Maria J. Lundqvist

Quantum Chemical Calculations of the Influence of Anchor-Cum-Spacer Groups on Femtosecond Electron Transfer Times in Dye-Sensitized Semiconductor Nanocrystals

Electronic properties of dye-sensitized semiconductor nanocrystals, consisting of perylene (Pe) chromophores attached to 2 nm TiO2 nanocrystals via different anchor-cum-spacer groups, have been studied theoretically using density functional theory (DFT) cluster calculations. Approximate effective electronic coupling strengths for the heterogeneous electron-transfer interaction have been extracted from the calculated electronic structures and are used to estimate femtosecond electron-transfer times theoretically. Results are presented for perylenes attached to the TiO2 via formic acid (Pe-COOH), propionic acid (Pe-CH2-CH2-COOH), and acrylic acid (Pe-CH [Formula: see text] CH-COOH). The calculated electron transfer times are between 5 and 10 fs with the formic acid and the conjugated acrylic acid bridges and about 35 fs with the saturated propionic acid bridge. The calculated electron injection times are of the same order of magnitude as the corresponding experimental values and qualitatively follow the experimental trend with respect to the influence of the different substitutions on the injection times.

Computational Study of the Lowest Triplet State of Ruthenium Polypyridyl Complexes Used in Artificial Photosynthesis.

The potential energy surfaces of the first excited triplet state of some ruthenium polypyridyl complexes were investigated by means of density functional theory. Focus was placed on the interaction between the geometrical changes accompanying the photoactivity of these complexes when used as antenna complexes in artificial photosynthesis and dye-sensitized solar cells and the accompanying changes in electronic structure. The loss process (3)MLCT --> (3)MC can be understood by means of ligand-field splitting, traced down to the coordination of the central ruthenium atom.

Different effects of deep inspirations on central and peripheral airways in healthy and allergen-challenged mice

BackgroundDeep inspirations (DI) have bronchodilatory and bronchoprotective effects in healthy human subjects, but these effects appear to be absent in asthmatic lungs. We have characterized the effects of DI on lung mechanics during mechanical ventilation in healthy mice and in a murine model of acute and chronic airway inflammation.MethodsBalb/c mice were sensitized to ovalbumin (OVA) and exposed to nebulized OVA for 1 week or 12 weeks. Control mice were challenged with PBS. Mice were randomly selected to receive DI, which were given twice during the minute before assessment of lung mechanics.ResultsDI protected against bronchoconstriction of central airways in healthy mice and in mice with acute airway inflammation, but not when OVA-induced chronic inflammation was present. DI reduced lung resistance induced by methacholine from 3.8 ± 0.3 to 2.8 ± 0.1 cmH2O·s·mL-1 in healthy mice and 5.1 ± 0.3 to 3.5 ± 0.3 cmH2O·s·mL-1 in acute airway inflammation (both P < 0.001). In healthy mice, DI reduced the maximum decrease in lung compliance from 15.9 ± 1.5% to 5.6 ± 0.6% (P < 0.0001). This protective effect was even more pronounced in mice with chronic inflammation where DI attenuated maximum decrease in compliance from 44.1 ± 6.6% to 14.3 ± 1.3% (P < 0.001). DI largely prevented increased peripheral tissue damping (G) and tissue elastance (H) in both healthy (G and H both P < 0.0001) and chronic allergen-treated animals (G and H both P < 0.0001).ConclusionWe have tested a mouse model of potential value for defining mechanisms and sites of action of DI in healthy and asthmatic human subjects. Our current results point to potent protective effects of DI on peripheral parts of chronically inflamed murine lungs and that the presence of DI may blunt airway hyperreactivity.

Quantum-chemical calculations of dye-sensitized semiconductor nanocrystals

Quantum chemical calculations providing detailed information of dye-sensitized semiconductor nanocrystals are presented. The calculations are used to elucidate both structural and electronic properties of photoelectrochemical devices, such as environmentally friendly Dye-Sensitized Solar Cells (DSSCs), at the molecular level. Quantum chemical calculations have recently been performed on both organic and organometallic dye molecules attached to titanium dioxide (TiO2) nanocrystals via different anchor and spacer groups. Strategies to make accurate quantum chemical calculations, e.g. at the DFT level of theory, on increasingly realistic models of such dye-sensitized semiconductor interfaces are presented. The ability of different anchor and spacer groups to act as mediators of ultrafast photo-induced electron injection from the dye molecules into the semiconductor nanocrystals is, in particular, discussed in terms of calculated electronic coupling strengths, and direct comparisons with experimental information are made whenever possible. Progress in the development of multi-scale simulation techniques using so called reactive force fields is illustrated for dye-sensitized solar cell systems.