The development of highly efficient and earth-abundant oxygen evolution/reduction reaction (OER/ORR) catalysts is essential for rechargeable metal–air batteries. Herein, cobalt-based hydroxide nanoparticles @ N-doping carbonic framework (CoOHCat@NCF) core–shell structures have been designed as highly stable and efficient OER/ORR bifunctional catalysts. The obtained composite shows enhanced catalytic activities and excellent stability in alkaline media. In the OER, a high turnover frequency (2.03 s^–1 at an overpotential of 0.36 V), low overpotential at high current density (100 mA·cm^–2 requiring an overpotential of 0.38 V), and excellent stability (100 mA·cm^–2 for one week with no activity loss) have been achieved. Furthermore, although cobalt species-based catalysts are known as good ORR catalysts, their hybridization with NCF obtained from metal organic frameworks successfully enhanced their ORR activities. The efficient activity of CoOHCat@NCF as a bifunctional oxygen electrocatalyst can be ascribed to the core–shell structures stabilizing the active catalytic sites and the porous shell structure favoring electrocatalysis-related mass transport.

Encapsulating well-defined nanoparticles (NPs) into metal–organic frameworks (MOFs) to form core–shell structures not only combines their properties, but may also provide synergistic functionality. Much research attention has been focused on applying core–shell NP@MOF structures to gas storage and sensing, luminescence, lithium ion batteries, selective catalysis, and cascade reactions; however, their application as photocatalysts has been reported much more rarely. Herein, we report the design of a new core–shell structure composed of semiconductor CdS NPs as the core and ZIF-8 as the shell. Both single-core–shell and multiple-core–shell CdS@ZIF-8 were synthesized by varying the concentrations of the ZIF-8 precursor. Photocatalytic hydrogen generation from formic acid over CdS@ZIF-8 demonstrated that core–shell CdS@ZIF-8 structures exhibit increased photocatalytic selectivity for H₂ generation from formic acid compared with pure CdS NPs. Furthermore, the concentration of CO in the products was significantly decreased, which benefits the application of CdS@ZIF-8 to proton-exchange membrane fuel cells. Our results provide guidance for the development of new photocatalysts based on NP@MOF core–shell materials.

By binding molecular probes that target tumor cells, gold nanoparticles (AuNPs) with superior characteristics have shown great potential in tumor molecular imaging studies. The non-invasive, high-resolution, and three-dimensional imaging of the targeted AuNPs within the tumor is desirable for both diagnosis and therapy. In this study, gold nanoflowers (AuNFs) are presented as a novel contrast agent for photoacoustic tomography (PAT). By binding to folic acid, the molecular probe, the tail-vein injected AuNFs concentrated within the tumor site in mice; this was clearly visualized by three-dimensional (3D) PAT imaging. In addition, toxicity assay proved that AuNFs were harmless to living cells and animals. Our results demonstrate that AuNFs have great potential in tumor molecular imaging.