Facile Gram-Scale Production of Cu/Cu ₂ O Core/Shell Nanoparticles Densely Embedded in a Porous Carbon Framework for Cost-Effective Peroxidase Mimicking

Natural enzymes are efficient catalysts but face high costs and instability, leading to the development of artificial enzymes like nanozymes. While noble metals commonly demonstrate high peroxidase (POD)-like activity, their expense limits their practical use. In contrast, 3d transition metal oxides, though less active, are more cost-effective due to their natural abundance, with Cu(I) emerging as a promising candidate. However, maximizing POD-like activity in small-sized Cu₂O nanoparticles (NPs) often requires complex synthetic processes and labor-intensive purification, making mass production challenging. To address these issues, it is crucial to develop POD nanozymes with simplified production methods that would reduce costs and facilitate their real-world applications. Herein, we present a straightforward and scalable method for preparing Cu/Cu₂O core/shell NPs densely embedded within a porous carbon-based framework by calcining Cu precursor and polyvinylpyrrolidone (PVP) at elevated temperatures in nitrogen. The resulting samples with Cu/Cu₂O NPs around 15 nm in size can be obtained at temperatures below 600 °C. Importantly, they can be used directly without purification, significantly reducing production costs compared to natural enzymes. The sample obtained at 300 °C, exhibiting the highest Cu(I) content, displays optimal POD-like activity and was further demonstrated in the detection of glutathione and glucose. This study is anticipated to guide the future development of scalable and cost-effective POD nanozymes for practical applications.