Tunable photoluminescence properties of fluorescein in a layered double hydroxide matrix and its application in sensors

Abstract

This paper reports the preparation of a tunable photoluminescence film through incorporation of fluorescein into a layered double hydroxide matrix, as well as its application in electrocatalysis for dopamine. The fluorescein (FLU) and 1-heptanesulfonic acid sodium (HES) with different molar ratios were co-intercalated into the galleries of Zn₂Al LDH by the anion exchange method. Thin films of FLU-HES/LDH (x%, x stands for the molar percentage of fluorescein), which possess good c-orientation of LDH platelets confirmed by XRD and SEM, were obtained by the solvent evaporation method on ITO substrates. It was found that the fluorescence wavelength, emission intensity and lifetime correlate with the orientation and aggregation state of FLU in the LDH gallery, and can be finely controlled by varying the fluorophore content through changing the molar ratio of FLU/HES. In addition, the FLU-HES/LDH thin film modified electrode exhibits electrocatalytic performances for dopamine with rather high sensitivity and selectivity. The optimal luminous intensity, the longest fluorescence lifetime and the superior electrocatalytic behavior for dopamine of FLU-HES/LDH (x%) can be obtained with x values ranging in 1.25 × 10⁻²–2.00 × 10⁻²%.