Assembly of 8-aminonaphthalene-1,3,6-trisulfonate intercalated layered double hydroxide film for the selective detection of Mg2+

A novel fluorescent film based on 8-aminonaphthalene-1,3,6-trisulfonate/layered double hydroxide composite (ANTS/LDH) has been synthesized by the electrophoretic deposition (EPD) method, and its application as an optical sensor for Mg2+ is demonstrated. The ANTS/LDH film with a thickness of 2 μm exhibits a good c-orientation of LDH platelets, which is confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ANTS/LDH film shows a good fluorescent response for Mg2+ ion. Meanwhile, a linear correlation between the fluorescence intensity of the ANTS/LDH film and the concentration of Mg2+ is obtained (I = 0.496 + 0.0708 log c (Mg2+), R2 = 0.996), with a detection limit of 2.37 × 10−7 M. The results indicate that ANTS/LDH film has a high fluorescence selectivity for Mg2+ ions, with no significant response to other metal ions, including Ca2+, Na+, K+, Fe3+, Co2+, Ni2+, or Cu2+. Furthermore, the ANTS/LDH thin film shows a good reusable ability for Mg2+ by alternately changing the solution of Mg2+ (5.0 × 10−3 M) and EDTA (8.0 × 10−2 M), and the relative standard deviation of 8 cycles is calculated as 1.7% (EDTA) and 0.14% (Mg2+). The specific fluorescence response of the film sensor is attributed to the complexation between ANTS and Mg2+, which is verified by 13C solid state NMR spectroscopy. In addition, density functional theory (DFT) calculation confirms that a strong interaction occurs between Mg2+ and ANTS molecule, which is responsible for the significant fluorescence quenching of the ANTS/LDH film. The results indicate that the ANTS/LDH thin film in this work can be used as a chemsensor for the quantitative detection of Mg2+.