The
construction of nanozymes at the atomic level that hold structural
stability and high enzyme-like activity is now a key factor in the
optimization of an artificial enzyme. Single-atom metal/cerium oxide
(CeO2)-based nanozymes have been demonstrated to possess
a variety of enzymatic activities and radical scavenging abilities,
which are mainly attributed to the single-atom active site, redox
valence states, and abundant defect chemistry. Here, we developed
a single-atom Pd/CeO2 nanostructure by aqueous phase synthesis
that exhibits the advantages of high yield and good stability. The
Pd/CeO2 nanostructure possesses peroxidase (POD), superoxide
dismutase (SOD), and catalase (CAT) activities as well as reactive
nitrogen species free-radical scavenging activity, exhibiting multienzyme-like
activities and stability compared with CeO2 and other metal-based
nanozymes. It is worth mentioning that the Pd/CeO2 nanostructure
exhibits high POD-mimicking activity with a reaction rate of 0.88
μM/min, about 5 times higher than that of the CeO2 nanozyme. In addition, the CAT-like activity of the Pd/CeO2 nanostructure is excellent, and its scavenging rate of hydrogen
peroxide reached nearly 100% at a concentration of 50 ng/μL.
The present work shows that single-atom Pd substitution is a promising
strategy for the design of CeO2 nanozymes to exert better
effects on biomedical applications, especially with diseases related
to oxidative stress.