Aggregation inhibition for graphene oxide nanosheets in polyelectrolyte solutions and assembly of nanocapsules with graphene oxide nanosheets as template

Abstract

A strategy for inhibiting aggregation of graphene oxide (GO) nanosheets is proposed in this work, which is important to understand the physical chemistry of the stability of GO and related factors. First, GO nanosheets (1.5–2.5 μm wide and 1.0 nm thick) were prepared by a modified Hummers' method. Then layer-by-layer (LbL) self-assembly of polyelectrolytes on GO nanosheets was carried out to obtain nanocapsules, whose premise is aggregation inhibition of GO based on the Debye–Hückel theory by considering the polyelectrolyte chain length and salt concentration. Low molecular weight polyelectrolytes and 0.5 mol L⁻¹ NaCl solution proved to be essential to inhibit the aggregation of GO nanosheets. On the basis of the aggregation inhibition, GO loaded with a hydrophobic drug, paclitaxel (PTX), were encapsulated by polyelectrolytes, showing a high loading capability of 0.4 mg mg⁻¹ and good dispersion stability. By assembling gold nanoparticles (AuNPs) in the shell, PTX was released rapidly from these nanocapsules under near infrared (NIR) irradiation. The strategy for successful aggregation inhibition of GO nanosheets in a polyelectrolyte matrix, as well as the stable loading and controlled rapid release of hydrophobic drugs, paves new paths for GO-based advanced nanomaterials and pharmaceutics.