Organic–Inorganic\nHybrid Flower-Shaped Microspheres\nApplied in Photoelectrochemical Sensing

Abstract

Organic–inorganic hybrid materials\nare rarely applied in\nphotoelectrochemical (PEC) sensing because of the serious charge-carrier\nrecombination in organic conjugated polymers. In this work, a series\nof poly­(3,4-ethylenedioxythiophene) (PEDOT)/ZnIn₂S₄ hybrid flower-shaped microspheres were synthesized using\nionic liquids (ILs) as the supporting electrolyte for EDOT electropolymerization\nand as the regulating reagent for controlling ZnIn₂S₄ growth, respectively. It was found that the hybrid material\n[HOEMIM]­NTf₂-PEDOT/[HOEMIM]­BF₄-ZnIn₂S₄ ([HOEMIM]⁺: 1-hydroxyethyl-3-methylimidazolium\ncation; NTf₂^–: bis­(trifluoromethanesulfonyl)­amide)\nwas the optimal one, with a smooth, transparent, and continuous polymer\nfilm covering the uniform and ordered cross-linked nanosheet arrays.\nThe hybrid material could produce a high anodic photocurrent, which\nwas about 78 times as high as that produced by the [HOEMIM]­BF₄-ZnIn₂S₄. The enhancement effect should\nbe the highest among all the organic–inorganic hybrid materials\nreported so far. This was related to its unique micromorphology structure,\np-n heterojunction, and the coexisting ILs, which restrained the charge-carrier\nrecombination in PEDOT and enhanced PEDOT sensitization to ZnIn₂S₄. Then, a carcinoembryonic antigen PEC immunosensor\nwas constructed based on the photoanodic sensing platform, and it\nexhibited good performance. Furthermore, the [HOEMIM]­BF₄-ZnIn₂S₄ was treated with NaClO solution to\ncreate the [HOEMIM]­NTf₂-PEDOT/[HOEMIM]­BF₄-S-Zn_<i>w</i>In_<i>x</i>S_<i>y</i>O_<i>z</i> general platform for\nboth photoanodic and photocathodic sensing. As a proof of concept,\nL-cysteine and dissolved oxygen were used as models for photoanodic\nand photocathodic sensing, respectively. The results demonstrated\nthat the general PEC platform was quite competent. This work opens\nup a window for the design of organic–inorganic hybrid PEC\nmaterials and will promote the application of such hybrid materials\nin PEC biosensing.