Synthesis of novel cobalt and iron complexes for sustainable catalytic hydrogenations

Aim of the present work of thesis is to synthesize new non-noble metal based complexes to be employ in redox reactions by a metal-ligand cooperative mechanism. The need of replacing toxic and expensive precious metal complexes with more available and benign metals, has led to the development of new compounds based on cobalt and iron, which are the metals investigated in this study. A carbonyl-tetrahydroborato-bis[(2-diisopropylphosphino)ethyl]amine-cobalt complex bearing a PNP-type ligand is synthesized by a three-step route. Optimization attempt of reaction route were assessed in order to lowering reaction times and solvent waste. New cobalt complex has been tested in esters hydrogenation as well as in acceptorless dehydrogenative coupling of ethanol. Other varieties of substrates were also tested in order to evaluate any possible applications. Concerning iron complex, dicarbonyl-(η4-3,4-bis(4-methoxyphenyl)-2,5-diphenylcyclopenta-2,4-dienone)(1,3-dimethyl-ilidene)iron is synthesized by a three steps route, involving transmetallation of a silver complex, derived from an imidazolium salt, to iron complex. In order to avoid solvent waste, optimization is assessed. Studies were performed to assess activity of triscarbonyl iron precursor toward imidazolium salt and silver complexes.

Untersuchungen von Aerosolpartikeln und Wolkenresidualpartikeln mittels Einzelpartikel-Massenspektrometrie und optischen Methoden

Atmosphärische Partikel beeinflussen das Klima durch Prozesse wie Streuung, Reflexion und Absorption. Zusätzlich fungiert ein Teil der Aerosolpartikel als Wolkenkondensationskeime (CCN), die sich auf die optischen Eigenschaften sowie die Rückstreukraft der Wolken und folglich den Strahlungshaushalt auswirken. Ob ein Aerosolpartikel Eigenschaften eines Wolkenkondensationskeims aufweist, ist vor allem von der Partikelgröße sowie der chemischen Zusammensetzung abhängig. Daher wurde die Methode der Einzelpartikel-Laserablations-Massenspektrometrie angewandt, die eine größenaufgelöste chemische Analyse von Einzelpartikeln erlaubt und zum Verständnis der ablaufenden multiphasenchemischen Prozesse innerhalb der Wolke beitragen soll.rnIm Rahmen dieser Arbeit wurde zur Charakterisierung von atmosphärischem Aerosol sowie von Wolkenresidualpartikel das Einzelpartikel-Massenspektrometer ALABAMA (Aircraft-based Laser Ablation Aerosol Mass Spectrometer) verwendet. Zusätzlich wurde zur Analyse der Partikelgröße sowie der Anzahlkonzentration ein optischer Partikelzähler betrieben. rnZur Bestimmung einer geeigneten Auswertemethode, die die Einzelpartikelmassenspektren automatisch in Gruppen ähnlich aussehender Spektren sortieren soll, wurden die beiden Algorithmen k-means und fuzzy c-means auf ihrer Richtigkeit überprüft. Es stellte sich heraus, dass beide Algorithmen keine fehlerfreien Ergebnisse lieferten, was u.a. von den Startbedingungen abhängig ist. Der fuzzy c-means lieferte jedoch zuverlässigere Ergebnisse. Darüber hinaus wurden die Massenspektren anhand auftretender charakteristischer chemischer Merkmale (Nitrat, Sulfat, Metalle) analysiert.rnIm Herbst 2010 fand die Feldkampagne HCCT (Hill Cap Cloud Thuringia) im Thüringer Wald statt, bei der die Veränderung von Aerosolpartikeln beim Passieren einer orographischen Wolke sowie ablaufende Prozesse innerhalb der Wolke untersucht wurden. Ein Vergleich der chemischen Zusammensetzung von Hintergrundaerosol und Wolkenresidualpartikeln zeigte, dass die relativen Anteile von Massenspektren der Partikeltypen Ruß und Amine für Wolkenresidualpartikel erhöht waren. Dies lässt sich durch eine gute CCN-Aktivität der intern gemischten Rußpartikel mit Nitrat und Sulfat bzw. auf einen begünstigten Übergang der Aminverbindungen aus der Gas- in die Partikelphase bei hohen relativen Luftfeuchten und tiefen Temperaturen erklären. Darüber hinaus stellte sich heraus, dass bereits mehr als 99% der Partikel des Hintergrundaerosols intern mit Nitrat und/oder Sulfat gemischt waren. Eine detaillierte Analyse des Mischungszustands der Aerosolpartikel zeigte, dass sich sowohl der Nitratgehalt als auch der Sulfatgehalt der Partikel beim Passieren der Wolke erhöhte. rn

Multifunctional polyether architectures : versatile materials for surface attachment and functionalization

Chapter 1 of this thesis comprises a review of polyether polyamines, i.e., combinations of polyether scaffolds with polymers bearing multiple amino moieties. Focus is laid on controlled or living polymerization methods. Furthermore, fields in which the combination of cationic, complexing, and pH-sensitive properties of the polyamines and biocompatibility and water-solubility of polyethers promise enormous potential are presented. Applications include stimuli-responsive polymers with a lower critical solution temperature (LCST) and/or the ability to gel, preparation of shell cross-linked (SCL) micelles, gene transfection, and surface functionalization.rnIn Chapter 2, multiaminofunctional polyethers relying on the class of glycidyl amine comonomers for anionic ring-opening polymerization (AROP) are presented. In Chapter 2.1, N,N-diethyl glycidyl amine (DEGA) is introduced for copolymerization with ethylene oxide (EO). Copolymer microstructure is assessed using online 1H NMR kinetics, 13C NMR triad sequence analysis, and differential scanning calorimetry (DSC). The concurrent copolymerization of EO and DEGA is found to result in macromolecules with a gradient structure. The LCSTs of the resulting copolymers can be tailored by adjusting DEGA fraction or pH value of the environment. Quaternization of the amino moieties by methylation results in polyelectrolytes. Block copolymers are used for PEGylated gold nanoparticle formation. Chapter 2.2 deals with a glycidyl amine monomer with a removable protecting group at the amino moiety, for liberation of primary amines at the polyether backbone, which is N,N-diallyl glycidyl amine (DAGA). Its allyl groups are able to withstand the harsh basic conditions of AROP, but can be cleaved homogeneously after polymerization. Gradient as well as block copolymers poly(ethylene glycol)-PDAGA (PEG-PDAGA) are obtained. They are analyzed regarding their microstructure, LCST behavior, and cleavage of the protecting groups. rnChapter 3 describes applications of multi(amino)functional polyethers for functionalization of inorganic surfaces. In Chapter 3.1, they are combined with an acetal-protected catechol initiator, leading to well-defined PEG and heteromultifunctional PEG analogues. After deprotection, multifunctional PEG ligands capable of attaching to a variety of metal oxide surfaces are obtained. In a cooperative project with the Department of Inorganic and Analytical Chemistry, JGU Mainz, their potential is demonstrated on MnO nanoparticles, which are promising candidates as T1 contrast agents in magnetic resonance imaging. The MnO nanoparticles are solubilized in aqueous solution upon ligand exchange. In Chapter 3.2, a concept for passivation and functionalization of glass surfaces towards gold nanorods is developed. Quaternized mPEG-b-PqDEGA diblock copolymers are attached to negatively charged glass surfaces via the cationic PqDEGA blocks. The PEG blocks are able to suppress gold nanorod adsorption on the glass in the flow cell, analyzed by dark field microscopy.rnChapter 4 highlights a straightforward approach to poly(ethylene glycol) macrocycles. Starting from commercially available bishydroxy-PEG, cyclic polymers are available by perallylation and ring-closing metathesis in presence of Grubbs’ catalyst. Purification of cyclic PEG is carried out using α-cyclodextrin. This cyclic sugar derivative forms inclusion complexes with remaining unreacted linear PEG in aqueous solution. Simple filtration leads to pure macrocycles, as evidenced by SEC and MALDI-ToF mass spectrometry. Cyclic polymers from biocompatible precursors are interesting materials regarding their increased blood circulation time compared to their linear counterparts.rnIn the Appendix, A.1, a study of the temperature-dependent water-solubility of polyether copolymers is presented. Macroscopic cloud points, determined by turbidimetry, are compared with microscopic aggregation phenomena, monitored by continuous wave electron paramagnetic resonance (CW EPR) spectroscopy in presence of the amphiphilic spin probe and model drug (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO). These thermoresponsive polymers are promising candidates for molecular transport applications. The same techniques are applied in Chapter A.2 to explore the pH-dependence of the cloud points of PEG-PDEGA copolymers in further detail. It is shown that the introduction of amino moieties at the PEG backbone allows for precise manipulation of complex phase transition modes. In Chapter A.3, multi-hydroxyfunctional polysilanes are presented. They are obtained via copolymerization of the acetal-protected dichloro(isopropylidene glyceryl propyl ether)methylsilane monomer. The hydroxyl groups are liberated through acidic work-up, yielding versatile access to new multifunctional polysilanes.

Caratteristiche chimico-fisiche e microbiologiche di salami in relazione al diametro e alla coltura starter impiegata.

I salumi fermentati sono prodotti caratterizzati da grandi differenze che riguardano la materia prima, gli ingredienti, le dimensioni e le condizioni di maturazione. Questa differenziazione è dovuta a pratiche storiche, culturali e tradizionali che variano da zona a zona. Il processo produttivo nel nostro Paese è però cambiato radicalmente grazie alle innovazioni tecnologiche. Tra queste l’introduzione delle colture starter ha rappresentato una garanzia di maggiore sicurezza igienica e sanitaria ma ha determinato una standardizzazione delle caratteristiche qualitative dei prodotti. Infatti, tutte le trasformazioni biochimiche che avvengono durante la maturazione possono essere influenzate dall’uso degli starter, così come dal diametro dei salami, che influenza la cinetica di perdita dell’acqua e la disponibilità di ossigeno all’interno del prodotto. Lo scopo del lavoro descritto nel mio elaborato è stato quello di valutare l’effetto di queste due variabili su alcune caratteristiche fisico-chimiche, microbiologiche e sul contenuto in amine biogene di salami prodotti industrialmente a partire dalla stessa miscela di ingredienti. Questo impasto carneo è stato addizionato di due starter diversi: oltre all’impiego di Staphylococcus carnosus, un primo lotto è stato inoculato con Lactobacillus sakei mentre un secondo con Pediococcus pentosaceus. Successivamente i due lotti sono stati insaccati in budelli sintetici aventi dimensioni diverse (grande con peso del prodotto all’insacco di 5.3kg e piccolo, con peso all’insacco di 385g). I risultati ottenuti da questa sperimentazione confermano il fatto che la dimensione è uno degli aspetti che maggiormente influenza la caratteristiche del prodotto. Inoltre, anche le colture starter hanno dato risultati diversi indipendentemente dal diametro, dimostrando la necessità di una più approfondita conoscenza tecnologica dei prodotti studiati in relazione alle attività microbiche che si svolgono durante la fermentazione e la maturazione.

The influence of saliva on the dissolution of calcium fluoride after application of different fluoride gels in vitro

OBJECTIVE: To determine the formation and dissolution of calcium fluoride on the enamel surface after application of two fluoride gel-saliva mixtures. METHOD AND MATERIALS: From each of 80 bovine incisors, two enamel specimens were prepared and subjected to two different treatment procedures. In group 1, 80 specimens were treated with a mixture of an amine fluoride gel (1.25% F-; pH 5.2; 5 minutes) and human saliva. In group 2, 80 enamel blocks were subjected to a mixture of sodium fluoride gel (1.25% F; pH 5.5; 5 minutes) and human saliva. Subsequent to fluoride treatment, 40 specimens from each group were stored in human saliva and sterile water, respectively. Ten specimens were removed after each of 1 hour, 24 hours, 2 days, and 5 days and analyzed according to potassium hydroxide-soluble fluoride. RESULTS: Application of amine fluoride gel resulted in a higher amount of potassium hydroxide-soluble fluoride than did sodium fluoride gel 1 hour after application. Saliva exerted an inhibitory effect according to the dissolution rate of calcium fluoride. However, after 5 days, more than 90% of the precipitated calcium fluoride was dissolved in the amine fluoride group, and almost all potassium hydroxide-soluble fluoride was lost in the sodium fluoride group. Calcium fluoride apparently dissolves rapidly, even at almost neutral pH. CONCLUSION: Considering the limitations of an in vitro study, it is concluded that highly concentrated fluoride gels should be applied at an adequate frequency to reestablish a calcium fluoride-like layer.

Efficacy of fluoride compounds and stannous chloride as erosion inhibitors in dentine

The aim of this study was to evaluate the anti-erosive effects of different fluoride compounds and one tin compound in the context of the complex pathohistology of dentine erosion, with particular emphasis on the role of the organic portion. Samples were subjected to two experiments including erosive acid attacks (0.05 molar citric acid, pH 2.3; 6 x 2 min/day) and applications (6 x 2 min/day) of the following test solutions: SnCl(2) (815 ppm Sn), NaF (250 ppm F), SnF(2) (250 ppm F, 809 ppm Sn), amine fluoride (AmF, 250 ppm F), AmF/NaF (250 ppm F), and AmF/SnF(2) (250 ppm F, 409 ppm Sn). The demineralised organic fraction was enzymatically removed either at the end of the experiment (experiment 1) or continuously throughout the experiment (experiment 2). Tissue loss was determined profilometrically after 10 experimental days. In experiment 1, the highest erosive tissue loss was found in the control group (erosion only); the AmF- and NaF-containing solutions reduced tissue loss by about 60%, reductions for SnCl(2), AmF/SnF(2), and SnF(2) were 52, 74 and 89%, respectively. In experiment 2, loss values generally were significantly higher, and the differences between the test solutions were much more distinct. Reduction of tissue loss was between 12 and 34% for the AmF- and NaF-containing preparations, and 11, 67 and 78% for SnCl(2), AmF/SnF(2), and SnF(2), respectively. Stannous fluoride-containing solutions revealed promising anti-erosive effects in dentine. The strikingly different outcomes in the two experiments suggest reconsidering current methodologies for investigating anti-erosive strategies in dentine.

Fluoride in dental erosion

Dental erosion develops through chronic exposure to extrinsic/intrinsic acids with a low pH. Enamel erosion is characterized by a centripetal dissolution leaving a small demineralized zone behind. In contrast, erosive demineralization in dentin is more complex as the acid-induced mineral dissolution leads to the exposure of collagenous organic matrix, which hampers ion diffusion and, thus, reduces further progression of the lesion. Topical fluoridation inducing the formation of a protective layer on dental hard tissue, which is composed of CaF(2) (in case of conventional fluorides like amine fluoride or sodium fluoride) or of metal-rich surface precipitates (in case of titanium tetrafluoride or tin-containing fluoride products), appears to be most effective on enamel. In dentin, the preventive effect of fluorides is highly dependent on the presence of the organic matrix. In situ studies have shown a higher protective potential of fluoride in enamel compared to dentin, probably as the organic matrix is affected by enzymatical and chemical degradation as well as by abrasive influences in the clinical situation. There is convincing evidence that fluoride, in general, can strengthen teeth against erosive acid damage, and high-concentration fluoride agents and/or frequent applications are considered potentially effective approaches in preventing dental erosion. The use of tin-containing fluoride products might provide the best approach for effective prevention of dental erosion. Further properly designed in situ or clinical studies are recommended in order to better understand the relative differences in performance of the various fluoride agents and formulations.

The Effects of Pi-Pi Stacking on the Controlled Radical Polymerization of Vinyl Aromatics

The atom transfer radical polymerization (ATRP) of styrene (St) was conducted in the presence of varying equivalence (eq) of hexafluorobenzene (HFB) and octafluorotoluene (OFT) to probe the effects of pi-pi stacking on the rate of the polymerization and on the tacticity of the resulting polystyrene (PSt). The extent of the pi-pi stacking interaction between HFB/OFT and the terminal polystyrenic phenyl group was also investigated as a function of solvent, both non-aromatic solvents (THF and hexanes) and aromatic solvents (benzene and toluene). In all cases the presence of HFB or OFT resulted in a decrease in monomer conversion indicating a reduction in the rate of the polymerization with greater retardation of the rate with increase eq of HFB or OFT (0.5 eq to 1 eq HFB/OFT compared to St). Additionally, when aromatic solvents were used instead of non-aromatic solvents the effect of the HFB/OFT on the rate was minimized, consistent with the aromatic solvent competitively interacting with the HFB/OFT. The effects of temperature and ligand strength on the ATRP of St in the presence of HFB were also probed. It was found that when using N,N,N’,N’,N’’-pentamethyldiethylenetriamine (PMDETA) as the ligand the effects of HFB at 38o were the same as at 86oC. When tris[2-(dimethylamino)ethyl]-amine (Me6TREN) was used as the ligand at 38o there was a decrease in monomer conversion similar to the analogous PMDETA reaction. When the polymerization was conducted at 86oC there was no effect on the monomer conversion with HFB present compared to when HFB was absent. To investigate the pi-pi stacking effect even further, the reverse pi-pi stacking system was observed by conducting the ATRP of pentafluorostyrene (PFSt) in the presence of varying eq of benzene and toluene, which in both cases resulted in an increase in monomer conversion compared to when benzene or toluene were absent; in summary the rate of the ATRP of PFSt increases when benzene or toluene waas present in the reaction. The pi-pi stacking interaction between the HFB/OFT and the dormant alkyl bromide of the polymer chain was verified by 1H-NMR with 1-bromoethylbenzene as the alkyl bromide. Also verified by 1H-NMR was the interaction between HFB/OFT and St and the interaction between PFSt and benzene. In all 1H-NMR spectra a perturbation in the aromatic and/or vinyl peaks was observed when the pi-pi stacking agent was present compared to when it was absent. The tacticity of the PSt formed in the presence of 1 eq of HFB was compared to the PSt formed in the absence of HFB by observing the C1 signal in their 13C-NMR spectra, but no change in shape or chemical shift of the signal was observed indicating that there was no change in tacticity.

Activation of T cells by carbamazepine and carbamazepine metabolites

BACKGROUND: T-cell-mediated hypersensitivity is a rare but serious manifestation of drug therapy. OBJECTIVES: To explore the mechanisms of drug presentation to T cells and the possibility that generation of metabolite-specific T cells may provoke cross-sensitization between drugs. METHODS: A lymphocyte transformation test was performed on 13 hypersensitive patients with carbamazepine, oxcarbazepine, and carbamazepine metabolites. Serial dilution experiments were performed to generate drug (metabolite)-specific T-cell clones to explore the structural basis of the T-cell response and mechanisms of antigen presentation. 3-Dimensional energy-minimized structures were generated by using computer modeling. The role of drug metabolism was analyzed with 1-aminobenzotriazole. RESULTS: Lymphocytes and T-cell clones proliferated with carbamazepine, oxcarbazepine, and some (carbamazepine 10,11 epoxide, 10-hydroxy carbamazepine) but not all stable carbamazepine metabolites. Structure activity studies using 29 carbamazepine (metabolite)-specific T-cell clones revealed 4 patterns of drug recognition, which could be explained by generation of preferred 3-dimensional structural conformations. T cells were stimulated by carbamazepine (metabolites) bound directly to MHC in the absence of processing. The activation threshold for T-cell proliferation varied between 5 minutes and 4 hours. 1-Aminobenzotriazole, which inhibits cytochrome P450 activity, did not prevent carbamazepine-related T-cell proliferation. Substitution of the terminal amine residue of carbamazepine with a methyl group diminished T-cell proliferation. CONCLUSION: These data show that carbamazepine and certain stable carbamazepine metabolites stimulate T cells rapidly via a direct interaction with MHC and specific T-cell receptors. CLINICAL IMPLICATIONS: Some patients with a history of carbamazepine hypersensitivity possess T cells that cross-react with oxcarbazepine, providing a rationale for cross-sensitivity between the 2 drugs.

CO2 laser-irradiation through topically applied fluoride increases acid resistance of demineralised human enamel in vitro

PURPOSE: To evaluate the effect of CO2 laser treatment through topically applied amine fluoride solution on demineralised enamel. MATERIALS AND METHODS: Sixty extracted human molar crowns were selected and cut longitudinally into half. One half was subjected to a 10-day pH-cycling procedure to create caries-like lesions, whereas the other was left non-demineralised. The following treatments were randomly assigned (one treatment per tooth, on respective non-demineralised and demineralised matched specimens): exposure to a 1% amine fluoride solution for 15 s without irradiation (group I), irradiation for 15 s with a continuous-wave CO2 laser (group II), or laser-treatment for 15 s through the amine fluoride solution applied immediately beforehand (group III). Fluoride uptake (n = 30) and acid resistance (n = 30) were determined after treatment. Enamel surface alterations after laser irradiation were monitored using scanning electron microscopy. RESULTS: In groups I and III, an increased fluoride uptake was detected (p < or = 0.05). Laser irradiation through topical fluoride resulted in an increased acid resistance of sound and demineralised enamel specimens in deeper layers (p < or = 0.05). In addition, less surface alterations were observed in SEM examination of specimens irradiated through the amine fluoride solution compared with counterparts treated with laser only. CONCLUSIONS: CO2 laser light application through an amine fluoride solution may be instrumental in enhancing acid resistance of sound and demineralised enamel.

Molecular interactions underlying the unusually high adenosine affinity of a novel Trypanosoma brucei nucleoside transporter

Trypanosoma brucei encodes a relatively high number of genes of the equilibrative nucleoside transporter (ENT) family. We report here the cloning and in-depth characterization of one T. brucei brucei ENT member, TbNT9/AT-D. This transporter was expressed in Saccharomyces cerevisiae and displayed a uniquely high affinity for adenosine (Km = 0.068 +/- 0.013 microM), as well as broader selectivity for other purine nucleosides in the low micromolar range, but was not inhibited by nucleobases or pyrimidines. This selectivity profile is consistent with the P1 transport activity observed previously in procyclic and long-slender bloodstream T. brucei, apart from the 40-fold higher affinity for adenosine than for inosine. We found that, like the previously investigated P1 activity of long/slender bloodstream trypanosomes, the 3'-hydroxy, 5'-hydroxy, N3, and N7 functional groups contribute to transporter binding. In addition, we show that the 6-position amine group of adenosine, but not the inosine 6-keto group, makes a major contribution to binding (DeltaG0 = 12 kJ/mol), explaining the different Km values of the purine nucleosides. We further found that P1 activity in procyclic and long-slender trypanosomes is pharmacologically distinct, and we identified the main gene encoding this activity in procyclic cells as NT10/AT-B. The presence of multiple P1-type nucleoside transport activities in T. brucei brucei facilitates the development of nucleoside-based treatments for African trypanosomiasis and would delay the onset of uptake-related drug resistance to such therapy. We show that both TbNT9/AT-D and NT10/AT-B transport a range of potentially therapeutic nucleoside analogs.

Electrospun chitosan nanofibers for virus removal

Electrospinning uses electrostatic forces to create nanofibers that are far smaller than conventional fiber spinning process. Nanofibers made with chitosan were created and techniques to control fibers diameter and were well developed. However, the adsorption of porcine parvovirus (PPV) was low. PPV is a small, nonenveloped virus that is difficult to remove due to its size, 18-26 nm in diameter, and its chemical stability. To improve virus adsorption, we functionalized the nanofibers with a quaternized amine, forming N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC). This was blended with additives to increase the ability to form HTCC nanofibers. The additives changed the viscosity and conductivity of the electrospinning solution. We have successfully synthesized and functionalized HTCC nanofibers that absorb PPV. HTCC blend with graphene have the ability to remove a minimum of 99% of PPV present in solution.

Photodegradation and photostabilization of weathered wood flour filled polyethylene composites

Wood plastic composites (WPCs) have gained popularity as building materials because of their usefulness in replacing solid wood in a variety of applications. These composites are promoted as being low-maintenance, high-durability products. However, it has been shown that WPCs exposed to weathering may experience a color change and/or loss in mechanical properties. An important requirement for building materials used in outdoor applications is the retention of their aesthetic qualities and mechanical properties during service life. Therefore, it is critical to understand the photodegradation mechanisms of WPCs exposed to UV radiation and to develop approaches to stabilize these composites (both unstabilized and stabilized) as well as the effect of weathering on the color fade and the retention of mechanical properties were characterized. Since different methods of manufacturing WPCs lead to different surface characteristics, which can influence weathering, the effect of manufacturing method on the photodegradation of WPCs was investigated first. Wood flour (WF) filled high-density polyethylene (HDPE) composite samples were either injection molded, extruded, or extruded and then planed. Fourier transform infrared (FTIR) spectroscopy was used to monitor the surface chemistry of the manufactured composites. The spectra showed that the surface of planed samples had more wood component than extruded and injection molded samples, respectively. After weathering, the samples were analyzed for color fade, and loss of flexural properties. The final lightness of the composites was not dependent upon the manufacturing method. However the mechanical property loss was dependent upon manufacturing method. The samples with more wood component at the surface (planed samples) experienced a larger percentage of total loss in flexural properties after weathering due to a greater effect of moisture on the samples. The change in surface chemistry of HDPE and WF/HDPE composites after weathering was studied using spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) was used to characterize the occurrence of surface oxidation whereas FTIR spectroscopy was used to monitor the development of degradation products, such as carbonyl groups and vinyl groups, and to determine changes in HDPE crystallinity. Surface oxidation occurred immediately after exposure for both the neat HDPE and WF/HDPE composites. After weathering, the surface of the WF/HDPE composites was oxidized to a greater extent than the neat HDPE after weathering. This suggests that photodegradation is exacerbated by the addition of the carbonyl functional groups of the wood fibers within the HDPE atrix during composite manufacturing. While neat HDPE may undergo cross-linking in the initial stages of accelerated weathering, the WF may physically hinder the ability of the HDPE to cross-link resulting in the potential for HDPE chain scission to dominate in the initial weathering stages of the WF/HDPE composites. To determine which photostabilizers are most effective for WF/HDPE composites, factorial experimental designes were used to determine the effects of adding two hindered amine light stabilizers, an ultraviolet absorber, and a pigment on the color made and mechanical properties of both unweathered and UV weathered samples. Both the pigment and ultraviolet absorber were more effective photostabilizers for WF/HDPE composites than hinder amine light stabilizers. The ineffectiveness of hindered amine light stabilizers in protecting WPCs against UV radiation was attribuated to the acid/base reactions occurring between the WF and hindered amine light stabilizer. The efficiency of an ultraviolet absorber and/or pigment was also examined by incorporating different concentration of an ultraviolet absorber and/or pigment into WF/HDPE composites. Color change and flexural properties were determined after accelerated UV weathering. The lightness of the composite after weathering was influenced by the concentration of both the ultraviolet absorber by masking the bleaching wood component as well as blocking UV light. Flexural MOE loss was influenced by an increase in ultraviolet absorber concentration, but increasing pigment concentration from 1 to 2% had little influence on MOE loss. However, increasing both ultraviolet absorber and pigment concentration resulted in improved strength properties over the unstabilized composites after 3000 h of weather. Finally, the change in surface chemistry due to weathering of WF/HDPE composites that were either unstabilized or stabilized with an ultraviolet absorber and/or pigment was analyzed using FTIR spectroscopy. The samples were tested for loss in modulus of elasticity, carbonyl and vinyl group formation at the surface, and change in HDPE crystallinity. It was concluded that structural changes in the samples; carbonyl group formation, terminal vinyl group formation, and crystallinity changes cannot reliably be used to predict changes in modulus of elasticity using a simple linear relationship. The effect of cross-linking, chain scission, and crystallinity changes due to ultraviolet exposure as well as the interfacial degradation due to moisture exposure are inter-related factors when weathering HDPE and WF/HDPE composites.

Bacteriorhodopsin protein hybrids for chemical and biological sensing

Bacteriorhodopsin (bR), an optoelectric protein found in Halobacterium salinarum, has the potential for use in protein hybrid sensing systems. Bacteriorhodopsin has no intrinsic sensing properties, however molecular and chemical tools permit production of bR protein hybrids with transducing and sensing properties. As a proof of concept, a maltose binding protein-bacteriorhodopsin ([MBP]-bR) hybrid was developed. It was proposed that the energy associated with target molecule binding, maltose, to the hybrid sensor protein would provide a means to directly modulate the electrical output from the MBP-bR bio-nanosensor platform. The bR protein hybrid is produced by linkage between bR (principal component of purified purple membrane [PM]) and MBP, which was produced by use of a plasmid expression vector system in Escherichia coli and purified utilizing an amylose affinity column. These proteins were chemically linked using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), which facilitates formation of an amide bond between a primary carboxylic acid and a primary amine. The presence of novel protein hybrids after chemical linkage was analyzed by SDSPAGE. Soluble proteins (MBP-only derivatives and unlinked MBP) were separated from insoluble proteins (PM derivatives and unlinked PM) using size exclusion chromatography. The putatively identified MBP-bR protein hybrid, in addition to unlinked bR, was collected. This sample was normalized for bR concentration to native PM and both were deposited onto indium tin oxide (ITO) coated glass slides by electrophoretic sedimentation. The photoresponse of both samples, activated using 100 Watt tungsten lamp at 10 cm distance, were equal at 175 mV. Testing of deposited PM with 1 mM sucrose or 1 mM maltose showed no change in the photoresponse of the xiv material, however addition of 1 mM maltose to the deposited MBP-bR linked hybrid material elicited a 57% decrease in photoresponse indicating a positive response for targeting of maltose. This chemically linked MBP-bR hybrid protein, with bacteriorhodopsin, as a photoresponsive transducing substrate, shows promise for creation of a universal sensing array by attachment of other pertinent sensing materials, in lieu of the maltose binding protein utilized. This strategy would allow significant reduction in sensor size, while increasing responsiveness and sensitivity at nano and picomolar levels.

A Novel Approach to Carbon Dioxide Capture and Storage

The novel approach to carbon capture and storage (CCS) described in this dissertation is a significant departure from the conventional approach to CCS. The novel approach uses a sodium carbonate solution to first capture CO2 from post combustion flue gas streams. The captured CO2 is then reacted with an alkaline industrial waste material, at ambient conditions, to regenerate the carbonate solution and permanently store the CO2 in the form of an added value carbonate mineral. Conventional CCS makes use of a hazardous amine solution for CO2 capture, a costly thermal regeneration stage, and the underground storage of supercritical CO2. The objective of the present dissertation was to examine each individual stage (capture and storage) of the proposed approach to CCS. Study of the capture stage found that a 2% w/w sodium carbonate solution was optimal for CO2 absorption in the present system. The 2% solution yielded the best tradeoff between the CO2 absorption rate and the CO2 absorption capacity of the solutions tested. Examination of CO2 absorption in the presence of flue gas impurities (NOx and SOx) found that carbonate solutions possess a significant advantage over amine solutions, that they could be used for multi-pollutant capture. All the NOx and SOx fed to the carbonate solution was able to be captured. Optimization studies found that it was possible to increase the absorption rate of CO2 into the carbonate solution by adding a surfactant to the solution to chemically alter the gas bubble size. The absorption rate of CO2 was increased by as much as 14%. Three coal combustion fly ash materials were chosen as the alkaline industrial waste materials to study the storage CO2 and regeneration the absorbent. X-ray diffraction analysis on reacted fly ash samples confirmed that the captured CO2 reacts with the fly ash materials to form a carbonate mineral, specifically calcite. Studies found that after a five day reaction time, 75% utilization of the waste material for CO2 storage could be achieved, while regenerating the absorbent. The regenerated absorbent exhibited a nearly identical CO2 absorption capacity and CO2 absorption rate as a fresh Na2CO3 solution.