Luminescent nanoprobes based on upconversion nanoparticles and single-walled carbon nanohorns or graphene oxide for detection of Pb2+ion

Two kinds of luminescent nanoprobes were developed for Pb2+ detection based on luminescence resonance energy transfer (LRET) by using sodium citrate functionalized upconversion nanoparticles (Cit-UCNPs) as the energy donor and single-walled carbon nanohorns (SWCNHs) or graphene oxide (GO) as the energy acceptor. A Pb2+ aptamer 5′-NH2-(CH2)6-GGGTGGGTGGGTGGGT-3′ (denoted as pDNA) sequence was assembled with Cit-UCNPs to form the Cit-UCNPs–pDNA. By using the SWCNHs (or GO) as matrix, the final Cit-UCNPs–pDNA–SWCNHs (or Cit-UCNPs–pDNA–GO) nanoprobe can be obtained, in which the LRET process happened and the upconversion luminescence of the probe was quenched. With the addition of Pb2+, a stable G-quadruplex–Pb2+ complex was formed, which results in the separation between Cit-UCNPs–pDNA nanoparticles and SWCNHs (or GO) and the recovery of the upconversion luminescence. The two turn-on luminescence probes could detect Pb2+ ions from amongst other ions with high sensitivity and selectivity in aqueous solution. To the best of our knowledge, a nanoprobe for the detection of Pb2+ ions based on LRET between UCNPs and SWCNHs (or GO) has not been reported in the literature to date. This work demonstrates a simple yet powerful sensing strategy, which may open up potential perspectives for environmental monitoring applications.