Conjugated Polymers for Organic Electronics: Structural and Electronic Characteristics

The use of organic materials to design electronic devices has actually presented a broad interest for because they constitute an ecological and suitable resource for our current "electronic world". These materials provide several advantages (low cost, light weight, good flexibility and solubility to be easily printed) that cannot be afforded with silicium. They can also potentially interact with biological systems, something impossible with inorganic devices. Between these materials we can include small molecules, polymers, fullerenes, nanotubes, graphene, other carbon-based molecular structures and hybrid materials. Actually these materials are being used to build electronic structures into electronic devices, like organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs), constituting and already commercial reality. Some of them are used on a widespread basis1, and are the focus of some recent researches in molecules2,3 and polymers4-6 suitable for these purposes. In this study we analyze the electronic and molecular characteristics of some different π-conjugated structures in order to evaluate their potential as semiconducting materials for organic electronics. For this purpose we focus on the study of conjugated polymers with different backbones configurations: (i) donor-acceptor configuration, (ii) 1D lineal or 2D branched conjugated backbones, and (iii) encapsulated polymers. To achieve this goal, we use a combined experimental and theoretical approach that includes electronic spectroscopies (i.e., absorption, emission and microsecond transient absorption), vibrational Raman spectroscopy and DFT calculations. These structural modifications are found to provoke a strong impact on the HOMO and LUMO levels and the molecular morphology, and, consequently, on their suitability as semiconductors in organic electronic applications.References 1. S. R. Forrest, M. E. Thompson. Chem. Rev., 2007, 107, 923 2. R. C. González-Cano, G. Saini, J. Jacob, J. T. López Navarrete, J. Casado and M. C. Ruiz Delgado. Chem. Eur. J. 2013, 19, 17165 3. J. L. Zafra, R. C. González-Cano, M. C. Ruiz Delgado, Z. Sun, Y. Li, J. T. López Navarrete, J. Wu and J. Casado. J. Chem. Phys. , 2014, 140, 054706 4. M. Goll, A. Ruff, E. Muks, F. Goerigk, B. Omiecienski, I. Ruff, R. C. González-Cano, J. T. López Navarrete, M. C. Ruiz Delgado, S. Ludwigs. Beilstein J. Org. Chem., 2015, 11, 335. 5. D. Herrero-Carvajal, A. de la Peña, R. C. González-Cano, C. Seoane, J. T. López Navarrete, J. L. Segura, J. Casado, M. C. Ruiz Delgado, J. Phys. Chem. C, 2014, 118, 9899. 6. M. Scheuble, Y. M. Gross, D. Trefz, M. Brinkmann, J. T. López Navarrete, M. C. Ruiz Delgado, and S. Ludwigs, Macromolecules, 2015, 48, 7049.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Axial skeleton anterior-posterior patterning is regulated through feedback regulation between Meis transcription factors and retinoic acid.

Vertebrate axial skeletal patterning is controlled by co-linear expression of Hox genes and axial level-dependent activity of HOX protein combinations. MEIS transcription factors act as co-factors of HOX proteins and profusely bind to Hox complex DNA; however, their roles in mammalian axial patterning remain unknown. Retinoic acid (RA) is known to regulate axial skeletal element identity through the transcriptional activity of its receptors; however, whether this role is related to MEIS/HOX activity remains unknown. Here, we study the role of Meis in axial skeleton formation and its relationship to the RA pathway in mice. Meis elimination in the paraxial mesoderm produces anterior homeotic transformations and rib mis-patterning associated to alterations of the hypaxial myotome. Although Raldh2 and Meis positively regulate each other, Raldh2 elimination largely recapitulates the defects associated with Meis deficiency, and Meis overexpression rescues the axial skeletal defects in Raldh2 mutants. We propose a Meis-RA-positive feedback loop, the output of which is Meis levels, that is essential to establish anterior-posterior identities and patterning of the vertebrate axial skeleton.This research was supported by the Ministerio de Ciencia, Innovación y Universidades (PGC2018-096486-B-I00), the Instituto de Salud Carlos III (RD16/ 0011/0019) and by the Comunidad de Madrid (S2017/BMD3875). The Centro Nacional de Investigaciones Cardiovasculares Carlos III is supported by the Ministerio de Ciencia, Innovación y Universidades and the Pro Centro Nacional de Investigaciones Cardiovasculares Carlos III Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). A.C.L.-D. was the recipient of a Formación Personal Investigador fellowship from the Ministerio de Economı́a y Competitividad (BES-2013-064374).S

Paleoliquefaction in the Bajo Segura basin (eastern Betic Cordillera)

The Bajo Segura basin, in the eastern Betic Cordillera, displays a seismic activity characterized by small-magnitude earthquakes (1.5-4.5 mb), with some occasional moderate to high-magnitude events (> 5.0 mb). These earthquakes are produced by the activity of blind faults without surface ruptures. For this reason, the detection of paleoearthquakes in the geological record is limited to indirect evidence of paleoseismicity, mainly liquefaction features. Moreover, such evidence is abundant in the historical record of the 1829 Torrevieja earthquake, in some of its aftershocks and in the 1919 Jacarilla earthquake. In this study several layers of Holocene seismites previously described in the basin were analyzed, and correlated with various radiometric 14C datings. This analysis enabled a recurrence period of approx. 1000 yr to be established for the moderate to high-magnitude earthquakes in the Bajo Segura basin.La cuenca del Bajo Segura, localizada en la Cordillera Bética oriental, tiene una actividad sísmica caracterizada principalmente por terremotos de pequeña magnitud (1.5-4.5 mb), aunque ocasionalmente han ocurrido terremotos de magnitud moderada-alta (> 5 mb). Estos terremotos están producidos por la actividad de fallas que no presentan ruptura en superficie (fallas ciegas). Por este motivo, el reconocimiento de paleoterremotos en el registro geológico se limita a las evidencias indirectas de paleosismicidad entre las que destacan las estructuras de licuefacción sísmica. Además se tiene constancia de numerosas manifestaciones de licuefacción en el terremoto histórico de Torrevieja de 1829, en alguna de sus réplicas y en el terremoto de Jacarilla de 1919. En este trabajo se han analizado varios niveles de sismitas holocenas descritos previamente en la cuenca, y se han correlacionado con varias dataciones radiométricas de 14 C . Este análisis ha permitido establecer un periodo de recurrencia de terremotos de magnitud moderada-alta en la cuenca del Bajo Segura, de aproximadamente 1000 años

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 {\AA} range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C$^{2+}$ and/or O$^{2+}$ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic HII regions and comparing with results for halo stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy a different locus in the C/O vs. O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic HII regions should have the same origin than in halo stars. The comparison between the C/O ratios in HII regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for HII regions and that this coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Paleoliquefaction in the Bajo Segura basin (eastern Betic Cordillera)

The Bajo Segura basin, in the eastern Betic Cordillera, displays a seismic activity characterized by small-magnitude earthquakes (1.5-4.5 mb), with some occasional moderate to high-magnitude events (> 5.0 mb). These earthquakes are produced by the activity of blind faults without surface ruptures. For this reason, the detection of paleoearthquakes in the geological record is limited to indirect evidence of paleoseismicity, mainly liquefaction features. Moreover, such evidence is abundant in the historical record of the 1829 Torrevieja earthquake, in some of its aftershocks and in the 1919 Jacarilla earthquake. In this study several layers of Holocene seismites previously described in the basin were analyzed, and correlated with various radiometric 14C datings. This analysis enabled a recurrence period of approx. 1000 yr to be established for the moderate to high-magnitude earthquakes in the Bajo Segura basin

The role of fungi in the cocoa production chain and the challenge of climate change

Background: The role of fungi in cocoa crops is mainly associated with plant diseases and contamination of harvest with unwanted metabolites such as mycotoxins that can reach the final consumer. However, in recent years there has been interest in discovering other existing interactions in the environment that may be beneficial, such as antagonism, commensalism, and the production of specific enzymes, among others. Scope and approach: This review summarizes the different fungi species involved in cocoa production and the cocoa supply chain. In particular, it examines the presence of fungal species during cultivation, harvest, fermentation, drying, and storage, emphasizing the factors that possibly influence their prevalence in the different stages of production and the health risks associated with the production of mycotoxins in the light of recent literature. Key find-ings and conclusion: Fungi associated with the cocoa production chain have many different roles. They have evolved in a varied range of ecosystems in close association with plants and various habitats, affecting nearly all the cocoa chain steps. Reports of the isolation of 60 genera of fungi were found, of which only 19 were involved in several stages. Although endophytic fungi can help control some diseases caused by pathogenic fungi, climate change, with increased rain and tempera-tures, together with intensified exchanges, can favour most of these fungal infections, and the presence of highly aggressive new fungal genotypes increasing the concern of mycotoxin production. For this reason, mitigation strategies need to be determined to prevent the spread of disease-causing fungi and preserve beneficial ones

Investigation of the long effective conjugation length in defect-free insulated molecular wires

Due to the “insulation” of the π-conjugated backbones, insulated molecular wires (IMWs) are expected to be applied to various optoelectronic applications and nanotechnology.[1] Recently, Kazunori et al have succeeded in the synthesis of a self-threading polythiophene with a polyrotaxane-like 3D architecture (PSTB, see Figure 1), for which an intrawire hole mobility of 0.9 cm2 V−1 s−1 has been measured.[2] Here, we aim to evaluate the extent of π-conjugation along polythiophene backbones sheathed within defect-free “insulating” layers. A comparison between the experimental Raman spectra of the self-threading oligomers (i.e. 2STB-5STB) and the corresponding PSTB polymer indicates that: (i) the ratio of relative intensities of the two most intense Raman bands (I1375/1445) increases with the elongation of the size chain but does not saturate up to the pentamer, and (ii) π-conjugation spreads over 17–18 thiophene units in the polymer. Whether the effective conjugation length of the polymer is better described by using the long oligomer extrapolation approach[3] or periodic DFT calculations of the polymer is discussed in detailed by exploiting the very recent potentialities of state-of-the-art quantum chemical simulations of vibrational properties for crystalline solids.[Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Materiales conjugados en electrónica orgánica: aspectos electrónicos y estructurales

En nuestro actual “mundo electrónico” existe un creciente interés en el diseño y fabricación de dispositivos electrónicos orgánicos, con propiedades ecológicas y de alta calidad. A diferencia de aquéllos basados en el silicio, se caracterizan por tener un bajo coste, ser ligeros, flexibles, solubles, imprimibles y con posibilidad de interacción con sistemas biológicos. Aparte de ser una realidad comercial reciente (OLEDs, OFETs, células solares orgánicas), nuevas moléculas1,2 y polímeros3-5 constituyen un objeto de investigación actual. En la presente comunicación se detalla el estudio de las características electrónicas y moleculares de diversas estructuras π-conjugadas (moleculares y poliméricas), para evaluar su potencial como semiconductores en diversos materiales electrónicos orgánicos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cálculos DFT en materiales orgánicos conjugados: importancia en el análisis de los datos experimentales

Actualmente, y cada vez con mayor intensidad, los materiales orgánicos policonjugados se están erigiendo como la alternativa ecológica real al uso de silicio en materiales para dispositivos electrónicos. Este hecho se debe principalmente a una serie de ventajas que presentan frente a los materiales inorgánicos tradicionales, tales como bajo coste de producción, ligereza, flexibilidad, disponibilidad para ser impresos y posibilidad de interacción con material biológico. Éstos pueden estar constituidos por diferentes estructuras, desde moléculas discretas a polímeros, pasando por macromoléculas de mayor complejidad (fullereno, nanotubos, grafeno…). Hoy en día es posible encontrarlos integrados en dispositivos electrónicos como diodos emisores de luz orgánicos (OLEDs), células solares orgánicas (OSCs) y transistores orgánicos de efecto campo (OFETs) y presentados en diferentes soportes1, constituyendo de este modo parte fundamental de la actualidad tecnológica comercial. Dado su impacto, son uno de los principales objetos de estudio, ya sea como estructuras moleculares2,3 o poliméricas4-6. En el trabajo desarrollado se analizan las estructuras electrónicas y moleculares de diferentes materiales π-conjugados, las modificaciones que se pueden ejercer en los mismos y las propiedades exclusivas derivadas de éstas, pudiendo, de este modo, determinar su capacidad como potencial material semiconductor en aplicaciones optoelectrónicas. Para ello se han llevado a cabo una serie de experimentos (espectroscopía Raman y espectroscopía electrónica de absorción) cuyo resultado ha sido analizado en profundidad utilizando cálculos químico-cuánticos en DFT como herramienta analítica. Gracias, por tanto, a los cálculos realizados, es posible obtener una visión completa del comportamiento electrónico observado en diferentes modelos moleculares y poliméricos, así como esclarecer la causa que genera ciertos comportamientos inéditos hasta el momento en este tipo de materiales.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec