双酚A在氧化石墨烯表面吸附的分子动力学模拟

双酚A(bisphenol A,BPA)是一种内分泌干扰物,会对机体多方面产生不良影响,包括生殖系统、神经系统、胚胎发育等.因此,在水环境中如何检测和去除BPA显得尤为重要.实验研究表明,氧化石墨烯(graphene oxide,GO)对BPA具有优异的吸附去除性能,但在分子层面的吸附机制尚不清楚.分子动力学模拟,能提供BPA在GO表面的动态吸附过程以及吸附构象等详细信息,可以弥补实验的不足.本文利用GROMACS分子动力学模拟软件,系统模拟了BPA在含GO的水溶液中的吸附过程,并计算了吸附自由能.结果显示:所有的BPA均被吸附在GO两侧,通过分析BPA的吸附构象以及与GO的相互作用,发现π-π疏水作用对吸附起主导作用,且显示出很好的稳定性,而静电和氢键作用增加了GO的吸附能力.通过自由能计算,BPA在GO表面的结合能达30 k J/mol,远大于水分子的5 k J/mol.这些结果进一步证实GO对BPA具有很强的吸附能力以及GO作为吸附剂在水溶液中去除BPA的可行性.

Molecular dynamics simulations of the adsorption of bisphenol A on graphene oxide

The elimination of bisphenol A (BPA) from water solution is of great importance, since BPA can cause the functional abnormalities of human endocrine system. One feasible removal method is the adsorption by graphene oxide (GO). However, the interactions between BPA and GO at an atomic level are still unclear. In this study, molecular dynamics simulations are performed to investigate the adsorption of BPA on the GO surface. The results show that all BPA molecules are attached to both sides of GO. The adsorption conformations of BPA in the closest layer to GO surface mainly exhibit two patterns. One is that the benzene rings of BPA are parallel to the basal plane of GO to form π -π structures, and the other is the two hydroxyl groups of BPAs interacting with the oxygen-contained groups on GO to form hydrogen bonds. Exploration of the detailed interactions between BPA and GO indicates that the hydrophobic π -π stacking interaction is the dominant force in the adsorption of BPA on GO, while hydrogen bonding enhances the binding of BPA on GO surface. Eventually, potential of mean forces (PMF) of BPA and water molecules on GO are calculated by umbrella sampling. The binding energy of BPA on GO reaches 30 kJ/mol, six times as large as that of water on GO, which is only about 5 kJ/mol. Our simulations further confirm that GO owns strong adsorption capacity and GO can be used as sorbent to eliminate BPA in water solution.