Denis Pablo A
Computational Nanotechnology, DETEMA, Facultad de Química, UDELAR, CC 1157, 11800 Montevideo, Uruguay.
Phys Chem Chem Phys. 2015 Feb 21;17(7):5393-402. doi: 10.1039/c4cp05331a.
Herein, we employed first principle density functional periodic calculations to characterize the silicon counterpart of graphene:silicene. We found that silicene is far more reactive than graphene, very stable and strong Si-X bonds can be formed, where X = H, CH3, OH and F. The Si-F bond is the strongest one, with a binding energy of 114.9 kcal mol(-1). When radicals are agglomerated, the binding energy per functional grows up to 17 kcal mol(-1). The functionalization with OH radicals produces the largest alterations of the structure of silicene, due to the presence of intralayer hydrogen bonds. The covalent addition of H, CH3, OH and F to silicene enables the adjustment of its electronic structure. In effect, functionalized silicene can be a semiconductor or even exhibit metallic properties when the type and concentration of radicals are varied. The most interesting results were obtained when two layers of functionalized silicene were stacked, given that the band gaps experienced a significant reduction with respect to those computed for symmetrically and asymmetrically (Janus) functionalized monolayer silicenes. In the case of fluorine, the largest changes in the electronic structure of bilayer silicene were appreciated when at least one side of silicene was completely fluorinated. In general, the fluorinated side induces metallic properties in a large number of functionalized silicenes. In some cases which presented band gaps as large as 3.2 eV when isolated, the deposition over fluorinated silicene was able to close that gap and induce a metallic character. In addition to this, in four cases small gaps in the range of 0.1-0.6 eV were obtained for bilayer silicenes. Therefore, functionalization of silicene is a powerful method to produce stable two-dimensional silicon based nanomaterials with tunable optical band gaps.
在此，我们采用第一性原理密度泛函周期性计算来表征石墨烯的硅对应物：硅烯。我们发现硅烯的反应活性比石墨烯高得多，能够形成非常稳定且强的Si-X键，其中X = H、CH₃、OH和F。Si-F键是最强的，结合能为114.9 kcal mol⁻¹。当自由基聚集时，每个官能团的结合能增加到17 kcal mol⁻¹。由于层内氢键的存在，用OH自由基进行官能化会使硅烯的结构发生最大变化。H、CH₃、OH和F与硅烯的共价加成能够调节其电子结构。实际上，当自由基的类型和浓度发生变化时，官能化的硅烯可以是半导体，甚至表现出金属特性。当堆叠两层官能化硅烯时，获得了最有趣的结果，因为相对于对称和不对称（Janus）官能化的单层硅烯计算得到的带隙，其带隙显著减小。对于氟的情况，当硅烯的至少一侧完全氟化时，双层硅烯的电子结构变化最大。一般来说，氟化侧会在大量官能化硅烯中诱导出金属特性。在一些孤立时带隙高达3.2 eV的情况下，在氟化硅烯上沉积能够闭合该带隙并诱导出金属特性。除此之外，在四种情况下，双层硅烯获得了0.1 - 0.6 eV范围内的小带隙。因此，硅烯的官能化是一种制备具有可调光学带隙的稳定二维硅基纳米材料的有效方法。
