1,721,011 research outputs found
Symmetry‐Breaking Charge‐Transfer Chromophore Interactions Supported by Carbon Nanodots
Full text linkCarbon dots (CDs) and their derivatives are useful platforms for studying electron-donor/acceptor interactions and dynamics therein. Herein, we couple amorphous CDs with phthalocyanines (Pcs) that act as electron donors with a large extended p-surface and intense absorption across the visible range of the solar spectrum. Investigations of the intercomponent interactions by means of steady-state and pump-probe transient absorption spectroscopy reveal symmetry-breaking charge transfer/separation and recombination dynamics within pairs of phthalocyanines. The CDs facilitate the electronic interactions between the phthalocyanines. Thus, our findings suggest that CDs could be used to support electronic couplings in multichromophoric systems and further increase their applicability in organic electronics, photonics, and artificial photosynthesisFil: Cacioppo, Michele. Università degli Studi di Trieste; ItaliaFil: Scharl, Tobias. Universitat Erlangen-Nuremberg; AlemaniaFil: Dordevic, Luka. Università degli Studi di Trieste; ItaliaFil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Arcudi, Francesca. Università degli Studi di Trieste; ItaliaFil: Guldi, Dirk. Universitat Erlangen-Nuremberg; AlemaniaFil: Prato, Maurizio. Università degli Studi di Trieste; Itali
Synthesis and excited state processes of arrays containing amine-rich carbon dots and unsymmetrical rylene diimides
Full text linkCombining carbon dots (CDs) with p-extended chromophores is an attractive way to study the electronic and energy processes of the former as a key step to many applications, including photosensing, photocatalysis, or photosensitization. CDs, in conjugation with chromophores, can have value in preparing donor–acceptor hybrids, and can also be used as scaffolds to support electronic communication between dyes. In this work, we conjugate two different rylene diimides, naphthalene and perylene diimides (NDI and PDI, respectively), with amorphous nitrogen-doped carbon dots. We take advantage of the imidization reaction between the amine-rich surface of the carbon dots and the monimide monoanhydride precursors of NDIs and PDIs, under microwave assisted conditions. The resulting (nano)hybrids were characterized also by spectroscopic methods. In particular, time-resolved spectroscopy for the multichromophoric array, consisting of CDs and both rylene diimides, allowed us to elucidate the complex inter-chromophoric interactions taking place in the excited state.Fil: Dordevic, Luka. Università degli Studi di Trieste; ItaliaFil: Haines, Philipp. Universitat Erlangen-Nuremberg; AlemaniaFil: Cacioppo, Michele. Università degli Studi di Trieste; ItaliaFil: Arcudi, Francesca. Università degli Studi di Trieste; ItaliaFil: Scharl, Tobias. Universitat Erlangen-Nuremberg; AlemaniaFil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Guldi, Dirk. Universitat Erlangen-Nuremberg; AlemaniaFil: Prato, Maurizio. Università degli Studi di Trieste; Itali
Four chromophores in one building block: Synthesis, structure and characterization of trans -[Ru(MQ)4Cl2]4+ and trans -[Ru(4,4-bpy)4Cl2] (MQ+ = N-methyl-4,4-bipyridinium, bpy = bipyridine)
Full text linkWe report the synthesis, crystal structure, electrochemical and spectroscopic properties of trans-[Ru(MQ)4Cl2]4+ (14+), where MQ+ = N-methyl-4,4′-bipyridinium. The crystal structure of 14+ shows the pyridinic rings bound in a trans fashion to the Ru ion. In 14+ and in its analog trans-[Ru(4,4′-bpy)4Cl2] (2, bpy = bipyridine), the electrochemical reduction waves of the four iminic ligands occur at very closely spaced potentials. In comparison with previously reported analogues, 14+ and 2 present high molar extinction coefficients (ε = 20,000-50,000 M-1cm-1), and red-shifted absorptions (up to 800 nm for 14+ and up to 600 nm for 2) in acetonitrile. Upon protonation of the four exposed nitrogens of 2 and electrochemical reduction of the ligands in 14+ and 2, spectral changes occur with retention of isosbestic points, revealing the presence of four independent chromophores. These results suggest poor electronic communication between the aromatic ligands within each compound, in contrast to related complexes such as cis-[Ru(2,2′-bpy)2Cl2] (3).Fil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Hodak, Jose Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentin
Harnessing high-energy MLCT excited states for artificial photosynthesis
No full textImportant fractions of the energy absorbed in natural and artificial photosynthetic schemes are dissipated via fast internal conversion processes. In contrast, chromophores that undergo internal conversion on slow timescales allow high-energy excited states to engage in bimolecular or long-range reactivity, outcompeting dissipation. This provides opportunities to improve solar energy conversion efficiencies. This review focuses on MLCT chromophores and analyzes fast and slow internal conversion processes in the form of inter-ligand electron transfer and hole reconfiguration. It discusses the current scenario, the obstacles, and the progress required to establish anti-dissipative molecular energy conversion schemes.Fil: Cotic, Agustina Ludmila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Ramirez Wierzbicki, Ivana Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Assessing the Photoinduced Electron-Donating Behavior of Carbon Nanodots in Nanoconjugates
No full textCarbon nanodots (CNDs) undergo electron transfer in different scenarios. Previous studies have mainly focused on the electron-accepting features of CNDs in covalently linked donor-acceptor nanoconjugates. In view of this, we decided to carry out in this study the formation of covalently linked nanoconjugates that feature electron-donating pressure synthesized carbon nanodots (pCNDs) and electron-accepting 11,11,12,12-tetracyano-9,10-anthra-p-quinodimethane (TCAQ): pCND-TCAQ. The stability of the one-electron reduced form of TCAQ renders it the acceptor of choice. Detailed structural and electrochemical investigations allowed the characterization of pCND-TCAQ. Furthermore, investigations regarding intramolecular interactions, by means of steady-state and pump-probe transient absorption spectroscopies, allowed detection and characterization of three excited state species, in general, and the pCND•+-TCAQ•- charge-separated state, in particular.Fil: Ferrer Ruíz, Andrés. Universidad Complutense de Madrid; EspañaFil: Scharl, Tobias. Universitat Erlangen-Nuremberg; AlemaniaFil: Rodríguez Pérez, Laura. Universidad Complutense de Madrid; EspañaFil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universitat Erlangen-Nuremberg; AlemaniaFil: Herranz, M. Ángeles. Universidad Complutense de Madrid; EspañaFil: Martín, Nazario. Universidad Complutense de Madrid; EspañaFil: Guldi, Dirk. Universitat Erlangen-Nuremberg; Alemani
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Efficient energy transfer via the cyanide bridge in dinuclear complexes containing Ru(ii) polypyridine moieties
Full text linkWe report the synthesis, structure and properties of the cyanide-bridged dinuclear complex ions [Ru(L)-(bpy)(μ-NC)M(CN)5]2−/− (L = tpy, 2,2′;6′,2′′-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2′- bipyridine, M = Fe(II), Fe(III), Cr(III)) and the related monomers [Ru(L)(bpy)X]2+ (X = CN− and NCS−).All the monomeric compounds are weak MLCT emitters (λ = 650?715 nm, ϕ ≈ 10−4). In the Fe(II) and Cr(III) dinuclear systems, the cyanide bridge promotes efficient energy transfer between the Ru-centered MLCT state and a Fe(II)- or Cr(III)-centered d?d state, which results either in a complete quenching of luminescence or in a narrow red emission (λ ≈ 820 nm, ϕ ≈ 10−3) respectively. In the case of Fe(III) dinuclear systems, an electron transfer quenching process is also likely to occur.Fil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Alborés, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Yamazaki, Shiori. University of Florida; Estados UnidosFil: Kleiman, Valeria D.. University of Florida; Estados UnidosFil: Baraldo Victorica, Luis Mario. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin
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