one simple step. The obtained BPEI–CQDs are spherical graphite nanocrystals (average 6.2   nm in size) capped with abundant BPEI at their surfaces. It is the first report that CQDs are both amino-functionalized and highly fluorescent, which suggests their promising applications in chemical sensing.