| 1. |
- Bera, Suman, et al.
(författare)
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Limiting Heterovalent B-Site Doping in CsPbI3 Nanocrystals : Phase and Optical Stability
- 2019
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Ingår i: ACS Energy Letters. - : AMER CHEMICAL SOC. - 2380-8195. ; 4:6, s. 1364-1369
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Tidskriftsartikel (refereegranskat)abstract
- B-site doping with various metal ions in alpha-CsPbI3 has been proven to be a potential approach in bringing phase stability to these nanocrystals. However, while the doping of various homovalent ions in replacing Pb(II) has been extensively studied, heterovalent doping was observed to be limited. To understand the impact of heterovalent doping, Sb(III) was chosen here as an effective dopant for occupying the Pb(II) position in CsPbI3 nanocrystals. Importantly, it was observed that insertion of Sb(III) also stabilized the crystal phase of these red-emitting nanocrystals, but only with limited doping. However, with more intake, the cube shape turned to platelet and therefore also reduced the stability. Details of the insights of formation of these doped nanostructures are investigated, and further, these were implemented for photovoltaic application and comparable efficiency was recorded.
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| 2. |
- Beri, Aru, et al.
(författare)
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AstroSat observations of the first Galactic ULX pulsar Swift J0243.6+6124
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:1, s. 565-575
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Tidskriftsartikel (refereegranskat)abstract
- Swift J0243.6+6124, the first Galactic ultraluminous X-ray pulsar, was observed during its 2017-2018 outburst with AstroSat at both sub- and super-Eddington levels of accretionwith X-ray luminosities of L-X similar to 7x10(37) and 6x10(38) erg s(-1), respectively. Our broad-band timing and spectral observations show that X-ray pulsations at similar to 9.85 s have been detected up to 150 keV when the source was accreting at the super-Eddington level. The pulse profiles are a strong function of both energy and source luminosity, showing a double-peaked profile with pulse fraction increasing from similar to 10 per cent at 1.65 keV to 40-80 per cent at 70 keV. The continuum X-ray spectra are well modelled with a high-energy cut-off power law (Gamma similar to 0.6-0.7) and one or two blackbody components with temperatures of similar to 0.35 and 1.2 keV, depending on the accretion level. No iron line emission is observed at sub-Eddington level, while a broad emission feature at around 6.9 keV is observed at the super-Eddington level, along with a blackbody radius (121-142 km) that indicates the presence of optically thick outflows.
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| 3. |
- Chandra, Sunil, et al.
(författare)
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X-Ray Observations of 1ES 1959+650 in Its High-activity State in 2016-2017 with AstroSat and Swift
- 2021
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 918:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive multifrequency study of the high-frequency-peaked BL Lac object 1ES 1959+650 using data from various facilities during the period 2016-2017, including X-ray data from AstroSat and Swift during the historically high X-ray flux state of the source observed until 2021 February. The unprecedented quality of X-ray data from high-cadence monitoring with AstroSat during 2016-2017 enables us to establish a detailed description of X-ray flares in 1ES 1959+650. The synchrotron peak shifts significantly between different flux states, in a manner consistent with a geometric (changing Doppler factor) interpretation. A time-dependent leptonic diffusive shock acceleration and radiation transfer model is used to reproduce the spectral energy distributions and X-ray light curves, to provide insight into the particle acceleration during the major activity periods observed in 2016 and 2017. The extensive data of Swift-XRT from 2015 December to 2021 February (exp. = 411.3 ks) reveals a positive correlation between flux and peak position.
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| 4. |
- Majee, Rahul, et al.
(författare)
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Maneuvering the Physical Properties and Spin States To Enhance the Activity of La-Sr-Co-Fe-O Perovskite Oxide Nanoparticles in Electrochemical Water Oxidation
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:7, s. 3342-3350
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite oxides have attracted considerable attention as durable electrocatalysts for metal-air batteries and fuel cells due to their precedence in oxygen electrocatalysis in spite of the complexities involved with their crystal structure, spin states, and physical properties. Here we report optimization of the activity of a model perovskite system La1-xSrxCo1-yFeyO3-delta (LSCF; x = 0.301, y = 0.298, and (delta = 0.05-0.11) toward electrochemical water oxidation (OER) by altering the calcination temperature of the nonaqueous sol-gel synthesized nanoparticles (NPs). Our results show that improved OER activity is the result of a synergism between its morphology, surface area, electrical conductivity, and spin state of the active transition metal site. With an e(g) orbital occupancy of 1.26, the interconnected similar to 90 nm LSCF NPs prepared at 975 degrees C (LSCF-975) outperforms the other distinguishable LSCF morphologies, requiring 440 mV overpotential to achieve 10 mA/cm(2), a performance comparable to the best-performing perovskite oxide electrocatalysts. While the interconnected NP morphology increases the propensity of electronic conduction across crystalline grain boundaries, the morphology-tuned high spin Co3+ ions increases the probability of binding reaction intermediates at the available surface sites. Density functional theory based work function modeling further demonstrates that LSCF-975 is the most favorable OER catalyst among others in terms of a moderate work function and Fermi energy level facilitating the adsorption and desorption of reaction intermediates.
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| 5. |
- Watts, Anna L., et al.
(författare)
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Dense matter with eXTP
- 2019
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Ingår i: Science China Physics, Mechanics & Astronomy. - : Science Press. - 1674-7348 .- 1869-1927. ; 62:2
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Forskningsöversikt (refereegranskat)abstract
- In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020s.
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