| 1. |
- Alammar, Tarek, et al.
(författare)
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The Power of Ionic Liquids : Crystal Facet Engineering of SrTiO3 Nanoparticles for Tailored Photocatalytic Applications
- 2021
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Ingår i: Advanced Sustainable Systems. - : Wiley. - 2366-7486. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Sonochemical synthesis of nano-sized SrTiO3 carried out at close to room temperature, in ionic liquids (ILs) allows the tuning of particle size and particle morphology, that is, tracht and habitus, as well as particle aggregation via the choice of the ionic liquids (ILs) as the reaction medium. The nanoparticles demonstrate high performance for photocatalytic water splitting and photodecomposition of organic material. To this end bis(trifluoromethanesulfonyl)amide ([Tf2N](-))-based ILs with cations of different properties with respect to specific interactions with the target material are investigated. Isolated, 15 +/- 1 nm sized nano-spheres of SrTiO3 are observed to form in [C(3)mimOH][Tf2N] ([C(3)mimOH](+) = 1-(3-hydroxypropyl)-3-methylimidazolium). Aggregation of small sized nanoparticles are observed to around 250 +/- 100 nm large cube-like formations in [C(4)mim][Tf2N] ([C(4)mim](+) = 1-butyl-3-methylimidazolium), raspberry-like in [C4Py][Tf2N] ([C4Py](+) butylpyridinium), and ball-like in [P-66614][Tf2N] ([P-66614](+) tetradecyltrihexyl phosphonium). Importantly, the different materials show different performance as photocatalysts. SrTiO3 prepared in [C(4)mim][Tf2N] shows the highest photocatalytic activity for H-2 evolution (1115.4 mu mol h(-1)) when using 0.025 wt% Rh as the co-catalyst, whereas the material prepared in [C(3)mimOH][Tf2N] shows the highest activity for the photocatalytic degradation of methylene blue (88%) under UV irradiation. The different photocatalytic activities can be correlated with the different crystal surface facets expressed in the respective nanosized SrTiO3 material, {110} for material obtained from [C(4)mim][Tf2N], and {100} for material from [C(3)mimOH][Tf2N]. First-principles density functional theory (DFT) calculations are used to support the experimental findings.
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| 2. |
- Kelley, Steven P., et al.
(författare)
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Structural Consequences of Halogen Bonding in Dialkylimidazolium : A New Design Strategy for Ionic Liquids Illustrated with the I-2 Cocrystal and Acetonitrile Solvate of 1,3-Dimethylimidazolium Iodide
- 2020
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:1, s. 498-505
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of 1,3-dimethylimidazolium-2-carboxylate with elemental iodine in acetonitrile rapidly affords crystalline iodide salts of the 1,3-dimethy1-2-iodoimidazolium cation ([C(1)mim-2-I](+)), [C(1)mim-2-I]I.0.5I(2), and [C(1)mim-2-1]I-0.5CH(3)CN, depending on the temperature. Analysis of the two structures shows the significant role of halogen bonding interactions between the cation and anion in the [C(1)mim-2-I]I salts, which reduces the ionicity of the compounds. This observation is backed by theoretical calculations revealing the importance of halogen bonding as a design strategy for ionic liquids (ILs), which, so far, has been underestimated. The halogen bonding is also analyzed in terms of this new design concept for ILs.
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| 3. |
- Namanga, Jude E., et al.
(författare)
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Efficient and Long Lived Green Light-Emitting Electrochemical Cells
- 2020
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 30:33
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Tidskriftsartikel (refereegranskat)abstract
- The combination of high efficiencies and long lifetime in a single light-emitting electrochemical cell (LEC) device remain a major problem in LEC technology, preventing its application in commercial lighting devices. Three green light-emitting cationic iridium-based complexes of the general composition [Ir((CN)-N-<^>)(2)((NN)-N-<^>)][PF6] with 4-Fppy (2-(4-fluorophenyl)pyridinato) as the cyclometalating (CN)-N-<^> ligand and 1,10-phenanthroline (1), 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline, bphen, 2), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuprione, dmbphen, 3) as ancillary (NN)-N-<^> ligands are synthesized and characterized. Computational studies are carried out in order to compare the electronic structure of the three ionic transition metal complexes (iTMCs) and provide insights into their potential as LEC emitter materials. LECs are then fabricated with complexes 1-3. Driven under a pulsed current, they display a high luminance and current and power efficiencies. As the LEC based on complex 2 displays the overall best device performance, including the longest lifetime of 474 h, it is selected for subsequent driving conditions optimization. An extraordinary power efficiency of 25 lm W-1 and current efficiency of 30 cd A(-1) are achieved under optimized operation conditions with reduced current density, resulting in a long device lifetime of 720 h. Altogether, ligand design in iTMCs and optimization of the device driving conditions leads to a significant improvement in LEC performance.
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| 4. |
- Namanga, Jude E., et al.
(författare)
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Fluorinated Cationic Iridium(III) Complex Yielding an Exceptional, Efficient, and Long-Lived Red-Light-Emitting Electrochemical Cell
- 2020
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:9, s. 9271-9277
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Tidskriftsartikel (refereegranskat)abstract
- A carefully designed red-light-emitting iridium (III) cationic complex yields light-emitting electrochemical cells (LECs) with exceptional efficiency and stability [Ir(4Fppy)(2)(biq)][PF6] (4Fppy = 2-(4-fluorophenyl)pyridinato, biq = 2,2'-biquinoline), whose structure was authenticated by single-crystal X-ray diffraction, emits in the red region of light with photoluminescence (upon 360 nm excitation) and electroluminescence maxima at 629 nm. Astonishingly, it is based on a fluorinated ligand, a design concept more commonly used for green emitter materials. Pairing it with a ligand that has comparatively low-lying frontier orbitals allows for a red shift of the band gap. The uncommon electronic structure of the complex allows overcoming the common problem of strong metal-ligand antibonding interactions in the excited state, rendering it extremely stable under operation. The complex displays a high photoluminescence quantum yield of 27.1% giving rise to an extremely efficient LEC with an initial maximum luminance of 326 cd m(-2), current efficiency of 3.26 cd A(-1), and power efficiency of 2.27 Im W-1, surpassing the current state of the art. Remarkably, the efficient red LEC has a lifetime of 167 h when driven under a block-wave pulsed current at a frequency of 1000 Hz, an average current density of 100 A m(-2), and a duty cycle of 50%. Increasing the duty cycle to 75% led to a decrease in the device average voltage, increasing the power efficiency to an exceptional value of 2.97 Im W-1 without compromising the device stability.
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| 5. |
- Renier, Olivier, et al.
(författare)
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Photoisomerization and Mesophase Formation in Azo-Ionic Liquids
- 2020
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:1, s. 214-225
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids present a versatile, highly tunable class of soft functional materials. Aside from being low melting salts, they can be endowed with additional functionalities. In N-alkylimidazolium halides, which are a prominent class of ionic liquids (ILs), the imidazolium cation was linked via an ether-bridge to an azobenzene unit in order to obtain photoresponsive materials through photoinduced trans-cis isomerization. The azobenzene unit, in turn, was modified with electron-donating or -withdrawing groups such as methyl-, tert-butyl-, methoxy-, N,N-dimethylamino, and nitro groups to study their influence on the photoisomerization and phase behavior. Endowing the imidazolium additionally with a long alkyl chain allows the materials to potentially form liquid crystalline (LC) mesophases before melting into the isotropic liquid. All studied compounds qualify as ionic liquids, and all, except for the nitro-compound, show the formation of smectic mesophases melting to the isotropic liquid. The compounds with the bulkiest aliphatic substituent, the tert-butyl, shows the lowest melting point, the largest mesophase window, and an efficient photochemical trans-cis conversion (>90%). In summary, by tuning sterically and electronically the cationic part of ILs, a photoswitchable room temperature liquid crystal could be developed and design guidelines for photoresponsive ionic liquids could be obtained.
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| 6. |
- Smetana, Volodymyr, et al.
(författare)
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Sandwiched Kagomé Lattices in a Coordination Polymer Based on Mixed-Valent Uranium
- 2021
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 21:3, s. 1727-1733
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Tidskriftsartikel (refereegranskat)abstract
- The metal-organic material (UO)-O-V((UO2)-O-VI)(2)(OH)(5)-(Triaz)(2) (Triaz = 1,2,4-triazolate) has been isolated from the reaction of UO2(NO3)(2)center dot 6H(2)O with 1,2,4-triazole in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]). The compound's crystal structure is comprised of planar inorganic layers interconnected by organic linkers into a 3D framework. These layers represent a uranium-based coordination polymer with a Kagome topology that to the best of our knowledge has never been recognized in f-element coordination chemistry.
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