Highly Selective Adsorption of Plants' Leaves on Nanoparticles

Adsorption of fine particles in air by a leaf is studied experimentally. It is found that each leaf can absorb only a kind of particles with almost same size, and it also exhibits high selectivity over other particles. The SEM study reveals that the size of nanopore on the epidermis is a main factor of the highly selective adsorption; the smaller nanopores can absorb larger nanoparticles in air. The morphology of a lotus leaf, which is waterproof and dustproof, has, on the other hand, many short nanofibrils instead of nanopores. It is concluded that the nanoscale geometrical structure of a surface affects its attraction/repulsion property. The experiment also shows that one square millimeter surface with nanopores in diameter of 18 nm can absorb 2 million nanoparticles of about 200 nm in diameter from air in 24 hours. A better understanding of the adsorption/repulsion mechanism could help the further design of bio-mimetic waterproof/dustproof artificial materials and artificial porous materials/fabrics/nonwovens for adsorption of nanoparticles in air.