Ion exchange reaction-mediated highly sensitive and selective photoelectrochemical assay of Hg(II) based on indirect Z-scheme heterostructure of TiO NPs/Au/3D tremella-like ZnInS.

An indirect Z-scheme heterostructure of TiO nanoparticles (NPs)/Au/3D tremella-like ZnInS as a photoelectrochemical (PEC) substrate was utilized to construct a highly sensitive and selective PEC sensor for the detection of Hg(II) by combining an ion exchange reaction-mediated signal amplification strategy. After assembling TiO NPs, Au NPs, and 3D tremella-like ZnInS step by step on the indium tin oxide (ITO) electrode, the indirect Z-scheme heterostructure was built, in which ZnInS works as Hg(II)-recognition probe. Importantly, this heterostructure could effectively restrict the rapid recombination of photoinduced carriers to generate an enhanced initial photocurrent for upgrading the sensitivity. With the introduction of Hg(II), the selective Zn-to-Hg ion exchange reaction was activated, and it could in situ form HgS, leading to the quenching of the PEC signal. The designed PEC device presented good performance for Hg(II) assay, with a broad linear range from 0.0005 to 10,000 nM and a detection limit of 0.32 pM. Thus, this protocol is expected to be utilized for elevating food supervision and environmental assessment via Hg(II) determination.