First-principles study of l-cysteine adsorption on vacancy graphene and Ag-doped graphene

•Influences of the vacancy type and the Ag dopant on l-cysteine adsorption are investigated.•The dangling C atom is warped for stable chemisorption in vacancy graphenes.•Two-step energy barrier leads to different adsorption types and adsorption energies.•Room temperature application potential is explored.

The understanding of interactions between graphene and biomolecules is of fundamental relevance to the area of nanobiotechnology. Herein, taking l-cys as the probe molecule, its adsorptions on single-vacancy graphene (SV), double-vacancy graphene (DV), Ag doped single-vacancy graphene (AgSV) and Ag doped double-vacancy graphene (AgDV) were investigated using first-principles calculations. SV and AgSV exhibit exothermical chemisorptions while AgDV exhibits endothermical chemisorptions towards l-cys, regardless of the end type. DV shows exothermical chemisorption towards S-end l-cys and endothermical physisorption towards O-end and N-end l-cys. Two-step energy barrier related to initial symmetry broken and structural reorganization leads to differences in adsorption types and adsorption energies. Site-specific immobilization was also revealed. Calculations at 298.15 K and 1 atm reveal that l-cys adsorptions on SV, AgSV, the S-end, O-end adsorptions on DV are thermodynamically favourable. The results could provide guidance for further choice of graphene in bionanotechnological applications.

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