Highly sensitive
stimuli-responsive fluorescent films are playing
an increasingly important role in the development of smart sensors
and erasable optical devices. However, systems involving humidity-responsive
fluorescence (HRF) are still very limited compared to those responsive
to other common environmental stimuli (e.g., light, heat, pressure,
or pH). Herein, by incorporating the 4-[4-(dimethylamino)styryl]pyridine
chromophore into a polyvinylpyrrolidone host, we have developed new
flexible self-supporting nanofiber films that exhibit fast and obvious
HRF. The reversible transformation between two fluorescence states
can be easily observed and recycled at least 200 times. Fluorescence
microscopy images provided in situ evidence of changes in both fluorescence
and morphology. This work therefore offers an alternative to conventional
humidity sensors based on changes in color and electrical properties.
Furthermore, we anticipate that these HRF films can also be employed
as optical antiforgery materials
