A visual electrochemiluminescence sensor based on the combination of distance-readout strategy and nanozymes catalyzing precipitation

Abstract

Background

Nanozyme is a kind of biomimetic enzyme with unique properties and catalytic function of nanomaterials. Various nanozymes have been applied in the development of visual biosensors because of its excellent stability and availability. Nevertheless, the current applications of nanozymes primarily focus on colorimetric sensing based on color changes, which is susceptible to external factors interference including sample solution color and ambient light. Incorporating a distance-readout strategy with nanozymes presents a promising avenue for the advancement of innovative visual biosensing technologies in the future.

Results

A visual electrochemiluminescence (ECL) sensor was developed by combining the distance-readout strategy with nanozymes catalyzing precipitation for the first time. The detection is based on the ECL length change induced by nanozymes. This sensor chip comprises a square detection area and a visual ECL channel area. A peroxidase-mimic, core-shell hollow Fe₃O₄@PDA@ZIF-67, was modified in the detection region. The substrate 4-chloro-1-naphthol was rapidly catalyzed by nanozymes to form purple precipitate benzo-4-chlorohexanedione, leading to an increase in impedance within the detection region. Consequently, the detection area's partial voltage rose while the visual channel's dropped, resulting in a shorter ECL length. As a proof-of-concept experiment, the visual distance-readout ECL sensor was utilized for the quantitative detection of H₂O₂. The alteration in ECL length exhibited a good linear relationship with H₂O₂ concentration (logarithm) within the range of 300 nM to 300 μM, with the limit of detection (LOD) of 87 nM.

Significance

This work developed a novel approach for the application of nanozymes in analytical chemistry. Compared with common colorimetric sensing, this method is more convenient and intuitive, which can effectively eliminate potential interference from humans and the environment during signal acquisition. Because biocatalytic precipitation can be formed through multiple sensing processes, this strategy holds great promise as a portable and cost-effective tool with diverse applications.