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- Hoogendoorn, Billy W.
(författare)
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Exploring cellulose as a biomacromolecule for enhanced battery metal ion recovery/recycling
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The research focused on the effects of integrating nanocellulose in the solidification of metal ions into metal oxide particles or metallic electrodeposits. Firstly, the cellulose was isolated as highly crystalline ca. 15-25 nm thick and 500 nm long fibers from bacterial cellulose using acid hydrolysis and had a negative surface charge. Positively charged nanocellulose was also explored using cationic functional groups substituted onto the nanofiber surface. The effect of the isolated nanocellulose when preparing metal oxides via enforced precipitation of zinc metal ions into zinc oxide particles was investigated at ultra-low nanocellulose content ≤0.01 %. The result indicated that increased reaction yields of ~15 % and a reduction of particle sizes by up to 50 % could occur at nanocellulose concentrations of 0.01 %. The kinetics was studied and showed that the presence of cellulose consistently increased the consumption rates of zinc ions. If the reaction consumed a large fraction of the zinc-ions (>80%) within the first 15 min, continued growth of ZnO was also suppressed by the presence of nanocellulose. This was observed during the synthesis of sheet-like ZnO-particles, where an increase in reaction yield from 81 to 95 % hindered the growth of additional nanorods, which otherwise had formed after 15 min of the reaction. Further, nanocellulose was then evaluated for metal recovery reactions of Zn, Cd, and Ni using electrodeposition. Zinc and cadmium, which generally form separate, faceted metal particles during electrodeposition, grew large dendrites when nanocellulose was present in the electrolyte. In the case of cadmium, the formation of dendrites was correlated with increases in yield by up to 15 %. For nickel, which always deposited as uniform and non-faceted layers, the presence of nanocellulose did not result in dendritic deposits. While the presence of 0.05 % of nanocellulose did not affect the yield for negatively charged nanocellulose, positively charged nanocellulose decreased the deposited amount by up to ca. 20 %. The temperature was also used to tune the dendritic formation during the zinc deposition. The major finding was that while the zinc electrodeposition in the presence of nanocellulose at 20 or 40°C induced dendritic growth, a similar deposition at 60 °C did not, reverting the deposition towards promoting dense and faceted zinc particles. The research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition aligns with the United Nations' Sustainable Development Goals (SDGs), particularly Goal 12: Responsible Consumption and Production, and Goal 1: End poverty in all its forms everywhere, but also Goal 13: Climate Action. The use of nanocellulose as an additive can contribute to sustainable consumption and production practices, reducing waste and conserving natural resources. This approach can help to address the challenge of meeting growing demands for metals used in various industrial applications, particularly those associated with battery manufacturing. Recycling valuable metals using nanocellulose can reduce the environmental impact of mining and processing ores, contributing to sustainable resource management and contribute to poverty reduction for creating job opportunities. Furthermore, the use of nanocellulose in electrodeposition reactions will help to combat climate change by promoting more efficient and environmentally friendly metal recovery methods, potentially reducing the carbon footprint associated with traditional metal recovery and mitigate the environmental impacts of metal extraction and mining. Overall, the research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition demonstrates innovative and sustainable solutions for resource management, contributing to the UN's SDGs.
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| 2. |
- Li, Ge
(författare)
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Computational Studies on Homogeneous Water Oxidation Catalysts
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To combat the increasing energy demand and climate change, artificial photosynthesis is a promising approach to producing renewables by storing energy into chemicals and fuels. Water oxidation, responsible for offering electrons and protons to the reduction reactions, suffers from slow kinetics. Consequently, developing highly efficient water oxidation catalysts (WOCs) reacting via desirable mechanisms plays an essential role in reaching the goal of artificial photosynthesis. Molecular WOCs in homogeneous catalysis could serve as models to understand the structure-property relationship and the reaction mechanisms owing to their well-defined structures and easily characterized properties. In Chapter 1, a variety of Ru- and Fe-based molecular WOCs are introduced. The two catalytic mechanisms for the O-O bond formation, water nucleophilic attack (WNA) and interaction of two metal-oxos (I2M), are described in Chapter 1.To understand the catalytic mechanisms for designing better WOCs, various theoretical techniques have been applied. Density functional theory (DFT) method was used to study the molecular properties of catalysts and the reaction energetics. Molecular dynamics (MD) and potential of mean force (PMF) were employed to investigate the behavior of catalysts and to calculate the free energy change along a specific coordinate in the explicit solvent. The theory for computing redox potentials, acid dissociation constants, reaction rate constants, and the descriptions of different solvation models are presented in Chapter 2.The family of Ru(bda)(py)2 (bda2- denotes 2,2'-bipyridine-6,6'-dicarboxylate, py denotes pyridine) complexes exhibits extremely high catalytic activity via the I2M mechanism under acidic conditions. Extensive studies have previously been conducted on the primary and secondary coordination environments. In Chapter 3, the first section focuses on three different modifications on the para-sites of the two pyridines. It is found that the complex with the longer hydrophobic group substituting the para-sites of two pyridines demonstrates the highest activity, which is attributed to the stronger binding energy between two RuV monomers. We conclude that the hydrophobic effect is dominating in enhancing the catalytic performance via the I2M mechanism. The second section of Chapter 3 studies the isolated crystal structure of the pseudo seven-coordinate RuIII-aqua intermediate obtained by connecting two meta-sites of pyridines with an ethylene glycol ether linker. DFT was used to study the formed H-bond network between the distal ligand and Ru(bda)(py)2. The influence of micro-solvation on the incoming aqua ligand was analyzed in the form of bonds and interactions. Incorporating a distal ligand could be an effective strategy to investigate the outer coordination environment effects. In the third section of Chapter 3, the linkers connecting two meta-sites of pyridines were changed and three more Ru(bda)(py)2-based catalysts with hydrophobic (aliphatic) and hydrophilic (ethylene glycol ether) linkers of different lengths were synthesized to study the outer coordination environment effects. The hydrophobic ligands lower the potentials slightly by stabilizing the key intermediates. The complex with the longer hydrophobic distal ligand demonstrates the highest TOF with the first-order kinetics. The I2M mechanism is suppressed owing to the limited flexibility of distal ligands validated by the nuclear magnetic resonance spectroscopy and the DFT-calculated energy differences between the conformations of distal ligands in the front and in the back of the bda ligand. The strategy of introducing hydrophobic outer coordination environment could be beneficial to design catalysts involving PCET reactions.Inspired by the Ru(bda)(py)2 catalyst and aiming to reduce the usage of Ru, a computational comparative study on Ru(bda)(py)2 and Fe(bda)(py)2 is presented in Chapter 4. Fe(bda)(py)2 was built by directly replacing Ru catalytic center of Ru(bda)(py)2 with Fe and maintaining the rest of the ligand system. The Fe-based complexes at different valence states prefer higher spin states while the Ru-based complexes are more stable at the lowest spin states. Unlike the Ru, the Fe center disfavors the 7-coordinate structure. Concerning the catalytic performance, the Fe(bda)(py)2 requires much higher potentials to reach the reactive FeV species than the Ru(bda)(py)2. The 6-coordinate [FeV(bda)(py)2=O]+ also has a higher energy barrier of the O-O bond formation via the I2M mechanism than the [RuV(bda)(py)2=O]+. We propose that directly substituting the Ru catalytic center with Fe fails to generate a viable catalyst and a significant ligand system modification is required.An alternative feasible catalytic mechanism is suggested for a highly active dinuclear Fe-based WOC in Chapter 5. The mechanism is proposed where two oxidation reactions are first required to reach the reactive state with calculated potentials matching the onset potential in the experiment. The reactive species is then decomposed by the nucleophilic chloride counter ion attack to produce two Fe-based monomers, which finally form the O-O bond by the radical coupling pathway. The calculated energy barriers and first-order kinetics match well with the experimental observations.
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| 4. |
- Sahu, Siddharth S., 1994-
(författare)
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Detection of Bio-analytes with Streaming Current : From Fundamental Principles to Novel Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A biosensor based on streaming current is a new and relatively unexplored subject with significant potential. This thesis attempts to gain a deeper understanding of the governing principles, and then exploit them to further improve its performance as well as develop novel applications. To this end, the underlying theoretical frameworks were examined and two critical parameters of the target: its size and electric charge, influencing the sensor’s sensitivity were identified. This was followed by experimental evaluation of the parameters, using a set of tailor-made proteins, aiming to understand the nature and extent of their influence on the sensor response in relation to simulation performed following an established model.The dependence of the sensor response on the charge of an analyte, or specifically the charge contrast between the sensor surface and an analyte, opens a new avenue to improve the sensitivity and also to develop novel functionality. First, this aspect was exploited to improve the sensitivity by optimizing the surface functionalization strategy. Three such methods were compared in terms of the resulting zeta potential of the surface. The sensitivity was the highest when the charge contrast was maximum. The optimal functionalization strategy was then used for highly sensitive detection of extracellular vesicles (EVs), where an improvement in the limit of detection by two orders of magnitude over the previously reported results was demonstrated. Two applications of the improved method were then demonstrated: monitoring the effectiveness of targeted cancer medicines and analysis of liquid biopsy of cancer patients via sensitive profiling of EV-membrane proteins.Improvement in the detection specificity is a critical aspect of biosensing. This was achieved by implementing a sandwich immunoassay and demonstrating the proof of concept using trastuzumab as the target and Z-domain as both the capture and detection probes. Although the improved selectivity came at the cost of a lower sensitivity, this could be mitigated via DNA-conjugation with the detection probes, a novel electrostatic labelling strategy that allows for improvement of the sensitivity by exploiting the electrostatic influence. An application of this method was then demonstrated by detecting the target from a complex medium of E. coli cell lysate. Continuing the prospect of charge engineering of antibodies, a set of positively and negatively charged antibodies were synthesized by conjugating poly-lysine and DNA oligonucleotides, respectively. This enabled stepwise, multiplexed membrane protein analysis of EVs using the alternating charge-labelled antibodies. The method was then applied to investigate EV-heterogeneity.
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