The Preparation Of Porphyrin Axial-coordination Lattices And Nanographanes

The precision that can be achieved by conventional micro-nanometer scale processing technologies,the so-called"top-down"method of processing devices,has gradually approached the physical limit.Compared with the top-down method,the bottom-up method features important advantages,such as tailored-made synthesis and processing down to the nanometer scale via self-assembly.In essence,self-assembly leverages the interaction between precursor molecules to allow small molecules to spontaneously form higher-dimensional structures such as long chains and molecular layers.By controlling the conditions and with suitable chemical precursors,self-assembly methods can be used to precisely build down to the atomic level.The selection of suitable precursor molecules is an important part of constructing nanostructures.Although there have been many studies on porphyrin-ligand coordination,the precision of three-dimensional heterostructures is difficult to control at the level of monolayers.Based on this,we investigate the synthesis of two different kind of 3D material.This research was based on the building of two ultra-high vacuum systems.By optimization,the system has greater functions comparing with the commercial systems.The systems combine instrumentation such as atomic force microscopy,scanning tunneling microscopy,time-of-flight mass spectrometry,and a Raman spectrometer,with unique capabilities to characterize and study the two new classes of materials introduced in this thesis.Porphyrins are a class of unique light-responsive molecules that easily form complexes with metals by axial coordination.Here we demonstrate prototypical axial coordination lattices via the controlled growth of iron porphyrins with DABCO.Specfically,an iron porphyrin(Fe OEP)molecular layer was precisely prepared on Au(111)substrate by molecular beam epitaxy and temperature-programmed desorption method.The morphology was characterized by scanning tunneling microscopy and atomic force microscopy.Then we apply the interaction between the complex and the organic small molecule,a monolayer organic small molecule DABCO was assembled on the monolayer Fe OEP molecule by temperature control again to form an axial-coordination lattice,and then the Fe OEP was accurately assembled by the layer-by-layer growth method.The three-dimensional heterostructure of Fe OEP-DABCO-Fe OEP provides a very promising platform for exploring physics at the nanoscale and new generation of optoelectronics.Growth in the third dimension can be also achieved by stacking of nanographene materials.Such materials are cutouts of graphene.In principle,stacks of nanographene could be covalently stabilized by hydrogenation.The hydrogenation of graphene yields a new class of material dubbed graphanes,which may have ferromagnetic,superconducting potential and it also has high value in hydrogen storage and functional devices.The hydrogenation of graphene is limited by the proportion of hydrogenation via top-down methods.Here we show that prototypical nanographenes can be fully hydrogenated en route toward the formation of three-dimensional nanodiamonds from stacks of nanographenes.Specifically,we combined the bottom-up method and the bottom-up method together:After the HBC multi-layer molecules were grown on the Au(111)substrate by molecular beam epitaxy,the hydrogenation method was carried out by two different hydrogenation methods:atomic hydrogen source and plasma hydrogen source.Raman data showed that both hydrogenation methods promoted the conversion of sp~2 carbon to sp~3 carbon in the HBC molecule,and further time-of-flight mass spectrometry characterization detected a product with a mass equal to nanographane,indicating that HBC was the fully hydrogenation to nanographane.And plasma hydrogenation is more efficient than atom hydrogen source hydrogenation.The simulation calculation of the system also shows that high temperature hydrogen atoms can add to HBC molecules and complete hydrogenation of HBC molecules,and when the free HBC molecules and semi-chair HBC molecules are hydrogenated together,it may promote the synthesis of nanodiamonds from two nanographanes.This presents a future possibility for the synthesis of nanodiamonds.