Gas sensing by long-wavelength and long-afterglow pectin/melamine-formaldehyde aerogel via resonance energy transfer

The exploration of pure organic ultra-long room temperature phosphorescence (RTP) materials has emerged as a research hotspot in recent years. Herein, a simple strategy for fabricating long-afterglow polymer aerogels with three-dimensional ordered structures and environmental monitoring capabilities is proposed. Based on the non-covalent interactions between pectin (PC) and melamine formaldehyde (MF), a composite aerogel (PCMF@phenanthrene) (PCMF@PA) doped with phosphorescent organic small molecules was constructed. It exhibits a stable and persistent afterglow, with a phosphorescence lifetime reaching up to 1.99 s. Simultaneously, this aerogel possesses excellent mechanical properties, having a compressive modulus of 4.14 MPa, which is 490.8 times that of the PC aerogel. Its friction coefficient is also much lower than that of the single MF aerogel, enabling the material to achieve a better balance between rigidity and service life in practical applications. Moreover, through resonance energy transfer, the afterglow wavelength was redshifted from 504 nm to 576 nm and 620 nm, and aerogels with ultra-long yellow and red afterglows were successfully obtained. PCMF@PA aerogels display specific chemical stability in different organic solvents. Notably, PCMF@PA has a characteristic recognition for formic acid gas. The change in the luminous intensity and lifetime of the aerogel after gas absorption distinguishes it from gases such as ammonia and acetic acid. These phosphorescent polymer aerogels with self-monitoring and tracing capabilities not only foster the advancement of ordered phosphorescent materials but also broaden the application scope of RTP materials in environmental monitoring.