Silica-nanocapsule-doped CR-39 for Fluorescence Detection of X-rays

X-rays (30 kV and 15 mA) generated using an X-ray diffractometer (Rigaku MiniFlex II) were detected as a fluorescence image using the UV-absorber-doped CR-39 when the X-ray dose exceeded 1 Gy. The fluorescence image was easily obtained using an FLA-9000 image analyzer. The excitation wavelength dependence of fluorescence intensity was observed, and the optimal excitation wavelength in the imager for obtaining the highest fluorescence intensity was 555 nm. X-ray irradiation of the UV-absorber-doped CR-39 generates fluorescence centers by charge separation. Therefore, to stabilize the fluorescence image, we attempted to prevent the recombination of the electrons and positive holes generated by X-ray irradiation by doping methylviologen MV2+ encapsulated in silica nanocapsules into CR-39 during its synthesis. It was found that the fluorescence intensity of the image remained constant for almost 120 min when more than 0.5 g of MV2+ encapsulated in nanocapsules were doped in CR-39. A new solid-state fluorescence detector for X-rays was thus realized using CR-39 doped with MV2+ encapsulated in silica nanocapsules.