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Controlling Triplet Excitons in Organic Semiconductors with Lanthanide-Doped Nanoparticles
No full textOrganic semiconductors (OSCs) underpin a wide range of optoelectronic technologies, including light-emitting diodes (LEDs), photovoltaics, and sensing devices, owing to their chemical tunability and mechanical flexibility. The optoelectronic performance of these materials is governed by excitonic processes, in which electronically excited states mediate light absorption, emission, and charge generation. Triplet excitons play a central role in determining the excited-state dynamics of OSCs under both optical and electrical excitation. However, in most closed-shell OSCs, triplet excitons are dark states that can neither be directly photogenerated nor harvested luminescently, which fundamentally limits their practical utilisation.
Overcoming these limitations requires strategies that enable the control of molecular triplet excitons. Traditional approaches to control triplets, such as heavy-metal-induced spin-orbit coupling (SOC) or engineering the singlet–triplet energy splitting, impose significant design constraints on OSCs. This thesis explores a new approach to molecular triplet exciton control by combining OSCs with lanthanide-doped nanoparticles (LnNPs). Using optical probes, we reveal the triplet exciton dynamics in a variety of organic–inorganic LnNP@OSC nanohybrid systems.
We present the first direct distance-dependent energy transfer measurements in LnNP@OSC nanohybrids. Using transient absorption spectroscopy (TAS), we show triplet energy transfer (TET) to be governed by a concerted Dexter-type process. Contrary to previous beliefs, we find near-unity TET efficiencies that are independent of distance over the range of OSC–LnNP separations investigated. We show that close coupling between the OSC and LnNPs is primarily important to ensure efficient triplet exciton generation. Although singlet energy transfer (SET) is faster, we show SET efficiencies to be lower and more strongly distance-dependent than TET efficiencies, thereby establishing the advantage of using the triplet manifold for most efficient energy transfer in these systems.
We carry out detailed optical studies of the triplet exciton dynamics in weakly-coupled solution-based LnNP@OSC nanohybrids and demonstrate the strong impact of molecular orientation of OSCs on the triplet exciton dynamics. Furthermore, we study the triplet exciton dynamics across the entire lanthanide series and show that triplet exciton generation is governed by hybridised electronic states that form at the OSC–LnNP interface rather than direct SOC or spin-exchange coupling. We show the resonance nature of both SET and TET in these systems and find near-unity TET efficiencies across the full lanthanide series. We use the established structure-function relationships to produce the first LnNP@OSC-based LEDs, operating in the biologically and technology relevant near-infrared (NIR) spectral region, where molecular triplet excitons mediate the function of these electrically driven devices.
Finally, we investigate strongly-coupled LnNP–OSC systems. We demonstrate an alternative method to enhance spin conversion in OSCs: through spin-exchange interactions with unpaired lanthanide 4f electrons. We show that the radiative Tn ← S0 transition can be activated in these systems, enabling direct photogeneration of triplet excited states from the singlet ground state and allowing for a straightforward way to directly measure triplet energies of OSCs. We present the first TAS measurements directly exciting this transition and for the first time report Urbach energies associated with triplet excitons in OSCs.
The findings in this thesis deepen our understanding of electronic and spin interactions in LnNP@OSC nanohybrids and provide a new paradigm for triplet exciton control in OSCs, enabling their informed design and engineering in optoelectronic devices
Multispectral imaging and automated analysis for quantifying grain quality to reveal known and potential novel alleles affecting grain traits in wheat.
Get PDFTo accelerate the pace of wheat (Triticum aestivum L.) improvement worldwide, desired seed-level characteristics and seed quality receive a growing attention as they directly impact early seedling establishment, seed longevity, and grain quality. Nevertheless, the throughput and accuracy of seed-level phenotyping and analysis have become a key limiting factor in this research domain, requiring new solutions to relieve this bottleneck. In this study, we first combined automated multispectral seed imaging (MSI; i.e. the VideometerLab 4 and Autofeeder systems) with a variety of machine learning and computer vision techniques to establish a high-throughput pipeline to analyse wheat seeds. Then, using 493 lines selected from the NIAB Diverse MAGIC (NDM) population, we applied the pipeline to segment individual seeds from MSI seed-lot images. This enabled us to perform seed-level measurement of sixteen morphological (e.g. seed size, length, width, and roundness) and spectral traits, ranging from ultraviolet (i.e. 375 nm, correlating with crude protein) to near-infrared (e.g. 975 nm, for assessing water content) wavelengths. After verifying these seed quality related traits (R2 ≥ 0.949; p < 0.001), we applied genome-wide association studies (GWAS) to link the computationally derived traits to genetic loci and identified eleven significant loci. Some of the loci were previously reported, with two unknown loci valuable for further assessment. Taken together, we believe this integrated MSI analysis pipeline provides a powerful solution for seed research and crop improvement in wheat, enabling us to bridge MSI, seed-level analysis, and genetic mapping to assess seed morphology, seed quality, and their underlying genetic architectures effectively
Dysregulated miR-124-3p in endometrial epithelial cells reduces endometrial receptivity by altering polarity and adhesion.
Get PDFThe endometrium undergoes substantial remodeling in each menstrual cycle to become receptive to an implanting embryo. Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. MicroRNA-124-3p is elevated in both the serum and endometrial tissue of women with chronic endometritis, a condition associated with infertility. MicroRNA-124-3p also has a role in cell adhesion, a key function during receptivity to allow blastocysts to adhere and implant. In this study, we aimed to determine the function of microRNA-124-3p on endometrial epithelial adhesive capacity during receptivity and effect on embryo implantation. Using a unique inducible, uterine epithelial-specific microRNA overexpression mouse model, we demonstrated that elevated uterine epithelial microRNA-124-3p impaired endometrial receptivity by altering genes associated with cell adhesion and polarity. This resulted in embryo implantation failure. Similarly in a second mouse model, increasing microRNA-124-3p expression only in mouse uterine surface (luminal) epithelium impaired receptivity and led to implantation failure. In humans, we demonstrated that microRNA-124-3p was abnormally increased in the endometrial epithelium of women with unexplained infertility during the receptive window. MicroRNA-124-3p overexpression in primary human endometrial epithelial cells (HEECs) impaired primary human embryo trophectoderm attachment in a 3-dimensional culture model of endometrium. Reduction of microRNA-124-3p in HEECs from infertile women normalized HEEC adhesive capacity. Overexpression of microRNA-124-3p or knockdown of its direct target IQGAP1 reduced fertile HEEC adhesion and its ability to lose polarity. Collectively, our data highlight that microRNA-124-3p and its protein targets contribute to endometrial receptivity by altering cell polarity and adhesion
IUTF Dataset: Enabling Cross-Border Resource for Analysing the Impact of Rainfall on Urban Transportation.
Get PDFUnderstanding the impact of extreme weather, particularly flooding, on urban transportation systems is critical for enhancing city resilience and traffic management. However, research and policy development are often hampered by a lack of datasets that comprehensively integrate detailed traffic dynamics, high-resolution weather information, and road network topology across multiple diverse urban environments. To address this significant gap, we present the Integrated Urban Traffic-Flood (IUTF) dataset. This open-access resource covers 40 major cities across Europe, North America, and Asia, including 21,739 sensors. The IUTF dataset uniquely combines (i) high-resolution traffic parameters derived from over 21,700 sensors (with raw data typically at 5-minute intervals, harmonised to hourly); (ii) detailed hourly precipitation data from ERA5 reanalysis, spatially aligned with (iii) the underlying road network topology for over 1 million road segments, processed from OpenStreetMap. This meticulously curated and validated dataset, created through a novel spatio-temporal harmonisation framework, enables unprecedented, cross-border analysis of weather impacts on urban mobility. It provides a foundational data resource to support applications in traffic flow prediction, infrastructure planning, and the future development of quantitative resilience models
Enable and orchestrate—How keystone actors shape institutions for smart service innovation in ecosystems
Get PDFThis study explores the role of keystone actors in shaping institutions to drive collaborative innovation within service ecosystems, focusing on smart services in industrial B2B settings. Smart services leverage data analytics for enhanced customer insights, marking a strategic shift for product-oriented companies. Transitioning to smart services involves adapting business models and fostering effective collaborations. Keystone actors facilitate this by promoting collaboration and aligning participants toward shared goals without exerting direct control. While previous research emphasizes understanding keystone actors in service ecosystems, how they shape institutions for collaboration is rarely investigated. This study aims to provide insights into driving smart service innovation, enhancing companies’ competitive advantage in the digital era. Using a multiple case study design, the research identifies two keystone actor types: the Orchestrator and the Enabler. The findings offer valuable insights into institution shaping and keystone actors’ influence, guiding practitioners in managing smart service innovation
Rethinking racism again? Assessing conceptual deadlocks and innovations in race theory
Get PDFThrough focusing on racial formation theory, systemic racism theory, and the racialized social systems approach, I argue that sociological race theories often reproduce methodological nationalism, stage-ism, and groupism. Such conceptual approaches often equate the boundaries of racial structures with the geographical borders of nation-states, racial categories are often presented as groups with cohesive racial interests, and there is a methodological proclivity to think in terms of distinct “periods” of racialization in a way that occludes moments of continuity. By contrast, I propose that race theorists ought to focus on transboundary entanglements, slow burning raciality, and dynamic racialization. Taking these concepts together, I specify that race theorists ought to develop understandings of how even hyper-localized conditions of race and racialization may be facilitated by transnational relations; that we ought to consider the continuity of racial domination over the long durée; and that we ought to think about racialization as a dynamic process, bringing more specificity to the notion of racial interests to think of specific moments in which different social fractions (e.g. white elites and white workers) synergize their differing interests to maintain racial domination
Surveying the Language Switching Behaviours of Multilingual Autistic and Non-Autistic Adults.
Get PDFPURPOSE: Whilst research in multilingualism and autism is increasing, there is still a gap when it comes to understanding how multilingual autistic individuals use their multiple languages. The aim of this research was to survey these linguistic behaviours from a self-report perspective and compare them to non-autistic multilingual individuals. METHODS: We collected data from 364 participants of which 177 (autistic = 98; mean age = 44.5, non-autistic = 79; mean age = 42.2) were included in the final analysis. Multilingual usage and switching behaviour were measured through an online questionnaire made available on Qualtrics, developed for the purpose of this research. RESULTS: The questionnaire revealed that autistic participants rated themselves as more multilingual, based on number of languages known, and used their respective languages more than non-autistic participants, although they reported switching between their languages as more effortful than non-autistic participants. A large portion of autistic individuals also reported using a non-native language daily and a similar number of autistic and non-autistic participants reported having lived in a country where their first or second language was spoken. Overall, autistic participants reported comparable or more multilingual language usage than non-autistic participants. CONCLUSIONS: The results of this research demonstrate that speaking autistic adults are, as one might intuitively expect, living active multilingual lives comparable to their typical peers. Future research should further investigate the rapport autistic multilingual individuals have with their linguistic communities via their language usage and the cognitive flexibility that may be associated with living multilingual and cross-national lives
Complex morphology and precession indicators of active galactic nuclei jets in LoTSS DR2
Get PDFThe LOw Frequency ARray Two-metre Sky Survey second data release (LoTSS DR2) covers 27% of the northern sky and contains around four million radio sources. The development of this catalogue involved a large citizen science project (Radio Galaxy Zoo: LOFAR), and more than 116 000 resolved sources went through visual inspection. We took a subset of sources with a flux density above 75 mJy and an angular size of 90″ or greater, yielding a total of 9985 sources, or ∼10% of the visually inspected sources. We classified these by visual inspection in terms of broad source type (e.g. Fanaroff-Riley class I or II, narrow or wide-angle tail, relaxed double), noticeable features (wings, visible jets, banding, filaments), environmental features (cluster environment, merger, diffuse emission). Our specific aim was to search for features linked to jet precession, such as a misaligned jet axis, curvature, and multiple hotspots. This combination of features and morphology allowed us to detect increasingly fine-grained sub-populations of interesting or unusual sources. We find that 28% of sources show evidence of one or more precession indicators, which could make them candidates for hosting close binary supermassive black holes. Potential precession signatures occur in sources of all sizes and luminosities in our sample but appear to favour more massive host galaxies. Our work greatly expands the sample size and parameter space of searches for precession signatures in powerful jetted sources. This work also showcases the diversity of large bright radio sources in the LOFAR surveys, whether or not precession indicators are present
The Circulation of Yersinia pestis in Central Eurasia before and during the First Plague Pandemic (Second to Eighth Century CE): Palaeogenetic and Historical Evidence and Sociopolitical, Ecological, and Climatic Factors
Get PDFModern Yersinia pestis genomes show the greatest diversity of the plague pathogen in Central Eurasia. This region is now widely linked to the origins of the Y. pestis lineages responsible for two historic plague pandemics: one starting with the so-called “Justinianic Plague” of the mid-sixth century and the other with the “Black Death” of the mid-fourteenth century. These pandemics have mostly been studied in the Mediterranean region and Europe. Although the beginning of the latter is clearly defined both geographically and temporally, the early spread of the former has received less attention, despite being the focus of several competing hypotheses. Here, we build on recent discoveries of Y. pestis in late antique human remains from Central Eurasia and Europe. These findings identified an early victim of the Y. pestis lineage in Central Eurasia, centuries before it appeared in Europe during the Justinianic Plague. We contextualize these analyses with (I) what we can reconstruct from archaeological, written, and paleoclimate evidence about the demographic, economic, environmental, and mobility (human and animal) histories of the region in the earliest centuries CE, and (II) written evidence for epidemic disease from the region and neighboring areas, which may be linked to the spread of the plague before, during, and after the Justinianic Plague. Specifically, we examine sources to establish and evaluate hypotheses about how, why, and if the plague spread from Central Eurasia, ultimately causing the Justinianic Plague and the “First Plague Pandemic,” and how significantly Eurasian populations were impacted over these centuries. Despite extensive source analysis, limited information, especially palaeogenomic data, prevents us from definitively pinpointing the immediate origin of the First Plague Pandemic. Still, most evidence strongly suggests that the Y. pestis lineage originated from Central Eurasia