Natural protoberberine alkaloid–montmorillonite nanocomposite powders with AIE features for visualizing high-resolution latent fingerprints

In this contribution, we propose natural resources as a new source to acquire biocompatible AIEgens.

A water-soluble probe, TPA-1OH, with aggregation-induced emission activity is synthesized and used for expedient real-time fluorescence in situ visualization of latent fingerprints (LFPs). A TPA-1OH aqueous solution exhibits nonfluorescence in pure water while strong fluorescence upon molecular aggregation induced by addition of poor solvent. Fluorescence images of LFPs on a variety of substrates, including rough surfaces such as walls, bricks, and paper, are developed under 405 nm light, by soaking in or spraying with a TPA-1OH aqueous solution (30 μM) without any necessity of organic cosolvents and post-treatment steps. The probe is noncytotoxic at a concentration lower than 50 μM. The development process of LFPs is demonstrated by real-time fluorescence in situ imaging. The exponential relationship between the relative fluorescence intensity and time is deduced from the fitting curve. The LFP images developed by TPA-1OH are evident and intact enough to allow that the level 1-3 details are displayed and analyzed. Noteworthily, the level 3 details of LFPs such as the fingerprint ridge width and the characteristics of the sweat pores are evidently visible under fluorescence microscopy. Even the nanoscopic details exceeding level 3 are visualized under super-resolution microscopy with sub-50 nm optical resolution.