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FABRICATION OF FUNCTIONAL NANOSTRUCTURES USING POLYELECTROLYTE NANOCOMPOSITES AND REDUCED GRAPHENE OXIDE ASSEMBLIES
Title
FABRICATION OF FUNCTIONAL NANOSTRUCTURES USING POLYELECTROLYTE NANOCOMPOSITES AND REDUCED GRAPHENE OXIDE ASSEMBLIES.
Creator
Chunder, Anindarupa, Zhai, Lei, University of Central Florida
Abstract / Description
A wide variety of nanomaterials ranging from polymer assemblies to organic and inorganic nanostructures (particles, wires, rods etc) have been actively pursued in recent years for various applications. The synthesis route of these nanomaterials had been driven through two fundamental approaches - ÂÂ'Top downÂÂ' and ÂÂ'Bottom upÂÂ'. The key aspect of their application remained in the ability to make the...
Show moreA wide variety of nanomaterials ranging from polymer assemblies to organic and inorganic nanostructures (particles, wires, rods etc) have been actively pursued in recent years for various applications. The synthesis route of these nanomaterials had been driven through two fundamental approaches - ÂÂ'Top downÂÂ' and ÂÂ'Bottom upÂÂ'. The key aspect of their application remained in the ability to make the nanomaterials suitable for targeted location by manipulating their structure and functionalizing with active target groups. Functional nanomaterials like polyelectrolyte based multilayered thin films, nanofibres and graphene based composite materials are highlighted in the current research. Multilayer thin films were fabricated by conventional dip coating and newly developed spray coating techniques. Spray coating technique has an advantage of being applied for large scale production as compared to the dip coating technique. Conformal hydrophobic/hydrophilic and superhydrophobic/hydrophilic thermal switchable surfaces were fabricated with multilayer films of poly(allylaminehydrochloride) (PAH) and silica nanoparticles by the dip coating technique, followed by the functionalization with thermosensitive polymer-poly(N-isopropylacrylamide)(PNIPAAM) and perfluorosilane. The thermally switchable superhydrophobic/ hydrophilic polymer patch was integrated in a microfluidic channel to act as a stop valve. At 70 degree centigrade, the valve was superhydrophobic and stopped the water flow (close status) while at room temperature, the patch became hydrophilic, and allowed the flow (open status). Spray-coated multilayered film of poly(allylaminehydrochloride) (PAH) and silica nanoparticles was fabricated on polycarbonate substrate as an anti-reflection (AR) coating. The adhesion between the substrate and the coating was enhanced by treating the polycarbonate surface with aminopropyltrimethoxylsilane (APTS) and sol-gel. The coating was finally made abrasion-resistant with a further sol-gel treatment on top of AR coating, which formed a hard thin scratch-resistant film on the coating. The resultant AR coating could reduce the reflection from 5 to 0.3% on plastic. Besides multilayered films, the fabrication of polyelectrolyte based electrospun nanofibers was also explored. Ultrathin nanofibers comprising 2-weak polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylaminehydrochloride) (PAH) were fabricated using the electrospinning technique and methylene blue (MB) was used as a model drug to evaluate the potential application of the fibers for drug delivery. The release of MB was controlled in a nonbuffered medium by changing the pH of the solution. Temperature controlled release of MB was obtained by depositing temperature sensitive PAA/poly(N-isopropylacrylamide) (PNIPAAM) multilayers onto the fiber surfaces. The sustained release of MB in a phosphate buffered saline (PBS) solution was achieved by constructing perfluorosilane networks on the fiber surfaces as capping layers. The fiber was also loaded with a real life anti-depressant drug (2,3-tertbutyl-4-methoxyphenol) and fiber surface was made superhydrophobic. The drug loaded superhydrophobic nanofiber mat was immersed under water, phosphate buffer saline and surfactant solutions in three separated experiments. The rate of release of durg was monitored from the fiber surface as a result of wetting with different solutions. Time dependent wetting of the superhydrophobic surface and consequently the release of drug was studied with different concentrations of surfactant solutions. The results provided important information about the underwater superhydrophobicity and retention time of drug in the nanofibers. The nanostructured polymers like nanowires, nanoribbons and nanorods had several other applications too, based on their structure. Different self-assembled structures of semiconducting polymers showed improved properties based on their architectures. Poly(3-hexylthiophene) (P3HT) supramolecular structures were fabricated on P3HT-dispersed reduced graphene oxide (RGO) nanosheets. P3HT was used to disperse RGO in hot anisole/N, N-dimethylformamide solvents, and the polymer formed nanowires on RGO surfaces through a RGO induced crystallization process. The Raman spectroscopy confirmed the interaction between P3HT and RGO, which allowed the manipulation of the composite's electrical properties. Such a bottom-up approach provided interesting information about graphene-based composites and inspired to study the interaction between RGO and the molecular semiconductor-tetrasulphonate salt of copper phthalocyanine (TSCuPc) for nanometer-scale electronics. The reduction of graphene oxide in presence of TSCuPc produced a highly stabilized aqueous composite ink with monodispersed graphene sheets. To demonstrate the potential application of the donor (TSCuPc)–acceptor (graphene) composite, the RGO/TSCuPc suspension was successfully incorporated in a thin film device and the optoelectronic property was measured. The conductivity (dark current) of the composite film decreased compared to that of pure graphene due to the donor molecule incorporation, but the photoconductivity and photoresponsivity increased to an appreciable extent. The property of the composite film overall improved with thermal annealing and optimum loading of TSCuPc molecules.
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Date Issued
2010
Identifier
CFE0003292, ucf:48509
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003292
Light Trapping in Thin Film Crystalline Silicon Solar Cells
Title
Light Trapping in Thin Film Crystalline Silicon Solar Cells.
Creator
Boroumand Azad, Javaneh, Chanda, Debashis, Peale, Robert, Del Barco, Enrique, Flitsiyan, Elena, Schoenfeld, Winston, University of Central Florida
Abstract / Description
This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband...
Show moreThis dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0(&)deg;-65(&)deg;. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains a scientific challenge, numerical optimization proves a viable alternative, paving the path towards practical implementation of the light trapping solar cells. A 3 (&)#181;m thick light trapping solar cell is modeled in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. It is shown that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. Further, 20 (&)#181;m and 100 (&)#181;m thick functional solar cells with the light trapping scheme are studied. The efficiency improvement is observed numerically and experimentally due to photon absorption enhancement in the light trapping cells with respect to a bare cell of same thickness.
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Date Issued
2017
Identifier
CFE0006936, ucf:51654
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006936