Examinando por Autor "Segura, José Luis"

Mostrando 1 - 4 de 4

Highly efficient solution-processed white organic light-emitting diodes based on novel copolymer single layer
(Elsevier, 2012) Coya, Carmen; Álvarez, Ángel Luis; Ramos, Mar; Gómez, Rafael; Seoane, Carlos; Segura, José Luis
We fabricate by solution processed methods organic light emitting diodes with single-layer structure (ITO/(PEDOT:PSS)/co-polymer/Ba/Al) and study the transport properties of the final devices. The copolymer is novel poly(fluorene-alt-phenylene) (PFP) derivatives containing co-monomers, involving red-emitting 1,8-naphthalimide units as pendant groups (0.0005, 0.005, 0.02 and 0.08 wt%) covalently attached. All the devices exhibited emission at very low driving currents in the A range (47¿73 A). White emission with luminous efficiency of 9.42 Cd/A at 50 A is obtained for the co-polymer with the smallest amount of chromophore. Commission Internationale de L¿Eclairage (CIE) coordinates evolve from almost pure white color (0.26, 0.30) for low currents to stable cool white (0.21, 0.23). Increasing naphthalimide contents leads to stable green and orange emission with 3.07, 19.5 and 6.7 Cd/A efficiencies. The current-voltage response of the devices is analyzed by means of a numerical model that includes an injection mechanism based in the microscopic hopping theory and a field-dependent carrier mobility for the bulk transport regime. The fitting results allow to estimate the dependence of carrier mobility on polymer composition in the diodes.
Novel synthetic approaches towards hexaazatriphenylene (HAT) derivatives
(Universidad Rey Juan Carlos-Universidad Complutense, 2008) Juárez, Rafael; Ramos, María Mar; Segura, José Luis
Large two-dimensional molecules with extended ¿-systems are subject of increasing interest as a consequence of their technological applications. In particular, hexaazatriphenylene (HAT) derivatives, present a great interest due to the influence of heteroatoms on the electronic nature without modifying the structure. HAT derivatives have recently attracted attention as materials for organic electronic applications1 and depending on the choice of substituent can have a variety of applications (discotic liquid-crystals, n-type semiconducting, magnetic materials or fluorescent dyes).2 Whereas HATs carrying six identical substituents are well known following different synthetic approaches, the synthesis of non-centrosymmetric HAT derivatives is still quite rare. In our working group we are centered in two main routes for affording HAT derivatives. One route affords a variety of symmetrical HAT derivatives including HAT condensed systems. On the other hand, we have also synthesized non-centrosymetric ¿-conjugated donor-acceptor molecules bearing a HAT core and donor groups in the periphery.3 In this communication we present a new soluble ¿-deficcient derivative which consists of three HAT molecules condensed around a central aromatic core so we have named it triHAT. We have found triHAT to be 0.75 V better acceptor than HAT in itself. We also present a new synthetic route in order to obtain non-centrosymetric ¿-conjugated donor-acceptor molecules bearing a HAT core and donnor groups in the periphery. This synthesis paves the way for further conjugated donnor-acceptor derivatives of HAT.
Scalable Synthesis and Electrocatalytic Performance of Highly Fluorinated Covalent Organic Frameworks for Oxygen Reduction
(Wiley VCH, 2023-10-16) Ramos, Mar; Martínez-Fernández, Marcos; de la Peña, Alejandro; Segura, José Luis; Rodríguez-San-Miguel, D; Zamora, Felix; Martínez-Periñán, E; Lorenzo, E; Aguilar-Galindo, F; Cabrera-Trujillo, J.J.; Vismara, R.; Navarro, J.A.R.
Abstract: In this study, we present a novel approach for the synthesis of covalent organic frameworks (COFs) that overcomes the common limitations of non-scalable solvothermal procedures. Our method allows for the roomtemperature and scalable synthesis of a highly fluorinated DFTAPB-TFTA-COF, which exhibits intrinsic hydrophobicity. We used DFT-based calculations to elucidate the role of the fluorine atoms in enhancing the crystallinity of the material through corrugation effects, resulting in maximized interlayer interactions, as disclosed both from PXRD structural resolution and theoretical simulations. We further investigated the electrocatalytic properties of this material towards the oxygen reduction reaction (ORR). Our results show that the fluorinated COF produces hydrogen peroxide selectively with low overpotential (0.062 V) and high turnover frequency (0.0757 s􀀀 1) without the addition of any conductive additives. These values are among the best reported for non-pyrolyzed and metal-free electrocatalysts. Finally, we employed DFT-based calculations to analyse the reaction mechanism, highlighting the crucial role of the fluorine atom in the active site assembly. Our findings shed light on the potential of fluorinated COFs as promising electrocatalysts for the ORR, as well as their potential applications in other fields.
Uracil grafted imine-based covalent organic framework for nucleobase recognition
(Royal Soc Chemistry, 2018) Royuela, Sergio; García-Garrido, Eduardo; Martín Arroyo, Miguel; Mancheño, María José; Ramos, Maria M; Gonzalez Rodríguez, David; Somoza, Alvaro; Zamora, Félix; Segura, José Luis
An imine-based covalent organic framework (COF) decorated in its cavities with uracil groups has shown selective recognition towards adenine in water. These results show how the confinement of the base-pair inside the COF’s pores allows a remarkable selective recognition in aqueous media.