SDC/OS-LDH composite for highly sensitive fluorescence detection of Fe3+ at a much lower concentration

In this work, we demonstrate the tunable luminescence of newly synthesized SDC/OS Mg/Al-LDH composites (SDC is 4,4 '-stilbenedicarboxylic acid; OS is 1-octanesulfonic acid sodium; LDH is layered double hydroxide) and their application in fluorescence sensing to detect Fe(iii) ions. Through an ion-exchange method, the SDC(2-)and OS(-)anions with changed molar ratios are intercalated into the LDH interlayers to obtain composites of SDCxOS1-x-LDH (x= 0.02, 0.05, and 0.10). In the solid state, the optimized SDC0.05OS0.95-LDH exhibits a blue emission (441 nm) with a 54 nm blue-shift compared with SDC-Na solid salt (495 nm). In a delaminated state, the colloidal suspension of SDC0.05OS0.95-LDH in formamide (FM) also gives a blue emission at 444 nm in comparison to the 451/468 nm emissions of the FM solution of free SDC(2-)anions, and the luminescence intensity of the exfoliated composite is similar to 28 times higher than that of the SDC(2-)anions. The SDC0.05OS0.95-LDH composite could be utilized in chemical fluorescence sensing for detecting Fe(3+)ions. In aqueous solutions with extremely low Fe(3+)concentrations of 0.18-1.78 mu M (0.01-0.1 ppm), the composite gives a large quenching constant of 2.34 x 10(5)M(-1), and an ultralow detection limit of 6.12 x 10(-8)M. This work may provide a highly effective while simple method for the detection of Fe(3+)in a small concentration range.