Fluorescence-enhanced optical sensor for detection of Al3+ in water based on functionalised nanoporous silica type SBA-15

An organic–inorganic hybrid optical sensor (PQ-SBA-15) was designed and prepared through functionalisation of the SBA-15 surface with 3-piperazinepropyltriethoxysilane followed by covalently attaching 8-hydroxyquinoline. Characterisation techniques, including FT-IR, thermal gravimetric, N2 adsorption-desorption and X-ray powder diffraction analyses, showed that the organic moieties were successfully grafted onto the surface of SBA-15 without the SBA-15 structure collapsing. The evaluation of the sensing ability of PQ-SBA-15 using fluorescence spectroscopy revealed that the PQ-SBA-15 was a selective fluorescence enhancement-based optical sensor for Al³⁺ in water in the presence of a wide range of metal cations including Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ with a limit of detection of 8.8 × 10–7 M. In addition, good linearity was observed between the fluorescence intensity and the concentration of Al³⁺.