Conductive NiCo bimetal-organic framework nanorods with conductivity-enhanced electrochemiluminescence for constructing biosensing platform

Abstract

Metal-organic frameworks (MOFs) has recently attracted immense attention in electrochemiluminescence (ECL) field, yet the ECL performance of MOFs is largely limited by their natively poor electric conductivity (generally < 10−8S m−1). To address this drawback, we adopted the doping strategy to synthesize a conductive bimetallic MOF nanorod [NixCo9-x(HHTP)4(H2O)30] (denoted as NiCo-HHTP, HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with excellent electrical conductivity (1.20 × 10−3S m−1), which could accelerate the charge transport and facilitate the electrochemical activation of HHTP luminophore, thereby improving utilization ratio of ECL luminophores to achieve a strong ECL emission. As expected, our experiment showed that the bimetallic NiCo-HHTP was superior to the isostructural monometallic MOF (Ni-HHTP) with nearly 2.82-fold higher electrical conductivity, 2.06-fold higher ECL intensity and 3.39-fold higher ECL efficiency. These results suggested that the electrical conductivity of NiCo-HHTP could be significantly improved by doping with cobalt, and the outstanding electrical conductivity greatly contributed to its excellent ECL performance. Considering the above-mentioned superior ECL properties, the NiCo-HHTP nanorods were utilized to fabricate an ultrasensitive ECL biosensor for microRNA-141 determination, achieving a wide linear range from 1 fM to 10 nM and a low detection limit of 0.69 fM. Overall, our work proposed a hopeful and practicable strategy to improve ECL performance via enhancing electrical conductivity of MOFs, which overcame current limitation of ECL enhancement in nonconductive MOFs and opened a new chapter to prepare high-efficiency MOF-based ECL materials, thus providing a unique opportunity for constructing ultrasensitive ECL sensors.