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Title: Biological applications of functional micro-/nano-structures
Other Titles: Wei na mi jie gou de gou jian ji qi sheng wu xue ying yong
Authors: Zhang, Wenjun (張文軍)
Department: Department of Physics and Materials Science
Degree: Doctor of Philosophy
Issue Date: 2010
Publisher: City University of Hong Kong
Subjects: Nanotechnology.
Notes: CityU Call Number: TP248.25.N35 Z45 2010
xix, 169 leaves : ill. 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references.
Type: thesis
Abstract: With shrinking dimensions, materials possess very different properties compared to their bulk counterparts. This provides the incentives to scientific researchers to investigate their properties and develop novel applications. Owing to the proven excellent performance of micro/nano- structures such as controllable release of ions from buried nano-scaled thin layers, cell response to micro-scaled morphological changes of substrates, enhanced sensitivity rendered by electrodes with sizes less than 10 micrometers, and dramatically increased electromagnetic field from local surface plasmon resonance of nanostructures, there is plenty of room for researches to develop such micro/nano- structures, especially in the challenging biological field. The objectives of the research work described in this thesis are as follows: (1) to modify the surface of transparent materials or to fabricate two dimensional micro-structures on transparent materials to observe cell behaviors and to attempt to figure out the key factors that control cell behaviors, (2) to produce micro-scaled and even nano-scaled electrodes for the high spatial-temporal detection of chemical reactions and biological phenomena, (3) to synthesize nano-structured materials using chemical routes for surface enhanced Raman spectroscopy (SERS) detection, and (4) to prepare nanostructures using the template approach for large SERS substrates. The goal is integration of micro-devices for biological applications. This thesis is composed of five main parts. Firstly, fabrication of buried nano-scaled layers and micro-structures on transparent substrates for cell manipulation is described. The quartz is treated by plasma immersion ion implantation (PIII) to regulate the cell pattern and polydimethylsiloxane (PDMS) is modified by soft lithography to control cell behaviors. The results suggest that ions released from the buried layer can affect the attached neural cells and even control their behavior. The quartz modified by PIII exhibits stable performance that may be used in lab-on-a-chip devices. The versatility of modified PDMS also renders itself a promising candidate in integrated biological micro-devices. Secondly, a method to fabricate electrodes on the ultramicro- and nano- scales routinely is discussed. The as-prepared carbon fiber electordes are utilized to monitor the secreting behavior of neurons. The intrinsic properties of micro- and nano- electrodes make high spatial-temporal resolution detection a reality. The Kiss and Run (K&R) mechanism is shown to be the preferred mode of neural exocytosis. Thirdly, a wet chemical approach to prepare nanostructures on SERS substrate is described. The convenient self-selective electroless plating technique is demonstrated to yield silver dendritic nanostructures based on the diffusion-limited aggregation process. Such nano-scaled fractals have great potential as excellent SERS substrates for biological matters. Fourthly, two nanostructures fabricated by the anodic aluminum oxide (AAO) template are described. The silver nanorods are formed in the AAO holes by drying and decomposition of absorbed silver nitrate at high temperature. The silver nanorod arrays are used to detect fluorescent molecules at trace levels. The silver nanocaps on the hexagonal structures of the AAO are prepared by direct current magnetron sputtering. The nanocap arrays have large potential with regard to bio-molecule detection. The nano-structures produced by the template approach are normally clean and uniform and cover a large area, thereby making them high performance SERS substrates. Finally, possible future work based on this thesis is proposed. One direction is to integrate the modified substrates and as-prepared electrodes into a lab-on-a-chip system. This will facilitate researchers to probe cell behaviors and mechanisms. Another possibility is to develop optimized SERS substrates for quantitative analysis of biological molecules. The latter will broaden the applications of Raman spectroscopy.
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