Portable Photoelectrochemical Device Integrated with Self-Powered Electrochromic Tablet for Visual Analysis.

A portable photoelectrochemical (PEC) device is developed by intergating a self-powered electrochromic tablet for visual analysis. The tablet consists of an electron-injector (EI) part for photo-to-electric conversion and an electrochromic (EC) part for visualized readout, which are coated with dye-sensitized titanium dioxide film and Ni-doped tungsten trioxide (WO3) film, respectively. Under the illumination of a white LED light, the photoexcited electrons generated from EI part convey to EC part through the conductive inner side of indium tin oxide slide and would cause color change of the Ni-doped WO3 film in the presence of protons. Furthermore, the Ni-doped WO3 film exhibits excellent transmittance modulation of more than 80%, providing an enhanced signal for visual analysis. Using pyrophosphate ion (PPi) as a model analyte, we have successfully constructed a visualized PEC sensing platform based on the formation of blue-colored hydrogen tungsten bronzes via the hydrolysis reaction of PPi. Being equipped with a small light source and a dark box, the PEC tablet as a portable device can perform colorimetric measurement with good reversibility and stability. This smart PEC device provides important reference for future studies on the visual application in practice.