| 1. |
- Karlsson, Johan, 1984, et al.
(författare)
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Localized controlled drug delivery from mesoporous implants
- 2014
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Ingår i: Technical Proceedings of the 2014 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2014. Washington, DC, United States, 15-18 June 2014. - 9781482258271
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Konferensbidrag (refereegranskat)abstract
- Mesoporous materials possess both a well-defined topography on the nanometer scale, and they may serve as hosts for drugs. In this work, titanium implants coated with mesoporous TiO2 thin films have been evaluated both in vitro and in vivo. Material characterization showed that, long-range ordered mesoporous TiO2, with a pore-size of 6 nm, and a narrow pore-size distribution were obtained. An in vivo study demonstrated that the films were robust enough to withstand the implantation procedure. The in vitro apatite formation experiments showed that formation of apatite was higher on the mesoporous surface compared to its nonporous counterpart. In a separate in vivo study, two osteoporosis drugs, alendronate (ALN) and raloxifene (RLX), were immobilised into the nanoporous oxide films. The in vitro drug release tests carried out showed a sustained release of both drugs. The osteogenic response after 28 days of implantation of the drug-loaded implants showed a significantly improved bone fixation.
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| 2. |
- Martinelli, Anna, 1978, et al.
(författare)
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A H2/O2 Fuel Cell for In situ μ-Raman Measurements. In-depth Characterization of an Ionic Liquid Filled Nafion Membrane
- 2012
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Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 12:2, s. 169-178
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Tidskriftsartikel (refereegranskat)abstract
- We report the design of a H2/O2 (fuel) cell for in situ μ-Raman spectroscopic measurements. The horizontal orientation of the cell is conceived to allow the penetration of the laser beam along the z-axis from one electrode to the other. We show that during in-depth analyses the Raman signal is not significantly lost and the axial resolution is sufficiently good to allow quantitative and qualitative spectral interpretation. We report “proof of principle” tests performed on Nafion membranes swelled with protic ionic liquids to demonstrate the validity of the design and the potentiality of the method. Our results confirm that this experimental setup can efficiently be used to follow structural changes and concentration gradients in the electrolyte of a fuel cell operando. In particular, we have been able to resolve both in time and in space the hydration state of the membrane as well as spatial variations for the coordination shell during a compositional transient state.
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| 3. |
- Martinelli, Anna, 1978, et al.
(författare)
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An investigation of the sol-gel process in ionic liquid/silica gels by time resolved Raman and 1H NMR spectroscopy
- 2012
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Ingår i: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 14:38, s. 13216-13223
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Tidskriftsartikel (refereegranskat)abstract
- We report, by employing time resolved Raman and nuclear magnetic resonance (NMR) spectroscopy, on the gelation process in ionogels. These are prepared from a non-aqueous sol–gel reaction in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C1C6ImTFSI). Raman and NMR spectroscopies are complementarily used to decipher the chemical reactions that occur during synthesis and to clarify the state of the ionic liquid up to, and well beyond, gelation. We find that the ionic liquid concentration affects both the reaction rate and the gelation time (tgel). In addition, NMR and Raman data reveal inherently different roles of the cation and the anion in the gelation process. While the oscillating behavior of the TFSI Raman signature at 740 cm−1 is mainly an effect of solvation and chemical composition, the evolution of the relative chemical shifts (Δδ) of different hydrogen atoms on the imidazolium correlates with gelation, as does the width of the chemical shift of –OH containing groups (δOH). We also observe that in the confined state the TFSI anion preferably adopts the cisoid conformation and experiences a stronger ion–ion interaction.
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| 4. |
- Martinelli, Anna, 1978, et al.
(författare)
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Conformational evolution of TFSI− in protic and aprotic ionic liquids
- 2011
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555.
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Tidskriftsartikel (refereegranskat)abstract
- We here report on the conformational evolution of the bis(trifluoromethanesulfonyl)imide anion (TFSI−) in protic and aprotic TFSI−-based ionic liquids as a function of temperature. The investigation is performed by Raman spectroscopy in the spectral ranges 240-380 cm−1 and 715-765 cm−1, where the interference from bands due to the cations is negligible. The contribution from each TFSI− conformation, i.e. the cisoid (C1) and the transoid (C2), is quantified in order to estimate the enthalpy of conformational change, ΔH, which is found to be in the range 3.4–7.3 kJ/mol in the liquid state. Conformational information is for the first time determined from the 740 cm−1 band, which previously mainly has been used as an indicator of ion-ion interactions. The similarity in ΔH values obtained from the two spectral ranges demonstrates the validity of using also the 740 cm−1 band for the quantification of the TFSI conformational evolution.
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| 5. |
- Martinelli, Anna, 1978
(författare)
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Effects of a Protic Ionic Liquid on the Reaction Pathway during Non-Aqueous Sol-Gel Synthesis of Silica: A Raman Spectroscopic Investigation
- 2014
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 15:4, s. 6488-6503
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Tidskriftsartikel (refereegranskat)abstract
- The reaction pathway during the formation of silica via a two-component "non-aqueou" sol-gel synthesis is studied by in situ time-resolved Raman spectroscopy. This synthetic route is followed with and without the addition of the protic ionic liquid 1-ethylimidazolium bis(trifluoromethanesulfonyl) imide (C-2 HImTFSI) in order to investigate its effect on the reaction pathway. We demonstrate that Raman spectroscopy is suitable to discriminate between different silica intermediates, which are produced and consumed at different rates with respect to the point of gelation. We find that half-way to gelation monomers and shorter chains are the most abundant silica species, while the formation of silica rings strongly correlates to the sol-to-gel transition. Thus, curling up of linear chains is here proposed as a plausible mechanism for the formation of small rings. These in turn act as nucleation sites for the condensation of larger rings and thus the formation of the open and polymeric silica network. We find that the protic ionic liquid does not change the reaction pathway per se, but accelerates the cyclization process, intermediated by the faster inclusion of monomeric species.
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| 6. |
- Martinelli, Anna, 1978, et al.
(författare)
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Insights into the interplay between molecular structure and diffusional motion in 1-alkyl-3-methylimidazolium ionic liquids. A combined PFG NMR and X-ray scattering study.
- 2013
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:15, s. 5510-5517
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Tidskriftsartikel (refereegranskat)abstract
- We report on how the local structure and the diffusional motion change on increased alkyl chain length in 1-alkyl-3- methylimidazolium cation ionic liquids. This study has been performed by combining pulse field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy and Small Angle X-ray Scattering (SAXS) experiments. The cationic side chain length varies from ethyl (n=2) to hexadodecyl (n=16), while the anion is always bis(trifluoromethanesulfonyl)imide (TFSI). We find that the self-diffusivity of the individual ionic species is correlated to the local structure in the corresponding ionic liquid, namely the nano-segregation into polar and non-polar domains. In agreement with previous results, we observe that for relatively short alkyl chains the cations diffuse faster than the anions; however we also note that this difference becomes less evident for longer alkyl chains and a cross-over is identified at n≈8 with the anions diffusing faster than the cations. Our results indicate that this controversial behavior can be rationalized in terms of different type of cation–cation and anion–anion orderings, as revealed by a detailed analysis of the correlation lengths and their dispersion curves obtained from SAXS data. We also discuss the validity of the Stokes-Einstein relation in these ionic liquids and the evolution of the ex- trapolated cationic radius that we find to depend non strictly linearly on n, in agreement with the cation-cation correlation lenghts.
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| 7. |
- Nayeri, Moheb, 1979, et al.
(författare)
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Surface effects on the structure and mobility of the ionic liquid C(6)C(1)ImTFSI in silica gels
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 10:30, s. 5618-5627
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Tidskriftsartikel (refereegranskat)abstract
- We report on how the dynamical and structural properties of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (C(6)C(1)ImTFSI) change upon different degrees of confinement in silica gels. The apparent diffusion coefficients of the individual ions are measured by H-1 and F-19 pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy, while the intermolecular interactions in the ionogels are elucidated by Raman spectroscopy. In addition, the local structure of the ionic liquid at the silica interface is probed by solid-state NMR spectroscopy. Importantly, we extend this study to a wider range of ionic liquid-to-silica molar ratios (x) than has been investigated previously, from very low (high degree of confinement) to very high (liquid-like gels) ionic liquid contents. Diffusion NMR measurements indicate that a solvation shell, with a significantly lower mobility than the bulk ionic liquid, forms at the silica interface. Additionally, the diffusion of the C(6)C(1)Im(+) and TFSI- ions decreases more rapidly below an observed molar ratio threshold (x < 1), with the intrinsic difference in the self-diffusion coefficient between the cation and anion becoming less pronounced. For ionic liquid molar ratio of x < 1, Raman spectroscopy reveals a different conformational equilibrium for the TFSI- anions compared to the bulk ionic liquid, with an increased population of the cisoid isomers with respect to the transoid. Concomitantly, at these high degrees of confinement the TFSI- anion experiences stronger ion-ion interactions as indicated by the evolution of the TFSI- characteristic vibrational mode at similar to 740 cm(-1). Furthermore, solid-state 2D Si-29{H-1} HETCOR NMR measurements establish the interactions of the ionic liquid species with the silica surface, where the presence of adsorbed water results in weaker interactions between Si-29 surface moieties and the hydrophobic alkyl protons of the cationic C(6)C(1)Im(+) molecules.
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| 8. |
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| 9. |
- Yaghini, Negin, 1976, et al.
(författare)
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Effect of water on the transport properties of protic and aprotic imidazolium ionic liquids - an analysis of self-diffusivity, conductivity, and proton exchange mechanism
- 2014
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 16:20, s. 9266-9275
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report on the transport properties of protic and aprotic ionic liquids of the imidazolium cation (C(2)C(1)Im(+) or C(2)HIm(+)) and the TFSI- or TfO- anion as a function of added water. We observe that the self-diffusion coefficient of the ionic species increases upon addition of water, and that the cation diffuses faster than the anion in the entire water concentration range investigated. We also observe that the overall increase of anionic and cationic diffusion coefficients is significant for C(2)HImTfO while it is rather weak for C(2)C(1)ImTFSI, the former being more hydrophilic. Moreover, the difference between cationic and anionic self-diffusivity specifically depends on the structure of the ionic liquid's ions. The degree of ion-ion association has been investigated by comparing the molar conductivity obtained by impedance measurements with the molar conductivity calculated from NMR data using the Nernst-Einstein equation. Our data indicate that the ions are partly dissociated (A(imp)/A(NMR) in the range 0.45-0.75) but also that the degree of association decreases in the order C(2)HImTfO > C(2)HImTFSI approximate to C(2)C(1)ImTfO > C(2)C(1)ImTFSI. From these results, it seems that water finds different sites of interaction in the protic and aprotic ionic liquids, with a strong preference for hydrogen bonding to the -NH group (when available) and a stronger affinity to the TfO anion as compared to the TFSI. For the protic ionic liquids, the analysis of H-1 NMR chemical shifts (upon addition of H2O and D2O, respectively) indicates a water-cation interaction of hydrogen bonding nature. In addition, we could probe proton exchange between the -NH group and deuterated water for the protic cation, which occurs at a significantly faster rate if associated with the TfO anion as compared to the TFSI.
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| 10. |
- Åkesson, Dan, 1970, et al.
(författare)
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Synthesis and Characterization of a cross-linkable polylactic acid based resin
- 2010
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 115:1, s. 480-486
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Tidskriftsartikel (refereegranskat)abstract
- A new biobased polyester resin was developed for thermoset composite applications. The resin is potentially inexpensive and can be produced industrially by relatively simple means. The resin consists of star-shaped methacrylated oligomers of lactic acid (LA). LA oligomers were synthesized in a two-step process: in the first step, oligomers of LA were polymerized by direct condensation of LA. In the second step, the oligomers were end-functionalized by methacrylic anhydride. The resin was characterized by differential scanning calorimetry, Raman spectroscopy, NMR, rubber process analyzer, and TOF-SIMS. Tests show that the resin can be crosslinked into a rigid network within a couple of minutes upon thermal initiation.
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