Solid-state intramolecular motions in continuous fibers driven by ambient humidity for fluorescent sensors

One striking feature of molecular rotors is their ability to change conformation with detectable optical signals through molecular motion when stimulated. However, due to the strong intermolecular interactions, synthetic molecular rotors have often relied on fluid environments. Here, we take advantage of the solid-state intramolecular motion of aggregation-induced emission (AIE) molecular rotors and one-dimensional fibers, developing highly sensitive optical fiber sensors that respond to ambient humidity rapidly and reversibly with observable chromatic fluorescence change. Moisture environments induce the swelling of the polymer fibers, activating intramolecular motions of AIE molecules to result in red-shifted fluorescence and linear response to ambient humidity. In this case, polymer fiber provides a process-friendly architecture and a physically tunable medium for the embedded AIE molecules to manipulate their fluorescence response characteristics. Assembly of sensor fibers could be built into hierarchical structures, which are adaptive to diverse-configuration for spatial-temporal humidity mapping, and suitable for device integration to build light-emitting sensors as well as touchless positioning interfaces for intelligence systems.

Automated summary

This study utilizes solid-state intramolecular motion of AIE molecular rotors and fibers to develop highly sensitive optical fiber sensors responsive to ambient humidity with observable chromatic fluorescence change. The sensors provide a linear response to humidity by inducing intramolecular motions of AIE molecules through swelling of polymer fibers in moisture environments. This approach offers a process-friendly architecture and physically tunable medium for manipulating fluorescence response characteristics, allowing for hierarchical sensor structures adaptable for spatial-temporal humidity mapping and device integration for light-emitting sensors and touchless positioning interfaces.