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This thesis explores the synthesis, characterization, and electrochemical behavior of nanocomposites composed of cobalt (Co) and molybdenum (Mo) deposited onto graphene oxide (GO), COOH-functionalized multi-walled carbon nanotubes (CNT-COOH), and blends of these two graphitic nanomaterials. The study aims to investigate the structural, morphological, and electrocatalytic properties of these nanocomposites synthesized via a hydrothermal method. Using a combination of analytical techniques including Raman Spectroscopy, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray Photoelectron Spectroscopy (XPS), Cyclic Voltammetry (CV), Chronoamperometry, and UV-vis Spectroscopy, the nanocomposite structures were comprehensively characterized. SEM imaging demonstrated differential deposition of CoMo particles, demonstrating higher affinity and deposition on CNT-COOH compared to GO. EDX and XPS findings confirmed successful deposition of Co and Mo sulfides and oxides on both supports. According to XPS data, cobalt sulfides, molybdenum dioxide, and molybdenum disulfide were the dominant species synthesized in CoMo-CNT-COOH and CoMo-GO, whereas the prevalent species in CoMo-CNT-COOH-GO were cobalt and molybdenum sulfides. Electrochemical analyses, particularly CV tests, unveiled unique electro-oxidative activity of CoMo-CNT-COOH for Methyl Orange (MO) analyte at -0.4 V. CoMo-CNT-COOH exhibited approximately 68% optimum electrooxidation of MO after 5 hours for 100 mL solution initially made of 30 ppm MO and 0.5 molar sulfuric acid, indicating potential for environmental remediation applications. / Thesis / Master of Chemical Engineering (MChE)

There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the cracked oxide theory was proposed by Tu in 1994. The current work has investigated the effect of using an electrochemically formed oxide and both a molybdate conversion coating and a tungstate conversion coating on tin whisker growth from Sn-Cu electrodeposits on Cu, and compared it with that from a native air-formed oxide. X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of coating parameters on the thickness and composition of the oxide film. The XPS studies show that the oxide film formed using either of the conversion coating baths was significantly thicker than that produced from the potassium bicarbonate-potassium carbonate bath. Initial observations suggest that both the tungstate-based conversion coatings and the molybdate-based conversion coatings significantly reduced whisker growth by over 80 %, compared with a native air-formed oxide, and provide improved whisker mitigation compared with the electrochemically formed oxides. The current work has also investigated the potential of using a dual-layer system, comprised of both an electrochemically formed oxide bottom layer and an acrylic conformal coating top layer, for the mitigation of tin whisker growth. The electrochemically formed oxide used in the dual-layer system was produced at 2 V vs. Ag/AgCl while passing a charge of 60 mC cm-2 and the thickness of the conformal coating was aimed to be between ~5 μm to ~6 μm. This thickness was chosen to enable the study of whisker growth on a shorter time scale and to study the effect the electrochemically formed oxide had when used in conjunction. Initial observations showed that the dual-layer system provided improved whisker mitigation compared with both the electrochemically formed oxides and acrylic conformal coatings when used singularly. As part of the self-healing work, nanocapsules filled with the reactive agent were needed to be synthesised and the compatibility of them with different solvents needed to be studied. Capsules filled with the reactive agent were successfully synthesised, however, it was found that the capsules agglomerated and the size of the capsules, in some instances, were too large to be incorporated into a thin conformal coating. Regardless, the capsules were still analysed to check the compatibility with different solvents, to identify a suitable conformal coating mixture that would not dissolve the polymer shell of the capsules. It was observed that the capsules were stable in three out of the five solvents that were analysed, them being isopropanol (IPA), butanone and methylcyclohexane.

Dopamine is a neurotransmitter found in central nerve system which has a vital role for human health. Dopamine oxidation in body is an important issue since it may form reactive metabolites which can be toxic to the cell. Surface-enhanced Raman scattering (SERS) is currently recognized as one of the most sensitive spectroscopic tools, which can be exploited for ultrasensitive chemical and biological detection, addition to providing structural information on the systems of interest. SERS of dopamine displays three strong bands at 1269, 1331 and 1479 cm-1. These bands are the signature of dopamine molecule. The most intense band at 1479 cm-1 is contributed mainly from stretching of the carbon-carbon bond to which the oxygens are attached. A bidentate silver-dopamine complex or in general bidentate metal-dopamine complex formation is required for the SERS detection of dopamine and other catecholamines. In other words, for acquiring the characteristic dopamine SERS signature, both of the catechol oxygens should take a part in the adsorption of dopamine to the silver metal surface which is used as a SERS substrate. Therefore, the reactivity of different oxidation forms of dopamine for the formation of bidentate silver-dopamine complex was investigated by obtaining their SERS spectra and following the characteristic C-C ring vibration at 1479 cm-1. Dopamine oxidation was carried out electrochemically, utilizing platinum and silver electrodes as working electrode. Oxidation products formed were identified with UV-vis Spectrometer. Also, silver metal ions were used to oxidize dopamine, leading to formation silver nanoparticles. Dopamine functionalized silver nanoparticles were characterized by Scanning Electron Microscope, Transmission Electron Microscope, UV-vis Spectrometer. Surface- enhanced Raman spectra of polydopamine on the surface of synthesized silver nanoparticles and the electrodeposited dopamine on the porous surface of silver electrode were also obtained.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第17962号 / 工博第3810号 / 新制||工||1583(附属図書館) / 30792 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 吉田 潤一, 教授 杉野目 道紀, 教授 松原 誠二郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Per- and polyfluoroalkyl substances (PFAS) are a rising topic in the field of contaminated sites around the world, with destruction of these being an area in dire need of innovation. Previous experiments of destructive character have been proven efficient using boron doped diamond electrodes (BDD) in small scale electrochemical cells. Further need for experimentation on actual site conditions is needed to further evaluate the use of this method, as well as research on alternative electrode materials to reduce the cost of remediation.  In this study, four cells containing contaminated soil were used: one with BDD electrodes, one with iron electrodes and two control cells. The iron electrodes were used to investigate if a less costly electrode material could achieve any degree of PFAS degradation. For the experiment a soil from a previous firefighting training site where firefighting foam containing high amounts of PFAS (620                     g/kg soil concentration) was used. During the first phase of the experiment a constant flow of deionized water was added to the cells containing the soil, and porewater was sampled at the in- and outflow along with the soil porewater, on a weekly basis, to evaluate the distribution of PFAS to provide information about possible degradation taking place. The extent of degradation was not quantified. However, due to differences in the molecular composition of the analysed PFAS a trend where short-chain PFAS increase throughout the experiment in the BDD cell indicated that short-chain PFAS were generated, which is an expected by-product in electrochemical oxidation of PFAS. No short-chain PFAS generation was seen in the iron electrode cell, nor was there a high amount present in the control cell leachate.  Further, leaching of PFAS was more efficient in the control cells, while PFAS in the BDD and iron electrode cell were retained or leaching was slowed down, most likely due to the electrode interaction with PFAS in porewater.Additionally a second phase where water flow through was halted and the cells were run in a batch mode was conducted to see PFAS degradation in stagnant conditions over time. In the stagnant cell in the second phase, only low PFAS concentrations in porewater were recorded while no degradation was established.  Further, fluoride analysis recorded F- concentrations in the range of    M, where the limit of detection was   M, which limited the confirmation of PFAS mineralisation in soil.  From this study insight of the difficulties with soil treatment of PFAS using electrokinetic method was highlighted, with sampling being a key factor in the accuracy of the result. For a more accurate establishment of the degradation experiments in a closed cell, with more extensive sampling throughout the entire column would be necessary. This is needed to generate a clearer picture of changes in PFAS concentration in the soil from the presumed degradation, coupled with a mass balance to provide the fate of PFAS in this type of setup.

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