Multicolor Emitting Lanthanide‐Doped Sr ₂ BiF ₇ Nanocomposites With Multi‐Layered Information Encoding for Next‐Generation Anticounterfeiting Systems

ABSTRACT One of the biggest challenges in anti‐counterfeiting applications remains the development of sophisticated luminescent materials with an excellent safety profile and easy production. In this manuscript, a series of lanthanide‐doped Sr 2 BiF 7 (SBF) nanomaterials, i.e., SBF:Eu 3+ ; SBF:Tb 3+ ; SBF:Yb 3+ , Ho 3+ ; SBF:Yb 3+ , Tm 3+ , and their nanocomposites were prepared via hydrothermal method. These nanocomposites demonstrate excitation‐dependent luminescence behavior exhibiting pear green and imperial blue upconversion (UC) emission under 980 nm laser. Whereas, they emit red claret from Eu 3+ under 254 nm UV light, sea green from Tb 3+ , and steel blue from the undoped material under 365 nm UV light, and a phlox emission resulting from the combined contributions of Eu 3+ and the host material under 395 nm excitation. Additionally, a low‐cost, simple screen printing method was used to successfully manufacture and apply stable fluorescent inks based on polyvinyl chloride (PVC) to different surfaces in order to produce a range of anti‐counterfeiting patterns. Interestingly, these printed patterns are barely apparent in normal light, but when exposed to excitation sources at 980, 395, 365, and 254 nm, they emit different colors. Because of their exceptional stability and unique multicolor luminescent qualities, newly developed multimodal composite materials offer low‐cost, multi‐layered security for authentic products against counterfeiting.