| 1. |
- An, Rong, et al.
(författare)
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Controlling the nanoscale friction by layered ionic liquid films
- 2020
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 22:26, s. 14941-14952
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Tidskriftsartikel (refereegranskat)abstract
- The nanofriction coefficient of ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), on the surfaces of mica and graphite was investigated using atomic force microscopy (AFM). A pronounced layered spatial distribution was found in the IL film formed on the solid substrates and can be divided into 3 well distinguishable regions exhibiting different physical properties with increasing distance from the substrate. We found that the friction coefficient (μ) increases monotonically as the layering thickness decreases, no matter what the thickness of the bulk IL is. This suggests that the layering assembled IL at solid surfaces is more important than the bulk phase in determining the magnitude of the nanoscale friction. The increase in the friction coefficient as the layering thickness decreases is most likely attributed to the assembled ordered IL layers closer to the substrate surfaces having a greater activation barrier for unlocking the surfaces to allow shear.
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| 2. |
- Fan, Pengpeng, et al.
(författare)
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The effect of nanoscale friction of mesoporous carbon supported ionic liquids on the mass transfer of CO2 adsorption
- 2020
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 22:3, s. 1097-1106
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Tidskriftsartikel (refereegranskat)abstract
- Supported ionic liquids (ILs) are attractive alternatives for CO2 capture and the thickness of supported IL films plays a critical role in the CO2 mass transfer rate. However, the dependence of CO2 uptake on the IL film thickness differs as the system varies. In this work, atomic force microscopy (AFM) is employed to probe the ‘nanofriction coefficient’ to characterize the mobility of ILs at the solid interface, in which, the smaller the nanofriction coefficient, the faster are the ionic mobility and CO2 mass transfer. A monotonic and almost linear relationship for supported IL films is obtained between the resistance of CO2 mass transfer (1/k) and the nanofriction coefficient (μ), avoiding the controversy over the effect of supported IL film thickness on CO2 adsorption. The enhanced mass transfer of CO2 adsorption at IL-solid interfaces is observed at smaller resistance 1/k and friction coefficient μ. The low-friction driven local mobility (diffusion) of ILs at solid interfaces is enhanced, promoting the exchange mixing of the ILs adsorbing CO2 with the ‘blank-clean’ ions of the ILs, and thus accelerating the CO2 mass transfer. The proposed correlation links the nanoscale friction with the mass transfer of CO2 adsorption, providing a fresh view on the design of ultra-low frictional supported ILs for enhanced CO2 capture and separation processes.
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| 3. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Diffusion of Ions in Phosphonium Orthoborate Ionic Liquids Studied by 1H and 11B Pulsed Field Gradient NMR
- 2020
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Ingår i: Frontiers in Chemistry. - : Frontiers Media S.A.. - 2296-2646. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Non-halogenated boron-based ionic liquids (ILs) composed of phosphonium cations and chelated orthoborate anions have high hydrolytic stability, low melting point and exceptional properties for various applications. This study is focused on ILs with the same type of cation, trihexyltetradecylphosphonium ([P6,6,6,14]+), and two orthoborate anions, such as bis(salicylato)borate ([BScB]−) and bis(oxalato)borate ([BOB]−). We compare the results of this study with our previous studies on ILs with bis(mandelato)borate ([BMB]−) and a variety of different cations (tetraalkylphosphonium, dialkylpyrrolidinium and dialkylimidazolium). The ion dynamics and phase behavior of these ILs is studied using 1H and 11B pulsed-field-gradient (PFG) NMR. PFG NMR is demonstrated to be a useful tool to elucidate the dynamics of ions in this class of phosphonium orthoborate ILs. In particular, the applicability of 11B PFG NMR for studying anions without 1H, such as [BOB]−, and the limitations of this technique to measure self-diffusion of ions in ILs are demonstrated and discussed in detail for the first time.
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| 4. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Understanding the Interaction of Boric Acid and CO2 with Ionic Liquids in Aqueous Medium by Multinuclear NMR Spectroscopy
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:1, s. 552-560
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Tidskriftsartikel (refereegranskat)abstract
- Boric acid is known to enhance the kinetics of CO2 absorption by some active aqueous solutions. However, the mechanism of interaction of boric acid with CO2 in the presence of active molecules is not yet fully understood. In this work, the interaction and dynamics of ions in aqueous solutions of functionalized choline-based ionic liquids [N1,1,5,2OH][Threo] and [N1,1,5,2OH][Tau] in the presence of boric acid and CO2 was thoroughly investigated using a multinuclear NMR approach: 13C and 11B NMR spectroscopy, 11B NMR transverse relaxation, and 1H and 11B NMR diffusometry. 13C and 11B NMR spectroscopy revealed the formation of borate-based complexes as a result of a reaction between boric acid and the anions of the ILs at ionic liquid/boric acid molar ratios larger than ca. 0.15. The formation of these complexes and their dynamics were further investigated using 11B relaxation and 1H and 11B pulse-field-gradient (PFG) NMR. Plausible reaction mechanisms of boric acid with the anions of the ILs, formation of the borate complexes, and dissociation of these complexes facilitated by CO2 molecules are suggested.
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| 5. |
- Kanwal, Sehrish, et al.
(författare)
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Poly-thiourea formaldehyde based anticorrosion marine coatings on type 304 stainless steel
- 2020
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 9:2, s. 2146-2153
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, hexamethylene diisocyanate (HMDI) encapsulated poly-thiourea formaldehyde (PTF) (10 wt%) coating was developed in an epoxy-polyamine matrix and their anticorrosion studies on Type SS304 stainless steel substrate have been conducted using electrochemistry techniques. The compact and hydrophobic shell wall of PTF proved to be a potent shell wall material for HMDI encapsulation. The effect of temperature and pH values was found to be decisive factor in the synthesis of microcapsules. The PTF microcapsules were synthesized in acidic condition with a pH value of 3. Over 90% of the core fraction is retained in water after 21 days immersion. However, core content decreased with increasing temperature. The capsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy(SEM), thermogravimetric analysis (TGA) and Electrochemical Impedance spectroscopy (EIS). Scanning electron microscopic analysis depicts the uniform morphology of coating with a particle size in the range of 1.08 μm–22.06 μm. The vibrational band at 2271 cm−1 attributed to NCO signal further endorses the successful encapsulation of HMDI into the PTF capsules. Electrochemical testing on steel specifies the appreciable anticorrosion performance of the synthesized poly thiourea formaldehyde (PTF) coating against artificial sea water.
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| 6. |
- Khan, Inayat Ali, et al.
(författare)
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Effect of Aromaticity in Anion on the Cation–Anion Interactions and Ionic Mobility in Fluorine-Free Ionic Liquids
- 2020
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 124:52, s. 11962-11973
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids (ILs) composed of tetra(n-butyl)phosphonium [P4444]+ and tetra(n-butyl)ammonium [N4444]+ cations paired with 2-furoate [FuA]−, tetrahydo-2-furoate [HFuA]−, and thiophene-2-carboxylate [TpA]− anions are prepared to investigate the effects of electron delocalization in anion and the mutual interactions between cations and anions on their physical and electrochemical properties. The [P4444]+ cations-based ILs are found to be liquids, while the [N4444]+ cations-based ILs are semi-solids at room temperature. Thermogravimetric analysis revealed higher decomposition temperatures and differential scanning calorimetry analysis showed lower glass transition temperatures for phosphonium-based ILs than the ammonium-based counterparts. The ILs are arranged in the decreasing order of their ionic conductivities as [P4444][HFuA] (0.069 mS cm–1) > [P4444][FuA] (0.032 mS cm–1) > [P4444][TpA] (0.028 mS cm–1) at 20 °C. The oxidative limit of the ILs followed the sequence of [FuA]−> [TpA]−> [HFuA]−, as measured by linear sweep voltammetry. This order can be attributed to the electrons’ delocalization in [FuA]− and in [TpA]− aromatic anions, which has enhanced the oxidative limit potentials and the overall electrochemical stabilities.
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| 7. |
- Khan, Inayat Ali, et al.
(författare)
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Fluorine-Free Ionic Liquid-Based Electrolyte for Supercapacitors Operating at Elevated Temperatures
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:27, s. 10212-10221
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Tidskriftsartikel (refereegranskat)abstract
- We synthesized tetra(n-butyl)phosphonium furoate [P4444][FuA] ionic liquid (IL) by the reaction of tetra(n-butyl)phosphonium hydroxide and 2-furoic acid using water as a solvent at room temperature. The thermal stability and phase behavior of the IL are investigated through thermogravimetry (TGA) and differential scanning calorimetry (DSC), while the ionic conductivity measurement is carried out using impedance spectroscopy. Hybrid carbon-based material composed of multi walled carbon nanotubes (MWCNTs) and activated charcoal is fabricated and used as electrodes. The effect of potential scan rate, temperature and voltage on the electrochemical performance of the capacitor is thoroughly investigated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results showed that the internal resistance and specific capacitance are highly dependent on the temperature and voltage, and a high specific capacitance of 141.4 F g−1 (5 mV s−1) from CV and 182 F g−1 (1 A g−1) from GCD at 100 °C is achieved, indicating an excellent electrochemical performance. The capacitor demonstrated 29.0 Wh kg−1 energy density and 13.3 kW kg−1 power density at 20 °C and 3 V potential, while 177 Wh kg−1 energy density and 82 kW kg−1 power density are achieved at higher temperature (100 °C). The FTIR analysis of the capacitor after electrochemical studies confirmed that no changes have occurred in the structure of the IL, indicating high electrochemical stability of the IL for supercapacitor applications in an extended temperature (−20 to 100 °C) and a wide potential range (3 V to 4.6 V).
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| 8. |
- Kim, Injeong, et al.
(författare)
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Investigations into the use of Maleic Anhydride/Sodium Hypophosphite as a Wood Modification Process
- 2020
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Ingår i: Proceedings IRG Annual Meeting 2020. - Stockholm : The International Research Group on Wood Protection.
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Konferensbidrag (refereegranskat)abstract
- The formation of crosslinked bonds between wood constituents is believed to be an effective way to stabilize wood against wet conditions. The possibility to use maleic anhydride (MA) combined with sodium hypophosphite (SHP) as crosslinking agents was studied, using Scots pine sapwood and a model compound. The modified wood showed weight gain and bulking effect after treatment and subsequent Soxhlet extractions, which indicated penetration into the wood cell wall and reaction of the chemicals with the wood constituents. The FTIR spectra confirmed the formation of an ester bond between the wood and MA. Furthermore, a decrease of intensity of band at 1635 cm-1 indicated a reduction of the double bond between carbons in MA after further treatment with SHP, especially at 170 ̊C. Such reactions were studied using monomethyl maleate (MMM) and SHP. The 13C NMR spectra of the reaction product confirmed a reduction of the double bond between carbons. This paper outlines studies undertaken to date, along with outlining aims of ongoing and future work.
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| 9. |
- Mushtaq, Irrum, et al.
(författare)
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Engineering electroactive and biocompatible tetra(aniline)-based terpolymers with tunable intrinsic antioxidant properties in vivo
- 2020
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier. - 0928-4931 .- 1873-0191. ; 108
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Tidskriftsartikel (refereegranskat)abstract
- Under different pathological conditions, high levels of reactive oxygen species (ROS) cause substantial damage to multiple organs. To counter these ROS levels in multiple organs, we have engineered highly potent novel terpolymers. We found that combination of FDA-approved polyethylene glycol, fumaric acid moieties and electroactive tetra(aniline) by varying the content of tetra(aniline) results into a novel drug composition with biologically active tunable intrinsic antioxidant properties. To test tunable intrinsic antioxidative properties of these engineered novel terpolymers, we used alloxan to induce diabetes in rats where ROS generation is known to be higher. The systemic administration of terpolymers to the diabetic rats showed strong electroactive antioxidant behavior which normalized ROS levels, enzymatic antioxidants including superoxide dismutase, catalase, but also reduced glutathione. As a proof-of-principle, we here show TANI based novel drug composition of terpolymers with tunable intrinsic antioxidant effects confirmed in multiple organs.
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| 10. |
- Naz, Sadia, et al.
(författare)
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One-Pot Deconstruction and Conversion of Lignocellulose Into Reducing Sugars by Pyridinium-Based Ionic Liquid–Metal Salt System
- 2020
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Ingår i: Frontiers in Chemistry. - : Frontiers Media S.A.. - 2296-2646. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Constantly decreasing fossil resources and exceeding energy demands are the most alarming concerns now-a-days. The only way out is to develop efficient, safe and economic biomass processing protocols that can lead towards biofuels and fine chemicals. This research is one of such consequences involving the deconstruction and conversion of wheat straw carbohydrate constituents into reducing sugars via one-pot reaction promoted by Lewis acidic pyridinium based ionic liquids (PyILs) mixed with different metal salts (MCl). Various parameters such as the type of metal salt, loading amount of metal salt, time, temperature, particle size of biomass and water content which affect the deconstruction of wheat straw have been evaluated and optimized. Among the studied IL and metal salt systems, the best results were obtained with [BMPy]+CoCl3‒. The dinitrosalicylic acid (DNS) assay was used to determine the percentage of total reducing sugars (TRS) generated during treatment of wheat straw. The deconstructed wheat straw was characterized with various analytical tools i.e. FTIR, SEM and XRD analyses. The ionic liquid‒metal salt system was recycled for subsequent treatment of wheat straw. Statistical parameters were calculated from analysis of variance (ANOVA) at 0.05 level of confidence.
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