<div>Laser-to-composite interactions are becoming increasingly common in diverse applications such as diagnostics, fabrication and machining, and weapons systems. Lasers are capable of not only performing non-contact diagnostics, but also inducing seemingly imperceptible structural damage to materials. In safety-critical venues like aerospace, automotive, and civil infrastructure where composites are playing an increasingly prominent role, it is desirable to have means of sensing laser exposure on a composite material. Self-sensing materials may be a powerful method of addressing this need. Herein, we present an exploratory study on the potential of using changes in electrical measurements as a way of detecting laser exposure to a carbon nanofiber (CNF)-modified glass fiber/epoxy laminate. CNFs were dispersed in liquid epoxy resin prior to laminate fabrication via hand layup. The dispersed CNFs form a three-dimensional conductive network which allows for electrical measurements to be taken from the traditionally insulating glass fiber/epoxy material system. It is expected that damage to the network will disrupt the electrical pathways, thereby causing the material to exhibit slightly higher resistance. To test laser sensing capabilities, a resistance baseline of the CNF-modified glass fiber/epoxy specimens was first established before laser exposure. These specimens were then exposed to an infra-red laser operating at 1064 nm, 35 kHz, and pulse duration of 8 ns. The specimens were irradiated for a total of 20 seconds (4 exposures each at 5 seconds). The resistances of the specimens were then measured again post-ablation. In this study, it was found that for 1.0 wt.% CNF by weight the average resistance increased by about 18 percent. However, this values varied for specimens with different weight fractions. This established that the laser was indeed causing damage to the specimen sufficient to evoke a change in electrical properties. In order to expand on this result, electrical impedance tomography (EIT) was employed for localization of laser exposures of 1, 3, and 5 seconds on a larger specimen, a 3.25” square plate. EIT was used to measure the changes in conductivity after each exposure. EIT was not only successful in detecting damage that was virtually imperceptible to the human-eye, but it also accurately localized the exposure sites. The post-ablation conductivity of the exposure sites decreased in a manner that was comparable to the resistance increase obtained during prior testing. Based on this preliminary study, this research could lead to the development of a real-time exposure detection and tracking system for the measurement, fabrication, and defense industries.</div>

<p dir="ltr">Metamaterials are artificially engineered nanoscale systems with a three-dimensional repetitive arrangement of certain components, and present exceptional optical properties for applications in nanophotonics, solar cells, plasmonic devices, and more. Self-assembled oxide-metal vertically aligned nanocomposites (VANs), with metallic phase as nanopillars embedded in the matrix oxide, have been recently proposed as a promising candidate for metamaterial applications. However, precise microstructural control and the structure-property relationships in VANs are still in high demand. Thus, by employing multiple approaches for structural design, this dissertation attempts to investigate the mechanisms of nanostructure evolutions and the corresponding optical responses.</p><p dir="ltr">In this dissertation, the precise control over the nanostructures has been demonstrated through morphology tuning, nanopillar orderings, and strain engineering. Firstly, Au, a well-known plasmonic mediator, has been selected as the metallic phase that forms nanopillars. Based on the previously proposed strain compensation model which describes the basic formation mechanism of VAN morphology, two oxides were then considered: La_0.7Sr_0.3MnO₃(LSMO) and CeO₂. In the first two chapters of this dissertation, LSMO was considered due to its similar lattice (a_LSMO= 3.87 Å, a_Au= 4.08 Å) and its enormous potential in nanoelectronics and spintronics. Deposited on SrTiO₃ (001) substrate through pulsed laser deposition (PLD), LSMO-Au nanocomposites exhibit ideal VAN morphology as well as promising hyperbolic dispersions in response to the incident illuminations. By substrate surface treatment of annealing at 1000°C, and variation of STO substate orientations from (001), to (111) and (110), the improved and tunable in-plan orderings of Au nanopillars have been successfully achieved. In the third chapter, a new oxide-metal VAN system of <a href="" target="_blank">CeO₂</a>-Au (a_CeO2= 5.411 Å, and a_CeO2/= 3.83 Å) has been deposited. The intriguing 45° rotated in-plan epitaxy presents an unexpected update to the strain compensation model, and tuning of Au morphology from nanopillars, nanoantennas, to nanoparticles also shows an effective modulation of the LSPR responses. COMSOL simulations have been exploited to reveal the relationships between Au morphologies and optical responses. In the last chapter, the two VAN systems of LSMO-Au and CeO₂-Au have been combined to form a complex layered VAN thin film. Investigations into the strain states, the nature of complex interfaces, and the according hybrid properties, show dramatic possibilities for further strain engineering. In summary, this dissertation has provided multiple routes for highly tailorable oxide-metal nanocomposite designs. And the two proposed material systems present great potential in optical metamaterial applications including biosensors, photovoltaics, super lenses, and more.</p>

<p dir="ltr">The gastrointestinal (GI) tract and its diverse microbial community play a significant role in overall health, impacting various aspects such as metabolism, physiology, nutrition, and immune function. Disruptions in the gut microbiota have been associated with metabolic diseases, colorectal cancer, diabetes, obesity, inflammatory bowel disease, Alzheimer's disease, and depression. Despite recognizing the importance of the gut microbiota, the interrelationship between microbiota, diet, and disease prevention remains unclear. Current techniques for monitoring the microbiome often rely on fecal samples or invasive endoscopic procedures, limiting the understanding of spatial variations in the gut microbiota and posing invasiveness challenges. To address these limitations, this dissertation focuses on the design and development of an electronic-free smart capsule platform capable of targeted sampling of GI fluid within specific regions of the GI tract. The capsule can be retrieved for subsequent bacterial culture and sequencing analysis. The capsule design is based on stimuli-responsive polymers and superabsorbent hydrogels, chosen for their proven safety, compatibility, and scalability. By leveraging the pH variation across the GI tract, the pH-sensitive polymeric coatings dissolve at the desired region, activating the sampling process. The superabsorbent hydrogel inside the capsule collects the sampled GI fluid and facilitates capsule closure upon completion of sampling. Systematic studies were conducted to identify suitable pH-responsive polymer coatings, superabsorbent hydrogels, and processing conditions that effectively operated within the physiological conditions of the GI tract. The technology's effectiveness and safety were validated through rigorous <i>in vitro</i> and <i>in vivo</i> studies using pig models. These studies demonstrated the potential of the technology for targeted sampling of GI fluid in both small and large intestinal regions, enabling subsequent bacterial culture and gene sequencing analysis. Additionally, the capsule design was enhanced with the integration of a metal tracer, enabling traceability throughout the GI tract using X-ray imaging and portable metal detectors for ambulatory screening. This technology holds promise as a non-invasive tool for studying real-time metabolic and molecular interactions among the host, diet, and microbiota in challenging-to-access GI regions. Its application in clinical studies can provide new insights into diet-host-microbiome interactions and contribute to addressing the burden faced by patients and their families dealing with GI-related diseases.</p>

<p dir="ltr">Energetic materials (EMs) manufacturing practices have evolved little since the First and Second World Wars. Because of this, a substantial focus has recently been placed on modernizing the processes used in the production of these materials to mitigate the risk of human error and prevent the potentially fatal, and costly, consequences that exist when accidents take place. In this work, a piezoelectrically actuated inkjet printer system was used to deposit functional materials onto the surfaces of mock and live polymer-bonded EMs. The benefit to this is two-fold: (1) the material can safely be deposited remotely, %mention human error? and (2) this high resolution method of printing can open the door to novel applications, allowing for functional elements to be integrated directly with the material. To start, composite formulation and mixing parameters were studied on a variety of mixers to better inform substrate preparation and the role that these parameters may play in a variety of substrate material properties, including local internal composition, density, quasi-static compression, and surface topography. From here, the topography and surface free energy of the surface of these materials was analyzed further to better inform ink formulation and selection. Upon observing the ink behavior at the interface, print parameters were chosen that supported the creation of continuous architectures that could function in a variety of capacities, including as resistance probes, strain gauges, heaters, spark gap igniters, and antennas.</p>

Diese Arbeit zielt darauf ab, Struktur-Aktivitäts-Korrelationen zu untersuchen, indem die Zusammensetzungen von Au25-Nanoclustern auf atomarer Ebene manipuliert werden. Die Liganden der Au25-Nanocluster wurden zunächst so konstruiert, dass geeignete Liganden für Anwendungen in der Lichtumwandlung gefunden werden konnten, wobei vier verschiedene Au25-Nanocluster mit ähnlichen Metallkernstrukturen synthetisiert wurden. Photoelektrochemische Messungen wurden durchgeführt, um die Sensibilisierungsfähigkeiten dieser Nanocluster durch Abscheidung auf anatas TiO2-Substraten zu vergleichen. Quantenchemische Berechnungen wurden durchgeführt, um den Einfluss der schützenden Liganden auf die Photoaktivitäten zu untersuchen. Danach wurden die Nanocluster mit optimalen Photoaktivitäten weiterhin zur Erforschung der photocatalytischen Eigenschaften verwendet. Da Metallsites im Allgemeinen als aktive Zentren für heterogene Katalyse betrachtet wurden, wurden die Legierungseffekte des Metallkerns untersucht, indem Ag-Atome darin eingebaut wurden. Die Und die photokatalytische Wasserstoffentwicklung wurde als Referenzreaktion für die Erforschung des Metallkerns verwendet. Eine graduelle Einstellung der Metallzusammensetzung des Metallkerns wurde erreicht, die einen vulkanartigen Trend zur Wasserstoffentwicklung zeigte. Ab-initio-Berechnungen wurden verwendet, um die Beziehung zwischen der Metallzusammensetzung und den katalytischen Aktivitäten zu korrelieren. Darüber hinaus wurden die zentral, mono-dotierten Ag25-Nanocluster mit Heteroatomen der Gruppe VIII ebenfalls untersucht. Obwohl die gestaffelten Energieniveaus zwischen den Nanoclustern und dem Substrat die Wasserstoffproduktionsraten des gesamten Photokatalysesystems erheblich förderten, verschlechterten die Dotierung von Heteroatomen in den innersten Kern die photokatalytischen Aktivitäten der Nanocluster. / This work aims at studying structure-activity correlations by engineering the compositions of Au25 nanoclusters at atomic level. The ligands of Au25 nanoclusters were first engineered to determine suitable ligands for light conversion, where four different Au25 nanoclusters with similar core metal structures were synthesized. Photoelectrochemical measurements were employed to compare the sensitization capabilities of these nanoclusters by depositing them onto anatase TiO2 substrates. Quantum chemical calculations were carried out to investigate the impact of protecting ligands on photoactivities. After that, the nanoclusters with optimum photoactivities were further used to explore the photocatalytic properties. Since metal sites were generally considered active centers for heterogeneous catalysis, the alloying effects of the metal core were studied by incorporating Ag atoms into it. And photocatalytic hydrogen evolution was used as a touch stone reaction for exploring the metal core. Gradient tuning of metal composition of the metal core had been achieved, which exhibited a volcanic-like trend toward hydrogen evolution. Ab initio calculations were employed to correlate the relationship between the metal composition and catalytic activities. In addition, the centrally, mono-doped Ag25 nanoclusters with group-VIII heteroatoms were also studied. Although the staggered energy levels between the nanoclusters and the substrate greatly promoted the hydrogen production rates of the whole photocatalysis system, the heteroatoms doping into the innermost core deteriorated the photocatalytic activities of the nanoclusters.

<p dir="ltr">For reliable, facile, and user-friendly, solution-based synthesis of materials, the colloidal nanocrystal route has proven to be the method of choice for so many. The tunability that this process renders its users---from choice of precursors, solvent systems, and reaction conditions including temperature, pressure, and precursor addition order---is truly second to none. In their simplest form, these nanomaterials are usually comprised of an inorganic core of the desired material and an outer layer of surface-stabilizing molecules called ligands. These ligands provide colloidal stability and allow for the solution-processing of these materials for downstream usage in devices such as light-emitting diodes and photovoltaics, for example. In this thesis, the study and use of colloidal nanomaterials of Cu(In,Ga)(S,Se)₂ (CIGSSe), IIA-IVB-S₃ (including BaZrS₃ and SrZrS₃), alkaline earth polysulfides (IIAS_x; IIA = Sr, Ba; x = 2, 3), and other materials like Cu₂GeS₃ and Cu₂BaSnS₄, for studies into the formation, colloidal stability, and fabrication into solar cells was performed.</p><p dir="ltr">More specifically, an experimental protocol was developed to fabricate high-quality CIGSSe nanoparticles with carbonaceous residues that are substantially reduced from traditional pathways. Traditional methods for synthesizing colloidal CIGS NPs often utilize heavy, long-chain organic species to serve as surface ligands which, during annealing in a Se/Ar atmosphere, leave behind an undesirable carbonaceous residue in the film. In an effort to minimize these residues, N-methyl-2-pyrrolidone (NMP) was used as an alternative surface ligand. Through the use of the NMP-based synthesis, a substantial reduction in the number of carbonaceous residues was observed in selenized films. Additionally, the fine-grain layer at the bottom of the film, a common observation of solution-processed films from organic media, was observed to exhibit a larger average grain size and increased chalcopyrite character over those of traditionally prepared films, presumably as a result of the reduced carbon content, allowing for superior growth. As a result, a gallium-free CuIn(S,Se)₂ device was shown to achieve power-conversion efficiencies of over 11% as well as possessing exceptional carrier generation capabilities with a short-circuit current density (J_SC) of 41.6 mA/cm², which is among the highest for the CIGSSe family of devices fabricated from solution-processed methods. It was shown that pre-selenized films of sulfide nanoparticles instead of selenide nanoparticles performed better as solar cells. While the exact mechanism is still under debate, it appears that the growth phase during selenization, which varies depending on the chalcogen present in the starting material plays an important role.</p><p dir="ltr">The IIA-IVB-S₃ system is just beginning to emerge as a material system shown to be capable of solution-based synthesis methods. This is primarily due to the extremely high oxophilicity of the IVB elements, Ti, Zr, and Hf, necessitating that extreme care and judicial use of inert environments be used to synthesize these materials via solution-based methods. In the IIA-IVB-S₃ system exists some of the chalcogenide perovskites, including BaZrS₃, which are expected to have similar electronic properties to the well-known, high-performing halide perovskites, albeit much more stable, making them attractive prospects as novel semiconductor materials for optoelectronic applications. This work builds upon recent studies to show a general synthesis protocol, involving the use of carbon disulfide insertion chemistry to generate highly reactive precursors, that can be used towards the colloidal synthesis of numerous nanomaterials in the IIA-IVB-S₃ system, including BaTiS₃, BaZrS₃, BaHfS₃, α-SrZrS₃ and α-SrHfS₃. Additionally, we establish a method to reliably control the formation of the BaZrS₃ perovskite, a complication seen in previous literature where BaZrS₃ appears to exist as two different phases when synthesized via colloidal methods. The utility of these nanomaterials is also assessed via the measurement of their absorption properties and in the form of highly stable colloidal inks for the fabrication of homogenous, crack-free thin films of BaZrS₃. In addition to the chalcogenide perovskites, the IIA-S system was also explored to better understand the solution-based formation of these materials and how the control of IIA polysulfides can be achieved. We show that the synthesis of these materials is strongly correlated to the reaction temperature and that the length of the S_n^2- oligomer chain is the dependent variable. We also report on the synthesis of a previously unreported polymorph of SrS₂ which appears to take on the <i>C2/c</i> space group, the same as BaS₂.</p><p dir="ltr">Finally, some discussion is also provided on the use of transmission electron microscopy (TEM) to analyze the crystal structure of materials. Some tips and techniques used throughout this thesis are summarized in this section.</p>

Traditional fabrication methods used to manufacture biosensors for physiological, therapeutics, or health monitoring purposes are complex and rely on costly materials, which has hindered their adoption as single-use medical devices. The development of a new kind of wearable and implantable electronics relying on inexpensive materials for their manufacturing will pave the way towards the ubiquitous adoption of sticker-like health tracking devices.<div>One of growing and most promising applications for biosensors is the continuous health monitoring using mechanically soft, stretchable sensors. While these healthcare devices showed an excellent compatibility with human tissues, they still need highly trained personnel to perform multi-step, prolonged fabrication for several functioning layers of the device. In this dissertation, I propose low-cost, scalable, simple, and rapid manufacturing techniques to fabricate multifunctional epidermal and implantable sensors to monitor a range of biosignals including heart, muscle, or eye activity to characterizing of biofuids such as sweat. I have also used these devices as an implant to provide heat therapy for muscle regeneration and optical stimulation of neurons using optogenetics. These devices have also combined with those of triboelectric<br>nanogenerators to realize self-powered sensors for monitoring imperceptible mechanical biosignals such as respiratory and pulse rate.</div><div>Food health and safety has also emerged as another important frontier to develop biosensors and improve the human health and quality of life. The recent progresses on detecting microbial activity inside foods or their packages rely on development of highly functional materials. The existing materials for fabrication of food sensors, however,<br>are often costly and toxic for human health or the environment. In this dissertation, I proposed biocompatible food sensors using protein/PCL microfibers to reinforce the protein microfibrous structure in humid conditions and exploit their excellent hygroscopic properties to sense biogenic gas, as an indicator for early detection of food spoilage. Finally, my battery-free food sensors are capable of monitoring food safety with no need of extra measurement devices. Collectively, this dissertation proposes cost-effective solutions to solve human health issues, enabled by developing low-cost, functional materials and exploiting simple fabrication techniques.<br></div>

Existing methods for pathogen/pollutant detection or wound infection monitoring employ high-cost instruments that could only be operated by trained personnel, and costly device-based detection requires a time-consuming field-to-lab process. This expensive process with multiple prerequisites prolongs the time that patients must wait for a diagnosis. Therefore, improved methods for point-of-care biosensing are necessary. In this study, we aimed to develop a direct, easy-to-use, portable, low cost, highly sensitive and selective sensor platform with the goal of pollutant detection and wound infection/cancer migration monitoring. This study has two main parts, including microfluidic, electrical, and optical sensing platforms. The first part, including chapters 2, 3, and 4, focuses on Bisphenol A (BPA) lateral flow assay (LFA) detection; the second part, including chapter 5 focuses on the electrical sensing platform fabrication for one of the markers of inflammation, matrix metalloproteinases-9 (MMP-9), monitoring/detection. In chapters 2, 3, and 4, we found that the few lateral flow assays (LFAs) established for detecting the endocrine-disrupting chemical BPA have employed citrate-stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, in chapter 2, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. In chapter 3, we describe the development of a new range-extended bisphenol A (BPA) detection method that uses a surface enhanced Raman scattering lateral flow assay (SERS-LFA) binary system. In chapter 4, we examine advanced bisphenol A (BPA) lateral flow assays (LFAs) that use multiple nanosystems. The assays include three nanosystems, namely, gold nanostars, gold nanocubes, and gold nanorods, which are rarely applied in LFAs, compared with general gold nanoparticles. The developed LFAs show different performances in the detection of BPA. In chapter 5, a stable electrical sensing platform is developed for MMP-9 detection.

Abstract : The objectives of this work were to prepare and characterize films of benzylic amide macrocycles and rotaxanes obtained by functionalisation of an acidterminated self-assembled monolayer (SAM) on gold, and thus to probe the aptitude of these surfaces for applications in the field of the nanotechnologies. We initially studied the self-assembled monolayer of 11-mercaptoundecanoic acid and focused on its composition, structure and organization. We show that the molecules of alcanethiol are oriented with the acid group pointing out from the surface. The film is highly ordered with defect density below 0.2%. We investigated the functionalisation process with the covalently bound Mac-OH macrocycle, with the physisorbed Mac-pyridine macrocycle and with the naphtalimide rotaxane. The latter is also anchored to the SAM through a non-covalent interaction. We focused on the comprehension of both quantitative as qualitative characteristics of the films, such as the degree of functionalisation, their stability with respect to external constraints, their order and homogeneity, their structure and their orientation. By combining techniques such as X-ray photoemission spectroscopy, infrared reflection-absorption spectroscopy, atomic force microscopy, electrochemical and contact angle measurements, we demonstrated that the films of macrocycles reach a high degree of functionalisation. The layers are homogeneous and a preferential orientation of the macrocycle molecules with the plan of the ring tilted with respect to the surface and with the alkyl chains pointing-out from the films is observed. In addition, we studied the possibility of using the macrocycle films for molecular recognition, employing the Fc-Gly-Gly molecule as a model target. Through similar experiments and analysis, films of naphtalimide rotaxane were proven to give a good functionalisation of SAM. The molecule adsorbs with a preferential orientation of the linear axis parallel to the surface and the macrocycle unit normal to it. We characterized the fluorescent properties of the molecule due to the naphtalimide group and showed that when adsorbed on a gold substrate the presence of the self-assembled monolayer prevents total quenching. <br> Résumé : Les objectifs de ce travail étaient de caractériser des films de macrocycles et de rotaxanes de type amide benzylique obtenus par la fonctionnalisation de monocouches auto-assemblées d'alcanethiols, ayant un groupe acide terminal, sur une surface d'or, et ainsi de mettre en évidence certaines des potentialités de ces surfaces en vue d'applications éventuelles dans le domaine des nanotechnologies. Nous avons d'abord étudié la monocouche auto-assemblée de l'acide 11-mercaptoundecanoïque et particulièrement les aspects tels que la composition, la structure et l'organisation du film et nous avons mis en évidence que les molécules d'alcanethiol sont orientées dans le film avec le groupe acide vers l'extérieur de la surface, de façon à pouvoir interagir avec les molécules à greffer, et que le degré d'ordre de la monocouche est très élevé, en montrant celle-ci une fraction de défauts inférieure au 0.2% de l'aire totale du film. L'étude de la fonctionnalisation successive avec le macrocycle Mac-OH, lié de façon covalente, et le macrocycle Mac-pyridine ainsi que la rotaxane naphtalimide, ancrés à travers une interaction non-covalente à la monocouche auto-assemblée, a porté une attention particulière à la compréhension d'aspects tels que le degré de recouvrement de la surface, la stabilité vis-à-vis de contraintes externes, l'ordre et l'homogénéité, ainsi que la structure des films et l'orientation des molécules. Grâce à la combinaison de techniques telles que l'XPS, l'IRAS, les techniques électrochimiques, les mesures d'angle de contact et l'AFM, nous avons mis en évidence que les films de macrocycle atteignent un recouvrement élevé et homogène de la monocouche autoassemblée et qu'une orientation des molécules de macrocycle, avec une inclinaison du plan de l'anneau par rapport à la surface et pointant leurs chaînes alkyles vers l'extérieure du film, est observée. Ensuite, nous avons abordé la possibilité d'impliquer les films de macrocycle en tant que récepteurs moléculaires d'une molécule modèle, la Fc-Gly-Gly. Par une caractérisation similaire, les films de la rotaxane naphtalimide ont montré d'atteindre un recouvrement élevé de la surface de la monocouche avec une orientation privilégiée des molécules avec l'axe parallèle et le macrocycle perpendiculaire à la surface pour pouvoir interagir, à travers les fonctions pyridine du macrocycle, avec la monocouche. De plus, nous avons caractérisé les propriétés fluorescentes de la molécule, résidantes dans son groupe naphtalimide, lorsqu'elle est adsorbée sur un substrat métallique, l'or, affectées par la présence de la monocouche auto-assemblée.

First principle electronic structure theory is used to describe the effect of crystal binding on radiation detectors, electron transport properties, and structural damage induced by intense irradiation. A large database containing general electronic structure results to which data mining algorithms can be applied in the search for new functional materials, a case study is presented for scintillator detector materials. Inelastic cross sections for the generation of secondary electron cascades through impact ionization are derived from the dielectric response of an electron gas and evolved in time with Molecular Dynamics (MD). Qualitative and quantitive estimates are presented for the excitation and relaxation of a sample irradiated with Free Electron Laser pulses. A study is presented in where the structural damage on covalent bonded crystals following intense irradiation is derived from a Tight Binding approach and evolved in time with MD in where the evolution of the sample is derived from GW theory for the quasiparticle spectra and a dedicated Boltzmann transport equation for the impact ionization.