| 1. |
- Chatterjee, Ritayan, et al.
(författare)
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Structure, microstructure and photocatalytic properties of embedded spherical Cu nanoparticles on Cu2O–SiO2
- 2021
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized spherical copper particle embedded on oxide matrix (Cunp-Cu2O/SiO2) is synthesized from a low cost chalcopyrite concentrate. The concentrate is reduced by hydrogen at 1323 K, followed by acid leaching to produce Cunp-Cu2O/SiO2. Powder X-ray diffraction confirms the formation of metallic copper as the principal phase along with oxides of silicon and copper. The weight fractions of Cu, SiO2 and Cu2O are 0.565(8), 0.203(2) and 0.232 (3) respectively, as obtained from a three-phase Rietveld refinement. The diameter of copper spheres, rooted on silica, as observed in transmission electron microscopy, is ranging between 4 and 34 nm. Spectroscopic studies, especially Raman spectra, confirm the occurrence of Cu2O. Raman active 2nd overtone at 219 cm−1 appears as the most intense peak. Contribution of SiO2 is clear in Fourier transform infrared spectra. A broad band between 1000 and 1100 cm−1, more specifically at 1080 cm−1 occurs due to Si–O–Si asymmetric stretches. The presence of Cu2O causes photoluminescence peaks to appear in the visible region, corresponding to energy gaps of 0.9 and 1 eV, which indicate the existence of two donor levels below the conduction band. Broad absorption wavelength in the ultraviolet–visible absorption spectra in visible region and low band gap energy of 1.4 eV indicate the possibility of Cunp-Cu2O/SiO2 to be an excellent photocatalytic material. The composite's photocatalytic performance as it is directly derived from the concentrate is quite promising under solar light irradiation. Bromophenol blue (BB) degradation efficiency is 71.26% in 90 min, the photocatalytic kinetics rate is 0.01447 min−1. Characterizations of Cunp-Cu2O/SiO2 as the recycled photocatalyst confirm its photocatalytic stability.
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| 2. |
- Das, Biswanath, et al.
(författare)
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A di‑iron(III) μ-oxido complex as catalyst precursor in the oxidation of alkanes and alkenes
- 2022
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Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- The oxido-bridged diiron(III) complex [Fe2(μ-O)(μ-OAc)(DPEAMP)2](OCH3) (1), based on a new unsymmetrical ligand with an N4O donor set, viz. [2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-((ethylamino)methyl)-4-methylphenol (HDPEAMP)], has been prepared and characterized by spectroscopic methods and X-ray crystallography. The crystal structure of the complex reveals that each Fe(III) ion is coordinated by three nitrogen and three oxygen donors, two of which are the bridging oxido and acetate ligands. Employing H2O2 as a terminal oxidant, 1 is capable of oxidizing a number of alkanes and alkenes with high activity. The catalytic oxidation of 1,2-dimethylcyclohexane results in excellent retention of configuration. Monitoring of the reaction of 1 with H2O2 and acetic acid in the absence of substrate, using low-temperature UV–Vis spectroscopy, suggests the in situ formation of a transient Fe(III)2-peroxido species. While the selectivity and nature of oxidation products implicate a high-valent iron-oxido complex as a key intermediate, the low alcohol/ketone ratios suggest a simultaneous radical-based process.
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| 3. |
- Folkers, Laura C., et al.
(författare)
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Entropy-Driven Incommensurability : Chemical Pressure-Guided Polymorphism in PdBi and the Origins of Lock-In Phenomena in Modulated Systems
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:7, s. 4936-4949
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Tidskriftsartikel (refereegranskat)abstract
- Incommensurate order, in which two or more mismatched periodic patterns combine to make a long-range ordered yet aperiodic structure, is emerging as a general phenomenon impacting the crystal structures of compounds ranging from alloys and nominally simple salts to organic molecules and proteins. The origins of incommensurability in these systems are often unclear, but it is commonly associated with relatively weak interactions that become apparent only at low temperatures. In this article, we elucidate an incommensurate modulation in the intermetallic compound PdBi that arises from a different mechanism: the controlled increase of entropy at higher temperatures. Following the synthesis of PdBi, we structurally characterize two low-temperature polymorphs of the TlI-type structure with single crystal synchrotron X-ray diffraction. At room temperature, we find a simple commensurate superstructure of the TlI-type structure (comm-PdBi), in which the Pd sublattice distorts to form a 2D pattern of short and long Pd-Pd contacts. Upon heating, the structure converts to an incommensurate variant (incomm-PdBi) corresponding to the insertion of thin slabs of the original TlI type into the superstructure. Theoretical bonding analysis suggests that comm-PdBi is driven by the formation of isolobal Pd-Pd bonds along shortened contacts in the distorted Pd network, which is qualitatively in accord with the 18-n rule but partially frustrated by the population of competing Bi-Bi bonding states. The emergence of incomm-PdBi upon heating is rationalized with the DFT-Cemical Pressure (CP) method: the insertion of TlI-type slabs result in regions of higher vibrational freedom that are entropically favored at higher temperatures. High-temperature incommensurability may be encountered in other materials when bond formation is weakened by competing electronic states, and there is a path for accommodating defects in the CP scheme.
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| 4. |
- Guo, Hua, 1990-
(författare)
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Structural characterization of complex inorganic materials using solid-state NMR spectroscopy
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the past decades, advancements in technology have relied greatly on the development of new functional inorganic materials. Detailed structural characterization of these materials is key for the understanding and also prediction of chemical and physical properties. The structural characterization of complex inorganic materials is typically conducted by a combination of multiple methods. Solid-state NMR brings several advantages because it is element-specific, non-destructive and allows local-chemical-structure elucidation for composite materials, disordered and interfacial structures. This thesis focuses on the application of solid-state NMR for structural characterization of two classes of complex inorganic materials. Calcium phosphate cements (CPCs) have been widely applied as bone-substitution materials. The structures of the setting cements are vital for understanding their behaviors in setting and bone-regeneration processes and functions of different additives. In this thesis two types of CPCs, with different additives, were investigated. The different components in the cements could be identified and quantified with solid-state NMR. Correlation spectra were established that helped in probing the structural relationship between different phases. Mixed-anion perovskite compounds AB(O,X)3 (X = N, F, H, OH, etc.) have been intensively investigated because of their unique properties for different applications as introduced by the mixed anion environment for the transition metal component B. Because of the lability of hydride oxyhydrides emerged as versatile precursors for the synthesis of other mixed-anion compounds and oxynitrides are extensively investigated for their photocatalytic activity and dielectric properties. In this thesis the oxyhydrides BaTiO3-xHx and SrVO2H were synthesized and their subsequent conversions to oxynitrides were investigated. Solid-state NMR was used to probe the local chemical environments of H and N incorporated in the perovskite anion substructure. 1H NMR proved especially to be useful in the quantification of H which is very difficult to accomplish by other methods.
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| 5. |
- Koley, Biplab, et al.
(författare)
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Structure and stability of γ1-AuZn2.1 : A γ-brass-related complex phase in the Au-Zn System
- 2020
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Ingår i: Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials. - 2052-5192. ; 76, s. 1109-1116
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Tidskriftsartikel (refereegranskat)abstract
- γ1-AuZn2.1 in the Au-Zn binary system has been synthesized and its structure analyzed by single-crystal X-ray diffraction. It crystallizes in the trigonal space group P31m (No. 157) with ∼227 atoms per unit cell and represents a 3a × 3a × c superstructure of rhombohedrally distorted γ-Au5-x Zn8+y. The structure is largely tetrahedrally closed packed. The formation of γ1-AuZn2.1 can be understood within the framework of a Hume-Rothery stabilization mechanism with a valence electron concentration of 1.68 e/a (valence electrons per atom).
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| 6. |
- Motlochová, Monika, et al.
(författare)
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Highly efficient eco-friendly sodium titanate sorbents of Cs(i), Sr(ii), Co(ii) and Eu(iii) : synthesis, characterization and detailed adsorption study
- 2024
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Ingår i: RSC Advances. - 2046-2069. ; 14:1, s. 743-754
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Tidskriftsartikel (refereegranskat)abstract
- Development of useful all-around materials which can quickly and efficiently adsorb radionuclides in response to environmental radioactive contamination is an urgent research objective. In response to this need, our team developed a simple preparation method for stable sodium titanates which can serve as efficient agents for removal of radionuclides from water. With an emphasis on an environmentally friendly synthesis, the resulting materials were defined by a range of means and methods measuring e.g. pH, ionic strength, contact time or metal ion concentration in order to assess their potential for use and applications as sorbents. The data obtained from measurements revealed rapid removal kinetics (up to 10 minutes), wide range of pH use and high equilibrium capacity. The maximum amount of adsorbed ions as calculated from the Langmuir isotherm was equal to 206.3 mg g−1 for Cs(i), 60.0 mg g−1 for Sr(ii), 50.2 mg g−1 for Co(ii) and 103.4 mg g−1 for Eu(iii), significantly exceeding published data obtained with related materials. The removal mechanism is most likely ion exchange followed by complexation reactions, as indicated by TEM/EDS analyses. Given their extraordinary sorption capacity and facile synthesis under mild conditions, these materials are promising candidates for the efficient removal of radionuclides from aqueous solutions during the clean-up of radioactive pollution in the environment.
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| 7. |
- Motlochová, Monika, et al.
(författare)
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Highly-efficient removal of Pb(II), Cu(II) and Cd(II) from water by novel lithium, sodium and potassium titanate reusable microrods
- 2020
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:7, s. 3694-3704
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report on the efficient removal of heavy metal ions with nanostructured lithium, sodium and potassium titanates from simulated wastewater. The titanates were obtained via a fast, easy and cost effective process based on extraction of sulfate ions from the crystals of titanyl sulfate and their replacement with hydroxyl groups of NaOH, LiOH and KOH solutions leaving the Ti-O framework intact. The as-prepared titanates were carefully examined by scanning and transmission electron microscopy. Furthermore, the effect of contact time, pH, annealing temperature, together with adsorption in real conditions including competitive adsorption and reusability were studied. It was found that the maximum adsorption capacity, as calculated from the Langmuir adsorption model, is up to 3.8 mmol Pb(ii) per g, 3.6 mmol Cu(ii) per g and 2.3 mmol Cd(ii) per g. Based on the characterization results, a possible mechanism for heavy metal removal was proposed. This work provides a very efficient, fast and convenient approach for exploring promising materials for water treatment.
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| 8. |
- Mumbaraddi, Dundappa, et al.
(författare)
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Minority report : Structure and bonding of YbNi3Ga9 and YbCu3Ga8 obtained in gallium flux
- 2022
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 311
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Tidskriftsartikel (refereegranskat)abstract
- The gallides YbNi3Ga9 and YbCu3Ga8 were obtained from flux growth reactions of Yb, various transition metals M, and Ga, to test a stability diagram that predicts the formation of ternary intermetallic phases. The structure of YbNi3Ga9 was redetermined to resolve discrepancies in the literature. For an untwinned crystal of YbNi3Ga9, the ErNi3Al9-type structure was confirmed (space group R32, a = 7.2294(7) Å, c = 27.513(3) Å, Z = 6), giving rise to an ordered arrangement of Yb2Ga3 nets in the stacking sequence. Crystals of YbCu3Ga8 were among the minority formed in the flux growth reaction. YbCu3Ga8 adopts the rare BaHg11-type structure (space group Pm3¯m, a = 8.2818(13) Å, Z = 3), with Cu and Ga atoms assumed to be disordered. As examples of polar intermetallics, these compounds exhibit electron transfer from Yb to Ga atoms, which then form multicentre covalent bonding networks, as confirmed by electronic structure calculations.
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| 9. |
- Nariyangadu, Sesha Bamini, et al.
(författare)
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New nonlinear optical crystal of rhodamine 590 acid phthalate
- 2020
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:33, s. 20863-20873
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and crystal structure of rhodamine 590 acid phthalate (RhAP) have been reported. This novel solid-state rhodamine derivative not only has a longer fluorescence lifetime compared to rhodamine solid-state matrixes where emission is quenched but also possesses strong nonlinear optical characteristics. The static and dynamic first- and second-order hyperpolarizabilities were calculated using the time-dependent density functional theory at the B3LYP/6-31+G∗ level. The computed static values of β and γof RhAP by the X-ray diffraction (XRD) structure were 31.9 × 10-30 and 199.0 × 10-36 esu, respectively. These values were about 62 times larger than the corresponding values in urea, an already well-known nonlinear optical material. The second-order hyperpolarizability of the compound was determined experimentally by measuring the two-photon absorption cross section using intensity-modulated light fields. The reported compound, excitable at near-infrared, exhibited frequency upconversion with the two-photon absorption coefficient enhanced by two orders of magnitude compared to that of the dye solution. Hosting the dye in the solid, at high concentrations, exploits the nonlinearity of the dye itself as well as results in significant excitonic effects including formation of broad exciton band and superradiance.
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| 10. |
- Ponou, Siméon, et al.
(författare)
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Optimization of Chemical Bonding through Defect Formation and Ordering-The Case of Mg7Pt4Ge4
- 2023
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Ingår i: Inorganic Chemistry. - 0020-1669 .- 1520-510X. ; 62:22, s. 8519-8529
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Tidskriftsartikel (refereegranskat)abstract
- The new phase Mg7Pt4Ge4 (Mg8□1Pt4Ge4; □ = vacancy) was prepared by reacting a mixture of the corresponding elements at high temperatures. According to single crystal X-ray diffraction data, it adopts a defect variant of the lighter analogue Mg2PtSi (Mg8Pt4Si4), reported in the Li2CuAs structure. An ordering of the Mg vacancies results in a stoichiometric phase, Mg7Pt4Ge4. However, the high content of Mg vacancies results in a violation of the 18-valence electron rule, which appears to hold for Mg2PtSi. First principle density functional theory calculations on a hypothetical, vacancy-free "Mg2PtGe"reveal potential electronic instabilities at EF in the band structure and significant occupancy of states with an antibonding character resulting from unfavorable Pt-Ge interactions. These antibonding interactions can be eliminated through introduction of Mg defects, which reduce the valence electron count, leaving the antibonding states empty. Mg itself does not participate in these interactions. Instead, the Mg contribution to the overall bonding comes from electron back-donation from the (Pt, Ge) anionic network to Mg cations. These findings may help to understand how the interplay of structural and electronic factors leads to the "hydrogen pump effect"observed in the closely related Mg3Pt, for which the electronic band structure shows a significant amount of unoccupied bonding states, indicating an electron deficient system.
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