Aggregation-induced enhanced emission

Keywords Aggregation-induced enhanced emission (AIEE) Fluorescent organic nanoparticles Ion-association method Organic dye nanoparticles Reprecipitation method Restriction of intramolecular rotation Size-dependent optical properties... 

Fig. 5.16 Selected fluorophores 44 with aggregation-induced enhanced emission. soi, fluorescence quantum yield in dioxane < agg, fluorescence quantum yield in dioxane-water (20 80).

Aggregation-induced enhanced emission polymeric nanoparticles... 

A self-assembled chitosan polymeric nanoparticle conjugated with fluorescent stilbene derivatives that exhibit aggregation-induced enhanced emission (AIEE) in vivo was reported by Lim et al. The AIEE phenomenon occnrs in a special class of dyes that have lower flnorescence in solution, but in a concentrated environment (snch as when encapsnlated in a nanoparticle or vesicle), the dyes show a marked enhancement in emission intensity, in contrast to common organic dyes. Dipolar tricyanostilbene derivatives... 

A similar aggregation-induced enhanced emission is reported by the same group of Park and co-workers (Fig. 17). Trifluoromethyl-based cyanostilbene 32 acts as a gelator for 1,2-dichlormethane. The formed gel is strongly fluor-... 

Qian Y, Li S, Zhang G, Wang Q, Wang S, Xu H, Li C, Li Y, Yang G (2007) Aggregation-induced emission enhancement of 2-(2 -hydroxyphenyl)benzothiazole-based excited-state intramolecular proton-transfer compounds. J Phys Chem B 111 5861-5868... 

The other key point is that the recognition event should then produce differences in the fluorescence properties of the sensor molecule in the presence of the two enantiomers of the analyte. Several mechanisms can be used to generate the fluorescence response (Figs. 2 and 11) by changing the electronic properties and the conformation of the sensor. Aggregation induced emission enhancement (AIEE) [49] was recently shown to be able to generate an enantioselective fluorescence response. Special optical techniques such as circularly polarized luminescence (CPL) are now available to detect enantioselective interactions occurring in the excited state or in the second coordination-sphere interactions [49]. 

NTPs), such as ATP, UTP, CTP, TTP, and GTP, over mono- and diphosphates (NMPs and NDPs, respectively), with enhancement of the fluorescence emission. In addition, it was postulated that, in the presence of probe 23b, NTPs induce aggregation, leading to an increase in fluorescence emission called aggregation-induced emission. 

The 2 + 2/3 + 2-cycloaddition reactions of cyclic ketimines formed functionalized sultam-fused azetidines and dihydropyrroles in good yields and high enantio-selectivities. The Cu(I)/Lewis acid-catalysed 3+2/2+2-cycloaddition reaction of 0 sulfonyl azides (1) with terminal alkynes (2) yielded bis-/V-sulfonylcyclobutenes (3) that exhibit aggregation-induced emission enhancement in the solid state (Scheme 1). Density functional theory (DFT) at the B3LYP/6-311++G(d,p) level has been used to investigate the Mo(CO)6-catalysed intramolecular 2+2- or 2 + 2+ 1-cycloaddition reactions of 5-allenyl-l-ynes." ... 

Similarities between CD and absorbance methods are also found between CD and fluorescence and CD and circularly polarized luminescence (CPL). Three prerequisites are needed to produce FDCD and CPL activities. Intense emission signals normally associated with fluorescence are attractive because limits of detection are lowered considerably. FDCD finds more uses as a chromatographic detection device. A CD signal is usually induced by some kind of molecular complexation reaction. Association can be with a simple molecule or with an aggregate of molecules, such as chiral micelles, which are known to be fluorescence enhancers. In cases of color induction combined with fluorescence induction, FDCD can lead to even higher levels of selectivity among analytes that have been derivatized by the same color reagent. 

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