cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.7274/25537249
title: Development of Yeast-Based Measurement Methods for Detecting Bioavailable Nutrients

description: Preventing eutrophication of inland freshwater ecosystems requires quantifying the excess nutrient (i.e., phosphorus (P) and nitrogen (N)) content of the streams and rivers that feed them. Identification of these at-risk waterways will help prevent harmful algae blooms that make drinking water unsafe. Here we present a novel method for measuring the more relevant bioavailable P (BAP). Where typical methods for measuring P assess soluble reactive P (SRP) or total P (TP) and require expensive analytical techniques that produce hazardous waste, this assay utilizes the growth of familiar baker’s yeast, avoids production of hazardous waste, and reduces cost relative to measurements of SRP and TP. The yeast BAP (yBAP) assay takes advantage of the observation that yeast density at saturating growth increases linearly with provided P. We show that this relationship can be used to measure P in freshwater in concentration ranges relevant to eutrophication. In addition, we measured yBAP in water containing a known amount of fertilizer and in samples from agricultural waterways. We observed that the majority of yBAP values were between those obtained from standard SRP and TP measurements, demonstrating that the assay is compatible with real-world settings. To expand the yBAP assay, we developed two additional derivatives for use with turbid samples that utilize the fact that growing cultures produce the gas carbon dioxide. The first derivative directly measures the released carbon dioxide by measuring pressure build-up in a closed culture chamber. The second derivative indirectly measures carbon dioxide release by measuring pH in the headspace (space above the yeast culture in a
closed system) as indicated by the color of a gel containing cresol red suspended above the liquid culture. In either case, the amount of P in a sample can be determined by comparing the observed result to standard curves constructed from solutions of known P concentration. These new variants of the assay allow for the detection of yBAP in turbid (sediment-laden) or soil samples due to their readouts not requiring measurement through the sample matrix itself but rather above it. The final portion of this thesis focuses on applying the same principles of growth to measure the excess nutrient nitrogen, a large component of eutrophication of saltwater systems, using the yeast strain Blastobotrys adeninivorans, which is capable of metabolizing more complex forms of N. In either system the cost-effective and nonhazardous nature of yeast-based assays suggests that they could have utility in a range of settings, offering added insight to identify water systems at risk of eutrophication.
DOI: 10.7274/25537249.v1
title: Development of Yeast-Based Measurement Methods for Detecting Bioavailable Nutrients

description: Preventing eutrophication of inland freshwater ecosystems requires quantifying the excess nutrient (i.e., phosphorus (P) and nitrogen (N)) content of the streams and rivers that feed them. Identification of these at-risk waterways will help prevent harmful algae blooms that make drinking water unsafe. Here we present a novel method for measuring the more relevant bioavailable P (BAP). Where typical methods for measuring P assess soluble reactive P (SRP) or total P (TP) and require expensive analytical techniques that produce hazardous waste, this assay utilizes the growth of familiar baker’s yeast, avoids production of hazardous waste, and reduces cost relative to measurements of SRP and TP. The yeast BAP (yBAP) assay takes advantage of the observation that yeast density at saturating growth increases linearly with provided P. We show that this relationship can be used to measure P in freshwater in concentration ranges relevant to eutrophication. In addition, we measured yBAP in water containing a known amount of fertilizer and in samples from agricultural waterways. We observed that the majority of yBAP values were between those obtained from standard SRP and TP measurements, demonstrating that the assay is compatible with real-world settings. To expand the yBAP assay, we developed two additional derivatives for use with turbid samples that utilize the fact that growing cultures produce the gas carbon dioxide. The first derivative directly measures the released carbon dioxide by measuring pressure build-up in a closed culture chamber. The second derivative indirectly measures carbon dioxide release by measuring pH in the headspace (space above the yeast culture in a
closed system) as indicated by the color of a gel containing cresol red suspended above the liquid culture. In either case, the amount of P in a sample can be determined by comparing the observed result to standard curves constructed from solutions of known P concentration. These new variants of the assay allow for the detection of yBAP in turbid (sediment-laden) or soil samples due to their readouts not requiring measurement through the sample matrix itself but rather above it. The final portion of this thesis focuses on applying the same principles of growth to measure the excess nutrient nitrogen, a large component of eutrophication of saltwater systems, using the yeast strain Blastobotrys adeninivorans, which is capable of metabolizing more complex forms of N. In either system the cost-effective and nonhazardous nature of yeast-based assays suggests that they could have utility in a range of settings, offering added insight to identify water systems at risk of eutrophication.
DOI: 10.7274/25541074
title: Energy Transfer from Metal Halide Perovskites: Insights for Solar Energy Harvesting

description: Harvesting solar energy is essential for meeting the increasing global energy demand driven by population growth. Inspired by natural photosynthesis, solar energy is harnessed for both electricity production (photovoltaics) and fuel generation (photocatalysis). Semiconductor nanomaterials have emerged as key light absorbers for photovoltaic and photocatalytic applications. The semiconductor nanomaterials are coupled with chromophores and other cocatalysts to facilitate charge/energy transfer for efficient light harvesting. Of particular interest is the energy transfer process, wherein semiconductor nanocrystals can populate the singlet and triplet states of the acceptor, each with its own distinct utility. Moreover, this energy transfer process can initiate nonlinear processes, further enhancing energy utilization. This dissertation elucidates the mechanisms underlying the energy transfer processes in a semiconductor-molecule hybrid assembly. 
As a model system, cesium lead halide perovskite as the sensitizer and rubrene and DBP (a perylene derivative) as acceptor chromophores are selected. Lead halide perovskites are particularly appealing as sensitizers due to their strong light absorption and tunable optical properties. Understanding the spectral characteristics of transient excited states in acceptor molecules is crucial for distinguishing between singlet/triplet energy transfer and charge transfer processes. We elucidated the spectroscopic signatures of singlet, triplet, radical anion, and radical cation of rubrene and DBP through a combination of spectroscopic and electrochemical techniques. The ambiguity surrounding the interactions between rubrene and DBP posed challenges for the application of these systems. However, we have demonstrated that DBP efficiently extracts singlet energy from rubrene.
A semiconductor-chromophore assembly was crafted utilizing cesium lead halide nanocrystals along with rubrene and DBP. In the cesium lead bromide-multichromophore assembly, sequential energy transfer was observed. Initially, singlet energy transfers from cesium lead bromide to rubrene, followed by a subsequent transfer from rubrene to DBP. This cascade of energy transfer showcases a down-conversion of energy, exemplifying the potential of semiconductor-multichromophore assemblies in energy manipulation. Conversely, in cesium lead iodide-rubrene assembly, triplet energy transfer was observed.
Finally, the triplet-triplet annihilation process in rubrene-DBP system was demonstrated. Through the cesium lead iodide-rubrene-DBP assembly, the energy can be upconverted. Taken together the projects detailed in this dissertation provide important insights into understanding the mechanism of interactions in semiconductor-chromophore assembly. Additionally, the experimental techniques and methodologies outlined herein can serve as versatile tools for identifying and comprehending interactions within semiconductor-chromophore assemblies more broadly.
DOI: 10.7274/25541074.v1
title: Energy Transfer from Metal Halide Perovskites: Insights for Solar Energy Harvesting

description: Harvesting solar energy is essential for meeting the increasing global energy demand driven by population growth. Inspired by natural photosynthesis, solar energy is harnessed for both electricity production (photovoltaics) and fuel generation (photocatalysis). Semiconductor nanomaterials have emerged as key light absorbers for photovoltaic and photocatalytic applications. The semiconductor nanomaterials are coupled with chromophores and other cocatalysts to facilitate charge/energy transfer for efficient light harvesting. Of particular interest is the energy transfer process, wherein semiconductor nanocrystals can populate the singlet and triplet states of the acceptor, each with its own distinct utility. Moreover, this energy transfer process can initiate nonlinear processes, further enhancing energy utilization. This dissertation elucidates the mechanisms underlying the energy transfer processes in a semiconductor-molecule hybrid assembly. 
As a model system, cesium lead halide perovskite as the sensitizer and rubrene and DBP (a perylene derivative) as acceptor chromophores are selected. Lead halide perovskites are particularly appealing as sensitizers due to their strong light absorption and tunable optical properties. Understanding the spectral characteristics of transient excited states in acceptor molecules is crucial for distinguishing between singlet/triplet energy transfer and charge transfer processes. We elucidated the spectroscopic signatures of singlet, triplet, radical anion, and radical cation of rubrene and DBP through a combination of spectroscopic and electrochemical techniques. The ambiguity surrounding the interactions between rubrene and DBP posed challenges for the application of these systems. However, we have demonstrated that DBP efficiently extracts singlet energy from rubrene.
A semiconductor-chromophore assembly was crafted utilizing cesium lead halide nanocrystals along with rubrene and DBP. In the cesium lead bromide-multichromophore assembly, sequential energy transfer was observed. Initially, singlet energy transfers from cesium lead bromide to rubrene, followed by a subsequent transfer from rubrene to DBP. This cascade of energy transfer showcases a down-conversion of energy, exemplifying the potential of semiconductor-multichromophore assemblies in energy manipulation. Conversely, in cesium lead iodide-rubrene assembly, triplet energy transfer was observed.
Finally, the triplet-triplet annihilation process in rubrene-DBP system was demonstrated. Through the cesium lead iodide-rubrene-DBP assembly, the energy can be upconverted. Taken together the projects detailed in this dissertation provide important insights into understanding the mechanism of interactions in semiconductor-chromophore assembly. Additionally, the experimental techniques and methodologies outlined herein can serve as versatile tools for identifying and comprehending interactions within semiconductor-chromophore assemblies more broadly.
DOI: 10.7274/25545646
title: Development of Analytical Methods and Machine Learning Platforms for Assessing the Quality of Pharmaceuticals and Drugs of Abuse

description: In low and middle-income countries (LMICs), the prevalence of counterfeit medicines, estimated at 1 in 10 pharmaceuticals, underscores the urgent need for quick and affordable presumptive analytical screening tools to mitigate the dangers associated with counterfeit drugs.
This research aims to tackle the challenges in pharmaceutical quality control and post-market surveillance by addressing the limitations of conventional predictive models and exploring the potential of non-brand-specific strategies. Traditional predictive models, often trained on libraries of authentic products, encounter difficulties in identifying quality issues in products beyond their training set. To overcome this, the research employs non-brand-specific strategies, utilizing lab-formulated samples correlated with high-performance liquid chromatography (HPLC) standards as a presumptive analytical method for post-market pharmaceutical screening, assessed through systematic metrics.
The study probes the effectiveness of Paper Analytical Devices (PADs) in discerning the active pharmaceutical ingredient (API) in over 20 antibiotic medicines. Leveraging chemical reactions to produce a unique color pattern, PADs are trained through machine learning predictive models to detect substandard formulations in the field. Despite their high sensitivity, PADs face challenges with specificity when dealing with APIs sharing identical functional groups. In response, the research investigates the integration of PADs with spectroscopic analytical techniques, creating an orthogonal analytical approach aimed at developing a robust technology for reliably detecting substandard and falsified medicines.
External factors, including variations in formulations, excipients, capsule type, color, and instrumental design/device fabrication, significantly influence pharmaceutical analysis. The research highlights the impact of capsule composition on spectroscopic analytical techniques, such as Near-Infrared (NIR) modeling. Factors like capsule type, color, or thickness introduce variance in NIR spectra comparable to the variance resulting from the type of API stored within the capsules. Recognizing and accounting for these external factors are essential for accurate and reliable analysis.
Furthermore, the research addresses a critical financial challenge in low and middle-income countries (LMICs) by introducing a cost-saving technique for achieving a more robust post-market surveillance. HPLC, while a powerful analytical method, demands specialized expertise and incurs substantial operational and maintenance costs, making it economically burdensome in resource-limited settings.
DOI: 10.7274/25545646.v1
title: Development of Analytical Methods and Machine Learning Platforms for Assessing the Quality of Pharmaceuticals and Drugs of Abuse

description: In low and middle-income countries (LMICs), the prevalence of counterfeit medicines, estimated at 1 in 10 pharmaceuticals, underscores the urgent need for quick and affordable presumptive analytical screening tools to mitigate the dangers associated with counterfeit drugs.
This research aims to tackle the challenges in pharmaceutical quality control and post-market surveillance by addressing the limitations of conventional predictive models and exploring the potential of non-brand-specific strategies. Traditional predictive models, often trained on libraries of authentic products, encounter difficulties in identifying quality issues in products beyond their training set. To overcome this, the research employs non-brand-specific strategies, utilizing lab-formulated samples correlated with high-performance liquid chromatography (HPLC) standards as a presumptive analytical method for post-market pharmaceutical screening, assessed through systematic metrics.
The study probes the effectiveness of Paper Analytical Devices (PADs) in discerning the active pharmaceutical ingredient (API) in over 20 antibiotic medicines. Leveraging chemical reactions to produce a unique color pattern, PADs are trained through machine learning predictive models to detect substandard formulations in the field. Despite their high sensitivity, PADs face challenges with specificity when dealing with APIs sharing identical functional groups. In response, the research investigates the integration of PADs with spectroscopic analytical techniques, creating an orthogonal analytical approach aimed at developing a robust technology for reliably detecting substandard and falsified medicines.
External factors, including variations in formulations, excipients, capsule type, color, and instrumental design/device fabrication, significantly influence pharmaceutical analysis. The research highlights the impact of capsule composition on spectroscopic analytical techniques, such as Near-Infrared (NIR) modeling. Factors like capsule type, color, or thickness introduce variance in NIR spectra comparable to the variance resulting from the type of API stored within the capsules. Recognizing and accounting for these external factors are essential for accurate and reliable analysis.
Furthermore, the research addresses a critical financial challenge in low and middle-income countries (LMICs) by introducing a cost-saving technique for achieving a more robust post-market surveillance. HPLC, while a powerful analytical method, demands specialized expertise and incurs substantial operational and maintenance costs, making it economically burdensome in resource-limited settings.
DOI: 10.7274/25568472
title: Two-Dimensional Molybdenum Disulfide for Sunlight Harvesting: Photophysical and Catalytic Insights

description: The increasing demand for energy, together with growing concerns about climate change and environmental degradation, has forced a global shift towards renewable energy sources. Sunlight, as a non-polluting and infinitely renewable source of clean energy, has gained significant attention in this transition. Tremendous efforts have been devoted to exploring suitable materials for harvesting sunlight, aiming to address the energy and environmental challenges we face today. Among the materials investigated, two-dimensional molybdenum disulfide (MoS2) has emerged as a promising candidate for sunlight harvesting applications. Its unique photophysical and catalytic properties make it particularly attractive for solar energy conversion. This thesis focuses on investigating the photophysical behavior and catalytic capabilities of MoS2 nanosheets, offering insights into its potential for advancing solar energy utilization.
The thesis begins by exploring the role of Ag nanoparticle cocatalysts in improving the photocatalytic properties of MoS2 nanosheets, elucidating the mechanisms underlying photoinduced charge separation. Subsequent chapters investigate the storage of electrons in MoS2 nanosheets induced by sunlight excitation and externally applied bias, establishing its potential for energy storage. Additionally, the corresponding changes in optical and electrical properties driven by the weakening of interlayer van der Waals interactions and the introduction of free charge carriers into MoS2 nanosheets are discussed. Spectroelectrochemistry is employed to further probe the mechanism underlying the stabilization of stored electrons via counter cation intercalation. The analysis of how different cation sizes affect MoS2 intercalation offers viewpoints for optimizing the design and application of MoS2 nanosheets for advanced solar energy conversion technologies. Furthermore, the thesis examines the dissociative adsorption of water on sulfur vacancy-rich MoS2 interfaces using in-situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The findings highlight the potential of surface-engineering techniques to improve the catalytic performance of MoS2, rendering it a more efficient material for water dissociation reactions. Overall, this thesis discusses the photophysical properties and surface chemistry of molybdenum disulfide. These findings provide perspectives for the utilization of MoS2 in sunlight harvesting applications and beyond, offering solutions for addressing the energy and environmental challenges of the future.
DOI: 10.7274/25568472.v1
title: Two-Dimensional Molybdenum Disulfide for Sunlight Harvesting: Photophysical and Catalytic Insights

description: The increasing demand for energy, together with growing concerns about climate change and environmental degradation, has forced a global shift towards renewable energy sources. Sunlight, as a non-polluting and infinitely renewable source of clean energy, has gained significant attention in this transition. Tremendous efforts have been devoted to exploring suitable materials for harvesting sunlight, aiming to address the energy and environmental challenges we face today. Among the materials investigated, two-dimensional molybdenum disulfide (MoS2) has emerged as a promising candidate for sunlight harvesting applications. Its unique photophysical and catalytic properties make it particularly attractive for solar energy conversion. This thesis focuses on investigating the photophysical behavior and catalytic capabilities of MoS2 nanosheets, offering insights into its potential for advancing solar energy utilization.
The thesis begins by exploring the role of Ag nanoparticle cocatalysts in improving the photocatalytic properties of MoS2 nanosheets, elucidating the mechanisms underlying photoinduced charge separation. Subsequent chapters investigate the storage of electrons in MoS2 nanosheets induced by sunlight excitation and externally applied bias, establishing its potential for energy storage. Additionally, the corresponding changes in optical and electrical properties driven by the weakening of interlayer van der Waals interactions and the introduction of free charge carriers into MoS2 nanosheets are discussed. Spectroelectrochemistry is employed to further probe the mechanism underlying the stabilization of stored electrons via counter cation intercalation. The analysis of how different cation sizes affect MoS2 intercalation offers viewpoints for optimizing the design and application of MoS2 nanosheets for advanced solar energy conversion technologies. Furthermore, the thesis examines the dissociative adsorption of water on sulfur vacancy-rich MoS2 interfaces using in-situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The findings highlight the potential of surface-engineering techniques to improve the catalytic performance of MoS2, rendering it a more efficient material for water dissociation reactions. Overall, this thesis discusses the photophysical properties and surface chemistry of molybdenum disulfide. These findings provide perspectives for the utilization of MoS2 in sunlight harvesting applications and beyond, offering solutions for addressing the energy and environmental challenges of the future.