ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- All Subjects: Diatoms
- Creators: Goryll, Michael
Description
Biogenic silica nanostructures, derived from diatoms, possess highly ordered porous hierarchical nanostructures and afford flexibility in design in large part due to the availability of a great variety of shapes, sizes, and symmetries. These advantages have been exploited for study of transport phenomena of ions and molecules towards the goal of developing ultrasensitive and selective filters and biosensors. Diatom frustules give researchers many inspiration and ideas for the design and production of novel nanostructured materials. In this doctoral research will focus on the following three aspects of biogenic silica: 1) Using diatom frustule as protein sensor. 2) Using diatom nanostructures as template to fabricate nano metal materials. 3) Using diatom nanostructures to fabricate hybrid platform.
Nanoscale confinement biogenetic silica template-based electrical biosensor assay offers the user the ability to detect and quantify the biomolecules. Diatoms have been demonstrated as part of a sensor. The sensor works on the principle of electrochemical impedance spectroscopy. When specific protein biomarkers from a test sample bind to corresponding antibodies conjugated to the surface of the gold surface at the base of each nanowell, a perturbation of electrical double layer occurs resulting in a change in the impedance.
Diatoms are also a new source of inspiration for the design and fabrication of nanostructured materials. Template-directed deposition within cylindrical nanopores of a porous membrane represents an attractive and reproducible approach for preparing metal nanopatterns or nanorods of a variety of aspect ratios. The nanopatterns fabricated from diatom have the potential of the metal-enhanced fluorescence to detect dye-conjugated molecules.
Another approach presents a platform integrating biogenic silica nanostructures with micromachined silicon substrates in a micro
ano hybrid device. In this study, one can take advantages of the unique properties of a marine diatom that exhibits nanopores on the order of 40 nm in diameter and a hierarchical structure. This device can be used to several applications, such as nano particles separation and detection. This platform is also a good substrate to study cell growth that one can observe the reaction of cell growing on the nanostructure of frustule.
Nanoscale confinement biogenetic silica template-based electrical biosensor assay offers the user the ability to detect and quantify the biomolecules. Diatoms have been demonstrated as part of a sensor. The sensor works on the principle of electrochemical impedance spectroscopy. When specific protein biomarkers from a test sample bind to corresponding antibodies conjugated to the surface of the gold surface at the base of each nanowell, a perturbation of electrical double layer occurs resulting in a change in the impedance.
Diatoms are also a new source of inspiration for the design and fabrication of nanostructured materials. Template-directed deposition within cylindrical nanopores of a porous membrane represents an attractive and reproducible approach for preparing metal nanopatterns or nanorods of a variety of aspect ratios. The nanopatterns fabricated from diatom have the potential of the metal-enhanced fluorescence to detect dye-conjugated molecules.
Another approach presents a platform integrating biogenic silica nanostructures with micromachined silicon substrates in a micro
ano hybrid device. In this study, one can take advantages of the unique properties of a marine diatom that exhibits nanopores on the order of 40 nm in diameter and a hierarchical structure. This device can be used to several applications, such as nano particles separation and detection. This platform is also a good substrate to study cell growth that one can observe the reaction of cell growing on the nanostructure of frustule.
ContributorsLin, Kai-Chun (Author) / Ramakrishna, B.L. (Thesis advisor) / Goryll, Michael (Thesis advisor) / Dey, Sandwip (Committee member) / Prasad, Shalini (Committee member) / Arizona State University (Publisher)
Created2014
Description
The hierarchical silica structure of the Coscinodiscus wailesii diatom was studied due to its intriguing optical properties. To bring the diatom into light harvesting applications, three crucial factors were investigated, including closely-packed diatom monolayer formation, bonding of the diatoms on a substrate, and conversion of silica diatom shells into silicon.
The closely-packed monolayer formation of diatom valves on silicon substrates was accomplished using their hydrodynamic properties and the surface tension of water. Valves dispersed on a hydrophobic surface were able to float-up with a preferential orientation (convex side facing the water surface) when water was added. The floating diatom monolayer was subsequently transferred to a silicon substrate. A closely-packed diatom monolayer on the silicon substrate was obtained after the water evaporated at room temperature.
The diatom monolayer was then directly bonded onto the substrate via a sintering process at high temperature in air. The percentage of bonded valves increased as the temperature increased. The valves started to sinter into the substrate at 1100°C. The sintering process caused shrinkage of the nanopores at temperatures above 1100°C. The more delicate structure was more sensitive to the elevated temperature. The cribellum, the most intricate nanostructure of the diatom (~50 nm), disappeared at 1125°C. The cribrum, consisting of approximated 100-300 nm diameter pores, disappeared at 1150°C. The areola, the micro-chamber-liked structure, can survive up to 1150°C. At 1200°C, the complete nanostructure was destroyed. In addition, cross-section images revealed that the valves fused into the thermally-grown oxide layer that was generated on the substrate at high temperatures.
The silica-sintered diatom close-packed monolayer, processed at 1125°C, was magnesiothermically converted into porous silicon using magnesium silicide. X-ray diffraction, infrared absorption, energy dispersive X-say spectra and secondary electron images confirmed the formation of a Si layer with preserved diatom nano-microstructure. The conversion process and subsequent application of a PEDOT:PSS coating both decreased the light reflection from the sample. The photocurrent and reflectance spectra revealed that the Si-diatom dominantly enhanced light absorption between 414 to 586 nm and 730 to 800 nm. Though some of the structural features disappeared during the sintering process, the diatom is still able to improve light absorption. Therefore, the sintering process can be used for diatom direct bonding in light harvesting applications.
The closely-packed monolayer formation of diatom valves on silicon substrates was accomplished using their hydrodynamic properties and the surface tension of water. Valves dispersed on a hydrophobic surface were able to float-up with a preferential orientation (convex side facing the water surface) when water was added. The floating diatom monolayer was subsequently transferred to a silicon substrate. A closely-packed diatom monolayer on the silicon substrate was obtained after the water evaporated at room temperature.
The diatom monolayer was then directly bonded onto the substrate via a sintering process at high temperature in air. The percentage of bonded valves increased as the temperature increased. The valves started to sinter into the substrate at 1100°C. The sintering process caused shrinkage of the nanopores at temperatures above 1100°C. The more delicate structure was more sensitive to the elevated temperature. The cribellum, the most intricate nanostructure of the diatom (~50 nm), disappeared at 1125°C. The cribrum, consisting of approximated 100-300 nm diameter pores, disappeared at 1150°C. The areola, the micro-chamber-liked structure, can survive up to 1150°C. At 1200°C, the complete nanostructure was destroyed. In addition, cross-section images revealed that the valves fused into the thermally-grown oxide layer that was generated on the substrate at high temperatures.
The silica-sintered diatom close-packed monolayer, processed at 1125°C, was magnesiothermically converted into porous silicon using magnesium silicide. X-ray diffraction, infrared absorption, energy dispersive X-say spectra and secondary electron images confirmed the formation of a Si layer with preserved diatom nano-microstructure. The conversion process and subsequent application of a PEDOT:PSS coating both decreased the light reflection from the sample. The photocurrent and reflectance spectra revealed that the Si-diatom dominantly enhanced light absorption between 414 to 586 nm and 730 to 800 nm. Though some of the structural features disappeared during the sintering process, the diatom is still able to improve light absorption. Therefore, the sintering process can be used for diatom direct bonding in light harvesting applications.
ContributorsRojsatien, Srisuda (Author) / Goryll, Michael (Thesis advisor) / Alford, Terry (Thesis advisor) / Theodore, David (Committee member) / Arizona State University (Publisher)
Created2018