Self-assembled TMB-CuO₂ nanosheets for dual-mode colorimetric and NIR-II photothermal detection of uranyl ion

The development of highly sensitive and selective point-of-care testing (POCT) techniques using optical methods for uranyl ion (UO₂²⁺) is essential for the effective monitoring of acidic uranium contamination. colorimetric methods have gained significant attention for their rapid response times, ease of use, and cost-effectiveness in the quantitative analysis of uranyl ions.

Herein, this study presents a self-assembled nanosheet composed of 3,3,5,5-tetramethylbenzidine (TMB) and CuO₂, designed for the dual-mode colorimetric and photothermal detection of UO₂²⁺. The CuO₂ nanodots could be incorporated into TMB nanosheets by the nanoprecipitation method. The TMB-CuO₂ nanosheets exhibited spontaneous decomposition in acidic environments, leading to the production of Cu²⁺, H₂O₂, and TMB, which facilitated in situ TMB oxidation through a Fenton reaction. The UO₂²⁺ can form coordination complexes with imines derived from the oxidation products of TMB, leading to significant accumulation and discoloration, thereby enabling the detection of UO₂²⁺ with naked eyes and handheld thermometers conveniently. The constructed UO₂²⁺ sensor demonstrates acceptable sensitivity and stability, with a linear range of 2.6-78.12 μM and a low detection limit (1.78 μM).

This study provides a method for synthesizing self-carried signal tag nanomaterials with enhanced loading capacity, further expanding the application of straightforward colorimetric and thermometric techniques for the sensitive and selective detection of acidic uranium contamination.