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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

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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.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

The properties of superconducting YBa₂Cu₃O₇₋(δ) thin films have been studied. Films have been prepared by multilayer deposition followed by ex situ furnace annealing. Deposition consists of a combination of dc triode sputtering from metallic targets of Y and Cu and thermal evaporation from a BaF₂ source. Superconducting and structural properties of the films strongly depend on the annealing conditions. Several heat treatment cycles were investigated, as well as different compositions. Best results were obtained for films deposited on (100) SrTiO₃ substrates, exhibiting T(c)(onset) as high as 92 K and zero resistance by 85 K. The second part of this dissertation examines the properties of ceramic Nd₂₋ₓCeₓCuO₄₋(δ) and Nd₁ͺ₈₅Ce₀ͺ₁₅(Cu₁₋(y)Zn(y))O₄₋(δ) bulk samples. Superconducting properties are examined as a function of x and y. Accurate (± 0.001 Å) lattice parameter calculations are performed from experimental x-ray diffraction data. Comparisons with previous zinc-doping studies in the hole superconducting material La₁ͺ₈₅Sr₀ͺ₁₅CuO₄₋(δ) are made. Theoretical implications and the question of electron-hole symmetry in the copper oxide superconductors are also discussed.

Copper oxide supported on alumina (CuO/Al2O3), silica (CuO/SiO2) and chromia (CuO/Cr2O3) have been synthesized and characterized. These catalysts were characterized using XRD, SEM, TEM, ICP, BET surface area and pore volume, TPR, TPD, TGA-DSC and IR. The hydrogenation of octanal using these catalysts was investigated; however, the primary focus of the project was the influence of water on the reaction and the catalysts. The initial study using CuO/Al2O3 showed that the optimum operating conditions for subsequent catalytic testing was 160 °C and a hydrogen to aldehyde ratio of two. Under these conditions, a conversion of 99 % and selectivity to octanol of 97 % was achieved. Further catalytic testing, using CuO/Al2O3 and CuO/Cr2O3, was carried out by introducing water-spiked feed into the reaction system after steady state was reached using fresh feed. Based on literature, it was initially expected that the presence of water would cause catalyst poisoning and subsequently catalyst deactivation. However, contrary to the expectation, the presence of water did not influence the activity of these two catalysts. Furthermore, the selectivity to octanol increased to 98.5 % when CuO/Al2O3 was used for the reaction, whilst a minor change in the selectivity to octanol (0.5 %) was obtained when CuO/Cr2O3 was used. The interaction of the water with the surface hydroxyls on alumina is most likely the reason for the increase in the selectivity to octanol when using CuO/Al2O3. In contrast to the other two catalysts, the reaction over CuO/SiO2 showed a steady decrease in both the conversion of octanal and the selectivity to octanol with time-onstream when using fresh feed. After 55 hours on stream, the conversion reached 22 %, (from an initial 95 %) whilst the selectivity to octanol reached 89 % (from an initial 98 %). This decline in the conversion and selectivity to octanol was possibly due in part, to the low isoelectric point of silica, with mechanical failure being the major contributing factor to the catalyst’s deactivation. The decrease in the BET surface area and the presence of smaller particles in the SEM image, confirmed that mechanical failure occurred. Since steady state was not reached and deactivation occurred, the reaction over CuO/SiO2 was also carried out using water-spiked feed. The conversion of octanal was seen to gradually decrease to 73 % after 55 hours on stream, whilst the selectivity to octanol remained unchanged at 98 % for the duration of the reaction. This showed the beneficial effect of the presence of water by slowing down the decline in catalytic activity and maintaining the selectivity to octanol. The improved selectivity obtained in the presence of water was attributed to its interaction with the silica surface hydroxyls. Since octanal conversion continued to decrease, it indicated that mechanical failure was the primary cause in the loss of catalytic activity. The used catalysts were characterized using XRD, SEM, EDS composition scanning, TEM, BET surface area and pore volume, TGA-DSC and IR. The catalysts used for the reaction with the fresh feed and the water-spiked feed were characterized and compared. Except for the deactivation of CuO/SiO2, the characterization of these catalysts showed that the presence of water did not negatively impact the make-up of the catalyst. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.