Upconversion Nanoparticles@Carbon Dots@Meso-SiO2 Sandwiched Core–Shell Nanohybrids with Tunable Dual-Mode Luminescence for 3D Anti-Counterfeiting Barcodes

inks with a dual-mode and tunable luminescence nature endow the inkjet-printing barcodes with an extremely high encoding capacity and high security. Such dual-mode fluorescent inks and barcodes are simple to fabricate, easy to view, efficient for coding, and difficult to clone, thus making them promising nanomaterials for anti-counterfeiting applications.