Fabrication Of Visualized Photoelectrochemical Sensing Platform And Its Application In Device

Photoelectrochemistry(PEC)exhibits the unique advantages and broad application prospects in biological analysis owing to its desirable features such as low background and high sensitivity.PEC process refers to a photo-to-electric conversion,which results from electron excitation and subsequent charge transfer of photoexcited materials such as organic compounds and semiconductors by a certain wavelength of light excitation.Meanwhile,colorimetric sensing technique has been intensively applied in numerous clinical diagnosis owing to its simplicity,inexpensive,and rapid detection.Colorimetry provides a favorable choice for signal transduction due to its easily discerned readout signals by the naked eye.Hence,there are broad prospects in developing visualized photoelectrochemical sensing platform by integrating the merits of both PEC and colorimetric imaging.1.Photoelectron-regulated redox reaction of polyaniline for visual detection of trace copperIn this work,we developed a photochromic sensing platform composing of emeraldine salt of polyaniline(ES-PANI)and titanium dioxide nanoparticles(TiO2 NPs)for visual detection of trace copper.Under ultraviolet light irradiation,the greenish ES-PANI could be oxidized to dark blue pernigraniline salt by the photogenerated hole of excited TiO2 NPs.In the presence of Cu2+,a light yellow leucoemeraldine salt was visually observed.The overall mechanism of color change was verified to be corresponding to the different redox states of PANI regulated by Cu species during the photochromic process.Integrating the advantages of both photoelectric property and visual detection,the redox reaction-based sensing mechanism led to a good sensitivity and high selectivity in detection of Cu2+.Besides the naked eye,two color recognition methods including reading mean green intensities in Photoshop and recording ultraviolet absorbance in microplate reader were also studied.This method was successfully applied to Cu2+ detection in human hair,and satisfactory recoveries were achieved.More significantly,our sensing platform was really simple,low-cost and able to detect an array of analytes within several minutes without requiring sophisticated equipment.This photoelectron-regulated colorimetric strategy provides a novel concept for the design of visual sensing platform,and could develop the portable test kits for rapid detection in clinical diagnosis.2.Photoelectron-initiated electrochromic tablet:design,characterization and visual analysisIn this work,we designed a photoelectron-initiated electrochromic tablet to develop a portable device for visualized photoelectrochemical(PEC)analysis.The tablet consists of an electron-injector(El)part for photo-to-electric conversion and an electrochromic(EC)part for visualized readout,which are composed of dye-sensitized titanium dioxide film and Ni-doped tungsten trioxide(WO3)film,respectively.Under the illumination of a white LED light,photoexcited electrons generated from El 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 synthesized Ni-doped WO3 film exhibits excellent transmittance modulation of more than 80%,providing an enhanced signal for visual analysis.Using pyrophosphate ions(PPi)as a model analyte,we successfully constructed a visualized PEC sensing platform based on the hydrolysis reaction of PPi and the formation of blue-colored hydrogen tungsten bronzes.Being equipped with a small light source and a dark box,the PEC tablet can perform colorimetric measurements on a portable device with good reversibility and stability.This smart PEC device provides important references for future studies on the visual application in practice.