Isomerization behavior of spiropyran-based compounds upon X-ray irradiation

We investigated the isomerization behavior of 1,3,3-trimethylindolino-6'-nitrobenzopyrylospiran (6-nitro BIPS) upon X-ray irradiation with the aim of developing tissue equivalent imaging sensor materials. We fabricated polymer films incorporated with 6-nitro BIPS. Also, we investigated the effect of the addition of the organic phosphor, b-PBD. Increase in the absorbance at 580 nm was observed at X-ray irradiation doses in the range 1-20 kGy. The increase of the absorbance as function of the dose is enhanced 1.5 times by the addition of b-PBD at 5.0 wt%. These results indicate that 6-nitro BIPS exhibits photochromism with direct excitation by X-rays, and that the photochromism behavior can be sensitized by the fluorescence from b-PBD.