[dipl] Kemian tekniikan korkeakoulu / CHEM

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  • Comparison of carbon, energy and CO2 efficiency of plastic recycling routes
    (2024-09-30 ) Le, Yen Nhi Kelly
    School of Chemical Engineering | Master's thesis
    Currently only 9 % of the global plastic waste is recycled and nearly all of it is processed through mechanical recycling. Mechanical recycling is the most advanced and efficient recycling route, but it has its limitations concerning for example feed-stock sensitivity and mechanical property deterioration. As the plastic waste and emission amounts increases it is inevitable to introduce other recycling routes to complement the mechanical recycling for increasing waste recycling rates and further the global decarbonisation. Therefore, the objective of this thesis was to increase the knowledge and to recognise the principal differences between the emerging plastics recycling technologies in terms of carbon yield, energy efficiency and direct CO2 emissions. The chosen plastics recycling routes were mechanical recycling, pyrolysis, gasification, carbon capture via methanol synthesis to Methanol-to-Olefins (MTO) and carbon capture via syngas to Fisher-Tropsch-to-Olefins (FTO). Mechanical recycling acted as a reference case. The plastic waste recycling routes were examined using a model created in this thesis, which predicted carbon, energy, and CO2 efficiencies based on the input. The model included two to four different feedstocks for each technology route. The results showed that in carbon yield carbon capture routes MTO and FTO performed with the most optimal carbon recycling rates of 66 % and 52 %, respectively. Gasification route had the least optimal carbon yield with a result of 36 %. In terms of energy balance, gasification stood out with a negative energy demand in other words released energy in the form of heat and carbon capture routes required a considerable amount of energy compared to mechanical recycling. As far as direct emissions are concerned pyrolysis emitted the most direct CO2 emissions among the compared routes. However, this was mainly due to the reason that it utilized fossil-based fuels the most. Based on the results there was not a one clear winner among the compared technologies since every technology route had its own strengths and weaknesses that requires further development.
  • Applying the circular business index to assess organizational circularity – A case study in the manufacturing industry
    (2025-09-25) Vesterlund, Moa
    School of Chemical Engineering | Master's thesis
    Linear resource extracting business practices are causing negative environmental impact, such as depletion of natural resources and ecosystem degradation. By shifting towards a more circular economy, organizations can generate economic growth while supporting sustainable development. Hence, circular economy is seen as a solution to mitigate climate change and support business practices. However, despite the interest among organizations to adopt circular practices, they often fail to turn the ambitions in into concrete actions. To support the transition, circularity measurement is needed to set a baselines, tack progress, and build awareness within organizations. The measurement methods available today are often complex and resource-intensive, requiring detailed data to assess the circular activity. The main objective of this study was to explores the Circular Business Index (CBI) as a practical method for assessing circularity in a manufacturing context. Through a case study of a Finnish abrasive manufacturer, the research applies CBI to evaluate the company’s circular maturity and activity across 8 R-strategies. Data was generated thought semi-structured interviews and analyzed through the assessment criteria of the CBI method. The analysis showed that efficiency-oriented strategies such as Reduce and Redesign are relatively well integrated in the case company. Transformative strategies like Rethink and Regenerate, however, are limited in integration. Additionally, an barriers to adopt circular principles was identified, with focus on limited targets, performance measurement, and resources. Apart from measuring circular activity, CBI works as a learning and communication tool, which can increase awareness of circular economy and support discussion. The findings of the thesis suggest that CBI is a useful starting point for organizations that are beginning their circular transition. Nevertheless, CBI should be accompanied with more technical tools, such as life cycle assessment, to evaluate perspectives outside the scope of the R-strategies. This research contributes to CE measurement literature by showing that CBI can act both as a measurement method and as a tool for organizational change.
  • Extractives removal in oxygen delignification stage
    (2025-09-29) Lempinen, Mery
    School of Chemical Engineering | Master's thesis
    Wood extractives are low molecular weight compounds that can accumulate during the kraft pulping process and deposit on machinery, causing unscheduled shutdowns. New ways of removing them at earlier stage are urgently needed to prevent their subsequent transformation into other compounds. Although extractives can be dissolved using chemicals, their behavior during oxygen delignification remains largely unknown. The goal of this master’s thesis was to reduce extractives content of eucalyptus kraft pulp using chemical additives, without disrupting the oxygen delignification performance. The chemicals studied were 1-octanol, anisole, 1,2-dimethoxybenzene, β-cyclodextrin and hydrogen peroxide. For each treated pulp, brightness, viscosity, kappa number, and hexenuronic acid content were determined before and after oxygen delignification. The research question was whether these chemicals can alter extractives’ interaction mechanism with unbleached pulp, so the extractives can be more physically liberated or chemically transformed to more soluble-form during oxygen delignification stage meanwhile keeping satisfactory results on pulp quality. Extractives yields were obtained using a Soxhlet extractor with three solvents: dichloromethane (DCM), acetone and water. The additives that gave the most promising extractives yield reductions, were further selected for optimized tests. Additionally, samples were analysed with gas chromatography-mass spectrometry, from which spectrum revealed individual compounds of extractives and their relative amounts. The results demonstrate that the addition of 0.5 w/w % 1,2-dimethoxybenzene into the oxygen delignification stage decreases the DCM extractives 36 % compared with pulp collected from reference O-stage, 31 % reduction was achieved for 0.5 w/w % hydrogen peroxide. Additionally, the pulp qualities correspond to the reference level. Removing extractives during the oxygen delignification stage would improve process efficiency, enhance pulp quality and reduce the need of bleaching chemicals. A lower extractive content would slow down their deposition on machinery. Further research of the filtrates would help confirm the reactivity of dissolved compounds, and more precise concentration optimization of the additives would prove their effectiveness.
  • Liquid-liquid phase separation of aggregation induced emitters and double-stranded DNA
    (2025-09-25) Rodriguez, Maria
    School of Chemical Engineering | Master's thesis
    Coacervates are droplet-like structures that form through liquid-liquid phase separation. This phenomenon is driven by multiple weak interactions between molecules or within a single molecule, such as electrostatic interactions, hydrogen bonding and hydrophobic effects. Coacervates are relevant in understanding natural biological processes and they may have played a crucial role in the origin of life. This thesis studied the ability of a family of aggregation induced emission dyes (AIEgens) to act as a co-coacervation agent for double-stranded DNA. Aggregation induced emission is a photophysical phenomenon, where non-emissive luminogens experience enhanced fluorescence upon aggregation. This behaviour is attributed to the restriction of intramolecular motions, which inhibits non-radiative pathways. The combination of AIE and coacervates creates fluorescent phase separated and systems, useful in biosensing and therapeutic delivery. The focus of this thesis was a family AIE dyes, each having the same core structure with varying carbon side chain lengths. Out of all the dyes, C6 possessed the right qualities for undergoing LLPS. It was able to act as a co-coacervation agent for double-stranded DNA but also undergo LLPS by itself. Aside from the structure of the dye, balancing the charges of double stranded DNA and C6, was also a crucial component in the system, achieved by adding NaCl. The addition of NaCl drove phase separation by screening excessive electrostatic repulsions. In the presence of double stranded DNA, coacervates were observed at C6 concentrations of 200 and 500 µM, across NaCl concentrations of 100, 500 and 1000 mM. The coacervation zone of C6 alone was very narrow compared to its dsDNA-containing counterpart, only forming coacervates at 500 µM in 1000 mM NaCl. However, when NaCl concentration exceeded the threshold of both systems, the coacervates transitioned into solid aggregates, which was observed in samples containing 2500 mM of NaCl. Lastly, kinetic studies revealed that C6 coacervates remained phase separated for only 25-50 minutes before gradually aggregating. Meanwhile C6-dsDNA coacervates experienced improved stability, maintaining phase separated state up until 3 hours. Overall, the key to successful LLPS was achieving a perfect balance between the hydrophobic and hydrophilic qualities of the AIEgen, as well as optimizing the strength and type of intermolecular interactions involved. LLPS of the dyes was studied using optical and fluorescence microscopy, as well as spectroscopy assays.
  • Anode slime behaviour in high impurity copper electrorefining
    (2025-09-10) Liljanko, Henna
    School of Chemical Engineering | Master's thesis
    As the use of secondary raw materials is increasing in copper production, more impurities are present in copper anodes. During electrorefining these impurities are released from the copper anode and form a by-product called anode slime. Anode slime that forms on the anode surface can cause anode passivation and contamination of copper cathodes. As the impurity levels of Cu anodes increase, more anode slime is generated, which can lead to operational problems (e.g. passivation & short-circuits) and degradation of copper cathode quality. The aim of this thesis was to investigate the possibility of electrorefining highly impure Cu anodes (<90 wt.% Cu) in typical electrorefining conditions, and to study the adherence of anode slimes in high-impurity anodes to the anode surface. The composition of the investigated Cu anode was studied with SEM-EDS. The electrorefining experiments were conducted in laboratory-scale with upwards and downwards facing anodes to evaluate the adherence of anode slimes, and to differentiate the adhering and non-adhering slime species, which were characterized with SEM-EDS. The investigations were conducted with an electrolyte composition of 40 g/L Cu2+, 15 g/L Ni2+, 180 g/L H2SO4 and 60 mg/L Cl- in temperatures of 55, 60 and 65 °C, and with current densities of 200 and 300 A/m2. Results indicate that it is possible to refine highly impure Cu anodes (<90 wt.% Cu) without immediate passivation using conventional process parameters, and the laboratory passivation times (2-42 h) were within a range (2-21 h) that has been reported previously with more conventional anodes (>98 wt.% Cu). The longest electrolysis duration was achieved in temperature of 65 °C and current density of 200 A/m2 where the time until onset of passivation was 42 hours. Characterization of adherent and non-adherent anode slime suggest that oxide phases (e.g. Cu-Ni-Fe-O, Cu-Ag-As-S-O, SiO2) detach easily from the anode surface. Additionally, it was observed that the main cause of anode passivation was the precipitation of CuSO₄ and (Cu,Ni)SO₄ on the anode surface as these phases occurred in all anode slime samples.
  • Biomolecular click chemistry for sitespecific conjugation and immobilization of oligonucleotides and monoclonal nanobodies
    (2025-09-19) Tikka, Mariina
    School of Chemical Engineering | Master's thesis
    Nanobody-oligonucleotide conjugates offer significant potential for imaging, therapeutics and diagnostic applications given their specificity, selectivity and small size. One especially promising application is in immunosensors, which combine high specificity and ease of use. Currently, the usage of immunosensors in commercial applications has been limited, since their performance is critically dependent on the orientation, stability, and density of immobilized sensor molecules. The use of nanobody-oligonucleotide conjugates presents a potential solution to these limitations. In this work, a recombinant protein–DNA oligonucleotide conjugation strategy was developed using SpyCatcher/Tag click chemistry for covalent ligation, coupled with DNA hybridization to enable site-specific immobilization of the conjugate to sensor surface. High yield and efficient purification of the fusion protein was achieved, and effective conjugate formation was observed with SpyCatcher/Tag. Specific surface immobilization of the conjugates was confirmed in fluorescencebased assays. These results establish that modular nanobody–oligonucleotide conjugates can be synthesized using biomolecular click chemistry. Furthermore, the retention of nanobody binding functionality upon immobilization supports the potential of this system for scalable and customizable use in multiplexed diagnostic platforms.
  • Passivating layer optimization in graphene field-effect transistors: Analysis of atomic layer deposited dielectrics
    (2025-09-18) Virta, Anni
    School of Chemical Engineering | Master's thesis
    Graphene field-effect transistors (GFETs) combine exceptional sensitivity, high carrier mobility, and ambipolar conductivity, making them attractive for advanced biosensing applications. Yet, their performance is strongly affected by adsorbates and interfacial defects, contributing to unintentional doping, hysteresis, instability, and device-to-device variability. The objective of this study was to investigate different dielectric passivation strategies to suppress such effects and identify an optimal encapsulation strategy. Thermal atomic layer deposition (ALD), remote plasma-enhanced atomic layer deposition (PE-ALD), and e-beam evaporation were studied alongside metal seeding and thermal annealing surface treatments to improve ALD nucleation. Electrical characterization was performed to evaluate the Dirac voltage distribution, carrier mobility, hysteresis, and ageing, complemented by structural analysis of remote PE-ALD nucleation. Thermal ALD with a thin metal seeding layer provided the most reliable electrical performance, with a narrow Dirac point distribution near charge neutrality, reduced hysteresis, and uniform nucleation. Post-deposition annealing restored the as-deposited electrical performance of environmentally aged devices, shifting the Dirac voltages back toward charge neutrality. All remote PE-ALD processes resulted in electrically non-functional devices, confirming plasma-induced graphene degradation, since morphological uniformity alone was insufficient to ensure electrical integrity. In contrast, the e-beam evaporated dielectric induced strong p-type doping, limiting its present compatibility with high-performance GFET encapsulation. Overall, this study confirmed thermal ALD with suitable surface preparation as a robust encapsulation method that could enable more stable GFET integration into biosensing platforms.
  • Extensible biocomposite fibers from recombinant spider silk like proteins and 2D MXene nanoflakes
    (2025-09-24) Mylly, Mariel
    School of Chemical Engineering | Master's thesis
    Spider silk-based materials provide exceptional mechanical performance, especially their unique combination of strength and elasticity, which makes them highly attractive for wearable textiles. Recombinant spider silk-like proteins can be produced in various hosts and spun into fibers with excellent mechanical properties (Gosline et al., 1999). MXenes are two-dimensional metal nitrides and carbides with high electrical conductivity, making them suitable material for electronic devices. Their chemical composition includes a functional group, enabling combination of MXenes with various biomolecules (Gogotsi & Huang, 2021). To exploit the excellent properties of both materials, this thesis aimed to explore a method to produce composite fibers from Recombinant silk-like protein ADF-3 and MXene with chemical composition of Ti3C2Tx, and characterize their mechanical, chemical and electrical properties. Tensile tests revealed an extensibility up to 387 %, strength up to 15.2 MPa and toughness up to 39.4 MJm-3 for composite fiber. The corresponding values for pure silk were 14.7 %, 5.0 MPa and 0.83 MJm-3, respectively, indicating a significant improvement with MXene incorporation. The extensibility was significantly enhanced compared to previously reported values, whereas strength and toughness remained moderate. Secondary structure analysis further indicated an enhanced -sheet formation in the presence of MXene. However, the electrical performance remained limited, likely due to low MXene content and small effective cross-sectional area of thin fibers and films. This work demonstrates a promising approach for incorporating MXene into protein spinning dopes, revealing notable improvements in mechanical behaviour of composite fibers. However, further optimization is required to fully reveal the electrical properties of MXene, whereas this work provides a valuable foundation for further research. Continuous spinning methods, such as wet spinning could provide more presice process control and therefore ensure the consistent quality fibers. Additionally, adjustment of MXene concentration is required for achieving electrical conductivity required for wearable electronics.
  • Engineering the properties and stability of PECVD silicon dioxide thin films for MEMS
    (2025-09-17) Haapanen, Maisa
    School of Chemical Engineering | Master's thesis
    Silicon dioxide (SiO2) thin films are extensively used in microelectromechanical systems (MEMS), both for structural purposes in the devices and as temporary layers during fabrication. The desired properties of the SiO2 thin film strongly depend on the purpose. This thesis was conducted for Murata Electronics Oy, and it sought for strategies to tailor the properties of silane- (SiH4) and tetraethyl orthosilicate- (TEOS) based plasma-enhanced chemical vapour deposited (PECVD) SiO2 thin films with PECVD process parameters and post-deposition treatments. Multivariate designs-of-experiment (DOE), constructed with statistical strategies, revealed the main parameters for tailoring the etch rate, residual stress, refractive index, surface roughness, thickness uniformity, and deposition rate. The results act as guidelines for designing SiO2 thin films for MEMS products and fabrication flows, and developing the PECVD process output to match the design. Comparison between SiH4- and TEOS-based films showed that slightly lower wet etch rates, minimum 2.1 times the etch rate of thermal oxide, were obtained with TEOS-based films, while minimum etch rates of SiH4-based films were 3.1 times the etch rate of thermal oxide. This indicates suitability of TEOS for structural parts in MEMS. As expected from previous literature, TEOS-based films showed approximately one order of magnitude lower surface roughnesses, Rq as low as 0.4 nm, than SiH4-based films. This favours TEOS for applications requiring smoothness, such as wafer level bonding, whereas SiH4-based films may be a better choice for structural parts in proximity to moving components, to prevent sticking. TEOS-based films showed linear correlations between the refractive index, wet etch rate, and residual stress of the films, making it possible to use refractive index as a fast monitor for film density. Changes in residual stresses over time showed that the stability in ambient clean-room conditions varied between the films. Thermal annealing at 1000 °C and a plasma treatment of TEOS-based films improved the stability of the films.
  • Structure-property relationships in modified wood laminates: effects of delignifica-tion, densification, and polymer impregnation
    (2025-09-04) Peltonen, Ilari
    School of Chemical Engineering | Master's thesis
    In recent years, several studies have shown the advantageous effects of delignification and densification on wood properties. Structure-retaining delignification can be utilized to selectively remove matrix components while still preserving the aligned cellulose architecture of native wood, which can be harnessed for its high mechanical properties and potential for functionalization. When combined with densification, delignified wood has been reported to exhibit exceptional mechanical performance, but water-induced dimensional instability remains a significant drawback. In order to address these challenges related to moisture susceptibility, recent research has explored combining delignification, densification, and resin impregnation for the development of strong and dimensionally stable wood composites. While formaldehyde-based resins have been commonly used for this purpose, they present significant health and environmental concerns. Furthermore, delignification and impregnation of bulk wood are time-consuming processes, which limits their scalability and uniformity of results. The objective of this thesis was to address these challenges by using spruce and birch veneers as substrates for the production of wood-based composite laminates. A process that combined alkaline sulphite delignification, methyl methacrylate (MMA) im-pregnation, in situ radical polymerisation, hot-pressing, and lamination was investigated. The mechanical performance of the composites was characterized by three-point bending, and dimensional stability was assessed by conditioning under humid conditions. The results revealed a species-dependent delignification efficiency of the alkaline sul-phite treatment, with birch samples reaching significantly higher delignification weight loss percentage than spruce samples. For both wood species, the process was success-fully used to produce composites that exhibited higher density, improved mechanical performance, and better dimensional stability compared to non-modified counterparts. Nevertheless, variability in final properties was observed, which was attributed to in-consistencies in polymer impregnation and retention during hot pressing.
  • Polyolefins in the emerging European hydrogen infrastructure: Overview of applications and Monte Carlo simulation of future demand
    (2025-08-15) Hämynen, Jussu
    School of Chemical Engineering | Master's thesis
    The transition from fossil fuel-based energy system to a renewable energy system has been widely discussed in Europe. Creating a hydrogen economy is one possible way to make this transition. However, because fossil-based fuels and chemicals are currently cheaper than renewable-made alternatives, a market-based transition is only possible with regional or global policies. There is no singular research on the material demands for a European hydrogen transport network. This thesis investigated the different applications of polyolefins in this context. Based on the results of the literature review, the potential applications were identified and a hydrogen transport system and its polyolefin demands were modeled and simulated using the Monte Carlo method for the 2025--2050 time period. For applications with the highest demand potentials, the results were brought into greater context with additional studies on the development of the global hydrogen market. This contextualization provided additional future scenarios with greater accuracy for polyolefin demand development than the Monte Carlo simulation. The applications with the highest polyolefin demand potentials were three-layer coated pipes in the European Hydrogen Backbone with a total annual demand potential of 4-13 kt/a depending mainly on the total length of the built backbone pipeline and its build rate. The other application with the highest potential was flexible composite pipes with a total annual demand potential of up to a total of 29 kt/a, depending mainly on total annual hydrogen demand and the number and length of backbone pipeline connections of hydrogen producers and demanders.
  • Emulsion polymerization of binders for sustainable fire retardant coatings
    (2025-08-20) Häkkinen, Ville
    School of Chemical Engineering | Master's thesis
    Conventional halogenated fire retardants are associated with toxicity, environmental persistence, and bioaccumulation, prompting the development of sustainable alternatives. This thesis investigates the synthesis and optimization of acrylic binders for fire retardant coatings through emulsion polymerization, with a focus on their compatibility with bio-based fire retardant additives. This work explores how synthesis parameters and emulsifier systems influence binder properties and their interaction with tannin, a bio-based fire retardant additive. Batch and semi-continuous emulsion polymerization were employed to synthesize poly(methyl methacrylate-\textit{co}-butyl acrylate) latexes. Two emulsifier systems were compared: a conventional surfactant blend(SDS+Brij\textsuperscript{\textregistered} S10) and a surfmer-based system (Emulsogen\textsuperscript{\textregistered} CPA 100 XS and CPN 100 XS). The chemical composition of the prepared copolymers were analyzed with proton nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The molecular weights of the prepared copolymers were determined via static light scattering and the particle size distribution of the latex particles was determined with dynamic light scattering. The glass transition temperature of the synthesized binders was determined using differential scanning calorimetry. The results of this study demonstrate that semi-continuous emulsion polymerization, particularly with controlled monomer and initiator feeding, allows precise compositional control, great monomer-to-polymer conversion, and uniform particle size distribution compared to batch processes. The influence of monomer feed rate, initiator feed rate, and emulsifier concentration on molecular weight, particle size, polydispersity, and thermal properties was systematically examined. Compatibility tests with tannin-based fire retardants revealed that surfmer-stabilized latexes exhibited greater stability with tannin compared to conventional surfactant systems, highlighting their potential in sustainable fire retardant binder formulations. The findings of this thesis work establish a foundation for the development of environmentally benign binder systems for modern fire retardant coatings.
  • Development of a camera-based imaging system for nucleation detection in crystallization and its comparison with focused beam reflectance measurement
    (2025-09-29) Kurki, Joni
    School of Chemical Engineering | Master's thesis
    Crystallization is a complex and important process in chemical production, and reliable monitoring of nucleation is essential for process understanding and control. Traditional tools such as focused beam reflectance measurement (FBRM) provide valuable particle information but are costly, probe-based, and susceptible to fouling. Bulk video imaging (BVI) has recently emerged as a low-cost, non-invasive alternative that monitors turbidity changes in crystallizing solutions using standard digital cameras. In this study, a processing pipeline using bulk video imaging was developed to validate the bulk video imaging technique on crystallization by using phytosterols as a model compound. The study simultaneously developed the image processing pipeline and algorithms for nucleation detection and tested across a variety of crystallization schemes, including different solvent systems, feedstock purities, and cooling rates. Camera-based measurements were collected alongside FBRM data to enable direct comparison. The results demonstrate that BVI is a robust and reliable method for detecting nucleation, often identifying the onset earlier than FBRM. In several cases, FBRM data were compromised by probe fouling or produced misleading results, whereas BVI consistently provided interpretable turbidity signals throughout the experiment. In addition to nucleation detection, BVI was also able to capture information about fouling tendencies, providing additional information for monitoring the crystallization. Overall, this work establishes BVI as a practical, low-cost alternative for crystallization monitoring, capable of providing robust nucleation detection while also delivering complementary process information beyond that obtainable from conventional probe-based tools.
  • Moire ferroelectricity in twisted hBN with machine learning potentials
    (2025-08-15) Stenbrink, Nils Henrik Samuli
    School of Chemical Engineering | Master's thesis
    This thesis is a study on the properties of twisted bilayer hexagonal boron nitride by computational methods. The methods consists of both density functional theory (DFT) and machine learning (ML) potential. We focus on developing the ML potential in order to study larger structures that aren’t available or are computationally too expensive to be studied with DFT. We concentrate on relaxation, atomic displacement during relaxation, phonon dispersion relations as well as local density of states (LDOS). First a functional ML potential was trained for this system, comparing it’s results with DFT calculations. We also computed phonon dispersion relations, which were used as a secondary performance test. When the performance of the ML potential was satisfactory, we relaxed twisted hBN systems with varying twist angles, calculated both the in-plane and out-of-plane atomic displacements during relaxation. The average and atom-wise interlayer distance was also calculated. The phonon dispersion relations were also used to gain valuable information about the twisted systems. We studied them in order to gain information about the stability of the system as well as finding evidence for phase transitions. Lastly, we computed LDOS of 3 twisted systems and an AA stacked structure for comparison. The results seemed to indicate that there is some force which gave rise to the final atomic positions in the relaxed structure. While the results did not conclusively prove the polarization or ferroelectricity, it did imply that those could be the reason for the results.
  • Light-controlled dissipative self-assembly systems of gold nanoclusters
    (2025-09-28) Chiapponi, Valentina
    School of Chemical Engineering | Master's thesis
    Nature has the extraordinary ability to operate far from thermodynamic equilibrium and self-assembling smaller building blocks into complex structures through continuous energy consumption. Scientists refer to this process as dissipative self-assembly (DSA), which remains a central focus of current research due to its potential for creating adaptive and responsive materials. While light-controlled DSA systems have been developed for gold nanoparticles, their translation to gold nanoclusters (AuNCs) remains largely unexplored. Nanoclusters are small aggregates consisting of a few to hundreds of gold atom, with diameter of only a few nanometers. Due to their size, they exhibit molecular-like behavior and distinctive chemical, optical and electronical properties, including strong photoluminescence (PL) and biocompatibility. These characteristics make them promising candidates for many biomedical applications. The aim of this thesis was to establish a light-controlled DSA system of thiolated AuNCs, mediated by merocyanine-based photoacids. This can be a way to enhance PL through aggregation-induced emission (AIE), potentially improving the performances of the NCs. AuNCs stabilized with cysteine (Cys), glutathione (GSH), mercaptohexanoic acid (MHA), and dihydrolipoic acid (LA) were synthesized and characterized using UV-Vis spectroscopy, PL spectroscopy and X-ray photoelectron spectroscopy. These AuNCs were then mixed with the photoacid (PA) and subjected to repeated light/dark cycles. The transmission electron microscopy images showed that AuMHA and AuGSH, which were already aggregated, remained unchanged upon PA activation, while AuCys and AuLA exhibited reversible self-assembly. In particular, light exposure induced aggregation of AuCys and dispersion of initially aggregated AuLA. Although, there was no clear evidence of enhanced PL via AIE, the establishment of DSA systems with AuNCs opens new pathways for the development of adaptive nanomaterials for bioimaging and drug delivery.
  • Techno-economic assessment of the chemical recycling for plastic waste
    (2025-09-29) Amin, Umer
    School of Chemical Engineering | Master's thesis
    The amount of municipal plastic waste increases globally. Only ten percent of all the plastic produced is recycled, while the rest goes to landfills, incinerators, or the natural environment. Advanced chemical recycling methods, such as pyrolysis, offer innovative technology for handling plastic waste, particularly for plastics that are not suitable for mechanical recycling. This thesis presents a comprehensive investigation into the chemical recycling of plastic waste, focusing on various recycling technologies and utilizing process simulation in Aspen Plus software. A techno-economic evaluation was performed on two different pyrolysis configurations. In the first scenario, flash uses simple separation technology to yield a variety of outputs, including light and heavy oils, waxes, and increased gas byproducts, offering operational flexibility for diverse end uses. The second scenario, fractional distillation, aims to maximize the production of higher-quality oil fractions suitable for fuels through complex separation, but produces a higher amount of solid char and gases. Fractional distillation, with higher investment requirements, is best suited for projects that prioritize the recovery of high-quality fuel. The economic assessment of the two pyrolysis scenarios indicates that flash separation (Scenario II) generates a good quantity of pyrolysis products, while needing less capital investment, making it a more adaptable and cost-efficient choice. This approach typically yields a faster return on investment and is flexible to changing operational scales. Fractional distillation (Scenario II), although requiring greater capital and generating more solid residue, excels at producing a higher quality liquid fuel, leading to greater profitability over an extended period. Scenario I (flash separation) stands out for its efficient production of varied product streams, reduced investment needs, and adaptability to different operational scales. Although Scenario II (fractional distillation) offers increased liquid oil recovery and remains a technically sound option, its higher associated costs and increased solid byproduct generation make Scenario I generally more favorable in terms of practical implementation.
  • Hydrocarbon dissociation on metal surfaces
    (2025-09-29) Jafari, Maryam
    School of Chemical Engineering | Master's thesis
    Hydrogen, due to its efficiency and producing water by burning, is a promising candidate as energy carrier. However traditional production methods are energy-intensive and produce significant amount of carbon dioxide. As using catalytic decomposition of light hydrocarbons offers a lower-emission alternative and produce solid carbon, it appears to be a promising method. To better understand the mechanism of this method, stepwise hydrogen dissociation of ethane and carbon-carbon coupling was modelled on Pt(111) surface, using density func-tional theory and climbing-image nudged elastic band. A clear trend was observed: hydrogen dissociation was thermodynamically and kinetically favourable at initial steps however becomes more difficult as more hydrogen was removed. In this process, the carbon skeleton hybridization goes from sp³ toward sp²/sp character. This result in a stronger bond between carbon and hydrogen. After overcoming the activation barrier of the last steps and full dehydrogenation is achieved, the coupling of unsaturated carbon fragments is thermodynamically favourable. This is consistent with graphene nucleation on platinum. Computed results show that the hydrogen removal requires less energy if a catalyst be able to electronically weaken the late-stage C–H bonds. Catalysts with steps or defects also require less energy for hydrogen removal. The study of hy-drogen dissociation on Pt(111) surface provides the mechanisms of the reactions and workflow of DFT and Cl-NEB, which helps improving the existing gaps.
  • A machine learning approach to predicting the melting points of liquid metal alloys for consumer electronics cooling
    (2025-09-29) Liu, Jiayi
    School of Chemical Engineering | Master's thesis
    This thesis investigates liquid metal phase change materials for cooling consumer electronics. A phase change material stores heat while melting and releases it while solidifying, which helps keep device temperatures in the safe 45–55℃. The study compiles liquidus data from peer reviewed papers and phase diagram databases. The final physics-expanded table contains 22,231 compositions and uses an 85/15 split by alloy system for validation. The method trains a Transformer model to predict the liquidus temperature from elemental fractions and simple physicochemical features. The screening then enumerates 1,317,840 unique compositions by combining 19 elements on a 0.1 at.%grid. The workflow ranks candidates by absolute deviation from 50℃ and forms a shortlist within 45 to 55℃. The lab prepared several shortlisted alloys for tests. The paper presents one representative DSC result. Differential scanning calorimetry measured the melting behavior, showing an onset at about 45.6℃ and a main peak at about 49.3℃ for the shortlisted alloy. These findings show that the workflow contracts a very large search space and supports safe thermal design in compact devices.
  • Development of Catcher/Tag-based purification method for Panus rudis laccase
    (2025-09-24) Ahvenjärvi, Laura
    School of Chemical Engineering | Master's thesis
    Recombinant enzymes are a safe and environmentally friendly alternative for chemical catalysis in industrial processes and one such alternative are laccases. Laccases (EC 1.10.3.2) are oxidoreductases and applicable in many industry applications since they oxidize a wide range of substrates with water as the byproduct. There is a demand for laccases in industrial biotechnological applications, but they often require characterization of the enzyme. Extensive characterization requires efficient purification of the enzyme, but the purification of laccases is expensive and produces low yields. Conventional affinity purification with polyhistidine-tag (HisTag) is especially challenging. Potential solution is to use Catcher/Tag-based purification method. Catcher/Tag is a protein/peptide conjugation pair which has shown great efficiency in protein purifications. This thesis aimed to evaluate the purification of white-rot fungal Panus rudis laccase with Catcher/Tag-based purification method. The second aim was to use Catcher/Tag version called SilkCatcher/SilkTag for purification for the first time and assess its suitability as a purification method. SilkCatcher/SilkTag is engineered from a surface protein domain of Lactobacillus plantarum. Three different P. rudis laccase variants with SilkCatcher, SilkTag or SpyTag, were produced in Pichia pastoris. SpySwitch/SpyTag is another Catcher/Tag version originating from the surface protein of Streptococcus pyogenes. The two Catcher variants, SilkCatcher and SpySwitch, were produced in Escherichia coli. SilkCatcher, SilkTag or SpyTag attached to laccases functioned as purification tags while SilkCatcher, SpySwitch and SilkTag were coupled to purification resin to purify laccases. As SpySwitch could not be produced in soluble form, purification was performed with only SilkCatcher and SilkTag. SilkCatcher/Tag showed good degree of purification though SilkCatcher and SilkTag binding was weak. The effectiveness of laccase purification with Catcher/Tag method could not be concluded decisively due to the weak binding and SpySwitch being produced in insoluble form. SilkCatcher/Tag has potential as a purification method, and P. rudis laccase was successfully produced in P. pastoris. This thesis provides the groundwork for future research of laccase purification with Catcher/Tag.
  • Recovery of REEs from immiscible silicate-phosphate slags/molten ash with focus on recycling of LFP
    (2025-09-29) Abaid Ur Rehman, Hafiz
    School of Chemical Engineering | Master's thesis
    The global demand for rare earth elements (REEs) is rapidly increasing due to their essential role in green technologies such as solar panels, electric vehicles, and wind energy. As a result, the number of end-of-life (EOL) products containing REEs is also increasing, leading to more REE-containing waste being generated annually. At the same time, the global supply of REEs is largely controlled by China, which creates supply risk for other regions, including the European Union. For this reason, REEs have been added to the list of critical raw materials (CRMs) in the EU. In addition to supply challenges, the production of REEs is also affected by the so-called balance problem, which leads to the overproduction of some REEs and underproduction of others. Recycling of REEs is considered one possible solution to reduce both the supply risk and the balance problem. In this study, the recovery of REEs from incinerator bottom ash (IBA) was investigated through high-temperature treatment. The use of lithium iron phosphate (LFP) and calcium pyrophosphate (Ca₂P₂O₇) as phosphorus sources was studied to promote the formation of immiscible silicate and phosphate liquid phases, enabling the selective partitioning of REEs into the phosphate phase. Another purpose of using LFP was to investigate the potential for selective recovery of lithium (Li) under the applied conditions. A series of experiments was conducted in a vertical tube furnace at 1150 °C and 1200 °C under controlled oxygen partial pressures of 10⁻⁷, 10⁻⁹, and 10⁻¹¹ atm, each with a holding time of 48 hours. The samples were analysed using scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS), electron probe microanalyser (EPMA), and laser ablation inductively coupled plasma - mass spectrometry (LA-ICP-MS). According to the results, the samples with LFP as the phosphorus source, treated at 1200 °C and at low oxygen partial pressures of 10⁻⁹, and 10⁻¹¹ atm, showed clear formation of two immiscible liquid phases (silicate and phosphate) without the presence of solid phases. Both of the studied REEs (La and Nd) were strongly enriched in the phosphate phase, indicating effective selective partitioning. However, lithium was almost equally distributed between both phases, meaning that its recovery was not possible under the given conditions. While the process successfully concentrates REEs into the phosphate phase, an additional step will be required to recover them from the phosphate for practical use.