[A Fluorescent Chemical Sensor Based on MgAl-8-HQ LDH Composite Particle for the Selective Detection of Fe3+]

In order to achieve the highly selective and Simple detection for ferric ion, strong-fluorescent 8-hydroxyquinoline (8-HQ) Mg-Al layered double hydroxide(Mg(χ)Al-8-HQ LDH) was designed and prepared by 8-HQ's intercalation and ready coordination based on adjustment of Al3+ on Mg-Al layered double hydroxides (MgAl LDH) laminates. Meanwhile its structure and property were characterized by IR, XRD, UV-Vis and fluorescent spectrometer. IR analysis showed coordinate bonds of C-O-Al and C-N-Al between 8-HQ and Al3+ were generated. XRD revealed that 8-HQ had already inserted in MgAl LDH laminates, and it made (003) diffraction peaks move to low 2θ angle direction, and the diffraction peak intensity was enhanced with the molar ratio of Mg and Al increasing. Because the coordination reaction between 8-HQ and Al3+ in MgAl LDH laminates took place, it induced the absorption peak of 8-HQ at 314 nm disappeared, at the same time the transition absorption peak at 376 nm between metal ions and ligands appeared. As demonstrated by fluorescence spectroscopic analysis, fluorescence intensity of Mg(χ)Al-8-HQ LDH increased with the content of Al3+ reducing, when the molar ratio of Magnesium and Aluminium ion is 4 : 1, its fluorescence intensity enhanced more significantly than 8-hydroxyquinoline aluminum. Through the research on the influence of metal ions on the fluorescence spectra of Mg4 Al-8-HQ LDH particle, it was found that the particle to metal ions exhibited significant selection and difference, especially with high selectivity for Fe3+ ion. The effect of [Fe3+] on the color and fluorescence intensity of Mg4Al-8-HQ LDH particle solution was further studied, and the results showed that the solution varied from light yellow to dark green with the content of Fe3+ in 10(-6) to 10(-2) mol x L(-1) increasing, so it can implement colorimetric sensing for Fe3+ in the above range. And at the same time its fluorescence intensity significantly decreased, and its fluorescence could be completely quenched, when [Fe3+] was 10(-3) mol x L(-1). When -log[Fe3+] was in 3 to 6, negative correlation function appeared between -log[Fe3+] and its fluorescence intensity, so it could implement fluorescence sensing detection for Fe3+ with high selectivity and sensitivity. According to the above research results, a new method of fluorescent and colorimetric dual sensor detection of Fe3+ by Mg4Al-8-HQ LDH particle was successfully established.