Magister Scientiae - MSc (Chemistry) / Although cadmium and lead chalcogenide quantum dot have excellent optical and photoluminescent properties that are highly favorable for biological applications, there still exists increasing concerns due to the toxicity of these metals. We, therefore, report the synthesis of new aqueous soluble IrSe quantum dot at room temperature utilizing a bottom-up wet chemistry approach. NaHSe and H2IrCl6 were utilized as the Se and Ir source, respectively. High-resolution transmission electron microscopy reveals that the synthesized 3MPA-IrSe Qd are 3 nm in diameter. The characteristics and properties of the IrSe Qd are investigated utilizing, Selected Area electron diffraction, ATR- Fourier Transform Infra-Red Spectroscopy, Energy Dispersive X-ray spectroscopy, Photoluminescence, Cyclic Voltammetry and chronocoulometry. A 3 fold increase in the optical band gap of IrSe quantum dot in comparison to reported bulk IrSe is observed consistent with the effective mass approximation theory for semiconductor materials of particles sizes < 10 nm. The PL emission of the IrSe quantum dot is at 519 nm. Their electro-activity is studied on gold electrodes and exhibit reduction and oxidation at - 107 mV and +641 mV, with lowered reductive potentials. The synthesized quantum dot are suitable for low energy requiring electrochemical applications such as biological sensors and candidates for further investigation as photoluminescent biological labels.

A extratibilidade de sais de fosfônio foi aproveitada para elaborar método de separação Ir-Rh, mediante a extração do sal de trifenil n-propil fosfônio do cloro-complexo de Ir(IV,) em clorofórmio. O coeficiente de extração de 99,2%, permite retirar o irídio do meio aquoso com grande eficiência. O irídio assim separado é determinado diretamente, por via espectrofotométrica, em 494 m&#181;, em faixa de concentração de 5,0 a 50,0 &#181;g/ml. Pd(II), Pt(IV) e Os(IV) interferem e são eliminados previamente, assim como Au(III). Os ânions interferentes, I-, Br- e SCN- são também eliminados previamente. Muitos íons podem estar presentes, tais como Co(II),Cu(II), Mn(II), Fe(III), Ni(II), As(V), Sb(V), NO3-, ClO4- e SO4--. Após a separação do Ir (IV), o Rh(III) que permanece, na solução é complexado com íons azoteto e extraído em clorofórmio depois de precipitado com íons trifenil n-propil fosfônio, sendo o coeficiente de extração de 98,3%. A determinação ê também feita no próprio solvente, mediante medida espectrofotométrica em 404-408 m&#181;, para um intervalo de concentração de . 10,0 a 70,0 &#181;g/ml. Uma separação envolvendo Os(IV), Pd(II)e Pt(IV) foi elaborada, eliminando-se Pd(II) e Pt(IV) por extração de ambos em metil n-butil cetona a partir de uma solução contendo SCN-. O Os(IV) é determinado na solução aquosa na forma de OsC16-- por medida espectrofotométrica em 370 m&#181;, válida para a faixa de concentração de 2,0 a 20,0 &#181;g/m1. / Abstract not available.

Abstract Platinum group elements (PGEs) have a high commercial value and variety of applications in different fields of industry. One of the well-known applications is the use of palladium, platinum and rhodium in the catalytic converters of automobiles to reduce the amount of harmful gases emitted to the environment. Advanced analytical methods are needed to deal with issues related to development of new catalyst materials, recycling of PGEs from spent materials and for monitoring PGE emissions to the environment. In the first part of this study the emphasis was on the catalyst materials. Especially, reliable determination of ruthenium content in catalyst materials required further studies. Consequently, acid digestions in closed vessels using a microwave oven or high pressure asher were compared with a previously reported fusion method. Furthermore, the recovery of PGEs from spent materials is important due to many factors, for example, the high value of these metals, environmental aspects related to their production and possible availability issues in the future. Thus, utilization of microwave-assisted leaching and cloud point extraction (CPE) for the recovery of palladium, platinum, rhodium and ruthenium from catalyst materials was investigated. The second part of this study concentrated on the PGEs in environmental samples and the analytical challenges related to PGE determinations with inductively coupled plasma mass spectrometry (ICP-MS). Due to the use of PGEs in catalytic converters of automobiles, they are emitted to the roadside environment. The use of Pleurozium schreberi, a terrestrial moss, for active biomonitoring of these emissions was evaluated. Advanced analytical methods were needed to perform interference-free determinations of palladium, platinum and rhodium in these samples. Two alternative approaches for interference elimination were studied. Firstly, the interfering elements were removed using CPE as a chemical separation method. Secondly, interferences were eliminated using ammonia as a reaction gas with the novel ICP-MS/MS (inductively coupled plasma tandem mass spectrometry) technique. / Tiivistelmä Platinaryhmän alkuaineita hyödynnetään monissa teknisissä sovelluksissa. Yksi tunnetuimmista on autoliikenteen haitallisten päästöjen vähentäminen käyttäen palladiumia, platinaa ja rodiumia autojen pakokaasukatalysaattoreissa. Luotettavia analyysimenetelmiä tarvitaan esimerkiksi kehitettäessä uusia katalyyttimateriaaleja, kierrätettäessä platinaryhmän alkuaineita käytetyistä materiaaleista tai seurattaessa platinaryhmän alkuaineiden määrää ympäristössä. Tämän tutkimuksen ensimmäinen osa liittyi katalyyttien ruteniumpitoisuuksien määrittämiseen ja platinaryhmän alkuaineiden kierrätykseen katalyyttimateriaaleista. Erityisesti näytteenhajotusvaihe aiheuttaa usein ongelmia ruteniummäärityksissä. Tämän vuoksi tutkimuksessa verrattiin keskenään mikroaaltotekniikalla tai korkeapainetuhkistimella suoritettuja happohajotuksia ja aiemmin raportoidulla sulatemenetelmällä suoritettuja hajotuksia. Mikroaaltoavusteista liuotusta sovellettiin yhdessä samepisteuuton kanssa tutkittaessa katalyyttimateriaalien palladiumin, platinan, rodiumin ja ruteniumin kierrätysmahdollisuuksia. Aihe on ajankohtainen, kun huomioidaan platinaryhmän alkuaineiden korkea hinta, niiden tuotantoon liittyvät ympäristöasiat sekä saatavuuteen liittyvät epävarmuustekijät. Tutkimuksen toisessa osassa keskityttiin ympäristönäytteisiin ja erityisesti niiden ICP-MS -analytiikan (induktiiviplasmamassaspektrometria) haasteisiin. Autojen katalysaattoreista lähtöisin olevia platinaryhmän alkuaineita päätyy ympäristöön lähinnä teiden varsille. Näitä päästöjä arvioitiin aktiivista biomonitorointia käyttäen. Spektraaliset häiriöt vaikeuttivat kerättyjen sammalnäytteiden (Pleurozium schreberi) palladium-, platina- ja rodiumpitoisuuksien määrityksiä. Tämän vuoksi mittauksissa esiintyvien häiriöiden poistossa hyödynnettiin kahta eri lähestymistapaa. Näistä ensimmäisessä häiritsevät alkuaineet poistettiin kemiallisen erotusmenetelmän, samepisteuuton, avulla. Toisessa tavassa häiriöt poistettiin uudella ICP-MS/MS -tekniikalla (induktiiviplasmatandemmassaspektrometria) käyttäen ammoniakkia reaktiokaasuna.

Philosophiae Doctor - PhD / In this study, the OMCVD method is demonstrated as a powerful, fast, economic and environmental friendly method to produce a set of PGMelectrocatalysts with different supports, metal content and metal alloys in one step and without the multiple processing stages of impregnation, washing, drying, calcinationsand activation. / South Africa

The aim of this thesis is the actual elaboration literature search concerning the issue of platinum group metals in the environment, determination of platinum and palladium in great urban agglomerations. It includes chemical and physical properties, occurrence and platinum and palladium cycle in the environment. It also contains methods for extraction and determination of platinum and palladium.

The aim of this thesis is the elaboration of a detailed literature review on the use of ion exchangers for the preconcentration of platinum group metals. This work contains an actual literature review on this issue. In this work you will find information about the current occurrence of platinum metals in the environment, their impact on health, properties, resources and the use. There are also described ways of decomposition, extraction and use of ion exchangers. In the experimental part this thesis deals with optimization of ion exchangers and following application of real samples from the city of Brno.

Background: Platinum group metal (PGM) mining and refining is a large constituent of the mining sector of South Africa and contributes significantly to the gross domestic product. The PGMs include the rare metals platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). During the refining process workers are potentially exposed to various chemical forms of the PGMs via the respiratory and dermal exposure routes. Historically, emphasis has been on respiratory exposure while the extent of skin exposure is still unknown. Among the different forms of PGMs, the salts are potential sensitisers, with platinum being a known respiratory sensitiser. Workers occupationally exposed to platinum and rhodium have reported respiratory as well as skin symptoms. However, it is unknown if these metals in the salt form are permeable through human skin, and whether dermal exposure could contribute to sensitisation. Evidence regarding differences between African and Caucasian skin anatomy and structure, as well as permeation through skin is contradictory, and no information is available on metal permeation through African skin. The in vitro diffusion method has been utilised successfully in occupational toxicology to demonstrate that metals such as chromium, cobalt and nickel, to name a few, permeate through human skin. The permeability of platinum and rhodium has not been investigated previously. Aims and objectives: The research aim was to obtain insight into the permeability of platinum and rhodium through intact human skin and to provide information needed to determine the potential health risk following dermal exposure to these metals. The specific objectives included: (i) to critically review the in vitro diffusion method that is used to determine the permeability of metals through human skin, (ii) to investigate the permeation of potassium tetrachloroplatinate (K2PtCl4) and rhodium chloride (RhCl3) as representative PGM salts through intact human skin over a 24-hour period, (iii) to evaluate the difference in permeability of platinum and rhodium through intact human skin, (iv) to evaluate the difference in permeability of platinum through intact African and Caucasian human skin. Methods: Abdominal skin obtained after cosmetic procedures was obtained from five female Caucasian and three female African donors between the ages of 28 and 52 with ethical approval from the North-West University. Full thickness skin tissue was mounted in a vertical Franz diffusion cell. Skin integrity was tested by measuring the electrical resistance across the skin before and after conclusion of the experiments, using a Tinsley LCR Data bridge Model 6401. The donor solution of 32.46 mg K2PtCl4 in 50 ml of synthetic sweat (pH 6.5), and 43.15 mg RhCl3 in 50 ml of synthetic sweat (pH 6.5) was prepared. The donor solution was applied to the stratum corneum side of the skin and physiological receptor solution (pH 7.35) was added to the receptor compartment. The concentration of the metals in the receptor solution was determined by high resolution inductively coupled plasma-mass spectrometry after extraction at various intervals during the 24 hours of the study. After completion of the study, the skin was rinsed four times to remove any platinum or rhodium remaining on the skin surface. The skin was digested using hydrogen peroxide, nitric acid and hydrochloric acid during different steps to determine the mass of the metals remaining in the skin by inductively coupled plasma-optical emission spectrometry. Results: The comparison of published in vitro skin permeation studies involving metals is impeded by the variations in the experimental design and dissimilarity in the reporting of results. Differences in experimental design included, most noticeably, the use of various donor and receptor solutions, different temperatures wherein the receptor compartment was placed, differences in skin thickness and variations in exposed skin surface areas. The metals considered in the review, namely chromium, cobalt, gold, lead, mercury, nickel, platinum, rhodium and silver, permeate through intact human skin under physiological conditions. Large variations in the permeability results were observed, with the notable differences in methodology as the probable reason. Results obtained from the in vitro experiments indicate that platinum and rhodium permeated through intact Caucasian skin with flux values of 0.12 and 0.05 ng/cm2/h, respectively. The cumulative mass of platinum (2.57 ng/cm2) that permeated after 24 hours of exposure was statistically significantly (p = 0.016) higher than rhodium permeation (1.11 ng/cm2). The mass of platinum (1 459.47 ng/cm2) retained in the skin after 24 hours of exposure was statistically significantly (p < 0.001) higher than rhodium retention (757.04 ng/cm2). The comparison of permeability between two different racial groups indicates that platinum permeated through the skin of both racial groups with the flux through African skin found as 1.93 ng/cm2/h and 0.27 ng/cm2/h through Caucasian skin. The cumulative mass of platinum permeated after 24 hours of exposure was statistically significantly (p = 0.044) higher through African skin (37.52 ng/cm2) than Caucasian skin (5.05 ng/cm2). The retention of platinum in African skin (3 064.13 ng/cm2) was more than twice the mass retained in Caucasian skin (1 486.32 ng/cm2). Conclusions: The in vitro diffusion method is an applicable method to determine skin permeability of metals. However, the experimental design and format of data reporting should be standardised to enable comparison of results from different studies. Platinum and rhodium permeated through intact human skin, with platinum permeation significantly higher. African skin was significantly more permeable by platinum than Caucasian skin. Both platinum and rhodium were retained inside the skin after 24 hours of exposure, possibly forming a reservoir which could contribute to continued permeation through the skin even after removal thereof from the skin. Platinum and rhodium permeated through full thickness skin and thereby could possibly contribute to local skin symptoms such as dermatitis and urticaria found in occupationally exposed workers. By permeating through the upper layers of the skin, these metals could potentially reach the viable epidermis and contribute to sensitisation. / PhD (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015

Background: Platinum group metal (PGM) mining and refining is a large constituent of the mining sector of South Africa and contributes significantly to the gross domestic product. The PGMs include the rare metals platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). During the refining process workers are potentially exposed to various chemical forms of the PGMs via the respiratory and dermal exposure routes. Historically, emphasis has been on respiratory exposure while the extent of skin exposure is still unknown. Among the different forms of PGMs, the salts are potential sensitisers, with platinum being a known respiratory sensitiser. Workers occupationally exposed to platinum and rhodium have reported respiratory as well as skin symptoms. However, it is unknown if these metals in the salt form are permeable through human skin, and whether dermal exposure could contribute to sensitisation. Evidence regarding differences between African and Caucasian skin anatomy and structure, as well as permeation through skin is contradictory, and no information is available on metal permeation through African skin. The in vitro diffusion method has been utilised successfully in occupational toxicology to demonstrate that metals such as chromium, cobalt and nickel, to name a few, permeate through human skin. The permeability of platinum and rhodium has not been investigated previously. Aims and objectives: The research aim was to obtain insight into the permeability of platinum and rhodium through intact human skin and to provide information needed to determine the potential health risk following dermal exposure to these metals. The specific objectives included: (i) to critically review the in vitro diffusion method that is used to determine the permeability of metals through human skin, (ii) to investigate the permeation of potassium tetrachloroplatinate (K2PtCl4) and rhodium chloride (RhCl3) as representative PGM salts through intact human skin over a 24-hour period, (iii) to evaluate the difference in permeability of platinum and rhodium through intact human skin, (iv) to evaluate the difference in permeability of platinum through intact African and Caucasian human skin. Methods: Abdominal skin obtained after cosmetic procedures was obtained from five female Caucasian and three female African donors between the ages of 28 and 52 with ethical approval from the North-West University. Full thickness skin tissue was mounted in a vertical Franz diffusion cell. Skin integrity was tested by measuring the electrical resistance across the skin before and after conclusion of the experiments, using a Tinsley LCR Data bridge Model 6401. The donor solution of 32.46 mg K2PtCl4 in 50 ml of synthetic sweat (pH 6.5), and 43.15 mg RhCl3 in 50 ml of synthetic sweat (pH 6.5) was prepared. The donor solution was applied to the stratum corneum side of the skin and physiological receptor solution (pH 7.35) was added to the receptor compartment. The concentration of the metals in the receptor solution was determined by high resolution inductively coupled plasma-mass spectrometry after extraction at various intervals during the 24 hours of the study. After completion of the study, the skin was rinsed four times to remove any platinum or rhodium remaining on the skin surface. The skin was digested using hydrogen peroxide, nitric acid and hydrochloric acid during different steps to determine the mass of the metals remaining in the skin by inductively coupled plasma-optical emission spectrometry. Results: The comparison of published in vitro skin permeation studies involving metals is impeded by the variations in the experimental design and dissimilarity in the reporting of results. Differences in experimental design included, most noticeably, the use of various donor and receptor solutions, different temperatures wherein the receptor compartment was placed, differences in skin thickness and variations in exposed skin surface areas. The metals considered in the review, namely chromium, cobalt, gold, lead, mercury, nickel, platinum, rhodium and silver, permeate through intact human skin under physiological conditions. Large variations in the permeability results were observed, with the notable differences in methodology as the probable reason. Results obtained from the in vitro experiments indicate that platinum and rhodium permeated through intact Caucasian skin with flux values of 0.12 and 0.05 ng/cm2/h, respectively. The cumulative mass of platinum (2.57 ng/cm2) that permeated after 24 hours of exposure was statistically significantly (p = 0.016) higher than rhodium permeation (1.11 ng/cm2). The mass of platinum (1 459.47 ng/cm2) retained in the skin after 24 hours of exposure was statistically significantly (p < 0.001) higher than rhodium retention (757.04 ng/cm2). The comparison of permeability between two different racial groups indicates that platinum permeated through the skin of both racial groups with the flux through African skin found as 1.93 ng/cm2/h and 0.27 ng/cm2/h through Caucasian skin. The cumulative mass of platinum permeated after 24 hours of exposure was statistically significantly (p = 0.044) higher through African skin (37.52 ng/cm2) than Caucasian skin (5.05 ng/cm2). The retention of platinum in African skin (3 064.13 ng/cm2) was more than twice the mass retained in Caucasian skin (1 486.32 ng/cm2). Conclusions: The in vitro diffusion method is an applicable method to determine skin permeability of metals. However, the experimental design and format of data reporting should be standardised to enable comparison of results from different studies. Platinum and rhodium permeated through intact human skin, with platinum permeation significantly higher. African skin was significantly more permeable by platinum than Caucasian skin. Both platinum and rhodium were retained inside the skin after 24 hours of exposure, possibly forming a reservoir which could contribute to continued permeation through the skin even after removal thereof from the skin. Platinum and rhodium permeated through full thickness skin and thereby could possibly contribute to local skin symptoms such as dermatitis and urticaria found in occupationally exposed workers. By permeating through the upper layers of the skin, these metals could potentially reach the viable epidermis and contribute to sensitisation. / PhD (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015

Le platine (Pt), le palladium (Pd) et le rhodium (Rh), font partie des Eléments du Groupe du Platine (EGP), utilisés dans les catalyseurs automobiles. En raison de leur émission dans l'environnement, ces éléments peuvent aujourd'hui être considérés comme des contaminants émergeants et traceurs de la contamination automobile. Cette étude porte sur la dispersion des EGP depuis leur source (monolithes et émission à l'échappement) jusqu'au champ proche (atmosphère, poussières de chaussées, eaux de ruissellement, sédiment,sol de bord de route). Leur mobilité à partir de monolithes a été étudiée en présence d'eau de ruissellement et de molécules organiques. Leur spéciation a été évaluée dans les poussières de chaussées et les sédiments. Les teneurs en EGP dans les monolithes étudiés montrent le remplacement de Pt par Pd dans les catalyseurs récents. L'abondance relative des EGP dans les échantillons environnementaux est Pd > Pt > Rh. Les expérimentations de mobilisation montrent que la mobilisation des EGP est plus significative au contact des molécules organiques, est dépendante du pH de la solution et augmente avec l'âge du monolithe. Rh est l'élément le plus mobilisable dans les monolithes. La spéciation montre que les EGP sont peu mobiles. Dans la part mobilisable, ils sont majoritairement liés à la fraction dite organique. / Platinum (Pt), palladium (Pd) and rhodium (Rh) (platinum-group elements; PGEs),are used in automotive catalytic converters to remove harmful emissions from exhaust gas. Nevertheless, nowadays, the PGEs are emerging as new environmental emission contaminators due to their increasing use. The goal of this research is to study the distribution of PGEs from the source (i.e. automotive catalytic converters and exhaust gas) to the environmental samples (i.e. atmospheric particles, road dust,storm water, pond sediments, and road-side soil). The mobility of PGEs from the converters in contact with run off water and natural complexing agents were studied. Also, the speciation of PGEs was investigated in road dust and pond sediments. Comparison of PGE contents in different catalysts confirms the replacement of Pt by Pd in more recent converters. Besides, the relative abundance of PGEs in environmental samples shows higher concentration of Pd compared toPt and Rh (i.e. Pd>Pt>Rh). The results of testing PGEs mobilization in catalytic converters demonstrate more significant mobilization by organic molecules as compared to run off water. Our results also show the dependency of PGEs mobilization on pH and on catalyst age. Among the PGEs, Rh was the most mobilized element in catalytic converters. More importantly, the speciation test shows that while PGEs are low mobile elements, in the mobilizable fraction, PGEs are in the organic fraction.

The two stage Lucite Alpha Process for the industrial manufacturing of methyl methacrylate (MMA) represents one of the most efficient technologies currently available for the large scale production of this important chemical commodity. The second stage of this process, which involves the condensation of methyl propanoate (MeP) with formaldehyde over a heterogeneous fixed bed catalyst, however, still shows great scope for improvement. Herein the development of a novel homogeneous catalytic system that would promote the condensation of either propanoic acid or MeP with formaldehyde is explored. Since C–C bond forming reactions which proceed via C–H activation pathways typically display high atom efficiency, our efforts were particularly focussed on employing a functionalisation strategy that is mediated by C–H activation. In the case of propanoic acid, the possibility of achieving regioselective α-methylenation by linking the substrate to phosphorus was evaluated. Thus, a series of acyloxyphosphines and acylphosphites derived from either propionic acid or phenylacetic acid was prepared and, where stability allowed, fully characterised. Some of the resultant simple mixed anhydrides posed problems relating to their stability, and the stabilisation of such ligand systems by using electronic and / or steric effects was therefore explored. In addition, the coordination chemistry and in solution behaviour of Rh(I) and Ru(II) complexes containing these ligands was examined. Similar to the free ligands, complexes derived from these mixed anhydrides rearranged in solution via a number of decomposition pathways, with the specific pathway dependent on the nature of the auxiliary ligands. For most of these complexes, however, ligand decarbonylation was the route of preference for decomposition. Despite the instability of these complexes, a selection of Rh(I) mixed anhydride complexes were assessed for their potential as C-H activation catalysts in reactions aimed at the α-methylenation of saturated carboxylic acids. Furthermore, the stabilisation of Rh(I) mixed anhydride complexes with chelating auxilary ligands, such as bisphosphines or N-substituted diphosphinoamines, was explored. In particular, a series of new Rh(I) mixed anhydride complexes containing dppe, dppb and dppbz as secondary ligands were prepared and the effects of these secondary ligands on the in solution stability of these complexes assessed. As MeP represents the final product in the first stage of the Alpha process and not propanoic acid, the utilisation of PNP iridium pincer complexes in the regioselective sp³ C–H activation of MeP and related esters was also examined. The factors that govern the regioselectivity of such reactions were of great interest to us and, in particular, the effects of water on the reactivity and regioselectivity of these reactions were explored. For MeP, preferential C–H activation of the methoxy group was found to proceed under anhydrous conditions and the catalytic functionalisation of this site with ethene using this activation approach was considered. Formaldehyde, employed in the second stage of the Alpha process, is a difficult substance to manufacture and handle, especially on a large scale. A preliminary study on the in situ production of anhydrous formaldehyde via the catalytic dehydrogenation of methanol was therefore performed. During this study, catalytic systems based on carbonate salts and / or transition metal complexes were considered. In the hope of reducing the number of steps required in the production of MMA, a new one-pot cascade reaction for the indirect α-methylenation of MeP with methanol was developed. Although the production of MMA using this system only proceeded with low efficiency, the obtained results serve as an important proof of concept for future developments in this area. Finally, the capacity of a series of simple bases to catalyse the condensation of MeP with formaldehyde was assessed as part of a fundamental study directed towards determining the factors that govern the efficiency of this reaction. In addition, the extent to which each base effects the deprotonation in the α-position of MeP was determined with the aid of deuterium labelling experiments. Similarly, using sodium propanoate as model base a rough estimate of the kinetics of deprotonation could be made based on the degree of deuterium incorporation over time. These studies suggested that the low efficiency of this condensation reaction is not caused by ineffective deprotonation but rather by the weak nucleophilicity of the generated carbanion. For this reason, attempts to increase the electrophilicity of formaldehyde through Mannich-type condensations reactions involving secondary amine and carboxylic acid additives were made.