Post-synthetic strategies for site-selective engineering and functionalization of nanocrystal-surfaces are important for tuning and maximizing the nanoscale-properties, useful in various applications, mainly in catalysis. In spite of the tremendous application potential, the synthesis of the 3-dimensional nanocrystals with anisotropic high-energy negative surface-curvature composed of densely populated low-coordinated atoms is still elusive. The existing strategies towards concave-surface-nanocrystals can only generate negative curvatures indiscriminately, all around the nanocrystal’s chemically equivalent facets, resulting a symmetrical structure. Before our work, there was no method for controllable and facet-selective fabrication of single concave-cavity in a symmetrical 3-dimensional nanocrystal, leaving other parts of the nanostructure unaffected. We developed a highly selective solid-state nanocrystal conversion strategy under thermal reductive conditions towards concave iron oxide (Fe3O4) nanocube with an open-mouthed cavity engraved exclusively on a single face of the nanocube. The systematic mechanistic studies based on the investigation of time-course reaction snapshots and various control experiments on the facet-selective cavitation process revealed a novel heat-induced nanospace-confined domino-type migration of Fe2+ ions from the SiO2-Fe3O4 interface towards the surrounding silica shell and simultaneous self-limiting nanoscale phase-transition to the Fe-silicate form. Installed with the mono-directional single cavity, the produced Janus-type concave iron oxide nanocube was further functionalized with controllable density of catalytic Pt-nanocrystals exclusively on concave sites; and such nanostructure was utilized as H2O2-fueled highly diffusive catalytic Janus nanoswimmer for the efficient degradation of pollutant-dyes in water.

Monofacet-selective cavitation within solid-state silica-nanoconfinement towards Janus iron oxide nanocube

2019 Fall National Meeting

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