Influence of Gas Adsorption on the Luminous Properties of Layered Double Hydroxide/Anionic Fluorescein Dye Hybrid Thin Solid Films

Abstract

Abstract Layered double hydroxide (LDH)/anionic fluorescein dye (AFD)/1-butanesulfonate (C4S) hybrid thin solid films prepared by immersing LDH thin films in aqueous solutions of AFD and C4S were investigated as sensing materials for relative humidity (RH) and/or various organic vapors. The basal spacing, i.e., the d003 value, of the LDH/AFD/C4S hybrid films under wet conditions became larger than that under dry conditions when water was adsorbed into the interlayer space. The intensity of photoluminescence (PL) from the AFD incorporated into the hybrid also increased upon water adsorption. This PL intensity exhibited a maximum value at 10% RH and was constant when the RH exceeded 20%. This behavior is explained by an increase in the population of dianionic AFD caused by water adsorption. The PL intensity of the LDH/AFD/C4S hybrid thin solid films also increased in the presence of alcohol vapor and became larger than under wet conditions. Moreover, the PL intensity also depended on the species of alcohol. Specifically, the PL intensity decreased in the presence of nonpolar organic solvent vapors. Therefore, the present hybrid materials can be used as a sensor for relative humidity and polar organic solvent vapors.