Portable smartphone-assisted highly sensitive detection of mercury ions based on gold nanoparticle-modified...

A novel portable smartphone-assisted colorimetric method was reported for the determination of Hg²⁺ with good analytical performance. A Zr(IV)-based metal-organic framework functionalized with amino groups (NH₂-UiO-66) has been adopted as a supporting platform to anchor gold nanoparticles (AuNPs), avoiding the migration and aggregation of AuNPs. With the addition of Hg²⁺, the formation of gold amalgam proved possible to enhance peroxidase-like activity of the composite (AuNPs/NH₂-UiO-66), accelerating the oxidization of zymolyte 3,3',5,5'-tetramethylbenzidine (TMB). In the meantime, the color of the reaction solution turned a vivid blue, and the red, green, and blue (RGB) values of the solution color changed accordingly. On account of this strategy, the quantitative detection of Hg²⁺ could be achieved. After the optimization of the experiment conditions, the average color intensity (I_c) resulting from RGB values was linear related to the concentration of Hg²⁺ from 10 to 100 nM, accompanied with a detection limit (LOD) down to 5.4 nM calculated by 3σ/S. The successful application of the designed method has been promoted to detect Hg²⁺ in some water samples, displaying a great potential in practical application. Furthermore, the use of a smartphone made our proposed method simple and accurate, and thus puts forward a possible way for in situ and real-time monitoring.