Engineered superhydrophilicity and superhydrophobicity of graphene-nanoplatelet coatings via thermal treatment

Superwettable materials are destined for a wide range of multifunctional applications. An ingenious, cost-effective yet simple method is proposed to control the superwettability of graphene through a thermal curing process at 300 °C under atmospheric pressure. By functionalizing graphene nanoplatelets (GNPs) with oxygenated groups, superhydrophilic surface with a water/air contact angle of 0° manifesting the ultrafast water permeation property is synthesized. Oppositely, superhydrophobic surface with antiadhesive property to water is obtained by functionalizing GNPs with siloxane groups under the same conditions. The superhydrophobicity is justified with a static contact angle of 163° ± 2.8° with a low contact angle hysteresis of 1.53° ± 0.86°. The chemical structures of the superwettable graphene are elucidated using various spectroscopy techniques. Theoretically, by using molecular dynamics simulations, we have further examined and testified the tunable superwettability phenomena of graphene. This study provides important insights into a facile approach in synthesizing advanced materials with superwettability for multifunctional high-performance applications.