A single-beam NIR laser-triggered full-color upconversion tuning of a Er/Tm:CsYbF@glass photothermal nanocomposite for optical security.

The development of advanced luminescent materials is highly desirable for addressing the rising threat of forgery. However, it is challenging to achieve stable full-color upconversion (UC) tuning in the same matrix upon a single-beam light excitation so as to ensure that authentic items are irreproducible. Herein, hexagonal Er/Tm:CsYbF nanocrystals (NCs) embedded inorganic glass an crystallization strategy is fabricated, which can emit blue, cyan, green, yellow, orange, red and near-infrared (NIR) UC emissions by simply modifying an incident 980 nm laser power.