Bioinspired nanoarchitecture: Nanofabrication of two-dimensional metallic and semiconductor arrays using microbial surface layer (S-layer) protein biotemplates

• Main Author: Mark, Sonny S
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2006
• Subjects: Microbiology
• ISBN: 0542927497; 9780542927492

By organizing structures such as nanoparticles and nanowires/pillars into two-dimensional (2-D) arrays, it has been shown that novel properties of these materials can often arise due to cooperative effects. Thus, the creation of highly ordered structures on nanometer-length scales is an area of much active research, and is expected to be crucial for the development next-generation optical, electronic, and magnetic devices. However, since the fabrication of ordered arrays with feature spacings in the sub-50 nm size range is not trivial using conventional lithographic processes, one has to look towards alternative methods. One possibility, explored in this dissertation, is to exploit the intrinsic periodic properties of naturally occurring biological structures known as surface layer ('S-layer') proteins. S-layers are highly ordered, self-assembling 2-D biological nanostructures displaying repeating features and pores in the size range 2-8 nm, with spacings of 3-30 nm. In this thesis work, S-layer protein lattices isolated from the Gram-positive bacterium Deinococcus radiodurans (HPI) and the acidothermophilic archaeon Sulfolobus acidocaldarius (SAS) were examined for their ability to biologically program the formation of self-assembled, ordered arrays of inorganic nanostructures. Using the HPI and SAS S-layers, the influences of particle properties, surface chemistry, and solution adsorption conditions on the formation of ordered arrays of metallic and dendrimer-encapsulated nanoparticles were investigated. For the generation of semiconductor nanoparticle arrays, CdSe/ZnS core/shell quantum dots (QDs) were functionalized with different types of thiol ligands in order to render them hydrophilic and thus water-soluble. Transmission electron microscopy (TEM), Fourier transform analyses, and pair correlation function (PCF) calculations revealed that ordered QD arrays with a range of nanometric spacings and different geometrical arrangements could be bionanofabricated. Finally, the results of initial efforts to utilize S-layers as nanolithographic masks for the fabrication of vertically aligned carbon nanostructures and silicon nanopillars are discussed. Overall, the findings presented in this dissertation demonstrate that it is possible to exploit the physicochemical/structural diversity of S-layer proteins to vary the morphological patterning of arrays of metallic and semiconductor nanomaterials.