A selective optical sensor for antimony based on hexagonal mesoporous structures.

Mesostructured materials show promise in fabricating ordered sensing systems in a reproducible manner. Here, the fabrication of optically selective and sensitive sensors up to subnanomolar concentrations of Sb(III) ions was reported via simple and reproducible techniques in which the hexagonal mesoporous silicas in powder and monolith forms were used as probe carriers. Evidence of successful fabrication of the optical sensors was investigated by extensive characterizations using powder X-ray diffraction, nitrogen adsorption/desorption isotherms, 29Si NMR spectroscopy, and transmission electron microscopy. The mesostructured features allowed high adsorption capacity and accessibility of probe molecules and efficient transport of toxic species via much more direct and easier diffusion to the network sites without significant alteration of their physical characteristics, leading to excellent sensing systems in terms of stability and sensitivity with rapid response time of detection. In addition, the high performance of the hexagonal sensors was dependent on key factors such as the number of support-based sensors, the reaction temperature, and the pH value that led to possible naked-eye detection of Sb(III) ion concentration with a detection limit as low as 3x10(-9) mol/dm3 and a wide detection range of 1 ppb-2 ppm. Of particular interest was that our mesostructured sensor design provided control over the retention of the potential functionality of the naked-eye sensing system of Sb(III) ions upon the storage and even after several regeneration and reuse cycles, indicating large-scale reversibility of sensing systems.