Fig. 4: Preparation of X-ray-sensitive polyurethane foam.

a Polyurethane foam (PUF); b Tb3+-doped Na5Lu9F32 anchored halloysite nanotubes (HNTs@Na5Lu9F32:Tb3+); c Tb3+-doped Na5Lu9F32 anchored halloysite nanotubes coated polyurethane foam (HNTs@Na5Lu9F32:Tb3+@PUF). HNTs@Na5Lu9F32:Tb3+@PUF is prepared by immersing PUF in the HNTs@Na5Lu9F32:Tb3+ aqueous dispersion by fully compressing and soaking.