Co₃O₄/CoFe₂O₄ Hollow Nanocube Multifunctional Nanozyme with Oxygen Vacancies for Deep-Learning-Assisted Smartphone Biosensing and Organic Pollutant Degradation

Abstract

Although the application of nanozymes has been widely studied, it is still a huge challenge to develop highly active and multifunctional nanozyme catalysts with a wider application prospect. Co 3 O 4 /CoFe 2 O 4 hollow nanocubes (HNCs) with oxygen vacancies were proposed in this study, which had a porous oxide heterostructure with CoFe 2 O 4 as the core and Co 3 O 4 as the shell. The Co 3 O 4 /CoFe 2 O 4 HNCs had three enzyme activities: peroxidase-like, oxidase-like, and catalase-like. Combining XPS depth profiling with density functional theory (DFT), the catalytic mechanism of peroxidase-like activity was explored in depth, which was mainly originated from •OH produced by the synergistic effect between the outer oxygen and inner oxygen and electron transfer between Co and Fe. A colorimetry/smartphone dual sensing platform was designed based on the peroxidase-like activity. Especially, a multifunctional intelligent sensing platform based on deep learning-YOLO v3 algorithm-assisted smartphone was constructed to realize real-time and rapid in situ detection of L-cysteine, norfloxacin, and zearalenone. Surprisingly, the detection limit of norfloxacin was low at 0.015 μM, which was better than that of the newly published detection method in the field of nanozymes. Meanwhile, the detection mechanism of L-cysteine and norfloxacin was successfully investigated by in situ FTIR. In fact, it also showed outstanding applications in detecting L-cysteine in the food environment and norfloxacin in drugs. Furthermore, Co 3 O 4 /CoFe 2 O 4 HNCs also could degrade 99.24% of rhodamine B, along with good reusability even after 10-cycle runs. Therefore, this work provided an in-depth understanding of the synergistic effect between the outer and inner oxygen in the reaction mechanism and an efficient method for establishing a deep-learning-assisted intelligent detection platform. In addition, this research also offered a good guideline for the further development and construction of nanozyme catalysts with multienzyme activities and multifunctional applications.

A Carbonate-Involved Amplification Strategy for Cathodic Electrochemiluminescence of Luminol Triggered by the Catalase-like CoO Nanorods

“…Conversely, a large number of bubbles were observed with the addition of CoO NRs into the H 2 O 2 solution. The unique phenomenon manifested only CoO NRs is characterized by the CAT-like activity . In addition, the CAT-like activity of CoO NRs was further confirmed by the UV–vis spectra of TMB.…”

“…The unique phenomenon manifested only CoO NRs is characterized by the CAT-like activity. 34 In addition, the CAT-like activity of CoO NRs was further confirmed by the UV−vis spectra of TMB. As shown in Figure S13, when CoO NRs was presented in the TMB − H 2 O 2 system, the TMB was oxidized to blue TMBox, resulting in the color of the solution turning blue.…”

Enhanced peroxidase-like activity of MOF nanozymes by co-catalysis for colorimetric detection of cholesterol

“…2 In addition, due to the advantages of low cost, simple synthesis, high stability, functional diversification, controllable activity, easy storage and good environmental tolerance, nanozymes can be used to detect ions and molecules, and have been widely used in sensing, antioxidant, and antibacterial applications, environmental monitoring and cancer therapy. [3][4][5][6][7] To date, many nanomaterials, such as metals, 8 metal oxides, 9 metal sulfides, 10 metal-organic frameworks (MOFs), 11 carbon-based, 12 etc., have been found to exhibit the activity of mimicking enzymes. Among them, MOFs, a kind of inorganicorganic porous crystal nanomaterial composed of a metal ion and an organic ligand through self-assembly, are suitable as an ideal candidate for nanozymes and have received wide attention in the research direction of nanozymes because of their natural advantages such as high specific surface area, open active site, flexible and adjustable pore size, and multi-functional structure.…”

Nanozyme Rich in Oxygen Vacancies Derived from Mn-Based Metal–Organic Gel for the Determination of Alkaline Phosphatase

“…The regulation of the interface structure is crucial to the catalytic activity of metal oxides. In order to boost the enzyme-like activity of nanomaterials, different surface engineering measures such as surface modification, size regulation, special morphology, and surface charge distribution have been widely applied for tuning the enzyme-like activity. − Recently, surface defect engineering has received more attention in regulating the activity of catalysts by means of modulating a surface electronic structure to produce more catalytic active sites. , Oxygen vacancies (OVs) as one of surface defect engineering can activate oxygen molecules adsorbed on the surface of materials and dissolved in solution to generate free radicals, which is the key active medium for igniting enzyme catalysis . For instance, nanoceria (CeO 2 ) with OVs resulting in the high ratio of Ce 3+ /Ce 4+ were considered as catalytic hotspots to significantly improve the superoxide dismutase-like activity .…”