Thesis (Ph.D.(Chemistry)) -- University of Limpopo, 2020 / The interest on the use of proton exchange membrane (PEM) fuel cells for vehicle application has increase due to its efficiency, high power density and rapid start up. The on-board reforming process is used to generate hydrogen; however, this process simultaneously produces 1% CO which poisons Pt-based anode catalyst. Previous studies have shown that supported Pd-based catalysts have very good stability on preferential oxidation (PROX) of CO, but these catalysts suffer from lower selectivity. Metal oxides such as Co3O4 and CeO2 are known to have high oxygen vacancy which promotes CO oxidation. Furthermore, the pre-treatment of the catalysts by hydrazine as well as the addition of MnOx species have been shown to improve the surface properties of metal/metal oxides catalysts. The study envisages that the modification of PROX catalysts will improve the CO conversion and its selectivity while maintaining higher stability. In this work, as-prepared (Co3O4) and hydrazine treated cobalt (Co3O4(H)) based catalysts were prepared by precipitation method and investigated at temperature range of 40-220 oC for preferential oxidation (PROX) of CO in excess hydrogen. The FTIR and XPS data of hydrazine treated Co3O4 does not show peak ratio differences, indicating that usual amounts of Co3+ and Co2+ were formed. An improved surface reducibility with smaller crystallite size was noted on Co3O4(H) catalyst, which indicate some surface transformation. Interestingly, the in-situ treatment of standalone Co3O4(H) decreased the maximum CO conversion temperature (T100%) from 160 oC (over Co3O4) to 100 oC. The Co3O4(H) catalyst showed good stability, with approximately 85% CO conversion at 100 oC for 21 h, as compared to fast deactivation of the Co3O4 catalyst. However, the Co3O4(H) catalyst was unstable in both CO2 and the moisture environment. Based on the spent hydrazine treated (CoO(H)) cobalt catalyst, the high PROX is associated with the formation of Co3+ species as confirmed by XRD, XPS, and TPR data. The Pd species was incorporated on different Co3O4 by improved wet impregnation method and this has improved the surface area of the overall catalysts. However, the presence of Pd species on Co3O4(H) catalyst decreased the CO conversion due to formation of moisture. Although, the Pd on Co3O4(H) had lower activity, the catalyst showed better stability under both moisture and CO2 conditions at 100 oC for 21 h. vi The 2wt.% metal oxides (MnO2, CeO2, Cr3O4, TiO2, MgO) on cobalt, and Pd on CeO2- Co3O4 and MnO2-Co3O4 were prepared by co-precipitation method and the structural composition was confirmed by XRD, FTIR, XPS and TPR data. Although, 2wt.%MnO2 on Co3O4(H) showed higher activity at 80 oC, both MnO2 and CeO2 improved the activity of Co3O4(H) at 100 oC. The higher activity of MnO2 is attributed to the higher surface area of the composite catalyst, in relation to ceria composite catalyst. Although the MnO2 species transformed the structure of Co3O4 by lowering the oxidation state to Co2+, the spent catalyst showed transformation from Co2+ to Co3+ during PROX, as confirmed by TPR data. Studies on the effects of CeO2 loading on Co3O4 catalysts, showed an optimum activity over 2wt.%CeO2-Co3O4 as compared to other ceria loadings (i.e., 3, 5, 8, 10, 15, 30wt.%CeO2). However, upon addition of 0.5wt.%Pd species on 2wt.%CeO2- Co3O4(H) composite, the activity of the catalyst decreased slightly at 100 oC, which could be due to a decreased surface area. Although its activity is lower, the catalyst has shown good stability in dry, moisture and CO2 conditions at 100 oC for 21 h. In addition, studies were also undertaken on the effect of MnO2 concentration on Co3O4 catalysts. The data shows that 7wt.%MnO2 species improved the activity of Co3O4 catalyst at 60 oC, however, the catalyst could not improve the activities at higher temperatures. This low activity is associated with a decrease in surface area as concentration increases. The presence of 0.5wt.%Pd species on 7wt.%MnO2-Co3O4 increased the activity at 60 and 80 oC, which could be due to reduction of Co3+ to Co2+ in the presence of Pd, as confirmed by XPS data. The catalyst has shown good stability in dry, moisture, and CO2 conditions at 100 oC for 21 h. The hydrazine treated cobalt-based catalysts in the presence of palladium and manganese oxide is the promising catalysts for proton exchange membrane fuel cells technology. / National Research Foundation (NRF) , Faculty of Science and Agriculture University of Limpopo and School of Physical and Mineral Sciences

Yes / Carbon monoxide (CO) is both a substance hazardous to health and a side product of a number of industrial processes, such as methanol steam reforming and large-scale oxidation reactions. The separation of CO from nitrogen (N2) in industrial processes is considered to be difficult because of the similarities of their electronic structures, sizes, and physicochemical properties (e.g., boiling points). Carbon monoxide is also a major poison in fuel cells because of its adsorption onto the active sites of the catalysts. It is therefore of the utmost economic importance to discover new materials that enable effective CO capture and release under mild conditions. However, methods to specifically absorb and easily release CO in the presence of contaminants, such as water, nitrogen, carbon dioxide, and oxygen, at ambient temperature are not available. Here, we report the simple and versatile fabrication of a new class of hybrid materials that allows capture and release of carbon monoxide under mild conditions. We found that carborane-containing metal complexes encapsulated in networks made of poly(dimethylsiloxane) react with CO, even when immersed in water, leading to dramatic color and infrared signature changes. Furthermore, we found that the CO can be easily released from the materials by simply dipping the networks into an organic solvent for less than 1 min, at ambient temperature and pressure, which not only offers a straightforward recycling method, but also a new method for the “on-demand” release of carbon monoxide. We illustrated the utilization of the on-demand release of CO from the networks by carrying out a carbonylation reaction on an electron-deficient metal complex that led to the formation of the CO-adduct, with concomitant recycling of the gel. We anticipate that our sponge-like materials and scalable methodology will open up new avenues for the storage, transport, and controlled release of CO, the silent killer and a major industrial poison. / The Royal Society, The Romanian Ministry of Education and Research, The University of Bradford, European Regional Development Fund of the European Union / Research Development Fund Publication Prize Award winner.

No description available.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A tunable narrow-bandwidth vacuum ultra violet laser source was developed and characterised. Two-photon resonant four-wave sum-frequency mixing of two pulsed dye laser beams in magnesium vapour was used to generate the VUV laser light. A heat pipe oven with a concentric design was incorporated to provide a magnesium vapour column of around 30 cm in length with a sufficiently stable temperature and appropriate vapour pressure for efficient VUV production. This is a longer nonlinear medium length than previously produced in our laboratory using a crossed heat pipe oven. The longer medium facilitated the production of VUV laser light of higher intensity than was previously obtainable. High resolution laser induced fluorescence spectra of carbon monoxide in a supersonic gas jet was recorded using the tunable VUV laser light produced in the crossed heat pipe oven. Experimental parameters were optimised and adjusted for the selective detection of the forbidden singlet-triplet transitions which typically have longer lifetimes than singlet-singlet transitions. Transitions from the X¹Σ⁺(v = 0) ground state to the e³Σ⁻( v = 5) triplet state were recorded, and accurate wavelength for the spectral lines were determined. Laboratory wavelengths for these lines have not been measured previously. Accurate wavelength for the weak forbidden spectral lines of CO are important in astrophysical applications, for example determining column densities of interstellar gas clouds. / AFRIKAANSE OPSOMMING: 'n Afstembare smal bandwydte vakuum ultraviolet laser bron is ontwikkel en gekarakteriseer. Twee-foton resonante vier-golf som-frekwensie vermenging van twee gepulseerde kleurstoflaserbundels in 'n magnesium damp is gebruik om die VUV laser lig te produseer. 'n Hittepyp oond met 'n konsentriese ontwerp is in gebruik geneem om a magnesium damp kollom van ongeveer 30 cm in lengte te voorsien waarvan die temperatuur voldoende stabiel is en die dampdruk toepaslik is vir effektiewe VUV produksie. Dit is 'n langer nie-liniêre medium as wat in die verlede deur 'n kruis-hittepyp oond voorsien is. Die langer medium het dit moontlik gemaak om VUV laser lig van hoër intensiteit te produseer as wat tot dusver bereikbaar was. Hoë resolusie laser geinduseerde fluoresensie spektra van koolstof monoksied in a supersoniese gasstraal is opgeneem met die hulp van die afstembare VUV laser lig geproduseer in die kruis-hittepyp oond. Eksperimentele parameters is geoptimeer en verstel vir die selektiewe waarneming van die verbode singlet-triplet oorgange wat tipies langer leeftye besit in vergelyking met singlet-singlet oorgange. Oorgange vanaf die X¹Σ⁺(v = 0) grond toestand na die e³Σ⁻( v = 5) triplet toestand is opgeneem en akkurate golflengtes vir die spektrale lyne is bepaal. Laboratorium golflengtes het tot dusver nie bestaan vir hierdie lyne nie. Akkurate golflengtes vir die swak verbode spektrale lyne van CO het belangrike toepassings in astrofisika soos die bepaling van die kollom digtheid van interstellêre gas wolke.

Thesis (PhD (Physics))--University of Stellenbosch, 2006. / Carbon monoxide (CO) is a diatomic molecule of particular interest in astrophysics, due to its high abundance in interstellar space. The Fourth Positive System A1Π−X1Σ+ of CO is an important feature in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum in astronomical observations, especially in high-resolution spectra recorded by satellite-based spectrographs. The interpretation of these astronomically detected spectra requires accurate laboratory wavelengths to serve as rest wavelengths and to resolve possible Doppler-shifts. Such rest wavelengths are known for the 12C16O, 13C16O and 12C18O isotopomers for all astronomically observed spectral lines of the Fourth Positive System. The only laboratory wavelengths currently available for the Fourth Positive System of the 12C17O isotopomer have been determined in a previous work carried out in our laboratory for the vibronic band A1Π(v0 = 3)−X1Σ+(v00 = 0). The present study continues this work for the other vibronic bands which have been detected astronomically, namely A1Π(v0 = 2 − 5)−X1Σ+(v00 = 0). The A1Π(v0 = 0− 1)−X1Σ+(v00 = 0) vibronic bands have also been investigated due to their probability for future astronomical detection. Rotationally-resolved spectra of these six vibronic bands were obtained by selective rovibronic laser excitation, and subsequent detection of the undispersed fluorescence, observed as a function of the excitation wavelength in the VUV. A tunable narrow-bandwidth VUV laser source is used for excitation, and the CO gas sample is introduced by supersonic expansion. Flow-cooling in the supersonic expansion to rotational temperatures roughly corresponding to temperatures in the interstellar medium simplifies and aids the spectral analysis of the spectral lines of interest. The cold conditions in the supersonic expansion facilitates a high sensitivity for detection of the low-J lines, and allows the detection of rare isotopomers of CO in natural abundance. The experimental setup has been improved in the present study by the addition of a vacuum monochromator, facilitating an improved characterisation of the VUV source. Furthermore, a number of experimental conditions have been optimised for the detection of rare CO isotopomers, significantly increasing the signals of these lines in the spectra. The combination of this increase in sensitivity and the addition of the vacuum monochromator to the experimental setup, allowed the simultaneous detection of absorption spectra with the fluorescence spectra as an additional source of information in spectral analysis. The increased sensitivity also contributed to the detection of a large number of spectral lines of interest, with some additional lines identified in the previously studied vibronic band. Spectral lines of 12C16O, 13C16O, 12C18O and 12C17O were detected in each vibronic band, allowing accurate calibration of the spectra. A total of 29 new lines of 12C17O were recorded in the six vibronic bands investigated. Additionally, 10 new singlet-triplet lines of 12C16O were recorded in the wavelength regions investigated. The new wavelengths of 12C17O have been applied to calculate consistent heliocentric velocities of a gas cloud toward the star X Persei, obtained from spectra of the different CO isotopomers taken by the Hubble space telescope.

Kiekvienasis metais vis didėjant autotransporto kiekiui keliuose, didėja ir jų į aplinką išmetamų teršalų kiekiai. Todėl galime numanyti, jog Lietuvoje autotransportui išaugus 2,5 karto per paskutinį dešimtmetį tiek kartų išaugo ir į aplinką išmetamų kenksmingų deginių kiekiai, kurie labiausiai jaučiami didžiuosiuose miestuose ar miesteliuose. Greta Kelmės miesto yra keli dideli cheminės oro taršos šaltiniai: kelias Ryga-Kaliningradas, Kelmė – Raseiniai ir pagrindinė miesto sankryža, kur susidaro didžiausi teršalų kiekiai. Šiais keliais nuolat juda intensyvūs autotransporto srautai, kurių dalis patenka į Kelmės miestą. Todėl buvo atliktas autotransporto srautų įtakos Kelmės miesto aplinkos orui tyrimas: ištirti autotransporto srautai Kelmėje; išmatuota anglies monoksido kiekiai ore; teoriškai apskaičiuoti autotransporto amžiaus ir jo eksploatacinių parametrų įtaka deginių kiekiui ir jų sudėčiai; eksperimentiškai ištirta autotransporto cheminė tarša. / The volume of vehicle traffic, growing every year, increases the emissions of toxic substances and pollutes the environment. Consequently, the road traffic in Lithuania has increased by 2.5 times over the last decade. Big cities and small towns have noticed the effect of harmful exhaust emissions on the environment and people health most. A large number of chemical sources of air pollution are located near Kelme city: road Riga – Kaliningrad, Kelme – Raseiniai and the main city crossroads, which produces the most significant contaminants. These roads are constantly moving the intense flows of motor vehicles, the part of which falls within the town of Kelme. Therefore the aim of our research was to study the impact of the road traffic on the air quality in Kelme city, to investigate the traffic flows, to measure the concentration of carbon monoxide in the air, theoretically calculate the impact of vehicle age and its operating parameters on the exhaust emissions and its composition. The experimental research revealed the chemical pollution of the vehicles .

Household fuel pollution from the use of low quality biomass fuels is considered as a risk factor for respiratory tract infections (RTI) in women and children. Inhalation of fuel-derived pulmonary toxins (e.g. particulate matter (PM2.5μm) , and carbon monoxide (CO) can harm the lungs of young children, due to their under-developed immune defences. In Bangladesh acute respiratory infections (ARI) are the leading cause of child mortality (< 5 years of age). This thesis aimed to examine the relationship between RTI and household fuel pollution exposure using measured pollution data and medical diagnoses. During an 18-month longitudinal health intervention in northern Bangladesh households (n=408) were interviewed (3 times) on cooking/fuel-use practices and child health. Anthropometric data (height/weight) and finger-prick blood samples for analysis of immune status (c-reactive protein, alpha-1-acidglycoprotein (AGP) and albumin) were collected (n=321 < 5 years of age). All unwell children (62.4%) were medically examined. Household pollution levels (particulate matter (PM2.5μm) and carbon monoxide (CO) were monitored for a 24-hour period (n=61). Moderate/ severe RTI was common (24.8%) (youngest child only n=213). Poor child growth (stunted: 43.8%, underweight=66.7%, wasted: 38.4%) and immunity were detected. 98% of the households used inefficient chimneyless mud stoves and low quality biomass fuels (wood, golden, dung). The measured indoor pollution levels exceeded the WHO safety thresholds (PM2.5 μm range: 85 to 3020 μg/m³ CO range: 0-16 ppm) (PM2.5 μm>25 μm/m³, CO>9ppm). Longitudinal multivariate GLM showed that cooking practices were associated with child immune status: haemoglobin levels (F= 1.555, p=NS) were significantly associated with Bihari ethnicity and a fixed stove use (F=3.718 and F=3.716, p<0.05 respectively). Elevated log₁₀-AGP levels were found (F=4.371, p<0.05) in Saidpur in households using a fixed stove (F=4.123, F=3.780, p<0.05). The patterns in child growth z-scores were due to age only (stunting: F=7.413, p<0.01, underweight F=5.787, p<0.05). Interestingly, poorer change score for weight-for-age (F=34.893, p<0.01) was associated with low age and more frequent cooking (F=6.441 and, F=6.553, p<0.05 respectively). Logistic regression (healthy vs. RTI) identified the presence of child by the stove during cooking as the sole risk factor for RTI (absent OR= 0.257, 95% CI: 0.097 - 0.676, p<0.01). Indoor cooking and the use of a fixed stove were associated with low SES. Education may help to reduce behaviours associated with high household fuel pollution exposure via the introduction of simple healthy cooking practices.

Prior work in our lab has indicated that reduced Hydroxocobalamin (B12r) can be added to human blood and is able to convert carbon monoxide (CO) into carbon dioxide. This has great potential as a direct antidote to mitigate the toxic effects of CO poisoning which is a public health risk. In the first part of our work, we use highly specific wavelengths of light and Raman spectroscopy to study changes in Carboxyhemoglobin (COHb) between blood treated with oxygen and blood treated with oxygen and B12r in a flowing circuit of blood. Using Raman spectroscopy, we found that the addition of B12r hastens the conversion of the COHb Raman signals to Oxyhemoglobin (HbO2) Raman signals. In addition, the B12r absorbance of light energy within the Raman spectrum is an exploitable relationship that can be used to measure B12r presence in the blood. In part two of our study we focused on the neurobehavioral testing of rats injured by CO exposure, however, we were not able to find statistical differences in the behavioral tests between exposed and unexposed rats.

Based upon experimental evidence from the 1970’s we proposed that a reduced form of hydroxocobalamin should be capable of producing carbon dioxide (CO2) from carbon monoxide (CO) in blood, and that this conversion should be detectable. Using resonance raman spectroscopy we demonstrated that a mixture of hydroxocobalamin and ascorbic acid could create the reduced form of hydroxocobalamin. We used a closed-loop circulation system with a hollow-fiber membrane oxygenator to produce carboxyhemoglobin. Using sensitive gas monitoring equipment to the gas-out port of the oxygenator we analyzed the CO and CO2 concentrations coming from the oxygenator. The mixture of hydroxocobalamin and ascorbic acid caused a 5-fold increase in the CO2 concentration of the gas-out flow, in comparison to baseline and negative controls. These findings offer initial support for the potential use of a mixture of hydroxocobalamin and ascorbic acid as an injectable antidote for carbon monoxide poisoning.

La recherche de nouvelles molécules pour combattre Pseudomonas.aeruginosa est d'une grande importance. L'utilisation des antibiotiques a spectre large a grandement accru la résistance de P.aeruginosa aux antibiotiques. Malgré cette situation, aucune nouvelle drogue active sur P.aeruginosa n'a été introduite en pratique clinique durant les 2 dernières décennies. Le monoxyde de carbone (CO) pourrait agir comme un inhibiteur efficace de la chaîne respiratoire de P.aeruginosa mais l'utilisation pratique de ce gaz comme molécule antibactérienne est gênée par sa toxicité et les difficultés de manipulation. Une avancée fondamentale récente dans le domaine de la recherche sur le CO a été la découverte des « carbon monoxide releasing molecules » (CO-RMs), qui servent de transporteur et délivre des quantités contrôlées de CO aux systèmes biologiques.Nous montrons ici que les CO-RMs possèdent des propriétés antibactériennes contre P.aeruginosa. Cet effet antibactérien des CO-RMs à lieu à des concentrations non toxiques pour les cellules eucaryotes et passe par une interaction du CO libérer par le transporteur avec la chaîne respiratoire bactérienne. Nous présentons des résultats in vivo montrant que les CO-RMs diminuent l'inoculum bactérien et augmentent la survie des souris après une bactériémie à P.aeruginosa. La comparaison de 4 CO-RMs ayant différente structures chimiques suggère que la précence d'un métal de transition joue un rôle important dans l'activité antibactérienne des CO-RMs. Une autre découverte importante présentée dans ce travail est l'inhibition de l'activité antibactérienne de certain CO-RMs par les molécules contenant des résidus thiols. Cette découverte limite la possibilité d'utiliser les CO-RMs concernés comme des agents anti-infectieux.En considérant les résultats présentés dans ce travail, l'inhibition de la chaîne respiratoire pourrait être considérée comme un nouveau mécanisme prometteur pour la recherche de nouveaux agents pharmaceutique pour combattre les infections à P.aeruginosa. / The search of new molecules to fight Pseudomonas.aeruginosa is of paramount importance. The use of broad spectrum antibiotics has greatly increased the antibiotic resistance of P.aeruginosa. In spite of this situation, no new drug against P.aeruginosa has been successfully introduced into the clinic in the past 2 decades. Carbon monoxide (CO) could act as an effective inhibitor of the respiratory chain in P. aeruginosa but the practical use of this gas as an antibacterial molecule is hampered by its toxicity and difficulty to manipulate. A recent fundamental development in the field of CO research has been the discovery of carbon monoxide-releasing molecules (CO-RMs), which serve as carriers for the delivery of controlled amounts of CO in biological systems.Here, we show that CO-RMs possesse bactericidal properties against P.aeruginosa. This antimicrobial effect of CO-RMs occurs at non toxic concentrations for eukaryotic cells and is mediated by an interaction of CO liberated by the carrier with bacterial respiratory chain. We present in vivo results showing that CO-RMs decrease bacterial inoculum and increase survival in mice following P.aeruginosa bacteraemia. A comparison of 4 CO-RMs with different chemical structures suggests that the presence of a transition metal center plays an important role in the antibacterial activity of CO-RMs. Another important finding presented in this work is the inhibition of the antibacterial activity of some CO-RMs by thiol containing molecules. This finding could deserve the possibility to use concerning CO-RMs as anti-infective agent.Considering results presented in this work, inhibition of respiratory chain could be considered as a promising new mechanism for the research in new pharmaceutical agent to fight P.aeruginosa infections.