| 1. |
- Björling, Alexander, et al.
(författare)
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Chemical Limits on X-ray Nanobeam Studies in Water
- 2023
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Ingår i: Journal of Physical Chemistry C. - 1932-7447. ; 127:28, s. 13877-13885
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Tidskriftsartikel (refereegranskat)abstract
- Operando X-ray studies of chemical reactions have gained increasing interest lately, fueled by the emergence of a new generation of powerful focused X-ray sources. Although it is well known that ionizing radiation causes damage to samples via radical chemistry, this effect is often overlooked in studies of working devices or catalysts where intense focused beams are used as nanoscale probes. Here, we show how an X-ray nanobeam directly causes a phase transition in shape-controlled Pd nanoparticles and that a large oxidative potential must be applied to counteract the effect. In addition, we present a chemical reaction-diffusion model that offers a plausible qualitative explanation of the observations, and which also suggests that prohibitive concentrations of reactive species will arise under any focused X-ray probe, calling into question the validity of these methods as applied to aqueous chemical and catalytic systems.
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| 2. |
- Björling, Alexander, et al.
(författare)
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Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline
- 2019
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 26, s. 1830-1834
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure-reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provides three-dimensional lattice strain fields from which surface reactivity maps can be inferred. However, all experiments published so far have investigated particles an order of magnitude larger than those used in practical applications. Studying smaller particles quickly becomes demanding as the diffracted intensity falls. Here, in situ nanodiffraction data from 60 nm Au nanoparticles under electrochemical control collected at the hard X-ray nanoprobe beamline of MAX IV, NanoMAX, are presented. Two-dimensional image reconstructions of these particles are produced, and it is estimated that NanoMAX, which is now open for general users, has the requisites for three-dimensional imaging of particles of a size relevant for catalytic applications. This represents the first demonstration of coherent X-ray diffraction experiments performed at a diffraction-limited storage ring, and illustrates the importance of these new sources for experiments where coherence properties become crucial.
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| 3. |
- Björling, Alexander, et al.
(författare)
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Three-Dimensional Coherent Bragg Imaging of Rotating Nanoparticles
- 2020
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 125:24
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Tidskriftsartikel (refereegranskat)abstract
- Bragg coherent diffraction imaging is a powerful strain imaging tool, often limited by beam-induced sample instability for small particles and high power densities. Here, we devise and validate an adapted diffraction volume assembly algorithm, capable of recovering three-dimensional datasets from particles undergoing uncontrolled and unknown rotations. We apply the method to gold nanoparticles which rotate under the influence of a focused coherent x-ray beam, retrieving their three-dimensional shapes and strain fields. The results show that the sample instability problem can be overcome, enabling the use of fourth generation synchrotron sources for Bragg coherent diffraction imaging to their full potential.
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