short communications
Beam-induced redox chemistry in iron oxide nanoparticle dispersions at ESRF–EBS
aInstitute of Crystallography, RWTH Aachen University, Jägerstraße 17–19, Aachen, 52066 Nordrhein-Westfalen, Germany
*Correspondence e-mail: zobel@ifk.rwth-aachen.de
The storage ring upgrade of the European Synchrotron Radiation Facility makes ESRF–EBS the most brilliant high-energy fourth-generation light source, enabling in situ studies with unprecedented time resolution. While radiation damage is commonly associated with degradation of organic matter such as ionic liquids or polymers in the synchrotron beam, this study clearly shows that highly brilliant X-ray beams readily induce structural changes and beam damage in inorganic matter, too. Here, the reduction of Fe3+ to Fe2+ in iron oxide nanoparticles by radicals in the brilliant ESRF–EBS beam, not observed before the upgrade, is reported. Radicals are created due to radiolysis of an EtOH–H2O mixture with low EtOH concentration (∼6 vol%). In light of extended irradiation times during insitu experiments in, for example, battery and catalysis research, beam-induced redox chemistry needs to be understood for proper interpretation of insitu data.
1. Introduction
During the past few decades the ) and mankind is constantly producing orders of magnitudes more photons in smaller and smaller cross sections (Bras et al., 2021). After the Extremely Brilliant Source (EBS) upgrade, the European Synchrotron Radiation Facility (ESRF) now produces an X-ray beam being ∼100 times more brilliant than before (Raimondi, 2016). Increase in comes with a vast increase in experimental possibilities, that enable us to capture faster events than ever (Bras et al., 2021) and to achieve the same time resolution on weakly scattering amorphous samples as before on crystalline ones (Vaughan et al., 2020). Yet, unprecedented comes with higher risk of radiation damage (Bras et al., 2021). In macromolecular crystallography, radiation damage is a big issue that the community has been aware of for many years, constantly working on predicting damage thresholds and developing methods on how to prevent it (Bras et al., 2021; Fourme et al., 2012; Garman, 2010; Holton, 2009). Further, also in other diffraction (Vaselabadi et al., 2016; Hopkins & Thorne, 2016; Neuhold et al., 2012) as well as imaging (Lai et al., 2013; Wang et al., 2009; Beetz & Jacobsen, 2003) and spectroscopy (Rightor et al., 1997; Chidambaram et al., 2001) experiments, X-ray radiation damage was observed on radiation-sensitive, mostly organic, materials and studied for future obviation. On the contrary, inorganic solid materials are not expected to be affected by radiation damage in X-ray scattering experiments, since very high radiation doses [MGy; 1 Grey (Gy) = 1 J kg−1] are needed for beam-induced changes like the creation of interstitial-hole Frenkel-pairs, excited electronic states, phase transitions and induced crystallization (Bras et al., 2021; Tiliks et al., 1991). Yet, recently, organometal halide perovskites, applied in solar cells, were found to suffer from X-ray induced electronic degradation, namely a decrease of the X-ray beam-induced current (XBIC), even though the elemental composition in (XRF) with common operando synchrotron nanoprobe conditions was not found to change (Stuckelberger et al., 2020). Such a material also exhibited a crystalline lead halide degradation phase, caused by iodine migration from the perovskite, in a scanning nano X-ray diffraction experiment (Ferrer Orri et al., 2022). Further, radiation damage under X-ray exposure was studied for inorganic materials (metal alloy, oxide and semiconducting) with X-ray photon spectroscopy (Astley et al., 2022). Changes in the binding energies were identified for all three materials, but due to different reasons, for example of the metal alloy.
of modern synchrotron light sources has increased a lot (Raimondi, 2016Here, we report on beam-induced changes in redox chemistry in iron oxide and associated changes in lattice parameters, which we observed while measuring total scattering on iron oxide nanoparticles (IONPs) dispersed in ethanol–water (EtOH–H2O) mixture with low ethanol (∼6 vol%) concentration at ID31 ESRF–EBS with high-energy X-rays (65 keV).
Redox chemistry is at the heart of the working principle of electrochemical and various catalytic processes. The number of in situ and operando experiments in these fields has risen rapidly because of the unprecedented time-resolution, enabling insight into structural details of, for instance, heterogeneous catalysts dispersed in liquid electrolytes in fuel cells (Chattot et al., 2021; Martens et al., 2021). Given the Fe3+ → Fe2+ beam-induced reduction in IONPs within only 12 s of exposure, what does happen to nanostructured, often multivalent, metal oxides exposed over hours during operando experiments?
Many battery materials consist of spinel oxides, thus similar to our IONPs (Choi & Manthiram, 2006; Koga et al., 2013; Manthiram, 2020), and we want to create awareness that charge–discharge processes of batteries could similarly be affected due to radiolysis of the surrounding organics. Further, nanomaterial research and general solvation effects on solid–liquid interfaces may be induced in the future (Roy et al., 2021; Christensen et al., 2021; Aalling-Frederiksen et al., 2021). Besides direct impact of the radicals on the solid state structure, solvated radicals can massively impact chemical reactions, for instance operando catalysis experiments. Since materials with excited states behave chemically different, we suppose that increased reaction rates (Bras et al., 2021) or unforeseen influences of radiolysis products at solid–liquid or liquid–gas interfaces (Le Caër, 2011; Bras et al., 2021) cannot be excluded. Hence, reaction kinetics of the experiment may be altered in comparison to without beam.
2. Data collection and data treatment
Total scattering measurements were performed at ID15-A at ESRF before the EBS upgrade and at ID31 at ESRF after the EBS upgrade, for IONPs in EtOH–H2O mixture with low EtOH concentration, IONPs in water (only ID31) (for information regarding sample preparation see Section S1 of the supporting information) and water, taken in 1 mm Kapton capillaries. Both beamlines are equipped with a PILATUS3 X CdTe 2M detector (253.7 mm × 288.8 mm sensitive area, 172 µm × 172 µm pixel size). For data processing and treatment, we used the following: for masking Fit2D and for calibration pyFAI-calib2 (Ashiotis et al., 2015), for radial integration xpdtools (https://xpdacq.github.io/xpdtools/), for pair distribution function (PDF) processing PDFgetX3 (Juhás et al., 2013), for PDF modelling DiffPy-CMI (Juhás et al., 2015) and PDFgui (Farrow et al., 2007), and for fitting of I(Q) data IgorPro by WaveMetrics.
2.1. Details on data collection on ID15A – pre-EBS upgrade
Data were taken with an energy of 68 keV (0.1823 Å) and a beam size of about 120 µm × 120 µm [vertical × horizontal (v × h), being a little bit smaller in the vertical] at ID15A before the upgrade. The 10 to 1 × 1011 photons s−1 (see Section S2 of the supporting information). Ten scans of 25 s each were taken on every sample resulting in a total radiation dose of ∼195–390 kGy (see Section S2 of the supporting information for calculation). NIST chromium(III) oxide standard was used for distance calibration and determination of instrumental resolution (Qdamp = 0.0181 Å−1; Qbroad = 0.0185 Å−1).
on the samples was estimated to be 5 × 102.2. Details on data collection on ID31 – after-EBS upgrade
Data were taken with an energy of 65 keV (0.1907 Å) and a beam size of about 100 µm × 300 µm (v × h, ±50 µm) at ID31 after the upgrade. The 14 photons s−1. Ten scans of 6 s each were taken on every sample resulting in a total radiation dose of ∼40000 kGy (see Section S2 of the supporting information for calculation). NIST cerium(IV) oxide standard was used for distance calibration and determination of instrumental resolution (Qdamp = 0.0159 Å−1; Qbroad = 0.0119 Å−1).
on the samples was 1 × 103. Results and discussion
Performing total scattering on IONPs of 7 and 15 nm in diameter, dispersed in an EtOH–H2O mixture with low EtOH concentration (6 vol%) at ESRF–EBS, we observed shifts of the Bragg peaks over the total time of exposure of 60 s, whereby the biggest shift was observed between the first and second scan between 6 and 12 s. Initially, the IONPs feature an inverse spinel structure with a composition close to maghemite (see Section S3 of the supporting information). Fig. 1(a) shows the diffraction pattern of such an IONP dispersion in the Q-range of 1–5 Å−1 in comparison with that of water. The diffraction patterns are similar, yet the first sharp diffraction peak (FSDP) of the dispersion is broadened and slightly shifted to lower Q-values due to the low amount of EtOH (∼6 vol%; for more information about the EtOH content see Section S4 of the supporting information). The Bragg peaks of the IONPs are visible on top of the broad diffraction from the solvent. In Fig. 1(b) the ten scans taken successively at ID31 after the EBS upgrade are shown in the Q-range of the (333) and (440) Bragg reflexes between 3.7 and 4.5 Å−1, for one exemplary dispersion of IONPs in EtOH–H2O mixture with low EtOH concentration (ID31-1-EtOH–H2O). Evidently, both peaks shift to lower Q-values after the first scan. This becomes even clearer in the inset which shows the (440) Bragg reflex for scan 1, 3 and 10 only, corrected for the water background. The Bragg peaks of the same IONPs dispersed in solely water (ID31-1-H2O) did not shift – see Fig. 1(c). Further, we compared these data with data of samples prepared the same way taken at ID15-A ESRF before the EBS upgrade, thus with lower per irradiated volume, and consequently resulting in lower total radiation dose despite the smaller beam size and longer exposure time (cf. Section S2 of the supporting information). In this case, too, no peak shift of the IONP Bragg peaks over time could be observed – see Fig. 1(d) (shown for ID15-A-1-EtOH–H2O).
We proved the reproducibility of the shift of Bragg peaks in EtOH–H2O mixtures after the upgrade (case 1) and its lack in only H2O after the upgrade (case 2) and the lack in EtOH–H2O mixtures before the upgrade (case 3), for several samples each. In order to quantify the shift and make sure it is bigger than the uncertainty in instrumental resolution, three scans (1, 3 and 10) of two samples of each of the three cases were investigated in more detail. For those scans a Gaussian function was fitted to the (440) reflex in I(Q) data (see Section S5 of the supporting information). Since a shift to lower Q-values is associated with a lattice expansion, this lattice expansion was also confirmed and quantified by PDF fits on the differential-PDFs (d-PDF, IONP dispersion minus water background) (see Section S6 of the supporting information). The results of both evaluations are listed in Table 1 in comparison with the total applied radiation dose, clearly showing the correlation of radiation dose and Bragg peak shift.
|
When water is irradiated with ; Zhang et al., 2012). Thereby, many different species are formed, such as hydrated electrons, dihydrogen and hydrogen peroxide molecules, oxonium and hydroxyl ions, as well as hydroxyl radicals and hydrogen atoms. Hydrated electrons and hydrogen are strong reducing agents, which are known to readily reduce dissolved metal ions to their lower in contrast to the hydroxyl radical, which is oxidative (Le Caër, 2011). are known to be scavengers for the oxidative hydroxyl radical (Simic et al., 1969; Zhang et al., 2012; Yamaguchi et al., 2016). By abstraction of hydrogen from the alcohol, the oxidative hydroxyl radical is scavenged by the alcohol, and thereby organic reducing radicals are evolving (Yamaguchi et al., 2016; Zhang et al., 2012). Moreover, upon radiation with X-rays, ethanol can also be oxidized to acetaldehyde via the production of two electrons and two protons (Yamaguchi et al., 2016). Consequently, in a mixture of water and alcohol a reducing environment for chemical reactions is created upon irradiation with For instance, graphene oxide can be reduced to graphene in such a reducing medium with comparable alcohol content (Zhang et al., 2012). Hence, we are convinced that in our case the non-stochiometric (mostly Fe3+containing) IONPs are reduced to magnetite. Magnetite crystallizes in the inverse spinel structure, with O2− anions forming a cubic close packing, Fe3+ ions occupying the tetrahedral sites and a 1:1 mixture of Fe2+ and Fe3+ ions on the octahedral sites (Cervellino et al., 2014). Magnetite nanoparticles stored in air are fully or partially oxidized to maghemite over time, by creation of vacancies on the octahedral sites accompanied by a lattice contraction (Cervellino et al., 2014; Sidhu et al., 1977). In maghemite (γ-Fe2O3) all of the initial one-third of Fe2+ was oxidized to Fe3+, and thus the number of vacancies is maximal. These vacancies can either be randomly distributed on the octahedral sites or vacancy ordering can exist, lowering the symmetry of the structure (Cervellino et al., 2014). In our case in the synchrotron beam, in the reducing medium created upon irradiation with the highly brilliant X-rays, the opposite reaction is taking place: parts of the Fe3+ ions are reduced to Fe2+ whereby the vacancies are filled again, and the lattice is expanding, due to the bigger ionic radius of Fe2+ in comparison with Fe3+ (Sidhu et al., 1977). Since no other iron source besides the IONPs is present, this reduction will most likely be accompanied by the release of oxygen from the for providing charge balance. For full conversion from maghemite to magnetite the release would amount to ∼11% of the initial oxygen content of the IONPs. Oxygen present at the IONP surface and in the dispersion could then also be involved in reactions with the evolving radicals. The process is schematically shown in Fig. 2. This assumption matches the experimental observations very well, since at first the Bragg peaks shift from first to second scan, strongly. Then, an equilibrium state seems to be reached, matching the fact that all vacancies are filled at some point. Further, the radiation dose per second (see Section S2 of the supporting information) in our experiments has been higher than the total radiation doses reported in studies which aimed at synthesizing inorganic nanoparticles via radiolysis by deliberate exposure of metal ion precursor solutions to strong (Čubová & Čuba, 2020). We exclude that the expansion is for two reasons: in the case of the IONPs in water only should be likewise influenced considering similar further, the increase of the lattice parameter of ∼0.03 Å would be caused at temperatures way above the boiling point of water (Bayer, 1972; Petric & Ling, 2007; Levy et al., 2004), but no evaporation of the solvent is observed in the I(Q) scans.
like radioactive nuclei, beams of charged particles and X-rays with a photon energy >100 eV, radiolysis of water takes place (Le Caër, 20114. Conclusion
In summary, we have observed beam-induced structural changes in iron oxide nanoparticles created by radiolysis during total scattering experiments on nanoparticle dispersions in an EtOH–H2O mixture with low EtOH concentration. The iron oxide nanoparticles were reduced from an almost maghemite (mainly Fe3+ containing) composition to magnetite in the highly brilliant synchrotron beam at ID31, ESRF–EBS. This is, to our knowledge, the first showcase of beam-induced damage in inorganic solids after the ESRF upgrade. Given its nature in redox chemistry and evolving radicals in solution, we expect this study to be highly relevant to a range of fields including in situ studies in catalysis and energy applications such as fuel cell or battery research. Time-dependent sample-specific changes need to be questioned in light of possibly radiolysis-induced redox chemistry.
5. Related literature
The following references, not cited in the main body of the paper, have been cited in the supporting information: Bondaz et al. (2020); Caruntu et al. (2004); Cooper et al. (2020); Greaves (1983); Qu et al. (2011); Thomä et al. (2019).
Supporting information
Sections S1 to S6, including Tables S1 to S5 and Figures S1 to S4. DOI: https://doi.org/10.1107/S1600577522011523/fv5157sup1.pdf
Acknowledgements
We gratefully acknowledge beam time at the European Synchrotron Radiation Facility granted from proposals CH5509 and CH6070. We thank our local contacts from beamline ID15-A and ID31, Gavin Vaughan and Marta Mirolo, for the assistance in operating the beamlines, as well as Jakub Drnec, Veijo Honkimäki and Andreas Magerl for discussions. Open access funding enabled and organized by Projekt DEAL.
Funding information
The following funding is acknowledged: European Synchrotron Radiation Facility (grant No. CH5509); European Synchrotron Radiation Facility (grant No. CH6070).
References
Aalling-Frederiksen, O., Juelsholt, M., Anker, A. S. & Jensen, K. M. O. (2021). Nanoscale, 13, 8087–8097. Web of Science CAS PubMed Google Scholar
Ashiotis, G., Deschildre, A., Nawaz, Z., Wright, J. P., Karkoulis, D., Picca, F. E. & Kieffer, J. (2015). J. Appl. Cryst. 48, 510–519. Web of Science CrossRef CAS IUCr Journals Google Scholar
Astley, S., Hu, D., Hazeldine, K., Ash, J., Cross, R. E., Cooil, S., Allen, M. W., Evans, J., James, K., Venturini, F., Grinter, D. C., Ferrer, P., Arrigo, R., Held, G., Williams, G. T. & Evans, D. A. (2022). Faraday Discuss. 236, 191–204. Web of Science CrossRef CAS PubMed Google Scholar
Bayer, G. (1972). Thermochim. Acta, 3, 421–426. CrossRef CAS Google Scholar
Beetz, T. & Jacobsen, C. (2003). J. Synchrotron Rad. 10, 280–283. Web of Science CrossRef CAS IUCr Journals Google Scholar
Bondaz, L., Fontaine, P., Muller, F., Pantoustier, N., Perrin, P., Morfin, I., Goldmann, M. & Cousin, F. (2020). Langmuir, 36, 6132–6144. Web of Science CrossRef CAS PubMed Google Scholar
Bras, W., Myles, D. A. A. & Felici, R. (2021). J. Phys. Condens. Matter, 33, 423002. Web of Science CrossRef Google Scholar
Caruntu, D., Caruntu, G., Chen, Y., O'Connor, C. J., Goloverda, G. & Kolesnichenko, V. L. (2004). Chem. Mater. 16, 5527–5534. Web of Science CrossRef CAS Google Scholar
Cervellino, A., Frison, R., Cernuto, G., Guagliardi, A. & Masciocchi, N. (2014). J. Appl. Cryst. 47, 1755–1761. Web of Science CrossRef CAS IUCr Journals Google Scholar
Chattot, R., Martens, I., Mirolo, M., Ronovsky, M., Russello, F., Isern, H., Braesch, G., Hornberger, E., Strasser, P., Sibert, E., Chatenet, M., Honkimäki, V. & Drnec, J. (2021). J. Am. Chem. Soc. 143, 17068–17078. Web of Science CrossRef CAS PubMed Google Scholar
Chidambaram, D., Halada, G. P. & Clayton, C. R. (2001). Appl. Surf. Sci. 181, 283–295. Web of Science CrossRef CAS Google Scholar
Choi, W. & Manthiram, A. (2006). J. Electrochem. Soc. 153, A1760. Web of Science CrossRef Google Scholar
Christensen, R. S., Klove, M., Roelsgaard, M., Sommer, S. & Iversen, B. B. (2021). Nanoscale 13, 12711–12719. Web of Science CrossRef CAS PubMed Google Scholar
Cooper, S. R., Candler, R. O., Cosby, A. G., Johnson, D. W., Jensen, K. M. O. & Hutchison, J. E. (2020). ACS Nano, 14, 5480–5490. Web of Science CrossRef CAS PubMed Google Scholar
Čubová, K. & Čuba, V. (2020). Radiat. Phys. Chem. 169, 108774. Google Scholar
Farrow, C. L., Juhas, P., Liu, J. W., Bryndin, D., Božin, E. S., Bloch, J., Proffen, T. & Billinge, S. J. (2007). J. Phys. Condens. Matter, 19, 335219. Web of Science CrossRef PubMed Google Scholar
Ferrer Orri, J., Doherty, T. A. S., Johnstone, D., Collins, S. M., Simons, H., Midgley, P. A., Ducati, C. & Stranks, S. D. (2022). Adv. Mater. 34, e2200383. Web of Science CrossRef PubMed Google Scholar
Fourme, R., Honkimäki, V., Girard, E., Medjoubi, K., Dhaussy, A.-C. & Kahn, R. (2012). J. Appl. Cryst. 45, 652–661. Web of Science CrossRef CAS IUCr Journals Google Scholar
Garman, E. F. (2010). Acta Cryst. D66, 339–351. Web of Science CrossRef CAS IUCr Journals Google Scholar
Greaves, C. (1983). J. Solid State Chem. 49, 325–333. CrossRef ICSD CAS Web of Science Google Scholar
Holton, J. M. (2009). J. Synchrotron Rad. 16, 133–142. Web of Science CrossRef CAS IUCr Journals Google Scholar
Hopkins, J. B. & Thorne, R. E. (2016). J. Appl. Cryst. 49, 880–890. Web of Science CrossRef CAS IUCr Journals Google Scholar
Juhás, P., Davis, T., Farrow, C. L. & Billinge, S. J. L. (2013). J. Appl. Cryst. 46, 560–566. Web of Science CrossRef IUCr Journals Google Scholar
Juhás, P., Farrow, C., Yang, X., Knox, K. & Billinge, S. (2015). Acta Cryst. A71, 562–568. Web of Science CrossRef IUCr Journals Google Scholar
Koga, H., Croguennec, L., Ménétrier, M., Douhil, K., Belin, S., Bourgeois, L., Suard, E., Weill, F. & Delmas, C. (2013). J. Electrochem. Soc. 160, A786–A792. Web of Science CrossRef CAS Google Scholar
Lai, B., Nelson, J., Yang, Y., Misra, S., Andrews, J. C., Cui, Y. & Toney, M. F. (2013). Proc. SPIE, 8851, 88510B. CrossRef Google Scholar
Le Caër, S. (2011). Water, 3, 235–253. Google Scholar
Levy, D., Artioli, G. & Dapiaggi, M. (2004). J. Solid State Chem. 177, 1713–1716. Web of Science CrossRef CAS Google Scholar
Manthiram, A. (2020). Nat. Commun. 11, 1550. Web of Science CrossRef PubMed Google Scholar
Martens, I., Chattot, R., Wiegmann, T., Fuchs, T., Magnussen, O. M., Dubau, L., Maillard, F. & Drnec, J. (2021). J. Phys. Energy, 3, 031003. Web of Science CrossRef Google Scholar
Momma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272–1276. Web of Science CrossRef CAS IUCr Journals Google Scholar
Neuhold, A., Novák, J., Flesch, H. G., Moser, A., Djuric, T., Grodd, L., Grigorian, S., Pietsch, U. & Resel, R. (2012). Nucl. Instrum. Methods Phys. Res. B, 284, 64–68. Web of Science CrossRef CAS Google Scholar
Petric, A. & Ling, H. (2007). J. Am. Ceram. Soc. 90, 1515–1520. Web of Science CrossRef CAS Google Scholar
Qu, H., Caruntu, D., Liu, H. & O'Connor, C. J. (2011). Langmuir, 27, 2271–2278. Web of Science CrossRef CAS PubMed Google Scholar
Raimondi, P. (2016). Synchrotron Radiat. News, 29(6), 8–15. CrossRef Google Scholar
Rightor, E. G., Hitchcock, A. P., Ade, H., Leapman, R. D., Urquhart, S. G., Smith, A. P., Mitchell, G., Fischer, D., Shin, H. J. & Warwick, T. (1997). J. Phys. Chem. B, 101, 1950–1960. CrossRef CAS Web of Science Google Scholar
Roy, S., Sharma, S., Karunaratne, W. V., Wu, F., Gakhar, R., Maltsev, D. S., Halstenberg, P., Abeykoon, M., Gill, S. K., Zhang, Y., Mahurin, S. M., Dai, S., Bryantsev, V. S., Margulis, C. J. & Ivanov, A. S. (2021). Chem. Sci. 12, 8026–8035. Web of Science CrossRef CAS PubMed Google Scholar
Sidhu, P. S., Gilkes, R. J. & Posner, A. M. (1977). J. Inorg. Nucl. Chem. 39, 1953–1958. CrossRef CAS Web of Science Google Scholar
Simic, M., Neta, P. & Hayon, E. (1969). J. Phys. Chem. 73, 3794–3800. CrossRef CAS Web of Science Google Scholar
Stuckelberger, M. E., Nietzold, T., West, B. M., Luo, Y., Li, X., Werner, J., Niesen, B., Ballif, C., Rose, V., Fenning, D. P. & Bertoni, M. I. (2020). J. Phys. Chem. C, 124, 17949–17956. Web of Science CrossRef CAS Google Scholar
Thomä, S. L. J., Krauss, S. W., Eckardt, M., Chater, P. & Zobel, M. (2019). Nat. Commun. 10, 995. Web of Science PubMed Google Scholar
Tiliks, J. E., Kizane, G. K., Supe, A. A., Abramenkovs, A. A., Tiliks, J. J. & Vasiljev, V. G. (1991). Fusion Eng. Des. 17, 17–20. CrossRef CAS Web of Science Google Scholar
Vaselabadi, S. A., Shakarisaz, D., Ruchhoeft, P., Strzalka, J. & Stein, G. E. (2016). J. Polym. Sci. Part B Polym. Phys. 54, 1074–1086. Web of Science CrossRef CAS Google Scholar
Vaughan, G. B. M., Baker, R., Barret, R., Bonnefoy, J., Buslaps, T., Checchia, S., Duran, D., Fihman, F., Got, P., Kieffer, J., Kimber, S. A. J., Martel, K., Morawe, C., Mottin, D., Papillon, E., Petitdemange, S., Vamvakeros, A., Vieux, J.-P. & Di Michiel, M. (2020). J. Synchrotron Rad. 27, 515–528. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wang, J., Morin, C., Li, L., Hitchcock, A. P., Scholl, A. & Doran, A. (2009). J. Electron Spectrosc. Relat. Phenom. 170, 25–36. Web of Science CrossRef CAS Google Scholar
Yamaguchi, A., Okada, I., Fukuoka, T., Ishihara, M., Sakurai, I. & Utsumi, Y. (2016). J. Nanomaterials, 2016, 1–16. Web of Science CrossRef Google Scholar
Zhang, B., Li, L., Wang, Z., Xie, S., Zhang, Y., Shen, Y., Yu, M., Deng, B., Huang, Q., Fan, C. & Li, J. (2012). J. Mater. Chem. 22, 7775. Web of Science CrossRef Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.