Philosophiae Doctor - PhD / South Africa is undergoing a serious consideration of hydrogen economy in an effort to develop safe clean and reliable alternative energy sources for fossil fuels. Ammonia is one of the promising candidates due to its low production cost, ease in liquefaction at ambient temperatures, and high energy density as compared to methanol. Ammonia has a high content of hydrogen atoms per unit volume and can easily be cracked down into hydrogen and nitrogen. In the last four years carbon intensive coal dependent South Africa has become one of the leading global destinations for renewable energy investment. Another driving force behind the technology is the prevalence of platinum reserves found in South Africa. Platinum group metals are the key catalytic materials used in most fuel cells, and with more than 75 % of the world’s known platinum reserves found within South Africa. In this thesis, I have developed novel electrocatalysts that are highly specific and selective for production of hydrogen using ammonia as a fuel source. The electro-oxidation of ammonia on platinum electrode drop coated platinum nanoparticles (PtNP), platinum iridium nanoparticles (PtIrNP), platinum ruthenium nanoparticles (PtRuNP), platinum telluride nanoparticles (PtTeNP) and ternary nanoparticles (PtIrTeNP) finally (PtRuTeNP) was systematically studied in alkaline solution of potassium hydroxide (KOH) by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrocatalysts were synthesised using sodium borohydride as a reducing agent and polyvinylpyrrolidone (PVP) as a stabilising agent from aqueous solutions of H2PtCl6/IrCl3/RuCl3/NaHTe mixtures. XRD confirmed that the binary and ternary electro-catalyst displayed characteristic patterns which indicated that all catalysts have shown the Pt face-centred-cubic (fcc) crystal structure and that the nanoparticles were poly-orientated. The structural characterization was further confirmed with FTIR and UV-vis, FTIR showed the most striking evidence that the PVP stabilized Pt presented a broad peak between 1288 cm-1 and 1638 cm‐1 which corresponded to C‐N stretching motion and C=O stretching motion of monomer for PVP, respectively. The narrow absorption peak centered at 1420 cm‐1 and 2880 cm‐1 occurred in which was ascribed to the C–H bonding due to the presence of PVP. This was due to the formation of coordinate bond between the nitrogen atom of the PVP and the Pt2+, Ir3+, Ru3+ and Te2+ ions. UV-vis was able to show the oxidation state of the nanoparticles and obtained an exponential graph shape which indicated complete reduction because there was no peak observed. Morphological characterization in the form of high resolution scanning electron microscope (HRSEM) revealed the formation of poly-orientated nanoparticles with average particle size of 23- 46 nm with slightly aggregated crystalline materials. The elemental composition of the alloy nanoparticles measured using energy dispersive spectroscopy (EDS) showed the presence of the four elements; Pt, Ir, Ru and Te. High resolution transmission electron microscopy (HRTEM) revealed the formation of crystalline non-aggregated 0.6-5 nm sized nanoparticles. The elemental composition of the alloy nanoparticles measured using energy dispersive X-ray (EDX) showed the presence of the four elements; Pt, Ir, Ru and Te. Selected area electron diffraction pattern (SAED) nanoparticles showed characteristic electron diffraction rings of Pt, PtIr, PtRu, PtTe, PtIrTe and PtRuTe, confirmed the phase and crystallinity of the materials. The electrocatalytic behaviour of the PtIrTe and PtRuTe nanoparticles for ammonia oxidation in KOH solution showed reduced overpotential properties and an increased current density compared to the bare Pt nanoparticles electrode thus providing a promising alternative for development of low-cost and high-performance electrocatalyst for electro-oxidation of ammonia. In terms of minimising the ammonia oxidation overpotential, catalyst selection were ranked as follows PtTe > PtRuTe > PtIr > PtRu > PtIrTe > Pt, with regards to maximising the exchange current density, the ranking was PtTe > PtIrTe > Pt > PtRu > PtIr > PtRuTe. The results were further interrogated with EIS which revealed in terms of minimising charge transfer resistance (Rct) the nano catalysts selection were ranked as follows PtRuTe ˃ PtIrTe ˃ PtRu ˃ PtIr ˃ Pt ˃ Bare Pt electrode ˃ PtTe. That meant that the conductivity of the catalysts facilitated the flow of charge through the nanoalloys onto the surface of the electrode. The difference in charge transfer resistance revealed that PtRuTe and PtIrTe nanoalloys had an obvious advantage in reaction activity. The application of ternary metal nanoparticles had significantly enhanced the catalytic activity toward ammonia oxidation. The role of the third component (Te) had improved the catalysts in reducing Nads adsorption on Pt. The enhanced catalytic activity has been attributed by a number of factors including the change in Pt–Pt inter atomic distance, number of Pt nearest neighbours, Pt 5d band vacancy, and Pt metal content on particle surface.

Porous materials have exhibited some remarkable performances in wide range of applications such as in the field of catalysis, gas adsorption, water treatment, bio- imaging, drugs delivery and energy applications. This is due to the pore characteristic of these materials. In fact, their properties depend mainly on the pore size, pore morphology and pore size distribution. The knowledge of understanding the effect of chemical nature of porous materials on the heterogeneous catalysis has significantly increased since last decades resulting in the increase in the development of innovative porous nano-hybrid materials. Scientists have integrated inorganic and organic materials to generate new structures with unique properties. A significant enhancement in their properties have been observed compared to their single components. This research work focuses on the design and tailoring of innovative hybrid materials with intrinsic porosity based on well studied single components for catalysis and energy applications. The first example is represented by the impregnation technique of gold nanoclusters (Au NCs) inside the pores of mesoporous silica nanoparticles (MSNs). The performance of Au NCs/ MSN as catalyst was evaluated by the epoxidation reaction of styrene. It shows a remarkable catalytic activity, high selectivity towards styrene epoxide (74%) and high conversion of styrene (88%). We have also investigated the self-assembly of polyoxomolybdates (P2Mo5O23) and cyclodextrins (CDs) as molecular building blocks (MBBs) through the bridging effect of counter cations (Na+, K+, and Cs+). This assembly has resulted in the formation of seven different crystals to give seven crystal structures of POM-CD MOFs. These novel porous hybrid frameworks with intrinsic porosity and tunable porosity have been well studied and characterized using different techniques. Interestingly, one of these structures (K-PMo-γ-CD) was obtained in good yield (70 % based on γ-CD), and was therefore selected to further study the catalytic performance of this type of the hybrid organic-inorganic structures (POM-CD MOFs). The ketalization process of cyclohexanone with glycol using K-PMo-γ-CD as catalysts, have been chosed as module reaction for this study. Our results showed that the material give the best catalytic performance, which reached its maximum conversion of 99.94 %, at 100oC. Finally, the scope of our research have been extended by combining another porous macrocycle, a trianglamine (TA), with the metal cluster complex system (polyoxometalate). This hybrid framework (POM-TA) have been well designed and synthesized based on molecular recognition. A detailed characterization shows that the POM-TA material has high surface area that suggests that it can be suitable as catalyst for some industrial processes. Our research on such organic-inorganic hybrid frameworks represents a promising enrichment in the field of heterogeneous catalysis. This is largely due to the possibility of combining different molecular building blocks to form a hybrid framework with improved properties such as intrinsic porosity, large surface area, and tunable structural properties.

No description available.

No description available.

Water treatment facilities commonly reduce soluble contaminants, such as soluble manganese (Mn2+), in water by oxidation and subsequent filtration. Previous studies have shown that conventional porous filter system removes Mn2+ from drinking water by developing Mn-oxides (MnOx(s)) bearing coating layers on the surface of filter media. Multiple models have been developed to explain this Mn2+ removal process and the formation mechanism of MnOx(s) coatings. Both, experimental and theoretical studies to date have been largely focused on the micrometer to millimeter scale range; whereas, coating layers are composed of nanoscale particles and films. Hence, understanding the nanoscale particle and film formation mechanisms is essential to comprehend the complexity of soluble contaminant removal processes. The primary objective of this study was to understand the initial MnOx(s) coating formation mechanisms and evaluate the influence of filter media characteristics on these processes. We pursued this objective by characterizing at the micro and nanoscale MnOx(s) coatings developed on different filter media by bench-scale column tests with simulating inorganic aqueous chemistry of a typical coagulation fresh water treatment plant, where free chlorine is present across filter bed. Analytical SEM and TEM, powder and synchrotron-based XRD, XPS, and ICPMS were used for characterization of coatings, filter media and water solution elemental chemistry. A secondary objective was to model how surface coating formation occurred and its correlation with experimentally observed physical characteristics. This modeling exercise indicates that surface roughness and morphology of filtering media are the major contributing factors in surface coating formation process. Contrary to previous models that assumed a uniform distribution and growth of surface coating, the experimental results showed that greater amounts of coating were developed in rougher areas. At the very early stage of coating formation, unevenly distributed thin films and/or particle aggregates were observed, which provided active sites for further surface coating growth. The predominant MnOx(s) phase in the surface coatings was identified to be poorly crystalline birnessite having scavenging activity by intercalation and/or sorption. This would explain the enhancement of efficiency in removing soluble manganese and other contaminants during water filtration. Moreover, the increased Mn2+ removal effect of having aluminum (Al) in pre-treated water is explained. These results indicate that the surface roughness and morphology need to be incorporated into particle capture models to more precisely describe the soluble manganese removal process. / Ph. D.

In this dissertation I explore discourse around the environmental risks of nanotechnology, and through this study of nanotechnology make the case that the dominance in risk discourse of regulatory science is limiting policy debate on environmental risks, and that specific initiatives should be undertaken to broaden debate not just on nanotechnology, but generally on the risks of new technologies. I argue that the treatment of environmental risk in public policy debates has failed for industrial chemicals, is failing for nanotechnology, and most certainly will fail for synthetic biology and other new technologies unless we change how we describe the impacts to people and other living things from the development and deployment of technology. However, I also contend that the nanotechnology case provides reason for optimism that risk can be given different, and better, treatment in environmental policy debates. I propose specific policy initiatives to advance a richer discourse around the environmental implications of emerging technologies. Evidence of enriched environmental policy debates would be a decentering of language concerning risk by developing within discourse language and practice directed toward enriching the human and environmental condition. / Ph. D.

O celulossomo é um complexo multienzimático extracelular utilizado por bactérias anaeróbias para a degradação de biomassa vegetal. Ele é composto por escafoldinas, estruturas alongadas que abrigam diversos módulos cohesina, às quais se ligam dockerinas, seus parceiros de interação específica de alta afinidade, fusionados às enzimas celulolíticas. Os módulos cohesina e dockerina compõem o elemento central da interação entre todos os componentes que integram o celulossomo. Esses módulos são divididos em tipos, de acordo com sua sequência primária. Essa divisão reflete efeitos funcionais distintos, sendo o tipo I responsável pela ligação de enzimas às escafoldinas, enquanto o tipo II medeia a ligação de escafoldinas à célula. O celulossomo de Ruminococcus flavefaciens é o mais complexo conhecido, e na classificação por tipos, suas sequências divergem, formando o tipo III, que foi posteriormente subdividido em 6 grupos para significância funcional. Nesse sistema, o principal responsável pela integração de enzimas ao sistema é a escafoldina primária ScaA, a qual interage com escafoldina adaptadora ScaB. A especificidade dessa ligação - dockerina de ScaA (Rf-DocA) com cohesinas de ScaB (Rf-CohB1-7) - é classificada como único membro do grupo 5, na divisão de grupos que compõem o tipo III. Assim, essa interação é de suma importância para a organização do celulossomo desse organismo, tendo sido estudada por meio de experimentos biofísicos e bioquímicos. Porém a falta de uma estrutura cristalina resolvida desses componentes limita a compreensão que podemos ter sobre a interação. 1-2 Nesse trabalho, apresentamos as estruturas cristalográficas de Rf-DocA, em complexo com a Rf-CohB4, além da estrutura dessa cohesina isolada, e ainda, a Rf-CohB1, e alguns de seus mutantes pontuais. Com isso, esclarecemos aspectos estruturais desses módulos, como a presença de dois sítios funcionais de ligação a cálcio em Rf-DocA. Também é observável pelos modelos gerados, detalhes da ligação entre eles, como os resíduos participantes da interação. Estudos de afinidade entre esses módulos foram conduzidos para a elucidar algumas propriedades da ligação entre esses módulos, de forma que descobrimos que ela ocorre de uma única maneira, e que há um loop na cohesina cuja flexibilidade afeta a afinidade da ligação. Isso sugere um mecanismo de alteração conformacional que regula a ligação à dockerina. Adicionalmente, buscamos o emprego desses módulos em uma aplicação tecnológica, desenhando redes automontáveis de proteínas, visando a construção de um nanomaterial. Essas redes são formadas por características intrínsecas das proteínas que os compõem, sendo o principal fator considerado sua simetria rotacional.3 Nesse sentido, as dockerinas e cohesinas foram utilizadas para ligação entre proteínas de diferentes simetrias. Utilizamos proteínas de simetrias C3, C4 e C6 com fusão a dockerinas, que se conectam às cohesinas fusionadas a proteínas de simetria C2, as quais formam o elemento linear da ligação entre os diferentes módulos. Esse desenho experimental permite a expressão e purificação independentes dos componentes, o que facilita a obtenção das redes, a partir da mistura dos dois componentes. Através de análises preliminares por microscopia eletrônica de transmissão, observamos a formação de filmes bidimensionais extensos e nanotubos com a construção testada. / The cellulosome is an intricate multienzyme extracelular complexes evolved by anaerobic bacteria for degradation of cellulosic biomass. It is composed of scaffoldins, elongated structures, which bare numerous cohesin modules, which bind to dockerin modules, their high affinity and specificity partners, borne by cellulolytic enzymes. The cohesin and dockerina modules constitute the central element of the interaction between every component of the cellulosome. These modules are categorized in types, according to their primary sequence. That distribution reflects distinct functions, in which the type I is responsible for integration of enzymes to scaffoldins, while type II mediates anchoring of scaffoldins to the cell wall. The cellulosome of Ruminococcus flavefaciens is the most intricate known to date, which is categorized into a third type of cohesins and dockerins, due to sequence diversion. The type III was further divided into 6 groups to impart functional significance. In that system, the main enzyme integrating component is the primary scaffoldin ScaA, which interacts to the adaptor scaffoldin ScaB. The specificity of this interaction - dockerina of ScaA (Rf-DocA) to ScaB cohesins (Rf-CohB1-7) - is sorted as a single member of group 5, in the subtypes of type III. Thus, this interaction is essential for cellulosome organization, having been studied by biophysical and biochemical experiments. However, the lack of a solved crystalline structure of these components narrows our understanding on this interaction. In the present study, we present the structures of Rf-DocA, complexed to Rf-CohB4, besides the structure of this isolated cohesin, and also Rf-CohB1 and its point mutants. Due to these data, we clarify structural aspects of these modules, such as the occurrence of two functioning calcium binding sites in Rf-DocA. We also identified details of their binding, such as the interacting residues. Through binding affinity studies, we concluded that the interaction between these modules occurs in a single mode, and that there is a loop in the cohesin module whose flexibility has direct effects on the binding affinity to dockerin. Additionally, we sought to utilize these modules in a downstream application, by designing self-assembling arrays of proteins, aiming for the construction of a nanomaterial. These arrays are constructed from the intrinsic properties of its constituent proteins, in which the main factor is rotational symmetry. In this context, dockerina and cohesin modules were used of binding different symmetry proteins. We utilized C3, C4 and C6 point symmetry proteins fused to dockerin modules, which bind to the cohesin modules fused to C2 point symmetry proteins, which establish the linear connection between the distinct components. This experimental design allows for the independent expression and purification of the components, which facilitates the achievement of the arrays, by simple mixture of the two components. Through preliminary analysis by transmission election microscopy, we observed the construction of two-dimensional films and nanotubes.

O celulossomo é um complexo multienzimático extracelular utilizado por bactérias anaeróbias para a degradação de biomassa vegetal. Ele é composto por escafoldinas, estruturas alongadas que abrigam diversos módulos cohesina, às quais se ligam dockerinas, seus parceiros de interação específica de alta afinidade, fusionados às enzimas celulolíticas. Os módulos cohesina e dockerina compõem o elemento central da interação entre todos os componentes que integram o celulossomo. Esses módulos são divididos em tipos, de acordo com sua sequência primária. Essa divisão reflete efeitos funcionais distintos, sendo o tipo I responsável pela ligação de enzimas às escafoldinas, enquanto o tipo II medeia a ligação de escafoldinas à célula. O celulossomo de Ruminococcus flavefaciens é o mais complexo conhecido, e na classificação por tipos, suas sequências divergem, formando o tipo III, que foi posteriormente subdividido em 6 grupos para significância funcional. Nesse sistema, o principal responsável pela integração de enzimas ao sistema é a escafoldina primária ScaA, a qual interage com escafoldina adaptadora ScaB. A especificidade dessa ligação - dockerina de ScaA (Rf-DocA) com cohesinas de ScaB (Rf-CohB1-7) - é classificada como único membro do grupo 5, na divisão de grupos que compõem o tipo III. Assim, essa interação é de suma importância para a organização do celulossomo desse organismo, tendo sido estudada por meio de experimentos biofísicos e bioquímicos. Porém a falta de uma estrutura cristalina resolvida desses componentes limita a compreensão que podemos ter sobre a interação. 1-2 Nesse trabalho, apresentamos as estruturas cristalográficas de Rf-DocA, em complexo com a Rf-CohB4, além da estrutura dessa cohesina isolada, e ainda, a Rf-CohB1, e alguns de seus mutantes pontuais. Com isso, esclarecemos aspectos estruturais desses módulos, como a presença de dois sítios funcionais de ligação a cálcio em Rf-DocA. Também é observável pelos modelos gerados, detalhes da ligação entre eles, como os resíduos participantes da interação. Estudos de afinidade entre esses módulos foram conduzidos para a elucidar algumas propriedades da ligação entre esses módulos, de forma que descobrimos que ela ocorre de uma única maneira, e que há um loop na cohesina cuja flexibilidade afeta a afinidade da ligação. Isso sugere um mecanismo de alteração conformacional que regula a ligação à dockerina. Adicionalmente, buscamos o emprego desses módulos em uma aplicação tecnológica, desenhando redes automontáveis de proteínas, visando a construção de um nanomaterial. Essas redes são formadas por características intrínsecas das proteínas que os compõem, sendo o principal fator considerado sua simetria rotacional.3 Nesse sentido, as dockerinas e cohesinas foram utilizadas para ligação entre proteínas de diferentes simetrias. Utilizamos proteínas de simetrias C3, C4 e C6 com fusão a dockerinas, que se conectam às cohesinas fusionadas a proteínas de simetria C2, as quais formam o elemento linear da ligação entre os diferentes módulos. Esse desenho experimental permite a expressão e purificação independentes dos componentes, o que facilita a obtenção das redes, a partir da mistura dos dois componentes. Através de análises preliminares por microscopia eletrônica de transmissão, observamos a formação de filmes bidimensionais extensos e nanotubos com a construção testada. / The cellulosome is an intricate multienzyme extracelular complexes evolved by anaerobic bacteria for degradation of cellulosic biomass. It is composed of scaffoldins, elongated structures, which bare numerous cohesin modules, which bind to dockerin modules, their high affinity and specificity partners, borne by cellulolytic enzymes. The cohesin and dockerina modules constitute the central element of the interaction between every component of the cellulosome. These modules are categorized in types, according to their primary sequence. That distribution reflects distinct functions, in which the type I is responsible for integration of enzymes to scaffoldins, while type II mediates anchoring of scaffoldins to the cell wall. The cellulosome of Ruminococcus flavefaciens is the most intricate known to date, which is categorized into a third type of cohesins and dockerins, due to sequence diversion. The type III was further divided into 6 groups to impart functional significance. In that system, the main enzyme integrating component is the primary scaffoldin ScaA, which interacts to the adaptor scaffoldin ScaB. The specificity of this interaction - dockerina of ScaA (Rf-DocA) to ScaB cohesins (Rf-CohB1-7) - is sorted as a single member of group 5, in the subtypes of type III. Thus, this interaction is essential for cellulosome organization, having been studied by biophysical and biochemical experiments. However, the lack of a solved crystalline structure of these components narrows our understanding on this interaction. In the present study, we present the structures of Rf-DocA, complexed to Rf-CohB4, besides the structure of this isolated cohesin, and also Rf-CohB1 and its point mutants. Due to these data, we clarify structural aspects of these modules, such as the occurrence of two functioning calcium binding sites in Rf-DocA. We also identified details of their binding, such as the interacting residues. Through binding affinity studies, we concluded that the interaction between these modules occurs in a single mode, and that there is a loop in the cohesin module whose flexibility has direct effects on the binding affinity to dockerin. Additionally, we sought to utilize these modules in a downstream application, by designing self-assembling arrays of proteins, aiming for the construction of a nanomaterial. These arrays are constructed from the intrinsic properties of its constituent proteins, in which the main factor is rotational symmetry. In this context, dockerina and cohesin modules were used of binding different symmetry proteins. We utilized C3, C4 and C6 point symmetry proteins fused to dockerin modules, which bind to the cohesin modules fused to C2 point symmetry proteins, which establish the linear connection between the distinct components. This experimental design allows for the independent expression and purification of the components, which facilitates the achievement of the arrays, by simple mixture of the two components. Through preliminary analysis by transmission election microscopy, we observed the construction of two-dimensional films and nanotubes.

Lithium-ion batteries (LIBs) are receiving significant attention from both academia and industry as one of the most promising energy storage and conservation devices due to their high energy density and excellent safety. Graphite, the most widely used anode material, with limitations on energy density, can no longer satisfy the requirements proposed by new applications. Therefore, further improvement on the electrochemical performance of anodes has been long pursued, along with the development of new anode materials. Among potential candidates, Si and Sn based anodes are believed to be the most promising. However, the dramatic volume expansion upon Li-intercalation and contraction upon Li de-intercalation cause mechanical instability, and thus cracking of the electrodes. To overcome this issue, many strategies have been explored. Among them the most efficient strategies include introduction of a nanostructure, coupled with a buffering matrix and coating with a protective film. However, although cycling life has been significantly increased using these three strategies, the capacity retention still needs improvement, especially over extensive charge-discharge cycles. In addition, more efforts are still needed to develop new fabrication methods with low costs and high efficiency. To further improve mechanical stability of electrodes, understanding of the failure mechanisms, particularly, the failure mechanisms of Si and Sn nanomaterials is essential. Therefore, some of the key factors including materials fabrication and microstructural changes during cycling are studied in this work. Hollow Si nanospheres have proved to be have a superior electrochemical performance when applied as anode materials. However, most of fabrication methods either involve use of processing methods with low throughput, or expensive temporary templates, which severely prohibits large-scale use of hollow Si spheres. This work designed a new template-free chemical synthesis method with high throughput and simple procedures to fabricate Si hollow spheres with a nanoporous surface. The characterization results showed good crystallinity and a uniform hollow sphere structure. The substructure of pores on the surface provides pathways for electrolyte diffusion and can alleviate the damage by the volume expansion during lithiation. The success of this synthesis method provides valuable inspiration for developing industrial manufacturing method of hollow Si spheres.3D graphene is the most promising matrix that can provide the necessary mechanical support to Sn and Si nanoparticles during lithiation. 2D graphene, however, results in Sn/graphene nanocomposites with a continuous capacity fade during cycling. It is anticipated that this is due to microstructural changes of Sn, however, no studies have been performed to examine the morphology of such cycled anodes. Hence, a new Sn/2D graphene nanocomposite was fabricated via a simple chemical synthesis, in which Sn nanoparticles (20-200 nm) were attached onto the graphene surface. The content of Sn was 10 wt.% and 20 wt.%. These nanopowders were cycled against pure Li-metal and, as in previous studies, a significant capacity decrease occurred during the first several cycles. Transmission and scanning electron microscopy revealed that during long term cycling electrochemical coarsening took place, which resulted in an increased Sn particle size of over 200 nm, which could form clusters that were 1 m. Such clusters result in a poor electrochemical performance since it is difficult for complete lithiation of the Sn to occur. It is hence concluded that the inability of Sn/2D graphene anodes to retain high capacities is due to coarsening that occurs during cycling. In addition to using forms of carbon to buffer the Sn expansion, it has been proposed to alloy Sn with S, which has a low redox potential vs Li⁰/Li⁺. Therefore, another new anode proposed here is that of SnS attached to graphite. The as prepared powders had a flower-like structure of the SnS alloy. Electrochemical cycling and subsequent microstructural analysis showed that after electrochemical cycling this pattern was destroyed and replaced by Sn and SnS nanoparticles. Based on the electron microscopy and XRD analysis, it was concluded that selective leaching of S occurs during lithiation of SnS particles, which results into nano SnS and Sn particles to be distributed throughout the electrolyte or SEI layer, without being able to take part in the electrochemical reactions. This mechanism has not been noted before for SnS anodes and indicates that it may not be possible to retain the initial morphology of SnS alloy during cycling, or the ability of SnS to be active throughout long term cycling. To conclude it should be stated that the goal and novelty of this thesis was (i) the fabrication of new Si, Sn/graphene and SnS/C nanostructures that can be used as anodes in Li-ion batteries and (ii) the documentation of the mechanisms that disrupt the initial structural stability of Sn/2D graphene and SnS/C anodes and result in severe capacity loss during long term cycling (over 100 cycles). These systems are of high interest to the electrochemistry community and battery developers.

The objectives of this thesis were to optimize the synthesis and surface coating of metallic and semiconductor nanoparticles, to understand how these materials interact with cells and physiological systems and to investigate how they can be used to deliver thermal therapy for medical applications. Reproducible high-yield synthesis of gold nanorods and surface coating with a variety of polymers and silica was optimized. Using gold nanorods as a model system, the relationship between particle surface chemistry, surface charge and cellular uptake was studied, as well as the toxicity of nanoparticles of different surface chemistry. Low toxicity in vitro was encouraging and was confirmed in vivo by intravenously injecting Sprague-Dawley rats with semiconductor quantum dots of various surface coatings. Low toxicity was found during biochemical, haematological and pathological assessment, and these results indicate that applications of nanoparticles should be further investigated. One such application is the use of near infrared absorbing gold nanorods in remotely activated hyperthermia. It was shown that gold nanorods act synergistically with the chemotherapeutic cisplatin to improve cytotoxicity, and reduce the required cytotoxic drug dose to 33% of the unheated amount. Due to the success of hyperthermia treatment in vitro, continuing and future work involves the use of gold nanorods ex vivo on excised human corneas in a novel application to weld corneal tissue for improved wound closure following cataract surgery.