Water-soluble host–guest system from β-cyclodextrin as a fluorescent sensor for aluminium ions: synthesis and sensing studies

In this paper, a simple small molecule (L) based on 4-(diethylamino)-2-hydroxy-benzaldehyde and carbohydrazide has been synthesized and characterized. Moreover, under ultrasonic conditions, a host–guest system with β-cyclodextrin and L was obtained. According to the hybridization process, the host–guest system showed excellent water solubility. The investigation of the fluorescence spectra revealed that the host–guest system exhibited a characteristic fluorescence behavior toward Al3+ in a pure water environment. Upon addition of Al3+, the host–guest system showed a strong blue fluorescence, which resulted from the fluorophore of L after the coordination of β-CD–L and Al3+ with a high binding constant (k = 3.1626 × 1011 M−1). In addition, SEM images demonstrated that the host–guest system expressed good crystallization behavior. Fluorescence microscope images of onion epidermal cells with β-CD–L–Al3+ proved that the water-soluble host–guest system possessed a high ability for cell permeability.