Colorimetric and photothermal-derived multimodal sensor for rapid and portable assay of Hg2+ based on target-sensitized oxidase-like activity of CoSe2 nanorods

It is imperative to design a highly selective, sensitive, and portable approach for the reliable determination and monitoring of mercury ion (Hg 2+ ) given its severe toxicity to both ecosystems and public health. Herein, we develop a colorimetric and photothermal-derived multimodal sensor for point-of-care testing of Hg 2+ based on the Hg 2+ -sensitized oxidase-mimetic activity of CoSe 2 nanorods. The synthesized CoSe 2 nanorods show negligible oxidase-mimetic activity. It can bind with CoSe 2 nanorods via an Hg-Se bond when Hg 2+ is present. The generation of HgSe on the surface of CoSe 2 nanorods booms the oxidase-like activity of CoSe 2 nanorods to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) into oxidative TMB (oxTMB), generating a hyperchromic effect and light-driven thermal effect. Consequently, the color and absorbance of the solution changed, realizing the colorimetric and visual sensing of Hg 2+ . The limit of detection (LOD) is 7.3 nM for colorimetry. Meanwhile, a photothermal sensor was also developed under the drive of a laser with a LOD of 12.3 nM. The developed sensor also shows high selectivity toward Hg 2+ because of the strong affinity between the CoSe 2 and Hg 2+ . Furthermore, the latent application of this sensor is confirmed by determining Hg 2+ in real water samples. More significantly, multimodal detection not only enhances accurate detection results through mutual authentication of different signals but also satisfies the demands of diversified detection by consolidating the advantages of photothermal and colorimetric approaches.