Water soluble dendritic structures with significant two-photon absorption (TPA) properties in the biological spectral window (700-1100 nm) are of particular interest for several biomedical applications [1]. As fluorescent probes for bioimaging, in particular, dendrimeric nano-objects with high two-photon brilliance (?2?) are required. The one-photon photophysical characterization of newly designed organic dots is thus important to determine their emissive properties and to disentangle their dependence on environmental aspects such as solvent polarity and aggregation induced effects. We report here on the one-photon characterization of a series of newly designed dendrimers based on a phosphorous based scaffold linked to push-push fluorophores, decorated with cationic groups on the periphery in order to achieve hydrophilicity. Dendrimers of generation 1 up to 3 containing two different fluorophores have been studied. The number of peripheral charges varies between 24 and 48 (Figure 1). Detailed steady-state and time-resolved spectroscopic investigations have been performed on the dendrimers in solvents of different polarity, with reference to monomer fluorophores chosen as models. Only one dendrimer show emission features (quantum yield and lifetime) similar to those of the model, whereas all the other dendrimers display an important reduction in the quantum yield in all solvents, with a trend not directly related to the polarity of the medium. In these cases the fluorescence decays show bi-exponential behavior, with one of the lifetimes very similar to that of parent model and the other one much shorter. The reduction of the emission quantum yield and the decay behavior in the dendrimers are discussed on the basis of thermodynamic grounds and on the analysis of aggregation effects, where both intra-molecular and inter-molecular interactions are taken into consideration. [1] Mongin, O.; Rouxel, C.; Vabre, J.-M.; Mir, Y.; Pla-Quintana, A.; Wei, Y.; Caminade, A.-M.; Majoral, J.-P.; Blanchard-Desce, M. Proc. SPIE-Int. Soc. Opt. Eng. 2009, 7403, 740303/1-740303/12.
Photophysical characterization of peripherally charged dendrimers designed for two-photon absorption
B Ventura;L Flamigni
2014
Abstract
Water soluble dendritic structures with significant two-photon absorption (TPA) properties in the biological spectral window (700-1100 nm) are of particular interest for several biomedical applications [1]. As fluorescent probes for bioimaging, in particular, dendrimeric nano-objects with high two-photon brilliance (?2?) are required. The one-photon photophysical characterization of newly designed organic dots is thus important to determine their emissive properties and to disentangle their dependence on environmental aspects such as solvent polarity and aggregation induced effects. We report here on the one-photon characterization of a series of newly designed dendrimers based on a phosphorous based scaffold linked to push-push fluorophores, decorated with cationic groups on the periphery in order to achieve hydrophilicity. Dendrimers of generation 1 up to 3 containing two different fluorophores have been studied. The number of peripheral charges varies between 24 and 48 (Figure 1). Detailed steady-state and time-resolved spectroscopic investigations have been performed on the dendrimers in solvents of different polarity, with reference to monomer fluorophores chosen as models. Only one dendrimer show emission features (quantum yield and lifetime) similar to those of the model, whereas all the other dendrimers display an important reduction in the quantum yield in all solvents, with a trend not directly related to the polarity of the medium. In these cases the fluorescence decays show bi-exponential behavior, with one of the lifetimes very similar to that of parent model and the other one much shorter. The reduction of the emission quantum yield and the decay behavior in the dendrimers are discussed on the basis of thermodynamic grounds and on the analysis of aggregation effects, where both intra-molecular and inter-molecular interactions are taken into consideration. [1] Mongin, O.; Rouxel, C.; Vabre, J.-M.; Mir, Y.; Pla-Quintana, A.; Wei, Y.; Caminade, A.-M.; Majoral, J.-P.; Blanchard-Desce, M. Proc. SPIE-Int. Soc. Opt. Eng. 2009, 7403, 740303/1-740303/12.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
