A dual-potential electrochemiluminescence ratiometric sensor for sensitive detection of dopamine based on...

A novel dual-potential ratiometric electrochemiluminescence (ECL) sensor was designed for detecting dopamine (DA) based on graphene-CdTe quantum dots (G-CdTe QDs) as the cathodic emitter and self-enhanced Ru(II) composite (TAEA-Ru) as the anodic emitter. TAEA-Ru was prepared by linking ruthenium(II) tris(2,2'-bipyridyl-4,4'-dicarboxylato) with tris(2-aminoethyl)amine. Firstly, 3-aminopropyltriethoxysilane founctionalized G-CdTe QDs was used as the substrate for capturing target DA via the specific recognition of the diol of DA to the oxyethyl group of APTES. Then, Cu₂O nanocrystals supported TAEA-Ru was further bound by the strong interaction between amino groups of DA and carboxyl groups of the Cu₂O-TAEA-Ru. With the increase in DA concentration, the loading of Cu₂O-TAEA-Ru at the electrode increased. As a result, the anodic ECL signal from TAEA-Ru increased, and the cathodic ECL signal from G-CdTe QDs/O₂ system decreased correspondingly. Such a decrease was resulted from the ECL resonance energy transfer (RET) from G-CdTe QDs to TAEA-Ru as well as the dual quenching effects of Cu₂O to G-CdTe QDs, namely the ECL-RET from G-CdTe QDs to Cu₂O and the consumption of coreactant O₂ by Cu₂O. Based on the ratio of two ECL signals, the determination of DA was achieved with a linear range from 10.0 fM to 1.0nM and a detection limit low to 2.9 fM (S/N=3). The combination of G-CdTe QDs/O₂ and TAEA-Ru would break the limitation of the same coreatant shared in previous ECL ratiometric systems and provide a potential application of ECL ratiometric sensor in the detection of biological small molecules with the assistance of the dual molecular recognition strategy.