Comparative study of guest charge-charge interactions within silica sol-gel.
ABSTRACT We investigated the effect of charge-charge interactions on the mobilities of rhodamine 6G (R6G), Nile Red, sulforhodamine B, and Oregon Green 514 (ORG) guest molecules within a silica sol-gel host as the guest charge progressed from positive to neutral to negative. Through classification of the mobility as fixed, tumbling, or intermediate behavior, we were able to distinguish differences in surface attraction as the guest charge was varied. On the basis of our results, an attractive charge (as tested by cationic R6G) does not contribute significantly to mobility within dry films. However, an increase in the cationic influence is observed in water-equilibrated environments. A comparison of ORG in dry and water- and phosphate-buffer-equilibrated films indicates that charge repulsion does significantly increase dye rotational mobility (to a maximum of 24 +/- 3% tumbling molecules). However, in view of the percentage of tumbling molecules found, charge-charge interactions do not appear to be the dominant force controlling guest mobility.
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ABSTRACT: A sea ice dynamics/thermodynamics model is validated using a one-year time series of data from the C-band synthetic aperture radar (SAR) instrument aboard Earth Resources Satellite 1 (ERS-1). Common validation problems using geophysical parameter estimates produced by operational algorithms are avoided by coupling a simple backscatter model to the physical model to generate a time series of estimated SAR backscatter values, which can be directly compared to the observed time series. Comparison of actual and estimated SAR backscatter shows good agreement during the winter and spring seasons. Differences during the summer and early autumn period are attributed to surficial changes, namely wet snow, meltponds, and young ice covered by frost flowers, that are not included in the ice physics model but affect the C-band backscatter. After adding these effects to the backscatter model, very good agreement is observed throughout the year between the sea ice/backscatter model and the ERS-1 time series, with RMS differences about 10% of the full range of backscatter values. The paper demonstrates the utility of the forward simulation approach for model validation and discusses potential future improvements and applicationsGeoscience and Remote Sensing Symposium, 1996. IGARSS '96. 'Remote Sensing for a Sustainable Future.', International; 06/1996
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ABSTRACT: The [Ru(bpy)3]2+ ion was encapsulated in a silica based sol–gel thin film, and the luminescence decay time constant of the photo-excited 3MLCT (metal-ligand-charge-transfer) was examined when this thin film was immersed in water, methanol, ethanol, 2-propanol, and glycerol. The luminescence decays of the films in the methanol, 2-propanol, and glycerol were better explained by a KWW model, while the luminescence decay of film immersed in water and ethanol were both well explained by a single exponential decay. Intriguingly, the dynamics of the dopants immersed in water, ethanol as well as in sol–gel bulk deviated from a single exponential fit and began to better explained by the the KWW model as temperature increased. The energy gap, ΔE(sol–gel film) and ΔE(solution), between the lowest 3MLCT state and atom localized 3 dd state for dopants under the presence of all solvents tested in this study were extracted from the temperature dependence study of the luminescence decay time constant. Generally, the ΔE(sol–gel film) values of ethanol and water were reduced from ΔE(solution), and ΔE(sol–gel film) value in all solvents matched the value of ΔE for sol–gel bulk. The effect on the dynamics in solvent over three weeks was investigated, and the films immersed in water presented the most remarkable monotonic increase in relaxation rates finally approaching the asymptotic value observed in the water solution. This phenomenon was considered to correspond to a trapping environment change due to a hydrophilic interaction through sequential intrusion of water or ethanol solvent into sol–gel pores.Journal of Sol-Gel Science and Technology 07/2007; 43(2):259-268. · 1.66 Impact Factor
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