The aim of this thesis is to investigate different functionalization strategy of graphene nanomaterials for graphene-based different biotechnological applications such as graphene-directed stem cell growth and differentiation and graphene-based biosensors. Chemical functionalization of graphene is required in many biological applications; in this thesis we have focused on exploiting the carboxylic groups available on GO molecules and non-covalent functionalization of graphene. GO has been a promising material for stem cell culture due to high specific surface area, ease of functionalization, its ability to support cell proliferation and to not cause cytotoxicity when stem cells are cultured on its substrate. The impact of biochemical functionalization on stem cell differentiation was not widely researched, and many research groups worldwide have been focusing on GO and rGO surfaces only. The approach of this thesis is to fabricate and characterize different graphene-based substrates to investigate the impact of biochemical functionalization of GO in directing adipose stem cell differentiation and to influence the gene expression pathways of Schwann-like differentiated adipose stem cells. The fabrication of graphene based biosensors is still challenging as biological molecules need to be attached to graphene-based sensors to increase both the specificity and the selectivity of the biosensors. In this thesis, two different chemical functionalization approaches were considered. Firstly, the covalent immobilization of membrane proteins embedded on a lipid nanodisc structure on GO was achieved. Secondly, the feasibility of using dip-pen nanolithography as a tool to locally functionalize graphene arrays with phospholipids was demonstrated. Phospholipid interface layer can act as bioactive layer which can be used for the protein insertion of tail-anchoring recombinant proteins as a new route for a non-covalent biological functionalization of graphene array.

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.

The development of new, improved methods for forming carbon–carbon and carbon–heteroatom bonds is the basic goal in synthetic organic chemistry. In the Lautens group, many recent advances have been made using late transition metals such as rhodium and palladium. One such research project involves the synthesis of indoles through tandem C–N and C–C coupling reactions using gem-dibromoolefin starting materials, and this area serves as a starting point for the research described. Chapter 1 describes a method by which the tandem use of gem-dibromoolefins can be halted to give intramolecular monocoupling reactions, maintaining one of the carbon–bromine bonds which can serve as a useful handle for further functionalization. The use of copper as a catalyst is key to this reaction, as it features a unique mechanism for carbon–heteroatom bond formation. Benzofurans and benzothiophenes can be prepared by this method. Chapter 2 describes the synthesis of 2-bromoindoles using an intramolecular Buchwald–Hartwig amination of gem-dibromoolefins. It is found that the products are more reactive towards palladium(0) than the starting material, and the use of a bulky phosphine ligand which facilitates reversible oxidative addition is required. This represents one of the first catalytic applications of this step in synthesis. Chapter 3 further explores the concept of reversible oxidative addition in a novel carbohalogenation reaction of alkenes. Aryl iodides tethered to alkenes are treated with a palladium(0) catalysts, which can undergo the basic steps of oxidative addition, carbopalladation, and novel sp2 carbon–iodine reductive elimination. This process is remarkably simple in concept, and is a waste-free, atom economically method for preparing new carbon–carbon bonds. Chapter 4 discusses various limitations to the carbohalogenation methodology, and seeks to overcome these problems. The use of aryl bromide starting materials can be accomplished by adding an iodide source to the reaction, allowing halide exchange of palladium(II) intermediates to occur. Intermolecular and asymmetric variants are also explored. Computational studies are discussed which reveal useful mechanistic details of the catalytic cycle, and this information is used in the development of novel phosphine ligands.

The dissociative adsorption of three carboxylic acids (acetic acid, propanoic acid, and acrylic acid), allyl alcohol, and allyl aldehyde on Si(100)2×1 at room temperature has been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD), as well as density-functional theory (DFT) calculations. The C 1s features obtained by XPS measurement for acetic acid, propanoic acid, and acrylic acid show that formation of bidentate carboxylate at a low exposure is followed by that of unidentate carboxylate at a higher exposure, with approximately equal population for both adstructures. The signatures of C 1s features attributed to methyl (285.7 eV), ethyl (285.3 eV), ethenyl (285.0 eV), and bidentate carboxyl (286.8 eV) and unidentate carboxyl (289.8-289.3 eV) carbons were observed for the studied carboxylic acids. The results showed that the carboxyl group is more reactive than the alkyl or alkenyl group towards the Si(100)2×1 surface, with O−H dissociation preferred over [2+2] C=C cycloaddition and the other plausible reaction products. This was also supported by our DFT calculation which showed that the bidentate carboxylate adstructure is the most stable configuration among the calculated adstructures for the aforementioned carboxylic acids. The combined temperature-dependent XPS and TPD studies provided strong evidence for the formation of ketene, acetaldehyde and CO from acetic acid, CO and ethylene from propanoic acid, and CO, ethylene, acetylene, and propene from acrylic acid. Furthermore, the TPD results provided further evidence for the preferred structure of the adsorbate from each of the carboxylic acid on the surface. In addition to carboxyl group, reactivity of the hydroxyl and carbonyl functional groups relative to that of ethenyl group was studied by investigating the reaction of allyl alcohol and allyl aldehyde on Si(100)2×1 at room temperature. The C 1s XPS results supported O−H dissociation for allyl alcohol and [2+2] C=O cycloaddition for allyl aldehyde over the [2+2] C=C cycloaddition. The similarity between the observed C 1s features for allyl alcohol and allyl aldehyde helped to identify the structure of the adsorption products of these two molecules on the surface. The presence of the related C 1s feature of C=C for allyl alcohol and allyl aldehyde, and the absence of C 1s feature of C=O for allyl aldehyde provided strong evidence to support that [2+2] C=C cycloaddition does not occur in the presence of hydroxyl or carbonyl groups. Furthermore, by comparing the experimental results and the adsorption energies of the adstructures calculated by DFT, it was concluded that these molecules do not react with the Si dimers through both of their functional groups, while the reaction of only one of the two functional groups is preferred on the surface. Formation of ethylene, acetylene, and propene from allyl alcohol and allyl aldehyde, simultaneously to CO from allyl alcohol, was concluded from the corresponding TPD results, which also confirm the structure of the adsorbates on the surface. The present research shows that reactions involving oxygen-containing functional groups are favoured over the other plausible reactions including [2+2] C=C cycloaddition on the Si(100)2×1. The preference of the surface to react with one of the two functional groups calls for future studies for the selective functionalization of Si(100)2×1 with potential applications in molecular electronics.

Graphene-based materials have generated tremendous interest in the past decade. Manipulating their characteristics using wet-chemistry methods holds distinctive value, as it provides a means towards scaling up, while not being limited by yield. The majority of this thesis focuses on the surface functionalization of graphene oxide (GO), which has drawn tremendous attention as a tunable precursor due to its readily chemically manipulable surface and richly functionalized basal plane. Firstly, a room-temperature based method is presented to reduce GO stepwise, with each organic moiety being removed sequentially. Characterization confirms the carbonyl group to be reduced first, while the tertiary alcohol is reduced last, as the optical gap decrease from 3.5 eV down to 1 eV. This provides greater control over GO, which is an inhomogeneous system, and is the first study to elucidate the order of removal of each functional group. In addition to organically manipulating GO, this thesis also reports a chemical methodology to inorganically functionalize GO and tune its wetting characteristics. A chemical method to covalently attach fluorine atoms in the form of tertiary alkyl fluorides is reported, and confirmed by MAS 13C NMR, as two forms of fluorinated graphene oxide (FGO) with varying C/F and C/O ratios are synthesized. Introducing C-F bonds decreases the overall surface free energy, which drastically reduces GO’s wetting behavior, especially in its highly fluorinated form. Ease of solution processing leads to development of sprayable inks that are deposited on a range of porous and non-porous surfaces to impart amphiphobicity. This is the first report that tunes the wetting characteristics of GO. Lastly as a part of a collaboration with ConocoPhillips, another class of carbon nanomaterials - carbon nanotubes (CNTs), have been inorganically functionalized to repel 30 wt% MEA, a critical solvent in CO2 recovery. In addition to improving the solution processability of CNTs, composite, homogeneous solutions are created with polysulfones and polyimides to fabricate CNT-polymer nanocomposites that display contact angles greater than 150o with 30 wt% MEA. This yields materials that are inherently supersolvophobic, instead of simply surface treating polymeric films, while the low density of fluorinated CNTs makes them a better alternative to superhydrophobic polymer materials.

The dissociative adsorption of three carboxylic acids (acetic acid, propanoic acid, and acrylic acid), allyl alcohol, and allyl aldehyde on Si(100)2×1 at room temperature has been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD), as well as density-functional theory (DFT) calculations. The C 1s features obtained by XPS measurement for acetic acid, propanoic acid, and acrylic acid show that formation of bidentate carboxylate at a low exposure is followed by that of unidentate carboxylate at a higher exposure, with approximately equal population for both adstructures. The signatures of C 1s features attributed to methyl (285.7 eV), ethyl (285.3 eV), ethenyl (285.0 eV), and bidentate carboxyl (286.8 eV) and unidentate carboxyl (289.8-289.3 eV) carbons were observed for the studied carboxylic acids. The results showed that the carboxyl group is more reactive than the alkyl or alkenyl group towards the Si(100)2×1 surface, with O−H dissociation preferred over [2+2] C=C cycloaddition and the other plausible reaction products. This was also supported by our DFT calculation which showed that the bidentate carboxylate adstructure is the most stable configuration among the calculated adstructures for the aforementioned carboxylic acids. The combined temperature-dependent XPS and TPD studies provided strong evidence for the formation of ketene, acetaldehyde and CO from acetic acid, CO and ethylene from propanoic acid, and CO, ethylene, acetylene, and propene from acrylic acid. Furthermore, the TPD results provided further evidence for the preferred structure of the adsorbate from each of the carboxylic acid on the surface. In addition to carboxyl group, reactivity of the hydroxyl and carbonyl functional groups relative to that of ethenyl group was studied by investigating the reaction of allyl alcohol and allyl aldehyde on Si(100)2×1 at room temperature. The C 1s XPS results supported O−H dissociation for allyl alcohol and [2+2] C=O cycloaddition for allyl aldehyde over the [2+2] C=C cycloaddition. The similarity between the observed C 1s features for allyl alcohol and allyl aldehyde helped to identify the structure of the adsorption products of these two molecules on the surface. The presence of the related C 1s feature of C=C for allyl alcohol and allyl aldehyde, and the absence of C 1s feature of C=O for allyl aldehyde provided strong evidence to support that [2+2] C=C cycloaddition does not occur in the presence of hydroxyl or carbonyl groups. Furthermore, by comparing the experimental results and the adsorption energies of the adstructures calculated by DFT, it was concluded that these molecules do not react with the Si dimers through both of their functional groups, while the reaction of only one of the two functional groups is preferred on the surface. Formation of ethylene, acetylene, and propene from allyl alcohol and allyl aldehyde, simultaneously to CO from allyl alcohol, was concluded from the corresponding TPD results, which also confirm the structure of the adsorbates on the surface. The present research shows that reactions involving oxygen-containing functional groups are favoured over the other plausible reactions including [2+2] C=C cycloaddition on the Si(100)2×1. The preference of the surface to react with one of the two functional groups calls for future studies for the selective functionalization of Si(100)2×1 with potential applications in molecular electronics.

No description available.

The C-H amination and olefin aziridination chemistry of iron supported by dipyrromethene ligands (RLAr, L=1,9-R2-5-aryldipyrromethene, R = Mes, 2,4,6-Ph3C6H2, tBu, Ad, 10-camphoryl, Ar = Mes, 2,4,6-Cl3C6H2) was explored. The weak-field, pyrrole-based dipyrrinato ligand was designed to generate an electrophilic, high-spin metal center capable of accessing high valent reactive intermediates in the presence of organic azides. Isolation of the reactive intermediate in combination with a series of mechanistic experiments suggest the N-group transfer chemistry proceeds through a rapid, single-electron pathway and maintains an overall S=2 electronic configuration throughout the catalytic cycle. We have established the catalysts' strong preference for allylic amination over aziridination with olefin containing substrates. Aziridination is limited to styrenyl substrates without allylic C-H bonds, while allylic amination has been demonstrated with both cyclic and linear aliphatic alkenes. Notably, the functionalization of &alpha-olefins to linear allylic amines occurs with outstanding regioselectivity. / Chemistry and Chemical Biology

Integrated photoelectrochemical water splitting with sunlight is one possible solution to growing global energy needs. Integration of catalysts, photoabsorbers and a membrane require low barriers to charge dissipation if a free standing device structure is to be achieved. The n-type/PEDOT:PSS junction has be identified as the major resistive component and constitutes a large barrier to charge dissipation. In this thesis, the modification of the interface between n-type Si/PEDOT:PSS was achieved by growing a highly – doped region at the contact between the wire and the membrane to reduce voltage loss at the junction from 300 mV to 130 mV. In addition, modification of the surface using a thiophene moiety is observed to decrease the voltage loss from 300 mV to 30 mV. Formation of an insulating silicon oxide on the methyl functionalized surface of the microwires identified a need for characterization of planar silicon samples representative of the sides of the microwires. Si (110), (211) and (111) crystal faces were functionalized with a methyl group and showed different resistance to oxidation. The Si (111) surface was the most resistant while the Si (211) surface was observed to be the least resistant to ambient oxidation.

Purification, chemistry and application are three very important aspects of current research on carbon nanotubes (CNTs). In the dissertation, the purification of nitric acid treated single-walled carbon nanotubes (SWNTs), the dissolution and dichlorocarbene addition of SWNTs, and the effects of chemically functionalized CNTs on neuronal growth are discussed.The nitric acid treated SWNTs were purified by chemical treatment, cross-flow filtration, and centrifugation methods. The effects of nitric acid treatment on the SWNTs and the efficiency of different purification methods was evaluated by the measurement of purify of SWNTs via solution phase NIR. Nitric acid reflux followed with controlled pH centrifugation can produce SWNTs with high purity. This purification mechanism was explained by the relationship of the concentration of the acidic sites on SWNTs and the zeta potential of SWNTs.The dissolution of SWNTs was achieved via chemical functionalization of SWNTs with octadecylamine (ODA). Dichlorocarbene addition to the sidewall of both ODA functionalized and as-prepared SWNTs was investigated. ODA functionalized HiPco-SWNTs were found to have the highest functionality of dichlorocarbene. Vis-NIR spectra of the dichlorocarbene functionalized SWNTs showed a significant decrease in the interband transitions of the semiconducting SWNTs, which indicated that the chemical functionalization of the sidewall of SWNTs changes the electronic properties of SWNTs. Far-IR spectra of the dichlorocarbene functionalized SWNTs showed a dramatic decrease in the electronic transitions at the Fermi level of metallic SWNTs, which was opposite to the effect of ionic doping by bromine. This difference in the far-IR spectroscopy can be used to distinguish covalent chemical functionalization and ionic doping effects of SWNTs.Chemically functionalized multi-walled carbon nanotubes (MWNTs) were applied as substrates for neuronal growth. By manipulating the charge carried by functionalized MWNTs we are able to control the outgrowth and branching pattern of neuronal processes. Chemically functionalized water soluble SWNTs graft copolymers were used in the modulation of outgrowth of neuronal processes. The graft copolymers were prepared by the functionalization of SWNTs with poly-m-aminobenzene sulphonic acid and poly-ethylene glycol. These functionalized water soluble SWNTs were able to increase the length of selected neuronal processes after their addition to the culturing medium.