Interfacial Water at Graphene Oxide Surface: Ordered or Disordered?

Abstract

The graphene oxide (GO)−water interface was simulated using Born− Oppenheimer molecular dynamics (BOMD) simulations with two different functionals, namely, revPBE-D3 and BLYP-D2, as well as a commonly used classical force field, namely, OPLS-AA. A number of different order parameters, including the orientation of the interfacial water molecules near the aromatic region of the GO surface as well as those near the oxygenated defects, were examined and compared. The BOMD interfacial waters are clearly much less structured as compared to the classical force field that shows a strongly ordered interface. Higher-level calculations, namely, symmetry adapted perturbation theory, were performed on representative clusters taken from the BOMD simulation. These calculations revealed not only that a number of conformations have similar interaction energies but also the importance of induction contribution to the interaction energies.

Water Structure, Dynamics, and Sum-Frequency Generation Spectra at Electrified Graphene Interfaces

“…This interfacial water molecular arrangement is very similar to that found e.g. at the air/water interface and at extended hydrophobic interfaces 17,18 (see SI); it is also consistent with prior simulation results obtained with both classical and DFT-based molecular dynamics 8,[19][20][21] of water at an uncharged graphene interface.…”

“…In contrast to the angular distribution that would be expected in the isotropic, uniform case (dashes), the distribution shows that most water OH groups lie almost tangent to the interface (θ ≃ 80°; see the inset in Figure b); another population is oriented away from graphene toward the bulk to form hydrogen bonds with second-layer water molecules (θ > 140°; see the inset in Figure b), and finally a small fraction of OH groups are in a “dangling” situation, oriented toward the interface (θ < 40°; see the inset in Figure b). This interfacial water molecular arrangement is very similar to that found, e.g., at the air/water interface and at extended hydrophobic interfaces , (see the SI); it is also consistent with prior simulation results obtained with both classical and DFT-based MD ,− of water at an uncharged graphene interface.…”

Infrared Nanospectroscopy at the Graphene–Electrolyte Interface

“…Second, the polarization of the field near the tip is perpendicular to the interface, which makes the nano-FTIR technique particularly sensitive to vibrational modes with transition dipole moments perpendicular to the surface . Because water molecules in the interfacial layer are mostly oriented parallel to the graphene, − this orientation makes the sensitivity to the bending mode of water particularly weak. Third, the depth sensitivity of each technique is very different as previously mentioned.…”

Adsorption of Phenolic Organic Pollutants on Graphene Oxide: Molecular Dynamics Study

“…研究采用的 GO 模型是二维周期性结构, 根据 Chen 等 [30] 通过实验合成的 GO 材料(O : C 的比为 0.12), 计算所用的 GO 模型含有 1008 个碳原子和 126 个羟基, O 与 C 的原子比为 0.125。 其周期性单元 结构的尺寸为 5.034 nm4.963 nm, 结构如图 1(a)所 示。此外, 苯酚、α-萘酚和 4-辛基酚的结构如图 1(b) [31][32] 分别在上述立方盒子中构建 了 GO 单独吸附苯酚(20 个)、α-萘酚(20 个)和 4-辛 基酚(20 个)体系的初始结构(见图 S1), 以及三种 POPs 竞争吸附体系(每种分子各 20 个)的初始结构 (见图 1(c))。模拟体系采用 SPC/E 水分子模型 [33] 。 OPLS-AA 力场是 Jorgensen 等 [34] 开发的一种全原子 力场, 被广泛应用于模拟 GO 和有机化合物的拓扑 结构 [35][36][37][38] 。邢宝山课题组 [21,[28][29] 通过 OPLS-AA 力 场成功模拟了多种芳香族有机污染物在 GO 表面的 吸附过程, 并得到了与实验观测相吻合的结果。因 此, 本研究采用 OPLS-AA 力场参数 [34] 构建了 GO 和 三种 POPs 的拓扑结构用于动力学模拟, 计算细节 详 见 补 充 材 料 。 所 有 的 分 子 动 力 学 模 拟 均 采 用 GROMACS 5.0.7 软件 [39][40] 样窗口, 以弹性系数为 1000 kJmol -1 nm -2 的简谐力 将酚类有机分子限制在选定的窗口中, 在 NPT 系综 下进行 200 ps 的平衡模拟, 再续跑 10 ns 用于数据 分析。伞形采样模拟的其他计算细节与 MD 模拟中 使用的参数相同。最后, 采用加权直方图分析方法 (Weighted Histogram Analysis Method, WHAM) [6] 得 到 PMF 并计算吸附能。 参考文献:…”