Chemiluminescence from NaClO–H2O2 and enhanced by l-cysteine capped Mn-doped ZnS quantum-dots

Water-soluble l-cysteine capped Mn-doped ZnS@Si quantum-dots (QDs), a kind of sensitizer, were synthesized. It was found that this sensitizer could enhance chemiluminescence (CL) signals emitted from interaction of NaClO with H2O2 in basic medium. The CL mechanism was studied experimentally by singlet oxygen (1O2) quenching method, UV–vis spectra, X-ray photoelectron spectra, transmission electron microscopy studies and ESR spin-trapping spectra. The results demonstrated that the CL enhancement of NaClO–H2O2 originate from the catalysis of the sensitizer, which catalyzed the decomposition of H2O2, producing reactive intermediates hydroxyl radical (radical dotOH) and superoxide anion (O2radical dot−). Then the resulting radical dotOH reacted with O2radical dot− to form 1O2 and oxygen excimer species (1O2)2⁎, which rapidly returned to its ground state by passing its energy to the sensitizer through an electron-transfer process. Finally, the sensitizer being in excited state, returned to the ground state through enhanced CL-emission.