Highly Specific Colorimetric Probe for Fluoride by Triggering the Intrinsic Catalytic Activity of a AgPt–Fe₃O₄ Hybrid Nanozyme Encapsulated in SiO₂ Shells

Abstract

Current colorimetric probes for fluoride (F − ) primarily rely on organic chromophores that often suffer from unsatisfactory selectivity, complex organic synthesis, and low aqueous compatibility. Herein, we proposed a highly specific colorimetric method for F − with 100% aqueous compatibility by triggering the intrinsic peroxidase-like activity of a AgPt− Fe 3 O 4 nanozyme encapsulated in SiO 2 shells. The excellent catalytic performance of the AgPt−Fe 3 O 4 nanozyme serves as an ideal platform for sensitive colorimetric sensing. After being encapsulated in SiO 2 , the enzymelike activity of AgPt−Fe 3 O 4 is inhibited and only F − can exclusively etch the SiO 2 shell to expose the active site of the nanozyme, thereby inducing color changes via oxidation of the chromogenic substrate. The limit of detection of the proposed method can reach as low as 13.73 μM in aqueous solution, which is lower than the maximum allowable concentration (79 μM) stipulated in the World Health Organization drinking water regulation. More importantly, this method is highly specific toward F − over other types of anions commonly found in environmental water, making it capable of analyzing sewage samples with very complex matrices. Finally, the nanoprobe is embedded into a test strip by electrostatic spinning to enable the rapid, visual, and onsite detection of F − .

Engineering an Enzymatic Cascade Catalytic Smartphone-Based Sensor for Onsite Visual Ratiometric Fluorescence–Colorimetric Dual-Mode Detection of Methyl Mercaptan

“…Recently, the excellent catalytic activity makes artificial nanozymes to be prominent candidates for developing versatile optical sensing platforms in response to various targets because they could exploit the target as the initiator/inhibitor of its mimicking enzyme catalytic activity to yield/eliminate reactive oxygen species (e.g., • OH), resulting in optical signal changes. ,− Inspired by these points mentioned above, we here focused on integrating an artificial nanozyme into a smartphone for developing an enzymatic cascade response ratiometric fluorescence–colorimetric dual-mode POC sensor, achieving the onsite visual detection of CH 3 SH in a precise and practical way. To this end, we first employed hollow CeO 2 nanospheres to encapsulate aggregation-induced emission (AIE) tetraphenylethene (TPE) for successfully synthesizing a novel AIE fluorescence nanozyme CeO 2 @TPE with high catalase-like activity and strong blue emission at ∼441 nm.…”

Hollow NiCo@C Nanozyme-Embedded Paper-Based Colorimetric Aptasensor for Highly Sensitive Antibiotic Detection on a Smartphone Platform

“…As artificial substitutes to natural enzymes, nanozymes possess multiple superiorities of wide sources, low cost, and high stability. Moreover, nanozymes can efficiently catalyze the oxidization of various chromogenic substrates to produce visible color products. , Nowadays, nanozyme-based colorimetric analysis has shown bright prospects in environmental pollutant monitoring, food supervision, and disease diagnosis. , However, most nanozymes still exhibit relatively weak catalytic activity in comparison with natural enzymes, which extremely restricts their commercial application . To solve the problem, extensive efforts have been made to engineer nanozymes through precisely tuning their morphologies, sizes, components, etc .…”

Recent advances in colorimetric sensors based on nanozymes with peroxidase-like activity

“…Meanwhile, the same group established an innovative colorimetric fluoride (F − ) probe with high sensitivity and specificity based on AgPt-Fe 3 O 4 @SiO 2 . 97…”