Re-Dispersible 1D and 2D Nanoparticle Solid Powders without any Surfactant

Nanoparticles possess unique size-dependent physical and chemical properties and hold considerable interest as ideal, defect-free building blocks for nanostructured materials. However, due to irreversible and intrinsic self-aggregation, it is challenging to obtain dried nanoparticle powders with good redispersibility. In this work, we propose a general method to increase the dispersibility of typical 1D and 2D nanoparticles, including cellulose nanowhiskers, graphene, Laponite and montmorillonite, by combining sol-gel transitions and supercritical CO2 drying. In the resulting dried powders, the nanoparticles adopt a non-full-contact mode and maintain a loose packing structure formed during the gelation process; thus, they can be perfectly redispersed in water and some organic solvents under mild conditions. Such a promising strategy, without using a surfactant, deliberate surface-modification and high energy consumption, provides a practical solution to the transportation, storage and large-scale industrial applications of nanoparticles.