An oil-in-water nanoemulsion (O/W NE) is selected as the carrier to encapsulate hydrophobic dual-mode luminescent upconversion nanoparticles (UC NPs) and downconversion (DC) carbon quantum dots (CQDs) inside the oil droplets for forming water-based fluorescent inks. The NE inks conform well to the requirements of inkjet printing for anti-counterfeiting encryption applications.