Modification of silica nanoparticles with fluorescein hydrozide for Cu(II) sensing

Fluorescein hydrozide modified silica nanoparticles (FH-SNPs, 280-550 nm) were prepared by covalently immobilizing a fluorescein hydrozide (FH) derivative containing organosilyl ligands onto the surface of silica nanoparticles. FT-IR, elemental analysis, SEM microscopy and steady-state fluorescence anisotropy were used to characterize the functionalized FH-SNPs. Upon the addition of Cu(II), the spirolactam ring of FH moiety on the silica surface was opened and a fluorescent product was formed, exhibiting a selective Cu(II)-amplified fluorescence signal. Under the optimized conditions, the linear range of fluorescence intensity for Cu(II) is 5-80 mu M (R-2 = 0.992), and the limit detection for Cu(II) is 1.0 mu M according to IUPAC definition (C-LOD = 3.3S(b)/m). (C) 2012 Elsevier Ltd. All rights reserved.