5 years ago

Adsorption patterns of aromatic amino acids on monolayer MoS2 and Au-modified MoS2 surfaces: A first-principles study

Adsorption patterns of aromatic amino acids on monolayer MoS2 and Au-modified MoS2 surfaces: A first-principles study
As a pioneering non-graphene material, two dimensional, single-layered molybdenum disulfide (MoS2) has achieved outstanding performance in biosensor research in recent years. However, either reliable exploitation of bio-applications or keeping eyes on biological safety requires clear understanding of the linkage between the MoS2 surface and the biological elementary blocks, such as amino acids. In this manuscript, first-principles density functional theory (DFT) was employed to investigate the adsorption behaviors of aromatic amino acids, phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp), on monolayer pristine MoS2 and Au-modified MoS2 surfaces. Optimal adsorption configurations of amino acids on different surfaces were predicted by adsorption energy calculation. The calculations indicate that three amino acids can be physically adsorbed on pristine MoS2 surface by parallel interaction between the aromatic ring and surface S atoms, which is consistent with previous work. On the Au-modified surface, amino acids demonstrate a coexistence of chemisorption and physisorption through covalent linkage to Au atom and no-covalent interaction to the sheet respectively. And the adsorption energies are almost twice as large as that of on a pure MoS2 surface. Yet there is a same adsorption ability order Trp>Tyr>Phe on both surfaces. By comparing changes in molecular geometry before and after adsorption, it is found that the structure influences of amino acids induced from both surfaces adsorption are limited. The DOS and PDOS analysis show that amino acids adsorption can modify the electronic properties of substrates through π-p interaction and other electronic interactions. Especially, amino acids with Au linker can transform p-type semiconductor of MoS2 into a n-type one. Our calculations clarify the sensitivity of intrinsic MoS2 and Au-modified MoS2 surfaces to Phe, Tyr and Trp in a waterless environment and demonstrate their fleshed-out interaction patterns. The results provide a first-hand theoretical reference for their potential bio-nanotechnical applications of both MoS2 and Au-modified MoS2 materials.

Publisher URL: www.sciencedirect.com/science

DOI: S2210271X17303948

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