Portable smartphone-assisted highly sensitive detection of mercury ions based on gold nanoparticle-modified NH-UiO-66 metal-organic framework.

A novel portable smartphone-assisted colorimetric method was reported for the determination of Hg with good analytical performance. A Zr(IV)-based metal-organic framework functionalized with amino groups (NH-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 Hg, the formation of gold amalgam proved possible to enhance peroxidase-like activity of the composite (AuNPs/NH-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 Hg could be achieved. After the optimization of the experiment conditions, the average color intensity (I) resulting from RGB values was linear related to the concentration of Hg 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 Hg 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.