Fluorophore enhanced emission

Fig. 6 Modified Jablonski diagram for illustrating metal-fluorophore interactions, (a) the transition of dye excited by the incident light, (b) the enhanced excitation according to enlarged electromagnetic field, (c) the fluorescent emission of dye molecule, (d) the nonradiative relaxation, (e) the enhanced emission of the fluorophores and metal coupling in far field. Reproduced with permission from Ref. [77]...

Extrinsic fluors are produced via a chemical reaction where the added reagent either enhances emission of a weak emitter through association or the analyte is derivatized with a fluor tag. 8-Hydroxyquinoline (HQS) is an example of an extrinsic complexing reagent (Reaction 11.1) where the native ligand is a marginal fluorophore but forms intense emitting metal chelates. This approach affords sensitive detection of... 

Enhancement of fluorescence due to the complexation of metal ions with fluoroionophores has been used as a well-precedented technique to analyze for the presence of metal ions [189-191], A number of studies have reported chelating fluorophores whose emission spectra change upon the addition of metal ions [192-198]. One remarkable result of this emission intensity enhancement is shown in Scheme 23, where the chelation of zinc chloride to 9,10-bis(((2-(dimethylamino)ethyl)methylamino)methyl)anthracene drastically enhances the observed fluorescence by a factor greater than 1000-fold [199], In the absence of Zn2+, the singlet excited state of anthracene moiety is strongly quenched by intramolecular photoinduced electron transfer from the amine to the anthracene moiety. The complex formation of Zn2+ with the amine moiety may result in the largely positive shift of the one-electron oxidation potential. Thus, intramolecular photoinduced electron transfer is strongly suppressed by the complexation of the amine moiety with Zn2+,... 

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).

Y. Zhang, K. Aslan, M. J. Previte, and C. D. Geddes. Metal-Enhanced Fluorescence Surface Plasmons can Radiate a Fluorophores Structured Emission Applied Physics Letters, 2007, 90, 053107. 

Enhanced fluorescence, or MEF, is a result of both a net system absorption and plasmon coupling and subsequently efficient emission, but to date, it has not been possible to quantify the relative contributions of enhanced emission and net increase in the system absorption to the MEF phenomena.(23) Due to the increase in the population of the singlet excited state or net system absorption, the very presence of MEP has also suggests an increase in the population of the triplet state.(23) The presence of Metal-Enhanced Fluorescence, Phosphorescence, Metal-Enhanced singlet oxygen and superoxide anion radical generation in the same system is an effect of the enhanced absorption and emission effects of the fluorophores near-to silver, although these processes are effectively competitive and ultimately provide a route for deactivation of electronic excited states. 

The tunability on emission wavelength of cyanine derivatives is based on the understanding of structure-photophysical property relationships, which allows the development of near-IR fluorophores [80, 84—87]. Enhancement of the rigidity in... 

In this case, the maximum enhancement is achieved when A,rcs is equal to the peak emission wavelength of the fluorophore. This enhancement is far more significant for fluorophores of low QE than for those of higher QE. An additional effect namely, a metal-fluorophore quenching can also occur for very small NP-fluorophore separations, typically within 5nm. This has important implications for the fabrication of an enhanced sensor chip, as will be seen in the following section. 

The optimal enhancement effect is observed when the localized surface plasmon resonance is tuned to the emission wavelength of a locally situated fluorophore [86]. This is consistent with the model suggesting a greatly increased efficiency for energy transfer from fluorophores to surface plasmons [78]. Since resonance energy transfer is involved, the important factors affecting the intensity of fluorescence emission must also be the orientation of the dye dipole moments relative to the... 

Reppy MA (2008) Enhancing the emission of polydiacetylene sensing materials through fluorophore addition and energy transfer. J Fluoresc 18 461 —471... 

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