Molecular mechanism for the unusual enhancement of the second-step chemiluminescence production from the carcinogenic tetrabromohydroquinone and H 2 O 2 .

We have found recently that two-step intrinsic hydroxyl radical ( ^· OH)-dependent chemiluminescence (CL) could be produced by carcinogenic tetrahaloquinone and H ₂ O ₂ . However, the first-step CL was too fast to clearly detect the stepwise generation of ^· OH and CL, and to distinguish the exact dividing point between the first-step and second-step CL. Here we found that, extremely clear two-step intrinsic CL could be produced by the relative slow reaction of tetrabromohydroquinone (TBHQ) with H ₂ O ₂ , which was directly dependent on the two-step ^· OH generation. Interestingly, the second-step, but not the first-step CL production of TBHQ/H ₂ O ₂ (CRET donor) was markedly enhanced by fluorescein (a typical xanthene dye, CRET acceptor) through a unique chemiluminescence resonance energy transfer (CRET) process. The novel CRET system of TBHQ/H ₂ O ₂ /fluorescein was successfully applied for the sensitive detection of TBHQ with the detection limit as low as 2.5 µmol/L. These findings will help to develop more sensitive and highly efficient CL or CRET systems and specific CL sensor to detect the carcinogenic haloquinones, which may have broad environmental applications.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023. Published by Elsevier B.V.)