TY - JOUR A1 - Yan, Runyu A1 - Oschatz, Martin A1 - Wu, Feixiang T1 - Towards stable lithium-sulfur battery cathodes by combining physical and chemical confinement of polysulfides in core-shell structured nitrogen-doped carbons JF - Carbon N2 - Despite intensive research on porous carbon materials as hosts for sulfur in lithium-sulfur battery cathodes, it remains a problem to restrain the soluble lithium polysulfide intermediates for a long-term cycling stability without the use of metallic or metal-containing species. Here, we report the synthesis of nitrogen-doped carbon materials with hierarchical pore architecture and a core-shell-type particle design including an ordered mesoporous carbon core and a polar microporous carbon shell. The initial discharge capacity with a sulfur loading up to 72 wt% reaches over 900 mA h g(sulf)(ur)(-1) at a rate of C/2. Cycling performance measured at C/2 indicates similar to 90% capacity retention over 250 cycles. In comparison to other carbon hosts, this architecture not only provides sufficient space for a high sulfur loading induced by the high-pore-volume particle core, but also enables a dual effect of physical and chemical confinement of the polysulfides to stabilize the cycle life by adsorbing the soluble intermediates in the polar microporous shell. This work elucidates a design principle for carbonaceous hosts that is capable to provide simultaneous physical-chemical confinement. This is necessary to overcome the shuttle effect towards stable lithium-sulfur battery cathodes, in the absence of additional membranes or inactive metal-based anchoring materials. KW - lithium-sulfur battery KW - sulfur KW - porous carbon KW - cathode KW - polysulfides Y1 - 2020 U6 - https://doi.org/10.1016/j.carbon.2020.01.046 SN - 0008-6223 SN - 1873-3891 VL - 161 SP - 162 EP - 168 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Wessig, Pablo A1 - John, Leonard A1 - Sperlich, Eric A1 - Kelling, Alexandra T1 - Sulfur tuning of [1,3]-dioxolo[4.5-f]benzodioxole (DBD) fluorescent dyes JF - European journal of organic chemistry N2 - The replacement of oxygen by sulfur atoms of [1,3]-dioxolo[4.5-f]benzodioxole (DBD) fluorescent dyes is an efficient way to adjust the photophysical properties (sulfur tuning). While previously developed S-4-DBD dyes exhibit considerably red-shifted absorption and emission wavelength, the heavy atom effect of four sulfur atoms cause low fluorescence quantum yields and short fluorescence lifetimes. Herein, we demonstrate that the replacement of less than four sulfur atoms (S-1-DBD, 1,2-S-2-DBD, and 1,4-S-2-DBD dyes) permits a fine-tuning of the photophysical properties. In some cases, a similar influence on the wavelength without the detrimental effect on the quantum yields and lifetimes is observed. Furthermore, the synthetic accessibility of S-1- and S-2-DBD dyes is improved, compared with S-4-DBD dyes. For coupling with biomolecules a series of reactive derivatives of the new dyes were developed (azides, OSu esters, alkynes, maleimides). KW - fluorescent dyes KW - heterocycles KW - photophysics KW - stokes shift KW - sulfur Y1 - 2020 U6 - https://doi.org/10.1002/ejoc.202001418 SN - 1434-193X SN - 1099-0690 VL - 2021 IS - 3 SP - 499 EP - 511 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wessig, Pablo A1 - Freyse, Daniel A1 - Schuster, David A1 - Kelling, Alexandra T1 - Fluorescent dyes with large stokes shifts based on Benzo[1,2-d:4,5-d']bis([1,3]dithiole) (“S4-DBD Dyes”) JF - Europan journal of organic chemistry N2 - We report on a further development of [1,3]-dioxolo[4.5-f]benzodioxole (DBD) fluorescent dyes by replacement of the four oxygen atoms of the heterocyclic core by sulfur atoms. This variation causes striking changes of the photophysical properties. Whereas absorption and emission significantly shifted to longer wavelength, the fluorescence lifetimes and quantum yields are diminished compared to DBD dyes. The latter effect is presumably caused by an enhanced intersystem crossing to the triplet state due to the sulfur atoms. The very large Stokes shifts of the S-4-DBD dyes ranging from 3000 cm(-1) to 7400 cm(-1) (67 nm to 191 nm) should be especially emphasized. By analogy with DBD dyes a broad variation of absorption and emission wavelength is possible by introducing different electron withdrawing substituents. Moreover, some derivatives for coupling with biomolecules were developed. KW - fluorescent dyes KW - sulfur KW - heterocycles KW - stokes shift KW - photophysics Y1 - 2020 U6 - https://doi.org/10.1002/ejoc.202000093 SN - 1434-193X SN - 1099-0690 VL - 2020 IS - 11 SP - 1732 EP - 1744 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Wang, Qiong A1 - Mosconi, Edoardo A1 - Wolff, Christian Michael A1 - Li, Junming A1 - Neher, Dieter A1 - De Angelis, Filippo A1 - Suranna, Gian Paolo A1 - Grisorio, Roberto A1 - Abate, Antonio T1 - Rationalizing the molecular design of hole-selective contacts to improve charge extraction in Perovskite solar cells JF - dvanced energy materials N2 - Two new hole selective materials (HSMs) based on dangling methylsulfanyl groups connected to the C-9 position of the fluorene core are synthesized and applied in perovskite solar cells. Being structurally similar to a half of Spiro-OMeTAD molecule, these HSMs (referred as FS and DFS) share similar redox potentials but are endowed with slightly higher hole mobility, due to the planarity and large extension of their structure. Competitive power conversion efficiency (up to 18.6%) is achieved by using the new HSMs in suitable perovskite solar cells. Time-resolved photoluminescence decay measurements and electrochemical impedance spectroscopy show more efficient charge extraction at the HSM/perovskite interface with respect to Spiro-OMeTAD, which is reflected in higher photocurrents exhibited by DFS/FS-integrated perovskite solar cells. Density functional theory simulations reveal that the interactions of methylammonium with methylsulfanyl groups in DFS/FS strengthen their electrostatic attraction with the perovskite surface, providing an additional path for hole extraction compared to the sole presence of methoxy groups in Spiro-OMeTAD. Importantly, the low-cost synthesis of FS makes it significantly attractive for the future commercialization of perovskite solar cells. KW - hole extraction KW - hole selective materials KW - perovskite solar cells KW - sulfur KW - triple-cation perovskite Y1 - 2019 U6 - https://doi.org/10.1002/aenm.201900990 SN - 1614-6832 SN - 1614-6840 VL - 9 IS - 28 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mendel, Ralf R. A1 - Hercher, Thomas W. A1 - Zupok, Arkadiusz A1 - Hasnat, Muhammad Abrar A1 - Leimkühler, Silke T1 - The requirement of inorganic Fe-S clusters for the biosynthesis of the organometallic molybdenum cofactor JF - Inorganics : open access journal N2 - Iron-sulfur (Fe-S) clusters are essential protein cofactors. In enzymes, they are present either in the rhombic [2Fe-2S] or the cubic [4Fe-4S] form, where they are involved in catalysis and electron transfer and in the biosynthesis of metal-containing prosthetic groups like the molybdenum cofactor (Moco). Here, we give an overview of the assembly of Fe-S clusters in bacteria and humans and present their connection to the Moco biosynthesis pathway. In all organisms, Fe-S cluster assembly starts with the abstraction of sulfur froml-cysteine and its transfer to a scaffold protein. After formation, Fe-S clusters are transferred to carrier proteins that insert them into recipient apo-proteins. In eukaryotes like humans and plants, Fe-S cluster assembly takes place both in mitochondria and in the cytosol. Both Moco biosynthesis and Fe-S cluster assembly are highly conserved among all kingdoms of life. Moco is a tricyclic pterin compound with molybdenum coordinated through its unique dithiolene group. Moco biosynthesis begins in the mitochondria in a Fe-S cluster dependent step involving radical/S-adenosylmethionine (SAM) chemistry. An intermediate is transferred to the cytosol where the dithiolene group is formed, to which molybdenum is finally added. Further connections between Fe-S cluster assembly and Moco biosynthesis are discussed in detail. KW - Moco biosynthesis KW - Fe-S cluster assembly KW - l-cysteine desulfurase KW - ISC KW - SUF KW - NIF KW - iron KW - molybdenum KW - sulfur Y1 - 2020 U6 - https://doi.org/10.3390/inorganics8070043 SN - 2304-6740 VL - 8 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Lever, Fabiano A1 - Mayer, Dennis A1 - Metje, Jan A1 - Alisauskas, Skirmantas A1 - Calegari, Francesca A1 - Düsterer, Stefan A1 - Feifel, Raimund A1 - Niebuhr, Mario A1 - Manschwetus, Bastian A1 - Kuhlmann, Marion A1 - Mazza, Tommaso A1 - Robinson, Matthew Scott A1 - Squibb, Richard J. A1 - Trabattoni, Andrea A1 - Wallner, Måns A1 - Wolf, Thomas J. A. A1 - Gühr, Markus T1 - Core-level spectroscopy of 2-thiouracil at the sulfur L1 and L2,3 edges utilizing a SASE free-electron-laser JF - Molecules N2 - In this paper, we report X-ray absorption and core-level electron spectra of the nucleobase derivative 2-thiouracil at the sulfur L1- and L2,3-edges. We used soft X-rays from the free-electron laser FLASH2 for the excitation of isolated molecules and dispersed the outgoing electrons with a magnetic bottle spectrometer. We identified photoelectrons from the 2p core orbital, accompanied by an electron correlation satellite, as well as resonant and non-resonant Coster–Kronig and Auger–Meitner emission at the L1- and L2,3-edges, respectively. We used the electron yield to construct X-ray absorption spectra at the two edges. The experimental data obtained are put in the context of the literature currently available on sulfur core-level and 2-thiouracil spectroscopy. KW - X-ray KW - photoelectron KW - sulfur KW - thiouracil KW - nucleobases KW - Coster–Kronig KW - Auger–Meitner KW - NEXAFS KW - FLASH Y1 - 2021 SN - 1420-3049 VL - 26 IS - 21 PB - MDPI CY - Basel ER -