Hydrothermal synthesis and protonation of Sc/Glu-PMs based organic–inorganic amorphous microstructures for enhanced phosphorescence and optical applications

Scandium-glutamic acid phosphorescent materials (Sc/Glu-PMs) were synthesized via a simple one-pot hydrothermal process using Sc 3+ ions and glutamic acid ligands. Structural characterization confirmed that the obtained material is an amorphous organic-inorganic composite rather than a crystalline coordination polymer. Compared with pure glutamic acid, Sc/Glu-PMs exhibited significantly enhanced room-temperature phosphorescence (RTP), attributed to coordination-induced structural rigidity that suppresses non-radiative decay pathways and stabilizes triplet excitons. Post-synthetic protonation using dilute hydrochloric acid further improved the phosphorescence quantum yield (PQY) from 7.63% to 11.07%, although a moderate decrease in phosphorescence lifetime was observed, indicating enhanced radiative decay efficiency after protonation. Surface and spectroscopic analyses suggest that protonation modifies the hydrogen-bonding environment and local surface chemistry without disrupting the bulk structure. The prepared materials also demonstrated promising optical information encryption performance, including high contrast, persistent afterglow, and good photostability under repeated UV on/off cycles. This work provides a simple coordination-protonation strategy for regulating RTP behavior in amino acid-based organic-inorganic systems for potential anti-counterfeiting and optoelectronic applications.