Advances in lanthanide-doped upconversion nanomaterials in security inks: a comprehensive review

Abstract Smart functional materials with intriguing optical properties play a crucial role due to their diverse applications in anticounterfeiting solutions. This review addresses the challenges posed by different counterfeiting activities and introduces various techniques to contest the ever-growing threats. The focus is primarily on potential lanthanide-doped upconversion nanomaterials, which are engineered to create different versions of security inks as countermeasures for counterfeiting. Furthermore, the evolution of these nanomaterials is discussed, showcasing their contribution towards enhancing the complexity of anticounterfeit solutions. The article also discusses the limitations and future scope of synthesizing smart nanomaterials to tackle counterfeiting issues. This comprehensive review will be beneficial in developing futuristic anticounterfeit solutions by exploiting the unique features of Ln-doped nanomaterials to the demanding and challenging field of anti-counterfeiting through security inks. Graphical abstract