Abstract: Nitrogen-doped carbon quantum dots (N-CQDs), synthesized via the rapid pyrolysis of ammonium citrate dibasic and ethylenediamine dihydrochloride, demonstrate remarkable chemiluminescence capabilities, emitting a vibrant blue-green light in peroxyoxalate chemiluminescence (PO-CL) reactions. Among these, a distinct variant of N-CQDs is an exceptionally sensitive biosensor, facilitating the swift detection of copper ions (Cu²⁺) within human plasma and urine samples. Upon rapid binding of N-CQDs and Cu²⁺, non-emissive complex forms due to intra-chemiluminescence resonance energy transfer (intra-CRET) initiated by the PO-CL reaction. Consequently, the brightness of the biosensor diminishes proportionally with increasing Cu²⁺ concentrations in human samples. Featuring a low sensing limit of 19.5 nM and an expansive dynamic range spanning from 0.05 to 3.8 µM, this biosensor empowers the rapid and precise quantification of trace Cu²⁺ levels with exceptional accuracy and recovery rates. In alignment with copper quantification guidelines set forth by the Environmental Protection Agency (EPA) and the National Institutes of Health (NIH), this selective biosensor stands as a cutting-edge monitoring tool, poised to advance analytical capabilities in various fields.

Key words: Nitrogen-doped carbon quantum dots (N-CQDs), Peroxyoxalate chemiluminescence (PO-CL), Chemiluminescence resonance energy transfer (CRET), Biosensor, Photoluminescence