A facile method to construct dual-responsive organogels with color changes

Abstract

A novel organogel that is dually responsive to pH and Li⁺ was facilely constructed from mixtures of β-cyclodextrin, thymolphthalein and sodium formate in N,N′-dimethylacetamide. Acidity (pH) can trigger a color change of the organogels between a transparent colorless state and a dark-blue state due to the presence of thymolphthalein. It is interesting that Li⁺ could decompose the gel system while Na⁺ and K⁺ do not disturb the gelatinous state. Scanning electron microscopy (SEM) images show that these organogels are composed of fibrous structures. These organogels possess relatively high viscoelasticity indicated by rheology measurements. A mechanism for the gel formation is proposed based on the results of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The systems could be expected to act as non-liquid materials for sensing with the naked eye.