Thioflavine T-induced charge neutralization assembly of AuNPs for colorimetric sensing of thallium

Thallium (Tl) is regarded as one of the 129 so-called “priority pollutants”, but its rapid optical sensing is largely unexplored. In this work, an AuNP-based label-free colorimetric sensing scheme was developed for Tl + . Specifically, thioflavine T (ThT) was found to induce charge neutralization aggregation of AuNPs, resulting in stable and intense blue color of AuNPs. Due to the higher affinity of PS2. M (DNA)-AuNPs over PS2. M-ThT, PS2. M DNA would protect AuNPs from aggregation by ThT. Since the affinity of PS2. M DNA-Tl + was even higher than that of PS2. M DNA-AuNPs, in the presence of Tl + , PS2. M DNA would be first captured by Tl + and restricted to be adsorbed onto AuNPs, resulting in ThT-induced aggregation of AuNPs for colorimetric sensing of Tl + . The proposed colorimetric sensing offered a limit of detection (LOD, 3σ) of 3.2 nM, which was lower than the maximum permitted amount of Tl + in drinking water regulated by EPA (10 nM). The accuracy of the proposed method was first verified through analysis of six water samples. Furthermore, the proposed colorimetric system was also explored for real-time monitoring of Tl + leakage from coal mine during raining water soaking, and maximum Tl + amounts occurred at about 12–24 h. ThT-induced charge screening assembly of AuNPs was harvested for colorimetric detection of Tl + in combination with G-quadruplex recognition. • ThT, a G-quadruplex dye, was found to induce charge screening assembly of AuNPs. • A colorimetric approach was developed for facile Tl+ detection in environmental water samples. • The method was explore for real-time monitoring of Tl + leakage from coal mine during raining water soaking.