Fluorescent dyes pyrene

Although many hydrocarbons exhibit fluorescence, often they are colourless and the fluorescence is only just into the blue, e.g. the linear terphenyl and quaterphenyl. Polycyclic ring systems such as terrylene and rubicene are used in analytical methods and OLEDs but a large number are ruled out of commercial use because of their potential to act as carcinogens. However, as mentioned in section 3.5.1.3, pery-lene is a useful fluorophore in a variety of outlets and pyrene is another polycyclic compound of interest. One derivative of pyrene (3.27) is a yellow-green fluorescent dye used in textile applications (Cl Solvent Green 7) and in analysis and sensors (see section 3.5.6.4). 

For example, in the case of pyrene (the most widely used fluorescent dye) the measured parameter is /1//3, the ratio of intensity of the first (372 nm) and third (385 nm) fluorescence peaks for pyrene aldehyde it is the wavelength of maximum absorption (36,37). In the presence of interacting polymer the plot is displaced to lower surfactant concentration this implies that a surfactant aggregation process, formally akin to micelli-... 

The CMC is the concentration of a copolymer above which the polymer self-assembles into nanoassemblies, and below which the copolymer exists in the solution as individual molecules (unimers). The CMC is a very important parameter, reflecting the stability of micelles in solution and the ability of copolymers to form micelles in solution. The fluorescence probe technique is the most used method to determine the CMC. Pyrene, whose fluorescent spectrum is environment sensitive, particularly its first and third peaks, is the first fluorescence dye used. The intensity ratio of the third and first peaks in its emission spectra has a sharp transition at CMC and thus can be used to determine the CMC (Figure 12). 

Palo Alto, CA) with an angle of 62 degrees. Pyrene was selected as the fluorescent dye because it is soluble in both PFOB and water, and is easily quenched with potassium iodide (KI), which is only soluble in water. 

Arenas et al. [54] report the solubilization of polychlorocarbon solvents by alkanoylglycamines, a phenomenon that is to be expected of highly water-soluble nonionic surfactants. Miyagishi et al. [55] report determination of the CMC s of these surfactants using measurements of the fluorescence of benzophenone imine. Such determinations using, for example, pyrene have long been known the use of this particular fluorescent dye is unusual. 

Roth et al. [42] used steady-state fluorescence measurements to study the emission spectra of pyrene and anthracene dyes covalently bonded to polystyrene (PS) upon phase separation from poly(vinyl methyl ether) (PVME). The total fluorescent dye content in the samples was <0.02 mol%. As shown in Figure 25.15a, before phase separation the fluorescence intensity of the spectra decreased slowly with increasing temperature. However, after phase separation (see Figure 25.15b) a sharp increase in fluorescence intensity was observed, which was attributed to the removal of fluorescence quenching of the dye by the local presence of the more polar PVME component in the misdble state. These results showed clearly that the PS/PVME blend displays a lower critical solubility temperature (LCST) type of phase diagram. 

Styrene and NHS active ester repeat units is reacted with the fluorescent dye 1-aminomethyl pyrene. The reaction is schematically depicted in Fig. 21. The monolayer thickness is approximately 42 nm. The active ester content of the copolymer is 30 mol%. A quartz slide is used as substrate. Figure 22 shows theUV/ vis spectrum of the polymer monolayer after extraction. The absorption spectrum of the 1-aminomethyl pyrene is clearly visible. The absorption maximum is located at 340 nm, the maximum of the emission at 376 nm in good agreement with literature data for comparable compounds not attached to a solid surface [60,61]. The substrates show, after deposition of the monolayer, a blue fluorescence if the sample is irradiated with light having a wavelength of 360 nm. 

Kool and co-workers recently reported a multicolor set of water-soluble dyes synthesized through the combination of three to five individual fluorophores assembled on a DNA-like backbone [94, 95]. As a continuation of their previous works on various DNA analogs [96-99], they synthesized the oligodeoxyfluoro-side (ODF) with seven fluorescent monomers, such as pyrene, perylene, dimethy-laminostilbene, and three stilbene derivatives, and they assembled these fluorescent DNA monomers into oligofluor chains using a DNA synthesizer (Fig. 26). Using... 

In a film, however, molecular mobility is severely limited, so that excimer fluorescence must arise mainly from pairs or groups of pyrene molecules that were approximately in the excimer configuration when the film was cast. Thus, the intensity of the excimer emission is also an indication of the local concentration of pyrene in the cast film. If the pyrene aggregates, we expect that the excimer fluorescence would increase with aggregation. This system can be used to look at the aggregation of very low concentrations of a small molecule dye in a polymer film, and potentially detect molecular aggregation before it would be observable by other tech-... 

Recent literature contains many examples of the construction of cascades [56], Usually they are made by the covalent linking of monomer dyes, which allows strict control of their stoichiometry. The pyrene-Bodipy molecular dyads and triads are examples [57]. Efficient energy flow was reported in a purpose-built cascade molecule bearing three distinct chromophores attached to the terminal acceptor [58]. A combinatorial approach with the selection of the best hits can be applied using the assembly of fluorescent oligonucleotide analogs [59]. 

Montalti and co-workers studied dansyl [27] and pyrene [28] derivatives and found the fluorescence quantum yields and excited-state lifetime of these two dyes increased in DDSNs. They attributed the enhancements to the shielding effect from the quenchers or polar solvent in the suspension. Their studies also demonstrated that the lifetime of the doped dye molecules was also dependent on the size of the DDSNs. Small DDSNs had a larger population of the short-living moieties that were more sensitive to the environment outside the DDSN. In contrast, the large DDSN had a larger population of the long-living moieties that were not sensitive to the environment. 

---