Aggregation-enhanced fluorescence

Scheme 9.13 A molecule undergoing aggregation-enhanced fluorescence...

A variety of luminescent nanoparticles have been specifically devised for con-focal and multiphoton microscopy. These include nanomaterials, such as silica-based nanoparticles doped with two-photon-absorbing fluorophores, able to exhibit aggregation-enhanced fluorescence, gold nanoparticles, semiconductor nanocrystals (quantum dots/rods), and nanophosphors, viz., ceramic nanoparticles containing luminescent lanthanide ions. 

Scheme 9.14 Molecules undergoing aggregation enhanced fluorescence. The cyano group in stilbene derivatives such as 27 and 28 imparts a twist outside planarity in solution, while aggregatirai causes planarization. Molecule 28 also incorporates a dithienylethene moiety for dual stability...

Near-IR Metal Enhanced Fluorescence And Controlled Colloidal Aggregation... 

Both Geddes and the Lakowicz group s have investigated the metal-enhanced fluorescence of fluorophores on silver island films (SIFs) [11,26,27] and variously aggregated silver nanoparticles in solution [28,29]. One example of enhancement on SIFs is discussed below [26]. In this work the distance-dependent MEF of a monolayer of sulforfiodamine B (SRB) on SIFs was studied. A SRB monolayer was electrostatically incorporated into the Langmuir-Blodgett (LB) layers of octadecylamine (ODA) deposited... 

The effect of micellar aggregates on the luminescence of organic compounds can be easily explained, whereas the introduction of a metal ion in these microheterogeneous systems significantly increases the difficulty to rationalize the observed effects. In fact, the mechanisms which are operating in micellar-enhanced fluorescence of metal complexes have not been completely elucidated. However, neutral complexes appear to be protected against deactivation pathways by the surrounding micellar environment [1]. 

Kim S, Ohulchanskyy TY, Pudavar HE, Pandey RK, Prasad PN (2007) Organically modified silica nanoparticles co-encapsulating photosensitizing drug and aggregation-enhanced two-photon absorbing fluorescent dyes aggregates for two-photon photodynamic therapy. 

YUA 07] Yuan W.Z., Qin A., Lam J.W.Y. et al., Disubstituted Polyacetylenes Containing Photopolymerizable Vinyl Groups and Polar Ester Functionality Polymer Synthesis, Aggregation-Enhanced Entission, and Fluorescent Pattern Formation , Macro/Mo/ecw/es, vol. 40, pp. 3159-3166,2007. 

R. Aroca and E. Johnson, Sur ce enhanced fluorescence of aggregates in Langmuir-Blodgett monolayers. 

The formation of a microphase structure can be sensitively detected by using hydrophobic fluorescent probes. Hydrophobic microdomains tend to solubilize hydrophobic small molecules present together in aqueous solution. For example, diphenylhexatriene (DHT) is hydrophobically bound to the St aggregates in ASt-x in aqueous solution and, as a result, the fluorescence intensity is greatly enhanced. Figure 9 shows the fluorescence intensity of DHT in the presence of ASt-x relative to the intensity in its absence (I/I0) as a function of the ASt-x concentration [29],... 

---