Multi-key optical anti-counterfeiting and information storage based on multi-mode excitation-emission of upconversion nanocrystals and metal chlorides

Anti-counterfeiting has become a crucial global issue. Traditional anti-counterfeiting technology is easy to be imitated because of its low security, so it is urgent to develop an optical information encryption strategy with higher security level. In this study, a multi-key optical anti-counterfeiting and information storage strategy based on upconversion nanocrystals (UCNPs) and metal chlorides under multi-mode excitation-emission is proposed. Based on the optical properties of four orange luminescent materials (OLM), the distinguishable excitation mode (UV, NIR) and good afterglow characteristics are used to encrypt, decrypt and store real information. Finally, based on this characteristic, we propose an information encryption strategy for binary digit-ASCII encoding and digital information display. Under the irradiation of 254 nm excitation light, the real information is hidden, the “excitation wavelength key” and “capture time key” are used to read the correct information. This multi-key anti-counterfeiting strategy hides real information by interfering with information, which greatly improves the security level of anti-counterfeiting and is very promising in anti-counterfeiting applications.