Abstract
Nanozymes hold huge potential in various fields, but their much lower catalytic activities than natural enzymes greatly limit their extensive applications. Recent studies indicated that an enhanced enzyme-like activity could be obtained by decreasing the particle size through rational design because smaller nanoparticles (NPs) have larger surface-area-to-volume ratios and more unsaturated sites, which are beneficial to the adsorption of reactant species. However, ultrasmall NPs have low adsorption energy and poor stability, which makes the synthesis of superstable and ultrasmall nanozymes extremely difficult. Several interesting works reported that the encapsulation of ultrasmall NPs with few-layer carbon shells could effectively protect them from dissolution and agglomeration, and meanwhile, their catalytic activities were not greatly affected. Herein, we report a superstable and ultrasmall graphene encapsuled CoRu nanocrystal (CoRu@G) with the CoRu alloy confined in the nanospace of few-layer graphene via the chemical vapor deposition method. It shows excellent corrosion resistance in aqua regia due to the protection of the chemically inert graphitic shell. The intrinsic peroxidase-, oxidase-, and catalase-like activities of the CoRu@G are systematically explored, including the influence of the concentration, pH, and temperature on the enzyme-like activity, steady-state kinetic analysis, and catalytic oxidation mechanism study. Significantly, the CoRu@G shows an excellent and ultrastable enzyme-like activity with the treatment of high temperatures, buffered solutions, or NaCl solutions probably because the graphene layer protects it from dissolution and agglomeration efficiently. We believe that the proposed graphene confinement strategy could highlight the direction of highly active, superstable, and ultrasmall-sized nanozyme preparation.
Highlights
The CoRu@G was prepared by the chemical vapor deposition (CVD) method according to the previously reported works, and it was further functionalized with polyoxyethylene stearyl ether (C18-PEG) through hydrophobic interactions to improve water solubility.[27,28]
As shown in the high-resolution transmission electron microscope (TEM) (HR-TEM) image of CoRu@G [Fig. 1(c)], few-layer graphene encapsuled on the surface of the CoRu alloy core, which was similar to the schematic diagram in the inset of Fig. 1(c)
We investigated the effect of temperature, NaCl, and buffered solution on the POD-like activity of CoRu@G evaluated by the TMB/H2O2/CoRu@G system
Summary
Nanozymes that integrate the functions of both natural enzymes and nanomaterials have attracted enormous interest due to their outstanding merits of low cost, high stability, tunable catalytic activities, and ease of production and storage.[1,2,3,4] Since Gao et al.[5] discovered the intrinsic peroxidase (POD)-like activity of Fe3O4 nanoparticles (NPs) in 2007, a series of nanozymes with POD,[6,7,8] oxidase (OXD),[9–11] catalase (CAT),[12–14] superoxide dismutase (SOD),[15] and glutathione peroxidase (GPx)[16] mimicking activities have been reported, and the versatility of nanozymes has greatly promoted the development of biomedicine[17–19] and environmental protection.[20,21] nanozymes have much lower catalytic activities than natural enzymes owing to the low densities of active sites, which makes it difficult to replace natural enzymes and limits their scitation.org/journal/apm extensive applications.[22–24] It is reported that the catalytic activity of nanozymes is highly dependent on the nanoparticle (NP) size.[25]. The intrinsic peroxidase-, oxidase-, and catalase-like activities of the CoRu@G are systematically explored, including the influence of the concentration, pH, and temperature on the enzyme-like activity, steady-state kinetic analysis, and catalytic oxidation mechanism study.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
