# Deciphering the nature of secondary Ag S species in soils polluted with Ag nanoparticles

Ana Elena Pradas del Real, Hiram Castillo-Michel, Ralf Kaegi, Juan Reyes-Herrera, Remi Tucoulou, Geraldine Sarret

## ► To cite this version:

Ana Elena Pradas del Real, Hiram Castillo-Michel, Ralf Kaegi, Juan Reyes-Herrera, Remi Tucoulou, et al.. Deciphering the nature of secondary Ag S species in soils polluted with Ag nanoparticles. Spectrochimica Acta Part B: Atomic Spectroscopy, 2025, 231, pp.107258. 10.1016/j.sab.2025.107258. hal-05371001

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# Deciphering the nature of secondary Ag—S species in soils polluted with Ag nanoparticles

Ana Elena Pradas del Real<sup>a,∗</sup>, Hiram Castillo-Michel<sup>b</sup>, Ralf Kaegi<sup>c</sup>, Juan Reyes-Herrera<sup>b</sup>, Remi Tucoulou<sup>b</sup>, Geraldine Sarret<sup>a</sup>

## ARTICLE INFO

### Keywords:

- Silver nanoparticles

- Soil

- X-ray absorption near edge structure (XANES)

- spectroscopy

- Nano X-ray fluorescence (nXRF)

## ABSTRACT

Ag₂S nanoparticles (Ag₂S-NPs) are the main silver species in sewage sludge and soils polluted with silver nanoparticles (AgNPs). Uncertainties about Ag⁺ release and nano-Ag₂S toxicity prompted us to further investigate Ag speciation and distribution under realistic conditions. In a previous study we found by bulk X-ray absorption spectroscopy (XAS) that besides Ag₂S, a secondary Ag—S species was present in sewage sludge and soils. This species accounted for 24–36 % of total silver. The objective of the present work was to investigate the nature of this Ag—S species. A combination of X-ray absorption near edge structure (XANES) spectroscopy at Ag K and L₁₁ edges at micro and nano resolutions and of S K-edge micro XANES were used. Nano X-ray Fluorescence (nXRF) was used to investigate the nanoparticle size distribution and to evaluate the presence of mixed metal sulfides. We identified the secondary Ag—S species as Ag bound to thiol groups of organic matter (Ag-thiolate). It was present around the Ag₂S-NPs, and likely resulted from the complexation of Ag⁺ by thiol groups of soil organic matter. Ag₂S-NPs displayed a variety of sizes, with 10 % to 40 % of particles below 100 nm. Mixed metal sulfides were also present. This study improves our understanding of the fate of Ag-NPs in terrestrial environments, highlights the potential reactivity of Ag₂S-NPs in soils, and shows the primary role of soil organic matter as a sink for released Ag⁺. This multi-scale, high-resolution approach represents a novel and powerful methodology for studying nanoparticle behavior in complex environmental matrices.

## 1. Introduction

Silver nanoparticles (AgNPs) are increasingly used in consumer and medical products due of their broad spectrum antibacterial properties [1]. In the EU, it is estimated that 270 tons of engineered Ag-NPs enter wastewater treatment plants every year. 255 tons (94 %) of Ag are retained in sewage sludge, and 140 tons of Ag present in this material (54 % of the sewage sludge) is applied in agricultural land [2]. More recent models confirmed that the application of sewage sludge in agricultural land represents the largest input of AgNPs to terrestrial ecosystems [3,4]. AgNPs undergo sulfidation during the wastewater treatment, so in sewage sludge Ag is predominantly present as Ag₂S-NPs [5–7]. Bulk Ag₂S has an extremely low solubility ($K_{sp} = 5.92 \times 10^{-51}$ [8]. Hence, sulfidation of Ag-NPs causes a decrease in their toxicity compared to pristine AgNPs [1]. However, the impact of Ag-NPs may have been underestimated since most studies were realized using fresh

Ag₂S-NPs instead of AgNPs subjected to wastewater treatment process [9]. It is essential to understand the transformation and fate of Ag₂S-NPs in soils in order to fully evaluate the environmental impact of Ag-NPs.

Several studies, showing an impact of Ag₂S-NPs on plants [10,11] and on soil microbial activities [12], suggest that even after sulfidation, Ag remains partly bioavailable. This hypothesis is supported by studies showing a leaching of Ag in biosolid-amended soils [13], and a bio-accumulation of Ag in snails in soils amended with sewage sludge [14]. The presence of bioavailable Ag in these sludge amended soils can have two origins. The first one is the weathering of Ag₂S-NPs. Various factors including irradiation by sunlight and interactions with iron oxides, Mn oxides, chlorine, thiosulfate, ozone and thiol groups of organic matters may alter Ag₂S-NPs through redox and non redox reactions, and lead to the release of Ag + ([15];[16]; [17–19]). The second possible origin of bioavailable Ag in sewage sludge is the presence of minor Ag species resulting from incomplete sulfidation of Ag⁺ released from the

<footnote><sup>a</sup> Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, Univ. G. Eiffel, ISTerre, Grenoble, France</footnote>

<footnote><sup>b</sup> ESRF, The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France</footnote>

<footnote><sup>c</sup> Eawag, Particle Laboratory, Dübendorf 8600, Switzerland</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: ana.pradas-del-real@univ-grenoble-alpes.fr (A.E. Pradas del Real).</footnote>
oxidative dissolution of AgNPs during the wastewater treatment. The nature of these minor species is debated. Some authors identified Ag-glutathione, Ag(0), Ag₃PO₄ and Ag sorbed to ferrihydrite, accounting for less than 15 % of total Ag [5,20,21] while in our previous study, we identified amorphous Ag₂S and/or organic Ag-thiolate (called Ag-thiol in the previous work) as minor Ag species, accounting for 24 % to 36 % of total Ag [22]. Bulk X-ray absorption spectroscopy (XAS), used in these studies at the Ag edge, is weakly sensitive to minor Ag species. A possible way to overcome this limitation is to use microfocused XAS. In addition, targeting not only Ag, but also S is a way to get more information on Ag speciation.

In the present study, we investigated the potential of combined Ag and S microXANES analyses to better characterize Ag speciation and Ag—S interactions. The full XAS mapping mode, which allows to extract average x-ray absorption spectra from a whole area as well as spectra from selected points of interest (corresponding to individual pixels), was used. We show the potential of this mode to characterize weathering gradients around particles. We also used µ and nanoXRF to obtain information on the particle size and on the presence of other metal sulfides, including mixed metal sulfides.

## 2. Material and methods

### 2.1. Sewage sludge production and pot experiment

Production and characterization of the sludge, characterization of the soil and details about the pot experiment are given in [22]. Briefly, PVP-AgNPs were continuously spiked into a pilot waste water treatment plant (WWTP) at EAWAG (Dübendorf, Switzerland) to produce a contaminated sludge (400 mg Ag kg⁻¹), referred to as “High dose sludge” in Pradas del Real et al. [22]. A loamy agricultural soil (Luvisol, WRB, 2006, La Côte Saint-André, Isère, France) was mixed with the high dose sewage sludge in a 1/10 ratio, and transferred to ¼ L pots. Selected pots were kept unplanted, and others were planted with rape (*Brassica napus*) and wheat (*Triticum aestivum*). After 4 weeks of growth, roots colonized the whole pots, so soils collected in planted pots were considered as rhizospheric soils. The speciation of Ag in the sludge and amended soils was studied by bulk Ag K-edge EXAFS spectroscopy, and the Ag distribution in unperturbed samples (20 µm sections fixed in epoxy resin) of the rape planted soil was studied by nano XRF [22]. In the present study we further investigate unperturbed samples of sludge-amended soils planted with rape and wheat, and without plant. The techniques used include µXRF, Ag L-edge µXANES, S K-edge µXANES, nanoXRF and Ag K-edge nanoXANES. µXAS and nanoXANES were acquired in full XANES mapping mode, as explained below.

### 2.2. Ag speciation by Ag L-edge full micro XANES mapping (FXAS)

µ-XRF and Ag L₁₁₁-edge full micro XANES mapping (FXAS) [23] was performed on the scanning X-ray microscope on ID21 beamline at the ESRF (The European Synchrotron Radiation Facility) at room temperature. Focusing was realized using a Kirkpatrick-Baez mirror system. At 3.45 keV photon flux was 2.2·10¹⁰ ph·s⁻¹. Detectors included a photodiode for measure the incoming photon flux (IO) and a silicon drift detector (SDD, X-flash Bruker 80 mm² active area) for the emitted X-ray fluorescence. Beam size was 0.4 (vertical) x 0.7 (horizontal) µm². Samples were explored by µXRF using 3 µm step size and 100 ms dwell time. In localized Ag spots, full micro XANES maps were recorded with 0.5 µm step and 100 ms dwell time using 3 eV energy steps from 3.32 to 3.34 keV, 0.5 eV from 3.34 to 3.38 keV, and 1 eV from 3.34 to 3.40 keV. Alignment of maps and extraction of µXANES spectra was performed as described in [24].

### 2.3. Ag speciation by Ag K-edge full nano XANES mapping

Ag K-edge full nano XANES mapping was performed on the hard X-

ray nanoprobe ID16b [25] at the ESRF. A focused X-ray beam (46 (vertical) × 62 (horizontal) nm²) was produced by Kirkpatrick-Baez mirrors providing a photon flux of 2.9·10¹⁰ ph·s⁻¹. Two fluorescence detectors (three-element SDD arrays from SGX Sensortech) were used. Areas of interest were first identified by nanoXRF (Ag K line) mapping. In a second step, XANES mapping was performed on specific regions with a pixel size of 50 × 50 nm², and a dwell time of 100 ms using 3 eV step from 25.455 to 25.485, 1 eV from 25.485 to 25.855 and 2 eV from 25.585 to 25.625 eV. Then, the maps were all slightly re-aligned with respect to each other and nanoXANES spectra were extracted from each pixel as described below. Only rape rhizosphere was investigated by this technique.

### 2.4. S speciation by full micro XANES mapping

µ-XRF and S K-edge full micro XANES mapping were performed on ID21 (ESRF) as described for Ag. Photon flux was 3.35·10⁹ ph·s⁻¹ at 2.5 keV and beam size was 0.4 (vertical) x 0.7 (horizontal) µm². XRF maps were performed at 2.5 keV to record total S fluorescence and at 2.474 keV to select the fluorescence produced by SH and S—S species which allowed to localize Ag₂S aggregates. S K-edge µXANES data were collected in FXAS mode with 0.5 µm step size and 100 ms dwell time using 3 eV energy steps from 2.450 to 2.462 keV, 0.3 eV from 2.462 to 2.474 keV, and 1 eV from 2.474 to 2.494 keV. Then, maps were aligned and µXANES spectra were extracted as described above.

### 2.5. µ and nano-XRF and XANES data curation

All fluorescence maps presented in this study were obtained using Pymca after fitting the XRF spectrum of each pixel [26]. XRF images recorded using the different regions of interests (Ag Lα, Ag Kα, S Kα) were corrected by dead time and IO and aligned using elastix [27].

XANES spectra were normalized and treated by linear combination fitting (LCF) using ATHENA software [28] using different XANES reference databases (Fig. S1). Ag L₁₁₁ edge XANES reference spectra were collected in previous studies in unfocused mode [10,29,30]. We have the spectra of two different Ag(I)-thiolate complexes (Ag—glutathione and Ag diethyldithiocarbamate (C₅H₁₀AgNS₂, Ag-DEDTC)). The references included in the LCFs were: natural macrocrystalline Ag₂S (acanthite), amorphous Ag₂S and Ag-DEDTC (Ag-thiolate) (Fig. 1.a). Ag K-edge reference spectra were previously recorded [22,29] and the following were included in the LCF's: natural macrocrystalline Ag₂S (acanthite), amorphous Ag₂S and Ag-DEDTC (Ag-thiolate) (Fig. 1.b). S K-edge reference spectra were downloaded from the S XANES spectra database of ID21 (https://www.esrf.fr/home/UsersAndScience/Experiments/XNP/ID21/php.html). Tested references included: gypsum (sulfate), anthraquinone sulfonic acid, potassium sulfite, L-cysteine (thiol), galena (PbS), zinc sulfide (ZnS) and troilite (FeS). Additionally, for this experiment the spectra of natural macrocrystalline Ag₂S (acanthite) was also recorded. The references selected for the LCF's were: gypsum (sulfate), anthraquinone sulfonic acid, potassium sulfite, L-cysteine (thiol) and macrocrystalline Ag₂S (acanthite) (Fig. 1.c).

### 2.6. nanoXRF mapping and particle size distribution

Nano XRF maps were recorded on ID16b (ESRF) as described above but using pink mode to reach a flux of 2.6·10¹¹ ph·s⁻¹. Beam size was 48 (vertical) × 60 (horizontal) nm². Maps were recorded using 50 nm step size and 100 ms dwell time. The analysis of the particle size distribution was performed using ImageJ [31] based on Feret diameter as described in [24]. The maps for Ag, Cu and Zn were compared in order to evaluate the presence of mixed sulfides.
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** XANES reference spectra at the a) Ag LIII-edge, b) Ag K-edge and c) S K-edge.</figcaption></figure>

### 3. Results and discussion

#### 3.1. Ag₂S and the secondary Ag–S species are associated at the micro and nanoscale

µXRF elemental maps were collected from soil without plant and from soil planted with wheat and rape. The Ag speciation in selected regions of the maps was studied by Ag L<sub>III</sub>-edge µXANES spectroscopy. For rape rhizosphere soil, µXRF maps, µXANES spectra and results of linear combination fitting (LCF) are shown in Fig. 2a and c. Ag₂S macrocrystalline was the main Ag species (70–85 %). Our data suggests a secondary Ag–S species corresponding to Ag-thiolate and/or amorphous Ag₂S. The two latter forms of Ag have very similar spectra but differ from the spectrum of nanoAg₂S and macrocrystalline Ag₂S (Fig. S1a). We investigated Ag speciation at higher spatial resolution by recording Ag K-edge nanoXANES in FXAS mode. Given the long acquisition time, we only investigated three Ag aggregates in rape rhizosphere soil (Fig. 2 b and d). In aggregate 1 and 2, smaller than 1 µm in diameter (around 650 nm × 400 nm and 600 nm × 600 nm respectively), we found a mixture of Ag₂S macrocrystalline (88 and 86 %) and Ag-thiolate or amorphous Ag₂S (13–16 %). In particle 3, slightly larger than the others (1050 nm × 600 nm), we found 100 % of Ag₂S macrocrystalline. The analysis of the other matrices (soil without plant and wheat rhizosphere) by µXRF and Ag L-egde µXAS showed similar results, with Ag₂S macrocrystalline as major species (59–74 %) and amorphous Ag₂S and/or Ag-thiolate as secondary species (32–42 %) (Fig. S2).

We have shown previously by bulk Ag K-edge EXAFS spectroscopy the presence of macrocrystalline Ag₂S as major species and of amorphous Ag₂S and/or Ag-thiolate as a minor species. The present results show the co-occurrence, at the micrometer and submicrometer scale, of macrocrystalline Ag₂S as major species and of amorphous Ag₂S and/or Ag-thiolate as a minor species.

#### 3.2. S speciation

With the aim to better identify the nature of Ag–S species present in the amended soils, we performed S K-edge µXANES spectroscopy in FXAS

<figure><img src="image_4.png" /><figcaption>**Fig. 2.** a) Tricolor µXRF map of a soil thin section from the rape rhizosphere, collected at 3450 eV, showing the distribution of Ag(red), S (green) and Si (blue). Red squares show the areas where Ag L<sub>III</sub> edge µXANES spectra were collected in mapping mode. The pink square is the area selected for nanoXRF and nanoXANES. b) nanoXRF map collected at 25650 eV showing the Ag distribution in temperature scale, and the three particles where Ag K edge nanoXANES spectra were collected in mapping mode. c). Top: Ag L<sub>III</sub> µXANES spectra (solid lines) and LCFs (dashed lines) for the red squares in a). Bottom: Average and standard deviations of Ag species distribution obtained from these three LCFs, c). Bottom: nano Ag K-edge XANES spectra (solid lines) and LCFs (dashed lines) for the points 1 2 and 3 in b). Bottom: Average and standard deviations of Ag species distribution obtained from these three LCFs. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)</figcaption></figure>
mode. Fig. 1c shows the S K-edge XANES spectra of references with different oxidation states (sulfide (Ag₂S), thiol, sulfite, sulfonic acid and sulfate). Results from rape planted soil are presented in Fig. 3. Fig. S3 shows results for non planted soil and wheat rhizosphere. LCFs were obtained with a mixture of reduced and oxidized S species, but the major species were the reduced forms, Ag₂S and thiol. We tested the use of other metal sulfides in the LCF's (Fig. S4), the best results were obtained using Ag₂S, confirming that the analyzed particles corresponded with Ag₂S nanoparticles identified with Ag K and L edges analysis. Fig. 4 shows the S K-edge XANES spectra extracted from the different intensity regions (from red to blue in a temperature scale) of the square 2 shown in Fig. 3. This figure shows a decrease in the proportion of Ag₂S from high to low intensity areas, accompanied by an increase in the proportion of thiol and or more oxidized species. Similar results were found on the other analyzed particles suggesting the presence of a corona enriched with thiol species around Ag₂S particles. These results indicate that the secondary Ag—S species found in spectroscopic studies at Ag K and L₃₃ edges correspond to Ag-thiol species, and it likely comes from the weathering of Ag₂S, release of Ag⁺ and binding to thiol groups of organic matter.

### 3.3. Ag particle size distribution

The Ag distribution was previously studied by nanoXRF in the rape rhizosphere. A distribution of sizes, from micro to nano sized particles to diffuse Ag, corresponding to sorbed Ag on OM, was observed [22]. In the present study, we investigated the Ag distribution in the soil without plant and in rape and wheat rhizospheres (figs. S5-S7), and determined the particle size distribution for these samples and rape rhizosphere (Fig. S8). The soil without plant and wheat rhizosphere have similar proportion of Ag particles below 100 nm (30–38 % in number of particles). Rape rhizosphere presents only 12 % of particles in this size class, and presents more diffuse Ag mentioned above, which is not taken into account in particle counting procedure. This observation may indicate more efficient weathering of Ag₂S particles in the rhizosphere of rape. However, additional Ag distribution maps would be necessary to confirm this hypothesis. Furthermore, there may be a bias in the comparison since the Ag distribution map for rape shows a large organic particle, containing diffuse Ag, whereas the Ag distribution maps from the other samples show more minerals. To conclude on this particle size analysis, in all conditions Ag particles cover a distribution of sizes, from

micro to nano sized particles to diffuse Ag, and this diffuse Ag corresponds to Ag associated with organic particles.

The role of organic matter (OM) in the stability of AgNPs is controversial. On the one hand it can stabilize them in soils via hetero-aggregation with soil minerals [18,19] and protect them from dissolution by blocking oxidation sites [32]. On the other hand, free radicals resulting from interactions between soil organic matter, microorganisms and iron oxides [33] may oxidize Ag₂S-NP (Li et al. [34]). In the present study, we could not identify the factor(s) or soil component(s) responsible for the weathering of Ag₂S-NPs, but it is clear that organic matter, through thiol groups, served as a sink for Ag⁺ released from the particles. Besides, the presence of Ag⁺ released through the oxidative dissolution of AgNPs that have not undergone sulfidation during wastewater treatment cannot be excluded.

### 3.4. Presence of mixed metal sulfides

In our previous study we found the presence of mixed metal sulfides in rape rhizosphere [22]. In the present work we wanted to evaluate the presence of these mixed sulfides in the soil without plant and wheat rhizosphere. Figs. S5–7 displays nanoXRF maps collected on thin sections of soil without plant and rape and wheat rhizospheres, showing Ag (Red), Cu (Green) and Zn (Blue) distribution. In the soil without plant, we found a colocalization of Ag and Zn (Fig. S5). In wheat rhizosphere (Fig. S7) we show Ag-Cu-Zn aggregates. Mixed sulfides have been observed in sewage sludge from a lab scale wastewater treatment plant (Georgantzopoulou et al. [35] and Etschmann et al. [36] showed that in fresh biosolids Cu was present as micrometer Cu sulfide particles but after aging of biosolids, Cu was evenly distributed on organic matter. Thalmann et al., [37] and Zhang et al., [38] showed that Ag⁺ in the presence of metal sulfides (ZnS, CuS) undergo sulfidation, at the expense of other metal sulfides. Together, our data and the findings from literature suggest that metal sulfides can be a source of sulfur for the sulfidation of Ag⁺ either in the sewage sludge or after application of the sludge in soils.

### 3.5. Conclusions and perspectives

This study presents an original combination of spectroscopic approaches to better understand the fate of AgNPs in agricultural soils amended with sewage sludge. The presence of a secondary Ag—S species

<figure><img src="image_5.png" /><figcaption>**Fig. 3.** a) Two-colour µXRF map of a soil thin section from the rape rhizosphere, collected at 2474 eV, showing the distribution of S (magenta) and Si (cyan). Orange squares show the areas where S K edge µXANES spectra were collected in mapping mode. b) Top: S K µXANES spectra (solid lines) and LCFs (dashed lines) from the orange square areas. Bottom: average and standard deviations of S species distribution obtained from these three LCFs. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 4.** Detailed analysis of the orange square 2 shown in Fig. 3 (Rape rhizosphere) a) µXRF map showing S distribution in temperature scale. B) S K edge µXANES spectra extracted from pixels numbered in a). Spectra show an evolution as a function of the intensity of S, with more reduced S in the regions with higher S intensity.</figcaption></figure>

was previously evidenced at the bulk scale. By combining µXANES at the Ag and S edges, we were able to identify this species as Ag-thiolate, and show that it formed a corona around Ag₂S-NP. The gradient from Ag₂S to Ag-thiolate from the nanoparticles to the outside suggested a transfer of Ag⁺ from inorganic S (sulfide) to organic S (sulfhydryl) groups of organic matter. However, based on our data, we cannot exclude the possibility that these Ag⁺ ions originated from the oxidative dissolution of AgNPs that were not fully sulfidized during wastewater treatment. Besides Ag₂S-NPs and Ag-thiolate, Ag was also present as mixed metal sulfides. The reactivity of this third species is likely different from Ag₂S-NPs. Ag-containing nanoparticles cover a large range of sizes, from >300 nm to <100 nm. Nanoparticle size is another parameter likely affecting the reactivity of Ag-containing nanoparticles.

Taken together, these results show that organic matter is the main sink for Ag⁺ present in soils amended with sewage sludge polluted with AgNPs. Whether these Ag⁺ come from the weathering of Ag₂SNPs or were never sulfidized after the oxidative dissolution of the AgNPs in the wastewater treatment, remains to be elucidated.

In terms of perspectives, determining the solubility constants of Ag₂S-NP and mixed metal sulfides nanoparticles, as well as the impact of particle size, and implementing them in thermodynamic models would improve our prediction of Ag release over time. In addition, a better characterization of the interactions between Ag⁺ and natural organic matter would help to evaluate the stability of the secondary Ag species. In the same way, the role of rhizospheric activity in the weathering of Ag₂S-NP and formation of Ag-thiolate should be considered as the exudation of organic compounds by plant roots and the specific redox conditions of the rhizosphere can have an impact in the weathering process.

The multi-scale, high-resolution approach used in this study represents a novel and powerful methodology for studying nanoparticle behavior in complex environmental matrices. Metal sulfides play a key role in inmobilizing metals and nanoparticles in sewage sludge and soils. The original combination of Ag L-edge and S K-edge XAS has proven to be crucial for identifying minor metal-S species, enabling a better understanding of their mobility, reactivity, and potential bioavailability. Moreover, the use of full-mapping XAS emerges as an essential tool for studying weathering processes and chemical gradients in general.

### CRediT authorship contribution statement

**Ana Elena Pradas del Real:** Writing – review & editing, Writing – original draft, Investigation, Formal analysis, Data curation, Conceptualization.
**Hiram Castillo-Michel:** Investigation, Formal analysis, Data curation, Conceptualization.
**Ralf Kaegi:** Writing – review & editing, Validation, Conceptualization.
**Juan Reyes-Herrera:** Visualization, Formal analysis, Data curation.
**Remi Tucoulou:** Visualization,

Investigation, Formal analysis. **Geraldine Sarret:** Writing – review & editing, Writing – original draft, Supervision, Funding acquisition, Conceptualization.

### Funding sources

This project was funded by the French program LabEx Serenade (11-LABX-0064), CNRS (PEPS project NANOPLANTE) and COST ES1205 (ENTER).

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgment

ISTerre is part of Labex OSUG@2020 (ANR10 LABX56). We thank the ESRF committees for the provision of beamtime, and the staff of ID21 and ID16b beamlines for their assistance during measurements.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.sab.2025.107258.

### Data availability

Data will be made available on request.

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