Carbon Nanodots-Catalyzed Chemiluminescence of Luminol: A Singlet Oxygen-Induced Mechanism

The catalyzed luminol chemiluminescence (CL) in a strongly alkaline environment has been rarely induced by singlet oxygen (1O2). This paper reports that cetyltrimethyl ammonium bromide passivated carbon nanodots (CTAB-CDs), prepared by the hydrothermal treatment of fullerene in the presence of CTAB, can be used as excellent catalysts to dramatically enhance the CL intensity of the luminol–H2O2 system in NaOH medium owing to their unique surface property. More importantly, this CL enhancement takes place mainly through the intermediate of 1O2, which follows a different mechanism from traditional reports. The CL spectra, UV–vis spectra, electron paramagnetic resonance (EPR) spectra, transmission electron microscopy (TEM) images before and after the CL reaction, and the effects of various free radical scavengers on the CL intensity were conducted to identify the possible 1O2-participating CL enhancement mechanism. It was demonstrated that the CL enhancement by CTAB-CDs originated from the processes of the catalysis of CDs on the electron-transfer and the breakdown of H2O2. Both processes produced a great amount of 1O2 on the surface of CTAB-CDs, and then the reaction of 1O2 with luminol resulted in an unstable endoperoxide, which could rapidly decompose into the excited state 3-aminophthalate anions (3-APA*), leading to the enhanced CL at 440 nm. The important features of this CDs-catalyzed CL will not only enrich traditional luminol CL mechanism in strongly alkaline conditions but also open up a new route to study this novel carbon nanomaterial, which may broaden the applications in a large variety of fields.