The aim of this work is to study the interfacial properties of amphiphilic compounds at the liquid–air interface in an attempt to develop a comprehensive understanding of their orientation as well as the influence of their interaction with the solvent on the interfacial layer properties. Using Vibrational Sum Frequency Spectroscopy (VSFS) as the main tool, the molecular structure of the amphiphilic layer and the amphiphile–solvent relation can be illuminated in great detail – it is arguably the most sensitive surface spectroscopy currently available. Due to its second order nature, the VSFS technique is capable of distinguishing molecules at the interface even in the presence of a vast excess of similar molecules in the bulk.Ionic liquids (Ils) form a class of solvent which are increasingly receiving attention as ``green solvents´´. Some of these, such as ethyl ammonium nitrate (EAN), a protic IL, have the capacity to hydrogen bond extensively which is one of the important features they share with water. Since the interaction with solvent is an important consideration for self assembly and it is known that surfactant self assembly in the EAN bulk is analogous to in water, it was considered of interest to probe self assembly at EAN–air interface. To this end the interfacial structure of the pure EAN interface was probed, as was the conformation and ordering of nonionic surfactants. These studies reveal that EAN is highly ordered at the interface, exposing the ethyl moiety to the gas phase. Additionally, polarization studies have enabled the average orientation of the ethyl group to be determined. Adsorption of nonionic surfactants at the interface appears to significantly displace the EAN from the interface. The headgroup of the surfactant, a linear ethylene oxide group, appears to be highly disordered.The disorder of the linear ethylene oxide groups has led to difficulties in their surface spectroscopic fingerprinting in this and other works. In an attempt to study the interfacial behaviour of ethylene oxide and the temperature dependence of its hydration, closed loop structures of PEO attached to hydrophobic groups were also probed. This essentially locks their conformation. Such molecules are known as crown ethers and display interesting interfacial behaviour and also the ability to bind cations. The presence of even small amounts of adsorbed crown ethers at the water interface is shown to considerably perturb the water structure. The NO, CN, COC and CH vibrational modes of these compounds at the air-water interface as well as OH vibrational modes of the surface water hydrating this compound have been targeted in order to obtain molecular information about arrangement and conformation. The CH2 vibrational modes of crown ethers have been identified and found to be split due to their interaction with ether oxygen. The spectra provide evidence for the existence of a protonated crown complex moiety at the surface leading to the appearance of strongly ordered water species. The orientation of Nitrobenzo crown (NB15C5) was monitored as a function of solution concentration, by targeting the ratio of peak intensities of the CN and NO2 vibrational modes. The water of hydration has also been probed as a function of crown concentration, salt concentration, and temperature. The latter study strongly suggests that the surface can be treated as a charged interface, and that the associated ordered water decreases with increasing ionic strength of the bulkFinally, insoluble monolayers of fatty acids spread on a water surface have also been studied in an effort to further understand the relationship between molecular architecture and film structure. Fatty acid (Arachidic Acid – AA and Eicosenoic Acid – EA) monolayers are compared to investigate the effect on the monolayer structure of introducing unsaturation into the alkyl chain. For AA, at very large area per molecule, floating domains of crystalline nature exist rather than any classical gaseous phase. The measured conformational disorder in EA decreases continuously with monolayer compression and no crystalline domains are observed at low density. Addition of NaCl to the subphase does not affect the monolayer order for either of the compounds; instead, a dramatic increase in the signal of the water hydrating the headgroups is observed. The effect of introducing further unsaturations (up to three) was also studied in order to probe the resulting interfacial structure. Remarkably the double bonds appear to adopt the same orientation, irrespective of how many they are in the chain. By monitoring the vinyl CH stretch it was possible to study the film stability towards oxidative degradation and it was found that all three unsaturated species studied showed rapid degradation. The rate of degradation could be controlled by adjusting the film pressure. However, the monolayers could be stabilised by performing the experiments in an inert nitrogen atmosphere. / QC20100629

Green chemistry principles have been applied to the enhancement of two industrial chemistry problems. An industrially used reaction to form alcohols from aldehydes and ketones, the Meerwein-Ponndorf-Verley reduction, was improved by introducing a new catalyst Al(OtBu)₃. Due to the lower state of aggregation of this catalyst versus the conventional Al(OiPr)₃ catalyst, reduction rates were found to be faster in both pure iPrOH and mixed solvent systems for three model compounds: benzaldehyde, acetophenone, and a complex, chiral ketone, (S)-CMK. This allowed for the successful implementation of two important milestones; lowering the amount of catalyst needed necessary to complete the reactions (an economic benefit and lower waste) and the conversion from traditional batch reactions to continuous flow (a processing benefit) whereby reactions can be scaled-out rather than scaled-up. Another industrially important field of research that was focused on was CO₂ capture. High energy demands from current CO₂ capture methods such as aqueous amine solvents, specifically from coal-fired power plant flue gas, led to the development of non-aqueous reversible ionic liquids based on silylated amines. Structural modifications of the substitution around the silicon atom, the length of the alkyl chain bonding the silicon and amine, branching along the alkyl backbone, and investigating secondary and primary amines within this class of silylated amines were completed. These amines were reacted with CO₂ and the CO₂ capacity, the ionic liquid viscosity, reversal temperature and reaction enthalpy were all considered as a function of structure. In all cases the capacity was found to be not only greater than that of monethanolamine, an industrial standard, but higher than theoretical predictions through the formation of carbamic acid. Viscosity, reversal temperature, and reaction enthalpy were all found to be tunable through structure. These modifications gave significant insight into the necessary direction for optimization of these solvents as energy-efficient replacements of current CO₂ capture technology.

In this study, we investigated the effect of electrolyte composition, photoanode thickness, and the additions of GuSCN (guanidinium thiocyanate), NMB (N-methylbenimidazole), and SiO2 on the photovoltaic performance of DSSCs (dye sensitized solar cells). A bifacial DSSC is realized and irradiated from front and rear sides. The devices give maximum photovoltaic efficiencies for 70% PMII (1-propyl 3-ethylimidazoliumiodide)/30%(EMIB(CN)4)(1-ethyl-3-methyl-imidazolium tetracyano borate) electrolyte composition and 10 &mu / m thick photoanode coating which is considered to be the ideal coating thickness for the diffusion length of electrolyte and dye absorption. A significant increase in the photocurrent for DSSCs with optimum molarity of 0.1 M GuSCN was observed due to decreased recombination which is believed to be surface passivation effect at photoanode electrolyte interface suppressing recombination rate. Moreover, optimum NMB molarity was found to be 0.4 for maximum efficiency. Addition of SiO2 to the electrolyte both as an overlayer and dispersed particles enhanced rear side illuminated cells where dispersed particles are found to be more efficient for the front side illuminated cells due to additional electron transport properties. Best rear side illuminated cell efficiency was 3.2% compared to front side illuminated cell efficiency of 4.2% which is a promising result for future rear side dye sensitized solar cell applications where front side illumination is not possible like tandem structures and for cells working from both front and rear side illuminations.

Homogenous acid catalysts are prevalent throughout the chemical industry but all have the drawback of requiring post reaction neutralization and subsequent downstream removal of the product salt. The use of a base to neutralize the acid and the processing of the salt are ancillary to the process and the disposal of the salt is an environmental concern. The work presented here shows the use of alkylcarbonic acids, which form in situ with CO₂ pressure and neutralize on loss of CO₂ pressure rather than requiring a base. Thus CO₂ can be used to "switch" the acid on and off. The properties of alkylcarbonic acids are explored to gain understanding of the mechanisms by which they act. The acids are also used to catalyze the synthesis of α-pinene, methyl yellow, and benzyl iodide. These reactions are examples of common acid catalyzed reactions where this technology could be implemented. The second half of the work explores two other "switches". The first is using temperature to break an emulsion with a novel thermally cleavable surfactant. This technology has potential applications in a wide range of fields where surfactants are used including polymerization, oil recovery, and biosynthesis. The second is using CO₂ to liquefy a solid ionic compound to allow its use as a solvent. This would greatly increase the number of ionic species available for use in ionic liquid-CO₂ biphasic systems.

<p>Surfactants are molecules that contain a water-soluble and afat-soluble part. They have important functions in productssuch as detergents, cosmetics, pharmaceuticals and foods aswell as in many industrial processes. Surfactants are used onvery large scale, which makes it important to decrease theirimpact on the environment. This can be done by starting withnatural materials, by improving the synthetic methods and byreducing the use of limited resources such as energy andorganic solvents.</p><p>This thesis focuses on lipase-catalyzed synthesis ofsurfactants based on natural products. It also includesfunctional studies of the produced surfactants; as antioxidantsin oils, or as surfactants to solubilize pharmaceuticals.</p><p>Unsaturated fatty acid esters of ascorbic acid weresynthesized with catalysis by Candida antarctica lipase B in<i>t</i>-amyl alcohol and in ionic liquids. High yields ofascorbyl oleate were obtained in an ionic liquid that wasdesigned to improve the solubility of the fatty acid, when thereaction was performed under vacuum. Ascorbyl oleate wasamorphous and was a better antioxidant than ascorbyl palmitatein rapeseed oil.</p><p>Polyethylene glycol (PEG) stearate, PEG 12-hydroxystearateand a series of PEG 12-acyloxy-stearates were synthesized in avacuum-driven, solvent-free system using<i>C. antarctica</i>lipase B as catalyst. Critical micelleconcentration and solubilization capacity were determined forthe PEG 12-acyloxy-stearates. Their effects on living cellswere evaluated in studies of hemolysis and transepithelialelectrical resistance. Several PEG1500 12-acyloxy-stearateswere excellent solubilizers for pharmaceutical use and hadnegligible negative effects on living cells even at highconcentrations.</p><p>Enzymatic and chemo-enzymatic methods offer uniquepossibilities to synthesize surfactants of high purity. Pureand well-defined surfactants enable new applications and areimportant for the understanding of surfactantstructure-function relationships.</p>

The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers (CPs). However, the high cost and toxicity of applicable metal oxides and poor long term stability of CPs paved the way to alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and CPs could significantly reduce the cost of supercapacitor electrodes compared to metal oxides. Recent developments in carbon allotropes, such as carbon nanotubes (CNTs) and especially graphene (G), have found applications in supercapacitors because of their enhanced double layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties. The main objective of the research presented in this dissertation is to increase the energy density of supercapacitors by the development of nanocomposite materials composed of graphene and different CPs, such as: (a) polyaniline derivatives (polyaniline (PANI), methoxy (-OCH3) aniline (POA) and methyl (-CH3) aniline (POT), (b) poly(3-4 ethylenedioxythiophene) (PEDOT) and (c) polypyrrole (PPy). The research was carried out in two phases, namely, (i) the development and performance evaluation of G-CP (graphene in conducting polymers) electrodes for supercapacitors, and (ii) the fabrication and testing of the coin cell supercapacitors with G-CP electrodes. In the first phase, the synthesis of different morphological structures of CPs as well as their composites with graphene was carried out, and the synthesized nanostructures were characterized by different physical, chemical and thermal characterization techniques, such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, BET surface area pore size distribution analysis and Thermogravimetric Analysis (TGA). The electrochemical properties of G-CP nanocomposite-based supercapacitors were investigated using Cyclic Voltammetry (CV), galvanostatic charge-discharge and Electrochemical Impedance Spectroscopy (EIS) techniques in different electrolytes, such as acidic (2M H2SO4 and HCl), organic ( 0.2 M LiClO4) and ionic liquid (1M BMIM-PF6) electrolytes. A comparative study was carried out to investigate the capacitive properties of G-PANI derivatives for supercapacitor applications. The methyl substituted polyaniline with graphene as a nanocomposite (G-POT) exhibited a better capacitance (425 F/g) than the G-PANI or the G-POA nanocomposite due to the electron donating group of G-POT. The relaxation time constants of 0.6, 2.5, and 5s for the G-POT, G-PANI and G-POA nanocomposite-based supercapacitors were calculated from the complex model by using the experimental EIS data. The specific capacitances of two-electrode system supercapacitor cells were estimated as 425, 400, 380, 305 and 267 F/g for G-POT, G-PANI, G-POA, G-PEDOT and G-PPy, respectively. The improvements in specific capacitance were observed due to the increased surface area with mesoporous nanocomposite structures (5~10 nm pore size distribution) and the pseudocapacitance effect due to the redox properties of the CPs. Further, the operating voltage of G-CP supercapacitors was increased to 3.5 V by employing an ionic liquid electrolyte, compared to 1.5 V operating voltage when aqueous electrolytes were used. On top of the gain in the operating voltage, the graphene nano-filler of the nanocomposite prevented the degradation of the CPs in the long term charging and discharging processes. In the second phase, after studying the material's chemistry and capacitive properties in three-electrode and two-electrode configuration-based basic electrochemical test cells, coin cell type supercapacitors were fabricated using G-CP nanocomposite electrodes to validate the tested G-CPs as devices. The fabrication process was optimized for the applied force and the number of spacers in crimping the two electrodes together. The pseudocapacitance and double layer capacitance values were extracted by fitting experimental EIS data to a proposed equivalent circuit, and the pseudocapacitive effect was found to be higher with G-PANI derivative nanocomposites than with the other studied G-CP nanocomposites due to the multiple redox states of G-PANI derivatives. The increased specific capacitance, voltage and small relaxation time constants of the G-CPs paved the way for the fabrication of safe, stable and high energy density supercapacitors.

The separation of the expensive catalysts from the solvent and reaction products remains one of the major disadvantages of homogeneous catalytic reactions, which are otherwise advantageous because of their high activity, tuneable selectivity and ease of study. Ideally, the homogeneous reactions would be carried out in continuous flow mode with the catalyst remaining in the reactor at all times, whilst the substrates and products flow over the catalyst. The system we have been studying is one where the catalyst is dissolved in a thin film of an ionic liquid, and this is supported within the pores of a microporous silica. This supported ionic liquid phase (SILP) catalyst is then placed in a tubular flow reactor, similar to that used for heterogeneous reactions. The raw materials are then injected into the rig, pass through the reactor and the products and the raw materials that have not reacted are collected at the other end of the rig. Supercritical CO₂ is used to transport the raw materials and products along the catalyst bed, allowing a continuous flow mode with low leaching for both the catalyst and the ionic liquid. We have applied this procedure first to alkene metathesis catalysed by a ruthenium complex that has been especially designed to dissolve in 1-butyl-3-methyimidazolium triflamide (BMIM NTf₂), which was used as ionic liquid. Activity is observed for the ring closing metathesis of diethyl 2,2-diallylmalonate, but the catalyst is not stable, only allowing about 300 turnovers. This instability is attributed to the formation of Ru=CH₂ moieties, which dimerise to an inactive species. More success is achieved with internal alkenes such as 2-octene and especially methyl oleate. Self metathesis of methyl oleate continues for >10.000 turnovers over 10 h, with only small decreases in activity. The cross metathesis of methyl oleate with dimethyl maleate has also been studied. Cross metathesis dominates in the early stages of the reaction but the cross metathesis products diminish with time. Surprisingly, the catalyst does not deactivate since self metathesis of methyl oleate continues. The phase behaviour of the reaction was monitored and gave us an insight into the reasons for this change in selectivity. Methoxycarbonylation reactions in continuous flow proved to be a much more difficult process than the previous metathesis reactions. Higher catalyst loading was needed to reduce the reaction times. The first continuous flow reactions showed conversion predominantly, if not exclusive, of 1-octene isomerised products. The presence of ionic liquid (IL) in the SILP system was essential, otherwise the catalyst leached out of the reactor very quickly. Batch reactions showed that none of the studied parameters (absence of presence of either BMIM NTf₂, OMIM NTf₂, silica or CO₂) had any influence on the reaction, but when observing the results it was noticed that the reactions that gave the best results were performed in a close range of pressures between 55 and 70 bar, indicating that the reaction might be pressure dependent. Further continuous flow reactions in that range of pressures gave the best conversions to methoxycarbonylation products. Unfortunately, at these pressures and without CO₂ the reaction took place in a liquid phase and thus substantial IL and catalyst leaching was observed, causing a decrease in conversion and making the reaction not feasible under continuous flow conditions. Nevertheless, the catalyst system composed of Pd, 1,2-bis(di-tert-butylphosphinomethyl)benzene (DTBPMB) ligand and acid showed an excellent linear selectivity, usually higher than 90%, both in batch and continuous flow reactions. Hydrogenation reactions of dimethyl itaconate (DMI) and dibutyl itaconate (DBI) using Rh-MeDuPhos showed excellent activity and enantioselestivity in a batch mode. In a continuous flow mode IL leaching caused a decrease of the enantioselectivity. The best results were obtained when CO₂ was not present. On the other hand, the absence of CO₂ implied that the reaction was performed in a liquid phase and therefore abundant IL leaching was observed along with a decrease in the enantioselectivity. A study of the reaction behaviour when using CO₂ in its different phases (liquid, gas and supercritical) was carried out. Under supercritical conditions IL leaching was avoided but conversion was not observed. When using CO₂ in its liquid phase some conversion was observed and full conversion occurred in its gas phase, but abundant IL leaching caused a decrease in the enantioselectivity. Better results were obtained by immobilising a Rh-MeDuPhos catalyst onto alumina via heteropoly acids. The effect of pressure, H₂ flow and substrate flow were studied and the stability of the reaction in the long term was examined under optimal conditions. More than 12,900 TONs were achieved after 4 days of continuous reaction, with conversions higher than 90% during the 3 first days and e.e. higher than 99% during the 2 first days.

No description available.

The use of lignocellulosic materials to replace fossil resources for the industrial production of fuels, chemicals, and materials is increasing. The carbohydrate composition of lignocellulose (i.e. cellulose and hemicellulose) is an abundant source of sugars. However, due to the feedstock recalcitrance, rigid and compact structure of plant cell walls, access to polysaccharides is hindered and release of fermentable sugars has become a bottle-neck. Thus, to overcome the recalcitrant barriers, thermochemical pretreatment with an acid catalyst is usually employed for the physical or chemical disruption of plant cell wall. After pretreatment, enzymatic hydrolysis is the preferred option to produce sugars that can be further converted into liquid fuels (e.g. ethanol) via fermentation by microbial biocatalysts. However, during acid pretreatment, several inhibitory compounds namely furfural, 5-hydroxymethyl furfural, phenols, and aliphatic acids are released from the lignocellulose components. The presence of these compounds can greatly effect both enzymatic hydrolysis and microbial fermentation. For instance, when Avicel cellulose and acid treated spruce wood hydrolysate were mixed, 63% decrease in the enzymatic hydrolysis efficiency was observed compared to when Avicel was hydrolyzed in aqueous citrate buffer. In addition, the acid hydrolysates were essentially non-fermentable. Therefore, the associated problems of lignocellulose conversion can be addressed either by using feedstocks that are less recalcitrant or by developing efficient pretreatment techniques that do not cause formation of inhibitory byproducts and simultaneously give high sugar yields. A variety of lignocellulose materials including woody substrates (spruce, pine, and birch), agricultural residues (sugarcane bagasse and reed canary grass), bark (pine bark), and transgenic aspens were evaluated for their saccharification potential. Apparently, woody substrates were more recalcitrant than the rest of the species and bark was essentially amorphous. However, the saccharification efficiency of these substrates varied based on the pretreatment method used. For instance, untreated reed canary grass was more recalcitrant than woody materials whereas the acid treated reed canary grass gave a higher sugar yield (64%) than the woody substrates (max 34%). Genetic modification of plants was beneficial, since under similar pretreatment and enzymatic hydrolysis conditions, up to 28% higher sugar production was achieved from the transgenic plants compare to the wild type. As an alternative to the commonly used acid catalysed pretreatments (prior to enzymatic hydrolysis) lignocellulose materials were treated with four ionic liquid solvents (ILs): two switchable ILs (SILs) -SO2DBUMEASIL and CO2DBUMEASIL, and two other ILs [Amim][HCO2] and [AMMorp][OAc]. viii After enzymatic hydrolysis of IL treated substrates, a maximum amount of glucan to glucose conversion of between 75% and 97% and a maximum total sugar yields of between 71% and 94% were obtained. When using acid pretreatment these values varied between 13-77% for glucan to glucose conversion and 26-83% for total sugar yield. For woody substrates, the hemicellulose recovery (max 92%) was higher for the IL treated substrates than compared to acid treated samples. However, in case of reed canary grass and pine bark the hemicellulose recovery (90% and 88%, respectively) was significantly higher for the acid treated substrates than the IL treated samples. To overcome the inhibitory problems associated with the lignocellulose hydrolysates, three chemical conditioning methods were used 1. detoxification with ferrous sulfate (FeSO4) and hydrogen peroxide (H2O2) 2. application of reducing agents (sulfite, dithionite, or dithiothreitol) and 3. treatment with alkali: Ca(OH)2, NaOH, and NH4OH. The concentrations of inhibitory compounds were significantly lower after treatments with FeSO4 and H2O2 or alkali. Using reducing agents did not cause any decrease in the concentration of inhibitors, but detoxification of spruce acid hydrolysates resulted in up to 54% improvement of the hydrolysis efficiency (in terms of sugar release) compared to untreated samples. On the other hand, application of detoxification procedures to the aqueous buffer resulted in up to 39% decrease in hydrolysis efficiency, thus confirming that the positive effect of detoxification was due to the chemical alteration of inhibitory compounds. In addition, the fermentability of detoxified hydrolysates were investigated using the yeast Saccharomyces cerevisiae. The detoxified hydrolysates were readily fermented to ethanol yielding a maximum ethanol concentration of 8.3 g/l while the undetoxified hydrolysates were basically non-fermentable.

The first chapter of this thesis describes the motivation behind using room temperature ionic liquids (RTILs) in gas sensor research and reviews current applications of RTILs in various sensors. The second chapter describes electrochemical polymerization of aniline in room temperature 1-butyl-3-methylimmidazolium ionic liquids without addition of any acid. It is shown that the polymerization of aniline in BMI(BF4) does require small but controlled amounts of water whereas the polymerization in BMI(PF6) and in BMI(TF2N) does not require any water addition. The third chapter describes the construction of reference electrodes for RTIL applications that have a known and reproducible potential versus the ferrocene/ ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag+ couple type, or of the second kind, based on Ag/AgCl in M+Cl-. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized. The fourth chapter describes the electrochemical preparation and spectral analysis of gold clusters by adding gold atoms one-by-one through polyaniline s ability to form a strong complex with chloroaurate at the protonated imine sites. Our results confirm that both the amount and the size of gold clusters affects the properties of the composite material. The fifth chapter describes the development and characterization of a CHEMFET sensing layer based on a composite of CSA-doped polyaniline (PANI), and the room temperature ionic liquid BMI(TF2N) for the sensing of ammonia gas. The work function responses of the cast films with and without IL are analyzed by step-wise changes of ammonia gas concentration from 0.5 to 694 ppm in air as a function of the mole fraction of IL to PANI. The PANI CSA/BMI(TF2N) layers shows enhanced sensitivities, lower detection limit and shorter response times. The final chapter describes the preparation and characterization of field-effect transistors with mixed ionic-electronic conductors that have been created by varying the ratio of room temperature ionic liquid and emeraldine salt of polyaniline. Transistor with high electronic conductivity (32mol% ES-PANI) and Au gate contact exhibited theoretical behavior of an IGFET; whereas, the purely ionic gate behaved irreproducibly, indicating that a capacitive divider has been formed in the gate.