A blue-light dosimeter which indicates the dose accumulation by a multicoloured change of photodegraded polymer.

Abstract

Luminescent polymers are commonly employed in light-emitting displays because of their good processability and higher luminance with low power consumption. However, even though they are candidates for lighting applications, they are susceptible to photoxidation processes which dramatically change their colour with light exposure. In this work we use the light instability of luminescent polymers in order to design a blue-light dosimeter which indicates dose accumulation by multicoloured changes of photodegraded poly(2-methoxy-5(2_-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV). Photoluminescence and absorbance spectra measurements were carried out on MEH-PPV solutions under the effect of blue-light provided by phototherapy systems. All measurements were done maintaining chief conditions of jaundice treatments. It is observed that changes from orange-red to yellow clearly on colour solutions, while its peak position emission shifts from orange-red to blue and decreases in intensity with increasing radiation exposure time. Experiments performed with oxygen enriched solutions were shown to improve these effects, which is mainly caused by the competition between two possible mechanisms: a light induced polymerization of MEH-PPV and replacement of C C by C O bonds on the polymer backbone. Analyses of the relation between the irradiance produced by phototherapy systems and CIE (1931) chromatic diagram of MEH-PPV reveal this polymer as an easy to operate blue-light dosimeter, and the results reported here clearly demonstrated the possibility to produce self-adhesive patch of luminescent polymers in order to attach such organic dosimeter safety and placed closer to the skin of jaundiced infants.