Effect of Dimensionality in Dendrimeric and Polymeric Fluorescent Materials for Detecting Explosives

TitleEffect of Dimensionality in Dendrimeric and Polymeric Fluorescent Materials for Detecting Explosives
Publication TypeJournal Article
Year of Publication2010
AuthorsCavaye, Hamish, Shaw Paul E., Wang Xin, Burn P. L., Lo S. C., and Meredith Paul
Date Published12/2010

Steady-state Stern−Volmer analysis is uniformly used to assess in solution the efficiency of a sensing molecule for a particular analyte. We use a combination of steady-state Stern−Volmer analysis and time-resolved photoluminescence (TRPL) to determine the underlying mechanisms by which fluorescent sensing materials comprised of fluorene-based chromophores sense nitro-based explosive analytes. The ability of two first-generation dendrimers comprised of bifluorene-containing chromophores to sense explosive analytes was compared with the chemically related polymer poly(9,9-di-n-octylfluoren-2,7-diyl). One dendrimer was planar with a single chromophore with the second having four chromophores tetrahedrally arranged around an adamantyl center. All the materials had high photoluminescence quantum yields of around 90% and were able to sense explosive analytes via quenching of their fluorescence. The three-dimensional dendrimer based upon the adamantyl core was found to have the highest Stern−Volmer constants for all the analytes tested with the planar dendrimer also proving to be on average superior to the polymer. The TRPL measurements showed that sensing occurred by a combination of collisional and static quenching with the proportion of collisional quenching being based on the number of aromatic units in the analyte. Steady-state fluorescence polarization anisotropy measurements of the three materials revealed that for the three-dimensional dendrimer an exciton can migrate between all of the chromophores, meaning that an exciton formed on one chromophore of the dendrimer can be quenched by an analyte interacting with a second chromophore. This gives rise to the potential for sensing response amplification and explains its superior performance to the planar dendrimer and polymer.