Sensing and sensitive visualization of latent fingerprints on various surfaces using a versatile fluorescent aggregation-induced emission-based coumarin derivative

Aggregation-induced emission luminogens for latent fingerprint detection

For over a century, fingerprints have served as a pivotal tool for identification of individuals owing to their enduring characteristics and easily apparent features, particularly in the realm of criminal investigations. Latent fingerprints (LFPs) are "invisible fingerprints" that are most commonly available at crime scenes and require a rapid, selective, sensitive, and convenient method for detection. However, existing fingerprint development techniques harbour limitations, prompting the exploration of novel approaches that prioritize investigator safety and environmental sustainability. Leveraging the unique photophysical properties of aggregation-induced emission luminogens (AIEgens) has emerged as a promising strategy for on-site analysis of LFP visualization. In this highlight, we have presented a comparative analysis of various AIEgens (organic compounds, metal complexes, nanoparticles, and polymers) for the development and detection of LFPs. Through this examination, insights into the efficiency and potential applications of AIE-based fingerprint development techniques are provided. In addition, several strategies have been proposed for circumventing the limitations of existing AIEgens. We hope that this highlight article will encourage more researchers to investigate AIEgens in LFP detection, contributing to forensic science.

3-Aroylbenzocoumarin-Based Luminogens: Bright Solid-State Emission, AIE Properties and Cell Imaging Application

A series of 3-aroylbenzocoumarin-based luminogens have been synthesized for investigating their aggregation-induced emission (AIE) and solid-state fluorescence. The single crystal X-ray diffraction analysis of one of them showed that the molecules are arranged in the form of π-dimers which may lead to excimer emission. The large Stokes shifts and the broad-band emission of these 3-aroylbenzocoumarins in solid/aggregation state demonstrated the probable formation of excimers. The shapes of benzocoumarin units have a great effect on the AIE behaviors. The linear benzocoumarin derivatives show larger Stokes shifts, while the bent-benzocoumarin derivatives exhibit better AIE performances. All of them show aggregation-enhanced excimer emission which is supported by the large Stokes shifts. The electronic effect of 3-aroyl groups also has a certain effect on their fluorescence properties. The polymorphism phenomenon was observed for one of the benzoyl-containing derivatives. Additionally, two of the derivatives containing methoxy group were successfully used for cell imaging.

Hypoxia-responsive AIEgens for precise disease theranostics

Specific biomarker-activatable probes have revolutionized theranostics, being beneficial for precision medicine. Hypoxia is a critical pathological characteristic prevalent in numerous major diseases such as cancers, cardiovascular disorders, inflammatory diseases, and acute ischemia. Aggregation-induced emission luminogens (AIEgens) have emerged as a promising tool to tackle the biomedical issues. Of particular significance are the hypoxia-responsive AIEgens, representing a kind of crucial probe capable of delicately sensing and responding to the hypoxic microenvironment, thereby enhancing the precision of disease diagnosis and treatment. In this review, we summarize the recent advances of hypoxia-responsive AIEgens for varied biomedical applications. The hypoxia-responsive structures based on AIEgens, such as azobenzene, nitrobenzene, and N-oxide are presented, which are in response to the reduction property to bring about significant alternations in response spectra and/or fluorescence intensity. The bioapplications including imaging and therapy of tumor and ischemia diseases are discussed. Moreover, the review sheds light on the future challenges and prospects in this field. This review aims to provide comprehensive guidance and understanding into the development of activatable bioprobes, especially the hypoxia-responsive AIEgens for improving the diagnosis and therapy outcome of related diseases.

Cross-Linking Induced Emission of Polymer Micelles for High-Contrast Visualization Level 3 Details of Latent Fingerprints

Rationally developing an intelligent tool for high-contrast fluorescence imaging of latent fingerprints (LFPs) is gaining much concern in many applications such as medical diagnostics and forensic investigations. Herein, the off-on fluorescent polymer micelles (PMs) have been rationally designed and synthesized for high-contrast fluorescence imaging of LFPs through the cross-linking reaction of hydrazine (N₂H₄) and aldehyde group of polymer. Excitingly, the cross-linking (N₂H₄) induced emission of PMs has the property of aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT), which could effectively address the notorious aggregation-caused quenching (ACQ) effects of conventional organic dyes. In addition, the cross-linking strategy can not only improve structural stability of PMs but also enhance its fluorescence brightness. The experiment results demonstrated that PMs showed high water dispersibility (100% aqueous solution), high selectivity, large Stokes shift (∼150 nm), good photostability, and excellent long-term stability. Because of the hydrophobic interaction between the PMs and fingerprint components, the PMs preferentially adhered onto the ridges of fingerprint, and then cross-linking (N₂H₄) induced emission properties endowed the PMs for high-contrast imaging of LFPs in different substrates, especially the levels 1-3 details of LFPs. We expect that this strategy will provide vital support for LFPs technology.

Novel Organic-Inorganic Hybrid Polystyrene Nanoparticles with Trichromatic Luminescence for the Detection of Latent Fingerprints

This article explored the application of novel organic-inorganic hybrid polystyrene nanoparticles (PSNPs) with trichromatic luminescence for the detection of latent fingerprints. The PSNPs were synthesized by encapsulated Eu(DBM)₃phen, coumarin 6, and FDBT into the polystyrene nanoparticles through the swelling method and applied them to visualize latent fingerprints. The PSNPs had a spherical morphology with an average diameter of 310.7 nm, and they emitted trichromatic fluorescence (525 nm/570 nm/610 nm) under 365 nm excitation wavelength with green/yellow/red color under filters. They were less likely to aggregate, float or stain the background when treating fingerprints. The developed fingerprints with excellent clarity of ridges and contrast could be viewed, and the digital magnification of fluorescence-developed fingerprints provided more minutiae details about some regional patterns. The colorimetric and fluorescent trichromatic light could provide complementary signals without the background interference from fluorescent substrates and/or complex multicolor surfaces, which improved the applicability of fluorescent nanoparticles for fingerprints development. PSNPs are promising for the detection of latent fingerprints and practical criminal investigations with their ease of operation, eco-friendly properties, and excellent trichromatic optical performance.

A fluorescent molecular rotor for the in situ imaging of latent fingerprints

We developed a fluorescent molecular rotor that responds to hydrophobic and viscous environments and visualizes latent fingerprints with level 3 details.

An AIRE-active far-red ratiometric fluorescent chemosensor for specifically sensing Zn2+ and resultant Zn2+ complex for subsequent pyrophosphate detection in almost pure aqueous media

A simple Schiff-base fluorescent chemosensor (1) was synthesized by the reaction of 3-amino-pyrazine-2-carbohydrazide and 7-diethylamino-3-formylcoumarin; the sensor 1 displayed a notable green emission at 524 nm in DMSO and an aggregation-induced ratiometric emission (AIRE) at 555 nm in an almost buffered aqueous media (0.5% DMSO content). The AIRE of 1 was quenched following binding to Zn²⁺ ions, while the fluorescence emission in the far-red region was evidently enhanced at 628 nm. Notably, the ratiometric signal output could be utilized to specifically distinguish Zn²⁺ among various metal ions. Moreover, the 1-Zn²⁺ complex was effectively employed as a fluorescent ratiometric chemosensor for pyrophosphate (PPi) detection. The detection limit was 3.52 μM and 2.45 μM for Zn²⁺ and PPi, respectively. The binding mechanism was evaluated by ¹H NMR, ESI-MS, single-crystal X-ray diffraction, TEM, time-resolved fluorescence spectrophotometry, and density functional theory studies. Overall, owing to its sensitive fluorescence behavior, cell imaging studies demonstrated that this sensor is capable of sensing Zn²⁺ and PPi in living cells.