White-emitting organometallo-silica nanoparticles for sun-like light-emitting diodes

This work discloses a radically new way to prepare white-emitting hybrid nanoparticles, whose implementation in lighting devices provides encouraging proof-of-concept performances towards alternative sunlight sources. In detail, the new synthetic approach is based on the kinetic control of the formation of organometallic dots, built via the condensation of three emitting iridium(III) complexes, which are subsequently transformed into mesoporous silica nanoparticles. Our novel hybrid systems, which are exceptionally stable under harsh irradiation and thermal stress environments, show a bright white emission with a record photoluminescence quantum yield. Their remarkable performance prompted us to implement them into single-component hybrid light-emitting diodes (HLEDs), achieving a high-quality sunlight source that is stable for >2000 hours with linearly extrapolated stabilities of >10 000 h. This represents one of the most stable HLEDs reported so far, while the versatility of our synthesis approach with respect to the type of emitters opens new opportunities for the design and fabrication of white-emitting color down-converters for HLEDs in the future.C. E., E. L. and J. R. B acknowledge Spanish MINECO and AEI/FEDER (ref. CTQ2016-78463-P). C. E. also thanks Universidad de La Rioja for a grant. E. F. and R.D.C. acknowledge the program “Ayudas para la atracción de talento investigador – Modalidad 1 of the Consejería de Educación, Juventud y Deporte – Comunidad de Madrid with the reference number 2016-T1/IND-1463”. R. D. C. acknowledges Spanish MINECO for the Ramón y Cajal program (RYC-2016-20891). J.G.M. acknowledges Spanish MINECO and AEI/FEDER (ref. CTQ2014-60017-R). E.S. thanks Spanish MINECO and AEI/FEDER (ref. CTQ2015-74494-JIN) and the University of Alicante (“Ayudas para la captación de talento” program with the reference number UATALENTO16-03)

Hybrid organometallo-silica catalysts for sustainable visible-light promoted olefin isomerization

The use of visible light as a clean and affordable reagent has turned photocatalysis into a green and powerful tool in synthetic chemistry. However, most of these photocatalytic processes are carried out under homogeneous conditions, which requires expensive catalysts that are difficult to recover and recycle. One way to overcome this problem is to incorporate the visible-active species into porous solid matrices. However, integrating these active species into the matrix to achieve a stable and active heterogeneous photocatalyst is not easy, and has usually been done by post-synthetic strategies. Herein, we describe the use of the highly emissive cyclometalated complex [Ir(dfppy)2(dasipy)]PF6 as a building block for the in-situ synthesis of four different silica-based heterogeneous photocatalysts, and a related post-synthetic grafted material. These highly stable materials have been assessed in the energy transfer photo-isomerization reaction of trans- to cis-stilbene under blue light and mild conditions; showing not only high isomerization yields (ca. 80 %), but also easy recovery and excellent recyclability (up to 100 % after 7 cycles).This work was supported by the Spanish MCIN/AIE/10.13039/501100011033, the ‘‘ERDF A way of making Europe’’, the ‘‘European Union’’ (projects PID2019-109742GB-I00 and PID2021-128761OB-C21), Gobierno de la Rioja (Project FORTALECE 2021/01) and Generalitat Valenciana (Regional Project AICO/2021/037 - Conselleria d’Innovació, Universitats, Ciència i Societat Digital)

Meeting High Stability and Efficiency in Hybrid Light‐Emitting Diodes Based on SiO2/ZrO2 Coated CsPbBr3 Perovskite Nanocrystals

Significant advances are realized in perovskite‐converted hybrid light‐emitting diodes (pc‐HLEDs). However, long‐living devices at high efficiencies still represent a major milestone with average stabilities of <200 h at ≈50 lm W−1 under low applied currents (<15 mA). Herein, a dual metal oxide‐coated CsPbBr3@SiO2/ZrO2 composite is prepared in a one‐pot synthesis through the kinetic control of the sol–gel reaction, followed by a gentle drying process in air. These hybrid nanoparticles show photoluminescence quantum yields of ≈65% that are stable under temperature, ambient, and irradiation stress scenarios. This is translated to pc‐HLEDs with a near‐unity conversion efficiency at any applied current, high efficiencies around 75 lm W−1, and one of the most remarkable stabilities of ≈200 and 700 h at 100 and 10 mA, respectively. In addition, the device degradation mechanism is thoughtfully rationalized comparing devices operating under ambient/inert conditions. As such, this work provides three milestones: i) a new room temperature one‐pot protocol to realize the first SiO2/ZrO2 metal oxide coating that effectively protects the emitting perovskite nanoparticle core, ii) one of the most stable and efficient pc‐HLEDs operating under ambient condition at any applied current, and iii) new insights for the degradation of pc‐HLEDs.R.D.C. acknowledges the program “Ayudas para la atracción de talento investigador—Modalidad 1 of the Consejería de Educación, Juventud y Deporte—Comunidad de Madrid with the Reference No. 2016‐T1/IND‐ 1463,” Spanish Ministry of Economy and Competitiveness (MINECO) for the Ramón y Cajal program (RYC‐2016‐20891), and HYNANOSC (RTI2018‐099504‐A‐C22). Y.Y.D. also thanks the financial support from China Scholarship Council (No. 201808440326). This work was supported by the Spanish MICINN and Agencia Estatal de Investigación (AEI)/European Regional Development Fund (FEDER) (Projects CTQ2015‐74494‐JIN, CTQ2016‐78463‐P, RTI2018‐099504‐B‐C21/A‐C22, and PID2019‐109742GB‐I00). E.S. thanks Universidad de Alicante through the “Programa de Retención de Talento” (ref. UATALENTO16‐03) and C.E. thanks Universidad de La Rioja for a grant. Open access funding enabled and organized by Projekt DEAL

Highly emissive hybrid mesoporous organometallo-silica nanoparticles for bioimaging

Production of mesoporous silica nanoparticles (MSNs) with uniform textural characteristics and imaging properties on a large scale is still a challenge. Thus, the design of simple and scalable methods to obtain reproducible functionalized MSNs has become even more relevant. Herein, we describe an in situ strategy for the synthesis and surface functionalization of highly luminescent mesoporous organometallo-silica nanoparticles. Using the [Ir(dfppy)2(dasipy)]PF6 chromophore and TEOS as sol–gel precursors and different capping agents, such as DMDES or APTES, three different emissive MSNs were prepared (NPOH_IS, NPMe_IS and NPNH2_IS), each containing hydroxyl, methyl and amine groups on their surfaces, respectively. All three were tested on human tumor A549 (lung carcinoma) and HeLa (cervix carcinoma) cell lines, showing intense and stable yellow phosphorescence, biocompatibility and efficient internalization. Moreover, NPMe_IS nanoparticles showed excellent colloidal stability, both in water and biological media, and a BET area of 1120 m2 g−1, making them not only luminescent biomarkers, but potentially also controlled delivery vectors.This work was supported by the Spanish MCIN/AIE/10.13039/501100011033 and by “ERDF A way of making Europe”, by the “European Union” (projects CTQ2015-74494-JIN, RTI2018-099504-B-C21 and PID2019-109742GB-I00) and the Agencia de Desarrollo Económico de La Rioja (Gobierno de la Rioja. Project 2017-I-IDD-00031). E.S. also thanks the University of Alicante through the “Programa de Retención de Talento” (ref. UATALENTO16-03). E.A.-A. is grateful to the Spanish Association Against Cancer (AECC) for her Ph.D. fellowship

Bottom-up construction of highly photoactive dye-sensitized titania using Ru(II) and Ir(III) complexes as building blocks

The one-pot co-condensation of tetrabutyl orthotitanate (TBOT) and the neutral Ru(II) N3 dye or the new cationic Ir(III) complex [Ir(ppy)2(3,3′-H2dcbpy)]PF6 have yielded novel hybrid in-situ titanias, which present an exceptional stability against leaching or photodegradation of the coordination dye. The main advantages of this strategy are: i) high dye incorporation level, ii) narrowing band gap and iii) high stability. These materials exhibit much higher photocatalytic activity, under both UV and visible light, not only than the dye-free titania but also than the related dye-sensitized titania prepared by post-synthetic grafting. This in-situ synthetic approach is a promising alternative route to prepare highly stable dye-sensitized materials with great applicability potential.We thank the Spanish MINECO (Projects CTQ2013-45518-P and CTQ2014-60017-R) for financial support

Diseño y aplicaciones de materiales híbridos fotoactivos

El trabajo realizado se ha centrado en la importancia de incorporar adecuadamente compuestos organometálicos fotoactivos en matrices de sólidos inorgánicos, con el fin de mejorar sus propiedades y ampliar sus aplicaciones potenciales. Así, se ha diseñado una ruta sintética in-situ basada en la Química de la Coordinación Sol-Gel con gran versatilidad, que ha permitido preparar diferentes tipos de materiales híbridos fotoactivos de sílice y de titania. El estudio comparativo realizado entre los materiales sintetizados mediante la nueva aproximación in-situ y los obtenidos a partir de estrategias post-sintéticas tradicionales, nos ha permitido mostrar la versatilidad y fortaleza de este nuevo método sintético. Con este fin, se han sintetizado y caracterizado diversos compuestos catiónicos de Ir(III) y Pt(II) de estequiometria [Ir(C^N)2L2]+ y [Pt(C^N)L2]+, respectivamente, donde C^N se corresponde con ligandos ciclometalados, y L con ligandos neutros de tipo bipiridina o fosfina funcionalizados con grupos trialcoxisilano (PPTES = PPh2(CH2)2Si(OEt)3, dasipy = 4,4-[CONH(CH2)3Si(OEt)3]2-bipiridina). Tras el estudio completo de sus propiedades físicas y ópticas, se ha llevado a cabo la síntesis de los correspondientes materiales mesoporosos híbridos organometallo-silica, mediante la ruta in-situ. Esta técnica se ha podido adaptar exitosamente a cromóforos organometálicos con características estructurales y electrónicas diferentes (geometrías octaédricas o plano-cuadradas, derivados catiónicos o neutros, con uno o varios grupos alcoxisilano). Además, introduciendo pequeñas modificaciones en las condiciones de reacción, se han podido obtener materiales híbridos luminiscentes de base silícea que presentan diferentes morfologías y propiedades texturales. Así, se han preparado desde materiales macroscópicos nanoestructurados (SiO2_P y SiO2_G), a nanopartículas discretas con acabados superficiales distintos (NPOH, NPMe y NPAPTES). En general, los materiales híbridos obtenidos presentan propiedades fotofísicas mejoradas, incrementando, además, la estabilidad de los cromóforos organometálicos incorporados. Esta metodología es relativamente flexible y permite obtener materiales que mimetizan el comportamiento emisivo de los cromóforos en estado sólido o en disolución, dependiendo de la concentración y condiciones de reacción empleados. Todas estas características han permitido utilizar estos materiales en una gran variedad de aplicaciones como geles luminiscentes ópticamente transparentes, dispositivos emisores de luz o biomarcadores. Así, y gracias a la colaboración que mantenemos con los grupos de investigación del Prof. Javier García-Martínez (Universidad de Alicante), el Dr. Rubén D. Costa (IMDEA Materiales, Madrid) y el Dr. José Manuel García Pichel (Centro de Investigación Biomédica de La Rioja, CIBIR), hemos podido probar estos materiales híbridos como sustratos en la fabricación de LEDs emisores de luz blanca y como biomarcadores. Por otro lado, se ha conseguido adaptar la estrategia sintética de la Química de la Coordinación Sol-Gel a la preparación de materiales basados en titania. Para ello, se han sintetizado dos derivados de Ir(III) y Ru(II), debidamente funcionalizados con grupos carboxilato, [Ir(ppy)2(3,3-H2dcbpy)]PF6 y [Ru(4,4-H2dcbpy)2(NCS)2]. Su posterior reacción de condensación con la fuente de titania, TBOT, ha permitido obtener unos materiales híbridos (TiO2_IS) con saltos electrónicos más pequeños que los correspondientes a la titania de control y a materiales similares obtenidos mediante técnicas post-sintéticas (TiO2_G). Todo ello afecta positivamente a su actividad fotocatalítica, no solo bajo irradiación UV sino también bajo luz visible. Este hecho, sin precedentes en la bibliografía, permite ampliar el abanico de posibilidades a la hora de diseñar materiales semiconductores fotoactivos altamente estables, con posibilidad de reutilización tras varios ciclos catalíticos de fotodegradación de materia orgánica. Estas características se atribuyen a la buena integración de los complejos fotoactivos en la matriz de anatasa, que les confiere una alta protección y una estabilidad excepcional. En conjunto, creemos que todas estas características, junto con la facilidad de modular las condiciones de reacción y la protección adicional que la matriz inorgánica confiere a los cromóforos incorporados, suponen un avance importante y un gran potencial a la hora de diseñar diferentes tipos de sistemas fotoactivos.Along this PhD work, we have manifested the importance of incorporating photoactive materials into inorganic matrices, with the aim of improving their properties and expanding their potential applications. In this sense, it has been designed a synthetic route based on the Sol-Gel Coordination Chemistry with a great versatility, allowing us to obtain different types of photoactive hybrid silica- and titania-based materials. Comparative studies performed between materials prepared following the new in-situ approach and those obtained by post-synthetic strategies allowed us to show their more notable strengths. With this aim, we have synthetized and characterized several cationic Ir(III) and Pt(II) complexes of the type [Ir(C^N)2L2]+ and [Pt(C^N)L2]+, respectively, where C^N corresponds to cyclometalated ligands, and L to neutral bipyridine and phosphine ligands functionalized with trialkoxysilane groups (PPTES = PPh2(CH2)2Si(OEt)3, dasipy = 4,4-[CONH(CH2)3Si(OEt)3]2-bipyridine). After the study of their photophysical properties, we prepared the corresponding hybrid organometallo-silica materials following the in-situ approximation. It has been demonstrated that this technique can be easily adapted to chromophores with different structural and electronic features (octahedral or square-planar geometries, cationic or neutral derivatives, with one or several alkoxysilane groups). In addition, using a single silica source (TEOS) and just slightly modifying the reaction conditions, luminescent hybrid silica-based materials with different morphologies and textural properties have been obtained. Thus, we have prepared macroscopic nanostructured materials (SiO2_P and SiO2_G) and discrete nanoparticles with different superficial modifications (NPOH, NPMe and NPAPTES). Generally, the new hybrid materials display better physical properties and stabilities than those of the organometallic chromophores incorporated. This methodology is relatively flexible and has allowed us to obtain materials that mimic the photoemission of the organometallic precursor in the solid state or in solution, depending on the concentration used. All these features allowed us to use these hybrid silica materials in a wide range of topics as optically transparent gels, light emitting devices or biomarkers. Thus, and thanks to collaborations with the research groups of Dr. Rubén D. Costa (IMDEA Materiales, Madrid) and Dr. José Manuel García Pichel (Centro de Investigación Biomédica de La Rioja, CIBIR), we have tested the silicas as substrates for the fabrication of white-emitting LEDs and as biomarkers, respectively. On the other hand, we have successfully adapted this Sol-Gel Coordination Chemistry approach to the preparation of titania-based materials. With is aim, we synthetized two Ir(III) and Ru(II) complexes, bearing bipyridine ligands with carboxylic groups, [Ir(ppy)2(3,3-H2dcbpy)]PF6 y [Ru(4,4-H2dcbpy)2(NCS)2]. The condensation reaction between them and TBOT yield hybrid titania materials (TiO2_IS) with narrower band gaps than those observed for the complex-free control titania and for other materials obtained following post-synthetic techniques (TiO2_G). All these features are the responsible of their improved photocatalytic performance, not only under UV light but also under visible irradiation. This fact, unprecedented in the bibliography, allows to broaden the possibilities for the design of new and stable photoactive materials, able to be used after several catalytic cycles for the photodegradation of organic compounds. This improved stability should be attributed to the good integration of the photoactive complexes inside the anatase matrix, which provides them with additional protection and stability. All these features, together with the ease modulation of the reaction conditions and the extra protection provided by the inorganic matrix to the incorporated chromophores, represent an important advance in the design of photoactive systems