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.