Fluorescence enhancement factor

Fig. 3 Typical ICT probes (left) and representative spectroscopic responses toward selected metal ions (right). Color code (left) coordinating atoms in blue, bridgehead atom of the fluorophore that takes part in complexation in orange, formal donor fragment in red, formal acceptor fragment in green (right) hypsochromic shifts in red, bathochromic shifts in green, fluorescence enhancement in violet, fluorescence quenching in blue. Symbols in table Aabs, 7em,

Leaving the classic ICT architecture and moving toward electronically decoupled systems, a strategy for obtaining extraordinarily high fluorescence enhancement factors has been developed at the end of the 1990s - the concept of... 

It should be noted that the rate of change of fluorescence intensity and the fluorescence enhancement factor depend on the polymerization conditions (temperature, initiator concentration, monomer reactivity) and on the nature of the polymer formed. 

Several structural and conceptual similarities can be seen between 13 and 14 [59], 14 reserves its best performance for Cd2+ with a fluorescence enhancement factor of 6. Its lack of response to protons is no surprise owing to the lack of an undelocalized amine within the iminoylthiourea moiety. However, the true... 

PET system with gradually mounting fluorescence enhancement factors as the size of the alkali cation increases. The 1,3-alternate calix[4]arene moiety within the macrobicycle is clearly the reason for this bias toward larger alkali cations. 

Finally, the sensory behaviour of (18) is not as good as that of its smaller ring cousin (14). On the positive side, however, the cation-binding constants remain quantitatively predictable and fluorescence enhancement selectivity peaks at potassium ion. The smaller fluorescence enhancement factor of 3 for (18) with potassium ion can be attributed to lower intrinsic charge density and more charge dispersal to aliphatic oxygen centres than those discussed in the previous paragraph. 

Water-soluble cyclophane 86145 exhibited a well-defined fluorescence band at 290 nm with a 210 nm excitation. The emission intensity was markedly increased by complexation with Zn2+ which forms a 2 1 (metal-ligand) complex. The fluorescence emission is pH-independent to pH 2. The fluorescence enhancement factor is 5.0 at pH 6 and 50 at pH 8.6 (due to the pH dependence of the free ligand). Ni2+ and Cu2+ ions quenched the ligand fluorescence via a PET mechanism. Furthermore, when cyclophane 86 was coordinated to Cu2+, the molar absorptivity of the transition band observed at 260 nm was increased by a factor of about 10. Such a large spectral change was not observed for the Zn2+ and Ni2+ complexes. In the Cu2+ complex, the two phenyl rings of the cyclophane are expected to be... 

In addition to the PLE spectra, we calculated the total fluorescence enhancement factor as the ratio of the photoluminescence near the nanoprism to the background photoluminescence. Figure 4.13 shows representative plots of the total... 

Figure 11.7 Left Schematic representation of LB layers construction and subsequent electrostatically adsorbed SRB dye molecules at octadecylamine layers. Octadecylamine layers were spaced from the substrate by inert stearic acid layers, d is the distance between fluorophore and SIF sur ce that can be varied with the number of inert stearic acid layers at a resolution of 2.5 nm. Right Fluorescence enhancement factor (filled circles) and corresponding ratio of lifetimes (open circles) of SRB on glass and SIF surfaces versus distance from the SIF surface. Reprinted with permission from reference [26]. (2007) American Chemical Society...

There is no sensitivity to individual molecular trajectories or dipole orientations, but one ends up directly with global figures to characterize the emitted fluorescence. Besides, distinguishing between the contributicms of the radiative rate and the collection efficiency remains a challenge, mainly because of the intrinsic difficulty to reliably measure collection efficiency. Lastly, the fluorescence enhancement factors are spectrally averaged within the fluorescence bandpass detection window. However, further investigations can provide some additional knowledge on these last two points, as we will discuss hereafter. 

The maximum of fluorescence enhancement factor per mitox molecule (K = 50) was obtained for TGF-240 covered by physisorbed poly-L-lysine monolayer... 

---