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Cyclodextrin-Assisted Two-Component Sonogel for Visual Humidity Sensing

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journal contribution
posted on 11.01.2017, 00:00 by Xudong Yu, Xiaoting Ge, Lijun Geng, Haichuang Lan, Jujie Ren, Yajuan Li, Tao Yi
In this work, two naphthalimide-based compounds, 1a and 1b, have been designed and synthesized. Both compounds can form stable two-component gels in n-propanol or n-butanol upon addition of α-cyclodextrin (α-CD) followed by sonication at room temperature. Interestingly, the 1a/α-CD gel is thixotropic and very sensitive to water. Addition of a small amount of water induces rapid gel collapse, allowing further development of the gel as a visual relative humidity sensor. Specificity of the sensor has been confirmed using several approaches, such as scanning electron microscopy and fluorescence, Fourier transform infrared, and 1H NMR spectroscopy experiments. The results show that α-CD acts as a junction for the assembly of 1a or 1b through hydrogen bonding between hydroxyl and amide groups. Upon addition of water, α-CD interacts with the adamantane group of 1a via an incomplete host–guest encapsulation, resulting in the dissociation of the hydrogen-bonding-assisted two-component assembly, accompanied by gel collapse.