An inorganic–organic hybrid optical sensor for heavy metal ion detection based on immobilizing 4-(2-pyridylazo)-resorcinol on functionalized HMS
2012
Liu, Tongge | Li, Gang | Zhang, Na | Chen, Yongying
A novel and low-cost optical sensor for heavy metal ion detection has been prepared by immobilizing 4-(2-pyridylazo)-resorcinol (PAR) on the functionalized hexagonal mesoporous silica (HMS) via N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAC). The successful fabrication of this optical sensor is confirmed by extensive characterizations using FT-IR, low angle X-ray diffraction (XRD), UV–vis spectroscopy and N₂ sorption, meanwhile its colorimetric properties, selectivity, sensitivity and reversibility are also investigated. The optical sensor responds selectively to heavy metal ions, such as Fe³⁺, Cd²⁺, Ni²⁺, Zn²⁺, Pb²⁺, Co²⁺, Hg²⁺ and Cu²⁺ with a color change from yellow to orange or purple in alkaline solutions, while it shows a color change only for Cu²⁺ under strongly acidic conditions. At pH 12.0, this optical sensor has a high sensitivity that makes it possible to detect Cu²⁺ in aqueous solution with the detection limit as low as 40ppb by naked-eye. This optical sensor also shows excellent reversibility and regeneration by treatment with a solution of EDTA.
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