Fig. 4: Radioactive gas adsorption and detection by porous scintillating Hf-DPA crystalline powder.

a, Experimental argon and krypton isotherms and GCMC simulated adsorption isotherms of argon, krypton, xenon and radon for a cubic unit-cell of Hf-DPA (32.79 × 32.79 × 32.79 ų) at 298 K. The uptake is expressed in molecules per unit-cell (MPU). b, Gas density distributions calculated at room temperature at constant pressure of 50 mbar by GCMC adsorption simulations for krypton and radon. Blue and red colours indicate the highest and lowest gas density in the pores, respectively. c, Gas–matrix interaction energy distribution probability calculated at a constant pressure of 50 mbar and room temperature for krypton, xenon and radon. d, Double coincidence detection of ⁸⁵Kr by polystyrene microspheres powder and Hf-DPA powder using two different coincidence windows (CWs) for detection (40 ns and 400 ns). The labels on the x-axis indicate when the radioactive gas has been injected into the detection device (gas in) and then washed out by a flux of clean air (gas out). cps, counts per second. e, Double coincidence detection rate of ⁸⁵Kr by the Hf-DPA powder as a function of the sample activity using different coincidence windows. The vertical lines mark the detection limit of a commercial device employed for detecting noble gas radionuclides (refs. ^46,47, red and violet line, respectively). The solid lines are the fit of data with linear functions. Error bars depict the residual values of the fit. f, Double coincidence detection of ²²Rn by polystyrene microsphere powder and Hf-DPA powder using different coincidence windows.