In order to address the global challenges of climate change caused by the increasing concentration of carbon dioxide (CO2), Carbon Capture, Utilization and Storage (CCUS) has been proposed as a promising strategy in carbon management. In parallel with the target of zero emission in fossil-fired power plants, negative emission has also drawn a great deal of attention in other chemical sectors, including cement making and steel production industries. Thanks to the recent reduction in the cost of renewable energy sources, such as wind and solar, a paradigm shifting concept has emerged to directly convert the captured carbon into chemicals and fuels. In this way, decarbonization in various chemical sectors can be achieved with a reduced carbon footprint. A variety of carbon dioxide conversion pathways have been investigated, including thermochemical, biological, photochemical, electrochemical and inorganic carbonation methods. Electrochemical conversion of carbon dioxide has been thoroughly investigated with great progress in electrocatalysts and reaction mechanisms. However, fewer studies have been taken to tackle the constraint of the low solubility of CO2 in conventional aqueous electrolytes. In an effort to improve the solubility of CO2, various novel electrolytes have been designed with a higher uptake of CO2 and a compatibility with electrochemical conversion, including Nanoparticle Organic Hybrid Materials (NOHMs)-based fluids. NOHMs are a unique liquid-like nanoscale hybrid material, comprising of polymers grafted onto nanoparticles (e.g., silica). NOHMs have demonstrated an excellent thermal stability and a high chemical tunability. Two types of NOHMs with ionic bonding (I) between the polymers and nanoparticles were selected in this study: NOHM-I-PEI incorporating polyethylenimine polymer (PEI) and NOHM-I-HPE consisting of polyetheramine polymer (HPE), illustrative of two modes of carbon capture (e.g., chemisorption and physisorption). The NOHMs-based fluids were synthesized with different secondary fluids and salt to tune the viscosity and conductivity. As the first liquid hybrid solvent system for combined carbon capture and conversion, the physical, chemical and electrochemical properties of NOHMs-based fluids were systematically investigated. It was found that NOHMs-based aqueous fluids have exhibited a lower specific heat capacity than that of the 30 wt.% monoethanolamine (MEA) solvents. In addition, upon CO2 loading, the increase in specific heat capacity and the reduction of the viscosity of the NOHM-I-PEI based aqueous fluids can be attributed to the formation of intra-molecular hydrogen bonds. The different chemistries of the two NOHMs can be reflected by the viscosity-based mixing behavior. The smaller critical concentration and the higher intrinsic viscosity of NOHM-I-HPE based aqueous fluids implied a more significant contribution of viscosity to the system by the addition of NOHM-I-HPE. The viscosity of NOHM-I-HPE (30 wt.%) in water was measured to be 395 cP, an order of magnitude higher than that of NOHM-I-PEI (30 wt.%) in water, which was determined to be 22.6 cP. It was also discovered that the addition of N-methyl-2-pyrrolidone (NMP) has resulted in a dramatic increase of the viscosity of NOHM-I-PEI based aqueous fluids, hypothesized to be due to a possible formation of a complex between NMP and NOHM-I-PEI. On the other hand, the presence of 0.1 M potassium bicarbonate (KHCO3) salt greatly reduced the viscosity of NOHM-I-HPE based aqueous fluids. The electrochemical properties of NOHMs-based fluids were also characterized and an excellent electrochemical stability has been demonstrated. The conductivities of NOHMs-based fluids witnessed an unexpected enhancement from the corresponding untethered polymer-based solutions. At 50 wt.% loading, the conductivity was 15 mS/cm for NOHM-I-PEI based aqueous fluids doped by 1 M bis(trifluoromethylsulfonyl)amine lithium salt (LiTFSI), while it was 0.91 mS/cm for PEI based aqueous solutions. Even after the viscosities of the two solutions were converted to the same value, there was still a large gap between the conductivities of the NOHMs-based fluids and polymer-based fluids. The relative tortuosity of ion transport in NOHMs-based fluids compared to untethered polymer-based solutions was less than 1. This result was indicative of a shorter pathway of ion transport in NOHMs-based fluids than in polymer-based fluids. Thus, it is suggested that in addition to a viscosity effect, unique multi-scale structures were also formed, enabling an enhanced ion transport in the NOHMs-based fluids. With this hypothesis, ultra-small-angle X-ray scattering (USAXS) technique was utilized to construct the structures of NOHMs morphology in secondary fluids, from agglomerates at large scale to aggregates at mid-scale, and to the interparticle distance at small scale. The sizes of the aggregates and the interparticle distance were highly tunable by varying the concentrations of NOHMs, and the types of NOHMs and secondary fluids. For example, the aggregate size was (32.30 ± 0.3) nm and (153.9 ± 1.5) nm for 50 wt.% loading of NOHM-I-PEI and NOHM-I-HPE in mPEG, respectively. This hierarchical structure was hypothesized to give ions unique channels and pathways to migrate, resulting in the surprising conductivity enhancement. Cryogenic electron microscopy (CryoEM) was also employed to image such multi-scale fractal structures. The diffusion behavior under this hierarchical structure was studied subsequently. To our surprise, in certain NOHMs-based fluids, such as 10 wt.% NOHM-I-HPE in water at 25℃, the diffusion coefficient of water was 3.43×(10)^(-9) m2/s, higher than that of deionized water, 2.99×(10)^(-9) m2/s. This is evident of the channels created by NOHMs in the secondary fluids to allow faster local diffusion of water and ions. Meanwhile, the diffusion coefficient of NOHM-I-HPE was higher with the presence of 0.1 M KHCO3 salt compared to the salt-free case in water. Though counter-intuitive, this was because salt would interact with the ionic bonding sites of NOHMs, facilitating the dynamic hopping of polymers on the nanoparticle surface, and thus improving the fluidity of the NOHM-I-HPE based aqueous fluids. This investigation of multi-scale structures and diffusion behavior of NOHMs-based fluids was insightful in understanding how the ions move in the system, and in explaining the enhanced conductivity of NOHMs-based fluids compared to the corresponding untethered polymer-based solutions. It is believed that ions move in two regions of the NOHMs-based fluids, the NOHMs-rich region and secondary fluids-rich region, in the mechanisms of translational movement, and coupled and decoupled ion migration with structural relaxation of NOHMs and secondary fluids. With the understanding of the fundamental properties and the construction of hierarchical structures, the carbon capture performance was evaluated for NOHMs-based fluids. The carbon capture behavior can be tuned by the concentration of NOHMs, and the presence of salt and physical solvents. The carbon capture kinetics was determined by both the amount of the capture material and the viscosity of the fluids. It was determined that 30 wt.% NOHM-I-PEI based aqueous fluids exhibited an optimal balance between capture capacity and sorption kinetics. As the concentration of NOHMs further increased, the elevated viscosity of the system limited the mass transfer of carbon capture. It was also found that salt induced a minimal impact on carbon capture in the initial 100 min for 5 wt.% NOHMs loading, but would negatively impact the capture capacity and kinetics at higher NOHMs loadings. Meanwhile, the addition of physical solvent (NMP) reduced carbon capture capacity and kinetics. Various existing forms of CO2 have been identified in NOHMs-based fluids, including carbamate, bicarbonate, and physisorbed CO2. Carbamate came from the reaction between CO2 and the amine functional groups on NOHM-I-PEI. Physisorbed CO2 was identified as the electroactive species for electrochemical conversion of CO2. In the combined carbon capture and conversion experiments using 5 wt.% NOHM-I-HPE based aqueous electrolyte, carbon monoxide (CO) production was enhanced on polycrystalline silver by 60%, and selectivity was changed on a pyridinic-N doped carbon-based electrode, in comparison with conventional 0.1 M KHCO3 electrolyte. The roles of NOHMs in carbon capture and conversion were also explored. The addition of NOHMs was able to improve the solubility of CO2 with a tunable pH change. It is hypothesized that NOHMs can complex with the electrochemical reaction species,CO2 (CO2^-), and this complex formation can be tunable by the concentration and types of NOHMs. In the end, an alternative approach of utilizing NOHMs-based fluids has also been proposed through encapsulation. The encapsulation of NOHMs-based fluids has enabled a higher specific surface area for CO2 uptake, and an enhancement in capture kinetics has been observed compared to the non-encapsulated NOHMs-based fluids. In summary, a novel nanoscale hybrid solvent system has been developed for combined carbon capture and conversion. The insight into the chemistry of this hybrid solvent system is not beneficial to the advancement in carbon capture and conversion, but it is also enlightening for the interdisciplinary development of various areas involving nanoscale hybrid materials.

Within living organisms in the natural world, highly complex systems have evolved over billions of years to carry out the specific synthetic functions required to support and propagate life. Nature's use of biological machines for the synthesis of functional molecules has inspired synthetic chemists from a broad range of specialisms to design artificial molecular machines and systems capable of facilitating non-trivial synthetic tasks. A core strategy employed in attempting to emulate biological machines for synthesis has been to mimic Nature's ability to compartmentalise discrete aspects of a synthetic process. Rotaxanes are favourable architectures around which to design molecular machines as their mechanically-interlocked nature provides the chemist with a unique means by which to achieve compartmentalisation and to control the effective molarity of non-covalently linked components. The research presented in this thesis investigates the design, synthesis and operation of novel, rotaxane-based molecular machines for the non-trivial assembly of individual amino acid building blocks into information-rich oligopeptides. The artificial devices described herein each endeavour to emulate (in a primitive manner) one of Nature's most remarkable machines for synthesis: the ribosome. Information is programmed into these 'synthetic ribosomes' through their careful design and modular assembly; upon operation of the artificial molecular machine, this transcribed information is translated into a pre-defined oligopeptide product. The research presented in this thesis is laid out as follows:Chapter 1 reviews the current state of the art in biomimetic molecular machines and systems capable of promoting non-trivial synthetic tasks;Chapter 2 describes a molecular machine capable of non-proteinogenic oligopeptide synthesis via the sequence-specific assembly of beta-homo amino acid building blocks;Chapter 3 presents a device which operates upon a polymer to assemble individual leucine units into a homo-oligopeptide. This product forms a secondary alpha-helical structure capable of asymmetric organocatalysis in the Juliá-Colonna epoxidation of chalcone derivatives;Chapter 4 details a novel mode of amide-bond-forming catalysis for rotaxane-based molecular machines with a view to assembling an advanced peptidic precursor to Penicillin G.Chapters 2 and 3 are presented as manuscripts which have been compiled for peer-review publication and which represent the collaborative efforts of the Author and the researchers indicated at the beginning of each chapter. The Author's contributions are also outlined at the beginning of each chapter. These manuscripts have been modified only to ensure consistency with the other chapters contained in this thesis.

At last, a thermal evaporation method that modifies the surface of ZnO nanorods and forms core shell structure is developed, which structure constitutes the photoelectrode for solar energy application. Single crystal ZnO nanorods are uniformly covered by wurtzite polycrystalline CdxZn1-x SySe1-y layer. The band gap of the shell can be systematically tuned from 2.5 to 1.7 eV by varying its composition, as suggested by the optical extinction measured of the samples. The type II band alignment between the ZnO core and the alloy shell enables effective photo-generated charge carrier separation, and the single crystalline ZnO nanorod array provides a direct electrical pathway for the photo-injected electron transport. The nanocable solar cells exhibited short-circuit current ∼0.2 mA/cm 2 and open-circuit voltages of 0.45 V when illuminated with 100 mW/cm 2 simulated AM 1.5 spectrum. / Green emission is observed from the ZnO nanorods synthesized by both methods, which is commonly attributed to the surface defect emission from the nanostructure. We modify surface of the nanorods with SiO 2 and investigate the relation between green emission and the surface defect. However, the surface passivation fails to reduce the green emission significantly, suggesting that surface defects of ZnO are not necessarily responsible for the green emission, but the interior structure quality of the ZnO nanorods decides the luminescence behavior. / In this study, a solution chemistry based method to grow aligned ZnO nanorod arrays on Zn foil is developed at first. Effects of various growth parameters, including the temperature, solution composition and the concentration of individual components on the morphology, structural quality, and properties of the ZnO nanorods are studied. The average diameter of the nanorods in the array can be tuned from ∼20 nm to ∼150 nm by systematically changing the growth conditions. Nanorods with larger diameters are found to be of better structural quality as compared to the smaller diametered ones, as suggested by the cathodoluminescence measurement. Following similar logic, a vapor transport deposition route on controllable fabricating of the ZnO nanorod arrays is investigated. The average diameter of the ZnO nanorods can be tuned from less than 40 nm to larger than submicron, by controlling the fabrication conditions. Larger-diametered nanorods that grow on higher temperature zone are found to possess higher band edge to defect emission ratio. / One dimensional (1D) ZnO nanostructure becomes a research focus in recent years. On the one hand, ZnO itself possesses structural, electrical and optical properties that make it useful for a diverse range of technological applications. On the other hand, semiconductor nanowire owns many advantages, such as superiority in electron transport and its high surface to volume ratio. Aligned ZnO 1D nanostructures on conducting substrates are of special interests, as they are easy to be integrated into devices, directly working as functional unit. / Jiao, Yang. / Adviser: Li Quan. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 107-109). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Jiao, Yang.

Qin Shuijie. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 109-123). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

This thesis presents a novel fabrication process to realize high-aspect-ratio, micron- and nano-sized probes and pipettes which can be used for biological applications. The basic fabrication process employs hydrofluoric (HF) acid to etch the outer layer of the end of capillary tubings and optical fibers as previously reported by other researchers. However, we invented a " sacrificial boundary etching" technique that can be used to shape capillary tubings and fibers into sharp micron-sized pipettes or probes with controllable tip angle. The tip profile and the length of its taper can be controlled by the initial height of HF acid inside a glass tube, which is used as a sacrificial material in shaping the tip profile. Our experimental results showed that capillary tubings and optical fibers can be sharpen into tips with angle as small as 2.1° and with tip diameter of ranging from 300 nm to 5 mum (the initial diameter being 125 mum). If the aspect-ratio (A.R.) of a probe is defined as the ratio between the length of its taper distance and the length of its base diameter, the A.R. for our fabricated probe can be as high as 10∼15. We also conducted cell probing experiments by using the fabricated probe. In addition, we performed microinjection of fluid into cells. On the other hand, by using the fabricated probe, an automated Carbon Nanotubes (CNTs) microspotting system was developed for rapid and batch assembly of bulk multi-walled carbon nanotubes (MWNTs) based nanosensors. By combining dielectrophoretic (DEP) and microspotting technique, MWNT bundles were successfully and repeatably manipulated between arrays of micro-fabricated electrodes. This feasible batch manufacturable method will dramatically reduce production costs and production time of nano sensing devices. / Lai Wai Chiu King. / "August 2005." / Adviser: Wen J. Li. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 4064. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 92-101). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Nan Gang Ma. / "October 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Nan Gang Ma.

A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in the School of Chemistry Faculty of Science, University of Witwatersrand, 2017 / Advancements in nanotechnology and nanosystems promise to extend limits of sustainable development and environment remediation in an attempt to address some of the world most challenging problems. Specifically, nanotechnology has played an important role in the design, synthesis, and characterization of various new and novel functional nanomaterials possessing extremely unique properties. For example, low dimensional nanostructures such as semiconductor nanocrystals with well controlled sizes, shapes, porosities, crystalline phases, and structures have been prepared via various synthetic methods. In addition these semiconductor nanocrystals have attracted research attention because of their fundamental role in the comprehension of the quantum size effect and great potential applications to save resources and improve the environment. Tremendous studies have established that morphological, optical, catalytic and electronic properties of semiconductor nanocrystals can be manipulated during synthesis by simply varying the growth parameters. Herein we establish the effect of different synthetic methods and several growth parameters on the properties of the as-synthesized semiconducting metal selenides nanocrystals (NixSey and InxSey) including structural, optical, electronic and catalytic properties. For example, reducing coordinating solvent oleylamine was seen to favour a particular morphologies and stoichiometries despite the duration of synthesis. In the case of InxSey nanocrystals, oleylamine favoured indium monoselenide (InSe) nanosheet formation while addition of 1-DDT as a co-surfactant to oleylamine produces In2Se3 nanowires. For NixSey nanocrystals, TOP as a co-surfactant to different ligands favoured the formation Ni3Se2 with different shapes including dots, plates, rods and wires in different solvents. Other parameters studied included the reaction time and temperature. Besides the properties, we probe the potential applications of these materials in dye sensitized solar cells as counter electrodes as well in chemical sensor as the sensing material. NixSey nanocrystals were employed as CE in DSSCs in an attempt to replace the noble expensive platinum conventionally used as CE in most DSSCs. It was established that different stoichiometry played a significant role in the catalytic reduction of I3-. Thus, different photovoltaic performance parameters were obtained with NiSe2 giving a higher PCE of 1.5 % followed Ni3Se4 then Ni3Se2. These values were however very low compared to the ones reported in literature, something that was attributed to low electron mobility, enhanced recombination and reduced catalytic performance as a result of poor device assembly and the organic ligand layer encapsulating the nanocrystal. In another scenerio, indium monoselenide nanocrystals were employed in chemiresistive sensors to detect the presence of a number of VOCs including formaldehyde, methanol, chloroform and acetone in the ambient. Indeed despite the well-known electrical, optical and structural properties previously reported in literature, metal selenides such as CdSe, PbSe and ZnSe among others present lack of investigation for gas sensing. The experimental results showed that different morphologies of InSe nanostructures interacted differently to the analyte gas suggesting difference in the electronic properties of different morphologies. The InSe nanoparticle based sensors gave a good response to HCHO and MeOH fumes and were more selective to HCHO fumes than chloroform and acetone. While those fabricated using the InSe nanosheets though responding well to HCHO recovered half way when exposed back in air and resulted in relatively high noise to signal ratio when exposed to MeOH. The operating temperature range for the InSe sensor devices were determined to be near room temperature. The sensors response was observed to decrease with increasing temperature from 30 °C to 90 °C. Evident from the results, the surface capping molecule (oleylamine) employed to stabilize the nanostructures during synthesis was responsible for the poor sensing abilities of the nanostructures. / XL2018

Large quantities of manufactured nanomaterials (MNM) are released into the environment by human activity each year. The entry of MNM into the terrestrial food webs, which has the potential for far-reaching impacts, begins with the uptake by plant species from the soil. These processes can be affected by MNM physico-chemical properties such as size, chemical composition, surface charge, etc., of which our knowledge is still incomplete. To bridge some of the gaps in our understanding of these processes and, specifically, to determine whether the physico-chemical properties of the MNM are predictive of their behavior in terrestrial food chains, we conducted a series of experiments using different MNM and model organisms. First, we synthesized functionalized CeO2 MNM having different charges and exposed tomato plants (Solanum lycopersicum cv Micro-Tom) to them. We found that plant growth and the rate of root-to-shoot translocation were functions of surface charge and exposure concentration. Mechanisms of entry into roots were examined using recent advances in high-resolution synchrotron X-ray microscopy to show that a combination of apoplastic and symplastic routes was used by the particles to penetrate to the interior of the roots. Our results also illustrate that these particles have drastically different tissue distribution patterns depending on their surface charges. Second, we exposed tomato plants with these CeO2 MNM and fed the leaves to the tobacco hornworm (Manduca sexta). Differential trophic transfer was observed as a function of the surface charge of the particles. An uptake and elimination study was conducted to obtain a time course of Ce dynamics. Despite no observed overall biomagnification across trophic levels, these differentially charged CeO2 MNMs had higher bioaccumulation factors than that of ionic Ce3+. The uptake-elimination dynamics were influenced by the surface charge of the NPs. Positively charged NPs had higher bioaccumulation factors and assimilation efficiencies but lower elimination rate than neutral and negatively charged CeO2 MNMs. Finally, to determine if studies conducted with highly purified, lab synthesized materials, were predictive of behavior of commercial nanopesticide formulations, we studied the dietary uptake of Cu(OH)2 MNMs by hornworms feeding on surface-contaminated tomato leaves. We compared lab-synthesized copper hydroxide (Cu(OH)2) nanowire with the widely used fungicide KOCIDE® 3000, whose active ingredient is nano-needles of copper hydroxide (Cu(OH)2). The difference in their toxicity and accumulation/elimination dynamics was found to correlate with the solubility of the materials. We have shown that the physico-chemical properties of MNM affect the toxicity, bio-distribution and trophic transfer of MNM in terrestrial ecosystems. With the increase of MNM release into the environment as a result of the rapid development of nanotechnology, these results have important implications for the evaluation of environmental risks associated with these MNMs and may help the application of nanotechnology to evolve to be more environmentally friendly.

Recent investigations have shown that engineered nanomaterials such as carbon nanotubes (CNTs) are a source and precursor for disinfection byproduct (DBP) formation. The aim of this study was to extend previous research of CNTs by investigating the potential for other classes of CNTs to generate disinfection byproducts (DBP) during chlorination. We examined particular types of CNTs with surface groups analogous to suspected model precursors for DBP formation.Specifically, we conducted experiments to determine the formation of haloacetic acids (HAAs) and N-nitrosodimethylamine (NDMA) via the chlorination of carbon nanotubes. Polymer coated CNTs generated the greatest total HAA concentration of up to 170 μg-HAA/mg-CNT. Results showed that the presence of surface oxide groups (e.g. surface carboxylic acid groups) promotes HAA formation. We observed a reasonably strong correlation between the extent of HAA formation and the concentration of surface oxygen on the CNT surface. Results also showed that CNTs behave similar to model precursors for di- and trichloroacetic acid formation (DCAA and TCAA, respectively). Nitrogen containing CNTs have been shown as source of N-nitrosodimethylamine (NDMA). Surprisingly, CS PEG, which does not contain N, produces NDMA when reacted with ethylenediamine (EDA). Ultimately, EDA is contributing N to CS PEG by sorbing to the CNT surface, which is the likely source of N for NDMA formation. At lower EDA concentrations, NDMA production is limited by available EDA. Conversely, at higher EDA concentrations, NDMA production is limited by available chlorine that is in competition with EDA and the CNT surface.

Thesis (Ph. D. in Chemical Engineering)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.