1. Solution-processed graphene-nanographene van der Waals heterostructures for photodetectors with efficient and ultralong charge separationZhaoyang Liu, Haixin Qiu, Shuai Fu, Can Wang, Xuelin Yao, Alex Dixon, Stéphane Campidelli, Egon Pavlica, Gvido Bratina, Sheng Zhao, Loïc Rondin, 2021, original scientific article Keywords: absorption, colloids, molecules, sensors, two dimensional materials
Published in RUNG: 28.02.2023; Views: 1627; Downloads: 0 |
2. Resolving the dilemma of Fe-N-C catalysts by the selective synthesis of tetrapyrrolic active sites via an imprinting strategyDavide Menga, Jian Liang Low, Yan-Sheng Li, Iztok Arčon, Burak Koyutürk, Friedrich Wagner, Francisco Ruiz-Zepeda, Miran Gaberšček, Beate Paulus, Tim-Patrick Fellinger, 2021, original scientific article Abstract: Combining the abundance and inexpensiveness of
their constituent elements with their atomic dispersion, atomically
dispersed Fe−N−C catalysts represent the most promising
alternative to precious-metal-based materials in proton exchange
membrane (PEM) fuel cells. Due to the high temperatures
involved in their synthesis and the sensitivity of Fe ions toward
carbothermal reduction, current synthetic methods are intrinsically
limited in type and amount of the desired, catalytically active Fe−
N4 sites, and high active site densities have been out of reach
(dilemma of Fe−N−C catalysts). We herein identify a paradigm
change in the synthesis of Fe−N−C catalysts arising from the
developments of other M−N−C single-atom catalysts. Supported
by DFT calculations we propose fundamental principles for the synthesis of M−N−C materials. We further exploit the proposed
principles in a novel synthetic strategy to surpass the dilemma of Fe−N−C catalysts. The selective formation of tetrapyrrolic Zn−N4
sites in a tailor-made Zn−N−C material is utilized as an active-site imprint for the preparation of a corresponding Fe−N−C catalyst.
By successive low- and high-temperature ion exchange reactions, we obtain a phase-pure Fe−N−C catalyst, with a high loading of
atomically dispersed Fe (>3 wt %). Moreover, the catalyst is entirely composed of tetrapyrrolic Fe−N4 sites. The density of
tetrapyrrolic Fe−N4 sites is more than six times as high as for previously reported tetrapyrrolic single-site Fe−N−C fuel cell catalysts
Keywords: Fe-N-C catalysts, selective synthesis, tetrapyrrolic active sites, EXAFS, XANES, single atom, DFT
Published in RUNG: 25.10.2021; Views: 2627; Downloads: 55
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3. On the GeV Emission of the Type I BdHN GRB 130427ARemo Ruffini, Rahim Moradi, Jorge Armando Rueda, Carlo Luciano Bianco, Christian Cherubini, Simonetta Filippi, Yen-Chen Chen, Mile Karlica, Narek Sahakyan, Yu Wang, She Sheng Xue, Laura Beccera, 2019, original scientific article Abstract: We propose that the inner engine of a type I binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field B_0 aligned with the BH rotation axis and surrounded by an ionized plasma of extremely low density of 10^−14 g cm−3. Using GRB 130427A as a prototype, we show that this inner engine acts in a sequence of elementary impulses. Electrons accelerate to ultrarelativistic energy near the BH horizon, propagating along the polar axis, θ = 0, where they can reach energies of ~10^18 eV, partially contributing to ultrahigh-energy cosmic rays. When propagating with $\theta \ne 0$ through the magnetic field B_0, they produce GeV and TeV radiation through synchroton emission. The mass of BH, M = 2.31M ⊙, its spin, α = 0.47, and the value of magnetic field B_0 = 3.48 × 10^10 G, are determined self consistently to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${ \mathcal E }\sim {10}^{37}$ erg is ~10^−14 s at the beginning of the process, then slowly increases with time evolution. In principle, this "inner engine" can operate in a gamma-ray burst (GRB) for thousands of years. By scaling the BH mass and the magnetic field, the same inner engine can describe active galactic nuclei.
Keywords: black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical Phenomena
Published in RUNG: 20.07.2020; Views: 3433; Downloads: 0
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