Chemistry

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This is the collection for the University of Waterloo's Department of Chemistry.

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Enhanced Performance and Stability of Planar Heterojunction Solar Cells via Hole Transport Layer Engineering and Low-Cost Fabrication
(University of Waterloo, 2026-01-16) Habibzadeh, Elaheh
Global energy demand has grown extensively in recent decades, and it has continued to rely on fossil fuels that are accompanied with environmental concerns. This has intensified the research for renewable energy alternatives with solar power standing out as a leading candidate due to its abundance, scalability and rapidly declining costs. As photovoltaic (PV) technologies have evolved significantly, their widespread adoption continues to face barriers in efficiency, stability and manufacturing costs. While inorganic semiconductors such as crystalline silicon remain dominant due to their favorable band gap and long-term stability, hybrid solar cells such as organic–inorganic heterojunction solar cells have gained increasing attention for their ability to combine the tunability and ease of processing of organics with the superior charge transport and stability of inorganics. In this work, we have investigated the stabilization of planar heterojunction solar cells through the incorporation of dimethyl sulfoxide (DMSO) into PEDOT:PSS-based hole transport layers (HTLs). The acidic and hygroscopic nature of PEDOT:PSS is a well-known source of device instability, leading to accelerated degradation under ambient conditions. By employing DMSO as a cosolvent alongside ethylene glycol and methanol, this work demonstrates that optimized modification enhances electrical conductivity, reduces recombination, and markedly improves stability. Devices incorporating DMSO-treated PEDOT:PSS films retain nearly 89.4% of their initial efficiency after 72 hours of ambient storage, in contrast to the sharp decline seen in control devices without DMSO. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) confirm improved surface morphology and a favorable redistribution of conductive domains. The findings establish DMSO modification as a practical, cost-effective strategy for producing more inherently resilient heterojunction solar cells. Following these insights, we introduce dimethyl sulfone (DMSO₂) as a solid-state additive for PEDOT:PSS films. Unlike liquid cosolvents, DMSO₂ crystallizes upon drying, inducing a unique reorganization of polymer microstructures that enhances phase separation and alignment of conductive PEDOT chains. The resulting films exhibit superior conductivity, improved charge transport, and greater stability against moisture induced degradation. Devices fabricated with DMSO₂-doped PEDOT:PSS achieve efficiencies up to 15.5% (EMD2) and an average T80 of ∼913 h of ambient storage (ED2), a substantial improvement over conventional treatment. Through a combination of external quantum efficiency (EQE), AFM, and conductivity analyses, this work highlights the ability of DMSO₂ to simultaneously enhance efficiency and extend ambient storage longevity, offering an environmentally benign and scalable pathway for advancing PEDOT:PSS-based solar technologies. We also address the challenge of electrode optimization by introducing a rapid and low-cost method of shadow mask fabrication by desktop 3D printing. While electrode geometry is critical to current collection efficiency, series resistance reduction, and overall photovoltaic performance, traditional fabrication techniques are expensive, time-consuming, and inflexible. By employing polyethylene terephthalate glycol-modified (PETG) filaments for 3D printing, this study demonstrates a streamlined approach to fabricating custom shadow masks for top electrode manufacturing in hours rather than weeks. Comparative testing of three geometries (comb-like busbar, central busbar, and crossed busbar) shows that the central busbar design achieves superior efficiency enhancement by 21.62% and improves the fill factor by reducing resistive losses and balancing optical transparency. This work illustrates how low-cost additive manufacturing can democratize device prototyping, accelerate design iterations, and lower research and production costs without compromising performance. In summary, this dissertation presents a cohesive exploration of strategies to improve efficiency, stability, and fabrication simplicity of planar heterojunction solar cells. Through targeted material modifications and innovative fabrication methods, the studies collectively highlight pathways to bridge laboratory innovation with commercial feasibility. Together, these contributions underscore the critical role of polymer modification and accessible fabrication in the evolution of next-generation solar cells, with the ultimate goal of advancing the prospects of clean, scalable, and sustainable energy technologies.
Development and Evaluation of Hydrophobic Catalysts for Deuterium Enrichment in a Gas-Vapor Reactor
(University of Waterloo, 2026-01-07) Lau, Jordan
Deuterium, an isotope of hydrogen, has found diverse applications in pharmaceutical, nuclear, and analytical fields owing to its chemical similarity to protium, but distinct mass which gives rise to the kinetic isotope effect. The water-hydrogen catalysis method offers a clean route for deuterium enrichment from its natural abundance (0.015 %). This process can achieve industrial-grade purity (> 99 %) in the presence of a hydrophobic catalyst. However, the industrially used Pt/C/PTFE catalyst is costly, making the initial capital requirement for deuterium enrichment high. Further, limited documentation on the synthesis and performance of Pt/C/PTFE hinders the development of viable alternatives. This thesis develops a co-current gas-phase reactor and tests its ability to directly study kinetics for catalysts that perform deuterium enrichment through isotopic exchange between H2/H2O. A protocol for a Pt/C/PTFE catalyst was developed and standardized. This catalyst was used to establish benchmark catalytic performance metrics for deuterium enrichment of H2O by catalytic exchange between a blended H2/D2 and H2O vapor stream. A series of Ni-Pt alloys were then explored as low-Pt alternatives to this industry standard catalyst. The reaction temperature and reaction time required for alloying of NiPt with stoichiometric ratios of 1Ni:3Pt, 1Ni:1Pt and 3Ni:1Pt were established. The resultant alloy nanoparticles were prepared into Ni-Pt/C/PTFE catalysts, analogous to the industry standard Pt catalyst, and their catalytic properties were tested. A reliable evaluation method for assessing catalytic activity was developed, through which mass-transfer coefficients and activation energies were determined. Comparative analysis showed the NiPt/C/PTFE alloy to successfully catalyze the isotopic exchange reactions but not outperform Pt/C/PTFE. Mechanistic analysis provides evidence for OH* oversaturating the surface at elevated temperatures in the reaction, which may be responsible for lower-than-anticipated catalytic performance. Further investigations into temperature-dependent kinetics may guide the rational design of cost-effective catalyst for deuterium enrichment.
Computational Insights into the Corrosion Behavior of NbTaMoW and NbTaMoWV High-Entropy Alloys in Molten Fluoride Salts
(University of Waterloo, 2025-12-23) Katai, Agnes
Molten salt reactors (MSRs), one of the six next-generation nuclear reactor designs, employ molten fluoride salts as the coolant and/or fuel solvent when operated in a thermal-neutron spectrum, and offer higher thermal efficiency compared to today’s water-cooled reactors. Nonetheless, the elevated temperatures, corrosive nature of salts, and high neutron irradiation in MSRs create a harsh environment for structural materials. The influx of impurities, namely moisture, into the molten salt medium has long been shown to exacerbate the corrosivity of fluorides. Owing to their superior thermal and mechanical robustness, refractory high-entropy alloys with a body-centered cubic (BCC) structure have been proposed as candidate containment materials for MSRs. Nonetheless, the degradation of these advanced materials in molten fluorides is an intricate process whose underlying mechanisms remain poorly understood. This study explores the corrosion behavior of BCC (100)-NbTaMoW and (100)-NbTaMoWV surfaces in pure and hydrated FLiBe salt via density functional theory and ab initio molecular dynamics simulations. Electronic structure analyses, including density of states and crystal orbital Hamilton population, provide insight into the interfacial bonding and charge transfer. Irrespective of salt purity, NbTaMoW exhibits minimal d-band shifts which highlight its electronic stability, and weak interactions with fluorine and oxygen. The addition of vanadium to form NbTaMoWV further diminishes susceptibility to oxidation and enhances stability at the salt interface, suggesting superior corrosion resistance in both pure and hydrated salt.
Polymeric Oil Additives and their Small Molecule Analogues Studied via Pyrene Excimer Fluorescence
(University of Waterloo, 2025-12-22) Frasca, Franklin
Several series of pyrene-labeled small molecules (PySMs) and large macromolecules (PyLMs) were studied with pyrene excimer formation (PEF) through the analysis of their monomer and excimer fluorescence decays with either the model free analysis (MFA) or the fluorescence blob model (FBM). In these studies, the conformation and dynamics of the pyrene side chains of the PySMs were characterized with parameters such as the average rate constant () of PEF or the number (Nblob) of structural units inside a polymeric blob. These parameters were then compared to those obtained for the same PySMs after they had been incorporated into much larger macromolecules to generate PyLMs, whose specific pyrene-labeled subsections were probed by PEF. Since reports on the local pyrene concentration ([Py]loc), the values were compared for each PySM or PyLM in several organic solvents. Similarly, block copolymers (BCPs) were prepared where pyrene was randomly incorporated in a specific block, whose homopolymer analog had been characterized beforehand by PEF. Comparison of the PEF response of the homopolymer alone and incorporated as one block of a BCP provided information on the flexibility and dynamics of each specific block within the pyrene-labeled BCPs. The linear relationship between and [Py]loc established earlier for a variety of PyLMs was studied for a set of linear diols (Py2-DOs) and branched polyols (Py-POs), which were labeled through ester linkages with two or more pyrenes, respectively. increased more quickly with increasing [Py]loc for the Py2-DOs having a lower [Py]loc than for the Py-POs taking higher [Py]loc values, resulting in a clear breakpoint in the -vs-[Py]loc trends when transitioning between the two classes of PySMs. The effect was observed in the more polar solvents N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) and the relatively less polar solvents tetrahydrofuran (THF) and dioxane. The decreased sensitivity of toward [Py]loc for the branched Py-POs was attributed to the quickly diffusing pyrene side chains, which sterically hindered access to an excited pyrene from pyrenyl labels located further away on the chain. This effect reduced the effective [Py]loc sensed by an excited pyrene and yielded lower values. These results were further supported by calculating the theoretical th for the Py-PO samples based on the values of the Py2-DO samples. determined experimentally for the branched Py-POs was indeed lower than th as predicted from the lower [Py]loc sensed by excited pyrenes. A series of PySMs was synthesized by using amide linkages to attach 1-pyrenebutyric acid to diamines and polyethyleneamines to yield linear (Py2-DAs) and branched (Py-PA) molecules with two and more than two pyrenyl labels, respectively. Their values, determined in the same solvents used in the Py2-DO and Py-PO study, revealed that the polar solvents DMF and DMSO yielded a linear -vs-[Py]loc relationship without a breakpoint between the Py2-DAs and Py-PAs. However, a breakpoint was found in the -vs-[Py]loc trends in the less polar solvents THF and dioxane when transitioning between the Py2-DAs and Py-PAs, as had also been noted earlier for the Py2-DOs and Py-POs but in all solvents. This effect was explained by amide-solvent interactions which were favoured in the more polar solvents that enhanced the double bond character of the C-N bond in the amides, slowing their pyrene side chain motion and restoring access to all ground-state pyrenes of a Py-PA sample to an excited pyrene. The preceding results were used for comparison of the PEF response of a series of succinimide terminated polyisobutylenes (PIBSIs) having polyethyleneamine ends which were labeled with pyrene (PIBSI-PA-Pys) to resemble the Py-PAs of the previous study. Labeling the polyamine subdomains of the PIBSI samples enabled their detection through PEF and their vs-[Py]loc trends were compared with those of the Py-PAs. Since the PIBSI-PA-Pys were not soluble in the more well-behaved DMF and DMSO, their behavior was assessed in THF. Much lower values were obtained for the PIBSI-PA-Py samples than for the Py-PAs, but a linear -vs-[Py]loc trend was obtained that passed through the origin as dictated by the =kdiff×[Py]loc relationship. This linear trend provided a means for characterizing the polyamine blocks of PIBSI dispersants, which are often difficult to study by standard methods. The final study focused on poly(alkyl methacrylate) (PAMA) di-block BCPs synthesized through atom transfer radical polymerization with a poly(stearyl methacrylate) (PC18MA) and poly(butyl methacrylate) (PC4MA) block with pyrene randomly incorporated in either block. The flexibility of either block was characterized with the number (Nblob) of structural units a pyrene label could sense during its fluorescence lifetime through analysis of the fluorescence decays with the FBM. In good solvents for the BCPs, the Nblob values matched those predicted theoretically while in hexane, octane, and dodecane, which are poor solvents for the PC4MA block, the process of PEF was hindered whether pyrene was in the well-solubilized PC18MA block or the poorly solubilized PC4MA blocks. This effect suggested that interactions between the two blocks slowed dynamics compared to their well solubilized behaviour in the better solvents THF, toluene, and o xylene. The crystallization behaviour of the stearyl side chains in the BCPs was probed through their fluorescence spectra above and below their crystallization temperature. The results indicated crystallization-driven micellization of the BCPs through a closed-association mechanism. In summary, this thesis has probed an interesting set of PySMs with PEF to report on their internal dynamics and interactions with different solvents, while also illustrating how PEF can be applied to amplify the signal and probe the conformation and dynamics of subdomains within larger PyLMs in solution. These methods have a particular application for the study of polymeric oil additives which see widespread use in the lubricant industry.
Polyelectrolyte templated synthesis and formation behavior of high entropy alloys
(University of Waterloo, 2025-12-18) Li, Alexander
High entropy alloys have recently received significant attention in electrocatalysis because their unique compositional complexity can enhance both catalytic activity and long term stability. Despite this promise, there remains a lack of scalable synthesis methods that can produce nanoscale high entropy alloys with controlled and more complex morphologies. One promising strategy is to leverage the electrical double layer that forms when polyelectrolytes interact with metal salts. Polyelectrolytes can serve as effective templates by creating a locally high ion concentration along their surface, which promotes initial mixing during nanoparticle nucleation. In particular, polystyrene sulfonate can also bridge nucleating particles, allowing for the formation of more intricate, networked morphologies. The goal of this work is to investigate how polyelectrolyte concentration, polymer chain length, and different reducing agents influence the resulting catalyst composition and morphology. In addition, this study aims to provide insight into the mechanisms of nanoscale high entropy alloy formation.
Machine Learning Approaches for Thermoelectric Performance Predictions
(University of Waterloo, 2025-12-17) Barua, Nikhil
The area of thermoelectric (TE) research suffers from an affordable pathway to achieve high performance TE materials. This is because the merit of the experimental approach, although sacrosanct and irrefutable, often, resorts to a trial- and-error method approach. This approach is achieved through training, experience, and observed knowledge. Additionally, while working to find an effective solution through this approach, the target TE material is kept in mind. This introduces biasness in TE materials discovery. In TE research, recent studies have demonstrated the potential for accelerated materials discovery through artificial intelligence (AI) driven methods. Building on these advances, the thesis aims to assist experimental researchers in predicting the properties for high-performance thermoelectric (TE) materials. The objective in the thesis is realized with the developed and tested machine learning (ML) models to predict TE properties. The developed models are based on extreme gradient boosting (XGBoost) and light gradient boosting machine (LightGBM) algorithms. These algorithms, which form part of the ML framework, were trained using curated datasets. The models achieved good predictive accuracy of TE properties. The interpretability of the model predictions through SHapley Additive exPlanations (SHAP), provided interesting and chemically meaningful insights between TE material compositions and the TE properties. In one of our studies, the predictive models were validated experimentally for new doped SnSe systems to observe near consistency between predicted and measured κ values. Subsequently, we developed an end-to-end web application embedded with these ML models, hosted on Git-Hub and Microsoft Azure cloud to deliver rapid TE property predictions. The application is made accessible to TE researchers worldwide. The researchers can upload any set of compositions to the web interface and receive immediate thermoelectric (TE) property predictions. The methodology of the overall ML pipeline explained in the chapters are open for diversification with other Deep Learning (DL) algorithms or Generative AI (Gen AI) models. Furthermore, the ML models can be retrained by modifying the data in the existing dataset, in the direction of improving model accuracy. With this, the models can be used for experimental or first-principle based computational validation. The scope of this research offers more questions than answers leading to an extensive scope of hypothesis generation. Therefore, this opens unlimited opportunities for future investigations.
Total Synthesis and Stereochemical Assignment of Turnercyclamycin C
(University of Waterloo, 2025-12-16) Kim, Gyeongsu
Turnercyclamycins (TCMs) are a new family of cyclic lipopeptide antibiotics (cLPAs) isolated from Teredinibacter turnerae, a symbiont of shipworms. They contain thirteen amino acids, eight of which are contained in a macrocycle closed by an ester bond. Attached to the macrocycle is a linear pentapeptide that is lipidated at the N-terminus. The four members of this family, TCM A to D, only differ from one another in their lipid tail composition. Seven of the thirteen amino acids are non-proteinogenic: D-ornithine, D-threo-β-hydroxyaspartic acid (D-t-HOAsp), D-threo-β-hydroxydiaminobutyric acid (D-t-HODab), L-β-hydroxyisoleucine (L-HOIle), two D-allo-isoleucines (D-allo-Ile) and L-homoserine (L-hSer). Their mechanism of action (MoA) is unknown. The TCMs exhibit good activity against Gram-negative pathogens Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii (A. baumannii) including colistin-resistant A. baumannii suggesting that the TCMs act by a MoA that is different from colistin. These findings and the favourable pharmacokinetic properties displayed by the TCMs suggest that they may be good leads for the development of a novel antibiotic for treating colistin-resistant A. baumannii via a unique MoA. The total chemical synthesis of the TCMs has not been achieved and the configuration at the -carbon of L-HOIle is unknown. Here, our efforts to develop a total chemical synthesis of one of the TCMs, TCM C, which has a dodecanoyl fatty acyl tail, are described. These efforts began with the synthesis of D-t-HOAsp, D-t-HODab, and both stereoisomers of L-HOIle, suitably protected for Fmoc solid phase peptide synthesis (SPPS) using both literature and novel routes. Before synthesizing TCM C, an analogue of TCM C, called TCM C-CA, in which we substituted D-t-HODab for D-Dab, D-t-HOAsp for D-Asp and L-HOIle for L-Ile was prepared. This was achieved using Fmoc SPPS in an overall 5% yield. This synthesis provided valuable information on how to best perform some of the key steps such as ester bond formation and macrocycle formation without using up the valuable non-canonical amino acids prepared by chemical synthesis. The synthesis of two versions of TCM C, each one containing one of the two stereoisomers of L-HO-Ile, is in progress.
Design, Synthesis, and Characterization of Multimetallic Complexes Supported by an Imidazopyrimidine-Based Trinucleating Ligand
(University of Waterloo, 2025-10-17) Woods, Riley
Transition metal catalysis has revolutionized chemical synthesis for decades and has allowed for the development of several Nobel prize-winning chemical reactions and processes. These catalysts, however, usually rely on the use of rare Earth metals such as platinum-group metals, mainly palladium, leading to economic and sustainability concerns. Recent studies on the use of Earth-abundant elements nickel, cobalt, and copper have revealed that these metals have the potential of offering low-cost alternatives to the traditional catalysts. Furthermore, these metals can access many more states, allowing for new and complementary reactivities to be achieved. Whilst transition metal catalysis is a large and impactful field, the majority of known catalysts are monometallic in nature. A compelling yet much underexplored area is the use of multimetallic complexes. Several studies and reviews have highlighted the beneficial effect of having multiple metal centers held in proximity. These sorts of systems often display improved catalytic performances over their monometallic counterparts. Synergy or metal-metal cooperativity between the centers is usually responsible for these observations, sometimes allowing for multielectron processes that are simply not possible with traditional monometallic catalysts. In terms of trimetallics, there is a paucity of ligand systems that can reliably produce a precise and controlled arrangement of the three metal centers in a way that is useful in catalysis. This is due to most relying on flexible organic frameworks tied to a symmetric node, additionally excluding them from heterometallic applications. Herein is reported a new trinucleating ligand framework, bpipp, specifically designed to enforce close proximity among three metal centers upon complexation. Based on the inherently unsymmetric imidazopyridmine backbone, the ligand features a tridentate pincer-like binding pocket with two additional bidentate binding pockets. This approach utilizes scalable synthetic methods to create a rigid ligand scaffold that precisely controls the spatial arrangement of the metals. The versatility of this ligand is demonstrated through the synthesis of several trimetallic complexes of Ni(II), Cu(II), Co(II); fully characterized by NMR spectroscopy, ESI-HRMS, and X ray crystallography. Notably, our ligand design achieves remarkably short metal-metal distances ranging from 3.3–3.5 Å, significantly closer than most reported trimetallic systems. This structural feature establishes an ideal platform for investigating genuine three-metal cooperative effects in catalysis.
Dual Characterization of Hydrophobically Modified Polyamidoamine Dendrimers and their Surfactant Aggregate Hosts by Pyrene Excimer Fluorescence
(University of Waterloo, 2025-10-14) Liu, Donghan
This thesis explores why the conformational response of generation-0 polyamidoamine dendrimers end-labeled with four identical 1-pyrenealkanoyl groups (PyCX-PAMAM-G0 with X = 4, 6, 8, 10, and 12 for a butyroyl, hexanoyl, octanoyl, decanoyl, and dodecanoyl linker, respectively) to their local environment makes them excellent molecular probes to investigate surfactant aggregates. The conformation of the dendrimers was studied in polar organic solvents, spherical micelles, and non-spherical surfactant aggregates (NSSA) using pyrene excimer formation (PEF) and the model-free analysis (MFA) of the fluorescence decays. In N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) and in micelles of sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium bromide (DTAB), the dendrimers with shorter (X = 4, 6, 8) alkanoyl linkers adopted an ideal conformation. In contrast, the PyC10- and PyC12-PAMAM-G0 dendrimers experienced a conformational inversion in pure surfactant micelles driven by the hydrophobicity gradient (HG) generated between the polar surface and the hydrophobic interior of the micelles. The conformational inversion of the PyC10- and PyC12-PAMAM-G0 dendrimers was further investigated with mixed micelles prepared from SDS and DTAB mixtures. The decrease in conformational inversion as the micellar shape evolved from a sphere to an elongated ellipsoid with increasing DTAB content led to the idea of the spatial partitioning theory (SPT). The SPT attributes changes in the average conformation of the dendrimers to the change in the volume fractions of the two regions found inside the mixed micelles, between which the dendrimers partition themselves. These two regions were the polar edge region, which was made of ~ 70 charged SDS molecules, and had a curved surface and a high HG, and a more hydrophobic middle region with a lower surface curvature and a low HG formed by the remaining neutralized surfactants. The SPT provided a robust fundamental framework to predict how the average rate constant () for PEF, obtained from the MFA of the fluorescence decays acquired with the PyCX-PAMAM-G0 samples, was affected by the composition of the NSSA the dendrimers interacted with. The sensitivity of the conformational inversion of the PyC10- and PyC12-PAMAM-G0 dendrimers to their local environment shows the potential of these dendrimers as molecular probes for NSSA formed upon the addition of NaCl or DTAB to aqueous solutions of SDS micelles. Partitioning of the dendrimers with longer C10 and C12 linkers between the edge and middle regions rationalized the changes in observed as a function of salt concentration, DTAB content, or both. The generality of the SPT, which applied to all surfactant systems investigated in this thesis, provided strong support for the two regions coexisting in the NSSA, with the edge region being constituted of the same number of charged surfactants as that found in a pure SDS micelle. This insight led to a proposal for the mechanism leading to the formation of NSSA, when salt or oppositely charged surfactants are added to an SDS aqueous solution. Together, the results presented in this thesis suggest that the PyCX-PAMAM-G0 dendrimers constitute outstanding molecular probes to study NSSA in solution.
Synthesis and Analysis of Daptomycin Analogues
(University of Waterloo, 2025-09-26) Brill, Robert
Daptomycin (Dap) is a naturally occurring, membrane-active, calcium-dependent cyclic lipodepsipeptide antibiotic (cLPA) which is used as a last-resort antibiotic to treat serious infections caused by Gram-positive (G+) bacteria including Staphylococcus aureus (S. aureus) and vancomycin-resistant enterococci (VRE). The appearance of Dap-resistant (Dap-R) bacteria with increasing frequency has motivated the search for Dap analogues that are active against Dap-R bacteria. Recently, it has been shown that appending hydrophobic groups to tryptophan (Trp) or kynurenine (Kyn) yielded some Dap analogues with improved activity and were active against Dap-R bacteria. Chapter 2 of this thesis describes the synthesis and evaluation of Dap analogues with hydrophobic modifications to the side chain of the D-asparagine (Asn) residue at position 2 to determine if appending hydrophobic groups to D-Asn2 will also result in Dap analogs with improved activity. Eight Asn derivatives were synthesized containing alkyl or hydroxyl groups appended to the primary amide nitrogen of the D-Asn side chain. Dap analogues containing these D-Asn derivatives at position 2 were synthesized using Fmoc (9-fluorenylmethyloxycarbonyl) solid-phase peptide synthesis (SPPS). Dap analogs containing methyl (Me), ethyl (Et), n-propyl (Pr), n-butyl (Bu) and n-hexyl (Hex) on the D-Asn exhibited minimum inhibitory concentration (MIC) values that were 2–4-fold higher than Dap while the n-octyl (Oct) and piperidinyl (Pip) analogs had MIC values that were 8- and 32-fold greater than Dap, respectively. These results demonstrate that the activity of Dap cannot be improved by appending hydrophobic groups to D-Asn2 and suggest that D-Asn2 may not be closely associated with the cell membrane. These results also show that the primary amide of D-Asn2 is not essential for activity while the presence of at least one hydrogen on the nitrogen of the D-Asn2 side chain is very important to activity. Membrane insertion studies using model membranes and fluorescence spectroscopy revealed that the hexyl and octyl analogues were able to insert into membranes even in the absence of Ca²⁺ consistent with their much-increased hydrophobicity compared to Dap. In chapter 3, we wished to determine if it is possible to convert Dap into a Zn+2-dependent antibiotic by substituting the two aspartate (Asp) residues in Dap’s calcium-binding motif, Asp7 and Asp9, with Nγ-hydroxyasparagine (Asn(OH)), an amino acid that has a hydroxamic acid side chain. Hydroxamic acids, known for strong Zn²⁺ chelation, have been used in medicinal chemistry to improve metal-dependent interactions. The synthesis of an Asn(OH) building block with the hydroxamic acid side chain protected with a trityl (Trt) group (Fmoc-Asn(OTrt)-OH) was achieved following a multi-step route starting from Fmoc-Asp(tBu)-OH. Attempts to synthesize Dap analogues containing Asn(OH) at positions 7 or 9 using this building block via Fmoc SPPS failed. However, the synthesis of a Dap analogue containing Asn(OH) at position 2 was successful indicating that incorporation of this residue using this building block is sequence dependent. A new Asn(OH) building block containing a protecting group that is smaller than the Trt group, the dimethoxybenzyl (DMB) group (Fmoc-Asn(ODMB)-OH), was prepared. Attempts to prepare the target peptides using this new building block also failed as were attempts using an Asn(OH) building block with the hydroxamic acid side chain unprotected.
Towards the synthesis of coinage metal chalcogen compounds stabilized by a bidentate N-heterocyclic carbene
(University of Waterloo, 2025-09-26) Alex, Alice
Group 11 metal chalcogen clusters have been of interest due to their potential applications in light emitting materials. Although group 11 metal chalcogen complexes with phosphine ligands have been extensively examined and most of them reported do not contain N-heterocyclic carbene (NHC) ligand. This thesis examines how the rigid bidentate NHC, 1,1’-(dibenzyl)-3,3’-(1,2-xylylene)dibenzo[d]imidazol-2-ylidene) (bisNHCBn) can be incorporated into the gold(I) metal – chalcogenolate (chalcogenolate = RSe-; R = organic moiety) and gold(I) chalcogenide (chalcogenide = Se2-) complexes. In these studies, the chalcogen reagents Se(SiMe3)2 or RSeSiMe3 are reacted with the gold coordination complex [(AuOAc)2(bisNHCBn)] to target Au(I) selenide and Au(I) selenolate clusters with bisNHCBn. The preparation, characterization, and UV-vis absorption studies of the resulting clusters are presented.
Multimetallic Complexes Supported by an Unsymmetrical Imidazopyrimidine-Based Ligand: Synthesis, Characterization, and Catalytic Studies
(University of Waterloo, 2025-09-23) Abaeva, Mila
Bimetallic catalysts containing two metals in close proximity harness cooperative effects that enable enhanced or unique reactivity in comparison to traditional monometallic catalysts. The development of such catalysts relies on the development of binucleating ligands that support their assembly and modulate key parameters, synthetic routes to access bimetallic complexes, and continued exploration of their catalytic properties. In this regard, heterobimetallic catalysts are particularly underdeveloped due to synthetic challenges associated with incorporating two different metal centers selectively. This thesis explores the synthesis of heterobimetallic complexes using a novel unsymmetrical ligand design. In ‎Chapter 2, imidazopyrimidine-based ligands are introduced as a novel motif for binucleating ligand design. The imidazopyrimidine motif was selected for its ease of synthesis and inherently unsymmetrical nature. A representative ligand was synthesized in high yield from readily available starting materials, and the route was successfully extended to multigram scale. In ‎Chapter 3, the coordination chemistry of this ligand was investigated through the synthesis of homobimetallic complexes. Dinickel(II), dicopper(II), and dipalladium(II) complexes were prepared and characterized to assess the structural influence of the imidazopyrimidine motif. Serendipitously, trinickel(II) and tricobalt(II) complexes were also prepared and characterized, demonstrating the ability of imidazopyrimidine-based ligands to potentially accommodate variable nuclearities. Key structural features, such as the metal-metal distances, were evaluated and compared with literature complexes. ‎Chapter 4 focuses on the synthesis of heterobimetallic complexes supported by an imidazopyrimidine-based ligand. One-step syntheses of nickel(II)/copper(II) and cobalt(II)/copper(II) complexes were achieved, including both binuclear and trinuclear complexes. NMR studies revealed that the heterometallic complexes were thermodynamically favoured. Competition reactions analyzed by ESI-MS demonstrated that the selective formation of heterometallic complexes was driven in part by the preferential binding of copper(II) to one of the coordination sites on the ligand. Attempts to access other heterobimetallic combinations, including nickel(II)/palladium(II) or copper(II)/palladium(II), were unsuccessful. In ‎Chapter 5, the Glaser-Hay coupling is explored using a dicopper complex supported by an imidazopyrimidine-based ligand. Compared to related monometallic catalysts, the dicopper complex exhibited a consistently reduced reaction rate, as determined by NMR studies.
Characterizing the Occurrence and Fate of Micropollutants in Aqueous and Environmental Samples: A Multidimensional Approach
(University of Waterloo, 2025-09-09) Lemmens, Shannon
Emerging contaminants such as pharmaceuticals and per-and polyfluoroalkyl substances (PFAS) present persistent challenges for environmental monitoring due to their chemical diversity, trace-level occurrence and limited removal in conventional wastewater treatment. This thesis presents a dual approach combining experimental two-dimensional separations with computational modelling to advance contaminant detection and mechanistic understanding. A targeted liquid chromatography-mass spectrometry (LCxDMS-MS/MS) method was developed and applied to complex pharmaceutical mixtures, revealing improved compound differentiation and class-based clustering across orthogonal retention time and compensation voltage dimensions. These trends demonstrate the potential of LCxDMS-MS/MS as a selective, high-throughput workflow for micropollutant screening in aqueous matrices. Complementary to this, quantum chemical calculations were performed on PFAS molecules, specifically perfluorosulfonic acids (PFSAs), to elucidate degradation pathways and assess the influence of molecular conformation on fragmentation energetics. Calculations identified several concerted and non-concerted reaction pathways that contribute to product selectivity. Together, these efforts establish a framework that integrates instrumentation and theory to support more informed contaminant analysis and method development.
Design, construction, and operation of a compact, ultrafast 100kV electron diffraction instrument
(University of Waterloo, 2025-09-08) Netzke, Samuel
Elucidating the structure and properties of nanomaterials at greater resolutions necessitates the continuing development of novel imaging techniques. Electron imaging methods (such as electron microscopy/diffraction) are well-suited for probing matter at the nanoscale; for a given energy, the electron scattering cross-section is ~10⁵⁻⁶ higher than X-rays and ~10³ times less damaging [1]. Ultrafast electron imaging techniques are capable of spatial and temporal resolutions down to ~0.1 nm and 100 fs (femtosecond), respectively. This enables the observation of fundamental dynamic processes including photoinduced phase transitions, electron-phonon energy transfer, and the evolution of coherent phonons [2]. At present, open user access to the incredible power of these ultrafast techniques is generally limited to one ultrafast electron diffraction (UED) facility. Existing, well-established methods used to study nanomaterials such as X-ray diffraction and conventional electron microscopy have a plethora of commercially available, laboratory scale instruments which can be used to carry out experiments. In contrast, there are no similar turn-key devices that enable the study of ultrafast dynamic processes. The construction of an in-house ultrafast electron diffraction apparatus is one solution to the problem of instrument accessibility and the realization of time-demanding experiments with proper controls. In this thesis, I document the design, assembly, and use of a compact laboratory scale UED instrument. The instrument is capable of stable operation at 100 kV, with subsequent development and testing suggesting that it can reach voltages in excess of ~130 kV. The instrument is able to produce electron pulses with a temporal length of ~200 fs while containing a sufficient number of electrons for adequate signal-to-noise level. Two experiments were then carried out using the UED apparatus in order to showcase its time and spatial resolutions: electron deflection by photoinduced plasma, and the investigation of the charge density wave (CDW) material NbTe2. Analysis of the time-resolved diffraction data collected from the NbTe2 measurements suggests at 60 kV demonstrate sub-picosecond resolution in agreement with the predicted instrument response obtained from N-particle tracer simulations.
Computational Methods for Inferring the Structures of Amorphous Materials and Understanding Ionic Diffusivities
(University of Waterloo, 2025-09-05) Gouws, Xander Andrew
The simulation of solid-state electrolytes (SSEs) has allows researchers to directly observe the migration paths of lithium ions, and so has played a pivotal role in elucidating the mechanisms of ionic conduction. Performing these simulations requires three steps: Structure determination, simulation, and analysis. Here, we have developed and tested new computational methods to address key challenges in two of these steps. First, we develop a gradient-based optimization method for determining the structures of amorphous materials from total scattering data. Unlike traditional reverse Monte Carlo approaches that rely on random atomic movements and suffer from slow convergence, our gradient-based method moves atoms to directly minimize the chi-squared goodness-of-fit and potential energy. Our approach was tested on amorphous silicon and a nickel--niobium metallic glass. Convergence was achieved in on the order of 5,000 steps, which is approximately one hundred times faster than existing hybrid Monte Carlo methods. Then, we introduce a method for detecting ion hopping events in SSEs without prior knowledge of site locations. This may be useful when simulating i) new materials, for which the positions of all lithium occupancy sites may be unknown, ii) structural changes (e.g. doping) that introduce local strains that shift site positions, or iii) amorphous materials, where lithium sites may be unknown prior to simulation. Testing our method on Li6PS5Cl and its BH4-doped variant, we recover the cage-forming nature of lithium sites in argyrodite structures, and find that the correlation factor for hops between cages is greater than one, indicating a forward-bias for intercage hops.
Impact of control noise on a variational quantum eigensolver
(University of Waterloo, 2025-08-21) Wang, Xinning
Quantum computers promise advantages over classical systems for problems such as molecular simulation, fueling the development of hybrid quantum-classical algorithms like the Variational Quantum Eigensolver (VQE). VQE is particularly attractive for noisy intermediate-scale quantum (NISQ) devices due to its shallow circuit depth and partial resilience to noise. Silicon-based spin qubits, with their compatibility with existing semiconductor technologies, are strong candidates for scalable quantum computation. However, their performance is constrained by hardware imperfections—chiefly charge noise and voltage miscalibration—that manifest as fluctuations or offsets in gate electrode voltages. These disturbances degrade quantum gate fidelities and, in turn, the accuracy of algorithmic results, presenting significant challenges for practical applications. In this thesis, we develop a comprehensive hardware-algorithm co-simulation framework to quantify the impact of voltage noise on silicon quantum dot systems. Charge noise is modeled using an ensemble of random telegraph noise processes to emulate realistic 1/f-like spectra. We systematically investigate the effects of stochastic noise and systematic miscalibration at both the gate level and algorithm level. For individual quantum gates—including RX, Hadamard, CZ, and RootSWAP—we characterize noise-induced fidelity loss and derive analytical expressions for error sensitivity, revealing contrasting robustness between detuning-driven and exchange-driven gates. Quantum process tomography and Kraus operator decomposition further elucidate dominant error channels, distinguishing coherent and incoherent contributions from different noise regimes. Extending the analysis to algorithm performance, we simulate VQE for the hydrogen molecule and identify a practical noise tolerance window within which high-accuracy energy estimation is maintained. These advances underscore the progress in bridging device physics and quantum algorithm implementation for silicon spin qubits, offering quantitative guidance on error budgeting, control calibration, and the development of noise-resilient algorithms for near-term quantum processors.
Development of hydrophilic silicone-based ink for the 3D vat photopolymerization printing of biomedical devices
(University of Waterloo, 2025-08-19) Wong, Li Yan
Three-dimensional (3D) printing is a layer-by-layer additive manufacturing technique that continues to gain interest due to its ability to fabricate customized structures at low setup cost and quick turnaround time. In this thesis, advanced ink materials are developed for the fabrication of elastic biomedical devices using vat photopolymerization (VP) printing. In Chapter 1, an overview of various 3D printing techniques is presented, including their respective advantages, disadvantages, and requirements for ink material. Compared to other major 3D printing techniques, VP printing offers high printing accuracy, resolution, and superior surface quality. However, the fabrication of elastic structures using VP printing has long been a challenge due to the high viscosity and tackiness of elastomeric material. A review of various elastic materials and their current applicability in VP printing is also presented. Finally, recent materials and strategies for fabricating biomimetic implants and fluidic devices via VP printing are discussed. In Chapter 2, a VP-printable hydrophilic silicone-based material is developed, using aminosilicone methacryloyl (SilMA) incorporated with acrylamide (AA) and poly(ethylene glycol) dimethacrylate (PEGDMA) as reactive diluents. The incorporation of AA and PEGDMA addresses the issues of high pre-gel viscosity and slow curing rate of SilMA. Furthermore, the formation of a SilMA/AA/PEGDMA interpenetrating network (IPN) upon curing is novel as it differs from the existing acrylate and thiol-ene silicone network. By integrating hydrogel components, the material displayed distinct characteristics compared to conventional silicone, including hydrophilicity and good swelling properties. Additionally, compared to regular hydrogels, the material shows improved strength, elasticity, and durability suitable for the fabrication of biomimetic implants. Despite its excellent VP printability, the developed material exhibits signs of overcuring, which hinders the printing of ultra-fine features. Hence, in Chapter 3, cellulose nanocrystal (CNC) is used to improve printing accuracy and resolution. The use of CNC to tune photocuring depth is novel and, to the best of our knowledge, has not been reported in literature previously. Upon the integration of 1 wt% of CNC, the developed material exhibits a high printing accuracy and resolution down to 100 μm with a near-zero deviation in the X and Y direction. Most importantly, the incorporation of CNC results in a printed fluidic device with excellent surface detail, good fluid processibility, and minimal colour staining. Yet, with the SilMA-based material, it remains challenging to achieve one-step printing of fluidic devices with embedded channels. Therefore, in Chapter 4, ink formulation with siloxane oligomer instead of polymer is developed for an even lower pre-gel viscosity. In this ink formulation, amphiphilic siloxane oligomer (silmer) is complemented with AA and glycidyl methacrylate (GMA). The use of silmer as the primary component in resin formulations is uncommon due to the challenges in dissolving high concentrations of silmer. Herein, a novel approach using a solvent blend is introduced as a critical strategy for formulating the amphiphilic silicone-based ink materials for VP printing. Silmer conformation is solvent-dependent, resulting in tuneable pre-gel viscosity, transparency, and surface properties. Upon ink optimization, a silicone-based fluidic device with embedded channel is successfully produced with VP printing, and the printed device shows excellent capability in synthesizing drug-encapsulated hydrogel beads, demonstrating its feasibility for real-world biomedical applications. Taken all together, this thesis presents the formulation of VP-printable hydrophilic silicone-based resin material with two different strategies: (1) the addition of reactive diluents and (2) the use of lower-molecular-weight siloxane oligomers; offering new perspectives on the formulation of hydrophilic elastomeric resin material for VP printing. Furthermore, the successful fabrication of biomimetic scaffold implants and biomedical fluidic devices with VP printing reveals a significantly simpler and more cost-effective method for the fabrication of silicone-based biomedical devices, moving beyond the conventional method of soft- lithography and moulding.
Fundamental studies for small molecule aptamer selection using capture-SELEX
(University of Waterloo, 2025-08-11) Ding, Yuzhe
DNA aptamers for small molecules hold transformative promise in biosensing, diagnostics, and therapeutics, yet their in vitro evolution has been hampered by incomplete knowledge of the parameters that drive efficient enrichment. In recent years, the development of library-immobilization based method, so called capture-SELEX, has generated over 100 high-quality DNA aptamers for various types of small molecules. Importantly, capture-SELEX allows systematic investigation of fundamental problems in the selection of aptamers. This thesis studies the capture-SELEX platform by dissecting thermodynamic, kinetic, and methodological variables to accelerate the discovery of high-affinity DNA aptamers. Using adenosine/ATP as targets for selection has repeatedly produced the same guanine-rich aptamer motif that was first reported by the Szostak group in 1995. This aptamer has been considered as the adenosine/ATP aptamer by the field. First, by gradually increasing the selection stringency on classical targets (adenosine and ATP), we selected two new aptamers with Kd ≈ 230 nM, 35-fold tighter than that of the classical aptamer sequence. This was achieved through gradual reduction of target concentration from 5 mM to the low-micromolar range. The evolution of the sequence abundance cross different rounds was traced by deep sequencing, and the reason for the previous repeated report of the classical sequence was attributed to its short 12-nucleotide conserved binding regions, whereas the two new aptamers have approximately 16 conserved nucleotides. This study highlights the importance of using low target concentration in order to enrich high affinity aptamers. During aptamer selection, using a lower target concentration tends to favor the enrichment of higher affinity binders, raising the question of whether a practical lower limit exists. Next, we performed three capture-SELEX campaigns using 5 µM, 500 nM, and 50 nM guanine as the target, respectively, to investigate it. Both the 5 µM and 500 nM selections successfully enriched the same guanine aptamer-requiring eight rounds at 5 µM guanine versus 17 rounds at 500 nM guanine. However, the 50 nM selection failed to yield any aptamers. The highest affinity and most enriched aptamer from these selections displayed a Kd of 200 nM, indicating that if the target concentration is much lower than Kd can lead to failed selections. Mutation analysis further revealed a critical cytosine in the guanine binding pocket: substituting this cytosine with a thymine switched selectivity from guanine to adenine. A similar specificity switching was previously seen in the natural guanine riboswitches. These findings define a lower limit for target concentration in capture-SELEX and offer a practical guidance for selecting target levels to isolate high-affinity aptamers. Selection of high-affinity aptamers underpins all downstream applications, yet most protocols emphasize thermodynamic factors-such as target concentration-while overlooking binding kinetics. Third, we performed a library-immobilization selection against ampicillin to dissect these influences. Under typical gravity-flow conditions (1-2 min interaction), a low-affinity aptamer (Kd = 12.7 µM) dominated the enriched pool. In contrast, extending the incubation time to 10 min enriched a higher affinity sequence (Kd = 1.8 µM), differing by only three nucleotides from the weaker Kd aptamer. Systematic comparison of library immobilization efficiency, release fraction, and release kinetics confirmed that dissociation rate from the capture duplex was the primary determinant of the selection outcome. We observed the same kinetic bias in parallel adenosine selections, demonstrating the generality of this effect. Based on these findings, we recommend combining low target concentrations with extended incubation time to favor the enrichment of high-affinity aptamers. This study not only yields a robust, high affinity and selective ampicillin aptamer but also highlights a critical interplay between thermodynamics and kinetics during in vitro aptamer selection. Since 1990, numerous aptamer-selection techniques have been developed, yet quantitative comparisons of their enrichment efficiencies remain scarce. Finally, we evaluated three library‐immobilization SELEX methods, capture‐SELEX, GO‐SELEX, and gold‐SELEX, using a spiked library containing DNA aptamers with varying affinities for adenosine. Using 100 µM adenosine as target, all three methods showed that <1 % of the library was released by adenosine as revealed by qPCR, with gold‐SELEX showing virtually no DNA elution. Deep sequencing of three model aptamers (Ade1301, Ade1304, and the classical adenosine aptamer) revealed 30-50‐fold enrichment in capture-SELEX, whereas GO‐SELEX and gold‐SELEX both yielded enrichment factors below 1, indicating a lack of aptamer enrichment. Blocking the primer‐binding regions improved GO‐SELEX enrichment to ~14 % but still fell far short of capture‐SELEX’s performance. Finally, we compared nonspecific versus target‐induced release and elucidated why capture‐SELEX’s structural-switching mechanism offers superior aptamer enrichment. Overall, capture‐SELEX is a markedly more efficient strategy for isolating high‐affinity aptamers. Collectively, this work establishes a quantitative framework for capture-SELEX-balancing target concentration, kinetic control, and partitioning strategy-to reliably isolate nanomolar-class DNA aptamers for small molecules.
Exploration, Synthesis, and Characterization of Bioinspired Iron–Imide and Iron–Amide Clusters
(University of Waterloo, 2025-07-24) Shmordok, Justin
Iron-sulfur clusters with high-spin irons play a crucial role in various biological processes. These clusters are found in enzymes such as ferredoxins, aconitase, and nitrogenase, where they function as redox cofactors or active sites for catalysis. One particularly significant transformation is the reduction of atmospheric dinitrogen to ammonia, which occurs at a complex iron-sulfur cluster with core composition [MFe7S9C] where M = Mo, V or Fe. Notably, this cluster features a μ6-carbide, whose function in the cluster remains unclear. In synthetic iron-sulfur chemistry, Fe4S4 clusters have been extensively studied with various ligands and core compositions. To explore the effects of light 2p-element ligation, nitrogen anions in amide or imide motifs can be employed. Research in the Lee group has led to the synthesis of a series of iron-imide-sulfide clusters [Fe4(NtBu)nS4-nCl4]z (n = 1-4). This class of compounds extends from [Fe4S4] to [Fe4(NtBu)4] cores, with intermediate species in the series containing a mixture of imide and sulfide ligands. The [Fe4(NtBu)4] core is synthesized via the reaction of FeCl3 with two equivalents of LiNHtBu, yielding [Fe4(NtBu)4Cl4]1–, Fe4(NtBu)4Cl3(NtBu) and FeCl2(NH2tBu)2 as the primary iron-containing products, with an approximate combined in-situ yield of 50% based on starting iron content. The [Fe4(NtBu)4Cl4]1– species can be isolated in 24% yield and undergoes both chemical oxidation and reduction to form [Fe4(NtBu)4Cl4] and [Fe4(NtBu)4Cl4]2–, respectively. The [Fe4(NtBu)4Cl4]z series has been characterized using a range of spectroscopic and structural techniques to elucidate its solid-state and solution phase properties. LiNHtBu is synthesized via the lithiation of tBuNH2 with one equivalent of n-BuLi. Upon workup, this reaction affords white crystals which display an octameric ladder structure with eight molecules of LiNHtBu in the solid state. When excess tBuNH2 (ca. 1.1 equivalents) is used, a white colloidal solution forms, yielding an infinite polymeric ladder structure in the solid state. The cyclic ladder structure was determined to be the metastable polymorph and the infinite polymer ladder structure was determined to be the thermodynamic polymorph using DSC analysis and synthetic procedures. The cyclic ladder structure can be converted to the infinite polymer structure by heat or by addition of a donor ligand to catalyze the transformation The [Fe4(NtBu)S3Cl4]2– cluster is synthesized via a controlled synthetic protocol involving the formation of an iron-amide dinuclear intermediate, Fe2(μ-NHtBu)2[N(SiMe3)2]2. This intermediate arises from the protonolysis reaction of Fe[N(SiMe3)2]2 with tBuNH2. Notably, this transformation is unusual, as analogous reactions with Fe[N(SiMe3)2]2 typically proceed with ligands that are more acidic than HN(SiMe3)2. To explore the scope of this reactivity, a series of amines with varying acidity, steric hindrance and nitrogen substitution patterns were examined. The products that can form from reactivity of Fe[N(SiMe3)2]2 with amines include a mononuclear amine adduct, di– and tri–substituted dinuclear complexes and homo– and heteroleptic trinuclear complexes. The type of complex formed depended on the stoichiometry of amine to Fe[N(SiMe3)2]2 and the acidity, nitrogen substitution and steric hindrance around the nitrogen. Finally, the reduction of [Fe4(NtBu)S3(SPh)4]2– was attempted. Although reduction to the z = 3– cluster was achieved, the resulting product proved unstable in CD3CN, decomposing into a new species accompanied by thiolate release. Upon oxidation of the decomposition product, [Fe4(NtBu)S3(SPh)4]2– was regenerated, indicating that the Fe4(NtBu)S3 core likely remains intact. Further ligand tuning revealed that the use of p-methylbenzene thiolate allowed for the isolation of the reduced cluster; however, purification was hindered by its limited solubility. The synthesis of the oxidized, [Et4N][Fe4(NtBu)S3(SMes)4] cluster was achieved by oxidization of the z = 2– cluster by ferrocenium. Surprisingly, the oxidized cluster displayed a ground spin state of S = 3/2.
Variations in Laser-Induced Carbon from Structurally Varied Poly(furfuryl alcohol)
(University of Waterloo, 2025-07-17) Yip, Emily
The laser-induced graphene technique, wherein a polymer precursor is irradiated by a CO2 IR laser, provides a simple method for patterning of carbon materials like graphene or glassy carbon under ambient conditions. This is a highly attractive method of carbonization for applications in electronics and energy storage devices, and fine tuning of the laser-induced carbon’s properties is permitted by the choice of precursor. For example, glassy carbon with its disordered structure and defects is desirable for high-performance supercapacitors and so an appropriate precursor can be selected to form glassy carbon by laser irradiation instead of graphene. However, direct structure-property correlations between the precursor and the nature of the resulting laser-induced carbon as well as its quality are unclear. To investigate this, poly(furfuryl alcohol) (PFA), a glassy carbon precursor that is infamously comprised of several structural motifs aside from its monomer unit, was synthesized under a variety of reaction conditions to create three series with different key structural features and then laser irradiated to analyze the resulting carbon material. Typical laser-induced carbon formed from PFA is more akin to glassy carbon, though varied lasing parameters and structures can potentially enable graphenization. Three series of PFA were prepared which exhibit varying degrees of polymerization, extents of ring opening, and high thermal stability. The PFA chemistry had a notable influence on the quality of the resulting laser-induced carbon, which demonstrated a broad range of ordering from an amorphous structure to that with more crystalline graphitic domains. Correlations between the PFA structure and laser-induced carbon quality showed that the most ordered carbon material formed when the PFA crosslinking was minimal and had high thermal resistance. Further structural engineering of the PFA with these properties may then enable laser-induced graphenization of the precursor.

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