The Self-assembly Structure Of Bioorganic Micromolecule: Atomic Force Microscopy Study

The invention of scanning tunneling microscopy (STM) in 1982 enabled people to observe and study hylic world in atomic scale of real space for the first time. SPM have achieved lager number of accomplishment in many field of physics and chemistry. It can not only resolve the atomic structure of law dimensional material, but also manipulate atom or molecule and construct nanostructures. In this dissertation, the invention and development of scanning probe microscopy (SPM) and its application in Self-assembled Monolayers (SAMs) systems have been reviewed. Atomic Force Microscopy (AFM) and spectroscopy have been used to study self-assembly structures of different bioorganic molecules on various substrate, the main results are as follows:1. Synthesis of CdS nanoparticles based on DNA network templates was investigated. UV–vis spectroscopy, photoluminescence, x-ray diffraction and atomic force microscopy (AFM) were used to characterize the CdS nanoparticles in detail. AFM results showed that the resulted CdS nanoparticles were directly aligned on the DNA network templates and that the synthesis and assembly of CdS nanoparticles was realized in one step. CdS nanoparticles fabricated with this method were smaller than those directly synthesized in a thiourea solution and were uniformly aligned on the DNA networks. By adjusting the density of the DNA networks and the concentration of Cd2+, the size and density of the CdS nanoparticles could be effectively controlled and CdS nanoparticles could grow along the DNA chains into nanowires.2. The structure of self-assembled monolayers of the type ? collagen on mica and HOPG substrates were studied by AFM. The effects of the concentration, the temperature, and the ionic strength of the collagen solution on the formed structure were all investigated in detail. And it is found that type ? collagen with low concentration was adsorbed with simple structure on surface, but they would aggregate into fibers with the increased concentration.3. The structure of nanoporous thin films of PDDA and DNA fabricated on a polyaniline (PANI)-modified mica surface by using droplet addition and electrostatic self-assembly has been successfully studied by AFM. The results showed that homogeneous large DNA networks could be formed with the proposed method, and the stability of the DNA networks could be improved with the addition of PDDA molecules. The possible adsorption mechanism was also investigated.