High-yield upcycling of feather wastes into solid-state ultra-long phosphorescence carbon dots for advanced anticounterfeiting and information encryption.

Recently, biomass-derived carbon dots (CDs) have attracted considerable attention in high-technology fields due to their prominent merits, including brilliant luminescence, superior biocompatibility, and low toxicity. However, most of the biomass-derived CDs only show bright fluorescence in diluted solution because of aggregation-induced quenching effect, hence cannot exhibit solid-state long-lived room-temperature phosphorescence (RTP) in ambient conditions. Herein, matrix-free solid-state RTP with an average lifetime of 0.50 s is realized in the CDs synthesized by one-pot hydrothermal treatment of duck feather waste powder. To further enhance RTP lifetime, hydrogen bonding is introduced by employing polyols like polyvinyl alcohol (PVA) and phytic acid (PA), and a bimodal luminescent CDs/PVA/PA ink is exploited by mixing the CDs and polyols. Astonishingly, the CDs/PVA/PA ink screen-printed onto cellulosic substrates exhibits unprecedented green RTP with average lifetime of up to 1.97 s, and the afterglow lasts for more than 14 s after removing UV lamp. Such improvement on RTP is proposed to the populated excited triplet excitons stabilized by rigid chains. Furthermore, the CDs/PVA/PA ink demonstrates excellent potential in anticounterfeiting and information encryption. To the best of the authors' knowledge, this work is the first successful attempt to fabricate matrix-free ultra-long RTP CDs by reclamation of the feather wastes for environmental sustainability.