Tunable multi-color room-temperature phosphorescence via melamine-based supramolecular self-assembly for anti-counterfeiting and humidity sensing

Abstract

Herein, we report a novel multi-component supramolecular self-assembly strategy for the development of tunable multi-color room-temperature phosphorescent (RTP) materials with dual functionalities. Unlike conventional single-matrix systems, our approach synergistically integrates a melamine (M) host, furoic acid (Fa), metal ions (Ba²⁺ or Zn²⁺), and organic dopants to achieve unprecedented control over emission properties. The assembled MFa-B (with BaCl₂) exhibits bright green afterglow (phosphorescence lifetime: 233 ms, afterglow time: 1.6 s), while MFa-Z (with ZnCl₂) shows an orange-red emission (phosphorescence lifetime: 256 ms, afterglow time: 1.7 s). Notably, MFa-Z demonstrates a highly sensitive and linear response (R² = 0.9840) to relative humidity (35%–75%), a functionality rarely achieved in organic RTP materials. Furthermore, by doping MFa-B with acridone (A) or acridoneacetic acid (AAc), we obtained cyan (MFa-B–A) and blue (MFa-B–AAc) afterglow with a significantly extended afterglow time of 3.0 s. The enhanced RTP performance is attributed to the rigid hydrogen-bonded framework that suppresses non-radiative decay, and the metal ions that promote intersystem crossing. Structural and thermal analyses confirm successful assembly and high stability. This work not only presents a straightforward and effective strategy for creating multi-functional RTP materials but also demonstrates their practical application in advanced anti-counterfeiting and visual humidity sensing, paving the way for next-generation smart luminescent systems.