LAUSR

A luminescent nanoprobe (NP), MnO2-modified Er3+/Yb3+-codoped Ag2MoO4 upconversion nanoparticles (UCNPs; cod-AMO-3/MnO2), was constructed for rapid, sensitive, and selective "turn-on" detection of trace As3+. Herein, two kinds of luminescent NPs were developed based on luminescence resonance energy transfer (LRET) between cod-AMO-3 as the energy donor and MnO2 as the energy acceptor. By using MnO2 as the matrix in cod-AMO-3/MnO2 fluorometric assay, the upconversion luminescence (UCL) intensity (IUCL) of the cod-AMO-3 probe was quenched significantly through LRET, illustrating MnO2 as an efficient quencher for UCL. With the addition of As3+, a stable bidentate binuclear (BB) corner-sharing bridged complex (As5+-MnO2) was probably formed, which alters the surface of the upconversion NP, leading to gradual separation between UCNPs and MnO2 and subsequent recovery of IUCL. Interestingly, it possessed superior sensitivity, reaction kinetics, and also high selectivity toward As3+ in aqueous solution. Our optimized cod-AMO-3/MnO2 nanocomposite (NComp) demonstrated a linear range of 0-150 ppb and an ultrasensitive detection limit of 0.028 ppb for As3+, which is extremely below the regulatory level, signifying the promising practical usage of this system. To the best of our knowledge, such a surface-modified Ln3+-codoped Ag-based nanosensor being applied for As3+ detection probably has not been reported yet, and it is rather unexplored. In a nutshell, the ability to monitor the As3+ concentration may enable the rational design of a convenient platform for a diverse range of environmental monitoring applications.