Accessing color-tunable afterglows from single conventional chromophore-based polysaccharide films through palette strategy

Achieving multicolor afterglow modulation from single conventional chromophore-based room temperature phosphorescence (RTP) materials is attractive but challenging. Herein, a facile palette strategy based on physical doping of red afterglow-emitted chromophore (N8) into sodium alginate (SA) is proposed to achieve large range of multicolor afterglow modulation for single conventional chromophore-based RTP materials. As well as being a key luminous component in the color palette, SA with cyan afterglow (upon 254 nm UV irradiation) can also activate the red afterglow of N8 via strong hydrogen bond interactions. Through regulating the doping ratios of N8 to SA, cyan to red afterglows have been achieved in the formed amorphous N8/SA films. Significantly, the afterglow of N8/SA also exhibits excitation wavelength- and time-dependent characteristics, which further extend the range and tunability of afterglow color. Besides, the phosphorescence lifetime of N8-based SA films could be further improved by chemically grafting N8 to SA, with a lifetime of 464.9 ms. Considering the excellent multicolor afterglow tunability and hygrothermal responsiveness, these smart SA-based materials demonstrate great application prospects in information encryption, anti-counterfeit ink painting, and 3D afterglow aerogel.