Cerium Dioxide-Mediated Signal "On-Off" by Resonance Energy Transfer on a Lab-On-Paper Device for Ultrasensitive Detection of Lead Ions.

In this report, a 3D microfluidic lab-on-paper device for ultrasensitive detection of lead cation was designed using phoenix tree fruit-shaped CeO2 nanoparticles (PFCeO2 NPs) as the catalyst and 50 nm silver NPs (Ag NPs) as the quencher. First, snowflake-like Ag NPs were grown on the paper working electrode through an in situ growth method and used as a matrix for DNAzymes that were specific for lead ions (Pb2+). After the addition of Ag NP-labeled substrate strands, the Ag NPs restrained the electrochemiluminescence (ECL) intensity of luminol greatly through the resonance energy transfer from luminol to Ag NPs. However, under the existence of Pb2+, the substrate strands were separated, and then PFCeO2 NP-labeled signal strands were hybridized with the DNAzymes. The ECL signal was improved greatly under the fast catalytic reaction between PFCeO2 NPs and H2O2, which converted the response from signal off to signal on state, resulting in sensitive detection of Pb2+. Under the optimal conditions, the ECL signal response exhibited a good linear relationship with the logarithm of lead cation in a wide linear range of 0.05-2000 nM and an ultralow detection limit of 0.016 nM. Meanwhile, a sensor featured with good specificity, acceptable stability, reproducibility, and low cost provides a promising portable, simple, and effective strategy for Pb2+ detection.