Aggregation-induced fluorescence 'turn on' imaging for fingerprints by an amphiphilic probe: Synthesis and performance

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

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.

Highly efficient ferric ion sensing and high resolution latent fingerprint imaging based on fluorescent silicon quantum dots

Expanding the application of silicon based luminescent materials is a fast-growing interdisciplinary field. Herein, a novel fluorescent bifunctional probe based on silicon quantum dots (SiQDs) for highly sensitive Fe³⁺ sensing and high-resolution latent fingerprint (LFP) imaging was subtly devised. The SiQD solution was mildly prepared using 3-aminopropyl trimethoxysilane as the silicon source and sodium ascorbate as the reductant, showing green emission at 515 nm under UV irradiation with a quantum yield of 19.8%. As a highly sensitive fluorescent sensor, the SiQD was demonstrated to have a highly selective quenching with Fe³⁺ in the concentration range of 2-1000 μM with the LOD of 0.086 μM in water. The quenching rate constant and association constant of the SiQDs-Fe³⁺ complex was calculated to be 1.05 × 10¹² mol/s and 6.8 × 10³ L/mol, respectively, suggesting a static quenching effect between them. Moreover, to achieve high-resolution LFP imaging, a novel SiO₂@SiQDs composite powder was further fabricated. The SiQDs were covalently anchored on the surface of silica nanospheres to conquer aggregation-caused quenching for the high-solid fluorescence. In the demonstration of LFP imaging, this silicon based luminescent composite exhibited high developing sensitivity, high selectivity and high contrast, indicating its practical value as a fingerprint developer at crime scenes.