Excimer

About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.

Excimer emission in protonated pyridine systems. 1. Fluorescence spectroscopy of protonated pyridine and its methyl derivatives in rigid glass solution at 77 K

Abstract: The emission properties of pyridine and mono- and dialkylpyridines have been studied in solution in the presence of trifluoroacetic acid at room temperature and 77 K. At room temperature, mono- and dialkylpyridines exhibit a weak and broad fluorescence band with a peak at about 300 nm except for pyridine and 4-n-alkyl- and 2-methylpyridines. This fluorescence originates from a (..pi../sup -/*) state of protonated mono- and dialkylpyridines. However, they exhibit no excimer fluorescence even in a highly concentrated system. At 77 K, in the mixed solvent of tetrahydrofuran, methanol, and methyltetrahydrofuran (4:3:1 by volume) in the presence of trifluoroacetic acid, mono- and dialkylpyridines exhibit a broad and structureless fluorescence band at about 325 nm, in addition to the normal fluorescence band. 4-n-Alkyl- and 2-methylpyridines apparently exhibit only a very weak fluorescence band at about 325 nm, but pyridine is nonfluorescent even at 77 K. It is concluded from the observations of absorption and fluorescence excitation spectra and the fluorescence characteristics that this broad and structureless band is ascribed to a particular excimer (termed dimerlike excimer fluorescence for convenience) which originates from the interaction between protonated monoalkylpyridines (or dialkylpyridines). The analysis of temperature and solvent dependence of fluorescence spectra and the phasemore » transition of the mixed solvent show that the cage of the mixed solvent plays an important role in the dimerlike excimer formation. Further, on the basis of a four-electron ASMO approximation, the dimerlike excimer fluorescence is assigned to result from the in-plane twisted and plane parallel configuration of a compact pair of protonated pyridines.« less

Emission from ionic cesium fluoride excimers excited by a laser-produced plasma.

Abstract: CsF vapor generated in a heat pipe was excited by a laser-produced plasma. Temporally integrated spectra and time-resolved fluorescence on the ionic excimer transition Cs(2+)F(-) ? Cs(+)F were observed at 185 nm. The pressure dependence of the fluorescence is influenced by self-absorption in the CsF vapor. The fluorescence is assigned to the Cs(2+)F(-) ((2)Sigma(1/2), B)? Cs(+)F ((2)Sigma(1/2),X) transition.

Switching monomer/excimer ratiometric fluorescence to time-resolved excimer probe for DNA detection: A simple strategy to enhance the sensitivity

Abstract: Pyrene has been widely used in designing ratiometric fluorescent probe due to its excimer emission that is different with the monomer in emission wavelengths. To take the advantage of the long-lived excimer emission, a pyrene-based zinc complex is designed as model compound for time-resolved DNA detection. PyZn exhibits excimer emission upon the binding of DNA, and the lifetime of excimer ( τ > 40 ns) is one magnitude longer than that of the monomer. With a delay time of 30 ns, the monomer emission can be eliminated almost completely, leading to a much weaker background and an improved signal-to-noise ratio. Significantly, this excimer-based long-lived fluorescence is not quenched by oxygen, which provides a general strategy to design long-lived fluorescent probes for time-resolved detection in oxygenic environments and organisms.