Lin Zhao,Bixia Yang,Guoxin Zhuang,Yonglin Wen,Tingshi Zhang,Mingxiong Lin,Zanyong Zhuang,Yan Yu
Exploitation of atomic-level principles to optimize the charge transfer on ultrathin 2D heterostructures is an emerging frontier in relieving the energy and environmental crisis. Herein, a facile “topological-atom-extraction” protocol is disclosed, i.e., selective extraction of Zn from ultrathin half-unit-cell ZnIn 2 S 4 (HZIS) can embed thin In 2 O 3 domain into 1.60 nm thick HZIS layer to create an atomically thin in-plane In 2 O 3 /HZIS heterostructure. Thanks to the optimal distance and capability of charge separation, the in-plane In 2 O 3 /HZIS heterostructure is among the best ZnIn 2 S 4 -based CO 2 reduction reaction (CRR) photocatalysts, and indeed demonstrates a significant increase (from 6.8- to 128-fold) in CO production rate compared with those of out-plane ZIS@In 2 O 3 and out-plane In 2 O 3 -HZIS calcined heterostructures. Density Functional Theory simulation reveals that whereas the out-plane heterostructure has a much smaller ∆q of 0.2–0.25 e, the in-plane heterostructure with “zero distance contact” has an optimal ∆q of 1.05 e between In 2 O 3 and HZIS that induces remarkable charge redistribution on the in-plane heterojunction interface and creates local electric field confined within the ultrathin layer. The charge redistribution efficiently directs the charge-carrier separation in S-scheme photocatalytic system and endows long-lifetime carrier to CRR active HZIS. The findings demonstrate the strong versatility of engineering atomic-level heterojunctions for efficient catalysts design.
The development of sensitive breast cancer biomarker (CA 15-3) measurement techniques is of great significance for the early diagnosis and therapeutic monitoring of breast cancer worldwide. Herein, we have designed a split-type photoelectrochemical (PEC) immunoassay platform for the ultrasensitive determination of CA 15-3 using In2O3/ZnIn2S4 heterojunctions with high photovoltaic conversion performance as a photoactive substrate. Efficient photocurrent-responsive In2O3/ZnIn2S4 was formed by surface loading narrow-bandgap ZnIn2S4 on MOF-derived wide bandgap In2O3 nanomaterials. Subsequently, a sandwich immunoreaction was performed using an alkaline phosphatase (ALP)-labeled secondary antibody as a signaling indicator to produce large amounts of ascorbic acid by enzymatic biocatalysis. Since ascorbic acid is an excellent electron donor capable of promoting photogenerated electron separation in semiconductor materials, it enhances the anodic photocurrent of In2O3/ZnIn2S4-modified electrodes. Under the optimal catalyst loading and immunoreaction time, the In2O3/ZnIn2S4-based PEC immunoassay showed a good photocurrent response to CA 15-3 over a wide detection range from 1.0 mU mL−1 to 10 000 mU mL−1 with a limit of detection of 0.45 mU mL−1. Owing to the excellent photocurrent response of In2O3/ZnIn2S4 to ascorbic acid and the split-type immunoassay protocol, the constructed PEC immunosensing platform has the advantages of high precision, anti-interference, and acceptable accuracy, and the results are equivalent to those of commercial enzyme-linked immunosorbent assay (ELISA) kits.
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