| In this thesis work, an operationally simple, reliable, and inexpensive methodology of patterning a wide variety of materials on the micron and nano-scale has been developed. This methodology relies on the selective wetting of materials on substrates modified with self-assembled monolayers (SAMs). Well-established techniques such as microcontact printing and dip-pen nanolithography (DPN) have been used to pattern SAMs of alkanethiols and silanes on gold and silicon oxide surfaces, respectively. Microcontact printing, a soft lithographic technique, uses a patterned PDMS stamp, whereas, DPN uses a functionalized AFM tip to pattern materials on surfaces. The patterned SAMs of alkanethiols and silanes have been used as templates for selective deposition of various materials. Initial work has been performed with block copolymers. It has been demonstrated that a mainly hydrophilic block copolymer selectively wets regions covered with hydrophilic SAMs whereas a mainly hydrophobic block copolymer selectively wets hydrophobic regions. This patterning technique has been extended to biomaterials and conjugated oligomers. It has been demonstrated that the methodology has no limitations with respect to molecular weights of the patterned materials, since materials ranging from oligomers to high molecular weight polyamino acid have been patterned.; In a separate but related project, thermal stabilities of alkanethiol and silane SAMs have been compared using X-ray photoelectron spectroscopy and it has been demonstrated that silane SAMs are more thermally stable than alkanethiol SAMs. It has also been shown that silane SAMs can also be used as templates for patterning materials, which may be used for high temperature applications.; In a third project, ultraviolet photoelectron spectroscopy and electron energy loss spectroscopy have been successfully used to evaluate the conjugation lengths of short-chain oligothiophenes.; Finally, chemical sensors based on alkanethiol monolayer protected gold nanoparticles have been fabricated by spin coating their solutions onto interdigitated array microelectrodes. For this purpose, gold nanoparticles functionalized with methyl- and o-thienyl-terminated alkanethiols, with different chain lengths, have been synthesized. Exposure of the films to chloroform, toluene, hexane, and ethanol vapors results in significant increases in electrical resistance of these films. The magnitude of the maximum resistance change correlates well with solubility properties of the protected gold nanoparticles, as determined by optical absorbance spectroscopy and the energy of the gold plasmon. The detection sensitivity of the films increases with increasing alkanethiol chain length. These data are consistent with a sensing mechanism in which organic vapors cause swelling of the nanoparticle film, resulting in increased distance between the gold cores. In principle, these chemical sensors can be made selective by having an array of gold nanoparticles functionalized with different alkanethiols. This may be done by patterning gold nanoparticles using the methodology developed in this thesis. |
