Abstract
Supraparticles consisting of nano- or microparticles have potential applications as, for example, photonic crystals, drug carriers, or heterogeneous catalysts. To avoid the use of solvent or processing liquid, one can make supraparticles by evaporating droplets of aqueous suspensions from super-liquid-repellent surfaces. Herein, a method to adjust the porosity of supraparticles is described; a high porosity is desired, for example, in catalysis. To prepare highly porous TiO2 supraparticles, polymer nanoparticles are co-dispersed in the suspension. Supraparticles are formed through evaporation of aqueous suspension droplets on superamphiphobic surfaces followed by calcination of the sacrificial polymer particles. The increase of porosity of up to 92% resulted in enhanced photocatalytic activity while maintaining sufficient mechanical stability.
Highlights
Supraparticles consisting of nano- or microparticles have potential applications as, for example, photonic crystals, drug carriers, or heterogeneous catalysts
We demonstrate that the hierarchical porous structures of the TiO2 supraparticles enhance photocatalytic performance in degrading rhodamine B (RhB)
Porous supraparticles were fabricated by first depositing a droplet of a binary nanoparticle suspension on a superamphiphobic surface (Figure 1a)
Summary
Supraparticles consisting of nano- or microparticles have potential applications as, for example, photonic crystals, drug carriers, or heterogeneous catalysts. For kinetics/thermodynamics-controlled growth methods, the self-assembly of nanoparticles is triggered by weak interactions such as hydrogen bonding, solvophobic interactions, and dipole−dipole interactions.[11−16] Instead, in template-based synthesis the assembly is controlled by using a template such as emulsions, mini-emulsions, block copolymer structures, or droplets prepared through microfluidics.[17−20] While being suitable for large-scale production, these approaches depend on chemicals, especially for size and composition engineering, which need to be separated from the supraparticles and disposed of afterward These chemicals may harm the environment and their use consumes energy. Irregular porous packings are favored when particles are not as stably dispersed and attract each other at some stage.[22,28−33]
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