478 research outputs found

    Advanced Materials and Technologies in Nanogenerators

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    This reprint discusses the various applications, new materials, and evolution in the field of nanogenerators. This lays the foundation for the popularization of their broad applications in energy science, environmental protection, wearable electronics, self-powered sensors, medical science, robotics, and artificial intelligence

    Engineered Porous Carbon Adsorbents for Radionuclide Remediation: A Study of Chemical and Physical Factors

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    Accidental release of radioactive material to the environment poses a widespread threat to health of the biosphere, including to humans though contamination of food or water sources, or though inhalation of airborne radioactive particles. The development of targeted, functionalised adsorbents and remediation materials which have the versatility to work effectively in varying groundwater conditions, often containing high quantities of dissolved matter, is necessary. Biopolymers are such a class of materials which are well suited to remediation and immobilisation of contaminants such as radionuclides from groundwater and soil. Not only do they possess promising physicochemical characteristics such as extensive hierarchical porosity, surface functionality and recalcitrance, they are inherently compatible with environmental systems. They can be further functionalised or activated, or incorporated into monolithic composites with specific, engineered functionality and morphology for enhanced uptake and removal of radionuclides. Despite this promise, they are poorly understood at a mechanistic level, in part, due to their amorphous nature which makes analysis of molecular scale processes difficult. Therefore consistent bulk behaviour is more difficult to predict. Understanding the underpinning physical and chemical features of biopolymers and their composites is a crucial step to both further optimisation and deployment of such a material in a remediation setting. Several functionalised biopolymers and monolithic composites were created for strontium uptake and immobilisation. Both the physical and chemical factors governing uptake behaviour were examined. The binding mechanism of strontium was examined using X-ray absorption spectroscopy and paired with bulk strontium uptake isotherm data. High and rapid uptake capacities were achieved to functionalised biochar with even higher uptake achieved to novel biochar-alginate hydrogel composites. EXAFS fitting results indicated biochars and hydrogels alike exhibit an inner sphere binding mechanism to engineered biopolymer adsorbents, indicating strong binding to the adsorbent. Pores, specifically macro pores play a crucial role in mass transport of radionuclides to/from active adsorption sites. They can also prevent pore blocking or fouling during adsorption. The pore architecture of a range of functionalised biochars was investigated quantitatively using X-ray tomography, revealing the pore tuning effect of several common activators on the macro pore space. Each choice of biochar-activator combination yields distinct pore architecture, which can be selected in response to varying application or conditions

    Laser Patterned N-doped Carbon: Preparation, Functionalization and Selective Chemical Sensors

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    Die kürzliche globale COVID-19-Pandemie hat deutlich gezeigt, dass hohe medizinische Kosten eine große Herausforderung für unser Gesundheitssystem darstellen. Daher besteht eine wachsende Nachfrage nach personalisierten tragbaren Geräten zur kontinuierlichen Überwachung des Gesundheitszustands von Menschen durch nicht-invasive Erfassung physiologischer Signale. Diese Dissertation fasst die Forschung zur Laserkarbonisierung als Werkzeug für die Synthese flexibler Gassensoren zusammen und präsentiert die Arbeit in vier Teilen. Der erste Teil stellt ein integriertes zweistufiges Verfahren zur Herstellung von laserstrukturiertem (Stickstoff-dotiertem) Kohlenstoff (LP-NC) ausgehend von molekularen Vorstufen vor. Der zweite Teil demonstriert die Herstellung eines flexiblen Sensors für die Kohlendioxid Erfassung basierend auf der Laserumwandlung einer Adenin-basierten Primärtinte. Die unidirektionale Energieeinwirkung kombiniert mit der tiefenabhängigen Abschwächung des Laserstrahls ergibt eine neuartige geschichtete Sensorheterostruktur mit porösen Transducer- und aktiven Sensorschichten. Dieser auf molekularen Vorläufern basierende Laserkarbonisierungsprozess ermöglicht eine selektive Modifikation der Eigenschaften von gedruckten Kohlenstoffmaterialien. Im dritten Teil wird gezeigt, dass die Imprägnierung von LP-NC mit Molybdäncarbid Nanopartikeln die Ladungsträgerdichte verändert, was wiederum die Empfindlichkeit von LP-NC gegenüber gasförmigen Analyten erhöht. Der letzte Teil erläutert, dass die Leitfähigkeit und die Oberflächeneigenschaften von LP-NC verändert werden können, indem der Originaltinte unterschiedliche Konzentrationen von Zinknitrat zugesetzt werden, um die selektiven Elemente des Sensormaterials zu verändern. Basierend auf diesen Faktoren zeigte die hergestellte LP-NC-basierte Sensorplattform in dieser Studie eine hohe Empfindlichkeit und Selektivität für verschiedene flüchtige organische Verbindungen.The recent global COVID-19 pandemic clearly displayed that the high costs of medical care on top of an aging population bring great challenges to our health systems. As a result, the demand for personalized wearable devices to continuously monitor the health status of individuals by non-invasive detection of physiological signals, thereby providing sufficient information for health monitoring and even preliminary medical diagnosis, is growing. This dissertation summarizes my research on laser-carbonization as a tool for the synthesis of functional materials for flexible gas sensors. The whole work is divided into four parts. The first part presents an integrated two-step approach starting from molecular precursor to prepare laser-patterned (nitrogen-doped) carbon (LP-NC). The second part shows the fabrication of a flexible LP-NC sensor architecture for room-temperature sensing of carbon dioxide via laser conversion of an adenine-based primary ink. By the unidirectional energy impact in conjunction with depth-dependent attenuation of the laser beam, a novel layered sensor heterostructure with a porous transducer and an active sensor layer is formed. This molecular precursor-based laser carbonization method enables the modification of printed carbon materials. In the third part, it is shown that impregnation of LP-NC with molybdenum carbide nanoparticle alters the charge carrier density, which, in turn, increases the sensitivity of LP-NC towards gaseous analytes. The last part explains that the electrical conductivity and surface properties of LP-NC can be modified by adding different concentrations of zinc nitrate into the primary ink to add selectivity elements to the sensor materials. Based on these factors, the LP-NC-based sensor platforms prepared in this study exhibited high sensitivity and selectivity for different volatile organic compounds

    CERNAS: Current Evolution and Research Novelty in Agricultural Sustainability

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    Climate changes pose overwhelming impacts on primary production and, consequently, on agricultural and animal farming. Additionally, at present, agriculture still depends strongly on fossil fuels both for energy and production factors ,such as synthetized inorganic fertilizers and harmful chemicals such as pesticides. The need to feed the growing world population poses many challenges. The need to reduce environmental impacts to a minimum, maintain healthy ecosystems, and improve soil microbiota are central to ensuring a promising future for coming generations. Livestock production under cover crop systems helps to alleviate compaction so that oxygen and water can sufficiently flow in the soil, add organic matter, and help hold soil in place, reducing crusting and protecting against erosion. The use of organic plant production practices allied to the control of substances used in agriculture also decisively contributes to alleviating the pressure on ecosystems. Some of the goals of this new decade are to use enhanced sustainable production methodologies to improve the input/output ratios of primary production, reduce environmental impacts, and rely on new innovative technologies. This reprint addresses original studies and reviews focused on the current evolution and research novelty in agricultural sustainability. New developments are discussed on issues related to quality of soil, natural fertilizers, or the sustainable use of land and water. Also, crop protection techniques are pivotal for sustainable food production under the challenges of the Sustainable Development Goals of the United Nations, allied to innovative weed control methodologies as a way to reduce the utilization of pesticides. The role of precision and smart agriculture is becoming more pertinent as communication technologies improve at a rapid rate. Waste management, reuse of agro-industrial residues, extension of shelf life, and use of new technologies are ways to reduce food waste, all contributing to higher sustainability in food supply chains, leading to a more rational use of natural resources. The unquestionable role of bees as pollinators and contributors to biodiversity is adjacent to characterizing beekeeping activities, which in turn contributes, together with the valorization of endemic varieties of plant foods, to the development of local communities. Finally, the short circuits and local food markets have a decisive role in the preservation and enhancement of rural economies.info:eu-repo/semantics/publishedVersio

    Development of techniques to determine extracellular matrix alterations in acute and chronic lung diseases and bioengineered tissues

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    Acute and chronic lung diseases are a major cause of global mortality. While pharmacological approaches exist, no therapies are curative. The only option at end-stage disease is lung transplantation which is hampered by a chronic shortage of donor organs. Therefore, there is a high interest to develop alternative approaches to use regenerative medicine approaches to generate new lung tissue in the lab or to deliver cells which can participate in structural repair. In parallel to this clinical need, these new technologies, and the animal models which are used to assess their efficacy, require the development of new evaluation methods. One of the most important methods for evaluating these therapies is histological assessment, as it can provide direct information at the tissue and cellular level information across all stages of the bioengineered tissue: from manufacture through evaluation in pre-clinical animal models. However, many of these potential therapies are comprised of a mix of cells, extracellular matrix and biomaterials (i.e. polymers in the case of soft tissues). Standard histological approaches have been developed for use with native animal and human tissues and organs, based on chemical moieties which are ubiquitous in animal tissues (e.g. amine or carboxylic acid groups). Biomaterials (e.g. synthetic or natural polymers), on the other hand, have diverse chemical moieties that may not always be compatible with standard fixatives and tissue processing. Furthermore, the chemical composition of the solutions used in fixation or tissue processing, even at trace amounts, may alter biomaterials which have been used for bioengineering tissue or in vitro models. Therefore, this thesis aimed to develop new methods to histologically assess native and bioengineered lung tissue, with a particular focus on developing methods which preserve cell-extracellular matrix or cell-biomaterial interactions for light and electron-based microscopy
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