The STM Study Of The Controllable Fabrication Of 2D Self-assembled Nanostructures

Guest molecules can be entrapped in the empty pores selectively,which provide methods for fabricating and tuning molecular nanostructures.In this thesis,we have investigated controllable construction and tuning two-dimensional(2D)supramolecular networks by using scanning tunneling microscopy(STM)technique and density function theory(DFT)calculation.The main topics are as follows:Firstly,TCDB is exploited as a template molecule and(R)-BINOL derivatives and Ir-POMs molecule as the guest molecules,respectively.Two kinds of well-defined architectures are clearly observed when they are coadsorbed on HOPG,drawing a conclusion that the different sizes of the guest species result in different filling behaviors.Moreover,we investigate the surface adsorption and the corresponding self-assembly of ligand-metal complex,which can form relatively large area rectangle networks.This type of network cannot be used as templates to trap guest species,such as coronene.It is revealed that geometry and energy matching play essential roles in the construction of host-guest architectures.Secondly,the self-assembling of hexaphenylbenzene(HPB)derivatives is investigated by STM.Our STM results reveal that the target molecule,which forms snowflake-like structure on HOPG surface frequently,is transformed into honeycomb structure in response to selective guest molecule.The COR molecule-substrate interactions stabilize the honeycomb structure,while fullerenes are not strong enough to change the original host network structure.These results provide an insight into the interactions between guest molecule and the template and substrate,which leads to a better understanding of template-directed fabrication of functional molecular arrays.