Cascade assembly of carbon nanoflasks as a potential high-efficient nanoreactor

Abstract Asymmetric carbon nanomaterials have shown unique performance merits over their symmetric counterparts, particularly in multifunctional tunability and active site availability. However, precisely manipulating the geometric structure of asymmetric carbon nanoparticles while integrating functional components remains a major challenge. Herein, a facile and cost-effective cascade assembly strategy is proposed towards double-necked carbon nanoflasks (DCFs) at the emulsion interface formed by PEO20-PPO70-PEO20 (P123) and sodium oleate. Electron tomography and three-dimensional (3D) reconstruction analysis reveal that the newly-designed DCFs contain larger initial flasks with smaller ones grown into their body. Importantly, precursor-guided reaction kinetics regulation drives the morphological evolution of primary products from hemispherical to single-necked carbon flasks (SCFs). Furthermore, only those well-grown SCFs can enable the subsequent cascade assembly of DCFs via unique geometric constraint and hydrogen-bonding interactions. Remarkably, this newly developed cascade assembly route enables the functional modification of asymmetric carbon nanomaterials. As a proof of concept, the potential nanoreactors are further constructed by in-situ encapsulating ultra-small Ag nanoparticles (~ 5 nm) into the carbon nanoflasks. Benefiting from the stable immobilization of Ag nanoparticles, the resultant catalyst exhibits an outstanding catalytic activity for the reduction of 4-nitrophenol. This work offers a promising strategy for designing functionally integrated asymmetric nanoreactors.