Analytische Chemie
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- Fluorescent nanoreporters (1) (entfernen)
Background: Fluorescent amplification strategies with nanomaterials are of increasing importance for a wide range of applications in material and life sciences. This includes their use as reporters for optical assays, targeted probes in bioimaging studies and as sensor materials. Some organic dyes with twisted skeleton conformation show enhanced emission upon aggregation (AIE)in contrast to the majority of dyes which reveal aggregation-caused fluorescence quenching (ACQ). Such dyes could be candidates for amplification strategies.
Here we present a series of new hydrophobic pyrrolidinylvinylquinoxaline (PVQ) dyes with different substituents, which are supposed to show AIE. This group of twisted skeleton conformed dyes are emissive in the solid state, as aggregates, and encapsulated in hydrophobic polymer materials.
Results: The PVQ derivatives show strong AIE in ethanol-water-mixtures containing more than 80% water as indicated by the strong increase in fluorescence quantum yields and lifetimes upon dye aggregation and nanoparticle formation. The size of the AIE effect and the observed fluorescence enhancement are in good agreement with DFT- and XRD calculations of the torsion angle between the four different substituents and the planar backbone of the dye. In all cases, particles with diameters smaller than 450 nm were formed. The hydrodynamic diameter of the aggregates was controlled by the water content, with an increasing water content causing a decrease of the hydrodynamic diameter. In the presence of polyelectrolytes or surfactants, μm-sized crystals were obtained. Encapsulation of the dyes in preformed polymer particles provides stabil and strongly emissive nanoparticles.
Conclusion: Based on new PVQ, we yielded highly emissive nanoparticles. The correlation between the torsion angle and the AIE effect underlines structural control of AIE by substitution pattern in this dye class. The loading of a polymer matrix with PVQ resulted in stable nanoparticles with varied surface modification. Applications of these effects in fluorescence assays are currently studied.