A Rapid, Low-Cost, and Scalable Technique for Printing State-of-the-Art Organic Field-Effect Transistors

In the last few years exciting advances have been achieved in developing printing techniques for organic semiconductors, and impressive mobility values have been reported for the resulting organic field-effect transistors (OFETs). However, not all these techniques are scalable and some of them require additional crystallization steps. This study reports on the fabrication of OFETs employing blends of four benchmark organic semiconductors with polystyrene and demonstrates that applying the same formulation and experimental conditions for printing them, highly reproducible and uniform crystalline films exhibiting high OFET performance are successfully achieved. It is noted that the mobility values achieved here are not the highest reported for the studied materials; however, they are state-of-the-art values and could be regarded as exceptional considering the low cost and fast speed of the fabrication process involved here.This work was mainly funded by the ERC StG 2012 306826 e GAMES and ERC PoC 2014 640120 LAB TECH projects. The authors also thank the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER BBN), the DGI (Spain) project BE WELL CTQ2013 40480 R, the Generalitat de Catalunya (2014 SGR 17) and the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV 2015 0496). The authors would like to thank the ICTS "NANBIOSIS", more specifically to the Nanotechnology Platform, unit of CIBER BBN at the Institute for Bioengineering of Catalonia (IBEC) for their assistance in ToF SIMS analyses. I. T. acknowledges FPU fellowship from the Ministery and the Materials Science PhD Program of Universitat Autònoma de Barcelona. F. G. D. P. thanks Universidad Técnica de Ambato and Secretaría de Educación Superior, Ciencia, Tecnología e Innovación for funding through a doctoral scholarship “Convocatoria abierta 2010”.Peer reviewe

A rapid, low-cost, and scalable technique for printing state-of-the-art organic field-effcet transistors

In the last few years exciting advances have been achieved in developing printing techniques for organic semiconductors, and impressive mobility values have been reported for the resulting organic field-effect transistors (OFETs). However, not all these techniques are scalable and some of them require additional crystallization steps. This study reports on the fabrication of OFETs employing blends of four benchmark organic semiconductors with polystyrene and demonstrates that applying the same formulation and experimental conditions for printing them, highly reproducible and uniform crystalline films exhibiting high OFET performance are successfully achieved. It is noted that the mobility values achieved here are not the highest reported for the studied materials; however, they are state-of-the-art values and could be regarded as exceptional considering the low cost and fast speed of the fabrication process involved here.Peer ReviewedPostprint (published version

Effect of intravenous pulses of methylprednisolone 250 mg versus dexamethasone 6 mg in hospitalised adults with severe COVID ‐19 pneumonia: An open‐label randomised trial

Producción CientíficaBackground: The efficacy and safety of high versus medium doses of glucocorticoids for the treatment of patients with COVID-19 has shown mixed outcomes in controlled trials and observational studies. We aimed to evaluate the effectiveness of methylprednisolone 250 mg bolus versus dexamethasone 6 mg in patients with severe COVID-19. Methods: A randomised, open-label, controlled trial was conducted between February and August 2021 at four hospitals in Spain. The trial was suspended after the first interim analysis since the investigators considered that continuing the trial would be futile. Patients were randomly assigned in a 1:1 ratio to receive dexamethasone 6 mg once daily for up to 10 days or methylprednisolone 250 mg once daily for 3 days. Results: Of the 128 randomised patients, 125 were analysed (mean age 60 ± 17 years; 82 males [66%]). Mortality at 28 days was 4.8% in the 250 mg methylprednisolone group versus 4.8% in the 6 mg dexamethasone group (absolute risk difference, 0.1% [95% CI, −8.8 to 9.1%]; p = 0.98). None of the secondary outcomes (admission to the intensive care unit, non-invasive respiratory or high-flow oxygen support, additional immunosuppressive drugs, or length of stay), or prespecified sensitivity analyses were statistically significant. Hyperglycaemia was more frequent in the methylprednisolone group at 27.0 versus 8.1% (absolute risk difference, −18.9% [95% CI, −31.8 to - 5.6%]; p = 0.007). Conclusions: Among severe but not critical patients with COVID-19, 250 mg/d for 3 days of methylprednisolone compared with 6 mg/d for 10 days of dexamethasone did not result in a decrease in mortality or intubation

Inventory of Geological Sites of Interest in the Canary Islands

En el marco de proyecto de investigación LIGCANARIAS (2018-2021) se ha realizado el Inventario de Lugares de Interés Geológico de las Islas Canarias, que forma parte del Inventario Español de Lugares de Interés Geológico (IELIG) para el dominio de este archipiélago. El inventario ha empleado la metodología del IELIG adaptada a un dominio geológico eminentemente volcánico, partiendo de los contextos geológicos regionales. Consta de 300 LIG: 53 en Gran Canaria, 47 en Tenerife, 54 en Lanzarote y Archipiélago Chinijo, 40 en Fuerteventura, 29 en La Palma, 23 en La Gomera y 21 en El Hierro. La principal novedad con respecto a los inventarios en otros dominios geológicos es la identificación de 33 LIG submarinos.Within the framework of the LIGCANARIAS research project (2018-2021), the Inventory of Geological Sites of Interest of the Canary Islands has been carried out, which is part of the Spanish Inventory of Places of Geological Interest (IELIG) for the domain of this archipelago. The inventory has used the IELIG methodology adapted to an eminently volcanic geological domain, based on regional geological frameworks. It consists of 300 geosites: 53 in Gran Canaria, 47 in Tenerife, 54 in Lanzarote and Chinijo Archipelago, 40 in Fuerteventura, 29 in La Palma, 23 in La Gomera and 21 in El Hierro. The main novelty with respect to the inventories in other geological domains is the identification of 33 submarine geosites.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEAgencia Canaria de Investigación, Innovación y Sociedad de la Informaciónpu

Solution-processed organic field-effect transistors: from fundamental aspects to applications

En esta tesis hemos estudiado varios factores relacionados con los transistores orgánicos de efecto campo (OFETs) procesados por solución, incluyendo su fabricación, su caracterización eléctrica y posibles aplicaciones, especialmente en el campo de sensores físicos. En este trabajo se han utilizado principalmente disoluciones de diferentes semiconductores orgánicos (OSC) de pequeña molécula tipo-p y polímeros aislantes. La deposición de estas mezclas para obtener las capas activas de los OFETs se ha llevado a cabo mediante una técnica de procesado por solución escalable, en concreto la denominada bar-assisted meniscus shearing (BAMS). El propósito principal de este trabajo ha sido comprender la influencia que tienen los parámetros de fabricación elegidos sobre las propiedades morfológicas y estructurales de las capas activas resultantes, y, por tanto, su impacto en las propiedades eléctricas de los dispositivos finales. Se ha realizado un estudio detallado a escala nanométrica de capas basadas en OSC:polímero aislante, descifrando la separación vertical de ambos componentes y el efecto que tiene sobre la estabilidad y el rendimiento de los dispositivos. Además, se han explorado diferentes métodos de dopaje con el objetivo de mejorar las características eléctricas de los OFETs que sufren de una alta resistencia de contacto. También se ha estudiado la relación entre propiedades morfológicas y eléctricas empleando dispositivos flexibles sometidos a tensión mecánica. Finalmente, gracias a la optimización de los parámetros de procesado se han fabricado OFETs con una alta sensibilidad a radiación de rayos-X, explicando a su vez cómo la morfología y el transporte de carga en la capa activa determinan la respuesta de estos dispositivos.In this thesis we have studied several aspects related to organic field-effect transistors (OFETs) printed from solution, including their fabrication, their electrical characterisation, and further applications, especially in the field of physical sensing. Blends of different p‑type small molecule organic semiconductors (OSCs) and insulating polymer binders have been employed in this research work. For the deposition of such blends as active layers for OFETs a scalable solution processing technique has been exploited, namely bar‑assisted meniscus shearing (BAMS). The main purpose of the work carried out has been understanding the influence of the fabrication parameters of choice on the morphological and structural features of the resulting active layer and, thus, their impact on the electrical performance of the final devices. A detailed nanoscale study of OSC:insulating polymer thin films has been conducted, elucidating the vertical stratification of both components and its effect on the devices stability and performance. Further, aiming at improving the electrical characteristics of devices exhibiting high contact resistance values, different doping methodologies have been explored. In addition, the morphology-performance relationship has been studied for flexible OFET devices subjected to mechanical strain. Finally, OFETs exhibiting high sensitivity to X-ray radiation have been fabricated by optimising the processing parameters, rationalising how the morphological and transport properties of the active layer determine the sensing capability of such devices

Solution-processed organic field-effect transistors: from fundamental aspects to applications

En esta tesis hemos estudiado varios factores relacionados con los transistores orgánicos de efecto campo (OFETs) procesados por solución, incluyendo su fabricación, su caracterización eléctrica y posibles aplicaciones, especialmente en el campo de sensores físicos. En este trabajo se han utilizado principalmente disoluciones de diferentes semiconductores orgánicos (OSC) de pequeña molécula tipo-p y polímeros aislantes. La deposición de estas mezclas para obtener las capas activas de los OFETs se ha llevado a cabo mediante una técnica de procesado por solución escalable, en concreto la denominada bar-assisted meniscus shearing (BAMS). El propósito principal de este trabajo ha sido comprender la influencia que tienen los parámetros de fabricación elegidos sobre las propiedades morfológicas y estructurales de las capas activas resultantes, y, por tanto, su impacto en las propiedades eléctricas de los dispositivos finales. Se ha realizado un estudio detallado a escala nanométrica de capas basadas en OSC:polímero aislante, descifrando la separación vertical de ambos componentes y el efecto que tiene sobre la estabilidad y el rendimiento de los dispositivos. Además, se han explorado diferentes métodos de dopaje con el objetivo de mejorar las características eléctricas de los OFETs que sufren de una alta resistencia de contacto. También se ha estudiado la relación entre propiedades morfológicas y eléctricas empleando dispositivos flexibles sometidos a tensión mecánica. Finalmente, gracias a la optimización de los parámetros de procesado se han fabricado OFETs con una alta sensibilidad a radiación de rayos-X, explicando a su vez cómo la morfología y el transporte de carga en la capa activa determinan la respuesta de estos dispositivos.In this thesis we have studied several aspects related to organic field-effect transistors (OFETs) printed from solution, including their fabrication, their electrical characterisation, and further applications, especially in the field of physical sensing. Blends of different p‑type small molecule organic semiconductors (OSCs) and insulating polymer binders have been employed in this research work. For the deposition of such blends as active layers for OFETs a scalable solution processing technique has been exploited, namely bar‑assisted meniscus shearing (BAMS). The main purpose of the work carried out has been understanding the influence of the fabrication parameters of choice on the morphological and structural features of the resulting active layer and, thus, their impact on the electrical performance of the final devices. A detailed nanoscale study of OSC:insulating polymer thin films has been conducted, elucidating the vertical stratification of both components and its effect on the devices stability and performance. Further, aiming at improving the electrical characteristics of devices exhibiting high contact resistance values, different doping methodologies have been explored. In addition, the morphology-performance relationship has been studied for flexible OFET devices subjected to mechanical strain. Finally, OFETs exhibiting high sensitivity to X-ray radiation have been fabricated by optimising the processing parameters, rationalising how the morphological and transport properties of the active layer determine the sensing capability of such devices

Spectroscopy study of Er3+ -doped Gd2O2S

RESUMEN: El objetivo principal de este trabajo es realizar una caracterización espectroscópica del compuesto Gd2O2S: Er3+(10%) en polvo microcristalino. Se ha llevado a cabo un estudio profundo de sus propiedades ópticas, centrándonos en los fenómenos de upconversion (UC). En general, los oxisulfuros activados con iones trivalentes de tierras raras son fósforos luminiscentes con una alta eficiencia. En particular, se ha demostrado que un 10% Er3+ es la concentración optima para conseguir la emisión UC más eficiente en oxisulfuro de gadolinio bajo excitación en 1510 nm. Se han obtenido espectros de emisión UC a diferentes temperaturas entre 10 K y 300 K excitando a 980 nm. También se ha observado luminiscencia de up-conversion múltiple: emisión azul, verde y roja excitando en cinco niveles diferentes del Er3+, lo cual nunca antes se había observado en un material de UC. También se ha podido medir la evolución temporal de la emisión UC trabajando con diferentes energías de excitación. Esto nos ha permitido identificar en cada caso si el mecanismo de UC dominante era una multi-absorción simultánea de fotones o bien procesos de transferencia de energía. Además, se han utilizado espectros Raman y de reflectancia para estudiar tanto la red como las impurezas de Er3+. Como resultado, determinamos la longitud de onda adecuada para excitar la emisión del Er3+ y también la energía máxima de los fonones de la red. Se ha determinado el desdoblamiento por campo cristalino de dos estados excitados del Er3+, 4S3/2 y 4F9/2, y del nivel fundamental, 4I15/2, por medio del estudio de los espectros de emisión y excitación a baja temperatura y su evolución a medida que ésta aumenta.ABSTRACT: The main goal of this work is the spectroscopic characterization of a microcrystalline powdered sample of Gd2O2S: Er3+(10%). A complete study of its optical properties has been done, focusing on NIR to VIS up-conversion (UC) phenomena. In general, oxysulfides activated with trivalent rare earth ions have shown to be phosphors with high luminescence efficiency. In particular, 10% Er3+ is the optimum concentration to achieve the highest UC efficiency with Er3+-doped gadolinium oxysulfide upon 1510 nm excitation. Up-conversion emission spectra were obtained under 980 nm excitation at different temperatures from 10 K to 300 K. Also, multi-upconversion luminescence was observed: blue, green and red emission under excitation into five different Er3+ excited states, which had never been observed before in any UC material. The temporal evolution of UC luminescent emission under different excitation energies was also measured, which enabled us to identify the dominant UC mechanism, simultaneous multi-photon absorption or energy transfer processes. In addition, Raman and reflectance spectroscopy has been used in order to study both the host material and the dopant ion. As a result, we determined the appropriate wavelength at which Er3+ emission can be excited and also the maximum phonon energy of the lattice. The determination of the magnitude of the crystal-field splitting of two Er3+ excited states, 4S3/2 and 4F9/2, and the ground state, 4I15/2, was achieved through the study of the temperature dependence of excitation and emission spectra.Grado en Físic

Optical prperties of hybrid ordered materials: dye/clay films

RESUMEN: En el presente trabajo se estudia la intercalación del colorante Pironina-Y en películas de arcilla tipo esmectita, concretamente en Saponita, con el fin de desarrollar materiales híbridos ordenados susceptibles de presentar propiedades de interés para aplicaciones ópticas. La elaboración de las películas de Saponita mediante la técnica spin-coating proporciona una distribución bidimensional ordenada de las láminas de arcilla. El colorante se incorpora en el espacio interlaminar de las películas de arcilla mediante un proceso de intercambio catiónico. El espesor de las películas de arcilla se analiza mediante perfilometría, mientras que la carga de colorante intercalada y el aumento del espacio interlaminar se estudia por análisis elemental y difracción de rayos-X, respectivamente. Las propiedades fotofísicas del sistema PY/Sap se determinan mediante las espectroscopías de absorción y fluorescencia, cuya evolución con la concentración de colorante permite estudiar la agregación del mismo. El colorante se incorpora con una orientación preferencial respecto a la normal a la película, dando lugar a un material híbrido macroscópicamente ordenado con respuesta anisótropa a la luz linealmente polarizada. Finalmente, se compara el comportamiento fotofísico de la PY adsorbida en Saponita y en Laponita, en particular el grado y tipo de agregación y cómo afecta a la eficiencia fluorescente del material, resultando más atractivas las películas confeccionadas con Saponita.ABSTRACT: In this work, the intercalation of Pyronin-Y dye into thin solid films of Saponite clays is studied with the goal of developing ordered hybrid materials with interesting properties for optical applications. The elaboration of Saponite films by spin-coating procedure gives rise to a bidimensional organized distribution of the clay layers. The dye is incorporated in the interlayer space of the clay by a cation exchange process. The thickness of the clay films is analyzed by a perfilometer, while the dye loading and the change in the size of the interlayer space is studied by elemental analysis and X-ray diffraction technique, respectively. The photophysical properties of the PY/Sap system are analyzed by absorption and fluorescence spectroscopies at different dye loadings, which also allows studying the dye aggregation. The dye is distributed with a preferential orientation respect to the normal axis of clay films, providing a macroscopic ordered system which shows an anisotropic response to linearly polarized light. Finally, the photophysical behavior of PY adsorbed in Saponite and in Laponite is compared, focusing on the extent and type of molecular aggregation and how it affects the fluorescence efficiency, being Saponite films the most attractive ones.Máster en Nuevos Materiale

High performing solution-coated electrolyte-gated organic fieldeffect transistors for aqueous media operation

Since the first demonstration, the electrolyte-gated organic field-effect transistors (EGOFETs) have immediately gained much attention for the development of cutting-edge technology and they are expected to have a strong impact in the field of (bio-)sensors. However EGOFETs directly expose their active material towards the aqueous media, hence a limited library of organic semiconductors is actually suitable. By using two mostly unexplored strategies in EGOFETs such as blended materials together with a printing technique, we have successfully widened this library. Our benchmarks were 6,13-bis(triisopropylsilylethynyl)pentacene and 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT), which have been firstly blended with polystyrene and secondly deposited by means of the bar-assisted meniscus shearing (BAMS) technique. Our approach yielded thin films (i.e. no thicker than 30 nm) suitable for organic electronics and stable in liquid environment. Up to date, these EGOFETs show unprecedented performances. Furthermore, an extremely harsh environment, like NaCl 1M, has been used in order to test the limit of operability of these electronic devices. Albeit an electrical worsening is observed, our devices can operate under different electrical stresses within the time frame of hours up to a week. In conclusion, our approach turns out to be a powerful tool for the EGOFET manufacturing.The authors thank the ERC StG 2012–306826 e-GAMES project, the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), the DGI (Spain) project BE-WELL CTQ2013-40480-R, the Generalitat de Catalunya (2014-SGR-17) and the Spanish Ministry of Economy and Competitiveness, through the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D (SEV- 2015-0496). Q. Z. acknowledges the China Scholarship Council, the National Natural Science Foundation (NSF) of China (Grant No. 11404266) and the Fundamental Research Funds for the Central Universities of China (Grant No. XDJK2014C081). Q. Z. And I. T. are enrolled in the Materials Science PhD Program of Universitat Autònoma de Barcelona. F.L. gratefully acknowledges the “Juan de la Cierva” programme. The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the Seventh Framework Programme of the European Union (FP7/2007–2013) under REA grant agreement no.600388 (TECNIOSpring programme), and from the Agency for Business Competitiveness of the Government of Catalonia, ACCIÓ. The authors thank Dr. D. Gutierrez and Dr. S. Galindo for their assistance with the switching speed measurements.Peer reviewe