Solution Evaporation-Driven Crumpling and Assembling of Large-Accessible-Space, High-Mechanical-Strength Graphene/Carbon Nanotube Composite Nanoparticles.

Crumpled graphene particles that are converted and assembled from 2D planar graphene sheets create a subtle material platform for widespread applications of graphene in a low-cost and scalable manner. However, such crumpled particles are suffering from small spatial availabilities in geometry and low strength in mechanical deformation due to the limited numbers and stabilities of connections among individual deformed graphene. Herein, we report, in both theoretical analysis and large-scale atomistic simulations, that a crumpled graphene composite nanoparticle with large accessible space and high mechanical strength can be achieved by encapsulating folded carbon nanotubes (CNTs) inside via a solvent evaporation-induced assembly approach. A unified energy-based theoretical model is developed to address the kinetic migration of both CNTs and graphene suspended in a liquid droplet and their crumpling and assembling mechanism into a composite particle by solution evaporation. The contact probability, surface ridge densities, and geometric size in assembled graphene/CNT composite nanoparticles are quantitatively extracted after the complete evaporation of liquid and are further correlated with their accessible space including accessible surface area and volume and mechanical strength. The coarse-grained molecular dynamics simulations are conducted to uncover structural and morphological evolution of graphene/CNT composite nanoparticles with solution evaporation, and the results show remarkable agreement with theoretical predictions. This study offers a theoretical foundation for synthesizing highly connected, mechanically enhanced, crumpled particles with tunable spatial porous structures by tailoring graphene and CNTs for applications in functional structures and devices.