Fossil-like pollen grains for construction of UV-responsive photochromic and fluorogenic dual-functional film.

Natural pollen, one of the most fascinating biological materials in existence, exhibits chemical modifications and tunable optical property in the process of fossilization. Herein, we firstly fabricated nature-based fossil-like pollen grains (F-PGs) with UV-responsive optical properties through a facile concentrated H 2 SO 4 treatment. The F-PGs featured incomplete carbonization property while remaining the UV-active alkyl aliphatic groups, which could initiate the carbonylation of F-PGs surface under UV irradiation, thus endowing the distinct UV dose-dependent photochromic and fluorogenic dual-function of F-PGs. With the sustainable, easy-preparation and cost-effective advantages, the F-PGs were used to construct dual-functional films. The F-PG films presented high photochromic contrast (ΔE* = 32) to serve as smartphone-readable quick response code-patterned UV sensors, which indicated the highest reported cumulative dose of UV irradiation (108 J cm−2, equivalent to 10 days of exposure to sunlight). In addition, the UV-irradiated F-PG films with the fluorogenic property also showed wide applications in one-step and flexible photo-reduction of various metal ions to nanoparticles. Collectively, the novel fossil-like pollen grains and functional films pave the way for utilization of natural pollen for UV-responsive applications and provide a new insight for transporting the renewable biomass into photochromic and fluorogenic materials in the future. [Display omitted] • UV-responsive photochromic and fluorogenic F-PGs derived from natural pollen were fabricated via H 2 SO 4 treatment. • The surface carbonylation leaded to the UV-responsive optical properties of F-PGs. • F-PG film presented high photochromic contrast to provide smartphone-readable quick response code-patterned UV sensors. • F-PGs constructed UV sensors indicated the highest reported cumulative dose of UV exposure. • Fluorogenic UV-F-PG film showed applications in flexible photo-reduction of various metal ions to nanoparticles. [ABSTRACT FROM AUTHOR]