Pd@Fe₂O₃ Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth

Abstract

Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe 2 O 3 nanorods. The interfacial strain at the Pd−γ-Fe 2 O 3 interface is minimized by the formation of an Fe x Pd "buffer phase" facilitating the growth of the nanorods. The γ-Fe 2 O 3 nanorods show a (111) orientation on the Pd(111) surface. Importantly, the Pd@γ-Fe 2 O 3 hybrid nanomaterials exhibit enhanced peroxidase activity compared to that of isolated Fe 2 O 3 nanorods with comparable surface area because of a synergistic effect for the charge separation and electron transport. The metal-templated epitaxial growth of nanostructures via wet-chemical reactions appears to be a promising strategy for the facile and high-yield synthesis of novel functional materials.

Single-atom nanozymes

“…Nanozymes, catalytic nanomaterials with enzyme-like characteristics (1,2), have attracted enormous research interests in recent years for the unique advantages of low cost, high stability, tunable catalytic activity, and ease of mass production, as well as storage, which endow them with wide applications in biosensing, tissue engineering, therapeutics, and environmental protection (3,4). Since Yan and coworkers (5) discovered the unexpected peroxidase mimicking activity of magnetic iron oxide nanoparticles, various nanozymes have been achieved by nanomaterials, such as metal oxides, noble metals, carbon materials, and metal-organic frameworks (MOFs) (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). However, there remain two contemporary challenges facing nanozyme technologies.…”

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation

“…The reactivity of nanoparticles may even be higher than that of enzymes, because any surface site can be catalytically active, whereas enzymes have only a single binding site, although its reacts with high specificity and complexity. Therefore, enzyme mimetic catalysis with nanoparticles has been successfully implemented in those cases, where small species (peroxides, superoxides, or sulfites) are involved and steric demands play only a minor role for the specificity of the reaction …”

“…Different from enzymes that typically have only a single active site, nanoparticles have many independent catalytic surface sites . As turnover numbers and catalytic rate constants are given per active subunit (as in classical enzymology), the activity of nanoparticle enzyme mimics has to be normalized to one active site.…”

“…As turnover numbers and catalytic rate constants are given per active subunit (as in classical enzymology), the activity of nanoparticle enzyme mimics has to be normalized to one active site. The ratio between the crystal volume (determined, e.g., by transmission electron microscopy) and the volume of a single unit cell of the respective compound can be used as a calibration factor to convert the total metal concentration (determined for example by atomic absorption spectroscopy) to the number of active surface sites . The specific activity (SA) is given by the formation rate of the product (in mole) versus time and the supplied amount of catalytic materials (in gram, Equation ).…”

Therapeutic applications of multifunctional nanozymes

“…As such, the enzyme-like properties of a variety of nanomaterials spanning from noble metals, [13][14][15] transition metal oxides [16][17][18][19][20] or carbon-based materials [21][22][23][24] have been explored. Also, their potential in various fields ranging from biosensor development, environmental remediation, 25,26 diagnosis, 27,28 therapeutics 29,30 or tissue engineering 31,32 has been demonstrated. Several excellent reviews have been recently published documenting work related to nanozymes and their biomedical applications.…”