The Growth and Characterization of Alkylphosphonic Acid Self-Assembled Nanofibers

The focus of this research was to investigate the formation and properties of novel Self-Assembled Nanofibers (SANs) created by the treatment of Al with solutions of short chain-length alkylphosphonic acids (APAs) in ethanol. A special emphasis was placed on the creation of APA SANs isolated from the immersed Al source and development of analysis techniques for artifact reduced characterization of as-grown individual SANs. Novel immersion growth techniques were devised for the reproducible creation of supported and unsupported isolated methylphosphonic acid (C1), propylphosphonic acid (C3), and pentylphosphonic acid (C5) SANs on Si3N4 and Al coated ProtoChipsTM DuraSiNTM Si3N4 meshes respectively. Additionally, a novel biased immersion growth technique was developed, increasing growth rates as well as allowing for APA SAN deposition onto a variety of substrates including Au microelectrodes. A combination of complimentary analysis techniques including: Atomic force microscopy (AFM), Scanning Transmission Electron Microscopy (STEM), Energy Dispersive Spectrometry (EDS), X-Ray Photoelectron Spectroscopy (XPS), and Electron Energy Loss Spectroscopy (EELS) were utilized to characterize the morphology, composition and chemistry of isolated individual APA SANs. STEM and AFM revealed individual APA SANs are actually composed of layered fibril bundles. Qualitative compositional analysis showed APA SANs were primarily composed of O, C, P, and Al with P:Al ratios determined to be between 1.5 and 4.2. Quantitative XPS and EELS analysis provided further evidence that the detected Al was non-metallic and likely oxidized. STEM with EELS was utilized to definitively correlate the presence of Al, P, O, and C to a 5 nm region of several overlapping unsupported C1 SANs. Thermal analysis of APA SANs on Al as well as isolated on Si3N4 revealed a nearly 5X increase in thermal stability as compared to the ˜ 100C-120C melting points of pure APAs. AFM nanoindentation and nanoscratching were utilized to investigate the mechanical response of individual APA SANs. Evidence of cracking and layering were observed in good agreement with the STEM fibril observations. The reduced elastic modulus, E*, or stiffness, was estimated utilizing a Hertzian mechanics analysis of AFM nanoindentation data and determined to range from ˜ 10GPa to 1 GPa varying inversely with chain-length. Electric Force Microscopy (EFM) of C1 SANs revealed no evidence of conductivity as compared to a control sample consisting of Focused Ion Beam (FIB) deposited Pt nanowires on Si3N4. Additionally, Current-Voltage (IV) measurements were made on individual APA SANs deposited on Au microelectrodes again with no evidence of conductivity.

Author dc:creator

• Salmon, Michael Edward

Advisors dc:contributor.advisor

• Phillip Russell, Committee Chair
• Dieter Griffis, Committee Member
• John Mackenzie, Committee Member
• Richard Spontak, Committee Member

• nanofiber
• nanotechnology
• methylphosphonic acid
• stem
• phosphonic
• afm
• sem

Statement dc:rights

• I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.

Dc Identifier Other

etd-07102006-080152

OAI record oai:identifier

https://repository.lib.ncsu.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Arepository.lib.ncsu.edu%3A1840.16%2F3060