Humidity-Driven Color-Fluorescence Dual Switching of Naphthalenediimide Aggregates

Numerous emerging applications require precise monitoring of humidity that is not only sensitive and miniaturized but also durable and portable. However, except for the existing sensing mechanisms, such as resistive, capacitive, impedance, and voltage-based devices, little attention has been paid to exploiting dual readout modes with novel properties that can meet the requirements of simplicity and convenience. In this work, an example of color/fluorescence dual-switching by using an aggregator building block of naphthalenediimide with a porous hygroscopic polymer matrix is proposed. With an increase in the water fraction, there are obvious variations in fluorescence, driven by H-aggregation of the aggregator, and in color, driven by intramolecular-charge transfer, which facilitate the monitoring of external humidity. More importantly, the prepared humidity-sensitive switch demonstrated excellent cycling stability and reversibility. This work may shed light on the precise fabrication of aggregation-activated materials for potential applications in humidity-sensitive systems and switching devices.