Orientador: Ignez Caracelli / Banca: Francisco Carlos Lavarda / Banca: Regina Helena de Almeida Santos / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Neste trabalho foi estudado o modo de ligação de três moléculas pequenas ao DNA 5'-CGCGAATTCGCG-3', através da simulação computacional e análise em tela gráfica. Verificou-se que é possível utilizar o programa GOLD, baseado em algoritmos genéticos, em estudos envolvendo o DNA, uma vez que até o momento há apenas dois trabalhos publicados na base de dados Scopus (Portal de Periódicos da Capes) onde esta metodologia é utilizada. Também foi verificado que 1vzk, complexo cristalográfico do DNA com 2-(5-{4-[amino (imino)metil]fenil}-2-tienil)-1h-benzimidazol-6-carboximida (DB818), obtido do PDB é uma estrutura representativa para estudos no sulco menor. Foram investigados os modos de ligação dos seguintes ligantes: (a) DB818, obtido a partir da estrutura cristalográfica 1 vzk; (b) DAZJOE; [Cr(1,2-bis(naftilidenoamino)etano)(H2O)2], estrutura obtida do Cambridge Structural Database e (c) CR3NC, [Cr(2,3-bis{[(2-hidroxi-4-dietilamino) (fenil) (metileno)]amino}2-butenodinitrila) (H2O)2], cuja estrutura foi obtida por modelagem molecular, tomando como modelo DAZJOE. Os estudos de docking do DAZJOE em DNA sugerem que seu modo de ligação seria no sulco menor, porém sua interação não se dá com as bases AATTC como no caso do DB818, mas sim entre as bases ATTC. Quando os cálculos de docking foram realizados com a molécula CR3NC, que tem volume maior e mais flexibilidade nas extremidades, observou-se que a mesma posiciona-se no sulco maior. Este resultado está em concordância com dados experimentais disponíveis. Um mecanismo de quebra do DNA é sugerido, não devido à influência do crômio, mas sim devido à presença dos nitrogênios. Observou-se que a influência do metal é menor do que a da molécula complexada ao íon nas interações. / Abstract: In this work we studied the binding mode of some small molecules in the DNA 5'-CGCGAATTCGCG-3' through computer simulation and analysis in graphical screen. We found that it is possible to use the GOLD program, based on genetic algorithms in studies involving DNA, despite we found only two papers in the database Scopus (CAPES Portal of Journals) where this approach is used. It was also found that 1 vzk, crystallographic complex of the DNA with 2-(5-(a-[amino (imino) methyl] phenil) -2- thienyl)- 1h-benzimidazol-6-carboximide (DB818), obtained from PDB is a representative structure for studies in the minor groove. We investigated the binding mode of the following ligands: a) DB818, obtained from the 1vzk crystallographic structure, (d) DAZJOE, [Cr(1,2-bis(naphthylideneamino) ethane)(H2O)2], structure obtained from Cambridge Structural Database and (c) CR3NC, [Cr((2,3-bis[(2-hydroxy-4phenyl) (diethylamino) (methylene)] 2-amino butenedinitrile)(H2O)2, whose structure was obtained by molecular modeling, taking DAZJOE as model. The DAZJOE docking's studies in DNA suggest that its binding mode would be in the minor groove, but their interaction is not given with the bases AATTC as for the DB818, but between the bases ATTC. When the docking calculations were performed with CR3NC molecule, which has larger volume and more flexibility in the extremities, we observed that in take place in major groove. This result is in agreement with experimental data available. It is suggested a DNA break mechanism, but not due to the influence of chromium, but the nitrogens. It was observed that the influence of the metal is lower than the ionophore in interactions. / Mestre

Shao, Lei = 金顆粒納米晶中角度、能量和空間位置分辨的表面等離子共振耦合 / 邵磊. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Abstracts in English and Chinese. / Shao, Lei = Jin ke li na mi jing zhong jiao du, neng liang he kong jian wei zhi fen bian de biao mian deng li zi gong zhen ou he / Shaolei. / Abstract --- p.1 / 摘要 --- p.iii / Acknowledgement --- p.v / Table of Contents --- p.vii / List of Figures --- p.ix / List of Tables --- p.xiv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Localized Surface Plasmon Resonances of Noble Metal Nanocrystals --- p.3 / Chapter 1.1.1 --- Dielectric Functions of Noble Metal Nanocrystals --- p.3 / Chapter 1.1.2 --- Absorption and Scattering of Light by Noble Metal Nanoparticles --- p.7 / Chapter 1.2 --- Coupling between Localized Surface Plasmons --- p.14 / Chapter 1.2.1 --- Theoretical Treatments for Plasmon Coupling --- p.14 / Chapter 1.2.2 --- Unique Properties Resulting from Plasmon Coupling --- p.15 / Chapter 1.2.3 --- Applications Based on Plasmon Coupling --- p.17 / Chapter 1.3 --- Outline of Thesis --- p.18 / Chapter 2. --- Growth of Gold Nanocrystals and Characterization Techniques --- p.26 / Chapter 2.1 --- Growth of Gold Nanocrystals --- p.26 / Chapter 2.2 --- Characterization Techniques --- p.29 / Chapter 3. --- Surface Plasmon Coupling in Homodimers of Elongated Gold Nanocrystals --- p.34 / Chapter 3.1 --- Formation of Homodimers of Elongated Gold Nanocrystals --- p.35 / Chapter 3.2 --- Angle-Resolved Plasmon Coupling in Gold Nanorod Dimers --- p.37 / Chapter 3.2.1 --- Experimental Results --- p.39 / Chapter 3.2.2 --- FDTD Calculations --- p.43 / Chapter 3.2.3 --- Dipolar Modeling --- p.49 / Chapter 3.3 --- Effect of the Head Shape on the Plasmon Coupling --- p.57 / Chapter 3.4 --- Summary --- p.60 / Chapter 4. --- Surface Plasmon Coupling in Heterodimers of Gold Nanocrystals --- p.64 / Chapter 4.1 --- Formation of Heterodimers of Gold Nanocrystals --- p.65 / Chapter 4.2 --- Energy-Resolved Plasmon Coupling in Gold Nanorod Heterodimers --- p.67 / Chapter 4.3 --- Position-Resolved Plasmon Coupling in Gold Nanorod-Nanosphere Heterodimers --- p.70 / Chapter 4.3.1 --- Experimental Results --- p.71 / Chapter 4.3.2 --- FDTD Calculations --- p.75 / Chapter 4.4 --- Summary --- p.83 / Chapter 5. --- Summary and Conclusion --- p.87

Lu, Chenxi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 53-60). / Abstract also in Chinese. / Chapter Chapter 1: --- Introduction --- p.1 / Chapter Chapter 2: --- Methodology --- p.5 / Chapter 2.1: --- Modified Rescaled Range Statistic R/S --- p.5 / Chapter 2.2: --- Fractionally Integrated GARCH (FIGARCH) Model --- p.7 / Chapter Chapter 3: --- Long memory in gold returns and volatility --- p.9 / Chapter 3.1: --- Data --- p.9 / Chapter 3.2: --- Empirical results of the modified R/S statistic and FIGARCH model --- p.11 / Chapter 3.3 --- Self-similarity of long memory in the gold market --- p.15 / Chapter Chapter 4: --- Structural break of long memory in the gold market --- p.18 / Chapter 4.1: --- Structural break in long memory feature --- p.18 / Chapter 4.2: --- Forward rolling and backward rolling methodology and empirical evidence --- p.20 / Chapter 4.3: --- Evidence for the structural break using the FIGARCH model --- p.31 / Chapter Chapter 5: --- Long memory in the international diamond market --- p.40 / Chapter 5.1: --- International diamond cartel --- p.40 / Chapter 5.2: --- Data --- p.43 / Chapter 5.3: --- Empirical results --- p.45 / Chapter Chapter 6: --- Conclusions --- p.51 / Reference --- p.53 / Appendix 1 --- p.61

Seven rats were trained on Fixed Ratio 20 and two on Fixed Ratio 12 Escape Schedules until a stable baseline was established. Five of the subjects were administered gold thioglucose, three received gold thiomalate, and one was injected with gold, gold thioglucose, and gold thiomalate, allowing for an intrasubject comparison. Colloidal gold appeared to suppress response rate for one or two sessions, while gold thioglucose and gold thiomalate suppressed normal response rates from several to a number of sessions. This response rate suppression was often followed by gradual recovery, although in several subjects recovery of response rate could not be achieved prior to termination of the experiments. The drop in response rate was more consistent for the gold thiomalate-treated subjects than for the gold thioglucose group. A toxic effect of the injected compounds was manifest as a loss of weight, which was regularly associated with a drop in response rate. This weight reduction was greatest in the gold thiomalate-injected animals, indicating that gold thiomalate is probably more toxic than gold thioglucose to rats. Tolerance was developed for gold thioglucose and gold thiomalate, as indicated by smaller response rate decrements after repeated injections of the compound. As a consequence of repeated drug administrations, the animals demonstrated that they could tolerate a 1 milligram per gram of body weight dose of gold thioglucose if the dosage was increased gradually from a low-dosage initial injection. This dosage of 1 milligram per gram of body weight is double the amount required to produce demonstrable hypothalamic lesions in the rat. Previous investigations have failed to demonstrate this degree of tolerance in rats, primarily because the animals did not have the opportunity to adapt themselves to this treatment. Decrease in spontaneous activity on a balance beam apparatus was observed in several rats following administration of the larger gold thioglucose dosages (i.e., 0.5 milligrams per gram of body weight to 1.0 milligram per gram of body weight), as well as following the administration of gold thiomalate. Dosages of 20 milligrams to 50 milligrams of gold chloride were lethal to two rats. The heavy dosage of gold thioglucose administered to the female rat subjects at Utah State University (i.e., up to 1 mg per gram of body weight), although potentially producing extensive hypothalamic lesions, did not produce demonstrable hyperphagia or obesity, probably due to the anorexia and hypophagia associated with liver and kidney damage,which could counteract the hyperphagia expected to be associated with the extensive hypothalamic lesions produced at dosages over 0.5 milligram per gram of body weight following gold thioglucose administration.

Selbstorganisierte Nanodrähte auf Halbleiteroberflächen ermöglichen die Untersuchung von Elektronen in niedrigen Dimensionen. Interessanterweise werden die elektronischen Eigenschaften des Systems von dessen Dimensionalität bestimmt, und das noch über das Quasiteilchenbild hinaus. Das quasi-eindimensionale (1D) Regime zeichnet sich durch eine schwache laterale Kopplung zwischen den Ketten aus und ermöglicht die Ausbildung einer Peierls Instabilität. Durch eine Nesting Bedingung in der Fermi Fläche kommt es zu einer Bandrückfaltung und damit zu einem isolierenden Grundzustand. Dies wird begleitet von einer neuen Überstruktur im Realraum, die mit dem Nestingvektor korrespondiert. In früheren Nanodrahtsystemen wurde ein solcher Effekt gezeigt. Dazu geh ̈oren Indium Ketten auf Si(111) und die Gold rekonstruierten Substrate Si(553) und Si(557). Die Theorie sagt jedoch einen weiteren Zustand voraus, der nur im perfekten 1D Grenzfall existiert und der bei geringster Kopplung mit höheren Dimensionen zerstört wird. Dieser Zustand wird Tomonaga-Luttinger Flüssigkeit (TLL) genannt und führt zu einem Zusammenbruch des Quasiteilchenbildes der Fermi-Flüssigkeit. Hier sind nur noch kollektive Anregungen der Elektronen erlaubt, da die starke laterale Einschränkung zu einer erhöhten Kopplung zwischen den Teilchen führt. Dadurch treten interessante Effekte wie Spin-Ladungs-Trennung auf, bei dem sich die Ladung und der Spin eines Elektrons entkoppeln und getrennt voneinander durch den Nanodraht bewegen können. Bis heute wurde solch ein seltener Zustand noch nicht an einer Oberfläche beobachtet. In dieser Arbeit wird ein neuer Ansatz zur Herstellung von besser definierten 1D Ketten gewählt. Dazu wird die Au-rekonstruierte Ge(001) Nanodraht-Oberfläche untersucht. Für die Präparation des Substrates wird ein neues Rezept entwickelt, welches eine langreichweitig geordnete Oberfläche erzeugt. Um das Wachstum der Nanodrähte zu optimieren wird das Wachstums-Phasendiagramm ausgiebig untersucht. Außerdem werden die strukturellen Bausteine der Ketten sehr genau beschrieben. Es ist bemerkenswert, dass ein struktureller Phasenübergang der Ketten oberhalb von Raumtemperatur gefunden wird. Aufgrund von spektroskopischen Untersuchungen kann eine Peierls Instabilität als Ursache ausgeschlossen werden. Es handelt sich um einen 3D-Ising-Typ Übergang an dem das Substrat ebenfalls beteiligt ist. Die Untersuchungen zur elektronischen Struktur der Ketten zeigen zwei deutliche Erkennungsmerkmale einer TLL: Ein potenzgesetzartiger Verlauf der Zustandsdichte und universales Skalenverhalten. Daher wird zum ersten Mal eine TLL an einer Oberfläche nachgewiesen, was nun gezielt lokale Untersuchungen und Manipulationen ermöglicht. Dazu gehören (i) Dotierung mit Alkalimetallen, (ii) die Untersuchung von Kettenenden und (iii) die einstellbare Kopplung zwischen den Ketten durch zusätzliche Goldatome. Damit wird ein wichtiger Beitrag zu theoretischen Vorhersagen und Modellen geliefert und somit das Verständnis korrelierter Elektronen vorangetrieben. / Self-organized nanowires at semiconductor surfaces offer the unique opportunity to study electrons in reduced dimensions. Notably the dimensionality of the system determines it’s electronic properties, beyond the quasiparticle description. In the quasi-one-dimensional (1D) regime with weak lateral coupling between the chains, a Peierls instability can be realized. A nesting condition in the Fermi surface leads to a backfolding of the 1D electron band and thus to an insulating state. It is accompanied by a charge density wave (CDW) in real space that corresponds to the nesting vector. This effect has been claimed to occur in many surface-defined nanowire systems, such as the In chains on Si(111) or the Au reconstructions on the terraced Si(553) and Si(557) surfaces. Therefore a weak coupling between the nanowires in these systems has to be concluded. However theory proposes another state in the perfect 1D limit, which is completely destroyed upon slight coupling to higher dimensions. In this so-called Tomonaga-Luttinger liquid (TLL) state, the quasiparticle description of the Fermi liquid breaks down. Since the interaction between the electrons is enhanced due to the strong confinement, only collective excitations are allowed. This leads to novel effects like spin charge separation, where spin and charge degrees of freedom are decoupled and allowed to travel independently along the 1D-chain. Such rare state has not been realized at a surface until today. This thesis uses a novel approach to realize nanowires with improved confinement by studying the Au reconstructed Ge(001) surface. A new cleaning procedure using piranha solution is presented, in order to prepare a clean and long-range ordered substrate. To ensure optimal growth of the Au nanowires the phase diagram is extensively studied by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The structural elements of the chains are revealed and described in high detail. Remarkably a structural phase transition of the delicate wire structure is found to occur above room temperature. Due to the lack of energy gaps a Peierls transition can be excluded as its origin. The transition is rather determined as 3D Ising type and therefore includes the substrate as well. Two hallmark properties of a TLL are found in the Au/Ge(001) wires by spectroscopic studies: Power-law suppression of the density of states (DOS) and universal scaling. This impressively proves the existence of a TLL in these chains and opens up a gateway to an atomic playground. Local studies and manipulations of a TLL state become possible for the first time. These comprise (i) doping by alkaline atoms, (ii) studies on chain ends and (iii) tunable coupling between the chains by additional Au atoms. Most importantly these manipulations offer input and test for theoretical models and predictions, and are thereby ultimately advancing the field of correlated electrons.

Atomic chains, often called nanowires, form in a self-organized process after the adsorption of metal atoms. These wires are spatially well confined representing a close approach of a true one-dimensional structure. The low-dimensional architecture thereby often leads to anisotropic electronic states with vanishing interchain interaction. In the presence of weak coupling to the substrate a one-dimensional metal can experience a phase transition according to Peierls into an insulating ground state upon temperature, which is accompanied by a periodic lattice distortion. Without any coupling a strict onedimensional regime is reached, where the common Fermi liquid description breaks down with the quasi-particles being replaced by collective excitations of spin and charge. This state is referred to as a Tomonaga-Luttinger liquid (TLL), which has been observed so far only in anisotropic bulk materials. An experimental fingerprint for both phenomena can be obtained from the electronic states close to the chemical potential, i.e. the Fermi energy. Using a semiconducting substrate provides the best observation conditions since any bulk projection onto the interesting bands is avoided. In case of Au/Ge(001) the growth of gold-induced chains is guided by the dimerized bare Ge (2×1) reconstruction yielding two different domains of wires rotated by 90° going from one terrace to the next by a single height step. The superior wetting capabilities of gold on germanium enables a complete coverage of the Ge(001) surface with longrange ordered wires. Their length scale and defect density is limited by the underlying substrate, for which a cleaning procedure is introduced based on wet-chemical etching followed by thermal dry oxidation. The band structure of Au/Ge(001) is investigated by angle-resolved photoelectron spectroscopy as a function of temperature. Two states are observed: a two-dimensional metallic state with hole-like dispersion and a one-dimensional electron pocket, whose band-integrated spectral function does not show the typical Fermi distribution at the chemical potential. Instead, a decrease of spectral weight applies following a power-law. This behavior can be well explained within the Tomonaga-Luttinger liquid theory which replaces the Fermi-Landau formalism in strictly one-dimensional systems. To enable theoretical modeling, a structural analysis was performed on the basis of surface x-ray diffraction (SXRD). From the in-plane scattering data a Patterson-map could be extracted leading to in-plane distances between gold atoms in the unit cell. This provides the first step towards a complete structural model and therefore towards a band structure calculation. First successful attempts have been made to manipulate the system by controlled adsorption of potassium. Here, an n-type doping effect is observed for submonolayer coverage whereas slightly increased coverages in combination with thermal energy lead to a new surface reconstruction. / Atomare Ketten, sogenannte Nano-Drähte, entstehen durch Selbstorganisation adsorbierter Metallatome auf einer Halbleiteroberfläche. Aufgrund der starken räumlichen Einschränkung der Ladungsträger innerhalb dieser Ketten entsteht dabei oftmals eine metallische Bandstruktur mit starker Anisotropie. Im Falle phononischer Ankopplung an das Substrat kann so ein eindimensionales (1D) Metall instabil gegen eine periodische Gitterverzerrung werden, bei der es zu einer Ausbildung einer Energielücke kommt. Dieser Metall-Isolator-Übergang wird dabei als Peierls Übergang bezeichnet. Für verschwindend geringe Kopplung der Ketten untereinander bzw. an das Substrat, d.h. im strikt eindimensionalen Fall, bricht das Fermi Flüssigkeitsmodell für dreidimensionale (3D) Metalle zusammen. Dessen Quasiteilchen werden durch kollektive Anregungen von Spin und Ladung ersetzt. Diesen Zustand bezeichnet man als Tomonaga-Luttinger Flüssigkeit. Beide Phänomene, Peierlsübergang und Tomonaga-Luttinger Flüssigkeit lassen sich anhand der elektronischen Bandstruktur experimentell nachweisen. Bei dem hier untersuchten Probensystem handelt es sich um Gold-induzierte Nandrähte auf der Germanium (001)-Oberfläche, kurz Au/Ge(001). Deren Wachstum erfolgt epitaktisch entlang der durch das Substrat vorgegebenen Dimer-Reihen, welche die freie Germaniumoberfläche in Form einer (2×1)-Symmetrie einnimmt. Die abwechselnde Stapelfolge ABAB des Substrates führt dabei zu zwei unterschiedlichen Drahtrichtungen, die jeweils um 90° zueinander gedreht sind, wenn man eine Einfachstufe von 1.4 A von einer A-Terrasse auf eine B-Terrasse oder umgekehrt geht. Die vorherrschende Kinetik während der Gold-Deposition bzw. das Benetzungsverhalten ermöglicht dabei eine vollständige Bedeckung der vormals freien Oberfläche mit Nanodrähten, deren Abmessungen einzig und allein durch Defekte bzw. die Größe der darunterliegenden Ge-Terrasse begrenzt sind. Um die Längenskala der Subtrat-Terrassen zu optimieren, wurde eine Reinigungsprozedur für Ge (001) entwickelt, bei der nass-chemisches Ätzen mit anschliessender Trocken-Oxidation zum Einsatz kommt. Die darauf aufbauenden Nanodrähte wurden im Anschluss mittels winkelaufgelöster Photoelektronenspektroskopie auf ihre elektronische Bandstruktur untersucht. Dabei wurden zwei neuartige Zustände beobachtet: ein metallischer, zweidimensionaler Loch-Zustand, der seinen Ursprung höchstwahrscheinlich in tieferen Schichten des Germaniums hat; und ein eindimensionaler Oberflächenzustand mit elektronenartiger Dispersion, dessen bandintegrierte Spektralfunktion von der einer Fermiflüssigkeit abweicht. Stattdessen wird ein exponentieller Abfall des spektralen Gewichtes als Funktion der Energie zum Ferminiveau hin beobachtet. Dieses Verhalten kann über einen weiten Temperaturbereich beobachtet werden und lässt sich mit der Tomonaga-Luttinger Flüssigkeit für strikt eindimensionale Systeme erklären. Zum weiteren theoretischen Verständnis dieses Phänomes, beispielsweise durch Bandstrukuturrechnungen mittels Dichte-Funktional-Theorie, bedarf es der genauen Kenntnis der atomaren Struktur dieser Ketten. Selbige wurde mittels Oberflächenröntgenbeugung (engl. surface x-ray diffraction, SXRD) untersucht. Auf Basis der gewonnenen Patterson-Karte lassen sich Rückschlüsse auf die interatomaren Abstände der Goldatome untereinander in der Einheitszelle ziehen. Dies stellt einen ersten wichtigen Schritt auf dem Weg zu einem vollständigen Strukturmodell dar. Darüber hinaus wurden erste vielversprechende Schritte unternommen, das Nanodrahtsystem kontrolliert zu manipulieren. Durch geringfügige, zusätzliche Deposition von Kalium konnte dabei eine schrittweise Erhöhung der Bandfüllung erzielt werden. Für weitergehende Kaliumanlagerungen im (Sub-)Monolagenbereich konnte sogar eine neue Rekonstruktion erzielt werden.

This dissertation mainly contains two parts: one is C-X (C, O, S) bond formation through gold(I) catalysis, one is new applications via gold(I/III) redox catalysis. In first part, gold(I) catalysts would be introduced and their general applications, then the TA-Au species will be emphasized including the design, synthesis, characters and their application in catalysis. The applications are well developed during the past decade in our group, but here only involves three examples regarding C-C, C-O and C-S bond formations. From these effective applications, the unique stability and reactivity of TA-Au will be studied and explained, which is the reason and value of TA-Au discovery. In second part, gold(I/III) redox catalysis will be presented through two application examples: cross-coupling of terminal alkynes, multiple bond di-functionalization. The most challenging part for coupling reactions is the competition between homo-coupling and cross-coupling products, while in our project, we have successfully developed a new method to selectively obtain cross-coupling as major product to homo-coupling product (ratio 12:1). Later on, we found a new method to achieve gold (I/III) redox cycle by using mild oxidant diazonium salt instead of PIDA or Selectfluor strong oxidant. The new mild and efficient method have largely extended the application of gold(I/III) redox catalysis into organic synthesis. In sum, the new gold catalysts and catalysis methods reported here are important to the development of gold catalysis field, which are critical and useful to help people understand the reason of applying noble gold species as catalysts, and the advantages that other metals do not have.

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Ion exchange equilibria are presented for [ ]??? ??? Au(CN)2 / Cl , [ ]??? ??? Au(CN)2 / SCN and SCN??? / Cl??? in aqueous solution, and in various mixed solvents, at 303K using Purolite A500 as the ion-exchanger. The mixed solvents investigated include water-acetone, water-dimethylsulfoxide (DMSO) and water-N-methyl-2-pyrrolidone (NMP). In aqueous solution, the selectivity of Purolite A500 for a given anion increases in the order: [ ]??? ??? &lt ??? &lt Cl SCN Au(CN)2 . This selectivity sequence confirms the high affinity of the ion exchange resin for the [ ]??? Au(CN)2 species. In mixed solvents, however, the selectivity of Purolite A500 for [ ]??? Au(CN)2 decreases with an increase in the composition of the organic solvent in the external solution. Mixed solvents containing greater than 60 mol% organic solvent are preferred for the displacement of [ ]??? Au(CN)2 from the resin. The effectiveness of a given type of mixed solvent generally increases in the following order: DMSO &it acetone &it NMP. The ion exchange equilibria are correlated using the Law of Mass Action, modified with activity coefficients, to determine the equilibrium constant for each binary system. The fitted values of the equilibrium constants are consistent with the trends observed in the ion exchange isotherms. The accuracy of the correlation results in the mixed solvent systems range from 1 to 10% and this is similar to the level of accuracy obtained for the ion exchange equilibria in aqueous solution. From these results it can be concluded that the Law of Mass Action is equally valid in mixed solvent systems. The variation in the equilibrium constant with mixed solvent composition, for a given binary system, correlates well with the dielectric constant of the mixed solvent. For a given value of the dielectric constant, however, the equilibrium constant, however, the equilibrium constant is dependent on the type of mixed solvent. A fundamental relationship is derived between the equilibrium constants and the Gibbs energies of transfer associated with the solvation of the ions in the mixed solvents. Based on this relationship, the redistribution of ions between the pore solution and the bulk mixed solvent, appears to be the most significant factor that governs the selectivity of the resin in mixed solvent systems.