Aggregation-Induced Emission sensors based on sulfide-containing naphthalimides for imaging latent fingerprints

Abstract

Aggregation-induced emission luminogens have attracted extensive attention due to their wide applications. In this work, two naphthalimide derivatives (NIS1 and NIS2) were designed and synthesized which could be used as the solid imaging agents for their AIE effects. In both molecules, V-shape structures were introduced to construct de-planar conjugated systems using O and N atoms as the centers. The center atoms tune the emissions of these molecules in deep blue (411∼436 nm, NIS1) and yellow-green (521∼540 nm, NIS2) regions in organic solvents with different polarity. NIS1 and NIS2 exhibit AIE-active fluorescence in their aqueous solutions (545 nm for NIS1 and 600 nm for NIS2). Further studies on their photophysical properties indicate that the introduction of methylmercapto group (-SCH3) can enhance the AIE intensities compared to their mimic. DFT calculation was performed to explore the different transitions occurred in these compounds. At last, NIS1 and NIS2 were successfully fabricated as the solid imaging agents and applied to the latent fingerprints imaging on varied substances. A highlight in this work is these imaging agents can work well on the scene with high background fluorescence by optimizing the excitation wavelength and selecting suitable emission channel.