| 1. |
- Kong, Xueying, 1993-
(författare)
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Porous Materials and Their Cellulose-Based Composites : Synthesis, Nanoengineering, and Applications
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Porous materials, such as porous carbons (PCs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), show considerable potential across various fields because of their rich microporous and mesoporous structures and large surface areas, yet they grapple with challenges like environmentally unfriendly fabrication methods and poor processability. In this thesis, we investigated environmentally friendly fabrication methods for porous materials, nanoengineering techniques for processing these materials, and their potential applications.Cladophora cellulose (CC), a naturally abundant biopolymer, was used to prepare PC via a one-step physical carbonization/activation method without using any corrosive activation agents. The obtained CC-derived PC (CPC) showed a high specific surface area (507.2 m2 g−1) and rich microporous structure. Additionally, we introduced a simple and environmentally friendly method for synthesizing imine-linked COFs at room temperature using water as the solvent. The method involves a key step in which aldehyde monomers are pre-activated by acetic acid, which promotes the aldehyde monomers to dissolve in water, enhancing their reactivity with amine monomers, and ensuring the formation of crystalline COFs. Consequently, we synthesized 16 distinct imine-linked COFs with high crystallinity and specific surface areas. Furthermore, this thesis focusses on improving the poor processability of these materials caused by the infusible and insoluble nature of their powders. The poor processability of these porous materials makes them difficult to process into desired structures and shapes. Here, we introduce two nanoengineering methods: i) Interweaving porous materials with CC nanofibers (CNFs) to form CNF-porous material aqueous solutions; and ii) Interfacial synthesis of porous materials on the surface of carboxylated CNFs to form CNF@porous materials with nanofiber structures in aqueous solutions. The obtained composite suspensions can be fabricated into freestanding and flexible composite nanopapers via a vacuum filtration and drying process. In addition, they can be processed into freestanding aerogels through a freeze-drying process. Consequently, we have successfully prepared freestanding and flexible CC-CPC nanopapers and CC-CPC aerogels, c-CNT@COF/CNT/CNF nanopapers (c-CNT: carboxylated carbon nanotube), CNF@MOF nanopapers, and CNF@COF nanopapers and demonstrated their potential in various applications, from efficient CO2 capture and organic pollutant removal to advanced energy storage and solar vapor generation. In summary, we used environmentally friendly methods to synthesize PC and imine-linked COFs, circumventing the need for corrosive chemical agents and toxic organic solvents, respectively. Furthermore, by combining CNFs with porous materials, we successfully created freestanding and flexible nanopapers and aerogels, thereby addressing the issue of poor processability associated with porous materials.
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| 2. |
- Sánchez Martín, Darío
(författare)
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Visual and magnetic detection of antimicrobial resistance genes using nanoparticles and isothermal amplification
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antibiotic resistance is becoming an increasing concern, necessitating new ways to diagnose and treat it rapidly and accurately. One proposed solution is the use of nucleic acid amplification tests, capable of detecting resistance in just a few hours, as opposed to the several days that traditional testing methods may require. One concept for such a test involves the volume-amplified magnetic nanobead detection assay (VAM-NDA), which combines rolling circle amplification (RCA), an isothermal amplification method, with magnetic nanoparticles (MNPs) for the detection of the RCA products.In this thesis, improvements have been made to the VAM-NDA. Coupling of RCA products with microparticles allowed a greater hydrodynamic increase of the MNPs when bound to these products, facilitating the detection of shorter products. Moreover, circle-to-circle amplification (C2CA) was performed, a technique comprising two RCA reactions, increasing the sensitivity of the assay and leading to a 1 attomole limit of detection. Optimization of several reaction parameters has allowed for increased sensitivity. Of highest relevance are the changes made to the length of padlock probes, oligonucleotides used for target recognition. These changes resulted in faster amplification. Equally important is the work conducted on phi29 DNA polymerase. Different manufacturers and mutants of this enzyme were tested, resulting in an improved and faster amplification. However, a previously undiscovered feature of this enzyme was also investigated, where phi29 amplification is competitively inhibited by the presence of ssDNA oligonucleotides, regardless of whether digestion of those is possible or not.Finally, a novel detection method for RCA products was developed, where nanoparticles were made to aggregate with the DNA products, resulting in aggregates visible to the naked eye. This method was further optimized, and integrated with C2CA, as well as substituting MNPs for coloured polystyrene nanoparticles. The result is a fast assay that can detect down to 100 zeptomoles of target DNA visually, in less than two hours. The use of coloured nanoparticles also allowed multiplexing using two sets of nanoparticles with different colours, and two targets were detected in a single sample.In conclusion, this thesis brings a DNA detection method one step closer to its use in the identification of antimicrobial resistance. The improvements to VAM-NDA and magnetic detection, advances on padlock probe design, the discovery of a novel behaviour of phi29 DNA polymerase, and the potential for naked-eye detection and multiplexing are of high relevance for future basic and translational research.
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| 3. |
- Zhou, Shengyang
(författare)
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Nanocellulose and Metal-Organic Framework-Based Composites : Synthesis, Characterization, and Applications
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanocellulose is one of the most promising of the green materials available for use in a sustainable economy because of its natural abundance and renewability. Compared to petroleum‒derived synthetic polymers, nanocellulose has many unparalleled advantages such as its unique nanofibrous structure, high thermal stability, mechanical flexibility, rich surface chemistry, biocompatibility, and biodegradability. The tremendous potential of nanocellulose has recently been realised in its use as a building block substrate for multifunctional applications such as energy storage devices, flexible electronic devices, and advanced filtration units. In future, more insight will be gained into the fundamental structure−function relationships of nanocellulose‒based functional materials, with subsequent advantages for the materials industry.Metal–organic frameworks (MOFs) are an emerging family of coordination polymers with unique crystalline porous features. Because of their diverse design principles and facile chemical synthesis processes, thousands of MOFs are currently under development. MOFs have found huge application value in many fields, including gas separation and storage, energy storage, industrial catalysis, and so on. However, control of the microscopic dimensions and crystal alignments of MOFs remains a big challenge. The insolubility and brittleness of MOF crystals have also resulted in problems with shaping and processing these substances. These problems have restricted the broader application of MOFs. This thesis explores the concept of nano‒composition with a focus on a previously little explored pathway for processing MOFs with the assistance of Cladophora cellulose (CC) extracted from green algae. Firstly, interfacial synthesis was developed through collaborative coordination of metal ions between the carboxyls on CC and the ligands in MOFs (Paper I). This approach enabled the continuous growth of MOF crystals along the CC to form core–shell hybrid CC@MOF nanofibers. These nanofibers were processable in aqueous solution, enabling facile fabrication of various bulk materials such as films (Paper I) and aerogels (Paper II). The CC@MOF composites had hierarchical porosity, good mechanical flexibility, low thermal conductivity, and high thermal stability. Various applications of the CC@MOF composites have subsequently been demonstrated; these include thermal insulation and fire retardancy (Paper II), electrochemical energy storage (Paper III), photothermal conversion evaporation for efficient water desalination (Paper IV), and solar‒driven ionic power generation (Paper V). This thesis covers the synthesis, structural characterization, and proof‒of‒concept applications of the CC@MOF composites, providing a basic understanding of the relationships between the structure and performance of composite materials.
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| 4. |
- Åhlén, Michelle, 1992-
(författare)
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Porous Sorbents for Environmental Applications and Selective Laser Sintering 3D Printing of Dosage Forms
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rising levels of greenhouse gas emissions from vehicular and industrial pollution constitute a serious concern not only for the environment but for our entire society. Traditional gas capture and separation techniques, such as amine scrubbing for CO2 gas separation, have been commonly used at a commercial scale, however issues relating to high costs and high energy requirements for sorbent regeneration have limited the efficiency of many of these techniques. The use of porous sorbents, such as metal-organic frameworks (MOFs), has garnered significant attention as an alternative method for the capture and separation of greenhouse gases in recent years, particularly due to their structural and functional tunability. Thus, part of this thesis explores the selective capture of CO2 and SF6 in five new MOFs and mixed-linker zeolitic imidazolate frameworks (ZIFs). The CO2 and SF6 adsorption in microporous bismuth-based MOFs containing narrow ultramicro-pores (e.g. UU-200) was not found to be correlated to the N2-accessible surface area of the framework but was related to pore size effects and possibly framework flexibility. Similar mechanisms for SF6 capture were observed in vanadium- and gallium-based MOFs (UU-201-4) in which an enhanced van der Waals interaction between the gas molecules and the pore surface was obtained due to the pore size of the materials coinciding with the kinetic diameter of SF6 (5.5 Å). This further resulted in good uptake capacities as well as SF6-over-N2 selectivites above 2.75 mmol g-1 and 43, respectively. Furthermore, the selective uptake of CO2 and SF6 could be modified in mixed-linker ZIF-7-8s by tuning of the pore aperture size through a controlled incorporation of the bulkier benzimidazolate linker in the frameworks.The removal of other environmental pollutants (e.g. phosphates) in porous materials such as amorphous mesoporous magnesium carbonate (MMC) was also investigated and showed that the material had superior sorption capacities as compared to its crystalline, non-porous counterpart. MMC was also found to be a capable functional support for other materials such as semiconducting TiO2 and ZnO nanoparticles. The TiO2/ZnO-composite was observed to retain the porosity as well as UV-blocking properties of the respective pristine materials.A part of this thesis was also devoted to the fabrication of personalized solid dosage forms for pharmaceutical applications. To achieve this, 3-dimensional selective laser sintering (SLS) printing was utilized to print both purely polymeric and drug-loaded tablets (containing 10 wt.% naproxen). The subsequent weight and mechanical strength of the obtained tablets could be tuned by either modifying the NIR-active pigment concentration in the powder formulation or by changing the laser energy input that is used during the printing process. Amorphization of the crystalline drug was also achieved in-situ during printing thus showing that the SLS 3D printing may be a promising technique for the manufacturing of solid amorphous dispersions with tailorable properties.
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| 5. |
- Åkerlund, Lisa, 1986-
(författare)
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Electrochemical characterizations of conducting redox polymers with proton traps : Enabling proton cycling in aprotic systems for high potential energy storage
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Floods, droughts and unpredictable weather could be the new reality for millions of people in a near future, unless we drastically decrease our greenhouse gas emissions to prevent the global average temperature from increasing even further. Material innovations will most certainly be essential for many of the technical solutions needed in order to tackle environmental issues. One major challenge is how to deal with the massive energy demand, following the average lifestyle of today, in a way that is both reliable and sustainable. Renewable energy sources have a varying output over time, hence cannot meet the demand for electricity by themselves. To buffer between demand and production, new ways to store the renewably produced energy are crucial. From a life cycle aspect conventional battery types are far from sustainable, and, with the increasing number of electronic devices for numerous applications, we need new options.This thesis explores conducting redox polymers (CRPs), which can be utilized as organic cathode materials in high potential energy storage. Hydroquinone (HQ) was applied as the capacity carrying pendant group, and by the introduction of a proton trap functionality the high reduction potential of quinone-proton cycling was achieved also in aprotic electrolytes. The high reduction potential allows for redox matching with the polymer backbone, crucial for CRPs to work as energy storage materials without any additives, and this was studied by in situ conductance with IDA. In situ EQCM was applied in order to examine the cycling chemistry, and the constant mass uptake during the full oxidation cycle (and reverse during the reduction cycle) indicated uptake of charge compensating ions. Further, the proton trap functionality and its effectiveness were investigated by compositional variation, FTIR and variation of electrolyte. In situ UV/Vis was applied in order to study the electronic transitions of the bandgap, the charge carriers and the pendant group redox conversion.The results presented introduce a new route for utilizing protonated forms of quinones as capacity carriers in aprotic media, by incorporating a proton trap in the material. The battery prototypes point to the versatility of the proton trap materials, having reversible proton cycling also when the electrolyte contains metal salts. With dual-ion type batteries the cycling chemistry of the anode is disconnected from the cathode, which allows for free choice of anode material.
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