Visual monitoring and removal of divalent copper, cadmium, and mercury ions from water by using mesoporous cubic Ia3d aluminosilica sensors

The design of a simple, pH-dependent, micro-object optical sensor based on mesoporous Ia3d aluminosilica pellets functionalized by a porphyrinic chelating ligand for the monitoring and removal of ultra-trace levels of toxic metals, such as Hg(II), Cu(II), and Cd(II), from aqueous media, such as drinking water and biological fluids, is described in this study. This micro-object optical sensor has large surface area-to-volume ratios and uniformly shaped pores in three-dimensional (3D) nanoscale gyroidal structures, and its active sites consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures. These mesostructures are densely coated with chelating ligand to permit ultra-fast, specific, pH-dependent visualization and the removal of toxic metals at sub-picomolar concentrations (∼10^-11 mol dm^-3) from aqueous media, including drinking water and a suspension of red blood cells, via a colorimetric signal visible to the naked eye, as well as via UV-Vis reflectance spectroscopy. The adsorption of metal ions forms a monolayer on the interior pore surfaces of the pellets in this sensor system. Given that the pellets exhibit long-term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be useful for the fabrication of inexpensive sensor devices for naked-eye detection of toxic pollutants. Furthermore, the usage of the pellets to remove metal ions from a physiological fluid (i.e., blood cells) was evaluated.