Mechano-responsive and acid stimuli-responsive luminescence of a hydrogen-bonded organic frameworks

Abstract

Stimuli-responsive materials are capable of changing their chemical or physical properties when exposed to external stimuli, showing a wide range of potential applications such as drug delivery, sensing, smart coatings, and artificial muscles. Here, a micron-sized hydrogen-bonded organic framework PFC-1 was constructed and its mechanical and acid stimuli-responsive luminescence were investigated. It was found that the fluorescence of PFC-1 aqueous suspension is affected HCl concentrations. The pristine PFC-1 aqueous suspension exhibits an emission peak with high fluorescence intensity at 440 nm and two weak emission shoulders at 475 nm and 535 nm, respectively. Upon the addition of hydrochloric acid, there is a gradual reduction in the peak intensities at 440 nm and 475 nm, while the peak intensity at 535 nm remains relatively unchanged, resulting in a progressive shift in fluorescence color from blue to green. Mechanical grinding induces approximate 30 nm blue-shift in the fluorescence emission peak, a change that is reversible upon immersing the powder in ethanol for 60 min. This work contributes to the development of stimuli-responsive hydrogen-bonded organic framework materials with potential applications in acid and pressure fluorescence sensing.