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Graduation date: 1998

Nanoparticles/nanocrystals have been recognized by their remarkable and technologically attractive properties which are different from those of bulk materials due to their ultra large surface area and extremely fine nanostructure. Highly sophisticated properties such as optical, magnetic, electronic, catalytic, mechanical, chemical and tribological properties can be obtained by advanced nanostructured coatings, making them desirable for industrial applications. This thesis encompasses the fabrication of nano/micro-structures of cuprous oxide (Cu2O) including nanocrystals, nanowires, nanocrystalline coatings and co-deposition of Cu2O/Cu by electrodeposition. The investigation in this thesis involved a systematic study by using a simple two-electrode system with copper sulphate as the electrolyte at pH 4.0 at room temperature and without the aids of any additive. The substrates under investigation included silicon wafer, stainless steel plate, highly oriented pyrolytic graphite (HOPG) and silver wire. By changing the kinds of the substrates, deposition modes, and deposition potentials, different types of nano/micro-structures of Cu2O were yielded. Nanometer-to-micron sized Cu2O single crystals were fabricated on an Au/Pd sputter-coated silicon wafer and stainless steel cathode. Different morphologies of the crystals were studied and their structural characterization was performed. The Cu2O crystals were generally of an octahedral shape. A growth mechanism was proposed to explain the morphologies of the observed nano/micro-structures. The effect of the electrodeposition parameters such as deposition voltage and deposition time, on the size of the crystals and their coverage on the substrates was examined. Highly aligned Cu2O nano/microwires were fabricated on the step edges of the HOPG substrate. With the same deposition potentials, longer deposition time would increase the diameter of the wires. Various crystal morphologies including flower-like and butterfly-like structures, and dendrites and truncated octahedra were observed on the working electrode of HOPG. Some of the morphologies were revealed for the first time by the one-step electrodeposition. To investigate the differences between yield by DC and pulsed electrodeposition respectively, the sizes and coverages of the deposited crystals on the substrate by DC and pulsed electrodeposition were compared. Two completely different forms of Cu2O, namely uniform nanocrystalline coatings and isolated single crystals, were fabricated on Ag microwires by pulsed and DC electrodeposition respectively. The results illustrated a very different effect on crystal nucleation between DC and pulsed electrodeposition, and suggested the possibility of using different voltage waveforms for electrodeposition in order to fabricate coatings with different nano/micro-structures on substrates. Gradual transition in the deposition products from pure Cu2O to pure Cu during electrodeposition with various DC potential was investigated. The percentage of Cu content was studied in depth for a full picture of the relationship between the depositing potentials and the compositions of the deposits. This thesis provides a method to fabricate nanocrystalline Cu2O, Cu and Cu/Cu2O on substrates in a single step without the use of additives. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

No description available.

Graduation date: 1996

Abstract Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool for the analysis of biomolecules such as peptides and proteins and soft ionization technique using the organic matrix. Because of the high concentration of the organic matrix produces high background signals in the low mass range, nanopatticles have been intensively applied in the surface-assisted Laser desorption/ionization-mass spectrometry (SALDI-MS) to reduce the background interferences in the MALDI.-MS. This thesis includes two projects. The first project applied the copper oxide nanorods, which absorbs 337 nm UV laser energy and has the large area, as the matrix for SALDI-TOF MS to detect four large antibiotics, peptides and proteins. The optimized conditions of the four antibiotic drugs were: 1000 £gM of copper oxide nanorods and incubation for 30 minutes to get the best signals. The LODs of the Lasalocid, Monensin, Salinomycin and Narasin are 200 nM, 25 nM, 50 nM and 50 nM, respectively. In addition, in this project, the CuO nanorods also can be mixed with glycerol to enhance the detection sensitivity for peptides and proteins. The second project presents the zinc selenium quantum dots (ZnSe QDs) modified with 3-mercaptopropionic acid (3-MPA) as the matrix and affinity probes in the SALDI-TOF MS. It strengthens the interaction between the gramicidin and zinc selenium quantum dots by electric interaction in the pH 6 phosphate buffer solution according to the pI value of the gramicidin and the pKa of. 3-mercaptopropionic acid. The best sensitivity of the gramicidin can be obtained under the optimized conditions: 50 £gM of zinc selenium quantum dots, 30 minutes incubation time and pH 6 of phosphate buffer solution. The LOD of the gramicidin is 0.08 £gM. This approach also can be successfully applied in the SALDI-TOF MS to enhance the sensitivity of peptides and proteins.

Copper oxide with various morphologies, such as nanocubes, nanorods, and nanoribbons was synthesized from the H2O/C2H5OH solution of Cu(OAc)2/NEt3 with or without tetraoctylammonium bromide (TOAB) under mild conditions. In the system of Cu(OAc)2/NEt3 (0.05 mmole : 7.9 mmole) with 0.75 mmole of TOAB in H2O/C2H5OH (10 mL : 40 mL) solution, We found that nanocubes of CuO spontaneously self-assembled into nanorods and then nanosheets with the increasing of reaction time. Structural characterization of the CuO nanorods shows that the rod grows primarily along the [010] direction. Nanorods of CuO were also characterized by TEM, HR-TEM, SAED, and XRD.

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Thesis (Ph. D.)--University of Chicago, Department of Physics. / "Private edition, distributed by The University pf Chicago Libraries, Chicago, Illinois." Includes bibliographical references. Also available on the Internet.