Abstract
The Fe2O3 nanozyme has been identified as the most promising alternative for the Fe3O4 nanozyme due to its relatively low toxic risk and good chemical stability. However, its enzyme-like activity is relatively low enough to meet specific application requirements. Furthermore, previous synthesis approaches have difficulties in fabricating ultra-small Fe2O3 nanoparticles with tunable size and suffer from agglomeration problems. In this study, atomic layer deposition (ALD) was used to deposit Fe2O3 on surfaces of carbon nanotubes to form hybrid nanozymes (Fe2O3/CNTs). ALD enables the preparation of ultrafine Fe2O3 nanoparticles with precise size control <1 nm, while CNTs could be served as promising support for good dispersibility and as an effective activity activator. Hence, the formed Fe2O3/CNTs exhibit excellent peroxidase-like activity with a specific peroxidase activity of 24.5 U mg−1. A colorimetric method for sensing dopamine (DA) was established and presented good sensitivity with a limit of detection (LOD) as low as 0.11 μM. These results demonstrated that, in virtue of meticulous engineering methods like ALD, carbon nanomaterial-based hybrids can be developed as talented enzyme mimetic, thus paving a way for nanozyme design with desired activity and broadening their applications in biosensing and other fields.
Highlights
It is well-known that nanozymes have been developed as the most promising alternative for natural enzymes, owing to their good stability, simple and large-scale preparation, and cost effectiveness (Gao et al, 2007; Lin et al, 2014; Wang et al, 2019)
With increasing atomic layer deposition (ALD) cycles, it remained difficult to identify the existence of Fe2O3 in the Transmission electron microscopy (TEM) image of 10Fe2O3/Carbon nanotubes (CNTs) (Figure 1B), but the HAADF image (Figure 1C) recorded at the same region reveals visibly the successful deposition of Fe2O3 nanoparticles on CNTs
It is worth noting that the as-synthesized Fe2O3 by ALD is amorphous with no visible crystalline structure found in high-resolution TEM (HRTEM) images
Summary
It is well-known that nanozymes have been developed as the most promising alternative for natural enzymes, owing to their good stability, simple and large-scale preparation, and cost effectiveness (Gao et al, 2007; Lin et al, 2014; Wang et al, 2019). As the most studied nanozymes, iron oxide nanozymes (IONzymes) have attracted great interest since the first exciting discovery that ferromagnetic oxide possesses an intrinsic peroxidase activity (Gao et al, 2007), and they show great application potential in fields of biosensing, magnetic. Nanotube-Supported Fe2O3 Hybrid Nanozyme resonance imaging, anti-biofouling, and cancer therapy (Cheng et al, 2017; Jiang et al, 2019; Li et al, 2019; Wang et al, 2019; Šálek et al, 2020). Fe2O3 nanozymes should be better candidates for applications. Their enzyme-mimicking activities are relatively low enough to meet a variety of specific application requirements (e.g., biosensing, antimicrobial therapy). It remains a great challenge to synthesize ultrafine Fe2O3 nanoparticles with both controllable and uniform sizes, as well as to eliminate nanoparticle aggregation, which could inevitably affect their enzyme-like activity during catalytic reaction
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