Atomic Scale Investigation On The Interactions Between Amino Acids And Metallic Atoms By Scanning Tunneling Microscopy

The amino acid is the building block of the biomacromolecules,proteins.The amino acid in living organisms are often combine with metallic atoms through coordination bonds or ionic bonds to form various complex with special functions,which play the role of structure maintenance,function and regulation in a variety of important proteins.In addition,the coordination nanostructures formed by amino acids and metal atoms have received widespread attention due to its potential applications in biomaterials.Therefore,study on the interactions between amino acids and metal atoms may help understand the role and mechanism of metal in specific biological processes.The non planar spatial configuration of natural amino acids makes it difficult to accurately characterize the interaction between amino acids and metal atoms at atomic scale,in this paper,we chose the amino acid molecule ANA,which is approximately planar in structure,by the combination of scanning tunneling microscopy imaging,X-ray photoelectron spectroscopy analysis and density functional theory calculations,we have investigated the interactions between the amino acid molecule ANA and iron atoms and copper atoms at the atomic scale.As one of the most important trace elements in human bodys with high content,iron plays important roles on the construction of many proteins.In Chapter 3 and Chapter 4,we have investigated the interactions between the ANA molecule and iron atoms on both Au(111)and Ag(111).We find that the introduction of iron atoms could induce the dehydrogenation behavior of carboxyl groups of ANA molecules and further coordinate with the dehydrogenated carboxyl groups.Further,the varying surface coverage,ANA molecules/iron atoms ratios as well as the substrates could cause totally distinct metal-organic coordination nanostructures possibly due to the flexible coordination configuration of dehydro carboxyl groups and the competition between the coordination bond and the hydrogen bond.However,it should be noted that,despite the distinct coordination nanostructures of dehydrogenated carboxyl group of ANA molecules with the iron atoms,the iron atom themselves always coordinate with four oxygen atoms.Copper is another essential metal element for our human body.In Chapter 5 and Chapter6,we have investigated the interactions between the ANA molecule and copper atoms on Cu(111)and Cu(110).We find that copper atoms could induce dehydrogenation of both carboxyl and amino groups of ANA molecules after annealing.However,different from that of iron atoms,copper atoms tend to coordinate with the dehydrogenated amino groups rather than dehydrogenated carboxyl groups,indicating different sites for coordination priority of copper atoms and iron atoms with ANA molecules.On the Cu(111),the coverage has little influence on their coordination configuration and nanostructure,and all of the coordination centers are mono-copper centers.In comparison,distinct surface coverage on Cu(110)could cause the coordination center from a mono-/bi-copper centers to pure mono-copper centers.Moreover,the coordination nanostructure has been changed from a quasi-ordered to highly ordered one,and the arrangement of copper coordination centers on the surface has been simultaneously modulated.These results are helpful to study the interaction between amino acids and different metals,and provides a new insights for the controlled fabrication of new-type single atom catalysts.