No abstract

The interfacial adsorption of graphene oxide (GO) is crucial in phenomena such as emulsification and froth flotation, where presence of 2D nanomaterials facilitates Pickering stabilization. This process usually requires the input of high amounts of shear energy, or is aided by surfactants in order to make it possible at room temperature. In this work, a surfactant‐free method for interfacial enrichment through the use of a family of tetraalkylammonium hydrotropes, the most effective being tetraethylammonium chloride (TEAC), is demonstrated. As both GO and hydrotropes do not spontaneously enrich to interfaces on their own, this synergistic, spontaneous effect highlights that hydrotropes adsorb to GO sheets, decreasing their negative charge while rendering them more amphiphilic and therefore making it thermodynamically favorable for them to adsorb to the interface. Evidence for this adsorption includes increases in surface pressure, as well as emulsion and froth stability when both GO and hydrotropes are present in a system. Hydrotropes perform as well as or better than surfactants. Adsorption is irreversible, with XRR and AFM studies demonstrating that roughness increases with compression of the air‐water interface, showing that GO sheets are crumpling at the interface rather than desorbing, providing new routes to patterned and structured GO layers.

Light-responsive binary (azobenzene + solvent) lyotropic liquid crystals (LCs) were investigated by structural modification of simple azobenzene molecules.

sheets of graphene/graphene oxide are the building blocks of a wide range of material architectures with strong application potential in energy storage and harvesting, and environmental remediation. A consistent issue with continuous 2D sheets, especially when hundreds of such 2D sheets are stacked tightly to form films and electrodes, is their low mass transport characteristics through the assembled structure. To overcome this problem, we report a sequential, two-step photochemical technique comprising nucleation of defects on 2D nanosheets of graphene/graphene oxide by long-wavelength (UVA/UVB) irradiation, followed by the growth of nanopores in H 2 O 2 -based etching triggered by short-wavelength (UVC) irradiation. We demonstrate our ability to tailor the size (10− 100 nm) and level of porosity (16−60%) in holey graphene oxide (h-GO). To test the holey GO we synthesized, we produced the nanofiltration membranes using h-GO with different pore sizes. Membranes made from hGO nanosheets with ∼60 nm pores exhibited up to a 3.7-fold increase in water permeance and an ∼10% increase in selectivity compared to those produced by pristine GO. We attribute this unusual behavior to the presence of water transport highways (the nanopores) and a smaller interlayer distance of the hGO sheets arising from a complex balance in hydroxylation and deoxygenation reactions during the photochemical process. We demonstrated successful transition of the method to a flow-based synthesis approach with highly enhanced production rates (∼188 mg/h, an about 30-fold increase over the batch process), thereby accelerating sustainable and automated manufacturing of perforated graphene materials and their adoption in industrial uses.