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

The substituent effect of quaternary protoberberine alkaloid (QPA) based natural products was systemically analyzed and further applied in latent fingerprints. [Display omitted] •The relationship between substitution and electron effect for QPA was described.•AIE behaviors of natural products (BBC, FBC, CTC, and EBC) were systemically studied.•CTC and EBC having dioxolo-substituted isoquinolinium show low reorganization energy.•BBC nanoaggregates detect TNP with 9.8 nM of LOD.•Natural BBC/MMT powders visualized three levels of detail for LFP imaging. Real-time and in-situ fluorescence visualization technologies have attention to in the forensic analysis of latent fingerprints (LFPs). The fingerprint powders with high performance and biocompatibility are essential for imaging LFPs with high definition and safety. In this work, five quaternary protoberberine alkaloid (QPA) derivatives were analyzed with reorganization energy and four-point calculations to explain the relationship between the substituent effect and luminescent properties and further resolve the luminous behaviors of four QPA-based natural products in solution. Thanks to the restriction of the intramolecular motions mechanism, aggregation-induced emission (AIE) active BBC nanoaggregates could sensitively detect explosive analog, 2,4,6-trinitrophenol, at a nanomolar level (9.8 nM of detection limit). Combined with natural montmorillonite (MMT) mineral powders, three levels of details for fingerprints were successfully imaged with solid-luminous BBC/MMT nanocomposites. The insight into the substituted effect of alkoxy groups on the QPA framework not only provides a new concept to design rotor-free AIE luminogens but also expands natural products and their nanocomposites into LFP and detection applications.