29.
K Jayaramulu, F Geyer, A Schneemann, Š Kment, M Otyepka, R Zboril, D Vollmer, R A Fischer
Hydrophobic Metal–Organic Frameworks Journal Article
In: Advanced Materials, vol. 31, no. 32, pp. 1900820, 2019, ISSN: 0935-9648.
@article{nokey,
title = {Hydrophobic Metal\textendashOrganic Frameworks},
author = {K Jayaramulu and F Geyer and A Schneemann and \v{S} Kment and M Otyepka and R Zboril and D Vollmer and R A Fischer},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201900820},
doi = {https://doi.org/10.1002/adma.201900820},
issn = {0935-9648},
year = {2019},
date = {2019-06-03},
journal = {Advanced Materials},
volume = {31},
number = {32},
pages = {1900820},
abstract = {Abstract Metal\textendashorganic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be overcome by developing stable hydrophobic MOFs whose chemical composition is tuned to ensure that their metal\textendashligand bonds persist even in the presence of moisture and water. However, the design and fabrication of such hydrophobic MOFs pose a significant challenge. Reported syntheses of hydrophobic MOFs are critically summarized, highlighting issues relating to their design, characterization, and practical use. First, wetting of hydrophobic materials is introduced and the four main strategies for synthesizing hydrophobic MOFs are discussed. Afterward, critical challenges in quantifying the wettability of these hydrophobic porous surfaces and solutions to these challenges are discussed. Finally, the reported uses of hydrophobic MOFs in practical applications such as hydrocarbon storage/separation and their use in separating oil spills from water are summarized. Finally, the state of the art is summarized and promising future developments of hydrophobic MOFs are highlighted.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Metal–organic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be overcome by developing stable hydrophobic MOFs whose chemical composition is tuned to ensure that their metal–ligand bonds persist even in the presence of moisture and water. However, the design and fabrication of such hydrophobic MOFs pose a significant challenge. Reported syntheses of hydrophobic MOFs are critically summarized, highlighting issues relating to their design, characterization, and practical use. First, wetting of hydrophobic materials is introduced and the four main strategies for synthesizing hydrophobic MOFs are discussed. Afterward, critical challenges in quantifying the wettability of these hydrophobic porous surfaces and solutions to these challenges are discussed. Finally, the reported uses of hydrophobic MOFs in practical applications such as hydrocarbon storage/separation and their use in separating oil spills from water are summarized. Finally, the state of the art is summarized and promising future developments of hydrophobic MOFs are highlighted.
28.
P Alexa, C Oligschleger, P Gröger, C Morchutt, V Vyas, B V Lotsch, J C Schön, R Gutzler, K Kern
Short-Range Structural Correlations in Amorphous 2D Polymers Journal Article
In: ChemPhysChem, vol. 20, no. 18, pp. 2340-2347, 2019, ISSN: 1439-4235.
@article{,
title = {Short-Range Structural Correlations in Amorphous 2D Polymers},
author = {P Alexa and C Oligschleger and P Gr\"{o}ger and C Morchutt and V Vyas and B V Lotsch and J C Sch\"{o}n and R Gutzler and K Kern},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cphc.201900326},
doi = {10.1002/cphc.201900326},
issn = {1439-4235},
year = {2019},
date = {2019-05-21},
journal = {ChemPhysChem},
volume = {20},
number = {18},
pages = {2340-2347},
abstract = {Abstract Many 2D covalent polymers synthesized as single layers on surfaces show inherent disorder, expressed for example in their ring-size distribution. Systems which are expected to form the thermodynamically favored hexagonal lattice usually deviate from crystallinity and include high numbers of pentagons, heptagons, and rings of other sizes. The amorphous structure of two different covalent polymers in real space using scanning tunneling microscopy is investigated. Molecular dynamics simulations are employed to extract additional information. We show that short-range correlations exist in the structure of one polymer, i. e. that polygons are not tessellating the surface randomly but that ring neighborhoods have preferential compositions. The correlation is dictated by the energy of formation of the ring neighborhoods.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Many 2D covalent polymers synthesized as single layers on surfaces show inherent disorder, expressed for example in their ring-size distribution. Systems which are expected to form the thermodynamically favored hexagonal lattice usually deviate from crystallinity and include high numbers of pentagons, heptagons, and rings of other sizes. The amorphous structure of two different covalent polymers in real space using scanning tunneling microscopy is investigated. Molecular dynamics simulations are employed to extract additional information. We show that short-range correlations exist in the structure of one polymer, i. e. that polygons are not tessellating the surface randomly but that ring neighborhoods have preferential compositions. The correlation is dictated by the energy of formation of the ring neighborhoods.
27.
A Vogel, T Miller, C Hoch, M Jakob, O Oeckler, T Nilges
Cu9.1Te4Cl3: A Thermoelectric Compound with Low Thermal and High Electrical Conductivity Journal Article
In: Inorganic Chemistry, vol. 58, no. 9, pp. 6222-6230, 2019, ISSN: 0020-1669.
@article{,
title = {Cu9.1Te4Cl3: A Thermoelectric Compound with Low Thermal and High Electrical Conductivity},
author = {A Vogel and T Miller and C Hoch and M Jakob and O Oeckler and T Nilges},
url = {https://doi.org/10.1021/acs.inorgchem.9b00453},
doi = {10.1021/acs.inorgchem.9b00453},
issn = {0020-1669},
year = {2019},
date = {2019-05-06},
journal = {Inorganic Chemistry},
volume = {58},
number = {9},
pages = {6222-6230},
abstract = {Cu9.1Te4Cl3 is a new polymorphic compound in the class of coinage metal polytelluride halides. Copper is highly mobile, which results in multiple order\textendashdisorder phase transitions in a limited temperature interval from 240 to 370 K. Mainly as a consequence of thermal transport properties, the compound’s thermoelectric figure of merit reaches values up to ZT = 0.15 in the temperature range between room temperature and 523 K. Its structure is closely related to that of Ag10Te4Br3, another coinage metal polytelluride halide, which represents the first p\textendashn\textendashp-switchable semiconductor approachable by a simple temperature change. The title compound outperforms Ag10Te4Br3 in terms of thermoelectric properties by 1 order of magnitude and therefore acts as a link between the class of p\textendashn\textendashp compounds and thermoelectric materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Cu9.1Te4Cl3 is a new polymorphic compound in the class of coinage metal polytelluride halides. Copper is highly mobile, which results in multiple order–disorder phase transitions in a limited temperature interval from 240 to 370 K. Mainly as a consequence of thermal transport properties, the compound’s thermoelectric figure of merit reaches values up to ZT = 0.15 in the temperature range between room temperature and 523 K. Its structure is closely related to that of Ag10Te4Br3, another coinage metal polytelluride halide, which represents the first p–n–p-switchable semiconductor approachable by a simple temperature change. The title compound outperforms Ag10Te4Br3 in terms of thermoelectric properties by 1 order of magnitude and therefore acts as a link between the class of p–n–p compounds and thermoelectric materials.
26.
S Reiter, M K Roos, R De Vivie-Riedle
Excited State Conformations of Bridged and Unbridged Pyrene Excimers Journal Article
In: Chemphotochem, vol. 3, no. 9, pp. 881-888, 2019, ISSN: 2367-0932.
@article{,
title = {Excited State Conformations of Bridged and Unbridged Pyrene Excimers},
author = {S Reiter and M K Roos and R De Vivie-Riedle},
url = {\<Go to ISI\>://WOS:000487014600024},
doi = {10.1002/cptc.201900096},
issn = {2367-0932},
year = {2019},
date = {2019-05-06},
journal = {Chemphotochem},
volume = {3},
number = {9},
pages = {881-888},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
25.
B Garlyyev, K Kratzl, M Rück, J Michalička, J Fichtner, J M Macak, T Kratky, S Günther, M Cokoja, A S Bandarenka, A Gagliardi, R A Fischer
Optimizing the Size of Platinum Nanoparticles for Enhanced Mass Activity in the Electrochemical Oxygen Reduction Reaction Journal Article
In: Angewandte Chemie International Edition, vol. 58, no. 28, pp. 9596-9600, 2019, ISSN: 1433-7851.
@article{,
title = {Optimizing the Size of Platinum Nanoparticles for Enhanced Mass Activity in the Electrochemical Oxygen Reduction Reaction},
author = {B Garlyyev and K Kratzl and M R\"{u}ck and J Michali\v{c}ka and J Fichtner and J M Macak and T Kratky and S G\"{u}nther and M Cokoja and A S Bandarenka and A Gagliardi and R A Fischer},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201904492},
doi = {10.1002/anie.201904492},
issn = {1433-7851},
year = {2019},
date = {2019-05-03},
journal = {Angewandte Chemie International Edition},
volume = {58},
number = {28},
pages = {9596-9600},
abstract = {Abstract High oxygen reduction (ORR) activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we prepare Pt nanoparticles with optimal size for the efficient ORR in proton-exchange-membrane fuel cells. Optimal nanoparticle sizes are predicted near 1, 2, and 3 nm by computational screening. To corroborate our computational results, we have addressed the challenge of approximately 1 nm sized Pt nanoparticle synthesis with a metal\textendashorganic framework (MOF) template approach. The electrocatalyst was characterized by HR-TEM, XPS, and its ORR activity was measured using a rotating disk electrode setup. The observed mass activities (0.87±0.14 A mgPt−1) are close to the computational prediction (0.99 A mgPt−1). We report the highest to date mass activity among pure Pt catalysts for the ORR within similar size range. The specific and mass activities are twice as high as the Tanaka commercial Pt/C catalysis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract High oxygen reduction (ORR) activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we prepare Pt nanoparticles with optimal size for the efficient ORR in proton-exchange-membrane fuel cells. Optimal nanoparticle sizes are predicted near 1, 2, and 3 nm by computational screening. To corroborate our computational results, we have addressed the challenge of approximately 1 nm sized Pt nanoparticle synthesis with a metal–organic framework (MOF) template approach. The electrocatalyst was characterized by HR-TEM, XPS, and its ORR activity was measured using a rotating disk electrode setup. The observed mass activities (0.87±0.14 A mgPt−1) are close to the computational prediction (0.99 A mgPt−1). We report the highest to date mass activity among pure Pt catalysts for the ORR within similar size range. The specific and mass activities are twice as high as the Tanaka commercial Pt/C catalysis.
24.
A Mähringer, A C Jakowetz, J M Rotter, B J Bohn, J K Stolarczyk, J Feldmann, T Bein, D D Medina
Oriented Thin Films of Electroactive Triphenylene Catecholate-Based Two-Dimensional Metal–Organic Frameworks Journal Article
In: ACS Nano, vol. 13, no. 6, pp. 6711-6719, 2019, ISSN: 1936-0851.
@article{nokey,
title = {Oriented Thin Films of Electroactive Triphenylene Catecholate-Based Two-Dimensional Metal\textendashOrganic Frameworks},
author = {A M\"{a}hringer and A C Jakowetz and J M Rotter and B J Bohn and J K Stolarczyk and J Feldmann and T Bein and D D Medina},
url = {https://doi.org/10.1021/acsnano.9b01137},
doi = {10.1021/acsnano.9b01137},
issn = {1936-0851},
year = {2019},
date = {2019-05-02},
journal = {ACS Nano},
volume = {13},
number = {6},
pages = {6711-6719},
abstract = {Two-dimensional triphenylene-based metal\textendashorganic frameworks (TP-MOFs) attract significant scientific interest due to their long-range order combined with significant electrical conductivity. The deposition of these structures as oriented films is expected to promote their incorporation into diverse optoelectronic devices. However, to date, a controlled deposition strategy applicable for the different members of this MOF family has not been reported yet. Herein, we present the synthesis of highly oriented thin films of TP-MOFs by vapor-assisted conversion (VAC). We targeted the M-CAT-1 series comprising hexahydroxytriphenylene organic ligands and metal-ions such as Ni2+, Co2+, and Cu2+. These planar organic building blocks are connected in-plane to the metal-ions through a square planar node forming extended sheets which undergo self-organization into defined stacks. Highly oriented thin Ni- and Co-CAT-1 films grown on gold substrates feature a high surface coverage with a uniform film topography and thickness ranging from 180 to 200 nm. The inclusion of acid modulators in the synthesis enabled the growth of films with a preferred orientation on quartz and on conductive substrates such as indium-doped tin oxide (ITO). The van der Pauw measurements performed across the M-CAT-1 films revealed high electrical conductivity values of up to 10\textendash3 S cm\textendash1 for both the Ni- and Co-CAT-1 films. Films grown on quartz allowed for a detailed photophysical characterization by means of UV\textendashvis, photoluminescence, and transient absorption spectroscopy. The latter revealed the existence of excited states on a nanosecond time scale, sufficiently long to demonstrate a photoinduced charge generation and extraction in Ni-CAT-1 films. This was achieved by fabricating a basic photovoltaic device with an ITO/Ni-CAT-1/Al architecture, thus establishing this MOF as a photoactive material. Our results point to the intriguing capabilities of these conductive M-CAT-1 materials and an additional scope of applications as photoabsorbers enabled through VAC thin-film synthesis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional triphenylene-based metal–organic frameworks (TP-MOFs) attract significant scientific interest due to their long-range order combined with significant electrical conductivity. The deposition of these structures as oriented films is expected to promote their incorporation into diverse optoelectronic devices. However, to date, a controlled deposition strategy applicable for the different members of this MOF family has not been reported yet. Herein, we present the synthesis of highly oriented thin films of TP-MOFs by vapor-assisted conversion (VAC). We targeted the M-CAT-1 series comprising hexahydroxytriphenylene organic ligands and metal-ions such as Ni2+, Co2+, and Cu2+. These planar organic building blocks are connected in-plane to the metal-ions through a square planar node forming extended sheets which undergo self-organization into defined stacks. Highly oriented thin Ni- and Co-CAT-1 films grown on gold substrates feature a high surface coverage with a uniform film topography and thickness ranging from 180 to 200 nm. The inclusion of acid modulators in the synthesis enabled the growth of films with a preferred orientation on quartz and on conductive substrates such as indium-doped tin oxide (ITO). The van der Pauw measurements performed across the M-CAT-1 films revealed high electrical conductivity values of up to 10–3 S cm–1 for both the Ni- and Co-CAT-1 films. Films grown on quartz allowed for a detailed photophysical characterization by means of UV–vis, photoluminescence, and transient absorption spectroscopy. The latter revealed the existence of excited states on a nanosecond time scale, sufficiently long to demonstrate a photoinduced charge generation and extraction in Ni-CAT-1 films. This was achieved by fabricating a basic photovoltaic device with an ITO/Ni-CAT-1/Al architecture, thus establishing this MOF as a photoactive material. Our results point to the intriguing capabilities of these conductive M-CAT-1 materials and an additional scope of applications as photoabsorbers enabled through VAC thin-film synthesis.
23.
R Wang, Y Tong, K Wang, S Xia, E Kentzinger, O Soltwedel, P Müller-Buschbaum, H Frielinghaus
Monitoring the morphological evolution in mixed-dimensional lead bromide perovskite films with lamellar-stacked perovskite nanoplatelets Journal Article
In: Nanoscale Horizons, vol. 4, no. 5, pp. 1139-1144, 2019, ISSN: 2055-6756.
@article{nokey,
title = {Monitoring the morphological evolution in mixed-dimensional lead bromide perovskite films with lamellar-stacked perovskite nanoplatelets},
author = {R Wang and Y Tong and K Wang and S Xia and E Kentzinger and O Soltwedel and P M\"{u}ller-Buschbaum and H Frielinghaus},
url = {http://dx.doi.org/10.1039/C9NH00156E},
doi = {10.1039/C9NH00156E},
issn = {2055-6756},
year = {2019},
date = {2019-04-23},
journal = {Nanoscale Horizons},
volume = {4},
number = {5},
pages = {1139-1144},
abstract = {Mixed-dimensional lead bromide perovskite films combine the properties of both three-dimensional (3D) and two-dimensional (2D) perovskite crystals, and due to their good humidity tolerance, they emerge as promising candidates for long-term stable optoelectronic applications. In order to further tailor the film morphology aiming for a better device performance, it is important to unravel the structural formation mechanism in these perovskite thin films. In the present study, the formation of 3D lead bromide perovskite crystals and the self-assembly of lamellar-stacked 2D perovskite nanoplatelets are comprehensively studied. Samples are prepared through a two-step vapor assisted route with different vapor exposure times in order to monitor the detailed morphology at the specific reaction stage. With grazing incidence X-ray scattering techniques, the preferential orientation of the 3D crystals is found to decrease upon increasing the reaction time. Also, it is evidenced that well-ordered in-plane lamellar-stacked 2D nanoplatelets form aggregates in the bulk structure only. The obtained hierarchical morphology shows excellent structural stability in a humid atmosphere even at a relative humidity level of 80%. Our findings statistically offer a morphological understanding, which is important for the optimization of the sample preparation route and thus the resulting performance of moisture-tolerant perovskite based optoelectronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mixed-dimensional lead bromide perovskite films combine the properties of both three-dimensional (3D) and two-dimensional (2D) perovskite crystals, and due to their good humidity tolerance, they emerge as promising candidates for long-term stable optoelectronic applications. In order to further tailor the film morphology aiming for a better device performance, it is important to unravel the structural formation mechanism in these perovskite thin films. In the present study, the formation of 3D lead bromide perovskite crystals and the self-assembly of lamellar-stacked 2D perovskite nanoplatelets are comprehensively studied. Samples are prepared through a two-step vapor assisted route with different vapor exposure times in order to monitor the detailed morphology at the specific reaction stage. With grazing incidence X-ray scattering techniques, the preferential orientation of the 3D crystals is found to decrease upon increasing the reaction time. Also, it is evidenced that well-ordered in-plane lamellar-stacked 2D nanoplatelets form aggregates in the bulk structure only. The obtained hierarchical morphology shows excellent structural stability in a humid atmosphere even at a relative humidity level of 80%. Our findings statistically offer a morphological understanding, which is important for the optimization of the sample preparation route and thus the resulting performance of moisture-tolerant perovskite based optoelectronic devices.
22.
R L Z Hoye, M L Lai, M Anaya, Y Tong, K Galkowski, T Doherty, W W Li, T N Huq, S Mackowski, L Polavarapu, J Feldmann, J L Macmanus-Driscoll, R H Friend, A S Urban, S D Stranks
In: Acs Energy Letters, vol. 4, no. 5, pp. 1181-1188, 2019, ISSN: 2380-8195.
@article{,
title = {Identifying and Reducing Interfacial Losses to Enhance Color-Pure Electroluminescence in Blue-Emitting Perovskite Nanoplatelet Light-Emitting Diodes},
author = {R L Z Hoye and M L Lai and M Anaya and Y Tong and K Galkowski and T Doherty and W W Li and T N Huq and S Mackowski and L Polavarapu and J Feldmann and J L Macmanus-Driscoll and R H Friend and A S Urban and S D Stranks},
url = {\<Go to ISI\>://WOS:000468015600025},
doi = {10.1021/acsenergylett.9b00571},
issn = {2380-8195},
year = {2019},
date = {2019-04-17},
journal = {Acs Energy Letters},
volume = {4},
number = {5},
pages = {1181-1188},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
21.
J A Sichert, A Hemmerling, C Cardenas-Daw, A S Urban, J Feldmann
Tuning the optical bandgap in layered hybrid perovskites through variation of alkyl chain length Journal Article
In: Apl Materials, vol. 7, no. 4, 2019, ISSN: 2166-532X.
@article{,
title = {Tuning the optical bandgap in layered hybrid perovskites through variation of alkyl chain length},
author = {J A Sichert and A Hemmerling and C Cardenas-Daw and A S Urban and J Feldmann},
url = {\<Go to ISI\>://WOS:000466615300017},
doi = {10.1063/1.5087296},
issn = {2166-532X},
year = {2019},
date = {2019-04-16},
journal = {Apl Materials},
volume = {7},
number = {4},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
20.
W Chen, J L Zhong, J Z Li, N Saxena, L P Kreuzer, H C Liu, L Song, B Su, D Yang, K Wang, J Schlipf, V Korstgens, T C He, K Wang, P Muller-Buschbaum
Structure and Charge Carrier Dynamics in Colloidal PbS Quantum Dot Solids Journal Article
In: Journal of Physical Chemistry Letters, vol. 10, no. 9, pp. 2058-2065, 2019, ISSN: 1948-7185.
@article{,
title = {Structure and Charge Carrier Dynamics in Colloidal PbS Quantum Dot Solids},
author = {W Chen and J L Zhong and J Z Li and N Saxena and L P Kreuzer and H C Liu and L Song and B Su and D Yang and K Wang and J Schlipf and V Korstgens and T C He and K Wang and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000466991300006},
doi = {10.1021/acs.jpclett.9b00869},
issn = {1948-7185},
year = {2019},
date = {2019-04-09},
urldate = {2019-04-09},
journal = {Journal of Physical Chemistry Letters},
volume = {10},
number = {9},
pages = {2058-2065},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
19.
V Balevičius Jr, T Wei, D Di Tommaso, D Abramavicius, J Hauer, T Polívka, C D P Duffy
The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating Journal Article
In: Chemical Science, vol. 10, no. 18, pp. 4792-4804, 2019, ISSN: 2041-6520.
@article{nokey,
title = {The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating},
author = {V Balevi\v{c}ius Jr and T Wei and D Di Tommaso and D Abramavicius and J Hauer and T Pol\'{i}vka and C D P Duffy},
url = {http://dx.doi.org/10.1039/C9SC00410F},
doi = {10.1039/C9SC00410F},
issn = {2041-6520},
year = {2019},
date = {2019-04-02},
journal = {Chemical Science},
volume = {10},
number = {18},
pages = {4792-4804},
abstract = {In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations. Hence, we present a holistic approach that tracks the internal temperature and vibronic distribution from the act of photo-excitation to the restoration of the global equilibrium. Within this framework internal vibrational redistribution and vibrational cooling are emergent phenomena. We demonstrate the validity of the framework by examining a highly controversial example, carotenoids. We show that correctly accounting for the local temperature unambiguously explains their energetically and temporally congested spectral dynamics without the ad hoc postulation of additional ‘dark’ states. An immediate further application of this approach would be to monitor the excitation and thermal dynamics of pigment\textendashprotein systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations. Hence, we present a holistic approach that tracks the internal temperature and vibronic distribution from the act of photo-excitation to the restoration of the global equilibrium. Within this framework internal vibrational redistribution and vibrational cooling are emergent phenomena. We demonstrate the validity of the framework by examining a highly controversial example, carotenoids. We show that correctly accounting for the local temperature unambiguously explains their energetically and temporally congested spectral dynamics without the ad hoc postulation of additional ‘dark’ states. An immediate further application of this approach would be to monitor the excitation and thermal dynamics of pigment–protein systems.
18.
W Li, S Watzele, H A El-Sayed, Y Liang, G Kieslich, A S Bandarenka, K Rodewald, B Rieger, R A Fischer
Unprecedented High Oxygen Evolution Activity of Electrocatalysts Derived from Surface-Mounted Metal–Organic Frameworks Journal Article
In: Journal of the American Chemical Society, vol. 141, no. 14, pp. 5926-5933, 2019, ISSN: 0002-7863.
@article{,
title = {Unprecedented High Oxygen Evolution Activity of Electrocatalysts Derived from Surface-Mounted Metal\textendashOrganic Frameworks},
author = {W Li and S Watzele and H A El-Sayed and Y Liang and G Kieslich and A S Bandarenka and K Rodewald and B Rieger and R A Fischer},
url = {https://doi.org/10.1021/jacs.9b00549},
doi = {10.1021/jacs.9b00549},
issn = {0002-7863},
year = {2019},
date = {2019-03-19},
journal = {Journal of the American Chemical Society},
volume = {141},
number = {14},
pages = {5926-5933},
abstract = {The oxygen evolution reaction (OER) is a key process for renewable energy storage. However, developing non-noble metal OER electrocatalysts with high activity, long durability and scalability remains a major challenge. Herein, high OER activity and stability in alkaline solution were discovered for mixed nickel/cobalt hydroxide electrocatalysts, which were derived in one-step procedure from oriented surface-mounted metal\textendashorganic framework (SURMOF) thin films that had been directly grown layer-by-layer on macro- and microelectrode substrates. The obtained mass activity of ∼2.5 mA·μg\textendash1 at the defined overpotential of 300 mV is 1 order of magnitude higher than that of the benchmarked IrO2 electrocatalyst and at least 3.5 times higher than the mass activity of any state-of-the-art NiFe-, FeCoW-, or NiCo-based electrocatalysts reported in the literature. The excellent morphology of the SURMOF-derived ultrathin electrocatalyst coating led to a high exposure of the most active Ni- and Co-based sites.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The oxygen evolution reaction (OER) is a key process for renewable energy storage. However, developing non-noble metal OER electrocatalysts with high activity, long durability and scalability remains a major challenge. Herein, high OER activity and stability in alkaline solution were discovered for mixed nickel/cobalt hydroxide electrocatalysts, which were derived in one-step procedure from oriented surface-mounted metal–organic framework (SURMOF) thin films that had been directly grown layer-by-layer on macro- and microelectrode substrates. The obtained mass activity of ∼2.5 mA·μg–1 at the defined overpotential of 300 mV is 1 order of magnitude higher than that of the benchmarked IrO2 electrocatalyst and at least 3.5 times higher than the mass activity of any state-of-the-art NiFe-, FeCoW-, or NiCo-based electrocatalysts reported in the literature. The excellent morphology of the SURMOF-derived ultrathin electrocatalyst coating led to a high exposure of the most active Ni- and Co-based sites.
17.
C Ott, F Reiter, M Baumgartner, M Pielmeier, A Vogel, P Walke, S Burger, M Ehrenreich, G Kieslich, D Daisenberger, J Armstrong, U K Thakur, P Kumar, S Chen, D Donadio, L S Walter, R T Weitz, K Shankar, T Nilges
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems Based on SnIP Journal Article
In: Advanced Functional Materials, vol. 29, no. 18, pp. 1900233, 2019, ISSN: 1616-301X.
@article{,
title = {Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems Based on SnIP},
author = {C Ott and F Reiter and M Baumgartner and M Pielmeier and A Vogel and P Walke and S Burger and M Ehrenreich and G Kieslich and D Daisenberger and J Armstrong and U K Thakur and P Kumar and S Chen and D Donadio and L S Walter and R T Weitz and K Shankar and T Nilges},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201900233},
doi = {10.1002/adfm.201900233},
issn = {1616-301X},
year = {2019},
date = {2019-03-13},
journal = {Advanced Functional Materials},
volume = {29},
number = {18},
pages = {1900233},
abstract = {Abstract Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core\textendashshell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
16.
E Pensa, J Gargiulo, A Lauri, S Schlücker, E Cortés, S A Maier
Spectral Screening of the Energy of Hot Holes over a Particle Plasmon Resonance Journal Article
In: Nano Letters, vol. 19, no. 3, pp. 1867-1874, 2019, ISSN: 1530-6984.
@article{,
title = {Spectral Screening of the Energy of Hot Holes over a Particle Plasmon Resonance},
author = {E Pensa and J Gargiulo and A Lauri and S Schl\"{u}cker and E Cort\'{e}s and S A Maier},
url = {https://doi.org/10.1021/acs.nanolett.8b04950},
doi = {10.1021/acs.nanolett.8b04950},
issn = {1530-6984},
year = {2019},
date = {2019-03-13},
journal = {Nano Letters},
volume = {19},
number = {3},
pages = {1867-1874},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
15.
S Laha, Y Lee, F Podjaski, D Weber, V Duppel, L M Schoop, F Pielnhofer, C Scheurer, K Muller, U Starke, K Reuter, B V Lotsch
Ruthenium Oxide Nanosheets for Enhanced Oxygen Evolution Catalysis in Acidic Medium Journal Article
In: Advanced Energy Materials, vol. 9, no. 15, 2019, ISSN: 1614-6832.
@article{,
title = {Ruthenium Oxide Nanosheets for Enhanced Oxygen Evolution Catalysis in Acidic Medium},
author = {S Laha and Y Lee and F Podjaski and D Weber and V Duppel and L M Schoop and F Pielnhofer and C Scheurer and K Muller and U Starke and K Reuter and B V Lotsch},
url = {\<Go to ISI\>://WOS:000465464500007},
doi = {10.1002/aenm.201803795},
issn = {1614-6832},
year = {2019},
date = {2019-02-21},
journal = {Advanced Energy Materials},
volume = {9},
number = {15},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
14.
B Doiron, M Mota, M P Wells, R Bower, A Mihai, Y Li, L F Cohen, N M Alford, P K Petrov, R F Oulton, S A Maier
Quantifying Figures of Merit for Localized Surface Plasmon Resonance Applications: A Materials Survey Journal Article
In: ACS Photonics, vol. 6, no. 2, pp. 240-259, 2019.
@article{,
title = {Quantifying Figures of Merit for Localized Surface Plasmon Resonance Applications: A Materials Survey},
author = {B Doiron and M Mota and M P Wells and R Bower and A Mihai and Y Li and L F Cohen and N M Alford and P K Petrov and R F Oulton and S A Maier},
url = {https://doi.org/10.1021/acsphotonics.8b01369},
doi = {10.1021/acsphotonics.8b01369},
year = {2019},
date = {2019-02-20},
journal = {ACS Photonics},
volume = {6},
number = {2},
pages = {240-259},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
13.
B Miller, J Lindlau, M Bommert, A Neumann, H Yamaguchi, A W Holleitner, A Högele, U Wurstbauer
Tuning the Fröhlich exciton-phonon scattering in monolayer MoS2 Journal Article
In: Nature Communications, vol. 10, no. 1, pp. 807, 2019, ISSN: 2041-1723.
@article{,
title = {Tuning the Fr\"{o}hlich exciton-phonon scattering in monolayer MoS2},
author = {B Miller and J Lindlau and M Bommert and A Neumann and H Yamaguchi and A W Holleitner and A H\"{o}gele and U Wurstbauer},
url = {https://doi.org/10.1038/s41467-019-08764-3},
doi = {10.1038/s41467-019-08764-3},
issn = {2041-1723},
year = {2019},
date = {2019-02-18},
journal = {Nature Communications},
volume = {10},
number = {1},
pages = {807},
abstract = {Charge carriers in semiconducting transition metal dichalcogenides possess a valley degree of freedom that allows for optoelectronic applications based on the momentum of excitons. At elevated temperatures, scattering by phonons limits valley polarization, making a detailed knowledge about strength and nature of the interaction of excitons with phonons essential. In this work, we directly access exciton-phonon coupling in charge tunable single layer MoS2 devices by polarization resolved Raman spectroscopy. We observe a strong defect mediated coupling between the long-range oscillating electric field induced by the longitudinal optical phonon in the dipolar medium and the exciton. This so-called Fr\"{o}hlich exciton phonon interaction is suppressed by doping. The suppression correlates with a distinct increase of the degree of valley polarization up to 20% even at elevated temperatures of 220 K. Our result demonstrates a promising strategy to increase the degree of valley polarization towards room temperature valleytronic applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Charge carriers in semiconducting transition metal dichalcogenides possess a valley degree of freedom that allows for optoelectronic applications based on the momentum of excitons. At elevated temperatures, scattering by phonons limits valley polarization, making a detailed knowledge about strength and nature of the interaction of excitons with phonons essential. In this work, we directly access exciton-phonon coupling in charge tunable single layer MoS2 devices by polarization resolved Raman spectroscopy. We observe a strong defect mediated coupling between the long-range oscillating electric field induced by the longitudinal optical phonon in the dipolar medium and the exciton. This so-called Fröhlich exciton phonon interaction is suppressed by doping. The suppression correlates with a distinct increase of the degree of valley polarization up to 20% even at elevated temperatures of 220 K. Our result demonstrates a promising strategy to increase the degree of valley polarization towards room temperature valleytronic applications.
12.
E-P Yao, B J Bohn, Y Tong, H Huang, L Polavarapu, J Feldmann
Exciton Diffusion Lengths and Dissociation Rates in CsPbBr3 Nanocrystal–Fullerene Composites: Layer-by-Layer versus Blend Structures Journal Article
In: Advanced Optical Materials, vol. 7, no. 8, pp. 1801776, 2019, ISSN: 2195-1071.
@article{,
title = {Exciton Diffusion Lengths and Dissociation Rates in CsPbBr3 Nanocrystal\textendashFullerene Composites: Layer-by-Layer versus Blend Structures},
author = {E-P Yao and B J Bohn and Y Tong and H Huang and L Polavarapu and J Feldmann},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201801776},
doi = {10.1002/adom.201801776},
issn = {2195-1071},
year = {2019},
date = {2019-02-18},
journal = {Advanced Optical Materials},
volume = {7},
number = {8},
pages = {1801776},
abstract = {Abstract Solution-processable perovskite nanocrystals (NCs) are gaining increasing interest in the field of photovoltaics because of their enhanced stability compared to their thin-film counterparts. However, the charge transfer dynamics in perovskite NC based light-harvesting systems are not well understood. By applying femtosecond differential transmission (DT) spectroscopy the photoinduced charge transfer from inorganic perovskite CsPbBr3 NCs to the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) is investigated for two fundamentally different architectures, namely layer-by-layer heterostructures and blend structures. By varying the thickness of the NC layer on top of the PCBM in the layer-by-layer heterostructure, an exciton diffusion length of 290 ± 28 nm for CsPbBr3 NC is extracted. The diffusion process is followed by an ultrafast exciton dissociation (within 200 fs) at the CsPbBr3 NC/PCBM interface. In blend structures an overall faster charge transfer process is observed. Furthermore, photoconductivity measurements on a blend structure-based photodetector reveal an effective charge extraction from the active layer resulting in a high photosensitivity. DT measurements on this blend structure including adjacent electron- or hole-transport layers give insight into the extraction process and suggest a certain degree of phase segregation, which assists the charge collection.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Solution-processable perovskite nanocrystals (NCs) are gaining increasing interest in the field of photovoltaics because of their enhanced stability compared to their thin-film counterparts. However, the charge transfer dynamics in perovskite NC based light-harvesting systems are not well understood. By applying femtosecond differential transmission (DT) spectroscopy the photoinduced charge transfer from inorganic perovskite CsPbBr3 NCs to the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) is investigated for two fundamentally different architectures, namely layer-by-layer heterostructures and blend structures. By varying the thickness of the NC layer on top of the PCBM in the layer-by-layer heterostructure, an exciton diffusion length of 290 ± 28 nm for CsPbBr3 NC is extracted. The diffusion process is followed by an ultrafast exciton dissociation (within 200 fs) at the CsPbBr3 NC/PCBM interface. In blend structures an overall faster charge transfer process is observed. Furthermore, photoconductivity measurements on a blend structure-based photodetector reveal an effective charge extraction from the active layer resulting in a high photosensitivity. DT measurements on this blend structure including adjacent electron- or hole-transport layers give insight into the extraction process and suggest a certain degree of phase segregation, which assists the charge collection.
11.
P Zimmermann, A Hötger, N Fernandez, A Nolinder, K Müller, J J Finley, A W Holleitner
Toward Plasmonic Tunnel Gaps for Nanoscale Photoemission Currents by On-Chip Laser Ablation Journal Article
In: Nano Letters, vol. 19, no. 2, pp. 1172-1178, 2019, ISSN: 1530-6984.
@article{,
title = {Toward Plasmonic Tunnel Gaps for Nanoscale Photoemission Currents by On-Chip Laser Ablation},
author = {P Zimmermann and A H\"{o}tger and N Fernandez and A Nolinder and K M\"{u}ller and J J Finley and A W Holleitner},
url = {https://doi.org/10.1021/acs.nanolett.8b04612},
doi = {10.1021/acs.nanolett.8b04612},
issn = {1530-6984},
year = {2019},
date = {2019-02-13},
journal = {Nano Letters},
volume = {19},
number = {2},
pages = {1172-1178},
abstract = {We demonstrate that prestructured metal nanogaps can be shaped on-chip to below 10 nm by femtosecond laser ablation. We explore the plasmonic properties and the nonlinear photocurrent characteristics of the formed tunnel junctions. The photocurrent can be tuned from multiphoton absorption toward the laser-induced strong-field tunneling regime in the nanogaps. We demonstrate that a unipolar ballistic electron current is achieved by designing the plasmonic junctions to be asymmetric, which allows ultrafast electronics on the nanometer scale.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We demonstrate that prestructured metal nanogaps can be shaped on-chip to below 10 nm by femtosecond laser ablation. We explore the plasmonic properties and the nonlinear photocurrent characteristics of the formed tunnel junctions. The photocurrent can be tuned from multiphoton absorption toward the laser-induced strong-field tunneling regime in the nanogaps. We demonstrate that a unipolar ballistic electron current is achieved by designing the plasmonic junctions to be asymmetric, which allows ultrafast electronics on the nanometer scale.
10.
P Zimmermann, A Hötger, N Fernandez, A Nolinder, K Müller, J J Finley, A W Holleitner
Toward Plasmonic Tunnel Gaps for Nanoscale Photoemission Currents by On-Chip Laser Ablation Journal Article
In: Nano Letters, vol. 19, no. 2, pp. 1172-1178, 2019, ISSN: 1530-6984.
@article{,
title = {Toward Plasmonic Tunnel Gaps for Nanoscale Photoemission Currents by On-Chip Laser Ablation},
author = {P Zimmermann and A H\"{o}tger and N Fernandez and A Nolinder and K M\"{u}ller and J J Finley and A W Holleitner},
url = {https://doi.org/10.1021/acs.nanolett.8b04612},
doi = {10.1021/acs.nanolett.8b04612},
issn = {1530-6984},
year = {2019},
date = {2019-02-13},
journal = {Nano Letters},
volume = {19},
number = {2},
pages = {1172-1178},
abstract = {We demonstrate that prestructured metal nanogaps can be shaped on-chip to below 10 nm by femtosecond laser ablation. We explore the plasmonic properties and the nonlinear photocurrent characteristics of the formed tunnel junctions. The photocurrent can be tuned from multiphoton absorption toward the laser-induced strong-field tunneling regime in the nanogaps. We demonstrate that a unipolar ballistic electron current is achieved by designing the plasmonic junctions to be asymmetric, which allows ultrafast electronics on the nanometer scale.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We demonstrate that prestructured metal nanogaps can be shaped on-chip to below 10 nm by femtosecond laser ablation. We explore the plasmonic properties and the nonlinear photocurrent characteristics of the formed tunnel junctions. The photocurrent can be tuned from multiphoton absorption toward the laser-induced strong-field tunneling regime in the nanogaps. We demonstrate that a unipolar ballistic electron current is achieved by designing the plasmonic junctions to be asymmetric, which allows ultrafast electronics on the nanometer scale.
9.
T Schröder, M B Scheible, F Steiner, J Vogelsang, P Tinnefeld
Interchromophoric Interactions Determine the Maximum Brightness Density in DNA Origami Structures Journal Article
In: Nano Letters, vol. 19, no. 2, pp. 1275-1281, 2019, ISSN: 1530-6984.
@article{,
title = {Interchromophoric Interactions Determine the Maximum Brightness Density in DNA Origami Structures},
author = {T Schr\"{o}der and M B Scheible and F Steiner and J Vogelsang and P Tinnefeld},
url = {https://doi.org/10.1021/acs.nanolett.8b04845},
doi = {10.1021/acs.nanolett.8b04845},
issn = {1530-6984},
year = {2019},
date = {2019-02-13},
urldate = {2019-02-13},
journal = {Nano Letters},
volume = {19},
number = {2},
pages = {1275-1281},
abstract = {An ideal point light source is as small and as bright as possible. For fluorescent point light sources, homogeneity of the light sources is important as well as that the fluorescent units inside the light source maintain their photophysical properties, which is compromised by dye aggregation. Here we propose DNA origami as a rigid scaffold to arrange dye molecules in a dense pixel array with high control of stoichiometry and dye\textendashdye interactions. In order to find the highest labeling density in a DNA origami structure without influencing dye photophysics, we alter the distance of two ATTO647N dyes in single base pair steps and probe the dye\textendashdye interactions on the single-molecule level. For small distances strong quenching in terms of intensity and fluorescence lifetime is observed. With increasing distance, we observe reduced quenching and molecular dynamics. However, energy transfer processes in the weak coupling regime still have a significant impact and can lead to quenching by singlet-dark-state-annihilation. Our study fills a gap of studying the interactions of dyes relevant for superresolution microscopy with dense labeling and for single-molecule biophysics. Incorporating these findings in a 3D DNA origami object will pave the way to bright and homogeneous DNA origami nanobeads.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
An ideal point light source is as small and as bright as possible. For fluorescent point light sources, homogeneity of the light sources is important as well as that the fluorescent units inside the light source maintain their photophysical properties, which is compromised by dye aggregation. Here we propose DNA origami as a rigid scaffold to arrange dye molecules in a dense pixel array with high control of stoichiometry and dye–dye interactions. In order to find the highest labeling density in a DNA origami structure without influencing dye photophysics, we alter the distance of two ATTO647N dyes in single base pair steps and probe the dye–dye interactions on the single-molecule level. For small distances strong quenching in terms of intensity and fluorescence lifetime is observed. With increasing distance, we observe reduced quenching and molecular dynamics. However, energy transfer processes in the weak coupling regime still have a significant impact and can lead to quenching by singlet-dark-state-annihilation. Our study fills a gap of studying the interactions of dyes relevant for superresolution microscopy with dense labeling and for single-molecule biophysics. Incorporating these findings in a 3D DNA origami object will pave the way to bright and homogeneous DNA origami nanobeads.
8.
J Fichtner, B Garlyyev, S Watzele, H A El-Sayed, J N Schwämmlein, W-J Li, F M Maillard, L Dubau, J Michalička, J M Macak, A W Holleitner, A S Bandarenka
Top-Down Synthesis of Nanostructured Platinum–Lanthanide Alloy Oxygen Reduction Reaction Catalysts: PtxPr/C as an Example Journal Article
In: ACS Applied Materials & Interfaces, vol. 11, no. 5, pp. 5129-5135, 2019, ISSN: 1944-8244.
@article{,
title = {Top-Down Synthesis of Nanostructured Platinum\textendashLanthanide Alloy Oxygen Reduction Reaction Catalysts: PtxPr/C as an Example},
author = {J Fichtner and B Garlyyev and S Watzele and H A El-Sayed and J N Schw\"{a}mmlein and W-J Li and F M Maillard and L Dubau and J Michali\v{c}ka and J M Macak and A W Holleitner and A S Bandarenka},
url = {https://doi.org/10.1021/acsami.8b20174},
doi = {10.1021/acsami.8b20174},
issn = {1944-8244},
year = {2019},
date = {2019-02-06},
journal = {ACS Applied Materials \& Interfaces},
volume = {11},
number = {5},
pages = {5129-5135},
abstract = {The oxygen reduction reaction (ORR) is of great interest for future sustainable energy conversion and storage, especially concerning fuel cell applications. The preparation of active, affordable, and scalable electrocatalysts and their application in fuel cell engines of hydrogen cars is a prominent step toward the reduction of air pollution, especially in urban areas. Alloying nanostructured Pt with lanthanides is a promising approach to enhance its catalytic ORR activity, whereby the development of a simple synthetic route turned out to be a nontrivial endeavor. Herein, for the first time, we present a successful single-step, scalable top-down synthetic route for Pt\textendashlanthanide alloy nanoparticles, as witnessed by the example of Pr-alloyed Pt nanoparticles. The catalyst was characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and photoelectron spectroscopy, and its electrocatalytic oxygen reduction activity was investigated using a rotating disk electrode technique. PtxPr/C showed ∼3.5 times higher [1.96 mA/cm2Pt, 0.9 V vs reversible hydrogen electrode (RHE)] specific activity and ∼1.7 times higher (0.7 A/mgPt, 0.9 V vs RHE) mass activity compared to commercial Pt/C catalysts. On the basis of previous findings and characterization of the PtxPr/C catalyst, the activity improvement over commercial Pt/C originates from a lattice strain introduced by the alloying process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The oxygen reduction reaction (ORR) is of great interest for future sustainable energy conversion and storage, especially concerning fuel cell applications. The preparation of active, affordable, and scalable electrocatalysts and their application in fuel cell engines of hydrogen cars is a prominent step toward the reduction of air pollution, especially in urban areas. Alloying nanostructured Pt with lanthanides is a promising approach to enhance its catalytic ORR activity, whereby the development of a simple synthetic route turned out to be a nontrivial endeavor. Herein, for the first time, we present a successful single-step, scalable top-down synthetic route for Pt–lanthanide alloy nanoparticles, as witnessed by the example of Pr-alloyed Pt nanoparticles. The catalyst was characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and photoelectron spectroscopy, and its electrocatalytic oxygen reduction activity was investigated using a rotating disk electrode technique. PtxPr/C showed ∼3.5 times higher [1.96 mA/cm2Pt, 0.9 V vs reversible hydrogen electrode (RHE)] specific activity and ∼1.7 times higher (0.7 A/mgPt, 0.9 V vs RHE) mass activity compared to commercial Pt/C catalysts. On the basis of previous findings and characterization of the PtxPr/C catalyst, the activity improvement over commercial Pt/C originates from a lattice strain introduced by the alloying process.
7.
T Wu, Y Luo, S A Maier, L Wei
Phase-matching and Peak Nonlinearity Enhanced Third-Harmonic Generation in Graphene Plasmonic Coupler Journal Article
In: Physical Review Applied, vol. 11, no. 1, pp. 014049, 2019.
@article{,
title = {Phase-matching and Peak Nonlinearity Enhanced Third-Harmonic Generation in Graphene Plasmonic Coupler},
author = {T Wu and Y Luo and S A Maier and L Wei},
url = {https://link.aps.org/doi/10.1103/PhysRevApplied.11.014049},
doi = {10.1103/PhysRevApplied.11.014049},
year = {2019},
date = {2019-01-24},
journal = {Physical Review Applied},
volume = {11},
number = {1},
pages = {014049},
abstract = {Strong nonlinear optical effects generally require giant optical fields interacting with the nonlinear media. Doped graphene hosts electrically tunable plasmons with long lifetimes that interact strongly with light. We investigate a graphene plasmonic coupler and explore two mechanisms to pursue highly efficient third-harmonic generation (THG): (1) phase matching of graphene plasmons at fundamental- and third-harmonic frequencies and (2) peak third-order nonlinear susceptibility of doped graphene. The third-harmonic wave is mainly converted from the evanescent mode of the incident light and the THG efficiency is found to be enhanced by over 10 orders of magnitude compared with a bare monolayer graphene. The significantly enhanced nonlinear optical responses in the graphene plasmonic coupler make this configuration an ideal platform for the development of alternative frequency generators and for signal processing at midinfrared and terahertz frequencies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Strong nonlinear optical effects generally require giant optical fields interacting with the nonlinear media. Doped graphene hosts electrically tunable plasmons with long lifetimes that interact strongly with light. We investigate a graphene plasmonic coupler and explore two mechanisms to pursue highly efficient third-harmonic generation (THG): (1) phase matching of graphene plasmons at fundamental- and third-harmonic frequencies and (2) peak third-order nonlinear susceptibility of doped graphene. The third-harmonic wave is mainly converted from the evanescent mode of the incident light and the THG efficiency is found to be enhanced by over 10 orders of magnitude compared with a bare monolayer graphene. The significantly enhanced nonlinear optical responses in the graphene plasmonic coupler make this configuration an ideal platform for the development of alternative frequency generators and for signal processing at midinfrared and terahertz frequencies.
6.
J Li, E Tan, N Keller, Y-H Chen, P M Zehetmaier, A C Jakowetz, T Bein, P Knochel
Cobalt-Catalyzed Electrophilic Aminations with Anthranils: An Expedient Route to Condensed Quinolines Journal Article
In: Journal of the American Chemical Society, vol. 141, no. 1, pp. 98-103, 2019, ISSN: 0002-7863.
@article{,
title = {Cobalt-Catalyzed Electrophilic Aminations with Anthranils: An Expedient Route to Condensed Quinolines},
author = {J Li and E Tan and N Keller and Y-H Chen and P M Zehetmaier and A C Jakowetz and T Bein and P Knochel},
url = {https://doi.org/10.1021/jacs.8b11466},
doi = {10.1021/jacs.8b11466},
issn = {0002-7863},
year = {2019},
date = {2019-01-09},
journal = {Journal of the American Chemical Society},
volume = {141},
number = {1},
pages = {98-103},
abstract = {The reaction of various organozinc pivalates with anthranils provides anilines derivatives, which cyclize under acidic conditions providing condensed quinolines. Using alkenylzinc pivalates, electron-rich arylzinc pivalates or heterocyclic zinc pivalates produces directly the condensed quinolines of which several structures belong to new heterocyclic scaffolds. These N-heterocycles are of particular interest for organic light emitting diodes with their high photoluminescence quantum yields and long exciton lifetimes as well as for hole-transporting materials in methylammonium lead iodide perovskites solar cells due to an optimal band alignment for holes and a large bandgap.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The reaction of various organozinc pivalates with anthranils provides anilines derivatives, which cyclize under acidic conditions providing condensed quinolines. Using alkenylzinc pivalates, electron-rich arylzinc pivalates or heterocyclic zinc pivalates produces directly the condensed quinolines of which several structures belong to new heterocyclic scaffolds. These N-heterocycles are of particular interest for organic light emitting diodes with their high photoluminescence quantum yields and long exciton lifetimes as well as for hole-transporting materials in methylammonium lead iodide perovskites solar cells due to an optimal band alignment for holes and a large bandgap.
5.
M Rück, A S Bandarenka, F Calle-Vallejo, A Gagliardi
Oxygen Reduction Reaction: Rapid Prediction of Mass Activity of Nanostructured Platinum Electrocatalysts Journal Article
In: The Journal of Physical Chemistry Letters, vol. 9, no. 15, pp. 4463-4468, 2018.
@article{nokey,
title = {Oxygen Reduction Reaction: Rapid Prediction of Mass Activity of Nanostructured Platinum Electrocatalysts},
author = {M R\"{u}ck and A S Bandarenka and F Calle-Vallejo and A Gagliardi},
url = {https://doi.org/10.1021/acs.jpclett.8b01864},
doi = {10.1021/acs.jpclett.8b01864},
year = {2018},
date = {2018-07-20},
urldate = {2018-07-20},
journal = {The Journal of Physical Chemistry Letters},
volume = {9},
number = {15},
pages = {4463-4468},
abstract = {Tailored Pt nanoparticle catalysts are promising candidates to accelerate the oxygen reduction reaction (ORR) in fuel cells. However, the search for active nanoparticle catalysts is hindered by the laborious effort of experimental synthesis and measurements. On the other hand, density functional theory-based approaches are still time-consuming and often not efficient. In this study, we introduce a computational model which enables rapid catalytic activity calculation of unstrained pure Pt nanoparticle electrocatalysts. Regarding particle size effects on Pt nanoparticles, experimental catalytic mass activities from previous studies are accurately reproduced by our computational model. Moreover, beyond available experiments, our computational model identifies potential enhancement in mass activity up to 190% over the experimentally detected maximum. Importantly, the rapid activity calculation enabled by our computational model may pave the way for extensive nanoparticle screening to expedite the search for improved electrocatalysts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Tailored Pt nanoparticle catalysts are promising candidates to accelerate the oxygen reduction reaction (ORR) in fuel cells. However, the search for active nanoparticle catalysts is hindered by the laborious effort of experimental synthesis and measurements. On the other hand, density functional theory-based approaches are still time-consuming and often not efficient. In this study, we introduce a computational model which enables rapid catalytic activity calculation of unstrained pure Pt nanoparticle electrocatalysts. Regarding particle size effects on Pt nanoparticles, experimental catalytic mass activities from previous studies are accurately reproduced by our computational model. Moreover, beyond available experiments, our computational model identifies potential enhancement in mass activity up to 190% over the experimentally detected maximum. Importantly, the rapid activity calculation enabled by our computational model may pave the way for extensive nanoparticle screening to expedite the search for improved electrocatalysts.
4.
A Kuhn, O Gerbig, C Zhu, F Falkenberg, J Maier, B V Lotsch
A new ultrafast superionic Li-conductor: ion dynamics in Li11Si2PS12 and comparison with other tetragonal LGPS-type electrolytes Journal Article
In: Physical Chemistry Chemical Physics, vol. 16, no. 28, pp. 14669-14674, 2014, ISSN: 1463-9076.
@article{nokey,
title = {A new ultrafast superionic Li-conductor: ion dynamics in Li11Si2PS12 and comparison with other tetragonal LGPS-type electrolytes},
author = {A Kuhn and O Gerbig and C Zhu and F Falkenberg and J Maier and B V Lotsch},
url = {http://dx.doi.org/10.1039/C4CP02046D},
doi = {10.1039/C4CP02046D},
issn = {1463-9076},
year = {2014},
date = {2014-05-23},
journal = {Physical Chemistry Chemical Physics},
volume = {16},
number = {28},
pages = {14669-14674},
abstract = {We report on a new ultrafast solid electrolyte of the composition Li11Si2PS12, which exhibits a higher room-temperature Li ion diffusivity than the present record holder Li10GeP2S12. We discuss the high-pressure synthesis and ion dynamics of tetragonal Li11Si2PS12, and comparison is made with our investigations of related members of the LMePS family, i.e. electrolytes of the general formula Li11−xMe2−xP1+xS12 with Me = Ge, Sn : Li10GeP2S12, Li7GePS8, Li10SnP2S12. The structure and dynamics were studied with multiple complementary techniques and the macroscopic diffusion could be traced back to fast Li ion hopping in the crystalline lattice. A clear correlation between the diffusivity and the unit cell volume of the LGPS-type electrolytes was observed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report on a new ultrafast solid electrolyte of the composition Li11Si2PS12, which exhibits a higher room-temperature Li ion diffusivity than the present record holder Li10GeP2S12. We discuss the high-pressure synthesis and ion dynamics of tetragonal Li11Si2PS12, and comparison is made with our investigations of related members of the LMePS family, i.e. electrolytes of the general formula Li11−xMe2−xP1+xS12 with Me = Ge, Sn : Li10GeP2S12, Li7GePS8, Li10SnP2S12. The structure and dynamics were studied with multiple complementary techniques and the macroscopic diffusion could be traced back to fast Li ion hopping in the crystalline lattice. A clear correlation between the diffusivity and the unit cell volume of the LGPS-type electrolytes was observed.
3.
R Natālija, B Andreas, I Hristo, W Rafał
Sub-20-attosecond timing jitter from a mode-locked 200-MHz All-PM Er:NALM fiber laser Proceedings Article
In: Proc.SPIE, pp. 128650L, 0000.
@inproceedings{nokey,
title = {Sub-20-attosecond timing jitter from a mode-locked 200-MHz All-PM Er:NALM fiber laser},
author = {R Nat\={a}lija and B Andreas and I Hristo and W Rafa\l},
url = {https://doi.org/10.1117/12.2692373},
doi = {10.1117/12.2692373},
booktitle = {Proc.SPIE},
volume = {12865},
pages = {128650L},
abstract = {Our research team has achieved a significant milestone by generating pulses with sub-20-attosecond (as) timing jitter from a 200-MHz all-Polarization-Maintaining (PM) erbium-doped (Er:) Nonlinear Amplifying Loop Mirror (NALM) fiber laser. Accurate measurement of these temporal fluctuations was conducted using the Balanced Optical cross-Correlation (BOC) technique. Through comprehensive investigation, we identified the critical parameters responsible for timing jitter, including dispersion and pump power, and validated their impact. The fine-tuning of the contributing factors allowed us to demonstrate an exceptionally low integrated timing jitter of only 15.59 attoseconds, integrated from 10 kHz to 10 MHz. This accomplishment stands as the lowest value ever documented for any free-running mode-locked fiber lasers that are erbium-doped.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Our research team has achieved a significant milestone by generating pulses with sub-20-attosecond (as) timing jitter from a 200-MHz all-Polarization-Maintaining (PM) erbium-doped (Er:) Nonlinear Amplifying Loop Mirror (NALM) fiber laser. Accurate measurement of these temporal fluctuations was conducted using the Balanced Optical cross-Correlation (BOC) technique. Through comprehensive investigation, we identified the critical parameters responsible for timing jitter, including dispersion and pump power, and validated their impact. The fine-tuning of the contributing factors allowed us to demonstrate an exceptionally low integrated timing jitter of only 15.59 attoseconds, integrated from 10 kHz to 10 MHz. This accomplishment stands as the lowest value ever documented for any free-running mode-locked fiber lasers that are erbium-doped.
2.
R Ovcharenko, X Y Xu, B P Fingerhut
Scalable Distributed Memory Implementation of the Quasi-Adiabatic Propagator Path Integral Journal Article
In: Journal of Chemical Theory and Computation, 0000, ISSN: 1549-9618.
@article{nokey,
title = {Scalable Distributed Memory Implementation of the Quasi-Adiabatic Propagator Path Integral},
author = {R Ovcharenko and X Y Xu and B P Fingerhut},
url = {\<Go to ISI\>://WOS:001735510300001},
doi = {10.1021/acs.jctc.6c00002},
issn = {1549-9618},
journal = {Journal of Chemical Theory and Computation},
abstract = {The accurate simulation of dissipative quantum dynamics subject to a non-Markovian environment poses persistent numerical challenges, in particular, for structured environments, where sharp mode resonances induce long-time system bath correlations. We present a scalable distributed memory implementation of the mask-assisted coarse graining of influence coefficients (MACGIC)-quasi-adiabatic propagator path integral (-QUAPI) method that exploits the memory resources of multiple compute nodes and mitigates the memory bottleneck of the method via a new premerging algorithm and a hash-based look-up (hMACGIC-QUAPI) while preserving numerical accuracy. The source code of the hMACGIC-QUAPI implementation is available in a publicly accessible Git repository under GPL license. The developed distributed memory implementation spreads the paths over the computing nodes by means of the MPI protocol, and efficient high level path management is achieved via the hash map-based implementation with constant access time. The efficiency of the implementation is demonstrated in large-scale dissipative quantum dynamics simulations that account for the coupling to a structured non-Markovian environment containing a sharp resonance, a setup for which convergence properties are investigated in depth. Broad applicability and the nonperturbative nature of the simulation method is illustrated via the tuning of the mode resonance frequency of the structured environment with respect to the characteristic system frequency. The simulations reveal a splitting of resonances due to a strong system-environment interaction and the emergence of sidebands due to multiexcitations of the bosonic mode that are not accounted for in perturbative approaches. The simulations demonstrate the versatility of the new hMACGIC-QUAPI method in the presence of strong non-Markovian system bath correlations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The accurate simulation of dissipative quantum dynamics subject to a non-Markovian environment poses persistent numerical challenges, in particular, for structured environments, where sharp mode resonances induce long-time system bath correlations. We present a scalable distributed memory implementation of the mask-assisted coarse graining of influence coefficients (MACGIC)-quasi-adiabatic propagator path integral (-QUAPI) method that exploits the memory resources of multiple compute nodes and mitigates the memory bottleneck of the method via a new premerging algorithm and a hash-based look-up (hMACGIC-QUAPI) while preserving numerical accuracy. The source code of the hMACGIC-QUAPI implementation is available in a publicly accessible Git repository under GPL license. The developed distributed memory implementation spreads the paths over the computing nodes by means of the MPI protocol, and efficient high level path management is achieved via the hash map-based implementation with constant access time. The efficiency of the implementation is demonstrated in large-scale dissipative quantum dynamics simulations that account for the coupling to a structured non-Markovian environment containing a sharp resonance, a setup for which convergence properties are investigated in depth. Broad applicability and the nonperturbative nature of the simulation method is illustrated via the tuning of the mode resonance frequency of the structured environment with respect to the characteristic system frequency. The simulations reveal a splitting of resonances due to a strong system-environment interaction and the emergence of sidebands due to multiexcitations of the bosonic mode that are not accounted for in perturbative approaches. The simulations demonstrate the versatility of the new hMACGIC-QUAPI method in the presence of strong non-Markovian system bath correlations.
1.
J Rojas, Z Wang, F Liu, J A Fereiro, D Chryssikos, T Dittrich, D Leister, D Cahen, M Tornow
Current Rectification Via Photosystem I Monolayers Induced by Their Orientation on Hydrophilic Self-Assembled Monolayers on Titanium Nitride Proceedings Article
In: 2024 IEEE 24th International Conference on Nanotechnology (NANO), pp. 266-271, 0000, ISBN: 1944-9380.
@inproceedings{nokey,
title = {Current Rectification Via Photosystem I Monolayers Induced by Their Orientation on Hydrophilic Self-Assembled Monolayers on Titanium Nitride},
author = {J Rojas and Z Wang and F Liu and J A Fereiro and D Chryssikos and T Dittrich and D Leister and D Cahen and M Tornow},
doi = {10.1109/NANO61778.2024.10628956},
isbn = {1944-9380},
booktitle = {2024 IEEE 24th International Conference on Nanotechnology (NANO)},
pages = {266-271},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}