Radiochromism in Nb-sensitized WO3 as an instant and cumulative X-ray dose recorder

Abstract

Radiation detection and protection are gaining increased importance due to the widespread applications of radiation technology in industry and human health, especially for X-rays. However, radiation detection is usually indirect and inconvenient for personal dose measurement. In this paper, we have developed a radiochromic strip for naked-eye visualization and direct cumulative recording of X-ray dose for the first time. The radiochromic phenomenon was observed in a family of Nb-doped WO₃ powders, which exhibit successive color changes with continuous or intermittent exposure to X-ray irradiation. Homogeneous doping of Nb in the WO₃ lattice facilitates a phase transition from a monoclinic to a tetragonal structure, which enhances the radiochromic performance due to the activated itinerant electron migration pathway of W–O–W bonds in corner-shared WO₆ octahedral subunits within the lattice. The X-ray-sensitive pigments record the X-ray illumination dose by changing color from bright yellow to dark blue with high contrast. The chromaticity aberration for the color of the samples between the as-synthesized and radiated for 60 minutes of the radiochromic pigments increased from ΔE = 42.07 (for WO₃) to ΔE = 72.53 (for Nb_0.09W_0.91O₃). Ex situ XRD and Raman spectra demonstrated that long-range lattice ordering is maintained while internal local vibrations are disrupted after X-ray irradiation. The X-ray radiation dose has been recorded cumulatively as dose-dependent radiochromism up to 556.6 μGy, with color evolution from light yellow to deep blue, which can be directly visualized by the naked eye. This technique aids in promoting portable radiation detection through device-free readout of dose recording for nuclear and radiation safety.