Tailor-made micro-object optical sensor based on mesoporous pellets for visual monitoring and removal of toxic metal ions from aqueous media

Methods for the continuous monitoring and removal of ultra-trace levels of toxic inorganic species (e.g., mercury, copper, and cadmium ions) from aqueous media such as drinking water and biological fluids are essential. In this paper, the design and engineering of a simple, pH-dependent, micro-object optical sensor is described based on mesoporous aluminosilica pellets with an adsorbed dressing receptor (a porphyrinic chelating ligand). This tailor-made optical sensor permits ultra-fast (≤ 60 s), specific, pH-dependent visualization and removal of Cu²⁺, Cd²⁺, and Hg²⁺ at sub-picomolar concentrations (∼10^-11 mol dm^-3) from aqueous media, including drinking water and a suspension of red blood cells. The acidic active acid sites of the pellets consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures densely coated with the chelating ligand. The sensor can be used in batch mode, as well as in a flow-through system in which sampling, target ion recognition and removal, and analysis are integrated in a highly automated and efficient manner. Because the pellets exhibit long-term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be expected to be useful for the fabrication of inexpensive sensor devices for naked-eye detection of toxic pollutants. A simple, micro-object optical sensor is engineered based on mesoporous aluminosilica pellets with an adsorbed dressing receptor. This tailor-made optical sensor permits ultra-fast (≤60 s), specific, pH-dependent visualization and removal of ultra-trace concentrations (∼10^-11 mol dm^-3) from aqueous media. Pellet-based micro-object sensing devices can be expected to be important for use in portable and remote sensing systems, especially for household use, where instrumental methods are prohibitively expensive.