Vaal University of Technology / ii Abstract The use of biosorption to complement conventional water treatment techniques has gained widespread appeal partly due to the abundance of waste materials that can be used as low cost biosorbents. However, some materials have not yet been exploited in this regard. This research was aimed at evaluating the biosorption potential of Mangifera indica (mango) seed shells that are readily available in several farming areas of the Limpopo and Mpumalanga Provinces of South Africa. In this work, powdered ethylenediaminetetraacetic acid (EDTA) functionalized biosorbent was prepared from alkali treated biomass of waste mango seed shells. The influence of alkali treatment and EDTA functionalization on the physicochemical properties of the biomass was characterized using Fourier transform infra-red spectroscopy, X-ray diffraction and thermogravimetric analysis. Results confirmed removal of hemicelluloses, conversion of crystalline to amorphous cellulose and the introduction of carboxyl, ester and tertiary amine groups from EDTA. Furthermore, the powdered biosorbent was immobilized using calcium alginate for adaptation to column sorption. The powdered biosorbents were tested for sorption of lead(II) ions using batch sorption experiment. Through EDTA functionalization, improvement in sorption capacity for lead(II) ions from 59.25 mg.g-1 to 306.33 mg.g-1 was realized. The Langmuir and Pseudo-nth order models most suitably simulated the equilibrium and kinetics of sorption by both functionalized and non-functionalized biomaterials. The calcium alginate immobilized biosorbent was evaluated for non-specific sorption of ionic species of copper, chromium, nickel and iron from electroplating wastewater through discontinuous column sorption experiments. Highest copper, chromium, nickel and iron removal was 12.3%, 14.8%, 4.4% and 13.8% from nonacidified samples at an initial pH of 3.4, and 15.5%, 18.7%, 13.7% and 17.3% from samples acidified to an initial pH of 1.8. Repeated sorption-desorption cycles involving acidified wastewater resulted in successive improvement in metal uptake against declining recovery indicating irreversible binding on –COOH groups formed from –CH2OH groups through a redox reaction involving reduction of chromium(VI) to chromium(III). Keywords: Mangifera indica; biosorption; alkali treatment; carboxyl functionalization; calcium alginate

The aim of this research was to develop, characterize, and analyze carbon nanotubes as biosensors. In particular, pH and lactate molecules were targeted in this study. The reason these analytes were chosen was twofold. Firstly, when hydrogen ions and lactate are excreted in abnormal amounts in human sweat, they may be an indicator of a separate health problem. Thus, there is a clinical need for such biosensor applications. Secondly, pH and lactate detection represent two different types of electrochemical sensing techniques. The carbon nanotubes used in this research were single walled and existed in bundles. They were further functionalized with the carboxyl group to detect pH and the enzyme lactate oxidase (LOX) to detect lactate. All carbon nanotube samples were characterized to compare the materials with the attached biomolecules and without the presence of biomolecules. Fourier Transform Infrared Spectroscopy (FTIR) was used to verify the attachment of both the carboxyl group COOH and LOX to the respective carbon nanotubes samples. Scanning electron microscopy (SEM) was used to analyze the carbon nanotube lactate electrode sample to examine the structure of the electrode. Both pH and lactate biosensors were used in a standard three electrode electrochemical cell where the carbon nanotubes behaved as the working electrode with an Ag/AgCl reference electrode and a platinum wire as the counter electrode. Each sample was separately interrogated by several voltammetry techniques such as linear, cyclic, and square wave. Square wave voltammetry proved to be the best template to use to sense the target analytes. The functionalized CNT-COOH electrode displayed a linear response to pH 1-10, with a negative voltage shift corresponding to an increase in pH. Two types of lactate sensors were fabricated, both of which exhibited an increase in current corresponding to an increase in lactate concentration. The functionalized CNT-LOX on a glassy carbon electrode displayed an amperometric response in the range of 1 mM - 4 lactate. The CNT-LOX on a Si/ITO substrate displayed an amperometric response in the range of 0.01 M - 0.05 M lactate.

Thesis advisor: Shih-Yuan Liu / Described herein are three projects that derive from in-depth studies of the distinct electronic structure of monocyclic 1,2-dihydro-1,2-azaborine (heretofore referred to as simply 1,2-azaborine). In the first chapter, the first comprehensive review of the late-stage functionalization methods available for 1,2-azaborines as well as their bicyclic and polycyclic (BN-PAH) counterparts is presented. In the second chapter, the development of a general method for both C4 and C5 functionalization based on the building block approach is described. The distinct electronic structure of 1,2-azaborine enables the chemical separation and further functionalization of C4 and C5 borylated isomers. In the second part, the C4, C5, and C6 isomers of BN-styrene analogues were prepared using the newly developed azaborine building blocks. The corresponding polymers were synthesized and extensively characterized in order to compare the effects of the BN-bond positioning relative to the polymer chain. In the fourth and final chapter, 1,2-azaborine-containing phosphine ligands featuring a P-B bond are synthesized. A comparative electronic structure analysis is performed between the BN-phosphine ligands and their direct all-carbon counterparts. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

We present a systematic methodology to functionalize magnetic nanoparticles through surface-initiated atom-transfer radical polymerization (ATRP). The magnetite nanoparticles are prepared according to the method proposed by Sun et al. (2004), which leads to a monodisperse population of ~ 6 nm particles stabilized by oleic acid. The functionalization of the nanoparticles has been performed by transforming particles into macro-initiators for the ATRP, and to achieve this two different routes have been explored. The first one is the ligand-exchange method, which consists of replacing some oleic acid molecules adsorbed on the particle surface with molecules that act as an initiator for ATRP. The second method consists in using the addition reaction of bromine to the oleic acid double bond, which turns the oleic acid itself into an initiator for the ATRP. We have then grown polymer brushes of a variety of acrylic polymers on the particles, including polyisopropylacrylamide and polyacrylic acid. The nanoparticles so functionalized are water soluble and show responsive behavior: either temperature responsive behavior when polyisopropylacrylamide is grown from the surface or PH responsive in the case of polyacrylic acid. This methodology has potential applications in the control of clustering of magnetic nanoparticles. / Singapore-MIT Alliance (SMA)

A main driving force behind the recent years’ immense interest in nanoscience and nanotechnology is the possibility of achieving new material properties and functionalities within, e.g., material physics, biomedicine, sensor technology, chemical catalysis, energy storing systems, and so on. New (theoretical) possibilities represent, in turn, a challenging task for chemists and physicists. An important feature of the present nanoscience surge is its strongly interdisciplinary character, which is reflected in the present work. In this thesis, nanocrystals and thin films of magnetic and ferroelectric metal oxides, e.g. RE2O3 (RE = Y, Gd, Dy), GdFeO3, Gd3Fe5O12, Na0.5K0.5NbO3, have been prepared by colloidal and sol-gel methods. The sizes of the nanocrystals were in the range 3-15 nm and different carboxylic acids, e.g. oleic or citric acid, were chemisorbed onto the surface of the nanoparticles. From FT-IR measurements it is concluded that the bonding to the surface takes place via the carboxylate group in a bidentate or bridging fashion, with some preference for the latter coordination mode. The magnetic properties of nanocrystalline Gd2O3 and GdFeO3 were measured, both with respect to magnetic resonance relaxivity and magnetic susceptibility. Both types of materials exhibit promising relaxivity properties, and may have the potential for use as positive contrast enhancing agents in magnetic resonance imaging (MRI). The nanocrystalline samples were also characterised by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and quantum chemical calculations. Thin films of Na0.5K0.5NbO3, GdFeO3 and Gd3Fe5O12 were prepared by sol-gel methods and characterized by x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). Under appropriate synthesis conditions, rather pure phase materials could be obtained with grain sizes ranging from 50 to 300 nm. Magnetic measurements in the temperature range 2-350 K indicated that the magnetization of the perovskite phase GdFeO3 can be described as the sum of two contributing terms. One term (mainly) due to the spontaneous magnetic ordering of the iron containing sublattice, and the other a susceptibility term, attributable to the paramagnetic gadolinium sublattice. The two terms yield the relationship M(T)=M0(T)+χ(T)*H for the magnetization. The garnet phase Gd3Fe5O12 is ferrimagnetic and showed a compensation temperature Tcomp ≈ 295 K.

In the last decades several new nanostructures of carbon have been discovered, including carbon nanotubes (CNTs), and the recently discovered 2-dimensional graphene. These new materials exhibit extraordinary and unique properties—making them extremely interesting both for fundamental science and for future applications. It is, however, of crucial importance to develop new and improved fabrication and processing methods for these carbon nanomaterials. In this thesis the concept of applying solution chemistry and solution-based techniques to fabricate and to deposit graphene and other carbon nanomaterials is explored. An area-selective deposition method was developed for CNT and carbon-coated iron nanoparticles. By utilizing organic functionalization the properties of the nanomaterials were tuned, with the purpose to make them soluble in a liquid solvent and also enable them to selectively adsorb to non-polar surfaces. The first step of the functionalization process was an acid treatment, to introduce defects in the materials. This method was also used to create defects in so-called carbon nanosheets (CNS). The effect of the defect formation on the electric properties of the graphene-like CNS was studied; it was found that the resistance of the CNS could be reduced to 1/50 by acid treating of the sample. Also, the effect of the created defects on gas adsorption to the surface of the CNS has been investigated. This was done using atomic layer deposition (ALD) of TiO2 on the CNS, and a clear change in nucleation be-havior was seen due to the acid-treatment. Furthermore, a solution-based new method for fabrication of graphene was developed; this method combines intercalation of bromine into graphite with ultrasonic treatment to exfoliate flakes into a solvent. From the solvent the flakes can be deposited onto an arbitrary substrate. Several important parameters in the method were investigated in order to optimize the process. One important parameter proved to be the choice of solvent in all steps of the procedure; it was shown to influence sonication yield, flake size, and deposition results. Toluene was identified as a suitable solvent. A mild heat-treatment of the starting material was also identified as a way to increase the exfoliation yield. Using this method, fabrication of few-layer graphene sheets was achieved and areas down to 3 layers in thickness were identified—this is in the very forefront of current solution-based graphene fabrication techniques.

The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.

The development of a novel palladium-catalyzed domino reaction with indole-based gem-dibromoolefin substrates is described. The reaction allowed access to a new class of polycyclic nitrogen heterocycles: N-fused benzo[c]carbazoles. A key feature of this domino reaction was the participation of both bromides in C–H functionalization processes, a hitherto unprecedented reactivity. Various substituents and substitution patterns were tolerated in this reaction, allowing for a highly modular approach to these challenging synthetic targets. Mechanistic studies were performed to gain further insight into the reactivity of these systems and elucidate the sequence of reaction steps. The results indicate that isomerization of reaction intermediates likely played a key role in promoting a successful reaction.

The development of a novel palladium-catalyzed domino reaction with indole-based gem-dibromoolefin substrates is described. The reaction allowed access to a new class of polycyclic nitrogen heterocycles: N-fused benzo[c]carbazoles. A key feature of this domino reaction was the participation of both bromides in C–H functionalization processes, a hitherto unprecedented reactivity. Various substituents and substitution patterns were tolerated in this reaction, allowing for a highly modular approach to these challenging synthetic targets. Mechanistic studies were performed to gain further insight into the reactivity of these systems and elucidate the sequence of reaction steps. The results indicate that isomerization of reaction intermediates likely played a key role in promoting a successful reaction.

The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.