Thermoelectric devices and supercapacitors based on nanostructured semiconducting polymers for energy production and storage

Más de dos terceras partes de la energía generada por las fuentes convencionales se pierden como calor. Recuperar esas pérdidas de energía puede ayudar a crear una forma más eficiente de producir energía para el desarrollo sostenible de nuestra sociedad. Mediante el uso de generadores termoeléctricos es posible producir energía a partir de gradientes de temperatura de tal manera que la termoelectricidad puede ser una buena estrategia para la recolección y recuperación de energía. La eficiencia termoeléctrica suele ser dada por la figura adimensional de mérito, ZT. Actualmente, los materiales inorgánicos se usan comúnmente en aplicaciones termoeléctricas, sin embargo presentan varias desventajas tales como: escasez de materias primas y toxicidad. Los materiales orgánicos, tales como los polímeros conductores, se han convertido en una alternativa a esos materiales inorgánicos debido a sus interesantes propiedades como abundancia flexibilidad y baja conductividad térmica. Sin embargo, su eficiencia termoeléctrica es todavía muy baja en comparación con los materiales inorgánicos. Por esta razón, esta tesis se centra en la síntesis y caracterización completa de polímeros conductores y materiales híbridos para aplicaciones termoeléctricas, desarrollando nuevos métodos de aumentar la eficiencia termoeléctrica de materiales orgánicos. Uno de esas métodos ha sido la optimización del dopado en películas delgadas de Poli(3,4-etilendioxitiofeno) (PEDOT) y polipirrol. Dicho proceso se llevó a cabo mediante una reducción química por medio de hidracina y además también se llevó a cabo mediante una reducción electroquímica. Por otra parte se sintetizaron nanoestructuras de PEDOT mediante polimerización en miniemulsión obteniéndose en una transición de tipo de semiconductor (p a n) mediante la utilización de un surfactante catiónico (bromuro de deciltrimetilamonio). Por otra parte también se sintetizaron materiales de índole inorgánica como nanostructuras de tipo nanohilo de compuestos basados en Nd1−xCaxCoO3 y La1−xCaxMnO3, mostrando cierta dependencia en las propiedades termoeléctricas con el contenido en calcio en ambos casos. Además, se estudiaron las propiedades termoeléctricas de materiales basados en carbono como: negro de humo, carbón vegetal y vitrografito. Dichos compuestos fueron sometidos a tratamientos de irradiación y hidrogenación observándose variaciones en el signo del coeficiente de Seebeck como en el caso de las muestras de vitrografito o un gran aumento en la conductividad eléctrica para las muestras de carbón vegetal. Por otro lado, se sintetizaron materiales híbridos y nanocomposites con el fin de obtener un material final con mejores propiedades que las sustancias de partida. De tal manera que se estudiaron películas de PEDOT/grafito expandido, donde se observó un aumento de la eficiencia termoeléctrica con el contenido en grafito expandido. Otros materiales compuestos a destacar fueros los sintetizados a partir de nanotubos multipared (MWCNTs) y PEDOT combinado el método capa a capa y la síntesis electroquímica llegando a obtener 155 µW/m2 K en mejor de los casos. Destaca también la síntesis de películas de Te sobre electros de PEDOT llegando a obtener 320 µW/m2K a 150 minutos de electrodeposición de Te. Por último, esta tesis muestra la fabricación de dispositivos utilizando materiales sintetizados en el laboratorio tales como: un generador termoeléctrico basado en PEDOT sintetizado por vía electroquímica, un generador termoeléctrico cilíndrico basado en PEDOT/MWCNTs, un sensor térmico fabricado con películas de PEDOT y por último supercondensadores basados en telas de algodón combinadas con MWCNTs, PEDOT y MnO2.More than two third parts of the energy generated by conventional sources is lost as heat. Recovering those energy losses can help to create a more efficient way to produce energy for a sustainable development of our society. By using thermoelectric generators it is possible to produce energy from temperature gradients. Showing that, thermoelectricity can be a good strategy for energy harvesting and recovery. The thermoelectric efficiency is usually given by the dimensionless figure of merit, ZT. Currently, inorganic materials are commonly used in thermoelectric applications, however they present several disadvantages such as: scarcity of the raw materials and toxicity. Due to their interesting properties, organic materials, such as conducting polymers, have become an alternative to those inorganic materials. However, their thermoelectric efficiency is still very low compared with inorganic materials. For this reason, this thesis is focused on the synthesis and complete characterization of conducting polymers and hybrid materials for thermoelectric applications, developing new ways to increase the thermoelectric efficiency of organic materials. In addition, this thesis show the fabrication of thermoelectric generators and supercapacitor devices using materials synthesized in our laboratories

3D printable electroconductive gelatin‑hyaluronic acid materials containing polypyrrole nanoparticles for electroactive tissue engineering

Electrically conductive bio-scaffolds are explored in the field of tissue engineering (TE) as a solution to address the clinical need of electroactive tissues, finding applications in nervous, cardiac, and spinal cord injury repair. In this work, we synthesise polypyrrole nanoparticles (PPy NP) via the mini-emulsion method with further combination with a gelatin/hyaluronic acid (HA) hydrogel to create electroconductive Gel:HA:PPy-NP TE scaffolds. Electroconductive Gel:HA:PPy-NP scaffolds possess excellent mechanical properties at 1.08 ± 0.26 MPa, closely matching the reported mechanical performance of the spinal cord. Scaffolds were designed with controlled porosity of 526.2 ± 74.6â 403.9 ± 57.4 μm, and conductivities of 4.3 à 10 â 6 ± 1.1 à 10 â 6 S.cm â 1 were reached. Rheological studies show that prior to lyophilisation, the Gel:HA:PPy-NP hydrogels display a shear-thinning behaviour. These gels were subsequently 3D printed into predefined 2 layer lattice geometries and displayed excellent post-printing shape fidelity. In vitro studies show that the Gel:HA:PPy-NP scaffolds are cytocompatible with mesenchymal stem cells and neuronal stem cells and display encouraging cell attachment and proliferation profiles. Based on these results, the incorporation of PPy NPs into Gel:HA biomaterial scaffolds enhances the conductive capabilities of the material, while showcasing biocompatible behaviour with cell cultures. Hence, Gel:HA:PPy-NP scaffolds are a promising TE option for stimulating regeneration following nervous tissue injury.The authors would like to thank the funding provided by the Irish Research Council through the Irish Research Council Enterprise Partnership Scheme with Johnson and Johnson (EPSPG/2020/78), as well as the Irish Fulbright Commission

Development of a green fluorescent tagged strain of Aspergillus carbonarius to monitor fungal colonization in grapes

An enhanced green fluorescent protein has been used to tag an OTA-producing strain of Aspergillus carbonarius (W04-40) isolated from naturally infected grape berries. Transformation of the fungus was mediated by Agrobacterium tumefaciens. The most efficient transformation occurred when the co-cultivation was done with 104 conidia due to higher frequency of resistance colonies (894 per 104 conidia) and lower background obtained. To confirm the presence of the hph gene in hygromycin resistant colonies, 20 putative transformants were screened by PCR analysis. The hph gene was identified in all the transformants. Variation on the expression levels of the eGFP was detected among the transformants and 50% of them appeared bright green fluorescent under the microscope. Microscopic analysis of all the bright fluorescent transformants revealed homogeneity of the fluorescent signal, which was clearly visible in the hyphae as well as in the conidia. eGFP expression in A. carbonarius was shown to be stable in all transformants. Confocal Laser scanning microscopy images of grape berries infected with the eGFP transformant demonstrated fungal penetration into the berry tissues. OTA production was importantly increased in the eGFP transformant in comparison with the wild type strain and pathogenicity on grape berries was slightly decreased after four days of inoculation. However, no differences in virulence were found after seven days of inoculation, thus allowing utilization of this eGFP mutant for in situ analysis of A. carbonarius infection of grape berries. To our knowledge, this is the first report describing the construction of a GFP-tagged strain belonging to Aspergillus section Nigri for monitoring Aspergillus rot on grape berries.This research was supported by AGL2005-00707/ALI and AGL2008-04828-C03-02 grants from the Spanish Government.Peer Reviewe

Cryotherapy in the paediatric airway: Indications, success and safety

Airway obstruction; Cryobiopsy; Paediatric bronchoscopyObstrucción de las vías respiratorias; Criobiopsia; Broncoscopia pediátricaObstrucció de les vies respiratòries; Criobiòpsia; Broncoscòpia pediàtricaBackground and objective Cryotherapy in interventional bronchoscopy is a new treatment modality, which has recently been made available for the paediatric airway. Lack of experience and safety concerns have led to hesitant adaptation. The aim of this study was to assess indications, success rates and complications of airway cryotherapy in children. Methods Bronchoscopists from medical centre performing cryotherapy in patients between 0 and 18 years were invited to participate in a prospective study based on an online questionnaire. Patient and participant data were collected between June 2020 and June 2021. Results A total of 69 cryotherapy procedures were performed in 57 patients a for three main indications: Biopsy (30), restoration of airway patency (23) and foreign body aspiration (16). The overall success rate was 93%, the remaining 7% were performed for foreign body removal and required a switch of technique. Restoration of airway patency was successfully applied in various pathologies, including mucus plugs, bronchial casts and post traumatic stenosis. The diagnostic yield of transbronchial biopsies was 96%. No severe complications were encountered; one pneumothorax following a cryobiopsy required a chest drain for 48 h. No child was admitted to intensive care or died from a procedural complication. Conclusion In this largest paediatric case collection to date, cryotherapy was safe and carried a high success rate. Cryobiopsy compares favourably to the widely used forceps biopsy and could replace it in the future. Paediatric bronchoscopists are encouraged to add cryotherapy to their armamentarium of airway interventions.Open Access funding enabled and organized by Projekt DEAL

Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers

Abstract Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work.Peer Reviewe

Effects of Gamma Irradiation on the Kinetics of the Adsorption and Desorption of Hydrogen in Carbon Microfibres

In this study, three types of carbon fibres were used, they were ex-polyacrylonitrile carbon fibres with high bulk modulus, ex-polyacrylonitrile fibres with high strength, and vapour grown carbon fibres. All the samples were subjected to a hydrogen adsorption process at room temperature in an over-pressured atmosphere of 25 bars. The adsorption process was monitored through electrical resistivity measurements. As conditioning of the fibres, a chemical activation by acid etching followed by ¿-ray irradiation with 60Co radioisotopes was performed. The surface energy was deter-mined by means of the sessile drop test. Both conditioning treatments are supplementary; the chemical activation works on the outer surface and the ¿-irradiation works in the bulk material as well. Apparently, the most significant parameter for hydrogen storage is the crystallite size. From this point of view, the mostPeer Reviewe

In Situ Synthesis of Polythiophene and Silver Nanoparticles within a PMMA Matrix: A Nanocomposite Approach to Thermoelectrics

The processability of organic thermoelectric materials plays a crucial role due to their clear advantages of applicability in large-scale areas compared to traditional inorganic counterparts. A promising way to process thermoelectric materials based on conductive polymers is through in situ polymerization in an insulating polymer matrix. This work shows an interpenetrating polymeric network based on polythiophene, silver nanoparticles (Ag NPs), and poly(methyl methacrylate) (PMMA) produced by the oxidative polymerization of terthiophene by an oxidizing silver salt in a PMMA matrix. Ag NPs are in situ synthesized simultaneously as a byproduct. The reaction occurs very fast in the solid state, and after only 1 min, a homogeneous interpenetrating polymer network (IPN) film is obtained, reaching electrical conductivity values of 120 S cm–1. Ag NPs play a determining role in the conducting properties of the IPN. Moreover, the thermoelectric properties were evaluated as a function of the synthesis parameters, reaching a maximum power factor of 51 μW m–1 K–2. This study shows a promising method to enhance the processability of hybrid thermoelectric materials on the basis of conductive polymers and nanofillers

Lung Ultrasound as a First-Line Test in the Evaluation of Post-COVID-19 Pulmonary Sequelae

COVID-19; Lung ultrasound (LUS); Pulmonary sequelaeCOVID-19; Ecografía pulmonar (LUS); Secuelas pulmonaresCOVID-19; Ecografia pulmonar (LUS); Seqüeles pulmonarsBackground: Interstitial lung sequelae are increasingly being reported in survivors of COVID-19 pneumonia. An early detection of these lesions may help prevent the development of irreversible lung fibrosis. Lung ultrasound (LUS) has shown high diagnostic accuracy in interstitial lung disease (ILD) and could likely be used as a first-line test for post-COVID-19 lung sequelae. Methods: Single-center observational prospective study. Follow-up assessments of consecutive patients hospitalized for COVID-19 pneumonia were conducted 2–5 months after the hospitalization. All patients underwent pulmonary function tests (PFTs), high-resolution computed tomography (HRCT), and LUS. Radiological alterations in HRCT were quantified using the Warrick score. The LUS score was obtained by evaluating the presence of pathological B-lines in 12 thoracic areas (range, 0–12). The correlation between the LUS and Warrick scores was analyzed. Results: Three hundred and fifty-two patients who recovered from COVID-19 pneumonia were recruited between July and September 2020. At follow-up, dyspnea was the most frequent symptom (69.3%). FVC and DLCO alterations were present in 79 (22.4%) and 234 (66.5%) patients, respectively. HRCT showed relevant interstitial lung sequelae (RILS) in 154 (43.8%) patients (Warrick score ≥ 7). The LUS score was strongly correlated with the HRCT Warrick score (r = 0.77) and showed a moderate inverse correlation with DLCO (r = −0.55). The ROC curve analysis revealed that a LUS score ≥ 3 indicated an excellent ability to discriminate patients with RILS (sensitivity, 94.2%; specificity, 81.8%; negative predictive value, 94.7%). Conclusions: LUS could be implemented as a first-line procedure in the evaluation of Post-COVID-19 interstitial lung sequelae. A normal LUS examination rules out the presence of these sequelae in COVID-19 survivors, avoiding the need for additional diagnostic tests such as HRCT