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12 pags., 3 figs., 1 app. -- Open Access funded by Creative Commons Atribution Licence 3.0 ; We predict unprecedentedly large values of the energy-transfer rate between an optical emitter and a layer of periodically doped graphene. The transfer exhibits divergences at photon frequencies corresponding to the Van Hove singularities of the plasmonic band structure of the graphene. In particular, we find flat bands associated with regions of vanishing doping charge, which appear in graphene when it is patterned through gates of spatially alternating signs, giving rise to intense transfer rate singularities. Graphene is thus shown to provide a unique platform for fast control of optical energy transfer via fast electrostatic inhomogeneous doping. © IOP Publishing and Deutsche Physikalische Gesellschaft. ; This work was partially supported by the European Union (FP7-ICT-2009-4-248855-N4E), the Spanish MEC (MAT2010-14885 and Consolider NanoLight.es) and Ibercivis. AM acknowledges financial support from the Spanish FPU.

Ultrafast intramolecular electronic energy transfer in a conjugated donor-acceptor system is simulated using nonadiabatic excited-state molecular dynamics. After initial site-selective photoexcitation of the donor, transition density localization is monitored throughout the S-2 -> S-1 internal conversion process, revealing an efficient unidirectional donor acceptor energy-transfer process. Detailed analysis of the excited state trajectories uncovers several salient features of the energy-transfer dynamics. While a weak temperature dependence is observed during the entire electronic energy relaxation, an ultrafast initially temperature-independent process allows the molecular system to approach the S-2-S-1 potential energy crossing seam within the first ten femtoseconds. Efficient energy transfer occurs in the absence of spectral overlap between the donor and acceptor units and is assisted by a transient delocalization phenomenon of the excited-state wave function acquiring Frenkel-exciton character at the moment of quantum transition. ; This project has received funding from the Universidad Carlos III de Madrid, the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement n° 600371, el Ministerio de Economia y Competitividad (COFUND2014-51509), el Ministerio de Educación, cultura y Deporte (CEI-15-17) and Banco Santander. This work was partially supported by CONICET, UNQ, ANPCyT (PICT-2014-2662). We also acknowledge support of the Center for Integrated Nano-technology (CINT), a U.S. Department of Energy, Office of Basic Energy Sciences user facility, as well as additional funding from the Bavarian University Centre for Latin America (BAYLAT). The work in Mons is supported by BELSPO through the PAI P6/27 Functional Supramolecular Systems project and by the Belgian National Fund for Scientific Research FNRS/F.R.S. DB is a Research Director of FNRS.

Com o objetivo de estudar as propriedades ópticas do polímero TFB, e de sua blenda com o polímero P3HT, foram realizadas medidas de absorção e fotoluminescência (PL) para ambos polímeros, e de uma blenda TFB:P3HT (95:05), depositados sob lâminas de vidro, pela técnica de deposição por centrifugação. Foram utilizados diferentes solventes na preparação das amostras, a fim de comparar os possíveis efeitos dos mesmos na emissão e transferência de energia entre os dois polímeros. Medidas de tempo de decaimento foram realizadas para verificar se esse parâmetro se altera para o TFB preparado a partir de diferentes solventes, e quando na presença de P3HT. Os resultados das medidas de fotoluminescência dos polímeros isolados mostram que não há mudança na forma da emissão desses polímeros conforme se alteram os solventes utilizados no preparo das soluções. Entretanto, no caso da blenda, ocorre mudança na transferência de energia entre os polímeros, dependendo do solvente, deslocando a cor de emissão da amostra para o azul ou vermelho. No espectro de fotoluminescência da blenda é observada uma emissão em 575 nm, a qual não aparece na fotoluminescência das amostras do TFB e P3HT isolados. A partir das medidas de tempo de decaimento, vimos que, nas amostras de TFB, não há alteração considerável com a mudança do solvente. Já para a blenda, nota-se que a presença do P3HT faz com que o tempo de decaimento do TFB diminua, especialmente quando o solvente utilizado foi o clorofórmio.

Molybdenum disulfide nanosheets covalently modified with porphyrin were prepared and fully characterized. Neither the porphyrin absorption nor its fluorescence was notably affected by covalent linkage to MoS2. The use of transient absorption spectroscopy showed that a complex ping‐pong energy‐transfer mechanism, namely from the porphyrin to MoS2 and back to the porphyrin, operated. This study reveals the potential of transition‐metal dichalcogenides in photosensitization processes. ; This project has received funding from EC H2020 under the Marie Sklodowska‐Curie grant agreement No. 642742. HRSTEM and EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. R.A. gratefully acknowledges support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project grant MAT2016‐79776‐P (AEI/FEDER, UE) and from EC H2020 programs "Graphene Flagship" (785219), FLAG‐ERA—"GATES" (JTC‐PCI2018‐093137) and "ESTEEM3" (823717). R.A. also acknowledges Government of Aragon under the project "Construyendo Europa desde Aragon" 2014‐2020 (grant number E13_17R). ; Peer reviewed

Photoluminescence properties and relaxation dynamics of electronic excitations in cesium vanadate CsVO 3 have been studied upon pulse laser excitation in the wide temperature range of 6.5–300 K. A vibronic structure observed in low-temperature PL spectra is considered and interpreted. Peculiarities of luminescence relaxation dynamics and emission spectra of CsVO 3 along with the appearance of the vibronic structure are explained in terms of strong electron-phonon coupling of excited electronic states and centrosymmetric vibrational modes in [VO 4 ] 3- center. A new approach in an interpretation of luminescence processes in vanadates is demonstrated. © 2019 Elsevier Ltd ; 16.5186.2017/8.9 ; The work was supported by Act 211 Government of the Russian Federation , contract № 02.A03.21.0006 . I.A.W. thanks for financial support Minobrnauki initiative research project № 16.5186.2017/8.9 . Authors thank Dr. Mathijs de Jong (Utrecht University) for his kind assistance in laser experiments and Prof. Boris V. Shulgin for fruitful discussions of this work.

This is the peer reviewed version of the following article: Chem. Eur. J. 2019, 25, 7004 7011, which has been published in final form at https://doi.org/10.1002/chem.201900830. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ; [EN] Benzophenone (BP) and drugs containing the BP chromophore, such as the non-steroidal anti-inflammatory drug ketoprofen, have been widely reported as DNA photo-sensitizers through triplet-triplet energy transfer (TTET). In the present work, a direct spectroscopic fingerprint for the formation of the thymine triplet ((3)Thy*) by through-bond (TB) TTET from (BP)-B-3* has been uncovered. This has been achieved in two new systems that have been designed and synthesized with one BP and one thymine (Thy) covalently linked to the two ends of the rigid skeleton of the natural bile acids cholic and lithocholic acid. The results shown here prove that it is possible to achieve triplet energy transfer to a Thy unit even when the photosensitizer is at a long (non-bonding) distance. ; Financial support from the Spanish Government (Grant SEV-2016-0683 and Projects CTQ2012-38754-C03-03 and CTQ2015-70164P), the Generalitat Valenciana (Prometeo Program), and the Universitat Politecnica de Valencia (pre-doctoral FPI fellowship for P.M.) is gratefully acknowledged. ; Miró, P.; Gomez-Mendoza, M.; Sastre Navarro, GI.; Cuquerella Alabort, MC.; Miranda Alonso, MÁ.; Marín García, ML. (2019). Generation of the Thymine Triplet State by Through-Bond Energy Transfer. Chemistry - A European Journal. 25(28):7004-7011. https://doi.org/10.1002/chem.201900830 ; S ; 7004 ; 7011 ; 25 ; 28 ; Mouret, S., Baudouin, C., Charveron, M., Favier, A., Cadet, J., & Douki, T. (2006). Cyclobutane pyrimidine dimers are predominant DNA lesions in whole human skin exposed to UVA radiation. Proceedings of the National Academy of Sciences, 103(37), 13765-13770. doi:10.1073/pnas.0604213103 ; Setlow, R. B., Grist, E., Thompson, K., & Woodhead, A. D. (1993). ...

9 páginas, 8 figuras. ; In this work we report the study of energy transfer between Nd3+ and Yb3+ ions in glasses with the 0.8CaSiO3-0.2Ca3(PO4)2 eutectic composition at room temperature by using steady-state and time-resolved laser spectroscopy. The Nd3+→Yb3+ transfer efficiency obtained from the Nd3+ lifetimes in the single doped and codoped samples reaches 73% for the highest Nd3+ concentration. The donor decay curves obtained under pulsed excitation have been used to establish the multipolar nature of the Nd3+→ Yb3+ transfer process and the energy transfer microparameter. The nonradiative energy transfer is consistent with an electric dipole-dipole interaction mechanism assisted by energy migration among donors. Back transfer from Yb3+ to Nd3+ is also observed. ; This work was supported by the Spanish Government under projects MAT2008-05921, MAT2009-14282-C02-02, and Consolider CSD2007-00013 (SAUUL), and the Basque Country Government (IT-331-07). ; Peer reviewed

The excited-state relaxation within bacteriochlorophyll (BChl) e and a in chlorosomes of Chlorobium phaeobacteroides has been studied by femtosecond transient absorption spectroscopy at room temperature. Singlet-singlet annihilation was observed to strongly influence both the isotropic and anisotropic decays. Pump intensities in the order of 10(11) photons x pulse(-1) x cm(-2) were required to obtain annihilation-free conditions. The most important consequence of applied very low excitation doses is an observation of a subpicosecond process within the BChl e manifold (similar to200-500 fs), manifesting itself as a rise in the red part of the Q(y) absorption band of the BChl e aggregates. The subsequent decay of the kinetics measured in the BChl e region and the corresponding rise in the baseplate BChl a is not single-exponential, and at least two components are necessary to fit the data, corresponding to several BChl e-->BChl a transfer steps. Under annihilation-free conditions, the anisotropic kinetics show a generally slow decay within the BChl e band (10-20 ps) whereas it decays more rapidly in the BChl a region (similar to1 ps). Analysis of the experimental data gives a detailed picture of the overall time evolution of the energy relaxation and energy transfer processes within the chlorosome. The results are interpreted within an exciton model based on the proposed structure. ; This research was supported by the Swedish Natural Science Research Council, the European Union Training and Mobility of Researchers project "Green Bacterial Photosynthesis" (grant FMRX-CT96-0081), and the Kempe Foundation. J. Pšenčik also thanks the Swedish Institute and Grant Agency of the Czech Republic (grant 206/02/0942) for financial support. ; Peer reviewed

he influence of non-covalent σ–π orbital interactions on triplet–triplet energy transfer (TTET) through tuning of the donor excitation energy remains basically unexplored. In the present work, we have investigated intermolecular TTET using donor moieties covalently linked to a rigid cholesterol (Ch) scaffold. For this purpose, diaryl ketones of π,π* electronic configuration tethered to α- or β-Ch were prepared from tiaprofenic acid (TPA) and suprofen (SUP). The obtained systems TPA-α-Ch, TPA-β-Ch, SUP-α-Ch and SUP-β-Ch were submitted to photophysical studies (laser flash photolysis and phosphorescence), in order to delineate the influence of steric shielding and σ–π orbital interactions on the rate of TTET to a series of energy acceptors. As a matter of fact, fine tuning of the donor triplet energy significantly modifies the rate constants of TTET in the absence of diffusion control. The experimental results are rationalized by means of theoretical calculations using first principles methods based on DFT as well as molecular dynamics. ; Financial support from the Generalitat Valenciana (Prometeo Program), the Spanish Government (CTQ2010-19909, SEV-2012-0267 and FPU fellowship for F.P.) and the Carlos III Institute of Health (Grant RIRAAF, RETICS program and Miguel Servet Contract CP11/00154 for I. A.) is gratefully acknowledged. We thank ASIC-UPV for computing time. Dedicated to Prof. Diego Cortes on the occasion of his 60th birthday. ; Andreu Ros, MI.; Morera Bertomeu, IM.; Palumbo, F.; Sastre Navarro, GI.; Bosca Mayans, F.; Miranda Alonso, MÁ. (2015). Steric-shielding vs sigma-pi orbital interactions in triplet-triplet energy transfer. Chemical Science. 6(7):4035-4041. https://doi.org/10.1039/c5sc00823a ; S ; 4035 ; 4041 ; 6 ; 7 ; Baldo, M. A., & Forrest, S. R. (2000). Transient analysis of organic electrophosphorescence: I. Transient analysis of triplet energy transfer. Physical Review B, 62(16), 10958-10966. doi:10.1103/physrevb.62.10958 ; Scaiano, J. C., Leigh, W., Meador, M. A., & Wagner, P. J. ...

We present a comprehensive study of two indocarbocyanines, DiI (1,1′-dioctadecyl-3,3,3′3′-tetramethylindocarbocyanine perchlorate) and DiD (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindodicarbocyanine perchlorate), in water suspensions in the presence of a CTAB surfactant both above and below the critical micellar concentration. The very good affinity of the two dyes with CTAB allows them to be brought into aqueous solutions minimizing aggregation phenomena. When the dyes are loaded inside the micelles, stable fluorescent nanostructures are formed that can be exploited for fundamental studies and for imaging applications. Of special interest are micelles loaded with both dyes: indeed, the large local dye concentration inside the micelles allows observing resonance energy transfer in systems where the global dye concentration is maintained at a low level, so that detailed and robust spectroscopic characterization is possible. Quite impressively, the efficiency of resonance energy transfer is boosted when diluting the sample below the critical micellar concentration. This counterintuitive result is explained in terms of the very large affinity between the dyes and CTAB which favors the dynamical formation of small molecular clusters containing both dyes. Fluorescent micelles are widely used in bioimaging and pharmacokinetic applications. More specifically, the observation of resonant energy transfer in micelles or more generally in nanostructures loaded with two dyes is routinely exploited as a way to assess the nanostructure integrity. In this context, our results demonstrate the importance of robust spectroscopic characterization of the relevant systems in different environments in order to safely assess the viability of the integrity test of nanoparticles based on resonant energy transfer. ; This work is dedicated to Concepció Rovira and Jaume Veciana, inspiring scientists in the field of functional molecular materials. Working with them is a prized privilege and the basis for a solid friendship. AD, MA, FB, CS and AP benefited from the equipment and support of the COMP-HUB Initiative, funded by the "Departments of Excellence" program of the Italian Ministry for Education, University and Research (MIUR, 2018–2022) and acknowledge the support from the high performance computing center at Parma University. JMF, GVN, MK and NV acknowledge support from MINECO through the Severo Ochoa Programme FUNFUTURE (SEV-2015-0496 and CEX2019-000917-S), and the Ministry of Science and Innovation of Spain through the grant PID2019-105622RB-I00 (Mol4Bio), and gratefully acknowledge the financial support received from European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 712949 (TECNIOspring PLUS) and from the Agency for Business Competitiveness of the Government of Catalonia. ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed