Synthesis of SiO2@MnCo2O4 core–shell nanorattles using layered double hydroxide precursors and studies on their peroxidase-like activity

Abstract

The current work demonstrates a simple soft chemical approach to synthesize SiO₂@MnCo₂O₄ core–shell nanorattles using SiO₂@MnCo-LDH (layered double hydroxide) precursors. XRD analysis indicates the formation of MnCo₂O₄ nanoparticles (NPs) on SiO₂ spheres. FESEM images show hierarchical flower-like MnCo₂O₄ NPs on the surface of the SiO₂ spheres. TEM micrographs show the interstitial space between the core (SiO₂) and the shell (MnCo₂O₄), indicating the core–shell nanorattle morphology of SiO₂@MnCo₂O₄. BET adsorption–desorption isotherms of the SiO₂@MnCo₂O₄ core–shell nanorattles indicate their mesoporous nature with high surface area. Optical studies indicate O²⁻ → Mn²⁺ and O²⁻ → Co³⁺ charge-transfer transitions and d–d transition in pure MnCo₂O₄ NPs and the SiO₂@MnCo₂O₄ core–shell nanorattles. XPS measurements indicate the presence of Si⁴⁺, Mn²⁺, Co²⁺, Mn³⁺, Co³⁺, and O²⁻ in the SiO₂@MnCo₂O₄ core–shell nanorattles. The SiO₂@MnCo₂O₄ core–shell nanorattles show paramagnetic and superparamagnetic behavior at 300 K and 5 K, respectively. After characterization, the SiO₂@MnCo₂O₄ core–shell nanorattles were explored for peroxidase-like activity for the first time. The SiO₂@MnCo₂O₄ core–shell nanorattles act as a peroxidase nanozyme and exhibit better peroxidase-like activity than pure MnCo₂O₄ NPs and horseradish peroxidase.