Dyes, organic fluorescent

There are several important features that determine the performance of organic dyes as fluorescent probes and labels ... 

Resch-Genger U, Grabolle M, Cavaliere-Jaricot S, et al. Quantum dots versus organic dyes as fluorescent labels (Review). Nat. Methods 2008 5 763-775. 

Organic fluorescent dyes with the appropriate spectral properties also can be paired with lanthanide chelates in FRET systems. For instance, many rhodamine dyes and the cyanine dye Cy5 have ideal excitation wavelengths for receiving energy from a nearby europium chelate. The LeadSeeker assay system from GE Healthcare incorporates various Cy5-labeled antibodies for developing specific analyte assays. In addition, if using a terbium chelate as the donor, then a Cy3 fluorescent dye can be used in assays as the acceptor. 

The original polymeric latex particles still are widely used for separation and detection. Polymers provide a matrix that can be swollen for embedding other molecules in their core, such as organic dyes or fluorescent molecules. Even nanoparticle quantum dots can be incorporated into larger latex particles to form highly fluorescent composite microparticles. 

The electronic excited state is inherently unstable and can decay back to the ground state in various ways, some of which involve (re-)emission of a photon, which leads to luminescence phenomena (fluorescence, phosphorescence, and chemiluminescence) (22). Some biologic molecules are naturally fluorescent, and phosphorescence is a common property of many marine and other organisms. (Fluorescence is photon emission caused by an electronic transition to ground state from an excited singlet state and is usually quite rapid. Phosphorescence is a much longer-lived process that involves formally forbidden transitions from electronic triplet states of a molecule.) Fluorescence measurement techniques can be extremely sensitive, and the use of fluorescent probes or dyes is now widespread in biomolecular analysis. For example, the large increase in fluorescence... 

In this chapter, we discuss core-shell semiconductor quantum dots and their applications in biological labeling (Fig. 12.1). In comparison with organic dyes and fluorescent proteins, semiconductor quantum dots represent a new class of fluorescent labels with unique advantages and applications. For example, the fluorescence emission spectra of quantum dots can be continuously tuned by changing the particle size, and a single wavelength can be used for simultaneous excitation of all different-sized QDs. 

Hexavalent uranium fluoresces brilliant green, peaking between 500 and 540 nm in most glass hosts. The brilliance of uranium fluorescence far exceeds that of the most efficient organic dyes. The fluorescence emission spectrum of hexavalent uranium-doped silica gel-glass is presented in Fig. 7. The peak maximum is at 533 nm [35]. 

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