Low-temperature photoluminescence quenching properties of Tin(II)-doped zinc metal halides: Implications for anti-counterfeiting labels

In this work, we report the synthesis and optical characterization of a divalent tin (Sn 2+ )-doped organic-inorganic zinc (Zn 2+ )-based compound, (DFPD) 2 ZnCl 4 ·H 2 O (DFPD + = 4,4-difluoropiperidinium), which exhibits notable PL quenching at relatively low temperatures. At room temperature, it emits stable green light with a high PL quantum yield of 97 %. Upon heating above 340 K, dehydration induces a structural transformation, resulting in an irreversible, stepwise quenching of its luminescence. Unlike most reported thermochromic materials, which generally require high PL quenching temperatures (>400 K), the relatively low deactivation temperature of (DFPD) 2 ZnCl 4 ·H 2 O:Sn 2+ makes it particularly suitable for enhancing the security of adhesive anti-counterfeiting labels.