Sensors excimer

There are many possibilities to use these complex formations in fluorescence sensing. If the excimer is not formed, we observe emission of the monomer only, and upon its formation there appears characteristic emission of the excimer. We just need to make a sensor, in which its free and target-bound forms differ in the ability of reporter dye to form excimers and the fluorescence spectra will report on the sensing event. Since we will observe transition between two spectroscopic forms, the analyte binding will result in increase in intensity of one of the forms and decrease of the other form with the observation of isoemissive point [22]. 

Schazmann B, Alhashimy N, Diamond D (2006) Chloride selective calix[4]arene optical sensor combining urea functionality with pyrene excimer transduction. J Am Chem Soc 128 8607-8614... 

Class 3 fluorophores linked, via a spacer or not, to a receptor. The design of such sensors, which are based on molecule or ion recognition by a receptor, requires special care in order to fulfil the criteria of affinity and selectivity. These aspects are relevant to the field of supramolecular chemistry. The changes in photophysical properties of the fluorophore upon interaction with the bound analyte are due to the perturbation by the latter of photoinduced processes such as electron transfer, charge transfer, energy transfer, excimer or exciplex formation or disappearance, etc. These aspects are relevant to the field of photophysics. In the case of ion recognition, the receptor is called an ionophore, and the whole molecular sensor is... 

The fluorescent molecular sensors will be presented with a classification according to the nature of the photoinduced process (mainly photoinduced electron or charge transfer, and excimer formation) that is responsible for photophysical changes upon cation binding. Such a classification should help the reader to understand the various effects of cation binding on the fluorescence characteristics reported in many papers. In most of these papers, little attention is often paid to the origin of cation-induced photophysical changes. 

E-3 (Figure 10.26) is the first example of an ionophoric calixarene with appended fluorophores, demonstrating the interest in this new class of fluorescent sensors. The lower rim contains two pyrene units that can form excimers in the absence of cation. Addition of alkali metal ions affects the monomer versus excimer emission. According to the same principle, E-4 was designed for the recognition of Na+ the Na+/K+ selectivity, as measured by the ratio of stability constants of the complexes, was indeed found to be 154, while the affinity for Li+ was too low to be determined. 

Fig. 10.26. Excimer-forming cation sensors (E-1 Bouas-Laurent H. et al. (1986) J. Am. Chem. Soc. 108, 315. Marquis D. and Desvergne J.-P. (1994) Chem. Phys. Lett. 230, 131. E-2 Suzuki...

Yamana et al. [67] used bis-pyrene-labeled DNA aptamer for detection of ATP. The pyrene excimer was incorporated into several nucleotide positions. Addition of ATP resulted in an increase in fluorescence only for aptamers labeled by fluorescence probe between residues that were responsible for ATP binding. Using this sensor it was possible to detect ATP with mmol/L sensitivity. 

Figure 16.23 Fluorescent nitric oxide sensor. The Co tropocoronand complex does not emit due to efficient excimer formation (top). Coordination of two nitric oxide molecules changes the geometry and excimer formation is geometrically inhibited (bottom) [94]...

Fig. 7.24 Schematic representation of a photoelectric aerosol sensor (according to EcoChem, 2000) use of an incoherent kryp-tonchloride excimer lamp (A max = 222 nm) as...

Optical temperature sensor (opt(r)odes) based on the viscosity-dependent intramolecular excimer formation of l,3bi(l-pyrenyl)propane in [C4mypr][Tf2N] have been developed [33], The relative intensity of the excimer emission was found to gain in intensity with higher temperature. This has been attributed to the generally low viscosity of the ionic liquid. The working temperature of this luminescence thermometer is between 25°C and about 150°C. 

The decrease of 65 and 66 excimer emission caused by the addition of (S)-borneol was observed with a series of organic compounds having different structures. Some steroidal compounds were particularly efficient in causing a decrease in excimer emission [216,217]. This result indicated that these functionalized CDs might be used as fluorescent sensors of organic molecules [218]. 

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