Biomimetic assembly of polydopamine-layer on graphene: Mechanisms, versatile 2D and 3D architectures and pollutant disposal

Single layer graphene was employed as an ultrathin substrate (<1 nm) to clarify the self-assembly process of polydopamine (PDA). The self-assembly of the PDA coated graphene nanosheets was conducted at different reaction concentrations and times, and monitored by atomic force microscopy images. The results indicated that the thickness of the PDA coatings could be conveniently controlled in a range from nearly a single PDA monolayer to tens of nanometers. Meanwhile, thermogravimetric curves, AFM phase images and alkali treatment study suggested that the PDA clusters were formed by crosslinked conjugates. Field emission scanning electron microscope results indicated that the PDA clusters exhibited surface dependent aggregation and roughness. The typical procedure for the synthesis of PDA coated reduced graphene oxide (RGO) can be divided into three steps: (1) dopamine converts GO into RGO; (2) the pH induced spontaneously polymerization of DA and deposition of PDA precursors on the RGO surface; (3) the further growth of PDA precursors and the self-assembly into large PDA clusters. Furthermore, the PDA layer assembled graphene sheets could function as versatile templates to construct 2D architectures with mineralized inorganic/metal nanoparticles; and the regarding catalytic ability and the adsorption of heavy metal ions were studied. Moreover, the DA can function as reductant for low temperature assembly of porous 3D hydrogel via pi-pi interactions and PDA polymerization. The PDA assembled graphene areogel can be used as a promising adsorbent for the removal of oils, organic solvents and dyes from contaminated water. (C) 2013 Elsevier B.V. All rights reserved.