Co-assembly Of Carboxyl Derivatives And Amino Derivatives On Silver Surfaces

Molecular self-assembly on surface is the process of spontaneous formation of ordered supramolecular structures by molecule-molecule and molecule-substrate interactions.In recent years,many novel surface nanostructures were obtained by molecular self-assembly,with the potential to be applied in the field of the nano-device manufacturing and nano-material microfabrication technology.Molecular self-assembly is induced by several non-covalent interactions,such as dipole-dipole interactions,van der Waals interactions,?-? stacking and hydrogen bonding.Among the various intermolecular interactions,hydrogen bonding is considered to be one of the most intriguing force because of its directionality and widely presence in bio-systems.In particular,many studies have been focused on the self-assembly of carboxyl and amino derivatives due to their vital importance to the formation of proteins.As well as,carboxyl-amino hydrogen bonding are largely exist in the DNA double helix structure.Based on this,it is necessary to further study the co-assembly of carboxyl and amino derivatives on surfaces.Combining ultra-high vacuum scanning tunneling microscopy(UHV-STM),XPS and DFT theory calculation,three main research works were performed based on the well design of precursors and various experiment methods:1.In this work,by introducing 1,3,5-tris(4-carboxyphenyl)benzene(TCPB)and 4,4''-diamino-p-terphenyl(DATP)as precursors,the co-assembly behavior of carboxyl and amino derivatives were studied on metal surfaces.Firstly,we studied the self-assembly of the two percursors.Then,the co-assembly of two precusors were observed based on the characteristics of self-assembly.The STM experiments show that a series of TCPB self-assembly structures were formed on Ag(111)surface,and the structure transformations occurred with the increased annealing temperature.DFT theoretical calculations show that the structure transitions were induced by the deprotonation of the carboxyl group of TCPB.On the other side,DATP monomers move fastly on the Ag(111)surface at 77 K,suggesting a rather weak molecule-molecule and molecule-substrate interactions.The DATP monomers,however,can be stabilized and become visible at 77 K on the Ag(111)surfaces by interacting with TCPB monomers after co-deposition of DATP and TCPB on the Ag(111)surface.Therefore,a series of co-assembly structures were obtained on Ag(111)surface by through precisely regulating the annealing temperature,and the irreversible structure transition occurred with the deprotonation of carboxyl groups.2.According to the exploration above,we investigated the bicomponent co-assembly of carboxyl derivatives and amino derivatives continualy.In this work,4,4'-diphenylethylene dicarboxylic acid(SDBA)and 1,3,5-tris(4-amino phenyl)benzene(TAPB)were introduced as precursors.We firstly studied the self-assembly of SDBA and TAPB respectively on the Ag(111)surface.Combining the characteristics of the self-assembled structures,the co-assembly of SDBA and TAPB were studied on the Ag(111)surfaces.Based on the precisely regulating of the annealing temperature and the deposition proportion of SDBA and TAPB,a group of co-assembly networks with different configurations and proportions were obtained on Ag(111)surface.3.Carboxyl groups profoundly affect the configuration of co-assembled structures.Many supramolecular assembly networks with different geometry can be obtained by use of the diverse prescursors.Therefore,we intend to acquir the steerable long-range one-dimentional nanowires by designing the precurors with specific geometry.In this work,4,4'-diphenylethylene dicarboxylic acid(SDBA)and N,N'-diphenyl biphenyl diamine(DPB)were taken as precursors.One-dimentional co-assembled chain structures have been achieved on Ag(111)and Ag(100)surfaces,albeit with growth direction restricted to absence of the upholder.Then,the upholder was introduced as the auxiliary to induce the growth of the chain structure.The ideal steerable long-range one-dimentional nano structures were achieved on Ag(110)surface.