| 1. |
- Boily, Jean-Francois, et al.
(författare)
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Direct identification of reaction sites on ferrihydrite
- 2020
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Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyl groups are the cornerstone species driving catalytic reactions on mineral nanoparticles of Earth's crust, water, and atmosphere. Here we directly identify populations of these groups on ferrihydrite, a key yet misunderstood iron oxyhydroxide nanomineral in natural sciences. This is achieved by resolving an enigmatic set of vibrational spectroscopic signatures of reactive hydroxo groups and chemisorbed water molecules embedded in specific chemical environments. We assist these findings by exploring a vast array of configurations of computer-generated nanoparticles. We find that these groups are mainly disposed along rows at edges of sheets of iron octahedra. Molecular dynamics of nanoparticles as large as 10 nm show that the most reactive surface hydroxo groups are predominantly free, yet are hydrogen bond acceptors in an intricate network formed with less reactive groups. The resolved vibrational spectroscopic signatures open new possibilities for tracking catalytic reactions on ferrihydrite, directly from the unique viewpoint of its reactive hydroxyl groups. Ferrihydrite nanoparticles have many hydroxyl sites which can react with environmental contaminants and nutrients, but the surface structure of this common mineral is still not fully understood. Here, a combination of vibrational spectroscopy and molecular simulations identify hydroxyl groups exposed along rows at the edges of sheets of iron octahedra.
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| 2. |
- Ding, Xiangbin, et al.
(författare)
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Identification of fluoride and phosphate binding sites at FeOOH surfaces
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:41, s. 21939-21947
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Tidskriftsartikel (refereegranskat)abstract
- Iron oxyhydroxide minerals occur widely in nature and play important roles in environmental and industrial processes. Owing to their high reactivity, these minerals can act as sinks and/or transformation centers for a variety of inorganic and organic ions. Interfacial reactions are often mediated by surface (hydr)oxo groups. These groups can be singly, doubly, or triply coordinated with respect to underlying Fe atoms. In order to investigate the reactivity of these differently coordinated groups, Fourier transform infrared (FTIR) spectroscopy was used to examine adsorption products formed on iron oxyhydroxide surfaces. The absence of water was required to probe the O-H stretching region after initial reactions in aqueous media. This work was specifically focused on synthetic, submicrometer-sized lepidocrocite and goethite particles reacted with aqueous solutions of sodium fluoride and monosodium phosphate. Langmuir-Freundlich adsorption isotherms were calibrated on adsorption data in aqueous media at various pH values to obtain the maximum sorption densities for these ions under these conditions. FTIR measurements of the resulting solids dried under N-2(g) show that fluoride and phosphate ions preferentially exchange with singly coordinated hydroxyls. Doubly coordinated groups can, however, be exchanged with fluoride ions at relatively high loading densities. Triply coordinated groups remain, in contrast, resilient to exchange. They may, however, stabilize phosphate species by hydrogen bonding. These findings add further constraints to our understanding of adsorption reactions and to the formulation of molecularly adequate thermodynamic models.
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| 3. |
- Guo, Huijie, et al.
(författare)
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Regulation of photoinduced charge transfer in all-small-molecule organic solar cells through the synergistic effect of external electric field and solvent
- 2024
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Ingår i: Journal of Luminescence. - 0022-2313. ; 268
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Tidskriftsartikel (refereegranskat)abstract
- The donor (BTR-Cl) and acceptor (BTP-FCl-FCl) have well-defined small molecule properties and excellent repeatability, and they can form charge transfer complexes with a wide spectral absorption range. Using density functional theory (DFT), we simulate the photoinduced charge transfer of bulk-heterojunction (BHJ) organic solar cell (OSC) materials modulated by the external electric field (Fext) at the microscopic level. The excited-state properties, reorganization energy (λ), Gibbs free energy (ΔG), electron coupling matrix elements (VDA) and intermolecular charge transfer (ICT) rate dependent on Fext are systematically analyzed. The results manifest that Fext has apparent positive regulation on the charge separation rate (KCS), and VDA is the main factor affecting KCS. The synergistic effect of solvent and Fext on charge transfer process is further investigated. It is found that the charge transfer rate in solvent is lower than that in solvent-free conditions, and the charge transfer rate in chlorobenzene (CB) solvent does not change significantly under the control of Fext. At the same time, Fext has a positive effect on the charge transfer rate in tetrahydrofuran (THF) solvent. Considering the charge transfer rate under different solvents and Fext intensities, it is found that the solvent and Fext play an essential role in determining the KCS and charge recombination rate (KCR).
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| 4. |
- Ma, Zhuo, et al.
(författare)
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Deciphering early human pancreas development at the single-cell level
- 2023
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding pancreas development can provide clues for better treatments of pancreatic diseases. However, the molecular heterogeneity and developmental trajectory of the early human pancreas are poorly explored. Here, we performed large-scale single-cell RNA sequencing and single-cell assay for transposase accessible chromatin sequencing of human embryonic pancreas tissue obtained from first-trimester embryos. We unraveled the molecular heterogeneity, developmental trajectories and regulatory networks of the major cell types. The results reveal that dorsal pancreatic multipotent cells in humans exhibit different gene expression patterns than ventral multipotent cells. Pancreato-biliary progenitors that generate ventral multipotent cells in humans were identified. Notch and MAPK signals from mesenchymal cells regulate the differentiation of multipotent cells into trunk and duct cells. Notably, we identified endocrine progenitor subclusters with different differentiation potentials. Although the developmental trajectories are largely conserved between humans and mice, some distinct gene expression patterns have also been identified. Overall, we provide a comprehensive landscape of early human pancreas development to understand its lineage transitions and molecular complexity. Here, the authors revealed molecular heterogeneity, developmental trajectory and regulatory network of early human pancreas development, and depict the whole progression of pancreatic organogenesis during the first trimester at the single-cell level.
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| 5. |
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| 6. |
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| 7. |
- Shi, Yali, et al.
(författare)
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Tissue Distribution and Whole Body Burden of the Chlorinated Polyfluoroalkyl Ether Sulfonic Acid F-53B in Crucian Carp (Carassius carassius) : Evidence for a Highly Bioaccumulative Contaminant of Emerging Concern
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:24, s. 14156-14165
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Tidskriftsartikel (refereegranskat)abstract
- Following the global actions to phase out perfluoroctanesulfonic acid (PFOS) a large number of alternative per- and polyfluoroalkyl substances, with poorly defined hazard properties, are being used in increasing quantities. Here, we report on the first detection of the chlorinated polyfluoroalkyl ether sulfonic acid F-53B in biological samples and determine the tissue distribution and whole body bioaccumulation factors (BAF(whole body)) in crucian carp (Carassius carassius). Analysis of fish samples from Xiaoqing River (XR) and Tangxun Lake (TL) demonstrated a similar level of F-53B contamination with median concentrations in blood of 41.9 and 20.9 ng/g, respectively. Tissue/blood ratios showed that distribution of F-53B primarily occurs to the kidney (TL: 0.48, XR: 0.54), gonad (TL: 0.36, XR: 0.54), liver (TL: 0.38, XR: 0.53), and heart (TL: 0.47, XR: 0.47). Median Log BAF(whole body) values for F-53B (XR: 4.124, TL: 4.322) exceeded regulatory bio accumulation criterion and were significantly higher than those of PFOS in the same data sets (XR: 3.430, TL: 3.279). On the basis of its apparent omnipresence and strong bioaccumulation propensity, it is hypothesized that F-53B could explain a significant fraction of previously unidentified organofluorine in biological samples from China, and regulatory actions for this compound are encouraged.
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| 8. |
- Song, Xiaowei, et al.
(författare)
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A Matrix Correction Approach to Estimate the Bioaccumulation Potential of Emerging PFASs
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies employing high-resolution mass spectrometry have discovered numerous emerging per- and polyfluoroalkyl substances (PFASs) in the environment, but the lack of authentic standards for these contaminants hampers quantitative evaluation of hazard properties. Here we tested a matrix correction methodology for determining the bioaccumulation potential of emerging PFASs based on peak area in crucian carp from Xiaoqing river, China. Fortification experiments of emerging PFASs extracted from surface water and sediment samples demonstrated that the quantification bias in fish tissues was <34% for analytes detected in fish and water. Tissue distribution ratios (TBRs) and whole-body bioaccumulation factors (BAFs) were subsequently calculated by correcting for analyte- and tissue-specific matrix effects. A model evaluation set including 7 reference PFASs demonstrated that peak area-based TBRs and BAFs were strongly correlated with those calculated from quantified concentrations (p<0.05, Adjusted r2>0.91, slope: 0.99-1.34). Among the detected substances, the trimer acid of hexafluoropropylene oxide and C9 monoether per- and polyfluoroalkyl ether carboxylic acid (PFECA) were identified as bioaccumulative substances. C8 PFECA and C8 mono chlorine-substituted perfluoroalkyl carboxylic acid displayed similar BAFs value compared to perfluorooctanoic acid. Overall, the proposed methodology provides a rapid hazard screening tool which could be used to assess emerging contaminants without access to authentic standards.
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| 9. |
- Song, Xiaowei, et al.
(författare)
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A Matrix Correction Approach to Estimate the Bioaccumulation Potential of Emerging PFASs
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies employing high-resolution mass spectrometry have discovered numerous emerging per- and polyfluoroalkyl substances (PFASs) in the environment, but the lack of authentic standards for these contaminants hampers quantitative evaluation of hazard properties. Here we tested a matrix correction methodology for determining the bioaccumulation potential of emerging PFASs based on peak area in crucian carp from Xiaoqing river, China. Fortification experiments of emerging PFASs extracted from surface water and sediment samples demonstrated that the quantification bias in fish tissues was <34% for analytes detected in fish and water. Tissue distribution ratios (TBRs) and whole-body bioaccumulation factors (BAFs) were subsequently calculated by correcting for analyte- and tissue-specific matrix effects. A model evaluation set including 7 reference PFASs demonstrated that peak area-based TBRs and BAFs were strongly correlated with those calculated from quantified concentrations (p<0.05, Adjusted r2>0.91, slope: 0.99-1.34). Among the detected substances, the trimer acid of hexafluoropropylene oxide and C9 monoether per- and polyfluoroalkyl ether carboxylic acid (PFECA) were identified as bioaccumulative substances. C8 PFECA and C8 mono chlorine-substituted perfluoroalkyl carboxylic acid displayed similar BAFs value compared to perfluorooctanoic acid. Overall, the proposed methodology provides a rapid hazard screening tool which could be used to assess emerging contaminants without access to authentic standards.
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| 10. |
- Song, Xiaowei, 1986-, et al.
(författare)
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Carbon dioxide binding at dry FeOOH mineral surfaces : evidence for structure-controlled speciation
- 2013
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Ingår i: Environmental Science and Technology. - Washington : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:16, s. 9241-9248
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between CO2(g) and mineral surfaces are important to atmospheric and terrestrial settings. This study provides detailed evidence on how differences in mineral surface structure impact carbonate speciation resulting from CO2(g) adsorption reactions. It was achieved by resolving the identity of adsorption sites and geometries of (bi)carbonate species at surfaces of nanosized goethite (alpha-FeOOH) and lepidocrocite (gamma-FeOOH) particles. Fourier transform infrared spectroscopy was used to obtain this information on particles contacted with atmospheres of CO2(g). Vibrational modes of surface hydroxo groups covering these particles were first monitored. These showed that only one type of the surface groups that are singly coordinated to Fe atoms (-OH) are involved in the formation of (bi)carbonate species. Those of higher coordination numbers (mu-OH, mu(3)-OH) do not participate. Adsorption geometries were then resolved by investigating the C-O stretching region, assisted by density functional theoretical calculations. These efforts provided indications leaning toward a predominance of mononuclear species, -O-CO2Hx=[0,1]. In contrast, monodentate binuclear species of (-O)(2)center dot COHx=[0,1], are expected to form at particle terminations and surface defects. Finally, calculations suggested that bicarbonate is the dominant species on goethite, while a mixture of bicarbonate and carbonate species is present on lepidocrocite, a result stemming from different hydrogen bonding patterns at these mineral surfaces.
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| 11. |
- Song, Xiaowei, et al.
(författare)
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Competitive ligand exchange on akaganéite surfaces enriches bulk chloride loadings
- 2012
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 376:1, s. 331-3
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Tidskriftsartikel (refereegranskat)abstract
- Akaganéite (β-FeOOH) is a nanosized iron oxyhydroxide mineral with a hollandite structure containing chloride ions in 0.4×0.4nm wide channels. Proton and chloride co-sorption into these channels induces variations in bulk O-H stretching vibrations, crystallographic lattice size, and thermal stability, as a result of hydrogen bond formation with chloride ions. In this work, we show that chloride ions bound to akaganéite surfaces can be dislodged into aqueous solutions by competitive adsorption of foreign ions and then transferred alongside co-sorbed protons into the akaganéite bulk. Fourier transform infrared and X-ray photoelectron spectroscopic measurements show that HClO(4), H(2)SO(4), and benzoic acid, and thereby, many other anions of various charge-to-size ratios can all effectively contribute to this phenomenon. This linked surface-bulk reactivity should be accounted for in mixed anion systems containing akaganéite-like materials.
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| 12. |
- Song, Xiaowei, et al.
(författare)
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Structural controls on OH site availability and reactivity at iron oxyhydroxide particle surfaces
- 2012
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:8, s. 2579-86
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Tidskriftsartikel (refereegranskat)abstract
- Iron oxyhydroxides (FeOOH) are highly reactive minerals of widespread occurrence in natural and industrial settings. These minerals chiefly occur as nano- to submicron-sized particles and are covered by hydroxyl functional groups coordinated to one (-OH), two (μ-OH), or three (μ(3)-OH) underlying iron atoms. These groups are reaction centers for gases, solutes as well as solvents and thereby play important roles in the fate and transformation of natural and industrial compounds. In this work we provide tools to identify hydroxyl groups on distinct crystallographic planes of two important FeOOH polymorphs, namely lepidocrocite (γ-FeOOH) and goethite (α-FeOOH). Fourier transform infrared spectroscopy was used to monitor O-H stretching vibrations of groups on particles with well-defined and distinct morphologies. Spectral responses to proton loadings and thermal gradients were used to assign bands to hydroxyl groups. These efforts were facilitated by the extraction of pure spectral components obtained by multivariate curve resolution. Molecular dynamics simulations of dominant crystallographic planes of the particles guided band assignment procedures by identifying feasible hydrogen bond networks between surface groups. Our findings provide new possibilities for molecular-scale resolution of important gas-phase processes on the surfaces of these important minerals.
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| 13. |
- Song, Xiaowei, 1986-
(författare)
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Surface and Bulk Reactivity of Iron Oxyhydroxides : A Molecular Perspective
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Iron oxyhydroxide (FeOOH) mineral plays an important role in a variety of atmospheric, terrestrial and technological settings. Molecular resolution of reactions involving these minerals is thereby required to develop a fundamental understanding of their contributions in processes taking place in the atmosphere, Earth’s upper crust as well as the hydrosphere. This study resolves interactions involving four different types of synthetic FeOOH particles with distinct and well-defined surfaces, namely lath- and rod-shaped lepidocrocite (γ), goethite (α) and akaganéite (β). The surface and bulk reactivities of these particles are controlled by their distinct structures. When exposed to ambient atmospheric or aqueous conditions their surfaces are populated with different types of (hydr)oxo functional groups acting as reaction centers. These sites consist of hydroxyl groups that can be singly- (≡FeOH, -OH), doubly- (≡Fe2OH, μ-OH), or triply-coordinated (≡Fe3OH, μ3-OH) with underlying Fe atoms. Moreover, these sites exhibit different types, densities, distributions, as well as hydrogen bonding patterns on different crystal planes for each mineral. Knowledge of the types and distributions of hydroxyl groups on minerals with different surface structures is fundamental for building a molecular-scale understanding of processes taking place at FeOOH particle surfaces.In this thesis, Fourier transform infrared (FTIR) spectroscopy was used to resolve the interactions between (hydr)oxo groups of FeOOH particles with (in)organic acids, salts, water vapor as well as carbon dioxide. The focus on such compounds was justified by their importance in natural environments. This thesis is based on 9 articles and manuscripts that can be found in the appendices.FTIR spectroscopic signatures of hydroxyl groups in the bulk of well crystallized FeOOH minerals were characterized for structural differences and thermal stabilities. Those of akaganéite were particularly resolved for the variable bond strength of bulk hydroxyls induced by the incorporation of HCl through nanostructured channels at the terminations of the particles. FTIR bands of hydroxyl groups at all particle surfaces were monitored for responses to thermal gradients and proton loadings, providing experimental validation to previous theoretical accounts on surface site reactivity. This site reactivity was resolved further in the fluoride (F-) and phosphate (PO43-) ions adsorption study to follow the site selectivity for ligand-exchange reactions. These efforts showed that singly-coordinated groups are the primary adsorption centers for ligands, doubly-coordinated groups can only be exchanged at substantially higher ligand loadings, while triply coordinated groups are largely resilient to any ligand-exchange reaction.These findings helped consolidate fundamental knowledge that can be used in investigating sorption processes involving atmospherically and geochemically important gases. The latter parts of this thesis were therefore focused on water vapor and carbon dioxide interactions with these FeOOH particles. These efforts showed how surface structure and speciation affect sorption loadings and configurations, as well as how water diffused into and through the akaganéite bulk. Hydrogen bonding is one of the most important forms of interactions between gas phase and minerals. It plays a crucial role in the formation of thin water films and in stabilizing surface (bi)carbonate species. The affinity of surface hydroxyl groups for water and carbon dioxide is strongly dependent on their abilities to form hydrogen bonds. These are controlled by coordination number and site accessibility/steric constraints. In agreement with the aforementioned ligand-exchange studies, surfaces dominated by singly coordinated groups have stronger ability to accumulate water layers than the ones terminated by groups of larger coordination number. Collectively, these efforts consolidate further the concept for structure-controlled reactivities in iron oxyhydroxides, and pave the way for new studies along such lines.
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| 14. |
- Song, Xiaowei, et al.
(författare)
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Surface and Bulk Thermal Dehydroxylation of FeOOH Polymorphs
- 2016
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 120:31, s. 6249-6257
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Tidskriftsartikel (refereegranskat)abstract
- In this study, bulk and surface thermal decomposition of synthetic iron oxyhydroxides to iron oxides was followed using the temperature programmed desorption (TPD) technique. Submicron-sized akaganeite beta-FeOOH), rod- and lath-shaped lepidocrocite (gamma-FeOOH), and goethite (alpha-FeOOH) particles were heated in vacuo in the 30-400 degrees C range, and their OH vibrational modes were monitored by Fourier transform infrared (FTIR) spectroscopy while H2O(g) release was monitored by quadrupole mass spectrometry. Peak thermal dehydroxylation temperatures were larger in the order of lath lepidocrocite (200 degrees C) < akaganeite (200/260 degrees C) < rod lepidocrocite (268 degrees C) < goethite (293 degrees C). Pre-equilibration of these particles to aqueous solutions of HCl increased dehydroxylation temperatures of all minerals except goethite by 13-40 degrees C. These shifts were explained by (1) the dissolution of particles or regions of particles of lower degree of crystallinity by HCl, as well as (2) the strengthening of the hydrogen bond environment in the akaganeite bulk. The latter is a means of facilitating H2O(g) formation via interactions between two adjacent OH groups. Strongly analogous forms of interactions at the FeOOH particle surfaces were also shown to facilitate the release of singly coordinated (-OH) hydroxo groups to the gas phase at temperatures lower than 125 degrees C, thus creating OH vacancies that may be actively involved in the transfer of bulk to surface OH groups during thermal dehydroxylation. Doubly- (mu-OH) and triply- (mu(3)-OH) coordinated hydroxo groups were however resilient to exchange under those conditions, and their dehydroxylation was strongly congruent with that of bulk OH groups. By resolving the bulk and surface thermal decomposition of FeOOH polymorphs, this work provides clearer insight into the fate of these materials in natural and technological settings where important thermal gradients are commonplace.
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| 15. |
- Song, Xiaowei, et al.
(författare)
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Surface Hydroxyl Identity and Reactivity in Akaganeite
- 2011
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Ingår i: The Journal of Physical Chemistry C. - Washington DC : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:34, s. 17036-17045
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyl groups on surfaces of well-defined akaganeite (beta-FeOOH) particles were identified by Fourier transform infrared spectroscopy. These efforts, assisted by molecular dynamics simulations, enabled the extraction of spectral signatures for these groups of the dominant (100), (001), and (010) crystallographic planes. Band assignments were supported by spectral variations induced by proton and chloride adsorption as well as temperature-programmed desorption. Molecular dynamics simulations were used to determine patterns and free energies of formation of hydrogen bonds. Surface Fe-O distances as well as hydrogen-bond numbers were also used to predict proton affinities. All spectral component concentrations display highly comparable responses to proton loadings with those of other FeOOH minerals previously studied with our coupled experimental-theoretical approach. These similarities underpin common thermodynamic stabilities for hydroxyls of a given Fe nuclearity on different planes of different minerals.
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| 16. |
- Song, Xiaowei, et al.
(författare)
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Variable Hydrogen Bond Strength in Akaganeite
- 2012
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Ingår i: The Journal of Physical Chemistry C. - Washington DC : American Ceramic Society. - 1932-7447 .- 1932-7455. ; 116:3, s. 2303-2312
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Tidskriftsartikel (refereegranskat)abstract
- Akaganeite (beta-FeOOH) is a chloride-bearing iron oxy-hydroxide with a hollandite-type structure. This high specific surface area mineral has been the object of numerous studies given its high reactivity and involvement in natural and industrial processes. The important ion exchange attributes of this mineral involve similar to 0.4 x 0.4 nm wide channels in which chloride ions are stabilized by hydrogen bonding from bulk OH groups. This work provides further details on the relationship between bulk chloride ion loadings and hydrogen bond strengths. Molecular dynamics calculations were first carried out on chloride-free and bearing lattices to build a conceptual model for possible interactions in the akaganeite bulk. Experimental work was thereafter carried out on synthetic acicular particles (7 x 80 to 11 x 110 nm) reacted to aqueous solutions of HCl, then dried under dry N-2(g). These samples were studied by Fourier transform infrared spectroscopy, temperature-programmed desorption, X-ray photoelectron spectroscopy, and X-ray powder diffraction as well as transmission electron spectroscopy. Results collectively show that Cl/Fe molar ratios increasing from 0.169 up to 0.442 induce important changes in the hydrogen bonding environment of bulk hydroxyls. This can specifically be seen through shifts in bulk O-H stretching frequencies from 3496/3395 to 3470/3350 cm(-1). These changes are associated with a substantial shortening of particle lengths (97 to 45 nm), expansion of crystallographic lattice size (up to 0.9%), and increases in median thermal dehydroxylation temperatures (260 to 305 degrees C). Our work thereby highlights important variations in physicochemical attributes of akaganeite particles reacted with HCl. Such variations should consequently be considered in settings involving submicrometer-sized akaganeite particles.
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| 17. |
- Song, Xiaowei, et al.
(författare)
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Water Vapor Adsorption on Goethite
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:13, s. 7171-7177
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Tidskriftsartikel (refereegranskat)abstract
- Goethite (α-FeOOH) is an important mineral contributing to processes of atmospheric and terrestrial importance. Interactions with water vapor are particularly relevant in these contexts. In this work, molecular details of water vapor (0.0-19.0 Torr; 0-96 % relative humidity at 25 °C) adsorption at surfaces of synthetic goethite nanoparticles reacted with and without HCl and NaCl were resolved using vibrational spectroscopy. This technique probed interactions between surface (hydr)oxo groups and liquid water-like films. Molecular dynamics showed that structures and orientations adopted by these waters are comparable to those adopted at the interface with liquid water. Particle surfaces reacted with HCl accumulated less water than acid-free surfaces due to disruptions in hydrogen bond networks by chemisorbed waters and chloride. Particles reacted with NaCl had lower loadings below ~10 Torr water vapor but greater loadings above this value than salt-free surfaces. Water adsorption reactions were here affected by competitive hydration of coexisting salt-free surface regions, adsorbed chloride and sodium, as well as precipitated NaCl. Collectively, the findings presented in this study add further insight into the initial mechanisms of thin water film formation at goethite surfaces subjected to variations in water vapor pressure that are relevant to natural systems.
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| 18. |
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| 19. |
- Song, Xiaowei, et al.
(författare)
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Water Vapor Diffusion into a Nanostructured Iron Oxyhydroxide
- 2013
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:12, s. 7107-7113
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Tidskriftsartikel (refereegranskat)abstract
- Water diffusion through 0.4 nm × 0.4 nm wide tunnels of synthesized akaganéite (β-FeOOH) nanoparticles was studied by a coupled experimental–molecular modeling approach. A sorption isotherm model obtained from quartz crystal microbalance measurements suggests that the akaganéite bulk can accommodate a maximum of 22.4 mg of water/g (44% bulk site occupancy) when exposed to atmospheres of up to 16 Torr water vapor. Fourier transform infrared spectroscopy also showed that water molecules interact with (hydr)oxo groups on both the akaganéite bulk and surface. Diffusion reactions through the akaganéite bulk were confirmed through important changes in the hydrogen-bonding environment of bulk hydroxyl groups. Molecular dynamics simulations showed that water molecules are localized in cavities that are bound by eight hydroxyl groups, forming short-lived (<0.5 ps) hydrogen bonds with one another. Diffusion coefficients of water are three orders of magnitude lower than they are in liquid water (D = 0.0–11.1 × 10–12 m2·s–1), whereas large integral rotational correlation times are 4 to 15 times higher (τr = 8.4–31.8 ps). Moreover, both of these properties are strongly loading-dependent. The simulations of the interface between the water vapor phase and the (010) surface plane of the akaganéite, where tunnel openings are exposed, revealed sluggish rates of incorporation between interfacial water species and their tunnel counterparts. The presence of defects in the synthesized particles are suspected to contribute to different diffusion rates in the laboratory when compared to those observed in pristine crystalline materials, as studied by molecular modeling.
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| 20. |
- Song, Xiaowei, et al.
(författare)
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Water vapor interactions with FeOOH particle surfaces
- 2013
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 560, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between iron (oxyhydr)oxide particle surfaces and water are of fundamental importance to natural and technological processes. In this Letter, we probe the interactions between submicron-sized lepidocrocite (γ-FeOOH) surfaces and gaseous water using Fourier transform infrared spectroscopy. Formation of hydrogen bonds between different lepidocrocite surface OH functional groups and water was specifically monitored in the O–H stretching region. Molecular dynamics simulations of the dominant crystallographic terminations of these particles provided insights into interfacial water structures and hydrogen bonding networks. Theoretical power spectra were moreover used to validate interpretations of experimental spectra. This Letter constrains our understanding of incipient water adsorption reactions leading to thermodynamically stable and reversible thin water films at FeOOH particle surfaces. It also suggests that these water layers are structurally analogous precursors to those occurring at a FeOOH surfaces contacted with liquid water.
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| 21. |
- Wang, Yilin, et al.
(författare)
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Interrupted silicogermanate with 10-ring channels : synthesis and structure determination by combining rotation electron diffraction and powder X-ray diffraction
- 2017
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Ingår i: Inorganic Chemistry Frontiers. - 2052-1545 .- 2052-1553. ; 4:10, s. 1654-1659
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Tidskriftsartikel (refereegranskat)abstract
- Silicogermanate (JU110) with an interrupted open-framework has been synthesized by using a hydrothermal method using 1,1′-(1,4-phenylenebis(methylene))bis(1-methylpyrrolidin-1-ium) hydroxide as an organic structure-directing agent (OSDA). Silicon and fluoride anions were introduced to the concentrated-gel synthesis system, and different synthetic parameters influencing the synthesis were discussed. The structure of JU110 was characterised by using rotation electron diffraction (RED) and high-resolution powder X-ray diffraction. JU110 crystallizes in the space group Fm2m (No. 42) with a = 13.9117(2) Å, b = 18.2980(3) Å and c = 32.7800(6) Å. The structure is constructed by the sti layers found in the STI framework that are pillared by D4R/Ge7 units to form a large cavity, showing 10-ring openings along [100] and 9-ring openings along [110]. Thermal stability studies showed that the framework was maintained with the loss of water molecules, but collapsed with the removal of charge-compensating cations.
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| 22. |
- Yeşilbaş, Merve, et al.
(författare)
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Carbon dioxide binding in supercooled water nanofilms on nanominerals
- 2020
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry. - 2051-8153 .- 2051-8161. ; 7:2, s. 437-442
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Tidskriftsartikel (refereegranskat)abstract
- Moist CO2-bearing air flowing in Earth's terrestrial environments and now warming cryosphere can be captured by thin nanometric water films supported by mineral nanoparticles. Molecular-level mechanisms driving the fate of CO2 by these water films at 25, −10 and −50 °C were resolved by vibration spectroscopy of mineral nanoparticles of well-known crystal habits and surface structures. This work shows that mineral-supported water films cooled below the freezing point of water do not freeze to ice and instead host hydrated carbonate species of comparable properties to those formed at 25 °C. CO2 uptake by water films is driven by nucleophilic attack of surface hydroxo groups. Conversion to carbonate species is, in turn, stabilised by hydrogen bonding with neighbouring hydroxo groups and water molecules. The lower CO2 uptake under extremely cold conditions (−50 °C) is, as such, explained by the reduced mobility of water needed to hydrate carbonate ions. Carbonate species initially entrapped by cooling of warmer films to −50 °C are nonetheless resilient to outgassing, even under vacuum. This implies that CO2 initially entrapped by cooling of warm CO2-bearing water films can have prolonged lifetimes under extremely cold conditions. Our findings shine new light on how nanominerals and the nanofilms they host alter the fate of CO2 in cold terrestrial environments. This chemistry is even strongly relevant to nanominerals in Earth's atmosphere and on the planet Mars.
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