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    Cyclic carbonates as green reactants for improving thermoplastic properties of lignocellulosic materials
    (2023) Tansatien, Rattanapon; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Larsson, Anette; Henrik-Klemens, Åke; Jonasson, Katarina
    Lignocellulosic materials are attractive raw materials for producing thermoplastics with more sustainable manufacturing. They come from a renewable source that can reduce the dependency on conventional fossil-based feedstock and has good tensile properties. However, their polymeric chains have poor mobility because of the multiple hydrogen bonds of their hydroxyl groups, which is an essential obstacle for thermoplastic processing. To improve their thermoplasticity, their hydroxyl groups can be converted by chemical modifications that introduce the side groups that can increase the flowability of their chains. In this study, unbleached softwood kraft pulp was oxyalkylated with cyclic carbonates (propylene carbonate and ethylene carbonate), acting as a reactant and medium. These two reactants create low environmental impacts because of their biodegradability and low toxicity. In addition, they are also safer compounds from their high boiling point, flash point, and vapor pressure. The influence of temperature, catalysts, and reaction time were investigated. The molecular structures, purity, and thermal properties of the modified products were also evaluated. The chemical modification with ethylene carbonate provides the highest yields and appears to be the most effective pathway to substitute hydroxyl groups with the alkyl side chains. In addition, the products from the chemical modifications with ethylene carbonate have a higher purity and are easier to separate than the products from the chemical modifications with propylene carbonate. Increasing the temperature and amount of catalyst promotes the substitutions on the hydroxyl group. Finally, the modified pulp from chemical modification with ethylene carbonate at a higher temperature and amount of catalyst has better thermal properties than the unmodified pulp. The glass-transition temperature (Tg) of the modified pulp can be detected at approximately 180 °C while the Tg of its raw material is above 220 °C, so the polymeric chains of modified pulp become more flowable.
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    In situ synthesis of gold nanorods on SiO₂-substrates
    (2023) Wilson, Sean; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Andersson, Martin; Hulander, Mats; Uusitalo, Maja
    The implantation of a medical device introduces a high risk of infection and bacterial biofilm formation on the device surface. These biomaterials-associated infections (BAI) are difficult to treat using conventional methods, such as high dosages of antibiotic treatments, as the bacteria are protected by the biofilm. A promising treatment is to modify the implant surfaces with gold nanorods, which can photothermally eradicate bacteria beneath the biofilm with heat generated from localized surface plasmon resonance (LSPR). As such there is a need to develop methods that reliably produce gold nanorods of a size that produces LSPR at wavelengths within the biological window and that stably bind the particles to the material surface homogeneously. In this thesis, a method has been developed to grow gold nanorods in situ on SiO2-glass and silicon wafers by binding gold nanoparticle seeds to surfaces using (3-Mercaptopropyl)- trimethoxysilane (MPTMS) as a linking molecule. The seeds were then grown into rods using a modified growth solution. The method has also been adapted to surface sensitive analysis to demonstrate the increased possibility to study anisotropic nanoparticles this method brings. In situ quartz crystal microbalance (QCM-D) analysis was used to study the formation of the self-assembled monolayer of MPTMS, the chemisorption of gold nanoparticle seeds, and how the growth rates of the particles vary over time, possibly due to both their increasing size as well as variations in solution concentrations. The developed method produced nanorods with a demonstrated rod yield of ~69% directly on SiO2-glass surfaces. The rods had an aspect ratio (AR) that could be customised to tune the wavelength of LSPR. The ability to tune the optical properties of the rods could allow this method to be used to grow gold nanorods for other applications, such as sensing, as well. Here the tuning was used to demonstrate the effect of silver ions within the growth solution and to produce nanorods with LSPR at the near infrared (NIR) wavelength of ~800nm in the biological window.
  • Post
    Goldfinger, Solvent extraction of gold
    (2023) Johansson, Richard; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Foreman, Mark; Foreman, Mark
    This is a project about the purification of gold at 25 ºC during recycling by solvent extraction. The solvent extraction of gold from chloride media (slightly acidic sodium chloride, choline chloride and a combination of ethylene glycol and choline chloride) by solutions of Aliquat 336 in 3,7-dimethyloctanol was investigated. The 3,7-dimethyloctanol is a semisynthetic diluent which can be obtained by simple chemical processing of a terpene (geranyl acetate) obtained from plants. The behavior of potential impurity metals such as copper, lead, palladium, and zinc, in the solvent extraction purification was assessed. An impure gold solution obtained from scrap gold was successfully purified into a pure gold solution by using a deep eutectic solvent (DES) as the stripping agent made of choline chloride and ethylene glycol at a 1:2 ratio. There is an increasing interest in making solvent extraction more environmentally friendly by using new and green solvents. Deep eutectic solvents (DESs) are a new group of greener solvents that have similar properties as ionic liquids (ILs). The solvent extraction of gold was modelled mathematically, the work included estimations of the random errors. Pitzer and SIT theory was used in the modelling and the parameters for Pitzer and SIT equations were obtained.
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    New catalysts for green BTX
    (2023) Hellgren, Oscar; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Carlsson, Per-Anders; de Reijer, Guido
    This thesis examines the impact of aluminium and gallium content in faujasite and mordenite zeolites on the conversion and selectivity of 2,5-dimethylfuran into benzene, toluene and xylene. An optimum aluminium content for faujasite was confirmed, and lies around a silicon to aluminium-ratio of 6.05. Gallium introduced by wet impregnation was shown to improve conversion and selectivity for faujasites with high aluminium content, and for mordenite. Gallium treated mordenite was found to have the highest selectivity and conversion out of all examined zeolites.
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    Functionalization of gold nanorods with antimicrobial peptides
    (2023) Asaad, Mohamed; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Andersson, Martin; Hulander, Mats
    Infections in biomedical implants can occur due to the growth of bacterial biofilms, and treating these infections becomes even more challenging due to problems such as antimicrobial resistance. Gold nanorods (NRs) provide an alternative approach to combating bacterial infections. When exposed to radiation, gold nanorods generate heat, which can be employed to eliminate bacteria. Antimicrobial peptides (AMPs) are naturally occurring peptides known for their potent ability to kill microorganisms. A combination between gold nanorods and AMPs could potentially show promising results and open up for new, safe and efficient treatment options of bacteria. The primary objective of this study was to investigate the interaction between gold nanorods and antimicrobial peptides, focusing on optimizing the attachment of these peptides to the nanorods. Two distinct types of antimicrobial peptides were employed: one with a positive charge and another one terminated with thiol groups. In the case of the positively charged antimicrobial peptide, it was observed that the removal of CTAB from the gold nanorods resulted in increased peptide attachment to the nanorods. Interestingly, it was also noted that the peptide not only bonded through thiol groups but also exhibited unfavorable attachment to the surface onto which the gold nanorods were coated, likely due to electrostatic interactions. To address this issue, two different strategies were applied. The first involved adjusting the pH of the system to induce electrostatic repulsion, while the second utilized a PEG silane polymer to block peptide attachment to the surface. Both approaches effectively reduced the amount of peptide binding to the surface. Additionally, introducing a pH of 11.5 with NaOH as the initial step in the QCMD measurement resulted in a cleaner silica surface, enhancing the attachment of various components. For the thiol-terminated antimicrobial peptides, UV-Vis analysis revealed that these peptides exclusively attached to the surface through thiol bonding. Notably, A fascinating revelation came to light when exploring the temperature at which these peptides detached from the gold nanorods. Beyond 45°C, an additional resonance peak emerged at approximately 970 nm, adding an interesting dimension to the findings.