ISSN:
1573-4846
Schlagwort(e):
static and time-resolved fluorescence spectroscopy
;
pyrene
;
rhodamine 6G
;
local environment
;
polymer-doped xerogels
;
oligomer-doped xerogels
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract We explore the potential of xerogel composites to tailor the behavior of active dopants that are sequestered within the xerogel. Toward this end, we report on the local dipolarity and dynamics of two fluorescent probes (pyrene and rhodamine 6G, R6G) each co-doped at low concentration directly into a series of binary xerogel composites. The composites that we have investigated are composed of tetraethylorthosilicate (Si(OCH2CH3)4,TEOS) plus one of several organically-modified silanes (ORMOSILs), organic oligomers, or a common surfactant. For convenience we divide these xerogel composites into two classes: (1) xerogels wherein the organic character arises from the addition of an ORMOSIL co-monomer, possessing a non-hydrolyzable organic functional group, that becomes covalently incorporated with in the xerogel and (2) xerogels wherein the organic content is adjusted by adding organic oligomers or a surfactant. Six organically-modified silylalkoxides of the form R′ n Si(OR)4−n were investigated as ORMOSILs. Poly(ethylene glycol), Nafion, and Ionene 6,2 were tested as oligomers. Triton X-100 was used as the surfactant. To estimate the local dipolarity within these composites we used the static fluorescence from pyrene molecules that were sequestered within the composites. These experiments showed that the local dipolarity surrounding the average pyrene molecule can be tuned significantly, but this depends on the actual organic species that one uses to prepare the xerogel composite. Time-resolved fluorescence anisotropy measurements were used to quantify the R6G mobility within the same composites. These results demonstrate that certain organic additive scan be used to adjust the R6G mobility within the xerogel composite.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1008708913243
Permalink
