STM Investigation Of Molecule Self-assembly And Chiral Reaction On Au(111)

Molecule self-assembly is a spontaneous process in the formation of well-ordered structures by non-covalent interactions between absorbed molecules.Researches of molecule self-assembly have been widely applied in the field of bio-engineering,new materials,molecule devices,as well as nano technology.Since the driving forces of self-assembly are weak non-covalent interactions,self-assembled structures have a relatively low thermal stability,which limits its further application.Besides spontaneously formed structure can be hard to control.On the other hand,surface chemical reactions show potential applications in surface catalysis,controllable preparation and reaction mechanism of functional macro-molecules.In light of this,problem remains in combining the advantages of self-assembly and surface reactions so as to improve the stability of self-assembled structures as well as to build a new functional covalently connected system.My main researches are listed below:1 STM study of condition-controlled PTCDA/NaCl self-assembly on Au(111)Perylenetetracarboxylic dianhydride(PTCDA)can form well-ordered hexagonal and square structures through self-assembly on Au(111).We introduced NaCl to the process and deposited NaCl monolayer before the deposition of PTCDA.The self-assembly structures were greatly changed with the participation of NaCl.Different sequence of molecule adsorption will lead to different self-assembly behavior as well as electronic property,which provides valuable information for the application of PTCDA in the field of organic thin film.2 Chirality transfer from self-assembled structures to oligomersUsing achiral molecules 1,4-dibromo-2,5-ditridecylbenzene(13DB)as precursors,the induction of chirality on Au(111)surface was investigated.13DB molecules adsorb flatly on surface,with alkyl chains mutually crosswise arranged,and benzene rings close-packed,causing a symmetry breaking and chiral assembly on Au(111).STM investigation reveals that chirality property remains in oligomers after aryl-aryl coupling reaction,which derives from its original chirality.The creation of homochiral domains inspires the controllable preparation of chiral structures on surface.3 Effect of polymerization degree by alkyl chain length in chiral reactionThe self-assembly behavior and aryl-aryl coupling reaction of chiral molecules 1,4-dibromo-2,5-dioctylbenzene(8DB)and 1,4-dibromo-2,5-didecylbenzene(10DB)is similar to that of 13DB.Polymerization degree of 8DB and 10DB was found to have been improved due to the shorter alkyl chains,which enlightens organic reactions demanding higher productivity as well as polymerization degree.