The effects of L-serine amino acid functionalization on a graphene plane were investigated through density functional theory calculations compared with those of oxygen functionalization. Three systems of 4 × 4 graphene supercells were created and functionalized by an epoxy group, a hydroxyl group, and an L-serine molecule. From the geometry optimization of the system containing a 4 × 4 graphene supercell and an L-serine molecule, it was found that a by-product hydroxyl group was formed by the dissociation of the −OH from the parental −COOH group and two covalent bonds forming at a couple of adjacent atoms on the graphene plane. The adsorption energy of the L-serine functionalization was weaker than that of the epoxy functionalization but was stronger than that of the hydroxyl functionalization. Electronic properties of this new L-serine functionalization were similar to epoxy functionalization at low functionalization density, as the Dirac cone was preserved with shifted wave vector due to the double sp³ vacancies. The C2v type of two-fold symmetry was observed through the local density of states (LDOS) and the gamma-point HOMO electron density analysis. However, the improved binding surface area of serine-functionalized graphene was observed, as four polar groups emerged from a single functionalization. Therefore, serine functionalization is a promising way to improve the properties of graphene-based electrodes.

Graphical abstract

中文翻译：

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与氧功能化相比，L-丝氨酸氨基酸功能化对石墨烯平面电子性能的影响。

通过密度泛函理论计算，研究了L-丝氨酸氨基酸功能化对石墨烯平面的影响，并与氧气功能化进行了比较。创建了3个4×4石墨烯超级电池系统，并通过环氧基，羟基和L-丝氨酸分子进行功能化。从包含4×4石墨烯超级电池和L-丝氨酸分子的系统的几何优化中，发现通过-OH与母体-COOH基团和两个共价键的解离形成了副产物羟基在石墨烯平面上的几个相邻原子上形成。L-丝氨酸官能化的吸附能弱于环氧官能化，但强于羟基官能化。^3个职位空缺。通过局部态密度（LDOS）和伽马点HOMO电子密度分析，观察到了C2v类型的两倍对称性。然而，观察到丝氨酸官能化的石墨烯的结合表面积得到了改善，因为单个官能化出现了四个极性基团。因此，丝氨酸功能化是改善石墨烯基电极性能的一种有前途的方法。

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