Chiral Modification of the Pd(111) Surface By Small Organic Molecules

Chiral modification of a metal surface is one of the most successful approaches of achieving enantioselective catalysis in heterogeneous phase. In this approach, an active metal surface is directly modified by adsorption of a chiral molecule (chiral modifier), the metal is responsible for catalytic activity while the adsorbed modifier controls the stereochemistry of adsorption and subsequent reactions through substrate interactions. So far, there are three types of widely recognized metal/modifier catalytic systems: tartaric acid modified Ni catalysts for the hydrogenation of β-ketoesters, cinchona modified Pt catalysts for hydrogenation of α-ketoesters and Pd catalysts modified with cinchona for selective activated alkene where high activity and enantiomeric excess is gained in comparison to the unmodified surfaces. However, the exact manner in which chirality is bestowed to a metal surface and how that affects a chiral reaction is not well understood and warrants the development of model studies (surface science analysis on well-defined single crystal surfaces under ultrahigh vacuum conditions). These model studies and surface science analysis are necessary to promote the fundamental understanding and to facilitate the rational design of a suitable metal/modifier system which is the principal focus of this dissertation. This dissertation is primarily focused on two aspects. First, a number of complementary surface science studies have been performed to characterize four different chiral modifiers: D-alanine, (S,S) tartaric acid, L-aspartic acid and α-(1-naphthyl) ethylamine on a Pd(111) surface to gain insight into the way in which they impart chirality to the surface. Second, the enantioselectivity of the chirally modified surfaces has been measured in ultrahigh vacuum. This has been achieved by exposing the modified surface to both enantiomers of another chiral molecule (the probe), to see if there is any enantiospecific interaction between the modifier and the probe. The enantioselectivity is measured from the enantioselectivity ratio which is the ratio of relative coverages of two enantiomers of the probe on a surface modified with a single enantiomer of the modifier. Combined experimental results and theoretical density functional theory calculations suggest that the amino acid modifiers impart chirality to the Pd(111) surface by an ensemble mechanism where they work collectively to form discrete chiral templates which interact with the chiral probe propylene oxide and glycidol enantiospecifically whereas, tartaric acid and naphthylethylamine provide individual chiral motifs which interact with the probes in a one to one fashion

Hierarchical Intermolecular Interaction Models of N-Heteroaromatic STM Adlayer Structures

The molecular scale electronic device concept was initiated in 1974 with the semi-quantitative analysis of a hemiquinone molecule. Because of the molecule's electron donor and acceptor properties, and ability to transfer electrons along the -network, it was proposed that the molecule could perform as a circuit rectifier. Many investigations of molecular scale systems have occurred since then, in particular, of organic molecules with large, fused ring systems that spontaneously self-organize after deposition onto a substrate. The directionality and molecular specificity of hydrogen bonding differentiates it from the other weak interactions, driving molecules into specific arrangements and enabling spontaneous rearrangement after addition of only a small amount of enthalpic energy. A direct application of molecular recognition through self-assembly has been the design of patterned self-assembled monolayers (SAMs) for the construction of microelectrodes and supramolecular templates. However, the intermolecular interactions that drive ordered structures to form, including molecular chains and large aggregates, has not been well understood. To elucidate a quantitative description of the intermolecular forces of network systems of aromatics that control such features as packing density and porosity, two individual model heteroaromatic systems of 9-acridinecarboxylic acid and isonicotinic acid are investigated using both experimental and computational resources. Supported by scanning tunneling microscopy (STM) topographies, x-ray diffraction (XRD) data and x-ray photoelectron (XPS) spectra, this class of N-heteroaromatics adsorbed on Ag (111) serves as a model system to systematically investigate 2-dimensional intermolecular (2-D) interactions and their impact on forming different structural phases of molecular chain domains. To approach an understanding of the dynamics of N-heteroaromatic film growth, an intermolecular interaction model of 1-D single phase chains and clusters is performed. The model considers the anisotropy of the electrostatic force interactions to determine what charge arrangements (dipole, quadrupole, etc.) better characterize the molecular interactions. Furthermore, the competition between phase chain types is shown to be length dependent and in qualitative agreement with the coverage dependent STM structural phase composition

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Department of Urban and Environmental Engineering (Environmental Science and Engineering)Water resource is essential for humans and many places on the earth, and there needs to solve freshwater shortage caused by water pollution by industrial and farming activities. Nanofiltration (NF) technique has been attracted a lot during past decades, because of its unique characteristics which are utillizing separation mechanisms of both solution diffusion (as in reverse osmosis) and sieving (as in ultrafiltration), resulting to obtain high rejection of divalent salts and organic molecules with low molecular weight (Mw from 200 to 1000) at low operating pressure. Currently, commercial NF polyamide (PA) thin-film composite (TFC) membranes have been generally produced by interfacial polymerization method using piperazine (aliphatic amine monomer) or m-phenylenediamine (MPD, aromatic amine monomer) reacting with trimesoyl chloride (TMC, acyl chloride monomer). The interfacial polymerization methods using piperazine/MPD and TMC are one of the most effective methods to fabricate TFC NF membranes, because the thin/dense polyamide selective layer can make high water flux at low driving-pressure, and the permeable properties can be optimized by several fabrication factors (e.g., monomer concentrations, effective additives, reaction times, and curing time/temperature for post-treatment). The NF technique has been broadly applied to treatment/recycle of the target compounds in acidic conditions: (I) exclusion of heavy metals and sulfate ions in the mining and metal industry, (II) recycling of phosphorus in sewage sludge, (III) treatment of nitric acids in the picture tube production, (IV) regeneration of acidic effluents in dairy cleaning-in-place processes, (V) purification of acidic effluents in the pulp and paper industry, and (VI) separation of plentiful acids such as HBF4, HCl, HNO3, H2SO4, H3BO3 in effluents from rinsing, fermentation, and extraction processes. Additionally, NF technique can be applied to wastewater containing HCl, HBr and HI from semiconductor???s etching process. Acid-stable NF membranes are needed to apply above processes which operate with acidic condition. However, high performance commercial NF semi/full-aromatic PA membranes, which are fabricated by piperazine/MPD with TMC, are limited in the range of pH 2 to 11 in accordance with suppliers. The previous studies were mainly investigated to effect of acidic conditions on PA membranes in the view of permeability. However, both changes of physical and chemical properties by degradation mechanism have not been systematically discussed for semi/full-aromatic membranes after exposure to various acidic conditions up to now. Therefore, a detailed research needs to elucidate effect of acidic degradation on physical and chemical properties of PA membranes using various analytical tools and computational calculation methods. The overall objectives of this work is to systematically examine the effect of the acidic conditions on semi/full-aromatic PA membranes in terms of changes of physical/chemical properties, and to suggest mechanism to explain changed the properties as well as applications for practical fields via various analytical tools: Scanning Electron Microscopy (SEM), Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), contact angle analyzer, electrophoretic light scattering spectrophotometer, filtration tests, and density functional theory (DFT) computational calculations. Experimental results from degradation by acid showed different tendency between semi and full-aromatic PA membrane using acidic aqueous solution (15wt% sulfuric acid). According to analyses of the membrane???s physical and chemical properties (e.g., SEM, ATR-FTIR, XPS, and filtration tests), full-aromatic PA membrane had relatively higher acid-stability than semi-aromatic PA membrane. These degradations by acid cause conversion of an amide group to carboxyl and amine groups measured by ToF-SIMS results. Furthermore, these converted carboxyl and amine groups decreased the contact angle and increased the absolute value of the zeta potential semi-aromatic PA membranes. These difference of acid-stability between semi and full-aromatic PA membrane is resulted from relatively lower energy barrier of semi-aromatic PA membrane in the RDS step. These energy barrier results in the RDS had a close relationship with protonated amides??? twist angle (??D), which shows representative and quantitative value for resonance of amide group. However, full-aromatic PA membrane with relatively higher acid-stability were also severely degraded when it exposed to pH 0 acidic solution containing hydrogen halides. For example, in ATR-FTIR results, amide II band (N-H) in 1541 cm-1 and amide I band (C=O) in 1663 cm-1 after degradation by hydrogen halides tended to decrease due to halogenation reacted with halogens generated by oxidation of hydrogen halides. In addition, water flux after exposure to hydrogen halides tended to severely decrease with increasing exposure time, resulted from broken hydrogen bonding due to halogenation. Meanwhile, acid-catalyzed hydrolysis, which causes conversion amide group into amine and carboxyl group, were applied to post-treatment of semi-aromatic PA membrane in terms of practical applications (e.g., water softening and enrichment of antibiotics). Post-treatment by sulfuric acid in the range of pH 0 to 2 increased membrane???s hydrophilicity, pore size, and absolute value of surface charge. In accordance with change of surface characteristics, mixture selectivity (Na+/Mg2+) for water softening was improved about 2.6 times in acidic conditions. Optimized post-treatment membranes were applied to the enrichment of antibiotics as well, and the membrane had higher water flux and competitive antibiotics rejection compared to other commercial or fabricated membranes. That is, operation time of optimized membrane was improved about 2 to 3 times than virgin semi-aromatic membrane.ope

X-ray Absorption Fine Structure Studies of Calcium Silicate Hydrate Biomaterials in Drug Delivery

Calcium silicate hydrate (CSH), a new type of bioceramics, has gained significant attention in hard tissue restoration because of their impressive role in the stimulation of osteoblast proliferation and differentiation in vitro. The further development of mesoporous bioceramics opens up new opportunities for drug delivery in hard tissue therapies. In this thesis, interaction mechanisms of drug molecules with CSH of different morphologies and CSH/polymer composites, imaging of drug distributions in CSH carriers in nanoscale, and the biomineralization mechanisms of CSH in vitro during drug release are extensively investigated using X-ray absorption near edge structure (XANES) and scanning transmission X-ray microscopy (STXM). The interactions between different drug molecules and CSH with different morphologies are investigated using XANES. It is found that the morphology and the presence of hydrates of drug carriers influence the drug loading capacities (DLCs). CSH provides active linkage sites (Ca-OH and Si-OH groups) for the acidic functional groups of drug molecules via electrostatic interactions. Besides, it is also found that the stoichiometric ratio of Ca2+ ions of CSH carriers to the functional groups of drug molecules will significantly influence the DLCs.The mapping of an individual CSH microsphere, which was synthesized by a sonochemical method, before and after the loading of ibuprofen (IBU) is recorded by STXM. This STXM-XANES study illustrates the integrity and the homogenously distribution of drug molecules in these drug carriers. The biomineralization of the drug carrier, CSH microspheres upon IBU release, are monitored with XANES and STXM. The biomineralization mechanisms for CSH microspheres loaded with IBU in the SBF solution, which were still controversial before, emerge via STXM mapping, spectral comparisons and fitting analysis. Finally, CSH/polymer composites were synthesized using a controlled precipitation reaction between calcium salt and silicate salt, followed by the addition of various polymer solutions iv at room temperature. The interactions between different polymers and CSH, the interactions between drug molecule IBU and these polymer composites have been extensively studied by XANES. We find that the polymers alter the structure of CSH to various degrees, and that this behaviour further influences the DLCs and drug release kinetics

MECHANISMS OF HETEROGENEOUS OXIDATIONS AT MODEL AEROSOL INTERFACES BY OZONE AND HYDROXYL RADICALS

Atmospheric aerosols play an important role in climate by scattering and absorbing radiation and by serving as cloud condensation nuclei. An aerosol’s optical or nucleation properties are driven by its chemical composition. Chemical aging of aerosols by atmospheric oxidants, such as ozone, alters the physiochemical properties of aerosol to become more hygroscopic, light absorbing, and viscous during transport. However the mechanism of these transformations is poorly understood. While ozone is a protective and beneficial atmospheric gas in the stratosphere, it is a potent greenhouse gas in the troposphere that traps heat near the Earth’s surface. It also impacts human heath by irritating the respiratory tract and exacerbating cardiovascular diseases. Additionally, ozone can alter the ecosystem through oxidizing plant foliage which can lead to deforestation and crop losses as well. Both gases and aerosols in the troposphere can react with ozone directly and indirectly with hydroxyl radicals. While daytime aging is thought to be primarily driven by photochemical processes and hydroxyl radicals, ozone is thought to be a key player in nighttime or dark aging processes that can alter the physicochemical properties of aerosols. Measured concentrations of trace gases and aged aerosol components in the field are higher than values predicted based on laboratory studies and computer simulations. Consequently, new experimental approaches are needed to narrow the gaps between observations and mechanistic understandings. In this dissertation, a plume of microdroplets was generated by pneumatically assisted aerosolization and then exposed to a flow of ozone before entering a mass spectrometer. This surface-specific technique allowed for the real-time analysis of reaction products and intermediates at the air-water interface. This work explores the in situ oxidation of iodide, a component of sea spray aerosols, by 0.05 – 13.00 ppmv ozone to explore how heterogeneous oxidation could enhance the production of reactive iodide species. Methods to study the reaction channels and intermediates were also established to not only determine a mechanism of iodide oxidation by ozone, but to enable the study of more complex systems. The developed approach was then applied to examine the oxidation of catechol and its substituted cousins, a family of compounds selected to model biomass burning and combustion emissions, at the air-water interface. While literature suggested that the primary mechanism of catechol oxidation by ozone would be the cleavage of the C1-C2 bond, it was determined that this was only a minor pathway. An indirect oxidation channel dominated heterogeneous processes at the air-water interface, giving rise to hydroxyl and semiquinone radicals that recombine to produce polyhydroxylated aromatics and quinones. This new mechanism of aging represents an overlooked channel by which brown, light-absorbing carbon aerosols are produced in the atmosphere. In addition, the work investigates how reactions on solid particulate aerosols proceed under variable relative humidity. Thin films were developed alongside a novel flow-through reactor to study of how aerosols are transformed by ozone and hydroxyl radicals when exposed to 50 ppbv - 800 ppmv of ozone. This system was employed to probe how catechol reacts with ozone under variable relative humidity. Further work was undertaken to model the adsorption process at the air-solid interface under variable humidity, permitting the estimation of the reactive uptake of ozone by the film at concentrations (50-200 ppbv) seen in rural and urban areas. Together, these results provide an increased understanding of how heterogeneous oxidation of aerosols contributes to aerosol aging processes as well as free radical production in the troposphere

SYNTHESIS, CHARACTERIZATION AND APPLICATIONS OF REDUCED GRAPHENE OXIDE AND COMPOSITE MEMBRANES FOR SELECTIVE SEPARATIONS AND REMOVAL OF ORGANIC CONTAMINANTS

Among the next generation materials being investigated for membrane development, partially reduced Graphene Oxide (rGO) has received increasing attention from the membrane community. rGO-based nanofiltration membranes have shown promising results in applications such as partial desalination, organic contaminant removal, gas-phase separations, and separations from solvent media. rGO offers a unique platform compared to common polymeric membranes since it can be used for separation applications in both aqueous and organic solvent media. An rGO-based platform could also be utilized to synthesize reactive membranes, giving rGO membranes the additional capability of reactively removing organic contaminants. This research focuses on the synthesis of rGO and nanocomposite membranes for applications including the separation of high-value phenolic compounds from a solvent-water mixture, removal of organic contaminants, and treatment of refinery wastewater. First, the behavior of a rGO membrane in water and isopropanol was investigated along with its ability to separate high-value, lignin-derived oligomeric compounds from a solvent-water mixture. This study revealed the formation of stable sorbates of water in the GO channels that resulted in declined membrane permeance and improved size-exclusion cutoff. Through controlled reduction of GO by heat treatment, it was demonstrated that physicochemical properties of the GO membrane could be modulated and separation performance tuned based on the extent of reduction. A varying degree of interlayer spacing was attained between the GO laminates by controlling the O/C ratio of GO. This allowed the rGO membrane to achieve tunable molecular separation of lignin-derived model oligomeric compounds from a solvent-water mixture. Second, the mechanism of ionic transport through the rGO membrane was studied as well as its application in partial desalination and removal of persistent organic contaminants from water. Through comprehensive experimental investigations and mathematical analysis, along with the aid of the extended Nernst Planck equation, the impacts of steric hindrance and charge interactions on the underlying ion transport mechanism were quantified. Charge interactions were observed to be the dominant exclusion mechanism for the rGO membranes. The application of rGO membranes for treatment of high TDS produced water was investigated with the goal of partial hardness and dissolved oil removal. In addition, this study demonstrated the removal of emerging organic contaminants, specifically perfluorooctanoic acid, by rGO membranes and elucidated a charge interaction-dominated exclusion mechanism for this contaminant, as well. Finally, rGO-based and microporous polyvinylidene fluoride (PVDF)-based catalytic membrane platforms were synthesized for removal of organic contaminants via an oxidative pathway. Herein, an advanced oxidation process was integrated with membrane technology by the in-situ synthesis of Fe-based nanoparticles. The unique capability to oxidatively remove contaminants in a continuous mode of operation was explored in addition to the separation performance of the membrane. The rGO-based platform achieved high oxidative removal of trichloroethylene via a sulfate-free, radical-mediated pathway, while simultaneously removing humic acids from water and potentially eliminating undesired side reactions. A PVDF-based microporous catalytic membrane platform was shown to effectively remove organic impurities, such as Naphthenic acids, from high TDS produced water by the same pathway. The enhancement of reaction extent for elevated temperatures and longer residence times was also quantified in this study. These studies benefit the membrane community in the following ways: 1) The work identifies the critical role of the physicochemical properties of GO, such as the O/C ratio and water sorption, for determining the permeability-selectivity of rGO membranes for solvent nanofiltration. 2) Investigations of ion transport through rGO membranes led to an understanding of a charge-dominated separation mechanism for ion retention. The Nernst-Planck equation-based approach employed in this study would enable further assessment and comparison of rGO membranes under a wide set of parameters. 3) Catalytic membrane platforms (rGO and microporous PVDF-based) were synthesized for conducting advanced oxidation reactions in the porous membrane domain, demonstrating potential applications in environmental remediation of organic contaminants

Surface-Mounted Metal-Organic Frameworks as the Platform for Surface Science: Photoreactivity, Electroreactivity, and Thermal Reactivity

Bisher haben Forscher Modellsysteme wie Einkristallmetalle oder Metalloxide entwickelt, um reale Pulversysteme besser zu verstehen. Es bestehen jedoch immer noch Fragen hinsichtlich der Oberflächenstruktur und Reaktivität von MOFs (Metall-organische Gerüstverbindungen). Glücklicherweise bieten oberflächenorientierte SURMOFs (surface-oriented SURMOFs) einen alternativen Ansatz für den Aufbau von Modellplattformen zur Untersuchung dieser grundlegenden Aspekte von MOFs. Diese Arbeit konzentriert sich auf die organische Photochemie, Elektrokatalyse und thermische Pyrolyse von MOFs aus einer physikalisch-chemischen Perspektive unter Verwendung von Oberflächenwissenschaftstechniken und SURMOF-Plattformen. Das Ziel dieser Arbeit besteht nicht nur darin, das Wissen über MOFs und SURMOFs zu erweitern, sondern auch die Leistungsfähigkeit von Oberflächenwissenschaftstechniken und -methoden im Bereich chemischer Reaktionen zu demonstrieren. Zu diesem Zweck verwendet die Arbeit eine hochmoderne UHV-IRRAS-Apparatur (Ultra-High-Vacuum Infrared Reflection Absorption Spectroscopy). Ein auf der Oberfläche montiertes MOF (SURMOF) Modellsystem mit Azid-Seitenketten wurde erfolgreich hergestellt und genau überwacht, um chemische Veränderungen während des Betriebs zu erfassen. Die umfassenden Ergebnisse, die durch die Kombination von IRRAS mit in situ XRD, MS und XPS erzielt wurden, zeigen, dass die Photoreaktion von Azid durch die Bildung von hochaktiven Nitren-Gruppen initiiert wird, die anschließend mit benachbarten C=C-Bindungen des Gerüsts reagieren und Pyrrol-Derivate durch intramolekulare Aminierung erzeugen. Ein hochwertiges ZIF-67-SURMOF wurde in einem Flüssigphasen-Schicht-für-Schicht-Verfahren hergestellt und erstmals in der Sauerstoffentwicklungskatalyse (OER) eingesetzt. Die katalytisch aktiven Spezies, CoOOH, in den SURMOF-Derivaten wurden identifiziert, was Einblicke in die Mechanismen der strukturellen Transformation und die Struktur-Leistung-Beziehungen bietet. Durch Zugabe von Ni und B wurde die Überspannung auf 375 mV bei 10 mA/cm2 reduziert. Zusätzlich wurden in situ IRRAS und XPS verwendet, um die strukturellen Übergänge von ZIF-67 zu kohlenstoffhaltigen Materialien mit Stickstoffelementen zu enthüllen. NEXAFS-Daten zeigen eine abschließende graphitische Struktur der kohlenstoffhaltigen Materialien nach Pyrolyse bei 900 K. Hoffentlich kann diese Arbeit das grundlegende Verständnis und die Anwendungsfelder von auf MOF und SURMOF basierenden Materialien erweitern

Spectroscopic investigations at the diamond-water interface

Artificial Photosynthesis is a promising approach to tackle the increasing challenges of global warming. However, the direct conversion of CO2 to other chemicals presents major kinetic challenges, evoking exploration of abundant, cost effective and sustainable photocatalysts. Diamonds are promising candidates as H-terminated diamond surfaces exhibit excellent electron emission characteristics in water because of their negative electron affinity. However, due to their wide band gap of 5.4 eV, the generation of solvated electrons, requires the photoactivation of diamond using deep UV radiation which is scarcely available in the solar spectrum. In this thesis two strategies are investi- gated to enable visible light absorption and enhance electron emission from diamonds. Specifically, the effect of B, N and P doping on the electronic structure of diamonds were investigated using soft X-ray ab- sorption spectroscopy at C K edge. The results of our study revealed that combining nanostructuration with B-doping leads to introduction of new electronic states close to both the valence band maximum and the conduction band minimum in B-doped diamonds. As an alternative strategy, the electronic structure of nanodiamonds sensitized with Ru(bpy)3 was probed. These studies presented evidence of electronic coupling between the Ru complex and the nanodiamonds with the HOMO of Ru(bpy)3 lying above the valence band minimum of the diamonds. As a result of this band alignment, the dye acts as an electron donor and can potentially refill the photogenerated holes in the valence band of diamonds. Since photoactivation of diamonds generates solvated electrons in water, it is also important to un- derstand the diamond-water interface. To this aim, infrared spectroscopy was used to elucidate the influence of different pH conditions on the surface interactions of ND-OH surfaces at the diamond- water interface. This study provided insights that could help to determine the optimal environment that would enhance electron emission from these surfaces. Based on the results, a possible forma- tion of oxonium ions on an ND-OH surface in acidic conditions could be deduced. These oxonium ions could potentially form a charge stabilization layer with water molecules, thereby enhancing electron emission which could be advantageous for photocatalytic reductions. The results further suggested a possible aging mechanism of ND-H surfaces under long term UV irradiation. For efficient photoelectro- catalytic CO2 reduction, diamonds were also co-promoted by Cu2O to form a hybrid photocatalyst. The electronic structure of this hybrid material was probed at the Cu L edge to explain the role of diamond in this hybrid material. It was found out that diamond indeed acts as a very stable support for Cu2O thereby decelerating the process of aging and subsequent deactivation of the catalyst. With this work, we thus, aim to highlight some of the characteristics of diamonds that would enable the development of diamond based photocatalysts in the future.Die künstliche Photosynthese ist ein vielversprechender Ansatz, um den wachsenden Herausforderungen der globalen Erwärmung zu begegnen. Die direkte Umwandlung von CO2 in andere Chemikalien stellt jedoch eine große Herausforderung dar, die zur Erforschung zahlreicher, kostengünstiger und nachhaltiger Photokatalysatoren führt. Aufgrund ihrer großen Bandlücke von 5,4 eV sind Diamanten vielversprechende Kandidaten. Denn H- terminierte Diamantoberflächen weisen aufgrund ihrer negativen Elektronenaffinität in Wasser hervorragende Elektronenemissionseigenschaften auf. Die Erzeugung von solvatisierten Elektronen erfordert jedoch die Photoaktivierung von Diamanten mit tiefer UV-Strahlung, die im Sonnenspektrum kaum verfügbar ist. In der vorliegenden Arbeit wurden zwei Strategien untersucht, um die Absorption des sichtbaren Lichts zu ermöglichen und die Elektronenemission von Diamanten zu verbessern. Insbesondere wurden die elektronischen Strukturen von p- und n-Diamanten mit B-, N- bzw. P-Dotierung mittels weicher Röntgenabsorptionsspektroskopie an der C-K-Kante untersucht. Diese Untersuchungen zeigten, dass die Kombination von Nanostrukturierung mit B-Dotierung neue elektronische Zustände erzeugt, die sowohl dem Valenzbandmaximum als auch dem Leitungsbandminimum in B-dotierten Diamanten nahe kommen. Als alternative Strategie wurde die elektronische Struktur von Nanodiamanten untersucht, die mit Ru(bpy)3 sensibilisiert sind. Diese Studien zeigten eine elektronische Kopplung zwischen dem Ru-Komplex und den Nanodiamanten, wobei das HOMO von Ru(bpy)3 über dem Valenzband Minimum der Diamanten lag. Durch diese Bandausrichtung wirkt der Farbstoff als Elektronendonor und kann die photogenerierten Löcher im Valenzband der Diamanten potenziell wieder auffüllen. Da die Photoaktivierung von Diamanten im Wasser solvatisierte Elektronen erzeugt, ist es auch wichtig, die Grenzfläche zwischen Diamant und Wasser zu verstehen. Wir untersuchten die Interaktion von OH- terminierten Diamant-Oberflächen mit Wasser bei unterschiedlichen pH-Werten, um die Elektronenemission von diesen Oberflächen zu verbessern. Es stellte sich heraus, dass unter sauren Bedingungen auf einer ND-OH-Oberfläche möglicherweise Oxoniumionen gebildet werden, die mit Wassermolekülen eine ladungsstabilisierende Schicht bilden könnten. Diese wiederum könnte die Elektronenemission er- höhen und die photokatalytische Reduktion von CO2 begünstigen. Einen hybriden Photokatalysator mit Cu2O Schichten auf der Diamantenoberfläche wurde auch gebildet, als alternativen Weg für eine effiziente CO2-Photoreduktion. Die elektronische Struktur dieses Hybridmaterials wurde an der Cu-L-Kante untersucht, um die Rolle des Diamanten in diesem Hybridmaterial zu erklären. Es wurde herausgefunden, dass Diamant tatsächlich als sehr stabiler Träger für Cu2O wirkt, wodurch der Alterungsprozess und die daraus folgende Deaktivierung des Katalysators verzögert werden. Mit dieser Arbeit wollen wir daher die Eigenschaften von Diamanten beleuchten, um künftig die Entwicklung von einem diamantbasierten Photokatalysator zu ermöglichen

Formulation, Structure, and Applications of Therapeutic, Amino Acid, and Water-Based Deep Eutectic Solvents

In the design of greener chemicals, deep eutectic solvents (DESs) are considered as one of the most versatile alternative solvents with widespread applications. DESs have the advantages of being nonflammable with negligible vapor pressure compared to traditional solvents. They share many characteristics of ionic liquids, but DESs are cheaper to formulate, typically nontoxic, recyclable, biodegradable, and are suitable for use with biological systems. In my Ph.D. research, three types of emerging and unconventional types of DESs, namely therapeutic DES (THEDES), amino acid-based DES (AADES), and water-based DES (WDES), have been investigated. To formulate these DES easily available and cheaper chemicals, such as water, choline chloride, menthol, aspirin, glutamic acid, arginine, and glycerol, were used. Besides formulation, experimental structural characterization, and rigorous computational studies, some of their preliminary applications have been explored to understand their potential area of applications. Formulation for poorly soluble drugs as THEDESs could enhance their solubility significantly and AADES were used to selectively depolymerize lignin. A complete characterization of WDES and solubility of salt or drug was explored. The structures and structural properties of the DES studied were explored rigorously, as these insights can help to make them more effective. The major aim of the research projects was to find out the gaps of the DES research and provide a solid background for future research. Combining the molecular dynamics (MD), density functional theory (DFT), spectroscopic (Raman, IR, and VCD) techniques, solvatochormism, cheminformatics, and chromatographic techniques helped to understand the behavior and potential of the studied formulations. For example, atom-atom radial distribution functions (RDFs) based on MD simulation reveal that hydrogen bonds are formed between Cl-…HOCh+ and Cl- …HOCOOH of the THEDES, where Cl- works as a bridge between ASA and Ch+. Cationanion electrostatic attractions are disrupted by highly interconnected hydrogen bonds. Nonsalt HBA-HBD THEDES (1:1 L-Menthol: acetic acid) is also explored and found that their depression of melting point is mainly because of long network of hydrogen bond. Since menthol is a chiral molecular, VCD was found as a good tool to understand the behavior of chiral molecule-based DES. Melting points of WDESs (1:3 and 1:4 choline chloride: H2O) were found significantly low, -79.21 and -79.25 °C, respectively. TGA study proved that water could be relatively stable at a higher temperature when it forms the DESs. Solvent selectivity triangle (SST) of Kamlet-Taft parameters proved that the DESs possess similar solvatochromic properties to ionic liquids. A simple analytical method was developed employing ion chromatography and atomic absorption spectroscopy to investigate the solubility of sodium halides, alkali chlorides, and cobalt chloride in the studied water-based DESs. Solubility trends of the metal halides in both DESs were found same, NaCl \u3e NaBr \u3e NaI \u3e NaF for sodium halides and LiCl \u3e NaCl \u3e KCl for alkali metal chlorides. Solubilities of the studied drug molecules such as aspirin were found to be 1.3 to 6.7 times higher in the solvents than their solubilities in water. Cell viability assay of the WDES1 (1:3 ChCl:H2O) compared to dimethyl sulfoxide (DMSO) against HEK293 cell line proved that the solvent is applicable to the biological system. The eutectic points of the formulated AADESs were -0.14°C for Glu-Gly and -1.36°C for Arg-Gly. FT-IR, 1HNMR spectroscopy, and mass spectrometry studies found that Glu-Gly formed ester impurities. However, mass spectrometry showed that the impurities are negligible. TGA revealed that both DESs could be applied up to 150-160°C without losing weight, while Glu-Gly could be used up to 200°C. AADESs are excellent pretreatment media for biomass, lignin was treated as a model biomass in this study with the formulated AADESs to determine their reaction products. It was found that Arg-Gly can isolate only one monomeric compound (4-methyl benzaldehyde), while Glu-Gly can isolate three monomeric compounds. Oxidative depolymerization of the lignin residues validated the outcomes obtained from the AADES-lignin reactions. Overall, this work helped to understand how to formulate novel DESs, their wide variety of characterizations, and possible application