Nanostructured materials especially, one-dimensional (1D) nanostructures have unique physical, chemical, mechanical properties and are the building blocks for a range of nanoscale devices. The procedure employed for the synthesis of nanostructures involves the use of sophisticated instruments or rigorous chemical reactions. The motivation of our work is to develop a strategy that is simple, cost effective and applicable to a host of oxide materials. Nanostructures of various oxides have been grown from the metal as the source material. 1D ZnO nanostructures have been obtained by simply heating Zn metal in ambient air at temperatures below 600 °C. The nanostructures grow on the surface of the source material and the morphology is controlled by monitoring the curvature of the source material. This technique has an added advantage that neither any catalyst nor any gas flow is required. Tetrapods of ZnO are obtained when Zn is heated above 700 °C in ambient air. It has been shown that the morphology and the aspect ratio (length-to-diameter ratio) of the tetrapods depend on the temperature and the temperature gradient. Photoluminescence studies reveal good optical quality ZnO nanostructures. The technique employed to synthesize 1D ZnO nanostructures has been checked for other oxides. The temperature required for the synthesis of Ga2O3 nanostructures is 1200 °C. Many researchers have shown that Ga2O3 emits in the blue-green region. A red emission is required to get the impression of white light which has been seen for nitrogen doped Ga2O3. As the temperature is very high and Ga is heated in ambient air, unintentional nitrogen doping of 1D Ga2O3 nanostructures is obtained which is the reason for white light emission. The morphology of Ga2O3 nanostructures has been controlled by monitoring the curvature of the starting material as is the case of ZnO. Similar technique has also been employed for the synthesis of CuO nanostructures. The morphology is temperature dependent and 1D CuO nanostructures are obtained when the synthesis temperature is between 400 and 600 C. Possible growth mechanisms have been proposed for all these oxide materials. The entire thesis is based on the results discussed above. It has been organized as follows: Chapter 1 deals with the introduction to nanostructures, importance of 1D nanostructures, the specific applications of different morphologies, materials that are widely explored in the synthesis of nanostructures and different approaches to the synthesis of nanostructures. Growth mechanisms like VLS, VS and SLS are briefly discussed. A brief review on the basic physical properties, applications and different morphologies of ZnO, Ga2O3 and CuO is outlined with emphasis to the various synthesis techniques. Finally the aim and scope of the present work is discussed. Chapter 2 describes the experimental setup used for the synthesis and the basic principles of characterization techniques like x-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectrum (EDS), electron energy loss spectroscopy (EELS), photoluminescence (PL), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), UV-Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). Chapter 3 deals with the synthesis of 1D ZnO nanostructures with different morphologies such as nanoneedles, nanorods, nanobelts from Zn powder/granule. The growth process is found to be different from the conventional VS mechanism. The advantage and the versatility of the method is emphasized. In this method, neither a catalyst nor any gas flow is required for the synthesis of oxide nanostructures. Depending upon the Zn powder or Zn granules as the starting material different nanostructures of ZnO have been synthesized. The as-synthesized materials are characterized by XRD, SEM, HRTEM, EDS, TGA and Raman spectroscopy and the results are discussed. Chapter 4 describes the controlled growth of ZnO tetrapods and the influence of temperature and temperature gradient on the growth process. Though there are several methods to synthesize ZnO tetrapods and it has been established that ZnO tetrapods can be synthesized by heating Zn in air, it is advantageous to grow tetrapods of different morphologies with different lengths. The large scale synthesis of ZnO tetrapods by heating Zn in air ambient is discussed in this chapter. The key parameters that control the diameter, length, and morphology of tetrapods are identified. It is shown that the morphology and dimensions of the tetrapods depend not only on the vaporization temperature but also on the temperature gradient of the furnace. The influence of vaporization temperature and growth temperature on the morphology of the tetrapods is discussed elaborately. Chapter 5 explains the one-step synthesis of nitrogen doped Ga2O3 nanostructures of different morphologies and the different growth mechanisms. The experimental method employed for the synthesis of nanostructures is simple and is different from the other reported methods. Neither any catalyst/substrate preparation nor any gas flow is required for the synthesis of Ga2O3 nanostructures. The synthesis involves the heating of molten Ga at high temperatures. Single crystalline monoclinic phase of nitrogen-doped Ga2O3 nanorods, nanobelts and nanoneedles are obtained by this method. The morphology is controlled by monitoring the curvature of the Ga droplet which is achieved by using different substrates. Possible growth processes of different morphology have been proposed. Chapter 6 includes some surprising results on the white light emission of Ga2O3 nanorods. High synthesis temperature generates a high vapor pressure suitable for the growth of Ga2O3 nanorods, creates oxygen vacancy and incorporates nitrogen from the ambient. The oxygen vacancy is responsible for the bluish-green emission, while nitrogen is responsible for the red emission. As a consequence, white light emission is observed from Ga2O3 nanorods when irradiated with UV light. The interesting point is that neither post-treatment of the nanorods nor size control is required for white light emission. Chapter 7 describes the synthesis of CuO nanostructures by heating Cu foil in air ambient. This is an attempt to check whether the synthesis technique employed for ZnO and Ga2O3 is applicable to other oxides. The as-synthesized CuO nanostructures are characterized by XRD, SEM, HRTEM, EDS, TGA, UV-visible, FTIR and the results are discussed. Chapter 8 gives the conclusions and the overall summary of the thesis.

<p>This licentiate study was initiated by copper, zinc and galvanized steel producers in Europe, who felt a need to assess runoff rates of copper and zinc from the pure metals and commercial products at marine exposure conditions. Their motive was the increasing concern in various European countries and the on-going risk assessments of copper and zinc within the European commission. Also the circumstance that available runoff rates so far, had been reported for mainly urban exposure conditions, rather than marine. A collaboration was therefore established with the French Corrosion Institute, which runs a marine test site in Brest, and a set of vital questions were formulated. Their answers are the essence of this licentiate study.</p><p>Based on the ISO corrosivity classification and one-year exposures, the marine atmosphere of Brest is fairly corrosive for zinc (class C3) and highly corrosive for copper (C4). Despite higher corrosivity classifications for both metals in Brest compared to the urban site of Stockholm, used as a reference site, nearly all runoff rates assessed for copper, zinc and their commercial products were lower in Brest compared to Stockholm. This was attributed to a higher surface wetting in Brest and concomitant higher removal rate of deposited chloride and sulphate species from the marine-exposed surfaces. The comparison shows that measured corrosion rates cannot be used to predict runoff rates, since different physicochemical processes govern corrosion and runoff respectively.</p><p>For copper, the runoff rate in Brest was approximately 1.1 g m^-2 yr^-1 with cuprite (Cu2O) as main patina constituent. During periods of very high chloride and sulphate deposition, paratacamite (Cu₂Cl(OH)₃) formed which increased the runoff rate to 1.5 g m^-2 yr^-1. For zinc, with hydrozincite (Zn₅(CO₃)2(OH)₆) as the main patina constituent, the runoff rate was relatively stable at 2.6 g m^-2 yr^-1 throughout the year, despite episodes of heavy chloride and sulphate deposition.</p><p>The application of organic coatings of varying thickness on artificially patinated copper or on different zinc-based products resulted in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. The thickest organic coating (150 µm thick), applied on hot dipped galvanized steel, reduced the runoff rate by a factor of 100. No deterioration of organic coatings was observed during the one-year exposures. Alloying zinc-based products with aluminium resulted in surface areas enriched in aluminium and concomitant reduced zinc runoff rates.</p><p>The release rate and bioavailability of copper from different anti-fouling paints into artificial seawater was also investigated. It turned out that the release rate not only depends on the copper concentration in the paint, but also on paint matrix properties and other released metal constituents detected. Far from all copper was bioavailabe at the immediate release situation. In all, the results suggest the importance of assessing the ecotoxic response of anti-fouling paints not only by regarding the copper release, but rather through an integrated effect of all matrix constituents.</p>

Presented diploma thesis focuses on the study of diffusion of cupric ions in humic acid hydrogels. A total of eight different hydrogels were prepared by dissolving the humic acids with sodium hydroxide and sodium triphosphate. For the purpose of precipitation and cross linking, hydrochloric acid and chlorides of magnesium, calcium and iron were used during a modified preparation of gels. Different gel-forming interactions were achieved by modifying the preparation of hydrogel systems. The aim of the thesis was to assess the effect of gel preparation procedure on the transport properties of the gels. Therefore, diffusion coeficients were determined for all samples. Two different methods - constant-source diffusion and instantaneous planar source diffusion - were used to assign the diffusion coefficients. Methods differ in source concentrations of cupric ions and are suitable for assessing the impact of the concentration on the diffusion coefficient. Both these methods were based on monitoring temporal evolution of diffusion profiles of cupric ions and on assigning the overall diffusion flow. Copper ions were elected as diffusing medium because of their high affinity and strong binding to humic acids. Measurements show that gels prepared using polyphosphate allow slightly faster diffusion of cupric ions and that the constant-source method provides higher diffusion coefficients in comparison to instantaneous planar source method.

Presented diploma thesis focuses on the study of diffusion of cupric ions in humic acid gels. A total of fifth different standards of humic acids and one sample humic acid prepared from same source as in bachelor's thesis, on which this thesis continues, were used for preparation solutions of humic acids. Thereafter, these solutions were used for preparation of agarose hydrogels, which were necessary in following diffusion experiments. The objective of the work was to compare transport properties of humic standards between themselves and then compare standards with humic acid prepared from same source as in bachelor's thesis. Measure, which was used to determine the transport properties, was comparison of effective diffusion coefficients. Method of instantaneous planar source diffusion was used to compare them. This method was based monitoring temporal evolution of diffusion profiles of cupric ions in humic hydrogels. Copper ions were selected as diffusing medium because of their high affinity and strong bonds to humic acids.

In this work the structure of the electrochemical metal-liquid interface is determined through use of quantum mechanics, molecular simulation, and experiment. Herein are profiled the molecular dynamics details and results of solid-liquid interfaces at flat non-specific solid surfaces and copper metal electrodes. Ab initio quantum-mechanical calculations are reported and define the interatomic potentials in the simulations. Some of the quantum-mechanical calculations involve small copper clusters interacting with 3-mercaptopropanesulfonic acid (MPSA), sodium, chloride, bisulfate and cuprous ions. In connection with these I develop the electrode charge dynamics (ECD) routine to treat the charge mobility in a metal. ECD bridges the gap between small-scale metal-cluster ab initio calculations and large-scale simulations of metal surfaces of arbitrary geometry. As water is the most abundant surface species in aqueous systems, water determines much of the interfacial dynamics. In contrast to prior simulation work, simulations in this work show the presence of a dense 2D ice-like rhombus structure of water on the surface that is relatively impervious to perturbation by typical electrode charges. I also find that chloride ions are adsorbed at both positive and negative electrode potentials, in agreement with experimental findings. Including internal modes of vibration in the water model enhances the ion contact adsorption at the solid surface. In superconformal filling of copper chip interconnects, organic additives are used to bottom-up fill high-aspect ratio trenches or vias. I use molecular dynamics and rotating-disk-electrode experiments to provide insight into the function of MPSA, one such additive. It is concluded that the thiol head group of MPSA inhibits copper deposition by preferentially occupying the active surface sites. The sulfonate head group participates in binding the copper ions and facilitating their transfer to the surface. Chloride ions reduce the work function of the copper electrode, reduce the binding energy of MPSA to the copper surface, and attenuate the binding of copper ions to the sulfonate head group of MPSA.

This licentiate study was initiated by copper, zinc and galvanized steel producers in Europe, who felt a need to assess runoff rates of copper and zinc from the pure metals and commercial products at marine exposure conditions. Their motive was the increasing concern in various European countries and the on-going risk assessments of copper and zinc within the European commission. Also the circumstance that available runoff rates so far, had been reported for mainly urban exposure conditions, rather than marine. A collaboration was therefore established with the French Corrosion Institute, which runs a marine test site in Brest, and a set of vital questions were formulated. Their answers are the essence of this licentiate study. Based on the ISO corrosivity classification and one-year exposures, the marine atmosphere of Brest is fairly corrosive for zinc (class C3) and highly corrosive for copper (C4). Despite higher corrosivity classifications for both metals in Brest compared to the urban site of Stockholm, used as a reference site, nearly all runoff rates assessed for copper, zinc and their commercial products were lower in Brest compared to Stockholm. This was attributed to a higher surface wetting in Brest and concomitant higher removal rate of deposited chloride and sulphate species from the marine-exposed surfaces. The comparison shows that measured corrosion rates cannot be used to predict runoff rates, since different physicochemical processes govern corrosion and runoff respectively. For copper, the runoff rate in Brest was approximately 1.1 g m-2 yr-1 with cuprite (Cu2O) as main patina constituent. During periods of very high chloride and sulphate deposition, paratacamite (Cu2Cl(OH)3) formed which increased the runoff rate to 1.5 g m-2 yr-1. For zinc, with hydrozincite (Zn5(CO3)2(OH)6) as the main patina constituent, the runoff rate was relatively stable at 2.6 g m-2 yr-1 throughout the year, despite episodes of heavy chloride and sulphate deposition. The application of organic coatings of varying thickness on artificially patinated copper or on different zinc-based products resulted in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. The thickest organic coating (150 µm thick), applied on hot dipped galvanized steel, reduced the runoff rate by a factor of 100. No deterioration of organic coatings was observed during the one-year exposures. Alloying zinc-based products with aluminium resulted in surface areas enriched in aluminium and concomitant reduced zinc runoff rates. The release rate and bioavailability of copper from different anti-fouling paints into artificial seawater was also investigated. It turned out that the release rate not only depends on the copper concentration in the paint, but also on paint matrix properties and other released metal constituents detected. Far from all copper was bioavailabe at the immediate release situation. In all, the results suggest the importance of assessing the ecotoxic response of anti-fouling paints not only by regarding the copper release, but rather through an integrated effect of all matrix constituents. / QC 20101126

No description available.

In this work, experimental and theoretical approaches are applied to the study of chemical reaction dynamics. In Chapter 2, two applications of transition state theory are presented: (1) Application of microcanonical transition state theory to determine the rate constant of dissociation of C2F3I after π∗ ← π excitation. It was found that this reaction has a very fast rate constant and thus is a promising system for testing the statistical assumption of molecular reaction dynamics. (2) A general rate constant expression for the reaction of atoms and molecules at surfaces was derived within the statistical framework of flexible transition state theory. In Chapter 4, a computationally efficient TDDFT approach was found to produce useful potential energy surface landscapes for application to non-adiabatic predissociative dynamics of the molecule CS2 after excitation from the ground state to the singlet C-state. In Chapter 5, ultrafast experimental results of excitation of CS2 to the predissociative neutral singlet C-state is presented. The bandwidth of the excitation laser was carefully tuned to span a two-component scattering resonance with each component differently evolving electronically with respect to excited state character during the quasi-bound oscillation. Scalar time-resolved photoelectron spectra (TRPES) and vector time-resolved photoelectron angular distribution (TRPAD) observables were recorded during the predissociation. The TRPES yield of photoelectrons was found to oscillate with a quantum beat pattern for the photoelectrons corresponding to ionization to the vibrationless cation ground state; this beat pattern was obscured for photoelectron energies corresponding to ionization from the vibrationally excited CS2 cation. The TRPAD data was recorded for two general molecular ensemble cases: with and without a pre-excitation alignment laser pulse. It was found that in the case of ensemble alignment (Chapter 6), the “molecular frame” TRPAD (i.e. TRMFPAD) was able to image the purely valence electronic dynamics of the evolving CS2 C-state. The unaligned ensemble TRPAD observable suffers from excessive orientational averaging and was unable to observe the quantum beat. Engineering efforts were also undertaken to eliminate scattered light background signal (Chapter 7, Appendix A) and improve laser stability as a function of ambient pressure (Appendix B) for TRMFPAD experiments. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-09-11 22:18:20.89