Nanostructured membrane separators for electrochemical detection of heavy metals

This paper reports on a novel technique for rapid and ultrahigh sensitive separation, preconcentration, and electrochemical detection of heavy metal ions in aqueous media based on simultaneous capillary-driven flow, ion entrapment, and impedance detection and can be easily integrated on a microfluidic platform. The device is based on a unique nanostructure consisting of nanoporous anodic alumina membrane functionalized with highly ordered hexagonal arrays of metal nanoparticles (i.e., Au or Pt) with 25 nm sub-gaps on the top surface and ultrathin porous metal nanoshells on the interior walls of the pores with <; 15 nm sub-gaps. Ions separation and preconcentration are achieved by inducing microfluidic flow inside the nanopores controlled by the contact angles mistmatch on the top and pore surfaces relative to the electrolyte.