| 1. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley-Blackwell. - 2162-7568 .- 2195-1071.
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 2. |
- Ji, Fuxiang, 1991-, et al.
(författare)
-
Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2024
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron-phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK(-1) based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III-V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 3. |
- Hu, Xiaolong, et al.
(författare)
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Fractal superconducting nanowire single-photon detectors and their applications in polarimetric imaging
- 2024
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Ingår i: Advanced Photon Counting Techniques XVIII. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we review the research and development of the fractal superconducting nanowire single-photon detectors (SNSPDs), including our demonstrations of high-performance devices and systems with over 80% system detection efficiency, negligibly low residual polarization sensitivity, and low timing jitter. Using the fractal SNSPDs, we demonstrate full-Stokes polarimetric imaging LiDAR.
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| 4. |
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| 5. |
- Wang, Sifan, et al.
(författare)
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Fire carbon emissions over Equatorial Asia reduced by shortened dry seasons
- 2023
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Fire carbon emissions over Equatorial Asia (EQAS) play a critical role in the global carbon cycle. Most regional fire emissions (89.0%) occur in the dry season, but how changes in the dry-season length affect the fire emissions remains poorly understood. Here we show that, the length of the EQAS dry season has decreased significantly during 1979–2021, and the delayed dry season onset (5.4 ± 1.6 (± one standard error) days decade−1) due to increased precipitation (36.4 ± 9.1 mm decade−1) in the early dry season is the main reason. The dry season length is strongly correlated with the length of the fire season. Increased precipitation during the early dry season led to a significant reduction (May: −0.7 ± 0.4 Tg C decade−1; August: −12.9 ± 6.7 Tg C decade−1) in fire carbon emissions during the early and peak fire season. Climate models from the Coupled Model Intercomparison Project Phase 6 project a continued decline in future dry season length in EQAS under medium and high-emission scenarios, implying further reductions in fire carbon emissions.
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| 6. |
- Wang, Xiaoming, et al.
(författare)
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Binding geometries of silicate species on ferrihydrite surfaces
- 2018
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Ingår i: ACS Earth and Space Chemistry. - : AMER CHEMICAL SOC. - 2472-3452. ; 2:2, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- Silicate sorption on ferrihydrite surfaces, as monomers, oligomers, and polymers, strongly affects ferrihydrite crystallinity, thermodynamic stability, and surface reactivity. How these silicate species bind on ferrihydrite surfaces is, however, not well understood. We have determined silicate binding geometries using a combination of X-ray absorption spectroscopy (XAS), differential atomic pair distribution function (d-PDF) analysis, and density functional theory (DFT) calculations. Silicon K-edge absorption pre edges and DFT-predicted energies indicate that silicate forms monomeric monodentate mononuclear (MM) complexes at low silicate sorption loadings. With increasing silicate loading, the pre-edge peak shifts to higher energies, suggesting changes in the silicate binding geometry toward multidentate complexation. The d-PDF analysis determines the Si Fe interatomic distance to be 3.25 A for the high-loading samples. The DFT calculations indicate that such distance corresponds to an oligomer in the bidentate binuclear (BB) binding geometry. The transition of the silicate sorption geometry accompanied by polymerization can affect stability of ferrihydrite and its adsorption and redox reactivity and increase the degree of Si isotopic fractionation upon silicate sorption on Fe oxides. MM monomeric complexes and BB oligomeric complexes should be used for surface complexation models predicting silicate sorption on Fe oxide surfaces.
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| 7. |
- Wang, Xiaoming, et al.
(författare)
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Phosphate Sorption Speciation and Precipitation Mechanisms on Amorphous Aluminum Hydroxide
- 2019
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Ingår i: Soil Systems. - : MDPI. - 2571-8789. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum (Al) oxides are important adsorbents for phosphate in soils and sediments, and significantly limit Phosphate (P) mobility and bioavailability, but the speciation of surface-adsorbed phosphate on Al oxides remains poorly understood. Here, phosphate sorption speciation on amorphous Al hydroxide (AAH) was determined under pH 3-8 and P concentration of 0.03 mM-15 mM using various spectroscopic approaches, and phosphate precipitation mechanisms were discussed as well. AAH exhibits an extremely high phosphate sorption capacity, increasing from 3.80 mmol/g at pH 7 to 4.63 mmol/g at pH 3. Regardless of reaction pH, with increasing P sorption loading, the sorption mechanism transits from bidentate binuclear (BB) surface complexation with d(P-Al) of 3.12 angstrom to surface precipitation of analogous amorphous AlPO4 (AAP), possibly with ternary complexes, such as (equivalent to Al-O)(2)-PO2-Al, as intermediate products. Additionally, the percentage of precipitated phosphate occurring in AAP linearly and positively correlates with P sorption loading. Compared to phosphate reaction with ferrihydrite, phosphate adsorbs and precipitates more readily on AAH due to the higher solubility product (K-sp) of AAH. The formation of AAP particles involves Al-III release, which is promoted by phosphate adsorption, and its subsequent precipitation with phosphate at AAH surfaces or in the bulk solution.
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| 8. |
- Zhang, Hanzhi, et al.
(författare)
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Quantitative estimation of the contribution of dustsources to Chinese loess using detrital zircon U-Pbage patterns
- 2016
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Ingår i: Journal of Geophysical Research - Earth Surface. - 2169-9003 .- 2169-9011. ; 121:11, s. 2085-2099
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Tidskriftsartikel (refereegranskat)abstract
- The origin and provenance of the loess deposits of the Chinese Loess Plateau (CLP) are stilldebated. In order to pinpoint the dust sources, surface samples from the piedmont of the NortheasternTibetan Plateau, the Gobi Altai Mountains, and modern eolian dunes from the Tengger desert and Mu Ussand field were analyzed by using the detrital zircon dating technique. In order to quantitatively discriminatethe content of different potential sources, zircon grains of different ages were grouped according to theirtectonic origin. Zircon grains aged from 1300 to 550 Ma were assigned to the Northeastern Tibetan Plateau,and grains aged from 550 to 0 Ma to the Northeastern Tibetan Plateau or the Gobi Altai Mountains, or to acombination of the two. Zircon ages of around 2.8 Ga to 1.3 Ga may be a mixture of sources from theNortheastern Tibetan Plateau, Gobi Altai Mountains, or North China Craton. Sediments from the Tenggerdesert and Mu Us sand field consist of a mixture of the three sources and exhibit a high degree of spatialvariability in terms of their source. In the northern part of the two deserts, 43–83% of the sediments arederived from the Gobi Altai Mountains, while in the south, material from the Northeastern Tibetan Plateaucomprises 51–98% of the sediments. Loess deposits from the CLP also comprise a mixture of the threedifferent sources, with material from the Northeastern Tibetan Plateau making the dominant contribution(65–100%), with material from the North China Craton and the Gobi Altai Mountains comprising 0–35% and0–40% of the loess deposits, respectively. The contributions from the three sources to the loess deposits onCLP vary spatially. Application of the novel statistical method of provenance group analysis demonstratesthat the loess deposits comprise a mixture of material from a broad region of northern China and that theNortheastern Tibetan Plateau material makes the dominant contribution.
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| 9. |
- Zhao, Xiaoming, et al.
(författare)
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Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells
- 2022
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 377:6603, s. 307-310
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Tidskriftsartikel (refereegranskat)abstract
- To understand degradation routes and improve the stability of perovskite solar cells (PSCs), accelerated aging tests are needed. Here, we use elevated temperatures (up to 110 degrees C) to quantify the accelerated degradation of encapsulated CsPbI3 PSCs under constant illumination. Incorporating a two-dimensional (2D) Cs2PbI2Cl2 capping layer between the perovskite active layer and hole-transport layer stabilizes the interface while increasing power conversion efficiency of the all-inorganic PSCs from 14.9 to 17.4%. Devices with this 2D capping layer did not degrade at 35 degrees C and required >= 2100 hours at 110 degrees C under constant illumination to degrade by 20% of their initial efficiency. Degradation acceleration factors based on the observed Arrhenius temperature dependence predict intrinsic lifetimes of 51,000 +/- 7000 hours (>5 years) operating continuously at 35 degrees C.
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