Localized fluorescence during application

Localized fluorescence during application of a Sinusoidal Electric Field. Top, - 0° middle, - 90° bottom, - 180°. 

In many brighteners deactivation from the Si state depends on the local environment. When fixed in (highly viscous) solid substrates, brighteners fluoresce with high quantum yields (0 ca. 0.9). In (low-viscosity) solvents, such as are used before or during application of the brightener, the quantum yield is often low and the probability of formation of photoproducts is higher. 

Some of these applications are complementary to the steady state methods discussed in section 8.2. Investigations of fluorescence lifetimes and of anisotropy or fluorescence quenching phenomena in the lifetime mode, that is during the decay after a single flash, require more elaborate instrumentation and theory than steady state investigations. On the whole applications rather than detail of methods are discussed here. The use of the lifetime method for the study of molecular rotation, domain movement and more local dynamic events can often, some experts say always, provide additional information even for those problems which can be investigated with considerable success by steady state measurements. 

FOCS (fiber bundle) was used by S.Szunerits et D.Walt" to image the concentration of Al cations during localized dissolution of pure aluminium in this case the fluorescent molecule was morin (excitation 3 lOnm - emission 510 mu) which allowed the in situ visualization of the corrosion processes by monitoring the release of Al. Nevertheless, application of FOCS for corrosion mechanisms has not been deeply investigated in the mentioned work but this kind of sensor represents a promising tool which could be applied. 

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