Vermiculite-derived cationic molecular-intercalated fluorescent MgAl-LDHs for assembling ultrathin solid-state light-emitting films

Solid-state light-emitting devices are of special interest in optoelectronic applications, owing to inherent advantages in terms of low cost, high efficiency and desirable durability. However, the accumulation of solid fluorescent chromophores causes serious energy transfer, resulting in fluorescence quenching. Herein, exfoliated vermiculite (VMT) was structurally disassembled into Mg-O octahedral and Si-O tetrahedral layers to produce hydrotalcite (LDHs) and SiO2, respectively, realizing efficient utilization of each component and VMT surface. The fluorescent intercalated LDHs was intercalated with organic fluorescent dyes, including rhodamine 6G (R6G), pyronine G (PG) and sodium fluorescein (Fl-Na), to prepare high-performance fluorescent LDHs, which was further assembled with VMT nanosheets to form ultrathin solid-state light-emitting films. Based on the electrostatic self-assembly strategy, the localization of chromophores and light-emitting intensity of solid films can be precisely controlled by adjusting ordered multilayers. In fact, the exfoliated VMT could cause the quenching of organic fluorescent dyes in liquid, therefore VMT can be used as fluorescent quencher, which could be regenerated by heating. The designed assembly strategy avoids the fluorescence quenching of VMT. Without the addition of any surfactant, both anionic and cationic organic fluorescent dye can be intercalated into hydrotalcite, overcoming the disadvantage of LDHs that can only intercalate anionic molecules. In particular, the VMT encapsulation overcomes the quenching problem of fluorescent dye and improves the stability of the light-emitting films. This work provides a potential strategy for assembling solid-state light-emitting films and opens new applications in various optoelectronics, such as surface-emitting light source and full-color flat-panel displays.