Phenol-modified silicene: preferred substitution site and electronic properties

Silicon nanosheets (or multilayer silicene) are one of the most exciting recent discoveries, being a two-dimensional form of silicon that is less than a nanometer thick, with large lateral dimensions. It has been shown previously that organo-modified silicene can be synthesized with phenyl groups covalently bonded to both sides of the nanosheet, with hydrogen atoms terminating the undercoordinated silicon atoms (J. Am. Chem. Soc. 2010, 132, 5946-5947; Phys. Chem. Chem. Phys. 2011, 13, 15418-15422). In this work, we use density functional theory calculations and ab initio molecular dynamics (MD) simulations to determine the effect of hydroxyl (OH) group substitution on the phenyl-modified silicene. We show that van der Waals forces need to be included in the simulation to represent the interactions between the groups on the nanosheet. Different positions of the OH groups on the phenyl rings were modeled including ortho-, meta-, and para-substituted positions. The para-substituted position was favored, followed by the meta- then ortho-substituted positions. Our ab initio MD simulations showed that the phenol groups will freely rotate on the nanosheet, aligning so as to form hydrogen bonds between adjacent phenol groups. Such a property may allow the material to be soluble in aqueous solutions, extending its application areas.