MOF derived iron oxide-based smart plasmonic Ag/Au hollow and porous nanoshells “ultra-microelectrodes” for ultra-sensitive detection of arsenic

Abstract

Engineering sensitive gold-based nanostructured “ultra-microelectrode” systems have been an essential part of As(III) sensing due to their high theoretical efficiency, high oxygen overpotential, high abundance and environmental benignity. However, it is still challenging to increase the specific active sites and enhance the electrocatalytic activity, the lack of which significantly limits the overall As(III) sensing performance and largely prevent its utilization in ultra-trace detection of As(III) in practical water systems. Herein, we report a detailed design of adsorbent assisted Fe oxide-based plasmonic Ag/Au hollow and porous nanoshells (Ag/Au HPNSs@FO) for electrochemical As(III) determination and ultra-trace detection of As(III) in practical water systems based on the integrated advantages of the plasmonic and ultra-microelectrode nanostructure. Ag nanoparticles were used merely as starting templates for the fabrication of plasmonic Ag/Au HPNSs and then, porous Fe oxide, with good adsorption capacity toward As(III), was introduced by pyrolysis treatment of MIL-100(Fe) grown on the Ag/Au HPNSs. The remarkable features of abundant micro-reactive sites, improved electrochemical activity, and synergistic effects have vastly ensured outstanding electrocatalytical performance of the arsenic redox reaction. The wide linear range of detection is from 0.05 to 16 ppb and the detection limit (3σ) is 0.01 ppb. Moreover, Ag/Au HPNSs@FO exhibits high sensitivity (922.5 μA ppb⁻¹) and stable detection. Most importantly, the ultra-trace detection of As(III) in practical water systems can be achieved by Ag/Au HPNSs@FO with unprecedentedly low concentrations (ca. 1 ppt and even lower concentrations).