Driskill Joshua, Vanzo Davide, Bratko Dusan, Luzar Alenka
Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, USA.
J Chem Phys. 2014 Nov 14;141(18):18C517. doi: 10.1063/1.4895541.
Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm(-1) lower than for graphene wetted only on one side, which gives close to 10° reduction in contact angle. This difference has potential implications for predictions of water absorption vs. desorption, phase behavior of water in aqueous nanoconfinements, solvent-induced interactions among graphitic nanoparticle and concomitant stability in aqueous dispersions, and can influence permeability of porous materials such as carbon nanotubes by water and aqueous solutions.
对石墨烯片上接触角的测量表明，其对底层基底的性质有显著依赖性，这一现象被称为润湿性透明。我们的分子模拟研究表明，在水中浸没的石墨烯片段的情况下也存在类似的透明性。色散吸引力、水偶极之间的角度相关性以及由于氢键诱导的极化水化层中跨石墨烯片的取向偏差所产生的排斥力的综合作用，增强了水对石墨烯的表观附着力。我们发现，完全润湿的石墨烯薄片的润湿自由能比仅一侧被润湿的石墨烯低约8 mN/m，这使得接触角降低了近10°。这种差异对于预测吸水与解吸、水在水性纳米限域中的相行为、溶剂诱导的石墨纳米颗粒之间的相互作用以及在水性分散体中的伴随稳定性具有潜在影响，并且会影响水和水溶液对碳纳米管等多孔材料的渗透性。
