The formation of two-dimensional micelles on graphene

Robinson, Benjamin and Bailey, Steven and Mazzocco, Riccardo and Bryce, Martin R. and Lambert, Colin and Kolosov, Oleg (2015) The formation of two-dimensional micelles on graphene. In: International Conference on Materials for Advanced Technologies, 2015-06-28.

Abstract

Due to its 2D structure, effective modification of surfaces and interfaces in graphene based systems is essential; efficient separation, suspension/dispersion and functionalisation of is typically achieved via surfactants in aqueous solution. However, it is well known that above a certain critical concentration, surfactants in aqueous environments self-assemble into three-dimensional spherical micelles with hydrophobic moieties shielded by a hydrophilic shell. Here we report a combined experimental and theoretical study demonstrating that surfactants can be designed to form 2D micelles, which are reported in for the first time in this study, when deposited in an aqueous environment onto atomically-flat graphitic surfaces thus opening up new strategies for processing and functionalising of 2D material surfaces and interfaces with widespread applications in biology, electronics, energy storage and information technology. Our molecular dynamics simulations indicate that such surfactants form a new class of 2D self-arranged ‘starfish’ micelles (2DSMs), which possess highly desirable and tuneable characteristics of high surface affinity coupled with unimpeded mobility. These predictions are supported by experimentally-measured interactions using a graphene coated quartz crystal microbalance, in ambient and vacuum environments. Using real-space nanoscale resolution nanomechanical sensitive ultrasonic force microscopy we correlate the molecular orientation within graphite deposited 2DSM with topographical mapping achieved by atomic force microscopy. We observe height profiles two orders of magnitude less than the 2DSM typical lateral dimension (0.60 ± 0.21 nm and 12.79 ± 2.93 nm respectively).