Coreactant enhanced anodic electrochemiluminescence of CdTe quantum dots at low potential for sensitive biosensing amplified by enzymatic cycle.

This work used sulfite as a coreactant to enhance the anodic electrochemiluminescence (ECL) of mercaptopropionic acid modified CdTe quantum dots (QDs). This strategy proposed the first coreactant anodic ECL of QDs and led to a sensitive ECL emission of QDs in aqueous solution at relatively low potential. In the presence of dissolved oxygen, the stable ECL emission resulted from the excited QDs. Thus, an ECL detection method was proposed at +0.90 V (vs Ag/AgCl) based on the quenching of excited QDs by the analyte. Using tyrosine as a model compound, whose electrooxidized product could quench the excited QDs and thus the ECL emission, an analytical method for detection of tyrosine in a wide concentration range was developed. Furthermore, by combining an enzymatic cycle of trace tyrosinase to produce the oxidized product with an energy-transfer process, an extremely sensitive method for ECL detection of tyrosine with a subpicomolar limit of detection was developed. The sulfite-enhanced anodic ECL emission provided an alternative for traditional ECL light emitters and a new methodology for extremely sensitive ECL detection of mono- and dihydroxybenzenes at relatively low anodic potential. This strategy could be easily realized and opened new avenues for the applications of QDs in ECL biosensing.