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Title: Fabrication, characterization and application of metal tetraaminophthalocyanine polymer nanostructures
Authors: GU FENG
Keywords: polymer, nanostructures, sensor, nanotube, MTAPc, Field Emission
Issue Date: 15-Jun-2009
Citation: GU FENG (2009-06-15). Fabrication, characterization and application of metal tetraaminophthalocyanine polymer nanostructures. ScholarBank@NUS Repository.
Abstract: The objectives of this work were to develop versatile and non-destructive fabrication methods for organometallic polymer nanostructures and to explore their properties and potential applications. The system of focus was metal tetraaminophthalocyanine (MTAPc) polymeric nanostructures in the form of ordered nanowires, nanotubes and b nanoflowersb . Template-assisted electropolymerization was adopted as the major preparation protocol for these nanostructures.

In the first part of this thesis, organometallic polymer nanowires and nanotubes were fabricated through cyclic voltammetry (CV) electropolymerization on Pt-coated anodic aluminum oxide (AAO) templates. The spectral and elemental information, obtained from studies using UV-vis, Raman and energy dispersive x-ray (EDX) spectroscopies, confirmed the presence of the phthalocyanine frame with the amino substituted structure and the polymeric form. The field emission scanning electron microscopy (FE-SEM) and the transmission electron microscopy (TEM) studies showed that the morphology of these nanostructures could be controlled by electrochemical parameters, such as monomer concentration, scan rate and number of CV cycles. On the other hand, these results also verified the proposed mechanism of formation of these polymeric nanotubes in explaining the monomer concentration difference and the b tip effectb from tubular-shaped Pt electrodes. In studies on the electronic characteristics of these polymers, their interesting capacitor properties were observed and calculated from the cyclic voltammetry (CV) graph and the electrochemical impedance spectroscopy (EIS) by frequency response analysis.

In the second part of this thesis, the potential applications of poly-CuTAPc nanowires and nanotubes as field emitters and chemical sensor were investigated. Remarkable field emission properties of these nanostructures were obtained. A significant improvement of enhancement factor value (N2) was noticed for poly-CuTAPc nanotubes; their turn-on field and maximum current density are comparable to those of many other organic nanomaterials. In the latter part of the work, the detection of dopamine and nitric oxide (NO) were demonstrated using poly-MTAPc nanotube modified electrodes in aqueous solutions. High sensitivities were achieved in dopamine determination for both nickel and copper centered MTAPc polymer nanotube sensors in the B5M concentration range. For NO determination, detection limits as low as 10nM and ultra-high response currents in the B5A range were observed in common voltammetric analysis. High sensitivity and improved linear ranges were also obtained.

Finally, the chemical structure and surface morphology of drop-dried MTAPc materials were investigated and characterized as poly-MTAPc nanostructures formed through auto-oxidation using FE-SEM, UV-vis and EDX spectroscopies. The formation of MTAPc nanostructures was suggested to be a result of non-epitaxial growth and the versatile adhesion property of such structures towards various surfaces makes them possible templates for further electropolymerization of either the same or a different material.

The use of the electrochemical polymerization technique together with the size-confinement of AAO templates offers a versatile way for the fabrication of MTAPc polymer nanostructures. These polymer nanostructures may contribute to investigations on conductivity studies in nano-sized materials and their applications in microelectronics, chemical sensing, and field emission materials. The investigation of the polymerization mechanism will shed light on the understanding of the formation of a series of amino-substituted organic materials and their sensing abilities.
Appears in Collections:Ph.D Theses (Open)

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