Assembly of layered double hydroxide/ANTS ultrathin film and its application as a biosensing material

The fluorescent ultrathin films (UTFs) based on layered double hydroxide/8-amino-1,3,6-naphthalenetrisulfonate (LDH/ANTS) have been prepared by employing a layer-by-layer assembly technique, and its application as an optical biosensor for dextran-40 was demonstrated. UV–vis spectroscopy, fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy have been adopted to monitor the assembly process. The UTFs display a continuous and uniform morphology, with a long-range ordered structure. It was found that the UTFs can be used for dextran-40 sensing in the concentration range 1.0 × 10−5 to 1.0 × 10−2 M, and the detection limit of 2.7 × 10−6 M is obtained. Good selectivity toward dextran-40 over other saccharides, including glucose, fructose and sucrose, has been demonstrated. Furthermore, the UTFs show a good reusable ability for dextran-40 by recovering the UTFs in a H2O2 aqueous solution (1.0 × 10−4 M), with the relative standard deviation of 4.18% toward dextran-40 for 10 cycles. The fluorescence response of the film sensor is attributed to a strong interaction between ANTS and dextran-40, which was verified by XPS, Raman and polarized photoemission spectroscopy, accounting for the significant fluorescence quenching of the LDH/ANTS film. The results indicate that the LDH/ANTS UTFs in this work can be used as a biosensor for the detection of dextran-40.