Electrochemiluminescence of Supramolecular Nanorods and Their Application in the 'On-Off-On' Detection of Copper Ions.

In this work, an 'on-off-on' switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu²⁺) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10-perylenetetracarboxylic acid (PTCA) and aniline. The initial 'signal-on' state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co-reaction accelerator. In addition, ECL quencher probes (Fc-NH₂/Cu-Sub/nano-Au) were fabricated by immobilizing aminoferrocene (Fc-NH₂) on Cu-substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu-enzyme strand to form Cu²⁺-specific DNAzyme. Similarly, the 'signal-off' state was obtained by the high quenching effect of Fc-NH₂ on the ECL of the excited-state PTCA (¹PTCA*). As expected, the second 'switch-on' state could achieved by incubating with the target Cu²⁺, owing to the Cu²⁺-specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (Δ I_ECL) before and after incubating with the target Cu²⁺, the prepared Cu²⁺-specific DNAzyme-based biosensor was used for the determination of Cu²⁺ concentrations with high sensitivity, excellent selectivity, and good regeneration. [ABSTRACT FROM AUTHOR]