Hazardous chemical elements in cleaning cloths: A potential source of microfibres.

Although potentially hazardous chemical elements (e.g., Cu, Cr, Pb, Sb, Ti, Zn) have been studied in clothing textiles, their presence in cleaning textiles is unknown. In this study, 48 cleaning cloth products (consisting of 81 individual samples) purchased in Europe, and consisting of synthetic (petroleum-based), semi-synthetic or natural fibres or combinations of these different types, have been analysed for 16 chemical elements by X-ray fluorescence (XRF) spectrometry. Titanium was detected in most cases (median and maximum concentrations ~3700 and 12,400 mg kg-1, respectively) and Raman microspectroscopy revealed that TiO2 was present as anatase. Barium, Br, Cr, Cu, Fe and Zn were frequently detected over a range of concentrations, reflecting the presence of various additives, and Sb was present at concentrations up to about 200 mg kg-1 in samples containing polyester as catalytic residue from the polymerisation process. Lead was detected as a contaminant in four samples and at concentrations below 10 mg kg-1. Overall, the range of the chemical element profiles and concentrations was similar to those for clothing materials published in the literature, suggesting that broadly the same additives, materials and processes are employed to manufacture cloths and clothing textiles. The mechanisms by which potentially hazardous chemical elements are released into the environment with microfibres or mobilised into soluble or nano-particulate forms remain to be explored

Electronic excited states of guanine-cytosine hairpins and duplexes studied by fluorescence spectroscopy

[EN] Guanine-cytosine hairpins, containing a hexaethylene glycol bridge, are studied by steady-state fluorescence spectroscopy and time-correlated single photon counting; their properties are compared to those of duplexes with the same sequence. It is shown that, both in hairpins and in duplexes, base pairing induces quenching of the pi pi(star) fluorescence, the quantum yield decreasing by at least two orders of magnitude. When the size of the systems increases from two to ten base pairs, a fluorescent component decaying on the nanosecond time-scale appears at energy higher than that stemming from the bright states of non-interacting mono-nucleotides (ca. 330 nm). For ten base pairs, this new fluorescence forms a well-defined band peaking at 305 nm. Its intensity is about 20% higher for the hairpin compared to the duplex. Its position (red-shifted by 1600 cm(-1)) and width (broader by 1800 cm(-1) FWHM) differ from those observed for large duplexes containing 1000 base pairs, suggesting the involvement of electronic coupling. Fluorescence anisotropy reveals that the excited states responsible for high energy emission are not populated directly upon photon absorption but are reached during a relaxation process. They are assigned to charge transfer states. According to the emerging picture, the amplitude of conformational motions determines whether instantaneous deactivation to the ground state or emission from charge transfer states will take place, while pi pi(star) fluorescence is associated to imperfect base-pairing.The French Agency for Research (ANR-10-BLAN-0809-01), the Conselleria de Educacion-Generalitat Valenciana (VALi+D program to I.V., N° 2010033) and the US Department of Energy, Office of Basic Energy Sciences (grant no. DE-FG02-96ER14604 to F.D.L.) are acknowledged for financial support.Brazard, J.; Thazhathveetil, A.; Vayá Pérez, I.; Lewis, F.; Gustavsson, T.; Markovitsi, D. (2013). Electronic excited states of guanine-cytosine hairpins and duplexes studied by fluorescence spectroscopy. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 12(8):1453-1459. https://doi.org/10.1039/c3pp50088hS14531459128Bouvier, B., Dognon, J.-P., Lavery, R., Markovitsi, D., Millié, P., Onidas, D., & Zakrzewska, K. (2003). Influence of Conformational Dynamics on the Exciton States of DNA Oligomers. The Journal of Physical Chemistry B, 107(48), 13512-13522. doi:10.1021/jp036164uMezzina, E., Mariani, P., Itri, R., Masiero, S., Pieraccini, S., Spada, G. P., … Gottarelli, G. (2001). The Self-Assembly of a Lipophilic Guanosine Nucleoside into Polymeric Columnar Aggregates: The Nucleoside Structure Contains Sufficient Information To Drive the Process towards a Strikingly Regular Polymer. Chemistry, 7(2), 388-395. doi:10.1002/1521-3765(20010119)7:23.0.co;2-vMarkovitsi, D., Gustavsson, T., & Talbot, F. (2007). Excited states and energy transfer among DNA bases in double helices. Photochemical & Photobiological Sciences, 6(7), 717. doi:10.1039/b705674eVayá, I., Gustavsson, T., Douki, T., Berlin, Y., & Markovitsi, D. (2012). Electronic Excitation Energy Transfer between Nucleobases of Natural DNA. Journal of the American Chemical Society, 134(28), 11366-11368. doi:10.1021/ja304328gKohler, B. (2010). Nonradiative Decay Mechanisms in DNA Model Systems. The Journal of Physical Chemistry Letters, 1(13), 2047-2053. doi:10.1021/jz100491xMarkovitsi, D., Gustavsson, T., & Vayá, I. (2010). Fluorescence of DNA Duplexes: From Model Helices to Natural DNA. The Journal of Physical Chemistry Letters, 1(22), 3271-3276. doi:10.1021/jz101122tMarkovitsi, D., Onidas, D., Talbot, F., Marguet, S., Gustavsson, T., & Lazzarotto, E. (2006). UVB/UVC induced processes in model DNA helices studied by time-resolved spectroscopy: Pitfalls and tricks. Journal of Photochemistry and Photobiology A: Chemistry, 183(1-2), 1-8. doi:10.1016/j.jphotochem.2006.05.029Vayá, I., Miannay, F.-A., Gustavsson, T., & Markovitsi, D. (2010). High-Energy Long-Lived Excited States in DNA Double Strands. ChemPhysChem, 11(5), 987-989. doi:10.1002/cphc.201000027Miannay, F.-A., Bányász, Á., Gustavsson, T., & Markovitsi, D. (2007). Ultrafast Excited-State Deactivation and Energy Transfer in Guanine−Cytosine DNA Double Helices. Journal of the American Chemical Society, 129(47), 14574-14575. doi:10.1021/ja077100q(s. f.). doi:10.1021/ja073448Sobolewski, A. L., Domcke, W., & Hattig, C. (2005). Tautomeric selectivity of the excited-state lifetime of guanine/cytosine base pairs: The role of electron-driven proton-transfer processes. Proceedings of the National Academy of Sciences, 102(50), 17903-17906. doi:10.1073/pnas.0504087102Abo-Riziq, A., Grace, L., Nir, E., Kabelac, M., Hobza, P., & de Vries, M. S. (2004). Photochemical selectivity in guanine-cytosine base-pair structures. Proceedings of the National Academy of Sciences, 102(1), 20-23. doi:10.1073/pnas.0408574102Altmann, S., Labhardt, A. M., Bur, D., Lehmann, C., Bannwarth, W., Billeter, M., … Leupin, W. (1995). NMR studies of DNA duplexes singly cross-linked by different synthetic linkers. Nucleic Acids Research, 23(23), 4827-4835. doi:10.1093/nar/23.23.4827Kozerski, L. (2001). A nicked duplex decamer DNA with a PEG6 tether. Nucleic Acids Research, 29(5), 1132-1143. doi:10.1093/nar/29.5.1132Rumney, S., & Kool, E. T. (1995). Structural Optimization of Non-Nucleotide Loop Replacements for Duplex and Triplex DNAs. Journal of the American Chemical Society, 117(21), 5635-5646. doi:10.1021/ja00126a004Hariharan, M., Siegmund, K., & Lewis, F. D. (2010). Structure and Stability of Alkane-Linked DNA Hairpin Conjugates. The Journal of Organic Chemistry, 75(18), 6236-6243. doi:10.1021/jo1013299Lewis, F. D., Letsinger, R. L., & Wasielewski, M. R. (2001). Dynamics of Photoinduced Charge Transfer and Hole Transport in Synthetic DNA Hairpins. Accounts of Chemical Research, 34(2), 159-170. doi:10.1021/ar0000197McCullagh, M., Hariharan, M., Lewis, F. D., Markovitsi, D., Douki, T., & Schatz, G. C. (2010). Conformational Control of TT Dimerization in DNA Conjugates. A Molecular Dynamics Study. The Journal of Physical Chemistry B, 114(15), 5215-5221. doi:10.1021/jp100983tMcCullagh, M., Zhang, L., Karaba, A. H., Zhu, H., Schatz, G. C., & Lewis, F. D. (2008). Effect of Loop Distortion on the Stability and Structural Dynamics of DNA Hairpin and Dumbbell Conjugates. The Journal of Physical Chemistry B, 112(36), 11415-11421. doi:10.1021/jp802378aOnidas, D., Markovitsi, D., Marguet, S., Sharonov, A., & Gustavsson, T. (2002). Fluorescence Properties of DNA Nucleosides and Nucleotides:  A Refined Steady-State and Femtosecond Investigation. The Journal of Physical Chemistry B, 106(43), 11367-11374. doi:10.1021/jp026063gRiazance, J. H., Baase, W. A., Johnson, W. C., Hall, K., Cruz, P., & Tinoco, I. (1985). Evidence for Z-form RNA by vacuum UV circular dichroism. Nucleic Acids Research, 13(13), 4983-4989. doi:10.1093/nar/13.13.4983Tuma, J., Tonzani, S., Schatz, G. C., Karaba, A. H., & Lewis, F. D. (2007). Structure and Electronic Spectra of DNA Mini-hairpins with Gn:CnStems. The Journal of Physical Chemistry B, 111(45), 13101-13106. doi:10.1021/jp072303mGeorghiou, S., Kubala, S. M., & Large, C. C. (1998). Environmental Control of the Deformability of the DNA Double Helix. Photochemistry and Photobiology, 67(5), 526-531. doi:10.1111/j.1751-1097.1998.tb09088.xZuo, X., Cui, G., Merz, K. M., Zhang, L., Lewis, F. D., & Tiede, D. M. (2006). X-ray diffraction «fingerprinting» of DNA structure in solution for quantitative evaluation of molecular dynamics simulation. Proceedings of the National Academy of Sciences, 103(10), 3534-3539. doi:10.1073/pnas.0600022103Marguet, S., Markovitsi, D., Millié, P., Sigal, H., & Kumar, S. (1998). Influence of Disorder on Electronic Excited States:  An Experimental and Numerical Study of Alkylthiotriphenylene Columnar Phases. The Journal of Physical Chemistry B, 102(24), 4697-4710. doi:10.1021/jp980623nAlbrecht, A. C. (1961). Polarizations and assignments of transitions: The method of photoselection. Journal of Molecular Spectroscopy, 6, 84-108. doi:10.1016/0022-2852(61)90234-xHua, Y., Changenet-Barret, P., Gustavsson, T., & Markovitsi, D. (2013). The effect of size on the optical properties of guanine nanostructures: a femtosecond to nanosecond study. Physical Chemistry Chemical Physics, 15(19), 7396. doi:10.1039/c3cp00060eMariani, P., & Saturni, L. (1996). Measurement of intercolumnar forces between parallel guanosine four-stranded helices. Biophysical Journal, 70(6), 2867-2874. doi:10.1016/s0006-3495(96)79856-9Gustavsson, T., Improta, R., & Markovitsi, D. (2010). DNA/RNA: Building Blocks of Life Under UV Irradiation. The Journal of Physical Chemistry Letters, 1(13), 2025-2030. doi:10.1021/jz1004973Hare, P. M., Crespo-Hernandez, C. E., & Kohler, B. (2006). Internal conversion to the electronic ground state occurs via two distinct pathways for pyrimidine bases in aqueous solution. Proceedings of the National Academy of Sciences, 104(2), 435-440. doi:10.1073/pnas.0608055104Scholes, G. D., & Ghiggino, K. P. (1994). Electronic Interactions and Interchromophore Excitation Transfer. The Journal of Physical Chemistry, 98(17), 4580-4590. doi:10.1021/j100068a017Nachtigallová, D., Hobza, P., & Ritze, H.-H. (2008). Electronic splitting in the excited states of DNA base homodimers and -trimers: an evaluation of short-range and Coulombic interactions. Physical Chemistry Chemical Physics, 10(37), 5689. doi:10.1039/b806323kStarikov, E. B., Cuniberti, G., & Tanaka, S. (2009). Conformation Dependence of DNA Exciton Parentage. The Journal of Physical Chemistry B, 113(30), 10428-10435. doi:10.1021/jp9035869Plasser, F., Aquino, A. J. A., Hase, W. L., & Lischka, H. (2012). UV Absorption Spectrum of Alternating DNA Duplexes. Analysis of Excitonic and Charge Transfer Interactions. The Journal of Physical Chemistry A, 116(46), 11151-11160. doi:10.1021/jp304725rSauri, V., Gobbo, J. P., Serrano-Pérez, J. J., Lundberg, M., Coto, P. B., Serrano-Andrés, L., … Roca-Sanjuán, D. (2012). Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism. Journal of Chemical Theory and Computation, 9(1), 481-496. doi:10.1021/ct3006166Groenhof, G., Schäfer, L. V., Boggio-Pasqua, M., Goette, M., Grubmüller, H., & Robb, M. A. (2007). Ultrafast Deactivation of an Excited Cytosine−Guanine Base Pair in DNA. Journal of the American Chemical Society, 129(21), 6812-6819. doi:10.1021/ja069176cGiudice, E. (2003). Base pair opening within B-DNA: free energy pathways for GC and AT pairs from umbrella sampling simulations. Nucleic Acids Research, 31(5), 1434-1443. doi:10.1093/nar/gkg239Folta-Stogniew, E., & Russu, I. M. (1994). Sequence Dependence of Base-Pair Opening in a DNA Dodecamer Containing the CACA/GTGT Sequence Motif. Biochemistry, 33(36), 11016-11024. doi:10.1021/bi00202a022Schwalb, N. K., & Temps, F. (2008). Base Sequence and Higher-Order Structure Induce the Complex Excited-State Dynamics in DNA. Science, 322(5899), 243-245. doi:10.1126/science.1161651Vayá, I., Brazard, J., Gustavsson, T., & Markovitsi, D. (2012). Electronically excited states of DNA oligonucleotides with disordered base sequences studied by fluorescence spectroscopy. Photochemical & Photobiological Sciences, 11(11), 1767. doi:10.1039/c2pp25180aPan, Z., Hariharan, M., Arkin, J. D., Jalilov, A. S., McCullagh, M., Schatz, G. C., & Lewis, F. D. (2011). Electron Donor–Acceptor Interactions with Flanking Purines Influence the Efficiency of Thymine Photodimerization. Journal of the American Chemical Society, 133(51), 20793-20798. doi:10.1021/ja205460fŠpačková, N., Berger, I., & Šponer, J. (1999). Nanosecond Molecular Dynamics Simulations of Parallel and Antiparallel Guanine Quadruplex DNA Molecules. Journal of the American Chemical Society, 121(23), 5519-5534. doi:10.1021/ja984449sMünzel, M., Szeibert, C., Glas, A. F., Globisch, D., & Carell, T. (2011). Discovery and Synthesis of New UV-Induced Intrastrand C(4−8)G and G(8−4)C Photolesions. Journal of the American Chemical Society, 133(14), 5186-5189. doi:10.1021/ja111304

Coherent ultrafast lattice-directed reaction dynamics of triiodide anion photodissociation

Solid-state reactions are influenced by the spatial arrangement of the reactants and the electrostatic environment of the lattice, which may enable lattice-directed chemical dynamics. Unlike the caging imposed by an inert matrix, an active lattice participates in the reaction, however, little evidence of such lattice participation has been gathered on ultrafast timescales due to the irreversibility of solid-state chemical systems. Here, by lowering the temperature to 80 K, we have been able to study the dissociative photochemistry of the triiodide anion (I₃−) in single-crystal tetra-n-butylammonium triiodide using broadband transient absorption spectroscopy. We identified the coherently formed tetraiodide radical anion (I₄•−) as a reaction intermediate. Its delayed appearance after that of the primary photoproduct, diiodide radical I₂•−, indicates that I₄•− was formed via a secondary reaction between a dissociated iodine radical (I^•) and an adjacent I₃−. This chemistry occurs as a result of the intermolecular interaction determined by the crystalline arrangement and is in stark contrast with previous solution studies

Electronically excited states of DNA oligonucleotides with disordered base sequences studied by fluorescence spectroscopy

[EN] DNA double-stranded oligomers are studied by steady-state and time-resolved fluorescence spectroscopy from the femtosecond to the nanosecond time-scale, following excitation at 267 nm. It is shown that emission arises from three types of excited states. (i) Bright pi pi* states emitting around 330 nm and decaying on the sub-picosecond time-scale with an average lifetime of ca. 0.4 ps and a quantum yield lower than 4 x 10(-6). (ii) Excimers/exciplexes emitting around 430 nm and decaying on the sub-nanosecond time-scale. (iii) Excited states emitting mainly at short wavelengths (lambda < 330 nm) and decaying on the nanosecond time-scale, possibly correlated to GC pairs. The properties of the examined duplexes, exhibiting significant disorder with respect to the nearest neighbour base sequence, are radically different than those of the much longer and disordered calf thymus DNA. Such behaviour suggests that long range and/or sequence effects play a key role in the fate of excitation energy.The French Agency for Research (ANR-10-BLAN-0809-01) and the Conselleria de Educacion-Generalitat Valenciana (VALi+D program to I.V., no. 2010033) are acknowledged for financial support.Vayá Pérez, I.; Brazard, J.; Gustavsson, T.; Markovitsi, D. (2012). Electronically excited states of DNA oligonucleotides with disordered base sequences studied by fluorescence spectroscopy. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 11(11):1767-1773. doi:10.1039/c2pp25180aS17671773111

Stabilization of Mixed Frenkel-Charge Transfer Excitons Extended Across Both Strands of Guanine–Cytosine DNA Duplexes

International audienceThe photoreactive pathways that may lead to DNA damage depend crucially upon the nature of the excited electronic states. The study of alternating guanine–cytosine duplexes by fluorescence spectroscopy and quantum mechanical calculations identifies a novel type of excited states that can be populated following UVB excitation. These states, denoted High-energy Emitting Long-lived Mixed (HELM) states, extend across both strands and arise from mixing between cytosine Frenkel excitons and guanine-to-cytosine charge transfer states. They emit at energies higher than ππ* states localized on single bases, survive for several nanoseconds, are sensitive to the ionic strength of the solution, and are strongly affected by the structural transition from the B form to the Z form. Their impact on the formation of lesions of the genetic code needs to be assessed

The effect of solvent relaxation in the ultrafast time-resolved spectroscopy of solvated benzophenone

Benzophenone (BP) despite its relatively simple molecular structure is a paradigmatic sensitizer, featuring both photocatalytic and photobiological effects due to its rather complex photophysical properties. In this contribution we report an original theoretical approach to model realistic, ultra-fast spectroscopy data, which requires describing intra- and intermolecular energy and structural relaxation. In particular we explicitly simulate time-resolved pump-probe spectra using a combination of state-of-the art hybrid quantum mechanics/molecular mechanics dynamics to treat relaxation and vibrational effects. The comparison with experimental transient absorption data demonstrates the efficiency and accuracy of our approach. Furthermore the explicit inclusion of the solvent, water for simulation and methanol for experiment, allows us, despite the inherent different behavior of the two, to underline the role played by the H-bonding relaxation in the first hundreds of femtoseconds after optical excitation. Finally we predict for the first time the two-dimensional electronic spectrum (2DES) of BP taking into account the vibrational effects and hence modelling partially symmetric and asymmetric ultrafast broadening

Mimicking Conjugated Polymer Thin-Film Photophysics with a Well-Defined Triblock Copolymer in Solution

Conjugated polymers (CPs) are promising materials for use in electronic applications, such as low-cost, easily processed organic photovoltaic (OPV) devices. Improving OPV efficiencies is hindered by a lack of a fundamental understanding of the photophysics in CP-based thin films that is complicated by their heterogeneous nanoscale morphologies. Here, we report on a poly(3-hexylthiophene)-block-poly(tert-butyl acrylate)-block-poly(3-hexylthiophene) rod-coil-rod triblock copolymer. In good solvents, this polymer resembles solutions of P3HT; however, upon the addition of a poor solvent, the two P3HT chains within the triblock copolymer collapse, affording a material with electronic spectra identical to those of a thin film of P3HT. Using this new system as a model for thin films of P3HT, we can attribute the low fluorescence quantum yield of films to the presence of a charge-transfer state, providing fundamental insights into the condensed phase photophysics that will help to guide the development of the next generation of materials for OPVs

Resolving the singlet excited states manifold of benzophenone by first-principles simulations and ultrafast spectroscopy

Accurate characterization of the high-lying excited state manifolds of organic molecules is of fundamental importance for the interpretation of the rich response detected in time-resolved nonlinear electronic spectroscopies. Here, we have characterized the singlet excited states manifold of benzophenone (BP), a versatile organic photoinitiator and a well-known DNA photosensitizer. Benchmarks of various multiconfigurational/multireference (RASSCF/PT2) and time-dependent density functional theory (TD-DFT) approaches allowed assignments of experimental linear absorption signals of BP in the ultraviolet (UV) region, with unprecedented characterization of ground state absorptions in the far UV. Experimental transient absorption spectra obtained by UV-Vis pump-probe spectroscopy at very short time-delays are shown to be directly comparable to theoretical estimates of excited state absorptions (from the low-lying nOπ* and ππ* singlet states) in the Franck-Condon region. Multireference computations provided reliable interpretation of the PP spectra, with TD-DFT results yielding a fair agreement as long as electronic transitions featuring double excitations contributions are not involved. These results lay the groundwork for further computational studies and interpretation of experimental nonlinear electronic spectra of benzophenone in more complex systems, such as BP/DNA adducts