Tunable Dual-Mode MOF-Based Composite Fluorescent Materials: Stimuli-Responsive and Anti-counterfeiting Application

With the incessant improvement of requirements for optical anti-counterfeiting technology, it is essential to develop multifunctional luminescent materials with multiple models and adjustable luminescence. In this article, we reported three new UCNPs@HPU-19b@Ln 3+ (UCNP = up-conversion nanosphere; HPU = Henan Polytechnic University; UCNPs = Y 2 O 3: Er 3+, Yb 3+ @SiO 2 up-conversion nanospheres; HPU-19 = [Cd 4 (L) 2 (H 2 O) 3 ] n, H 4 L = 5,5′-oxydiisophthalic acid) composite materials, which could exhibit red, green, or yellow emission under 254 nm excitation and red emission under 980 nm excitation. Simultaneously, three kinds of fluorescent materials all have sensitive and reversible sensing to HCl gas, which can realize multiple cycles without destroying the structure. The three composite materials solutions as anti-counterfeiting inks were utilized to write and draw some signals and pictures on the papers. On one hand, we could get the specific stored information under different excitations. On the other hand, when treated with acid/base vapor, not only can hidden information be read but also the hidden information reading can be repeatedly realized. Therefore, the dual-mode and reversible luminescence of UCNPs@HPU-19b@Ln 3+ endow them anti-counterfeiting application with high coding ability and high security.