Scission of 2D Inorganic Nanosheets via Physical Adsorption on a Nonflat Surface

We report that titania nanosheets can be orthogonally sectioned into substantially rectangular-shaped fragments when deposited on a nonflat substrate surface via spin-coating their suspension. Such events occur for all the nanosheets on the substrate surface. In the deposition process, nanosheets float and stay flat on top of the solvent surface, and adsorb on the substrate with conforming to the bumpy surface by following the descending solvent level. Because the nanosheet area is smaller than the actual area of the bumpy surface having the same projected area, the nanosheet experiences tensile stress along its lateral direction. The tensile stress originates from the intermolecular forces acting between the nanosheet and the substrate surface upon the adsorption on the substrate. Due to the high 2D anisotropy, the integrated intermolecular forces can be large enough to cleave the chemical bonds, leading to the scission of the nanosheet. This interesting finding may offer a new processing technique for cutting and shaping various 2D materials.