Cellulose-based environment-friendly smart materials for colorimetric and fluorescent detection of Cu2+/Fe3+ ions and their anti-counterfeiting applications

Copper and iron play an important role in many biological processes in humans, animals and plant life. Hence, it is critical to observe the copper and iron ions concentration by a precise, fast, selective and an applied method. Herein, a multifunctional cellulose-based smart fluorescent material (Lum-MDI-CA) with extended conjugation structure was designed and synthesized for the fast, sensitive and dual mode detection of Cu2+ and Fe3+ ions. The 5-amino-2,3-dihydrophthalazine-1,4'-dione (Luminol, here after; Lum) was used as a fluorophore and 4,4'- methylene diphenyl diisocyanate (MDI) was used as a cross-linking agent. Remarkably, the polymer material not only worked as an outstanding sensor for the effective detection and removal of Cu2+ ions and Fe3+ ions but also demonstrated unique characteristics for security printing applications. Moreover, the extended conjugation was ceased upon meeting with Cu2+ and Fe3+ ions resulting in decreased fluorescence intensity. The results were fully supported by DFT calculations. In addition, the material and its polymer blend were efficiently fabricated into flexible fluorescent films, smart inks and demonstrated anti-counterfeiting applications. To our knowledge, this is the first study for the preparation of luminol-modified biopolymer-based environment-friendly sensor for the removal of hazardous metals from environment.