| 41. |
- Luo, Yang, et al.
(författare)
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Three-dimensional and temperature-dependent electronic structure of the heavy-fermion compound CePt2In7 studied by angle-resolved photoemission spectroscopy
- 2020
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 101:11
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Tidskriftsartikel (refereegranskat)abstract
- The three-dimensional and temperature-dependent electronic structures of the heavy-fermion superconductor CePt2In7 are investigated. Angle-resolved photoemission spectroscopy using variable photon energy establishes the existence of quasi-two- and three-dimensional Fermi surface topologies. Temperature-dependent 4d-4f on-resonance photoemission spectroscopies data reveal that heavy quasiparticle bands begin to form at a temperature well above the characteristic (coherence) temperature T+. The emergence of low-lying crystal electric field excitation may be responsible for the "relocalization" or the precursor to the establishment of heavy electrons coherence in heavy-fermion compounds. These findings provide critical insight into understanding the hybridization in heavy-fermion systems.
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| 42. |
- Ma, Yong, et al.
(författare)
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Local structures of nitrogen doped graphdiynes determined by computational X-ray spectroscopy
- 2019
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Ingår i: Carbon. - : Elsevier Ltd. - 0008-6223 .- 1873-3891. ; 149, s. 672-678
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen doping is an important method to modulate electronic structure of two-dimensional carbon materials. The properties of the doped systems are heavily dependent on the local structure of nitrogen dopants involved, which are often determined by experimental X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) at the nitrogen K-edge. In the present work, the N1s XPS and NEXAFS spectra of nitrogen-doped graphdiynes have been accurately calculated at the density functional theory level. Five representative nitrogen-dopants in graphdiynes, namely [pyridinic, amino, graphitic, and two sp-hybridized N (sp-N-1 and sp-N-2) local structures], are fully examined, from which all experimental features could be correctly assigned. The calculated results can be used to determine the ratio of different nitrogen dopants in graphdiyne at different elevated temperatures reported in previous experiments. Our findings provide the basic references for structure determination of nitrogen doped graphdiyne and new understanding of the underlying structure-property relationships.
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| 43. |
- Ma, Yong, et al.
(författare)
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The equilibrium geometry of A@C60 : A test case for conventional density functional theory
- 2014
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 591, s. 312-316
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Tidskriftsartikel (refereegranskat)abstract
- Potential energy surfaces (PESs) along the reaction pathway towards the center of CC bond between two six membered rings for ten different endohedral fullerenes A@C60 (A = H, C, O, S, N, P, He, Ne, Ar, Kr) have been studied by density functional theory (DFT) and Hartree-Fock (HF) method. The results show that no suitable method can consistently describe the interaction between atom A and carbon cage. The dispersion corrected DFT methods fail to describe the equilibrium geometry and PES of the complexes with light atoms. Nevertheless, the inclusion of the dispersion stabilizes the system as reflected by interaction energies (IEs) between atom A and C60.
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| 44. |
- Pang, Kanglei, 1993-, et al.
(författare)
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Redirecting configuration of atomically dispersed selenium catalytic sites for efficient hydrazine oxidation
- 2024
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Ingår i: Matter. - 2590-2393 .- 2590-2385. ; 7:2, s. 655-667
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the reconstruction of surface sites is crucial for gaining insights into the true active sites and catalytic mechanisms. While extensive research has been conducted on reconstruction behaviors of atomically dispersed metallic catalytic sites, limited attention has been paid to non-metallic ones despite their potential catalytic activity comparable or even superior to their noble-metal counterpart. Herein, we report a carbonaceous, atomically dispersed non-metallic selenium catalyst that displayed exceptional catalytic activity in the hydrazine oxidation reaction (HzOR) in alkaline media, outperforming the noble-metal Pt catalysts. In situ X-ray absorption spectroscopy (XAS) and Fourier transform infrared spectroscopy revealed that the pristine SeC4 site pre-adsorbs an ∗OH ligand, followed by HzOR occurring on the other side of the OH–SeC4. Theoretical calculations proposed that the pre-adsorbed ∗OH group pulls electrons from the Se site, resulting in a more positively charged Se and a higher polarity of Se–C bonds, thereby enhancing surface reactivity toward HzO/R.
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| 45. |
- Pecunia, Vincenzo, et al.
(författare)
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Roadmap on energy harvesting materials
- 2023
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Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
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| 46. |
- Qian, Chaoju, et al.
(författare)
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Population dynamics of Agriophyllum squarrosum, a pioneer annual plant endemic to mobile sand dunes, in response to global climate change
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Climate change plays an important role in the transition of ecosystems. Stratigraphic investigations have suggested that the Asian interior experienced frequent transitions between grassland and desert ecosystems as a consequence of global climate change. Using maternally and bi-parentally inherited markers, we investigated the population dynamics of Agriophyllum squarrosum (Chenopodiaceae), an annual pioneer plant endemic to mobile sand dunes. Phylogeographic analysis revealed that A. squarrosum could originate from Gurbantunggut desert since similar to 1.6 Ma, and subsequently underwent three waves of colonisation into other deserts and sandy lands corresponding to several glaciations. The rapid population expansion and distribution range shifts of A. squarrosum from monsoonal climate zones suggested that the development of the monsoonal climate significantly enhanced the population growth and gene flow of A. squarrosum. These data also suggested that desertification of the fragile grassland ecosystems in the Qinghai-Tibetan Plateau was more ancient than previously suggested and will be aggravated under global warming in the future. This study provides new molecular phylogeographic insights into how pioneer annual plant species in desert ecosystems respond to global climate change, and facilitates evaluation of the ecological potential and genetic resources of future crops for non-arable dry lands to mitigate climate change.
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| 47. |
- Qiu, Feifei, et al.
(författare)
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Optical Images of Molecular Vibronic Couplings from Tip-Enhanced Fluorescence Excitation SpectroscopyY
- 2022
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Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 2:1, s. 150-158
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Tidskriftsartikel (refereegranskat)abstract
- Tip-based photoemission spectroscopic techniques have now achieved subnanometer resolution that allows visualization of the chemical structure and even the ground-state vibrational modes of a single molecule. However, the ability to visualize the interplay between electronic and nuclear motions of excited states, i.e., vibronic couplings, is yet to be explored. Herein, we theoretically propose a new technique, namely, tip-enhanced fluorescence excitation (TEFE). TEFE takes advantage of the highly confined plasmonic field and thus can offer a possibility to directly visualize the vibronic effect of a single molecule in real space for arbitrary excited states in a given energy window. Numerical simulations for a single porphine molecule confirm that vibronic couplings originating from Herzberg-Teller (HT) active modes can be visually identified. TEFE further enables high-order vibrational transitions that are normally suppressed in the other plasmon-based processes. Images of the combination vibrational transitions have the same pattern as that of their parental HT active mode's fundamental transition, providing a direct protocol for measurements of the activity of Franck-Condon modes of selected excited states. These findings strongly suggest that TEFE is a powerful strategy to identify the involvement of molecular moieties in the complicated electron-nuclear interactions of the excited states at the single-molecule level.
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| 48. |
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