A Simple Method for High-Quality Ultra-Thin Graphene Oxide Films Facilitates Nanoscale Investigations of Ion and Water Adsorption

Abstract

Graphene oxide (GO) is a promising material for separations. Nanoscale GO thin films at the air/water interface are excellent experimental models to understand molecular-scale interactions of ions and water with GO. However, thin film formation strongly depends on how the GO was processed. This paper reports a simple, reliable, and quick method of preparing ultra-thin GO films, irrespective of their origin. This method allows the quantitative investigation of differences in film structure, ion adsorption, and interfacial water behavior with multiple surface sensitive probes. The data show that functional groups and oxidative debris vary significantly between different commercially available GO samples. These differences strongly affect ion adsorption and interfacial water behavior near GO, which are vital properties in separation applications. The results demonstrate the importance of the GO process conditions and provide experimental methods to quantify molecular-scale differences between different GO films.

Convenient Confinement: Interplay of Solution Conditions and Graphene Oxide Film Structure on Rare Earth Separations

“…Data collected at pH < 3 show a prominent peak around 3600 cm -1 . We attribute this signal to water trapped within or coordinating mainly to the GO film, 32 the structure of which is described later using XR. This water population changes slightly with increasing subphase pH but is largely unaffected.…”

“…Samples were then diluted 1:5 using anhydrous methanol (Sigma Aldrich), sonicated for 1 hour, and filtered through a 1.2 µm syringe filter. 32 We created interfacial GO films by the dropwise addition of prepared GO solutions onto an aqueous subphase using a 1 mL glass syringe. The surface pressure was monitored using a pressure sensor (Nima)equipped with a Wilhelmy plate (chromatography paper).…”

“…[29][30][31] We have recently demonstrated a universal GO thin film preparation method that allows investigation of molecular-scale GO/ion/water interactions at high resolution. 32 Understanding the effects of solution conditions on film structure is similarly important and challenging. There is no easy way to tune individual film 4 or subphase parameters, as the entire system is affected by even minor changes.…”

Convenient Confinement: Interplay of Solution Conditions and Graphene Oxide Film Structure on Rare Earth Separations

“…Samples were then diluted 1:5 using anhydrous methanol (Sigma-Aldrich), sonicated for 1 h, and filtered through a 1.2 μm syringe filter. 35 Interfacial Graphene Oxide Film Preparation. The interfacial GO films were created by the dropwise addition of prepared GO solutions onto an aqueous subphase using a 1 mL glass syringe.…”

“…32−34 Our group recently demonstrated a universal GO thin film preparation method that allows investigation of molecular-scale GO/ion/water interactions at high resolution. 35 Understanding the effects of solution conditions on film structure is similarly important and challenging. There is no easy way to tune individual film or subphase parameters, as the entire system is affected by even minor changes.…”