| 11. |
- Bengtsson, Åsa, et al.
(author)
-
Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems
- 2009
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:4, s. 2355-2362
-
Journal article (peer-reviewed)abstract
- A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca9(HPO4)2(PO4)4F2 is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented. The CaOH and OPO3H2 sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4) system. Besides a determination of the solubility product of Ca9(HPO4)2(PO4)4F2, two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (∼1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pHiep from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers the surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: ≡CaOH2+ + F− ⇋ ≡CaF + H2O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF2(s) in the most acidic pH range.
|
|
| 12. |
- Biasi, P., et al.
(author)
-
Revealing the role of bromide in the H2O2 direct synthesis with the catalyst wet pretreatment method (CWPM)
- 2017
-
In: AIChE Journal. - : American Institute of Chemical Engineers. - 0001-1541 .- 1547-5905. ; 63:1, s. 32-42
-
Journal article (peer-reviewed)abstract
- A tailor-made Pd0/K2621 catalyst was subjected to post synthesis modification via a wet treatment procedure. The aimwas the understanding of the role of promoters and how—if any—improvements could be qualitatively related to the cat-alyst performance for the H2O2direct synthesis. The Catalyst Wet Pretreatment Method was applied in different metha-nolic solutions containing H2O2, NaBr, and H3PO4, either as single modifiers or as a mixture. The catalyst wascharacterized by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. It was concluded that themodified catalysts give rise to higher selectivities compared to the pristi ne reference catalyst thus opening a possibilityto exclude the addit ion of the undesirable selectivity enhancers in the reaction medium. This work provides original evi-dence on the role of promoter s, especially bromide, allowing the formulation of a new reaction mechanism for one ofthe most challenging reactions recognized by the world.
|
|
| 13. |
- Boily, Jean-Francois, et al.
(author)
-
X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 2. tracing the relationship between surface charge and electrolyte adsorption
- 2010
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:6, s. 2613-2616
-
Journal article (peer-reviewed)abstract
- Colloidal-sized hematite spheroids exposed to aqueous NaCl solutions were investigated by X-ray photoelectron spectroscopy using the fast-frozen technique. The O 1s region provided evidence for (de)protonation reactions of surface (hydr)oxo groups of OH-enriched/O-depleted hematite Surfaces. These results were also correlated to changes in sodium (Na 1s) and chloride (Cl 2p) contents with pH. Electrolyte ion surface loadings were successfully predicted using a classic thermodynamic adsorption model normalized for surface site density. These efforts pointed to ion-specific inner-Helmholtz plane capacitances.
|
|
| 14. |
- Borah, Raju Kumar, et al.
(author)
-
Copper Oxide Nanoparticles as a Mild and Efficient Catalyst for N-Arylation of Imidazole and Aniline with Boronic Acids at Room Temperature
- 2017
-
In: Synlett. - : Georg Thieme Verlag KG. - 0936-5214 .- 1437-2096. ; 28:10, s. 1177-1182
-
Journal article (peer-reviewed)abstract
- The present work describes the excellent catalytic activity of copper(II) oxide nanoparticles (NPs) towards N-arylation of aniline and imidazole at room temperature. The copper(II) oxide NPs were synthesized by a thermal refluxing technique and characterized by FT-IR spectroscopy; powder XRD, SEM, EDX, TEM, TGA, XPS, BET surface area analysis, and particle size analysis. The size of the NPs was found to be around 12 nm having a surface area of 164.180 m(2) g(-1). The catalytic system was also found to be recyclable and could be reused in subsequent catalytic runs without a significant loss of activity.
|
|
| 15. |
- Bottone, Anna, et al.
(author)
-
Sodium hypochlorite as an oxidizing agent for removal of soil organic matter before microplastics analyses
- 2021
-
In: Journal of Environmental Quality. - : John Wiley & Sons. - 0047-2425 .- 1537-2537. ; 51:1, s. 112-122
-
Journal article (peer-reviewed)abstract
- The omnipresence of microplastics (MPs) across Earth's surface has raised concerns about their environmental impact and created an urgent need for methods to identify them in complex soil and sedimentary matrices. However, detecting MPs in the O horizons of soils is difficult because plastic polymers share many physical and chemical properties with natural soil organic matter (SOM). In this study, we assessed whether sodium hypochlorite (NaOCl), a reagent that can oxidize SOM and simultaneously preserve mineral constituents, can be used for MP analysis and characterization in soil environments. In addition, we scrutinized how factors such as MP size, polymer type, extraction methods, and soil matrix affect the recovery of microplastic particles. We used both hydrophobic and density-dependent separation methods to assess the effects of our oxidation treatment on the recovery of MP. We observed that NaOCl effectively removed SOM without greatly altering the surface properties of resistant MP polymers (polypropylene, polylactic acid, low-density polyethylene, and polyethylene terephthalate), which were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy after SOM removal. The NaOCl treatment caused some chlorination and formation of additional C–OH bonds on polymer surfaces, which likely contributed to the reduced efficiency of the hydrophobic-based (oil) extraction. We conclude that NaOCl treatment can improve detection of MPs in SOM-rich soil and that recovery of MPs from soils is influenced by MP size, polymer type, extraction method, and soil type, which makes it challenging to develop a universal analytical method.
|
|
| 16. |
- Bukhanko, Natalia, et al.
(author)
-
Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route
- 2013
-
In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 1:8, s. 883-893
-
Journal article (peer-reviewed)abstract
- The synthesis of 1-ethyl chloride in the gas-phase mixture of ethanol and hydrochloric acid over ZnCl2/Al2O3 catalysts was studied in a continuous reactor using both commercial and tailor-made supports. The catalytic materials were characterized by the means of structural (XPS, TEM, XRD, and BET) and catalytic activity (selectivity and conversion) measurements. The reaction parameters such as temperature, pressure, and feedstock flow rates were optimized for the conversion of ethanol to ethyl chloride. The new tailor-made highly porous Al2O3-based catalyst outperformed its commercial counterpart by exhibiting high conversion and selectivity (98%) at the temperature of 325 °C. Long-term stability tests (240 h) confirmed the excellent durability of the tailor-made alumina catalysts. The process demonstrated here poses an efficient and economic “green” large-scale on-site synthesis of this industrially important reactant in industry, where bioethanol is produced and 1-ethyl chloride is necessary, e.g., for ethylation of cellulose and synthetic polymer products. On-site in situ production of ethyl chloride avoids the problems associated with the transportation and storage of toxic and flammable 1-ethyl chloride.
|
|
| 17. |
- Bukhanko, Natalia, et al.
(author)
-
Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina and flexible 3-D carbon foam supported catalysts
- 2017
-
In: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 542:25, s. 212-225
-
Journal article (peer-reviewed)abstract
- Isopropyl chloride synthesis from isopropanol and HCl in gas phase over ZnCl2 catalysts supported on Al2O3 as well as flexible carbon foam was studied in a continuous reactor. A series of catalytic materials were synthesised and characterised by BET, XPS, SEM, TEM, XRD and NH3-TPD methods. Catalytic activity tests (product selectivity and conversion of reactants) were performed for all materials and optimal reaction conditions (temperature and feedstock flow rates) were found. The results indicate that the highest yield of isopropyl chloride was obtained over 5 wt.% ZnCl2 on commercial Al2O3 (No. II) (95.3%). Determination of product mixture compositions and by-product identification were done using a GC-MS method. Carbon foam variant catalyst, 5 wt.% ZnCl2/C, was found to perform best out of the carbon-supported materials, achieving ∼75% yield of isopropyl chloride. The kinetic model describing the process in a continuous packed bed reactor was proposed and kinetic parameters were calculated. The activation energy for the formation of isopropyl chloride reaction directly from isopropanol and HCl was found to be ∼58 kJ/mol.
|
|
| 18. |
- Cano, A., et al.
(author)
-
Contribution to the coordination chemistry of transition metal nitroprussides : a cryo-XPS study
- 2019
-
In: New Journal of Chemistry. - : Royal Society of Chemistry. - 1144-0546 .- 1369-9261. ; 43:12, s. 4835-4848
-
Journal article (peer-reviewed)abstract
- The series of coordination polymers under investigation was formed by the assembly of a pentacyanonitrosylferrate(ii) anionic block, [Fe(CN)(5)NO](2-), through monovalent and divalent transition metal ions, e.g. Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+. For divalent ions, the resulting materials have a 3D porous framework with attractive features for applications in gas storage and separation, as electroactive solids, light-driven molecular magnets, and so on; in this study, we report the results obtained for a series of coordination polymers using the cryogenic X-ray photoelectron spectroscopy (cryo-XPS) data; comprehensive details regarding their coordination chemistries were obtained from the acquired spectra in addition to their comparison with the structural and spectroscopic information obtained from other techniques. The results discussed herein are original and contribute towards the understanding of the electronic structures and related properties for this family of coordination polymers. This series of solids was found to be highly susceptible to strong damage induced by X-ray beams throughout the conventional XPS experiment; therefore, the analysis was conducted under cryogenic conditions.
|
|
| 19. |
- Cano, A., et al.
(author)
-
Intercalation of pyrazine in layered copper nitroprusside : synthesis, crystal structure and XPS study
- 2019
-
In: Journal of Solid State Chemistry. - : Elsevier. - 0022-4596 .- 1095-726X. ; 273, s. 1-10
-
Journal article (peer-reviewed)abstract
- Hybrid inorganic–organic solids form an interesting family of functional materials, where their functionalities are determined by both, the inorganic and organic building blocks. This study reports the intercalation of pyrazine in 2D copper nitroprusside, the crystal structure of the resulting hybrid solid and explores the scope of cryogenic X-ray photoelectron spectroscopy (XPS) to shed light on its electronic structure. In this material, the pyrazine molecule appears coordinated to Cu atoms from neighboring layers, to form the columns in the resulting 3D porous framework. Its crystal structure was solved and refined from the corresponding XRD powder pattern. XPS data, recorded under cryogenic conditions, provided fine details on the electronic structure of this hybrid solid. The binding energy values for the ligand atoms and the involved metals show a definite correlation with the structural data and FT-IR spectra. When XPS spectra were recorded at room temperature, a significant sample decomposition was observed. Three possible mechanisms for the sample damage during the XPS experiment are considered. The hybrid material under study is representative of a wide series of nanoporous solids obtained by intercalation of organic pillars between 2D inorganic solids.
|
|
| 20. |
- Cant, David J. H., et al.
(author)
-
Cryo-XPS for surface characterization of nanomedicines
- 2023
-
In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 127:39, s. 8220-8227
-
Journal article (peer-reviewed)abstract
- Nanoparticles used for medical applications commonly possess coatings or surface functionalities intended to provide specific behavior in vivo, for example, the use of PEG to provide stealth properties. Direct, quantitative measurement of the surface chemistry and composition of such systems in a hydrated environment has thus far not been demonstrated, yet such measurements are of great importance for the development of nanomedicine systems. Here we demonstrate the first use of cryo-XPS for the measurement of two PEG-functionalized nanomedicines: a polymeric drug delivery system and a lipid nanoparticle mRNA carrier. The observed differences between cryo-XPS and standard XPS measurements indicate the potential of cryo-XPS for providing quantitative measurements of such nanoparticle systems in hydrated conditions.
|
|
