Hydrothermal synthesis of fluorescent carbon dots from sodium citrate and polyacrylamide and their highly selective detection of lead and pyrophosphate

Fluorescent carbon dots (CDs) have been a promising star in analytical and environmental fields. Present study designed a new bright-blue fluorescent carbon dots with sodium citrate and polyacrylamide by a hydrothermal method. The obtained CDs had an average diameter of 2.4 nm and exhibited excitation-independent property. The experimental results demonstrated that the bright-blue fluorescent CDs exhibited “off-on” property with Pb2+ and pyrophosphate (PPi), which proved that it was a good fluorescent probe for the determination of Pb2+ and PPi. The fluorescence intensity of CDs was significantly quenched by Pb2+ (turn-off) through forming CDs/Pb2+ complexes via an inner filter effect, and the fluorescence intensity of CDs/Pb2+ system was completely resumed by PPi (turn-on) owing to the release of CDs from the CDs/Pb2+ complexes due to higher binding force of PPi to Pb2+. The detection limits were 4.6 nM for Pb2+ and 54 nM for PPi, respectively. The probe was successfully validated with real water samples and human urine. The results showed that this the probe was facile, rapid and exhibited high sensitivity, selectivity, repeatability and stability. This “off-on” fluorescent probe based on CDs provided a promising platform for environmental and biological sensing applications.