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.

Activation of stress-related signalling pathway in human cells upon SiO2 nanoparticles exposure as an early indicator of cytotoxicity

“…These were synthesised via a co-condensation reaction where Rhodamine 6G soluble dye was incorporated into the silica framework during the synthesis of the nanoparticles. It is known that by the incorporation of the dye within the silica framework, the dye release is prevented by the lack of charge transfer which is usually associated with a surface functionalisation of the fluorescent dye [47]. Therefore, in our study when dispersed in biological, or water based solutions no obvious difference between the unlabelled and Rhodamine 6G labelled amorphous SiO 2 NP was found due to the complete amorphous nature of the mesoporous silica.…”

NMR Spectroscopy Can Characterize Proteins Encapsulated in a Sol-Gel Matrix

“…[24][25][26] These findings parallel earlier ones that show negative and neutral (or nearly neutral) solutes are free to tumble when encapsulated, while cationic solutes interact strongly with the anionic silicate walls. 21,[27][28][29][30][31][32] The resolved peaks of SG-encapsulated cyt b 5 and Mb have nearly 2-fold greater linewidths than those of the solution spectra (∼1.6× for cyt b 5 ; ∼1.9× for Mb). There are two likely sources of this increase: magnetic susceptibility dispersion introduced by inhomogeneities in the SG; increases in rotational correlation times (τ c ) caused by encapsulation.…”

Biodegradable composites with improved barrier properties and transparency from the impregnation of PLA to bacterial cellulose membranes

“…Contact angle measurements were additionally carried out to investigate the effect of the incorporated PLA‐PEG on the surface water affinity and results are gathered in Table . Low contact angle values, ranging from 0° to 30°, are characteristic from highly hydrophilic surfaces such as glass or mica, while high contact angle values, between 70° and 90°, are observed for hydrophobic surfaces such as silicone or fluorocarbon polymers . In this case the BC/PLA‐PEG bionanocomposites turned to have more hydrophobic surfaces than the neat BC since it can be observed that the general tendency is an increase on the contact angle values of the bionanocomposites with respect to the neat BC.…”