Volcanogenic massive sulphide deposits are important sources of base metals throughout the world. The Canadian Cu-Zn-(Au, Ag) deposits of Archaean age occur in greenstone terrains within the Canadian Shield. These deposits are closely associated with volcanic vents developed along zones of rifting within mobile belts. The vents are manifested by coarse felsic pyroclastics and/or rhyolitic domes. The Japanese Pb-Zn-Cu-Ba(Ag) deposits, generally known as Kuroko deposits, are of Miocene age, and although also associated with volcanic vents, are developed above zones of subduction. Mineralization in volcanogenic deposits is a result of submarine exhalation of metalliferous hydrothermal solutions derived from fractionation of predominantly calc-alkaline magmas. The deposits are characterized by certain geological features that result from the interaction of specific physical and chemical conditions during deposition. Primary features include massive and stringer sulphide bodies, alteration zones, mineralogical and metal zoning, and certain depositional textures and structures. These features are commonly modified by subsequent metamorphism and deformation which impart secondary ore textures and affect metal distribution and shape. The disparity in age between Canadian and Japanese deposits allows the entire spectrum of geological features to be studied; from the completely unaltered to the high deformed and recrystallized. The characteristic geological features are the prime factors which control the metal distribution and concentration, and the size and shape of the deposits, thereby influencing the viability of the respective ore bodies. A knowledge of these factors and the physico-chemical parameters which control them are thus fundamental in the "understanding" of these deposits. They ultimately control the geological interpretations and predictions made during ore body delineation, ore reserve estimation, mining and ore beneficiation.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1981 / Includes bibliographical references. / by Ze'ev Shaked. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemistry

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本論文示範了兩款過渡金屬硫化物量子點 (二硫化銀銦量子點與硫化錳量子點) 在量子點敏化太陽能電池上作為光敏化劑的應用，這也是它們在量子點敏化太陽能電池上的初次應用。 / 二硫化銀銦量子點的合成採用了一鍋合成法，合成的量子點隨後透過3-巰基丙酸連接到二氧化鈦的表面。研究發現，當量子點溶液的濃度處於較低水平的時候，量子點在二氧化鈦的吸附量會較高。另外，從不同研究小組在量子點吸附行為的報告中，觀察到量子點的吸附行為決定於實驗條件，如量子點的大小和表面活劑，納米二氧化鈦多孔膜的孔隙度和量子點的溶劑。實驗中，最高性能的二硫化銀銦量子點敏化太陽能電池的短路電流為0.49 mA/cm²，開路電壓為0.245 V，填充因子為38.26 %，光電轉換效率為0.046 %。 / 透過連續離子層沉積反應法，硫化錳量子點生長並組裝到二氧化鈦的表面上。能譜測量顯示，錳跟硫的比率在不是1:1。這現象懷疑是源於錳(2+)的小離子半徑，對錳(2+)和硫(2-)之間的化學反應產生了不良的影響，導致吸附了的錳(2+)沒有反應過來。通過優化連續離子層沉積反應法週期的數量，最高性能的硫化錳量子點敏化太陽能電池的短路電流為0.65 mA/cm²，開路電壓為0.30 V，填充因子為48.21 %，光電轉換效率為0.095 %。 / QD-SSCs sensitized with novel transition metal sulfides have been demonstrated. Both AgInS₂ QD-SSC and MnS QD-SSC presented in this thesis are new and are the first demonstrated works in the research field. / AgInS₂ QDs was synthesized by one-pot hot colloidal synthesis approach. The as-synthesized QDs were attached to the TiO₂ surface through 3-mercaptopropionic acid. Optimization process on QDs adsorption was done, and it has been observed that the amount of QDs adsorbed is higher when the concentration of the QDs solution is at low level. The variations in the behaviors in QDs adsorption between works from different research groups are considered to originate from experimental conditions such as the sizes and surfactants of QDs, porosities in the TiO₂ matrix, and the solvent for QDs dispersion. The optimized AgInS₂ QD-SSC attained a short-circuit current of 0.49 mA/cm², an open-circuit voltage of 0.245 V, a fill factor of 38.26 % and a power conversion efficiency of 0.046 %. IPCE measurements confirm the successful sensitization from AgInS₂ QDs, indicating the energetically favourable electron injection from AgInS₂ QDs to TiO₂. / By adopting the SILAR technique, MnS QDs was in-situ grown and deposited on the TiO₂ surface. EDX measurements indicated that the Mn/S ratio in the TiO₂/MnS film is not 1:1. The reason is suspected to originate from the small ionic radius of Mn²⁺ that promoted an adverse effect on the reaction between Mn²⁺ and S²₋. It is proposed that a portion of the adsorbed Mn²⁺ did not react with the S²₋., resulting an excess concentration of Mn²⁺ in the film. By optimizing the number of SILAR cycles, MnS QD-SSC was optimized to exhibit a short-circuit current of 0.65 mA/cm², an open-circuit volatge of 0.30 V, a fill factor of 48.21 % and a power conversion efficiency of 0.095 %. IPCE measurements confirm the sensitization is originated from MnS QDs, which consequently reveal an energetically favourable electron injection from the MnS QDs to TiO₂. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Cheng, Kai Chun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Solar cells --- p.2 / Chapter 1.2.1 --- Developments --- p.2 / Chapter 1.2.2 --- Nanostructured solar cells --- p.4 / Chapter 1.2.2.1 --- Bilayer organic solar cells --- p.4 / Chapter 1.2.2.2 --- Bulk heterojunction organic solar cells --- p.5 / Chapter 1.2.2.3 --- Organic-inorganic hybrid solar cells --- p.7 / Chapter 1.2.2.4 --- Dye-sensitized solar cells --- p.8 / Chapter 1.2.2.5 --- Quantum dot-sensitized solar cells --- p.11 / Chapter 1.2.3 --- Characterization of solar cells --- p.11 / References --- p.14 / Chapter Chapter 2 --- Quantum dot-sensitized solar cells --- p.18 / Chapter 2.1 --- Quantum dots --- p.18 / Chapter 2.1.1 --- Quantum confinement --- p.18 / Chapter 2.1.2 --- Multiple exciton generation --- p.20 / Chapter 2.2 --- Quantum dot-sensitized solar cell --- p.22 / Chapter 2.2.1 --- Principles --- p.22 / Chapter 2.2.2 --- Assembly of oxide/quantum dot film --- p.25 / Chapter 2.2.3 --- Light harvesting and electron injection --- p.29 / Chapter 2.2.4 --- Titanium dioxide as electron acceptor --- p.33 / Chapter 2.2.5 --- Redox process of electrolyte --- p.37 / Chapter 2.2.6 --- Counter electrode materials --- p.39 / References --- p.41 / Chapter Chapter 3 --- Experimental Details --- p.45 / Chapter 3.1 --- Materials --- p.45 / Chapter 3.2 --- Preparation of the TiO₂ mesoporous film --- p.46 / Chapter 3.3 --- Synthesis of AgInS₂ quantum dots --- p.47 / Chapter 3.4 --- Preparation of the TiO₂/QDs film --- p.47 / Chapter 3.5 --- Configuration of the QD-sensitized solar cell --- p.49 / Chapter 3.6 --- Characterization and Photoelectrochemical Measurements --- p.51 / References --- p.52 / Chapter Chapter 4 --- Experimental Results --- p.53 / Chapter 4.1 --- AgInS₂ QD-sensitized solar cell --- p.54 / Chapter 4.1.1 --- Characterization of AgInS₂ QDs --- p.54 / Chapter 4.1.2 --- Adsorption of AgInS₂ QDs on the TiO₂ surface --- p.56 / Chapter 4.1.3 --- Photoelectrochemical measurements of the AgInS₂ QD-SSC --- p.60 / Chapter 4.2 --- MnS QD-sensitized solar cell --- p.64 / Chapter 4.2.1 --- Characterization of MnS QDs --- p.64 / Chapter 4.2.2 --- Photoelectrochemical measurements of the MnS QD-SSC --- p.69 / References --- p.74 / Chapter Chapter 5 --- Discussions and Conclusions --- p.75 / Chapter 5.1 --- Discussions --- p.76 / Chapter 5.1.1 --- AgInS₂ QD-SSC --- p.76 / Chapter 5.1.1.1 --- Adsorption of AgInS₂ QDs on the TiO₂ surface --- p.76 / Chapter 5.1.1.2 --- Electron injection --- p.80 / Chapter 5.1.1.3 --- Problems encountered and future directions --- p.83 / Chapter 5.1.2 --- MnS QD-SSC --- p.84 / Chapter 5.1.2.1 --- Growth of MnS QDs on the TiO₂ surface --- p.85 / Chapter 5.1.2.2 --- Effects of SILAR cycles on MnS QD-SSC --- p.86 / Chapter 5.1.2.3 --- Problems encountered and future directions --- p.88 / Chapter 5.1.3 --- AgInS₂ QD-SSC versus MnS QD-SSC --- p.89 / Chapter 5.2 --- Conclusions --- p.91 / References --- p.94

Wastewater treatment plants (WwTP) act as the principle buffer between anthropogenic sources of Silver Nanoparticles (AgNPs) and environmental targets. AgNPs, given their effective anti-microbial properties, have the potential to negatively impact WwTP processes and organisms within the natural environment. A clear understanding of the fate and transport of AgNPs as they pass through WwTPs is crucial in evaluating AgNPs impacts for WwTP process, the natural environment and in the development of a comprehensive environmental risk assessment for AgNPs. The main aim of this thesis was to carry out an analysis on the fate, transport and transformation of AgNPs through WwTP relevant filtration medias in order to understand more about the toxicological implications for both WwTP processes and receiving environments. AgNPs were synthesised in-house, via an in-situ reduction method, which produced a homogeneous dispersion of nanoparticles of average particle diameter 9.98nm, with a standard deviation of 3.11nm. Column studies and adsorption isotherm experiments were conducted to investigate the fate and transport of silver nitrate, AgNPs and bulk silver across media beds of quartz sand and granulated activated carbon (GAC), both chosen for their relevance in wastewater treatment protocols. TEM imaging and EDS analysis was employed to characterise the AgNPs physically and elementally within the column influents and effluents. An original contribution made to the existing knowledge on AgNPs is that in contrast to bulk silver and silver nitrate, uncoated AgNPs were observed to be highly mobile through the quartz sand media. This high mobility was in contrast with the prior expectation that van der Waals forces of attraction between the positively charged AgNPs and the negative charge of the silica surfaces within the sand bed would lead to some measure of retention within the column matrix. The resulting high mobility of the AgNPs was attributed to particle surface contamination of boride ions originating from the reduction agent used during the synthesis process. This highlights (and reinforces) the importance of better understanding on the implications of the various methods of synthesis and use of capping agents for AgNPs characteristics and the impact this has on fate and transport. AgNPs were also noted to have been significantly altered after their passage through the quartz sand media, with up to 83% of the sample increasing in size, from 9.98nm to an average of 18.26nm and a maximum of 144nm. Particle size measurements were made using the measuring tool available in the GNU Image Manipulation Program (GIMP). This size increase was attributed to the formation of nano-alloy clusters with residual gold and iron compounds, naturally present within the sand bed. In the case of silver-gold alloy clusters, this is expected to exhibit positive implications for future environmental fates of the resulting AgNPs, where the presence of gold in alloy clusters has been observed to significantly deactivate AgNPs silver ion release. In contrast to the sand, it was observed that the GAC was an effective absorber of AgNPs. However, this was observed to be a size dependant relationship, where the GAC was not observed to be effective for adsorption of bulk silver at particle sizes of 300 – 800nm. In this thesis, in addition to the experimental work, a novel, low complexity technique was developed for the detection and quantification of AgNPs in laboratory aqueous solutions. This protocol utilises a laboratory bench top photometer and gave AgNPs concentration results that reliably and accurately reflected that of ICP-MS and ICP-OES results within a detection range of 0.01 and 20mg/L; where the correlation coefficient between the instrument absorbance response and ICP-MS/OES concentration (at 450nm) was R2 0.994.

The effect of stoichiometry on the pyrolytic decomposition, oxidation and ignition behaviour of synthetic violarite and pentlandite has been established. These minerals, of general formula (Fe,Ni)(subscript)3S(subscript)4 and (Fe,Ni)(subscript)9S(subscript)8 respectively, may vary considerably in Fe:Ni ratio. Pentlandite can also show some variation in metal:sulfur ratio. A series of samples, ranging in stoichiometry from Fe(subscript)0.96Ni(subscript)1.97S(subscript)4 to Fe(subscript)0.20Ni(subscript)2.72S(subscript)4 and Fe(subscript)5.80Ni(subscript)3.15S(subscript)8 to Fe(subscript)3.40Ni(subscript)5.55S(subscript)8, were synthesised and characterised using wet chemical analysis, electron probe micro-analysis (EPMA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer, Emmett and Teller (BET) surface area analysis.The thermal behaviour of these sulfides was examined using simultaneous Thermogravimetry-Differential Thermal Analysis (TG-DTA) at different heating rates and in different atmospheres. Partially reacted samples were collected at various temperatures and analysed using XRD, EPMA, SEM, optical microscopy (OM), and Fourier transform infrared (FTIR) spectroscopy. The endmembers of the violarite and pentlandite series were examined in detail to determine the effect of stoichiometry on the reaction mechanism. In this study the reaction mechanism refers to the sequence of reactions occurring during pyrolytic decomposition or oxidation of the sulfide minerals. Samples were sieved into four particle size fractions, 125-90, 90-63, 63-45 and 45-20 gm, to determine the effect of particle size on the reaction mechanism.When violarite was heated in an inert atmosphere at 10 degrees celsius min(subscript)-1, it initially decomposed to a monosulfide solid solution (mss), (Fe,Ni)(subscript)1-xS, and vaesite, (Ni,Fe)S(subscript)2, indicated by a ++ / sharp endothermic peak in the DTA trace. The decomposition temperature was found to be linearly dependent on the iron:nickel ratio, decreasing from 495 degrees celsius to 450 degrees celsius as the iron:nickel ratio decreased from 0.49 to 0.07. This was followed by a broader endothermic peak coinciding with a rapid mass loss, which was associated with the decomposition of vaesite to mss with the loss of sulfur. Between 615-805 degrees celsius the mss was converted to a high temperature form of heazlewoodite, (Fe,Ni)(subscript)3+/-S(subscript)2 melted incongruently at 835 degrees celsius and 805 degrees celsius for Fe(subscript)0.96Ni(subscript)1.97S(subscript)4 and Fe(subscript)0.20Ni(subscript)2.72S(subscript)4 respectively, with further loss of sulfur vapour forming a central sulfide liquid of general formula (Fe,Ni)(subscript)1+xS.Under similar experimental conditions, pentlandite pyrolytically decomposed forming mss and heazlewoodite with no associated loss of sulfur. The decomposition temperature decreased as the iron:nickel ratio deviated from the ideal value of 1:1. A maximum decomposition temperature of 610 degrees celsius was found at an iron:nickel ratio of 1.00, decreasing to 580 degrees celsius at a ratio of 1.84 and 0.61. Sulfur was evolved slowly at temperatures in excess of 760 degrees celsius as mss was converted to heazlewoodite, indicated by a gradual mass loss. The heazlewoodite then melted incongruently in excess of 840 degrees celsius indicated by a sharp endothermic peak, resulting in a further loss of sulfur.The oxidation of violarite and pentlandite was investigated at a heating rate of 10 degrees celsius min(subscript)-1 in an air atmosphere. The oxidation of violarite was initiated by decomposition to mss resulting in a rapid mass loss associated with the evolution of sulfur vapour, and an exothermic peak due to the gas phase oxidation of ++ / the sulfur. The iron sulfide component of the mss was then preferentially oxidised to iron(II) sulfate between 485-575 degrees celsius, upon which the sulfate decomposed and the remaining iron sulfide was preferentially oxidised to hematite. The mss core was then converted to (Fe,Ni)(subscript)3+/-xS(subscript)2 between 635-715 degrees celsius, resulting in the loss of further sulfur which was oxidised. The sulfide core, which consisted of predominantly Ni(subscript)3+/-xS(subscript)2 with a minor amount of iron still remaining in solid solution, incongruently melted at a constant temperature of 795 degrees celsius regardless of the initial stoichiometry of the violarite sample. This was followed by the rapid oxidation of the liquid sulfide resulting in a sharp exothermic peak in the DTA trace.For pentlandite, the TG-DTA curve exhibited an initial mass gain commencing at approximately 400 degrees celsius, which was attributed to the preferential oxidation of iron. Evidence from SEM indicated that iron migrated towards the oxygen interface, where it was oxidised to hematite. During this process the metal: sulfur ratio decreased and pentlandite was converted to mss. The iron sulfide component of the mss phase was then preferentially oxidised to hematite as indicated by a major exotherm, which occurred in the temperature range 575-665 degrees celsius, forming an oxide product layer around a nickel sulfide core. The oxidation of the remaining nickel sulfide followed the same reaction sequence to that of violarite.By increasing the heating rate to 40 degrees celsius min(subscript)-1, and carrying out the oxidation in pure oxygen, the tendency of the sulfides to ignite was established. Ignition was characterised by a highly exothermic reaction which coincided with a rapid mass loss over a short time period. Overheating of the samples above the programmed furnace ++ / temperature was also observed. Violarite exhibited ignition behaviour while pentlandite did not.Both sulfides were subjected to shock heating conditions (heating rate = 1500 - 5000 degrees celsius min(subscript)-1, oxygen atmosphere) using isothermal thermogravimetry (TG). This method produces heating rates analogous to those which are experienced in the reaction shaft of an industrial flash smelter. The effect of stoichiometry on ignition temperature and extent of oxidation for the entire series of synthetic violarites and pentlandites was determined. Partially ignited and ignited products were collected from isothermal TG experiments and were examined by OM, SEM and EPMA to establish the ignition mechanism.Both violarite and pentlandite ignited using the isothermal TG technique. A clear relationship was found between the stoichiometry of violarite and pentlandite and the ignition temperature, with an increase in the iron:nickel ratio causing a decrease in the ignition temperature. The ignition temperature also decreased as the size of the particles decreased.The extent of oxidation increased as the iron:nickel ratio increased, and also increased as the particle size decreased.

An investigation has been made of the role of the four disulfide bonds of bovine pancreatic ribonuclease in maintaining the protein in a biologically active form. Studies were carried out to determine the effect of reductive cleavage of these bonds on the ability of the enzyme to catalyze the hydrolysis of ribonucleic acid. The appearance of sulfhydryl groups was taken as evidence that reduction of the protein had occurred. <P> No significant reduction or loss of enzymic activity of ribonuclease could be demonstrated when the protein was treated with the reducing agents sodium or potassium borohydride in aqueous solution at room temperature,pH 8. <P> Thioglycolic acid was found to be an effective agent for reducing ribonuclease disulfide bonds. At room temperature, in an aqueous solution containing a Large excess of thioglycolate over protein, reduction proceeded slowly at pH 8. At the end of five hours, approximately one disulfide bond was broken, with the loss of 20 per cent of the original enzyme activity. The addition of urea greatly facilitated reduction. The rate of reduction was especially rapid in solutions of urea concentration greater than 4 molar. In 8 M urea at pH 8, treatment of ribonuclease with thioglycolate resulted in the complete loss of enzymic activity in one half hour, with the simultaneous rupture of two or three disulfide bonds. Under these conditions, maximum reduction was achieved in approximately two hours, with cleavage of between three and four disulfide bonds per molecule. In the pH range from 3 to 10, rate of activity loss was most rapid at pH 10, slightly less rapid at pH 3, and reached a minimum near pH 5. The effects of pH and urea were additive in that the maximum rate of inactivation occurred at pH 10 in 8 M urea (97 per cent activity loss in 10 minutes), and the minimum rate st pH 5 in the absence of urea (20 per cent loss in 28 hours). <P> Inactivation was markedly inhibited by phosphate ions. A solution of protein which was O.36 M in phosphate at pH 8 lost activity very slowly when treated with thioglycolic acid, even in the presence of 4 M urea. These findings, together with the observation of other workers that polyvalent ions such as phosphate reverse the denaturetion of ribonuclease in urea, suggest that phosphate inhibits reduction by stabilizing the protein in its native configuration, whereas urea facilitates reduction by denaturing the protein. <P> Air oxidation of fully or partially inactivated protein resulted, in some cases, in the recovery of up to 4O per cent of the enzyme activity which had been lost as a result of reduction. <P> The relation between loss of activity and reduction was analyzed by correlating the data obtained in those experiments in which both the sulfhydryl concentration and the enzymic activity of samples of modified protein were determined. The experiments were carried out under a variety of conditions of pH and urea concentration. On the basis of these data, it is concluded that the inactivation of thioglycolate-treated ribonuclease is probably not a unique function of extent of reduction, but depends in part on the method by which the reduction is achieved.