take the superiorities in processability, biocompatibility, rich source, wide variety, and low cost. [7] Generally, achieving pure organic p-RTP follows two criteria: i) promotion of intersystem crossing (ISC) through aggregation [8] and introduction of carbonyl, heteroatoms, and heavy atoms; [7] ii) suppression of the nonradiative relaxation processes (vibration or external quenchers). [7,9] Specifically, for the latter, various approaches, including crystal engineering, [10] host-guest doping or complexation, [11] H-aggregation, [2a,3b,12] construction of metal-organic framework and perovskite hybrids, [13,14] and ionic or ionic-π interactions, [15] were centrally developed. Currently explored systems, however, are predominantly molecular organic crystals, whose amorphous states show weakened or even disappeared p-RTP, [16] thus hampering their practical applications. To overcome these drawbacks, amorphous (p-) RTP systems were developed, which generally create rigid environment through powerful intermolecular interactions. [11a,b,17-20] Nevertheless, the color tunability in a wide-range remains a daunting challenge. Therefore, further development of versatile platforms to realize distinct p-RTP emissions from blue to red is highly desired. [21] On the other hand, most of these p-RTP materials just show a single emission color, and only scattered examples demonstrating excitation-dependent [4] or time-dependent emissions [22] were reported. If the afterglow color can vary with time, it would empower the materials with rich encryption modes in security protection, thus promoting more reliable protection at much higher levels. [22] For example, Chi et al. reported the first example with time-dependent afterglow colors through weak intermolecular hydrogen-bonding interaction. [22a] And very recently, Yang and coworkers reported similar phenomenon that originates from well-separated thermally activated delayed fluorescence (TADF) and p-RTP with comparable but different lifetimes. [22b] Meanwhile, as an alternative to molecular p-RTP compounds, polymers are even more attractive on account of their film-forming ability, which is favorable for diverse technical applications with flexibility and ease processing procedures. [23] However, the development of a simple approach to fabricate amorphous polymers with color-tunable and multicolor p-RTP in response to excitation wavelength (λ ex), particularly those also accompanying time-dependent afterglows, remains highly challenging. Here we report such system based on sodium Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains...

Smart afterglow materials in response to excitation and delay time, including crystals, polymeric films, and carbon dots, have attracted considerable attention on account of their fundamental value in photophysics and promising applications in optoelectronics. However, the fabrication of amorphous and flexible polymer films with fine control remains underexplored. Herein, new doped polymer films based on sodium alginate and aromatic carboxylates are developed, which demonstrate following advantages: (i) easy and fast fabrication through the aqueous solution process, (ii) flexible, transparent, and re‐dissolvable characteristics, (iii) multi‐tunable afterglow colors from blue to red and even white with fine control. Specifically, even better controllability can be achieved through co‐doping and triplet‐to‐singlet Förster resonance energy transfer (TS‐FRET). Multimode advanced anti‐counterfeiting of these materials is demonstrated using their excitation‐ and time‐dependent as well as TS‐FRET‐mediated afterglow colors.

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