Fabrication And Charicterization Of One-Dimensional Nanomaterials Based On DNA-template And Self-assembly Technology

A significant challenge in integrating nanoscale building blocks into functional nanodevices or circuits is finding parallel,cost-effective,and simple methods of assembling the nanostructures,such as nanoparticle,nanowire and nanotube.With the size of nanodevices shrinking,it has become quite clear that the conventional "top-down" approaches are beset with many difficulties,such as more complicated techniques,higher cost and even some fundamental physical limitations.This state of affairs has led to great interest in the development of new methodologies based on "bottom-up" approaches.In particular,DNA has already been extensively used to construct various nanostructures and nanodevices recently,due to its unique properties including intermolecular and intramolecular recognition,special chemical structure,mechanical rigidness and nanoscale diameter.The self-assembly technology of nanowires based on the DNA template has been widely demonstrated by a great deal of researchers and their potential applications for the functional nanodevices or circuits were also been explored.The main contents of the dissertation can be summarized as follows:In Chapterâ… ,we first introduced briefly the development history of nanomaterials and nanodevices.Then,we described some important applications of nanotechnologies in biology area.Finally,the motivation and main contents of this dissertation were summarized.In Chapterâ…¡,we have developed a simple,yet highly effective and reliable, poly(dimethylsiloxane)(PDMS) transfer method to fabricate highly dense and well-aligned CdS nanowires on silica substrates,following DNA templates.This method combined DNA combing technique,nanotransfer-printing and photochemical reaction techniques.CdS nanoparticles are selectively deposited and confined on DNA strings aligned on a PDMS sheet to form CdS nanowires.The nanowires are then transferred to the substrate with a low occurrence of parasitic CdS nanoparticles. The width and length of the nanowires can be controlled by adjusting the incubation time on the PDMS sheet.Lastly,theâ… -â…¤measurement of the CdS nanowire was also performed.In Chapterâ…¢,we fabricated Pd nanowires respectively by three different methods:direct method on mica surface,photochemical method in aqueous solution and PDMS-transfer method in ethanol solution.The morphologies,diameters,density and continuity of the Pd nanowires synthesized by three methods were carefully investigated and characterized.It was found that the Pd nanowires fabricated by the PDMS-transfer method in ethanol solution had thick diameter,long length,dense density,low numbers of parasitic CdS nanoparticles on the surface and high conductance.In addition,the growth mechanics related to the method was also proposed.In Chapterâ…£,we demonstrated that a palladium chloride aqueous solution, mixed with a proper ammonia solution,could produce Tetra-amminepalladous chloride(Pd(NH₃)₄Cl₂·H₂O) nanowires.These nanowires can spontaneously form the two-dimensional hexagon-oriented Pd(NH₃)₄Cl₂·H₂O arrays on mica surfaces.We can control the length and height of these nanowires by adjusting their deposit time on the mica substrate.In addition,we developed a simple,effective method,based on the self-assembly of TAA on Cd(Ac)₂ film,to fabricate thick,luminescent CdS nanowires on mica surface.In Chapterâ…¤,we proposed a method to construct DNA-templated nanodevice based on the interaction between biotin and streptavidin.Au microelectrodes with 4μm gap were fabricated by deep UV lithography and the biotin labeled DNA with about 20k b.p.length was synthesized by PCR method.Through self-assembly approach,the streptavidin molecules were first assembled on the Au film and then the biotin-DNA molecules were assembled on the streptavidin layer.The assembly processes were carefully characterized by QCM-D technique and the corresponding mechanisms were also discussed.