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| 2. |
- de Oliveira, Raphaela, et al.
(författare)
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Water Nanochannels in Ultrathin Clinochlore Phyllosilicate Mineral with Ice-like Behavior
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Ingår i: Journal of Physical Chemistry C. - 1932-7447.
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Tidskriftsartikel (refereegranskat)abstract
- Water is the matrix of life, and its confinement in nanocavities is a central topic from geophysics to nanotribology. Phyllosilicate layered minerals provide natural nanocavities for water due to their capacity to hydrate by confining water molecules in the interlamellar space. However, the hydration of phyllosilicates at the nanoscale is not a fully understood process and depends on the geological specimens. In this work, we report the formation of aqueous nanochannels in the interlamellar space of ultrathin clinochlore phyllosilicate mineral using infrared scattering-type scanning near-field optical microscopy and Kelvin probe force microscopy. We demonstrate that nanoconfinement of water in clinochlore changes the overall mechanical, optical, and dielectric properties of the system. We propose a capacitive model that describes the dielectric response of the aqueous nanochannels. Our model is endorsed by a robust crystal truncation rod analysis of synchrotron X-ray diffraction data. We found that clinochlore termination combines hydrated structures ordered along the c-axis. We also find evidence of ice-like behavior of the water nanoconfined in clinochlore by Fourier-transform infrared spectroscopy. Notably, our work introduces clinochlore as a natural platform for water confinement in two-dimensional systems that can be engineered for several applications in the frontiers of nanotechnology.
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| 3. |
- Hammarberg, Susanna, et al.
(författare)
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Nanoscale X-ray Imaging of Composition and Ferroelastic Domains in Heterostructured Perovskite Nanowires : Implications for Optoelectronic Devices
- 2023
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 6:19, s. 17698-17705
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites (MHPs) have garnered significant interest as promising candidates for nanoscale optoelectronic applications due to their excellent optical properties. Axially heterostructured CsPbBr3-CsPb(Br(1-x)Clx)3 nanowires can be produced by localized anion exchange of pregrown CsPbBr3 nanowires. However, characterizing such heterostructures with sufficient strain and real space resolution is challenging. Here, we use nanofocused scanning X-ray diffraction (XRD) and X-ray fluorescence (XRF) with a 60 nm beam to investigate a heterostructured MHP nanowire as well as a reference CsPbBr3 nanowire. The nano-XRD approach gives spatially resolved maps of composition, lattice spacing, and lattice tilt. Both the reference and exchanged nanowire show signs of diverse types of ferroelastic domains, as revealed by the tilt maps. The chlorinated segment shows an average Cl composition of x = 66 and x = 70% as measured by XRD and XRF, respectively. The XRD measurements give a much more consistent result than the XRF ones. These findings are consistent with photoluminescence measurements, showing x = 73%. The nominally unexchanged segment also has a small concentration of Cl, as observed with all three methods, which we attribute to diffusion after processing. These results highlight the need to prevent such unwanted processes in order to fabricate optoelectronic devices based on MHP heterostructures.
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| 4. |
- Luo, Xiyu, et al.
(författare)
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Effects of local compositional heterogeneity in mixed halide perovskites on blue electroluminescence
- 2024
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Ingår i: Matter. - 2590-2393. ; 7:3, s. 1054-1070
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Tidskriftsartikel (refereegranskat)abstract
- Compositional heterogeneity is commonly observed in mixed bromide/iodide perovskite photoabsorbers, typically with minimal effects on charge carrier recombination and photovoltaic performance. Consistently, it has so far received very limited attention in bromide/chloride-mixed perovskites, which hold particular significance for blue light-emitting diodes. Here, we uncover that even a minor degree of localized halide heterogeneity leads to severe non-radiative losses in mixed bromide/chloride blue perovskite emitters, presenting a stark contrast to general observations in photovoltaics. We not only provide a visualization of the heterogeneity landscape spanning from micro-to sub-microscale but also identify that this issue mainly arises from the initially formed chloride-rich clusters during perovskite nucleation. Our work sheds light on a long-term neglected factor impeding the advancement of blue light-emitting diodes using mixed halide perovskites and provides a practical strategy to mitigate this issue.
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| 5. |
- Marçal, L. A.B., et al.
(författare)
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Structural and chemical properties of anion exchanged CsPb(Br(1−x)Cl x )3 heterostructured perovskite nanowires imaged by nanofocused x-rays
- 2024
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Ingår i: Nanotechnology. - 0957-4484. ; 35:26
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Tidskriftsartikel (refereegranskat)abstract
- Over the last years metal halide perovskites have demonstrated remarkable potential for integration in light emitting devices. Heterostructures allow for tunable bandgap depending on the local anion composition, crucial for optoelectronic devices, but local structural effects of anion exchange in single crystals is not fully understood. Here, we investigate how the anion exchange of CsPbBr3 nanowires fully and locally exposed to HCl vapor affects the local crystal structure, using nanofocused x-rays. We study the nanoscale composition and crystal structure as function of HCl exposure time and demonstrate the correlation of anion exchange with changes in the lattice parameter. The local composition was measured by x-ray fluorescence and x-ray diffraction, with general agreement of both methods but with much less variation using latter. The heterostructured nanowires exhibit unintentional gradients in composition, both axially and radially. Ferroelastic domains are observed for all HCl exposure times, and the magnitude of the lattice tilt at the domain walls scales with the Cl concentration.
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| 6. |
- Yang, Huaiyu, 1984-, et al.
(författare)
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Sandwich crystals of butyl paraben
- 2014
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 16:37, s. 8863-8873
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Tidskriftsartikel (refereegranskat)abstract
- Butyl paraben crystals having a porous layer in between two solid non-porous layers have been produced by cooling crystallization in mixtures of ethanol and water. The outer layers are transparent and fully crystalline, while the middle layer appears to be polycrystalline and is full of pores of various dimensions, down to below 0.1 mu m diameters. The thickness of the porous layer reaches about 40% of the whole crystal. The crystals contain one polymorph only and appear to be essentially fully crystalline. They are stable for more than a year when stored on the shelf at room temperature. When the crystals dissolve, the porous layer dissolves faster, leaving the outer layers for slower dissolution. The sandwich crystals are easily cleaved through the middle layer parallel to the (100) plane. This type of sandwich crystals may provide new useful properties to pharmaceutical solids, e. g. larger specific surface area, higher dissolution rates and improved compaction properties.
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