Rattle-type porous carbon microcapsules (RPCMs) were deliberately designed to combine multiple functions with the aim of improving the applicability of amorphous carbon in a synergistic fashion. A movable Fe3O4 nanocluster coated with porous carbon is encapsulated in the cavity of a carbon microcapsule with an eggshell-like characteristic, allowing for storage, adsorption, and exchange of matters through the mesoporous channels of the carbon layer. The synthetic strategy of RPCMs is flexible and universal, involving the constitution and carbonization of Fe3O4@PF@PS@PF template particles. This results in a double carbon shell and a sandwiched hollow cavity with a movable magnetic core. There is evidence that RPCMs possess large surface areas, hierarchical pore sizes, hydrophobicity, and magnetic responsiveness. Hence, diverse applications have been investigated. It is proved that RPCMs exhibit excellent performance in the effective enrichment of peptides/proteins. The detection limit toward peptides could reach as low as 10 nM, and the enrichment capacity toward MYO protein is as high as 410 mg/g (protein/beads). Furthermore, RPCMs are able to harvest proteins in complex real samples such as fetal bovine serum and rabbit blood. In addition, RPCMs could be fabricated in a supercapacitor electrode and display outstanding energy-storage performance. The electrochemical measurements demonstrate that RPCM-based electrodes have a specific capacitance of as high as 216 F/g (0.1 A/g), long-term cycling stability with a capacitance retention of 92.4% over 1000 cycles (0.2 A/g), and good electronic conductivity.
Keywords: magnetic nanoparticles; peptides/proteins enrichment; porous carbon; rattle structure; supercapacitor.