Molecular dosimeter developed from high efficient rare-earth complexes:: UV-A, UV-B and UV-C responses

We have developed a molecular dosimeter where the most important features are its high sensitivity and selectivity to UV cumulative measurements. In this work, we have been studying the three main UV regions regarding skin damage: UV-A, W-B, and UV-C. The active part of the dosimeter is a thin film of a few hundred angstroms produced by thermal evaporation of volatile and thermodynamically stable lanthanide complexes. The Eu(III) emission (D-5(0) --> F-7(2)) and the Tb(III) emission (D-5(4) --> F-7(5)) were monitored as a function of UV exposure time. An irreversible luminescence decrease of the Eu(III) emission was observed giving it a memory effect allowing dosimetry measurements. The Tb(III) behavior was also analyzed. All measurements were quantified by an integration sphere coupled to a radiometer. We may also adjust the film thickness for sensitivity control: for 600 Angstrom thickness we obtained time constants of 7 min for UV-A (46 mu W/cm(2)), 12 min for UV-B (55 mu W/cm(2)). In the bulk limit the time constant was found to be more than 40 times higher. A time constant of 1.5 h was measured in the W-C (15 mu W/cm(2)) region for a 150 Angstrom film, and an estimation of 11 h was calculated for a 600 Angstrom film.