Chemical Templating by AFM Tip-directed Nano-electrochemical Patterning.

摘要

This work has examines the creation and use of chemical templates for nanocircuit and other nanodevice fabrication. Chemical templating can be useful in attachment, orientation and wiring of molecularly templated circuits. DNA origami provides a suitable method for creating molecularly templated circuits as DNA can be folded into complex shapes and functionalized with active circuit elements, such as semiconducting nanomaterials. Surface attachment of DNA origami structures can be accomplished by hybridization of dangling single-stranded DNA (ssDNA) on the origami structures with complementary surface-bound strands. Chemical templating provides a pathway for placing the patterned surface-bound attachment points needed for surface alignment of the molecular templates. Chemical templates can also be used to connect circuit elements on the surface by selectively metallizing the templates to form local wiring. AFM tip-directed nano-oxidation was selected as the method for patterning to create chemical templates. This project demonstrates new techniques for creating, continuous metallization of, and DNA attachment to nanochemical templates.;Selective-continuous metallization of nanochemical templates is needed for wiring of circuit templates. To improve the metallization density and enable the continuous nano-scale metallization of amine-coated surfaces, the treatment of amine-coated surfaces with a plating additive prior to metallization was studied. The additive treatment resulted in a 73% increase in seed material, enabling continuous nano-scale metallization. A new method was developed to create amine nanotemplates by selective attachment of a polymer to surface oxide patterns created by nano-oxidation. The treatment of the templates with the additive enabled a five-fold reduction in feasible width for continuous metallization. Nano-oxidation was also used in the nanometer-scale patterning of a thiol-coated surface. Metallization of the background thiols but not the oxidized patterns resulted in a metal film that was a negative of the patterns. The resulting metal film may be useful for nanometer-scale pattern transfer.;DNA-coated gold nanoparticles (AuNPs) were selectively attached to amine templates by an ionic interaction between the template and ssDNA attached to the particles. Only the ssDNA on the bottom of the AuNPs interacted with the template, leaving the top strands free to bind with complementary ssDNA. Attempts to attach origami structures to these particles were only marginally successful, and may have been hindered by the presence of complementary ssDNA in solution but not attached to the origami, or the by the low density of DNA-AuNPs attached to the templates. The formation of patterned binding sites by direct, covalent attachment of ssDNA to chemical templates was also explored. Initial results indicated that ssDNA was chemically bound to the templates and able to selectively bind to complementary strands; however, the observed attachment density was low and further optimization is required. Methods such as these are needed to enable nano-scale, site-specific alignment of nanomaterials.