Novel and label-free colorimetric detection of radon using AuNPs and lead(II)-induced GR5 DNAzyme-based amplification strategy.

Radioactive radon decays into a stable daughter product, ²¹⁰ Pb, which was used as the detection target to determine the radon radiation dose in a new technique. Pb ²⁺ triggers DNAzyme to cleave a molecular beacon (MB), resulting in the stem-loop structure opening and forming two single DNA strands (ssDNA). The ssDNA binds to unmodified gold nanoparticles and effectively prevents their aggregation in a salt solution. The detached enzyme strands continue to complement the remaining MB to amplify the response signal. The method proposed in this study exhibited a good linear relationship for Pb ²⁺ and radon concentrations in the range of 6.22 × 10 ² -1.02 × 10 ⁵  Bq h/m ³ with a detection limit of 186.48 Bq h/m ³ using an ultraviolet-visible spectrometer. In practical applications, this sensitive method can avoid radioactive damage in field testing, and the detection limit meets the national standard in China. Importantly, this simple, highly sensitive strategy uses simple equipment and has a strong anti-interference ability. Graphical abstract.