Competition of DTH-Fe3O4@SiO2 towards cations and reversibility of DTH-Fe3O4@SiO2 towards Zn2+. (A) Fluorescent emission changes of DTH-Fe3O4@SiO2 (0.3 g/L) upon addition of 1, blank; 2, Zn2+; 3, Na+; 4, Na+ + Zn2+; 5, K+; 6, K+ + Zn2+; 7, Ca2+; 8, Ca2+ + Zn2+; 9, Mg2+; and 10, Mg2+ + Zn2+ (each metal ion is 100 μM) in ethanol at room temperature. (B) Fluorescence spectra of DTH-Fe3O4@SiO2 (0.3 g/L) in (a) without, (b) with Zn2+ (1.0 × 10-4 M), and (c) after treatment with EDTA (2.5 × 10-4 M) in (b) solution. The inset picture shows the photograph of DTH-Fe3O4@SiO2 with Zn2+ by treatment of EDTA (2.5 × 10-4 M) under a 365-nm UV light.
Wang et al. Nanoscale Research Letters 2012 7:86 doi:10.1186/1556-276X-7-86