Enhancing the Oxidase‐like Performances of Co_xMn_3‐xO₄ Nanoparticles by Tuning the Mn Content and Decorating Reduced Graphene Oxide

Abstract

Binary transition-metal oxides nanomaterials as oxidase-mimic have attracted great attention, but their catalytic activity and stability remain to be improved, and the underneath mechanism needs to be debated. In this work, Co x Mn 3-x O 4 nanoparticles were prepared in-situ on reduced graphene oxide sheets through a hydrothermal procedure. The morphologies, compositions, and oxidase-like activities of the Co x Mn 3-x O 4 nanoparticles supported on reduced graphene oxide (Co x Mn 3-x O 4 NPs/rGO) were studied systematically. It is demonstrated that the oxidase-like catalytic activities can be regulated by tuning not only the ratio of Co to Mn but also the content of rGO. It is illustrated that the CoMn 2 O 4 NPs/rGO4 with the rGO content of 80 % exhibits over all better oxidase-like catalytic performance. We constructed the oxidase-like catalysis mechanism of Co x Mn 3-x O 4 NPs/rGO composites. It is found that the oxidase-like activity of the composites mainly depends on CoÀ Mn synergy effect, including the cooperation of Co 2 + /Co 3 + , Mn 2 + /Mn 3 + and Mn 3 + /Mn 4 + redox pairs. More importantly, Mn 3 + was indispensable for the activation of Co 2 + /Co 3 + couples. Based on the decent oxidase-like activity of the CoMn 2 O 4 NPs/rGO composite, a proof-of concept colorimetric sensing system for L-cysteine detection was developed, which show low detection limit of 0.08 μM (S/N = 3), as well as excellent selectivity and anti-interference ability.

Co‐based Nanozymatic Profiling: Advances Spanning Chemistry, Biomedical, and Environmental Sciences

“…The doping ratio also influenced the activity of the NPs, as Zhang et al prepared Co x Mn 3-x O 4 NPs in situ on reduced graphene oxide sheets and then modulated the catalytic activity of the OXD by adjusting the Co/Mn ratio. [77] In another exciting development, Jiang et al synthesized hollow nanoporous carbon skeletons (Au/Co@HNCF) modified with Au/Co bimetallic NPs using a similar thermal cleavage method. [78] By comparing the electrochemically active surface area (ECSA) values of the materials before and after doping, they found that the number of active sites of Au/Co@HNCF was higher than that of Co@NCF, indicating the efficiency of the doping process in enhancing the activity of the NP activity.…”

“…prepared Co x Mn 3‐x O 4 NPs in situ on reduced graphene oxide sheets and then modulated the catalytic activity of the OXD by adjusting the Co/Mn ratio. [ 77 ] In another exciting development, Jiang et al. synthesized hollow nanoporous carbon skeletons (Au/Co@HNCF) modified with Au/Co bimetallic NPs using a similar thermal cleavage method.…”

“…Zhang's group loaded Co x Mn 3‐x O 4 NPs in situ on graphene sheets, forming π–π interactions with TMB. [ 77 ] This improved the adsorption rate of the substrate and the diffusion rate of the product, resulting in a low detection limit for L‐Cys of 0.08 µ m .…”

NiCo LDH nanozymes with selective antibacterial activity against Gram-negative bacteria for wound healing

“…Therefore, we select layered double hydroxides (LDHs) with positive charge as model nanozymes to study their selective antibacterial activity against G À bacteria. [20][21][22][23][24] Here, we prepared NiCo LDHs nanostructures with tunable composition, morphology, and surface area to obtain the highest antibacterial activity. Using their generated ROS based on their peroxidase-like activity, Ni 4 Co 6 LDHs could effectively kill bacteria.…”