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Anal Chem. 2014 May 6;86(9):4528-35. doi: 10.1021/ac5005162. Epub 2014 Apr 14.

Carbon nitride quantum dots: a novel chemiluminescence system for selective detection of free chlorine in water.

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Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.


A facile one-step microwave-assisted approach for the preparation of strong fluorescent carbon nitride quantum dots (g-CNQDs) by using guanidine hydrochloride and EDTA as the precursors was developed. Strong chemiluminescence (CL) emission was observed when NaClO was injected into the prepared g-CNQDs, and a novel CL system for direct detection of free chlorine was established. Free residual chlorine in water was sensitively detected with a detection limit of 0.01 μM and had a very wide detection range of 0.02 to 10 μM. On the basis of CL spectral, UV-visible absorption spectral, and electron spin resonance (ESR) spectral studies, as well as investigations on the effects of various free radical scavengers, a possible CL mechanism was proposed. It was suggested that the radiative recombination of oxidant-injected holes and electrons in the g-CNQDs accounted for the CL emission. Meanwhile, (1)O2 on the surface of g-CNQDs, generated from some reactive oxygen species in the g-CNQDs-NaClO system, could transfer energy to g-CNQDs and thus further enhance the CL emission. The CL system is highly sensitive and differentiable, opening a new field for the development of novel CL-emitting species, but also expanding the conventional optical utilizations of g-CNQDs.

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