New dual colorimetric/fluorimetric probes for Hg²⁺ detection & extraction based on mesoporous SBA-16 nanoparticles containing porphyrin or rhodamine chromophores

Multifunctional luminescent nanomaterials based on mesoporous silica SBA-16 doped with a ring-opening rhodamine derivative (RhNHS) or with a cationic porphyrin bearing imidazolium substituents (Porph) were successfully obtained and characterized. The non-immobilized Porph leads to a selective colorimetric detection for Cu²⁺, Pb²⁺ and Hg²⁺ in HEPES buffer at pH 7, producing colour changes from violet to pink, green and brown, detecting the minimal amount of 3.6, 5.8 and 3.8 ppm by absorption, respectively. The new approach afforded solid-state devices that showed a colorimetric and fluorometric response towards toxic metal ions, such as Cu²⁺, Pb²⁺ and Hg²⁺, with a naked-eye detection of 5 ppm for SBA-16@Porph. A minimal detectable amount of 2 ppb, confirmed by ICP-AES, was achieved with both hybrid nanosystems for Hg²⁺, and extraction values of Hg²⁺ in water were higher than 70%. Moreover, SBA-16@Porph was successfully applied for Hg²⁺ remediation in water, being able to extract the amount of 69 mg/g (0.86 mmol/g).