Biomimetic Mineralization Guided One-Pot Preparation of Gold Clusters Anchored Two-Dimensional MnO₂ Nanosheets for Fluorometric/Magnetic Bimodal Sensing

A novel fluorometric/magnetic bimodal sensor is reported based on gold nanoclusters (Au NCs)-anchored two-dimensional (2D) MnO₂ nanosheets (Au NCs–MnO₂) that are synthesized through a one-pot biomimetic mineralization process. Bovine serum albumin (BSA) was used as the template to guide the formation and assembly of the Au NCs–MnO₂ under physiological conditions and without use of any strong oxidizing agent and toxic surfactants as well as organic solvent. The fluorescence of Au NCs was first quenched by MnO₂ nanosheets, while upon H₂O₂ introduction, the MnO₂ nanosheets can be sensitively and selectively reduced to Mn²⁺ with enhanced magnetic resonance (MR) signal and rapid recovery of Au NCs fluorescence simultaneously. This dual-modal strategy can overcome the weakness of a single-fluorescence detection mode. A linear range of 0.06–2 μM toward H₂O₂ was obtained for the fluorescence mode, whereas the MR mode also allowed detection of H₂O₂ at a concentration that ranged from 0.01 to 0.2 mM. Benefiting from the BSA molecule residual on the product surface, the as-prepared Au NCs–MnO₂ displays low cytotoxicity and good biocompatibility. Importantly, the successful application of Au NCs–MnO₂ for analysis of H₂O₂ in biological samples and cells indicates that the integration of Au NCs fluorescence with Mn²⁺ MR response provides a promising bimodal sensing platform for H₂O₂ in vivo monitoring

MOF-Templated Fabrication of Hollow Co₄N@N-Doped Carbon Porous Nanocages with Superior Catalytic Activity

Metallic Co₄N catalysts have been considered as one of the most promising non-noble materials for heterogeneous catalysis because of their high electrical conductivity, great magnetic property, and high intrinsic activity. However, the metastable properties seriously limit their applications for heterogeneous water phase catalysis. In this work, a novel Co-metal–organic framework (MOF)-derived hollow porous nanocages (PNCs) composed of metallic Co₄N and N-doped carbon (NC) were synthesized for the first time. This hollow three-dimensional (3D) PNC catalyst was synthesized by taking advantage of Co-MOF as a precursor for fabricating 3D hollow Co₃O₄@C PNCs, along with the NH₃ treatment of Co-oxide frames to promote the in situ conversion of Co-MOF to Co₄N@NC PNCs, benefiting from the high intrinsic activity and electron conductivity of the metallic Co₄N phase and the good permeability of the hollow porous nanostructure as well as the efficient doping of N into the carbon layer. Besides, the covalent bridge between the active Co₄N surface and PNC shells also provides facile pathways for electron and mass transport. The obtained Co₄N@NC PNCs exhibit excellent catalytic activity and stability for 4-nitrophenol reduction in terms of low activation energy (<i>E</i>_a = 23.53 kJ mol^–1), high turnover frequency (52.01 × 10²⁰ molecule g^–1 min^–1), and high apparent rate constant (<i>k</i>_app = 2.106 min^–1). Furthermore, its magnetic property and stable configuration account for the excellent recyclability of the catalyst. It is hoped that our finding could pave the way for the construction of other hollow transition metal-based nitride@NC PNC catalysts for wide applications