Identifier

etd-04122013-194031

Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

Particle lithography and scanning probe lithography were applied to study the kinetics and mechanisms of surface self-assembly processes. Organothiols on Au(111) and organosilane on Si(111) were chosen as model systems for investigations at the nanoscale using atomic force microscopy (AFM). Fundamental insight of structure/property interrelationships and understanding the properties of novel materials are critical for developments with molecular devices. Methods using an AFM probe for nanofabrication have been applied successfully to prepare sophisticated molecular architectures with high reproducibility and spatial precision. The established capabilities of AFM-based nanografting were reviewed for inscribing patterns of diverse composition, to generate complicated surface designs with well-defined chemistries. Nanografting provides a versatile tool for generating nanostructures of organic and biological molecules, as well as nanoparticles. Protocols of nanografting are accomplished in liquid media, providing a mechanism for introducing new reagents for successive in situ steps for 3-D fabrication of designed nanopatterns. Because so many chemical reactions can be accomplished in solution, there are rich possibilities for chemists to design studies of other surface reactions. Surface assembly and self-polymerization of chloromethylphenyltrichlorosilane (CMPS) were investigated using test platforms of organosilanes fabricated with particle lithography. A thin film of octadecyltrichlorosilane (OTS) with well-defined nanopores was prepared on Si(111) to spatially confine the surface assembly of CMPS within nanopores of OTS. Time-dependent changes during the self-polymerization of CMPS was visualized ex situ using AFM. Molecular-level details of CMPS nanostructures were obtained from high resolution AFM images to track the growth of organosilanes on Si(111). Measurements of the heights and diameters of CMPS nanostructures provided quantitative information of the kinetics of CMPS self-polymerization. Scanning probe-based methods of nanolithography were applied to investigate the self-assembly of a tridentate organothiol, 1,1,1-tris(mercaptomethyl)heptadecane (TMMH). Multidentate adsorbates can address problems with long-term stability to oxidation observed with monothiolated n-alkylthiols. Multidentate thiol ligands demonstrate improved resistance to oxidation, thermal desorption and UV exposure. Progressive changes in surface morphology for TMMH assembly onto Au(111) was studied in situ with time-lapse AFM, monitoring changes in surface coverage at different time intervals. Nanoshaving and nanografting were used as molecular rulers to evaluate the thickness of films of TMMH.

Date

2013

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Garno, Jayne

DOI

10.31390/gradschool_dissertations.2396

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