Molecular Antennas and Photoactive Nanomaterials based on Energy Transfer Processes

110 p.The scope of this thesis deals is the development and description of photoactive nanomaterials and novel multichromophoric systems as artificial antenna systems. To this aim, the photophysical signatures of luminescent fluorophores (with absorption and emission at different regions of the visible electromagnetic spectrum) encapsulated into inorganic and organic hosts, or assembled in supramolecular structures have been exhaustively characterized. These systems are able to harvest the light over a broad spectral region (ultraviolet-visible) and transfer it to the target place and with a specific energy via successive energy transfer hops. As consequence the excitation can be performed far away from the emission region, improving the photostability of the acceptor emitting dye and a lowering the background interferences. In pursuit of such antennas, different alternatives have been considered, (i) Hybrid materials based on LTL zeolites doped with laser dyes working in the blue, green or red parts of the visible. (ii) Latex nanoparticles doped simultaneously with luminescent fluorophores, leading to stable aqueous colloids. (iii) Molecular cassettes based on energy donor and acceptor dyes covalently linked. All of them undergoing efficient and tunable energy transfer processes, the key factor for a successful development of luminescent antennas. In conclusion, the herein reported approaches (photoactive materials and novel dyes) towards the development of luminescent antennas are shown to be properly applied in photonic fields such as tunable dye lasers, light modulators or polarity probe

The subtlety of gender stereotypes in the workplace:Current and future directions for research on the glass cliff

Glass cliff effects are context dependent and multiply determined, resulting in mixed evidence and remaining gaps in our understanding of the phenomenon. In this chapter, we review existing evidence about the think crisis-think female association, identifying particular challenges and opportunities that women face as crisis management leaders. We examine how glass cliff research points to three main factors that may attenuate the think male-think manager stereotype in difficult organizational contexts: (1) women's perceived higher communal orientations (stereotype-based explanations), (2) associations of women with organizational transformations (signaling change explanations), and (3) limited ethical standards that expose women to failure (hostile explanations). To better understand these interpretations and identify the specific contexts in which women are likely to emerge as leaders, we call for a theoretical and empirical refinement of current conceptualizations of crises, as well as a more thorough analysis of the many-sided consequences of these associations for women's career

Emotional Androgyny: A Preventive Factor of Psychosocial Risks at Work?

Although previous studies have acknowledged the connections between gender and emotional competences, more research is needed on how gender and emotion interact to influence psychosocial risks at work. This paper addresses how gender stereotypes and emotions simultaneously act as psychosocial antecedents of organizational stress. Following the principles of psychological androgyny, we propose that a combination of communion and agency can serve as a preventive factor at work and lead to healthier responses by providing a wider range of emotional competences to deal with organizational demands. Following previous methodological approaches, we include a quantitative review about scientific research on occupational health in the PsycINFO database during the period 1980–2017 from a multidimensional gender perspective that differentiates between studies addressing the topic from either sex, gender or gender identity dimensions. Finally, we propose new analytical directions to deal with psychosocial hazards at work by underscoring some of the complex ways in which gender and emotional competences influence psychosocial risks at work

Photoactive Nanomaterials Inspired by Nature: LTL Zeolite Doped with Laser Dyes as Artificial Light Harvesting Systems

The herein reported work describes the development of hierarchically-organized fluorescent nanomaterials inspired by plant antenna systems. These hybrid materials are based on nanostructured zeolitic materials (LTL zeolite) doped with laser dyes, which implies a synergism between organic and inorganic moieties. The non-interconnected channeled structure and pore dimensions (7.1 angstrom) of the inorganic host are ideal to order and align the allocated fluorophores inside, inferring also high thermal and chemical stability. These artificial antennae harvest a broad range of chromatic radiation and convert it into predominant red-edge or alternatively white-light emission, just choosing the right dye combination and concentration ratio to modulate the efficiency of the ongoing energy transfer hops. A further degree of organization can be achieved by functionalizing the channel entrances of LTL zeolite with specific tailor-made (stopcock) molecules via a covalent linkage. These molecules plug the channels to avoid the leakage of the guest molecules absorbed inside, as well as connect the inner space of the zeolite with the outside thanks to energy transfer processes, making the coupling of the material with external devices easier.This work was supported by the Basque Government (IT912-16) and Spanish MICINN (MAT2014-51937-C3-3-P) projects. Leire Gartzia also thanks the Basque Goberment for a Post-doctoral grant. Yi Xiao from Dalian University (China) is kindly acknowledged for the supply and synthesis of the stopcock molecule

Liquid-crystalline, liquid-ordered, rippled and gel lipid bilayer phases as observed with nile red fluorescence

The basic matrix of cellular membranes consists of a double layer (bilayer) of phospholipids. Semisynthetic lipid bilayers are commonly used in biophysical studies of membranes. According to tem-perature and composition, lipid bilayers can exist in liquid-crystalline (or liquid-disordered), liquid -ordered, rippled, and gel phases. In the present study, the hydrophobic, solvatochromic molecule Nile red has been used as a fluorescent probe to examine the physical state of bilayers of different composi-tions in the 15-60 degrees C range. Phospholipids with saturated or unsaturated acyl chains, in the presence or absence of cholesterol have been studied. Nile red shows absorption maxima at 520-550 nm and emis-sion maxima at 580-640 nm, single photon excitation not being damaging to the system. A red/orange intensity ratio (ROIR) index has been used to normalize the results. ROIR varies clearly and reproducibly with the lipid phase, increasing in the order: liquid-ordered < gel < rippled < liquid-crystalline. It increases with temperature and decreases with cholesterol contents in the bilayers. Nile red allows an unusually clear observation of the rippled-to-liquid crystalline phase transition in saturated phospho-lipids. FLIM studies with Nile red also show differences between lamellar phases. Rotational relaxation times have been determined for Nile red in liquid-disordered (0.72 +/- 0.010 ns), gel (1.16 +/- 0.070 ns), and liquid-ordered (1.79 +/- 0.14 ns) phases, the large value of the liquid-ordered phase being an indication of the sterol hindering probe tumbling in the hydrophobic matrix.This work was supported in part by the Spanish Ministerio de Ciencia e Innovación (MCI), Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (grants No. PGC2018-099857-B-I00, PID2020-114755GB-C33 ), by the Basque Government (grants No. IT1625-22, IT1639-22,and IT1270-19), by Fundación Ramón Areces (CIVP20A6619), by Fundación Biofísica Bizkaia, and by the Basque Excellence Research Centre (BERC) program of the Basque Government

Linde Type L Zeolite: A Privileged Porous Support to Develop Photoactive and Catalytic Nanomaterials

Among the wide assortment of zeolites based on aluminosilicates, Linde Type L (LTL) zeolite outstands as a support host owing to its porous framework and high adsorption surfaces. Thus, the incorporation of suitable guest molecules (fluorophores or metals) allows the development of photoactive and catalytic nanomaterials. In this chapter, we describe the design of materials based on LTL zeolite to achieve artificial antennae, inspired in the natural photosynthesis, and ecofriendly materials for the catalytic reforming of biogas. First, we describe the microwave-assisted synthesis of LTL zeolite with tunable size and morphology. Afterward, we test the energy transfer probability between the guest fluorophores into the LTL zeolite pores as the key process enabling the antenna behavior of this hybrid material with broadband absorption and tunable emission or predominant red fluorescence. Finally, we also test the behavior of LTL zeolite as a support material for the catalytic reforming of biogas. To this aim, suitable metals were impregnated onto LTL zeolite featuring different shapes and alkaline metal exchange. Activity tests indicated that disk- and cylinder-shaped hosts were the most active ones, especially when bimetallic (Rh-Ni) catalysts were prepared. However, the alkaline metal exchange was ineffective to increase the hydrogen yield

Balizko molekula fotoaktibo multifuntzionala biomedikuntzarako

Light-emitting organic molecules are appealing for diagnosis in biomedicine. Fluorescence is a valuable tool to visualize ongoing biochemical processes and biomolecules in the human body with great sensibility and easily. Thus, photoactive dyes are applied as fluorescent tags, probes and sensors to monitor biochemical processes, organelles and biomolecules, respectively, by means of fluorescence microscopy. Moreover, no-fluorescent dyes but able to generate singlet oxygen can be applied as photosensitizers for photodynamic therapy in the treatment of cancer. In each of the aforementioned areas dealing with biophotonics, different chromophores are required owing to the opposite photophysical signatures demanded. Herein, we propose BODIPY called chromophore as a molecular scaffold for diagnosis and therapy. The chemical versatility and tunable photophysics of this chromophoric core enables tailoring by the appropriate substitution pattern. Therefore, our aim is to highlight the importance of molecular design to develop fluorophores as well as photosensitizers based solely in BODIPY.; Argia igortzeko gai diren molekula organikoek arreta handia jaso dute azkenaldian biomedikuntzaren esparruan, batez ere diagnosian erabiltzeko helburuarekin. Izan ere, fluoreszentzia, baliabide ezin hobea da gorputzean gertatzen diren hainbat prozesu biokimiko monitorizatzeko eta biomolekulak sentikortasun handiz detektatzeko. Hori dela eta, fotoaktiboak diren kromoforoak markatzaile, zunda edo sentsore fluoreszente gisa erabiltzen dira mikroskopia fluoreszenteari esker; hots, prozesu biokimikoak jarraitzeko, organuluak ikusteko edota biomolekulak detektatzeko. Fluoreszentziarik ez duten kromoforoak, ordea, oxigeno singletea sortzeko gaitasuna ere izan dezakete eta fotosentikortzaile izaerarekin erabil daitezke terapia fotodinamikoan, minbiziaren aurkako tratamenduan. Argi dago, biofotonikako arlo baterako zein besterako eskakizun fotofisikoak guztiz bestelakoak direla eta kromoforo ezberdinak diseinatzea ezinbestekoa dela. Horregatik, lan honetan, BODIPY izeneko kromoforo-familia oinarrizko molekula-egituratzat hartzen da, diagnosian zein terapian aplikatu ahal izateko. Kromoforo mota horren abantaila nagusia da bere egitura eta propietateak erraz molda daitezkeela. Horrela, egituraren gainean ordezkapen sinple batzuk eginda hainbat eskakizun modu errazean ase daitezke. Hortaz, gure helburu nagusia da BODIPYan oinarritutako fluoroforoak zein fotosentikortzaileak garatzea eta diseinu molekularraren garrantzia azpimarratzea

Koloratzaile fotoaktiboen belaunaldi berria

Nature is a source of inspiration for humankind and helps in technological advance. As a matter of fact, the reproduction of the photosynthesis, where natural chromophores absorb the incoming sunlight, is a long seeking challenge. To mimic such antenna systems new organic dyes are designed. However, single molecules show intrinsic limitations to absorb the whole electromagnetic spectrum, for light traveling, and to withstand prolonged irradiation regimes. To offset such shortcoming, multichromophoric dyes are an appealing alternative. In these complex molecular structures dissimilar dyes are covalently linked to promote energy transfer between them, which is the key pathway. Thus, multichromohores enable a broadband and efficient absorption. Therefore, multichromophoric dyes emerge as the next generation of ap-plied photoactive systems for artificial antennae in optic and photovoltaic devices. Herein, we detail the main structural and photophysical requirements to develop efficient and stable multichromophores. As a proof of concept, we showcase multichromophoric dyes based on rhodamine, perylene red and BODIPY and describe their photonic performance applied as lasers and sensors.; Gizakiok, maiz, naturan inspiratzen gara garapen teknologikoa bultzatzeko. Bada, fotosin-tesia horren adibide argia da. Prozesu natural horretan, eguzki-argia kromoforo naturalen bidez xurgatzen da, eta gaur egun antena-sistema natural hori modu eraginkorrean imitatzeko azterlan ugari egiten ari dira, koloratzaile organiko berrien diseinuan oinarrituta. Hala ere, molekula sinpleak direnez, zenbait muga izaten dituzte; adibidez, zailtasunak dituzte espektro elektromagnetiko osoan argia xurgatzeko, argi-energia garraiatzeko eta erradiazio jarraituaren pean luze irauteko. Hala, hainbat kromoforoz osatutako koloratzaileak, multikromoforo deritzenak, irtenbide aproposa dira. Molekula-egitura horietan, kromoforo edo koloratzaile ezberdinak modu kobalentean konbinatzen dira eta energia-trukea sustatzen da. Hortaz, antena naturalak imitatzeko funtsezkoa den prozesua lortzen da eta argiaren xurgapen zabala eta eraginkorra bermatzen da. Hori dela eta, koloratzaileen kimikan, multikromoforoak etorkizuneko sistema fotoaktibotzat hartzen dira antena artifizialak garatzeko eta gailu optiko eta fotovoltaikoetan aplikatzeko. Argitalpen honetan, beraz, antena eraginkor eta egonkorrak garatzeko ezinbestekoak diren irizpide molekularrak eta fotofisikoak zehazten dira. Adibide gisa, errodaminan, perileno gorrian eta BODIPYan oinarritutako koloratzaile multikromoforikoak aurkezten dira, eta horien portaera fotonikoa deskribatzen da laser eta sentsore bezala erabiltzeko

Narcissistic self-sorting of n-acene nano-ribbons yielding energy-transfer and electroluminescence at p-n junctions

The 2,3-didecyloxy derivative of an n-type anthracene (n-BG) and a p-type tetracene (p-R) have been synthesized and their self-assembly into nano-ribbons studied. Hyperspectral fluorescence imaging revealed their narcissistic self-sorting, leading to separated nanoribbons emitting with very different colors (blue or green for n-BG, depending on the growth solvent, and red for p-R). It is unique that the usual origins of self-sorting, such as specific H-bonding, different growth kinetics, or incompatible steric hindrance can be ruled out. Hence, the narcissistic behaviour is herein proposed to originate from a sofar unconsidered cause: the discrepancy between the quadrupolar character of n-BG and dipolar character of p-R. At the p-n junctions of these nanoribbons, inter-ribbon FRET and electro-luminescence switch-on were observed by fluorescence/luminescence microscopy.The authors acknowledge the financial support of the European Research Council Marie Curie Actions (FP7-PEOPLE-2012-ITN SMARTNET Grant agreement Nr 316656); the CNRS; the French Ministry of Education and Research; the Region Aquitaine; the ANR-06-JCJC-0030; the Department of Education, Science and Universities of the Basque Country Government (postdoctoral grant and project IT1639-22); the "Arina" informatic cluster of UPV/EHU; the facilities ELORGA of UB; and the ANR-17-CE24-0033-01 RESOLVE. The authors thank Dr A. Mendez-Ardoy for the CV measurements and CESAMO for structural analyses (ISM, Univ. Bordeaux)