Functionalization of mesoporous silica membrane with a Schiff base fluorophore for Cu(II) ion sensing

Abstract

A Schiff base (SB) immobilized hybrid mesoporous silica membrane (SB-HMM) was prepared by immobilizing a Schiff base onto the pore surface of mesoporous silica (pore size = 3.1 nm) embedded in the pores of a porous anodic alumina membrane. In contrast to the non-fluorescent analogous SB molecule in homogeneous solutions, SB-HMM exhibited intense fluorescence due to emission enhancement caused by aggregation of SB groups on the pore surface. The high quantum efficiency of the surface SB groups allows SB-HMM to function as a fluorescent sensor for Cu(II) ions in an aqueous solution with good sensitivity, selectivity and reproducibility. Under the optimal conditions described, the linear ranges of fluorescence intensity for Cu(II) are 1.2–13.8 (M ( R 2 = 0.993) and 19.4–60 ( R 2 = 0.992) (M. The limit of detection for Cu(II) is 0.8 μM on basis of the definition by IUPAC ( C LOD = 3.3 S b/ m).