Fluorescence
“Fluorescenceis the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons, this two-photon absorption can lead to emission of radiation having a shorter wavelength than the absorbed radiation.”
“The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible, and the emitted light is in the visible region.”
Recent Journal Articles
Tunable Metal-Enhanced Fluorescence by Stimuli-Responsive Polyelectrolyte Interlayer Films
(587–592)Macromolecular Rapid Communications 32 #7 (2011)
Ma et al of the University of Science and Technology, China, found tunable metal-enhanced fluorescence (MEF) of Ag nanostructures. Because of the good MEF properties of the highly dendritic Ag nanostructures, we obtained an increase of up to 25 times for the weak fluorescence of porphyrin molecules (Por4–). More importantly, by the introduction of a stimulus-responsive PAA/PDDA multilayer film as an interlayer, the distance between the fluorophores and the Ag nanostructures could be tuned by immersing the substrates into solutions of different ionic strength or pH. The MEF behavior of the composite films could thus be tuned in a controlled manner, because of the distance dependent nature of the MEF effects. (RDC 4/5/2011)