One-Step Exfoliation/Etching Method to Produce Chitosan-Stabilized Holey Graphene Nanosheets for Superior DNA Adsorption.

Holey graphene (HG) features universal applications in adsorption because of the large surface areas and the abundant active sites across the nanopores, but it is difficult to produce HG nanosheets straightforwardly from bulk graphite with current etching methods. Herein, for the first time, we developed a one-step sonication-assisted liquid-phase exfoliation/etching method to produce HG nanosheets from bulk graphite by taking advantage of chitosan for stabilization. With the cavitation bubble collapse stress during the intense sonication, the graphite powders were exfoliated and nanopores of tunable diameters from 40 to 200 nm were generated across the graphene nanosheets. Importantly, with chitosan as the stabilizing agent to reduce the fluid collapse stress transferred onto the graphene nanosheets, the lateral size of HG could be as large as 30 μm. Using this approach, several holey layered crystals (graphite, hexagonal boron nitride, and tungsten disulfide) were fabricated with adequate nanostructures, including lateral size, nanosheet thickness, and nanopore size. Notably, the nanoporous structure endowed the graphene nanosheets with superior high double-stranded DNA adsorption (1253 μg/mg, the highest until now) and excellent DNA protection capacity. Based on this, the HG nanosheets were developed for the surface-mediated reversal gene transfection, displaying appreciable efficiency with the traditional methods.