| 1. |
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| 2. |
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| 3. |
- Maurina Morais, Eduardo, 1989, et al.
(författare)
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Solvent-free synthesis of protic ionic liquids. Synthesis, characterization and computational studies of triazolium based ionic liquids
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 360
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Tidskriftsartikel (refereegranskat)abstract
- A series of triazolium and imidazolium based protic ionic liquids were synthesized using a solvent-free method designed to address several limitations encountered with other commonly used methods. Using this method, pure (98–99% m/m) and dry (128–553 ppm of water) protic ionic liquids were synthesized (in a laboratory scale) without the need for purification methods that require heating the ionic liquid, hence avoiding the common issue of thermal decomposition. This method was also designed to allow for the accurate measurement of acid and base, and for the controlled mixing of both compounds, which is essential to avoid producing impure protic ionic liquids with excess of either acid or base. The system is constructed of only glass and chemically resistant polymer (PTFE and PVDF) parts, which avoid other contaminants that can result from unwanted reactions involving the reagents with common laboratory tools (metallic objects, paper, plastic, etc.). This process is described in detail in the paper as well as in a video. The resulting ionic liquids were carefully analyzed by spectroscopic and thermal methods designed to avoid water absorption, which is known to affect their properties. To complement this experimental characterization, computational chemistry tools were used to assess the ionic liquids’ properties, as well as to assign vibrational modes.
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| 4. |
- Laarz, Eric, et al.
(författare)
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Colloidal processing of Al2O3-based composites reinforced with TiN and TiC particulates, whiskers and nanoparticles
- 2001
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 21:8, s. 1027-1035
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Tidskriftsartikel (refereegranskat)abstract
- A colloidal processing route has been developed for the preparation of dense and homogeneous Al2O3–TiN/TiC composites. The dispersion and rheological properties of mixtures of TiN or TiC particulates and Al2O3 particles were investigated using electrokinetics and steady-shear rheology. We found that well-dispersed aqueous suspensions with low viscosity could be prepared by adding a poly(acrylic acid) dispersant and controlling pH in the alkaline range. This processing scheme was also suitable for preparation of whisker and nanoparticle composite suspensions. The alumina-based composite suspensions with a secondary-phase concentration of 25 vol.% were freeze-granulated and hot-pressed, and the resulting bodies were fully densified with well-dispersed secondary phases. Homogeneous Al2O3–TiN nanoparticle composites could only be prepared with additions of up to 5 vol.% nanoparticles; higher additions resulted in agglomeration and subsequent grain growth of the nanoparticles.
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| 5. |
- Co, Michelle, 1975-, et al.
(författare)
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Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure
- 2012
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 716, s. 40-48
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Tidskriftsartikel (refereegranskat)abstract
- Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and El 80, contained birch bark extracts obtained after extraction at 80 and 180 degrees C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 degrees C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an electrochemical detector, were used to determine the antioxidant capacity of the processed samples. The results obtained with the different techniques were compared to assess the yield of the extraction and degradation processes. In addition, an online hyphenated system comprising high performance liquid chromatography coupled to diode-array; electrochemical; and tandem mass spectrometric detection (HPLC-DAD-ECD-MS/MS) was used to study the compositions of the extracts in more detail. The results for the samples processed at 80 degrees C showed that the extraction reached a steady-state already after 5 min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180 degrees C, on the other hand, gave rise to partly degraded extracts with a multitude of peaks in both the diode array and electrochemical detectors, and a higher antioxidant capacity compared to for the extracts obtained at 80 degrees C. It is concluded that HPLC-DAD-ECD is a more appropriate technique for the determination of antioxidants than the DPPH assay. The mass spectrometric results indicate that one of the extracted antioxidants, catechin, was isomerised to its diastereoisomers; (+)-catechin, (-)-catechin, (+)-epicatechin, and (-)-epicatechin.
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| 6. |
- Rahm, Martin, et al.
(författare)
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The Molecular Surface Structure of Ammonium and Potassium Dinitramide : A Vibrational Sum Frequency Spectroscopy and Quantum Chemical Study
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:21, s. 10588-10596
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational sum frequency spectroscopy (VSFS) and quantum chemical modeling have been employed to investigate the molecular surface structure of ammonium and potassium dinitramide (ADN and KDN) crystals. Identification of key vibrational modes was made possible by performing density functional theory calculations of molecular clusters. The surface of KDN was found to be partly covered with a thin layer of the decomposition product KNO3, which due to its low thickness was not detectable by infrared and Raman spectroscopy. In contrast, ADN exhibited an extremely inhomogeneous surface, on which polarized dinitramide anions were present, possibly together with a thin layer of NH4NO3. The intertwined use of theoretical and experimental tools proved indispensable in the analysis of these complex surfaces. The experimental verification of polarized and destabilized dinitramide anions stresses the importance of designing surface-active polymer support, stabilizers, and/or coating agents, in order to enable environmentally friendly ADN-based solid-rocket propulsion.
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| 7. |
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| 8. |
- Sahlberg, Martin, 1981-
(författare)
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Light-Metal Hydrides for Hydrogen Storage
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Demands for zero greenhouse-gas emission vehicles have sharpened with today’s increased focus on global warming. Hydrogen storage is a key technology for the implementation of hydrogen powered vehicles. Metal hydrides can claim higher energy densities than alternative hydrogen storage materials, but a remaining challenge is to find a metal hydride which satisfies all current demands on practical usability. Several metals store large amounts of hydrogen by forming a metal hydride, e.g., Mg, Ti and Al. The main problems are the weight of the material and the reaction energy between the metal and hydrogen. Magnesium has a high storage capacity (7.6 wt.% hydrogen) in forming MgH2; this is a slow reaction, but can be accelerated either by minimizing the diffusion length within the hydride or by changing the diffusion properties. Light-metal hydrides have been studied in this thesis with the goal of finding new hydrogen storage compounds and of gaining a better understanding of the parameters which determine their storage properties. Various magnesium-containing compounds have been investigated. These systems represent different ways to address the problems which arise in exploiting magnesium based materials. The compounds were synthesized in sealed tantalum tubes, and investigated by in situ synchrotron radiation X-ray powder diffraction, neutron powder diffraction, isothermal measurements, thermal desorption spectroscopy and electron microscopy. It is demonstrated that hydrogen storage properties can be improved by alloying magnesium with yttrium or scandium. Mg-Y-compounds decompose in hydrogen to form MgH2 nano-structures. Hydrogen desorption kinetics are improved compared to pure MgH2. The influence of adding a third element, gallium or zinc has also been studied; it is shown that gallium improves hydrogen desorption from YH2. ScAl1-xMgx is presented here for the first time as a hydrogen storage material. It absorbs hydrogen by forming ScH2 and Al(Mg) in a fully reversible reaction. It is shown that the hydrogen desorption temperature of ScH2 is reduced by more than 400 °C by alloying with aluminium and magnesium.
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| 9. |
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| 10. |
- Sauer, Christopher, 1993
(författare)
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Green Aromatics: Catalytic Valorisation of bio-derived 2,5-dimethylfuran over Zeolites and Zeotypes
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis discusses the use of biomass as a potentially green feedstock for the chemical industry in the urgent shift away from fossil resources. I elaborate on reasons why we cannot afford to burn virgin biomass for energy production, among them a variety of ecosystem services that forests and other lands provide. In addition, the utilisation of biomass should be focused on products that sequester and lock away carbon for more extended periods, e.g. timber, materials and chemicals. In particular, biomass can be used as an alternative "carbon neutral" feedstock for the chemical industry, where we can preserve the already existing chemical complexity in the bio-based molecules. One example is the upgrading of furans to benzene, toluene and xylene (BTX) aromatics with the help of zeolite catalysis. These aromatics are important commodity chemicals, where the shift to a bio-based resource could make use of already existing knowledge, catalyst and production infrastructure. However, research is necessary to understand these new feedstock molecules and their interaction with the catalysts and to enable the design of applicable catalysts. In order to study the interaction of the furans, in particular 2,5-dimethylfuran (2,5-dmf), I describe and discuss the development of an analytical methodology that utilises infrared spectroscopy and mass spectrometry for the on-line identification and quantification of product molecules during catalytic reactions. This on-line analysis method is then applied to the catalytic conversion of 2,5-dmf to aromatics over a range of zeolite and zeotype catalysts. In-depth studies with ammonia as a probe molecule of the catalytic active acid sites, as well as temperature programmed experiments with ammonia and 2,5-dmf give insights into product distribution, selectivity changes and deactivation of the catalyst. For example, olefins and aromatics are initially preferred products, while with increasing time on stream, the isomerisation of 2,5-dmf becomes dominant. The incorporation of Ga into the zeotype framework, resulting in a Ga-Silicate, shows how targeted catalyst design can increase overall aromatics production. This catalyst is also suitable for selective isomerisation of 2,5-dmf to 2,4-dimethylfuran, which has a rare substitution pattern. Finally, itwas found that the most valuable of BTX, p -xylene, can be produced more selectively when 2,5-dmf is pre-adsorbed onto zeolite ZSM-5 and then released during a temperature programmed product desorption.
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| 11. |
- Rickaby, Rosalind E. M., et al.
(författare)
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Perturbing phytoplankton : response and isotopic fractionation with changing carbonate chemistry in two coccolithophore species
- 2010
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Ingår i: Climate of the Past. - : Copernicus Publications on behalf of the European Geosciences Union. - 1814-9324 .- 1814-9332. ; 6, s. 771-785
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Tidskriftsartikel (refereegranskat)abstract
- All species of coccolithophore appear to respond to perturbations of carbonate chemistry in a different way. Here, we show that the degree of malformation, growthrate and stable isotopic composition of organic matter and carbonate produced by two contrasting species of coccolithophore (Gephyrocapsa oceanica and Coccolithus pelagicusssp. braarudii) are indicative of differences between their photosynthetic and calcification response to changing DIC levels (ranging from 1100 to 7800 μmol kg−1) at constant pH (8.13±0.02). Gephyrocapsa oceanica thrived under all conditions of DIC, showing evidence of increased growth rates at higher DIC, but C. braarudii was detrimentally affected at high DIC showing signs of malformation, and decreased growth rates. The carbon isotopic fractionation into organic matter and the coccoliths suggests that C. braarudii utilises a common internal pool of carbon for calcification and photosynthesis but G. oceanica relies on independent supplies for each process. All coccolithophores appear to utilize bicarbonate as their ultimate source of carbon for calcification resulting in the release of a proton. But, we suggest that this proton can be harnessed to enhance the supply of CO2(aq) for photosynthesis either from a large internal HCO−3 pool which acts as a pH buffer (C. braarudii), or pumped externally to aid the diffusive supply of CO2 across the membrane from the abundant HCO−3 (G. oceanica), likely mediated by an internal and external carbonic anhydrase respectively. Our simplified hypothetical spectrum of physiologies may provide a context to understand different species response to changing pH and DIC, the species specific Ep and calcite “vital effects”, as well as accounting for geological trends in coccolithophore cell size.
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| 12. |
- Chajara, Khalil, et al.
(författare)
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The reagent-free, microwave-assisted purification of carbon nanotubes
- 2010
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 34:10, s. 2275-2280
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a microwave-assisted, reagent-free method for the efficient primary purification of MW and SW carbon nanotubes that is extremely fast compared to previously reported processes. The treatment dissociates and disperses non-nanotube carbon in an organic solvent to yield very pure carbon nanotubes within a few minutes of heating and a simple filtration, without the involvement of acidic/oxidative reagents. According to thermogravimetric analysis, Raman and IR spectroscopy, as well as scanning and transmission electron microscopy, the process yields pure nanotubes with a low degree of defects.
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| 13. |
- Dopieralski, Przemyslaw D., et al.
(författare)
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Hydration of NaHCO3, KHCO3, (HCO3-)(2), HCO3- and CO32- from molecular dynamics simulation and speed of sound measurements
- 2011
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 507:1-3, s. 89-95
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Tidskriftsartikel (refereegranskat)abstract
- Car-Parrinello molecular dynamics and acoustic method have been applied to determine the hydration of HCO3- and CO32- ions in aqueous solution. From CPMD simulations the hydration numbers are 5.3 and 8.5 for the HCO3- and CO32- ions, respectively. From speed of sound and density measurements the hydration numbers for HCO3- and CO32- are 5.5 and 10.2, respectively. Our attempt to answer the old question concerning the status of HCO3 in solution quite well support the earlier spectroscopic results that no (HCO3)(2) is present in the solution but the existence of the minor amount of dimers cannot be definitely excluded.
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| 14. |
- Grennberg, Helena, et al.
(författare)
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Functionalization and Area-Selective Deposition of Magnetic Carbon-Coated Iron Nanoparticles from Solution
- 2011
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Ingår i: Journal of Nanotechnology. - : Hindawi publishing. - 1687-9503 .- 1687-9511. ; , s. 342368-
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Tidskriftsartikel (refereegranskat)abstract
- A route to area-selective deposition of carbon-coated iron nanoparticles, involving chemical modification of the surface of the particles, is described. Partial oxidative etching of the coating introduces carboxylic groups, which then are esterified. The functionalized particles can be selectively deposited on the Si areas of Si/SiO2 substrates by a simple dipping procedure. Nanoparticles and nanoassemblies have been analyzed using SEM, TEM, and XPS.
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| 15. |
- Harsanyi, I., et al.
(författare)
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On the hydration structure of LiCl aqueous solutions : A Reverse Monte Carlo based combination of diffraction data and Molecular Dynamics simulations
- 2011
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322 .- 1873-3166. ; 158:1, s. 61-67
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Tidskriftsartikel (refereegranskat)abstract
- Reverse Monte Carlo (RMC) calculations have been carried out on aqueous LiCl solutions at several concentrations, comparing experimental X-ray and neutron diffraction data with partial radial distribution functions (prdf) from Molecular Dynamics (MD) simulations based on conventional ion-ion, ion-water, and water-water pair potentials. The RMC calculations indicate that the hydration shell of the Li+ ions could be even more structured than computer simulations predict, containing at high concentrations unusually few water molecules, of the order of 2 to 3. Concerning the consistency between the structures based on potential models and diffraction data: the ion-water partial radial distribution functions (prdf) from MD are found to be consistent with the experimental data whereas the water-water and ion-ion partials are more problematic. The most serious deficiency is that at high salt concentrations the O-O prdf cannot be made consistent with the present X-ray diffraction data.
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| 16. |
- Hollmark, Håkan M., et al.
(författare)
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Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O2
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:8, s. A962-A966
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the charge-state behavior of the Li-ion battery cathode material LixNi(0.65)Co(0.25)Mn(0.1)O(2) as observed by X-ray absorption spectroscopy (XAS) and resonant soft X-ray emission (RSXE). A set of six identical Li//LixNi0.65Co0.25Mn0.1O2 batteries has been cycled and is studied in different states of charge in the range of x = 1.0, ... ,0.2 before disassembly in an Ar glove box. Site and symmetry selective information about the electronic structure of the conduction and valence bands reveals that Ni as well as Co ions participate in the uptake and release of the extra electron charge that the inserted Li ions provide, but the Ni ion is much less than expected. The net amount of charge on the oxygen varies approximately 0.24 charge units in the range of x, and dramatic changes in the hybridization are evident in XAS and in particular in RSXE at the O K edge. We attribute this to a strong screening behavior of the Li ions between the oxide layers. Structural integrity effects limit the extraction of Li ions to a value of about x = 0.2-0.4. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454739] All rights reserved.
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| 17. |
- Kam, Kinson C., et al.
(författare)
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Synthesis and electrochemical properties of nanostructured Li(2)FeSiO(4)/C cathode material for Li-ion batteries
- 2011
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 192:1, s. 356-359
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured Li(2)FeSiO(4)/C was synthesized by high-energy ball-milling and the amorphous citrate-assisted techniques. Similar redox behaviour is observed for samples prepared by the amorphous citrate-assisted route followed by a 4 h heat treatment: 0.3 V polarization and more sloping behaviour was observed when cycling between 2.0 V and 3.7 V at 60 degrees C; lower capacity fade is also observed compared to Li(2)FeSiO(4)/C prepared by the solid-state reaction technique. A discharge capacity of 102 mA h g(-1) is obtained for samples prepared by the high-energy ball-milling method, while capacities decrease from 95 to 77 mA h g(-1) using the amorphous citrate method for heat-treatment times increasing successively from 4 h to 18 h.
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| 18. |
- Lewin, Erik, et al.
(författare)
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Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
- 2009
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Ingår i: Plasma Processes and Polymers. - : WILEY-VCH Verlag GmbH & Co. - 1612-8850. ; 6:S1, s. S928-S934
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite nc-TiC/a-C coatings were prepared by non-reactive magnetron sputtering in industrial scale equipment, under varying deposition conditions in order to investigate upscaling and possible industrialisation. The coatings were found to have similar microstructure and performance compared to previous laboratory scale experiments. The samples were characterised with XRD, XPS and SEM as well with ball-on-disc, nanoindentation and electrical measurements. Coatings containing a small fraction of a-C matrix phase were found to have promising both electrical properties (rho < 400 mu Omega cm and contact resistances down to 0.34 m Omega at 40 N) and tribological properties (f < 0.3 for 10 000 laps).
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| 19. |
- Li, Shu-Ming, et al.
(författare)
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Rapid microwave-assisted preparation and characterization of cellulose-silver nanocomposites
- 2011
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 83:2, s. 422-429
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Tidskriftsartikel (refereegranskat)abstract
- A simple rapid and efficient microwave-assisted synthesis of cellulose-silver nanocomposites with silver nanoparticles homogeneously dispersed in the cellulose matrix using cellulose solution AgNO3 and ascorbic acid in N N-dimethylacetamide (DMAc) is reported The cellulose solution was prepared by the dissolution of microcrystalline cellulose in a solvent system of lithium chloride (LiCl)/DMAc The effects of the microwave heating times and ascorbic acid concentration on the nanocomposites were investigated The microstructure size morphology and thermal properties of these nanocomposites were analyzed with X-ray diffraction (XRD) Fourier transform infrared (FT-IR) thermogravimetric analysis (TG) differential scanning calorimetric analysis (DSC) and scanning electron microscopy (SEM) The results revealed that the ascorbic acid concentration played an important role in the phase of the nanocomposites This work provided a promising way to prepare cellulose-silver nanocomposites with good dispersity.
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| 20. |
- Liivat, Anti, et al.
(författare)
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Li-ion migration in Li(2)FeSiO(4)-related cathode materials : A DFT study
- 2011
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 192:1, s. 58-64
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Tidskriftsartikel (refereegranskat)abstract
- The orthosilicate family of materials Li(2)MSiO(4) for M = Fe, Mn and Co are coming to be seen as potentially cheap cathode materials for large-scale Li-ion batteries, not least through the possibility for significant capacity gains if more than one Li-ion can be removed per formula unit. To gain insights into possible Li-ion migration pathways and diffusion barriers for Li-ions, model systems for Li(x)FeSiO(4)(x approximate to 1.2) are here studied using the Density Functional Theory (DFT) approach. Li-ion and ion-vacancy migration barriers are calculated for a number of model systems. The results help explain why the Li/Fe site-mixing observed during electrochemical cycling of Li(2)FeSiO(4) does not lead to any noticeable loss in cell performance, despite the increased tortuosity introduced into the Li-migration pathways by this ion-mixing process.
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| 21. |
- Lu, Zhansheng, et al.
(författare)
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SOx on ceria from adsorbed SO2
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:18, s. 184703-
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Tidskriftsartikel (refereegranskat)abstract
- Results from first-principles calculations present a rather clear picture of the interaction of SO2 with unreduced and partially reduced (111) and (110) surfaces of ceria. The Ce3+/Ce4+ redox couple, together with many oxidation states of S, give rise to a multitude of SOx species, with oxidation states from + III to + VI. SO2 adsorbs either as a molecule or attaches via its S-atom to one or two surface oxygens to form sulfite (SO32-) and sulfate (SO42-) species, forming new S-O bonds but never any S-Ce bonds. Molecular adsorption is found on the (111) surface. SO32- structures are found on both the (111) and (110) surfaces of both stoichiometric and partially reduced ceria. SO42-structures are observed on the (110) surface together with the formation of two reduced Ce3+ surface cations. SO2 can also partially heal the ceria oxygen vacancies by weakening a S-O bond, when significant electron transfer from the surface (Ce4f) into the lowest unoccupied molecular orbital of the SO2 adsorbate takes place and oxidizes the surface Ce3+ cations. Furthermore, we propose a mechanism that could lead to monodentate sulfate formation at the (111) surface.
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| 22. |
- Nyström, Gustav, et al.
(författare)
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A Nanocellulose Polypyrrole Composite Based on Microfibrillated Cellulose from Wood
- 2010
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society. - 1520-6106 .- 1520-5207. ; 114:12, s. 4178-4182
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that it is possible to coat the individual fibers of wood-based nanocellulose with polypyrrole using in situ chemical polymerization to obtain an electrically conducting continuous high-surface-area composite. The experimental results indicate that the high surface area of the water dispersed material, to a large extent, is maintained upon normal drying without the use of any solvent exchange. Thus, the employed chemical polymerization of polypyrrole on the microfibrillated cellulose (MFC) nanofibers in the hydrogel gives rise to a composite, the structure of which—unlike that of uncoated MFC paper—does not collapse upon drying. The dry composite has a surface area of 90 m2/g and a conductivity of 1.5 S/cm, is electrochemically active, and exhibits an ion-exchange capacity for chloride ions of 289 C/g corresponding to a specific capacity of 80 mAh/g. The straightforwardness of the fabrication of the present nanocellulose composites should significantly facilitate industrial manufacturing of highly porous, electroactive conductive paper materials for applications including ion-exchange and paper-based energy storage devices.
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| 23. |
- Ottosson, Niklas, et al.
(författare)
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On the Origins of Core-Electron Chemical Shifts of Small Biomolecules in Aqueous Solution : Insights from Photoemisson and ab Initio Calculations of Glycine(aq)
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 133:9, s. 3120-3130
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Tidskriftsartikel (refereegranskat)abstract
- The local electronic structure of glycine in neutral, basic, and acidic aqueous solution is studied experimentally by X-ray photoelectron spectroscopy and theoretically by molecular dynamics simulations accompanied by first-principle electronic structure and spectrum calculations. Measured and computed nitrogen and carbon is binding energies are assigned to different local atomic environments, which are shown to be sensitive to the protonation/deprotonation of the amino and carboxyl functional groups at different pH values. We report the first accurate computation of core-level chemical shifts of an aqueous solute in various protonation states and explicitly show how the distributions of photoelectron binding energies (core-level peak widths) are related to the details of the hydrogen bond configurations, i.e. the geometries of the water solvation shell and the associated electronic screening. The comparison between the experiments and calculations further enables the separation of protonation-induced (covalent) and solvent-induced (electrostatic) screening contributions to the chemical shifts in the aqueous phase. The present core-level line shape analysis facilitates an accurate interpretation of photoelectron spectra from larger biomolecular solutes than glycine.
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| 24. |
- Sellappan, Raja, 1981, et al.
(författare)
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Preparation and characterization of TiO2/carbon composite thin films with enhanced photocatalytic activity
- 2011
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Ingår i: Journal of Molecular Catalysis A. - : Elsevier BV. - 1381-1169 .- 1873-314X. ; 335:1-2, s. 136-144
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Tidskriftsartikel (refereegranskat)abstract
- Composite TiO2/carbon thin films prepared by physical vapor deposition techniques on fused silica substrates show enhanced photocatalytic activity towards decomposition of methanol to CO2 and water, as compared to pure TiO2 films of similar thickness. Raman and XRD measurements confirm that annealed TiO2 films exhibit anatase structure while the carbon layer becomes graphitic. Characteristic for the composite films is an enhanced optical absorption in the visible range. The presence of the carbon film causes a shift of the TiO2 absorption edge and modifies its grain size to be smaller. We hypothesize that the observed enhancement of photocatalytic activity is due to synergy effects at the carbon/TiO2 interface, resulting in smaller titania crystallite size and anisotropic charge carrier transport, which in turn reduces their recombination probability.
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| 25. |
- Zadin, Vahur, et al.
(författare)
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Finite element modelling of ion transport in the electrolyte of a 3D-microbattery
- 2011
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 192:1, s. 279-283
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical model describing ionic transport in a 3D-microbattery (3D-MB) electrolyte is developed here using finite element methodology. The model is then exploited to study a 3D-MB based on an interdigitated plate ("trench") architecture for a 10 pm-thick electrolyte layer separating 10 mu m-thick graphite anode and LiCoO(2) cathode plates. The effect of varying plate length, end-shape and electronic conductivity is also modelled. It is shown that the 3D-MB architecture gives rise to qualitatively non-uniform current densities, leading to sub-optimal surface utilization. This can, in turn, be optimized by varying electrode geometries and/or material properties.
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