Latent Fingerprints Research Articles

Supramolecular Sequential Light-Harvesting Systems for Constructing White LED Device and Latent Fingerprint Imaging.

The fabrication of supramolecular light-harvesting systems (LHS) with sequential energy transfer is of significance in utilizing light energy. In this study, we report the non-covalent self-assembly of a sequential LHS by pillar[5]arene-based host-guest interaction in water and its applications in white light-emitting diode (LED) device and latent fingerprint imaging. The host-guest complex WP5 G self-assembles into nanoparticles in water and shows enhanced aggregation-induced emission (AIE) effect. The nanoparticles can be further used to construct sequential LHS with fluorescent dyes 4,7-di(2-thienyl)-benzo[2,1,3]thiadiazole (DBT) and sulforhodamine 101 (SR101). Impressively, the system shows white-light emission when the molar ratio of WP5 G/DBT/SR101 is 1100/2/16. The material can be coated on a LED bulb to achieve white-light emission. In addition, the sequential LHS exhibit multicolor fluorescence including red emission, which have been successfully applied to high-resolution imaging of latent fingerprints. Therefore, we demonstrated a general strategy for the construction of sequential LHS in water based on macrocyclic host-guest interaction and explored its multi-functional applications in white-light LED device and imaging of latent fingerprints, which will promote future development and application of supramolecular LHSs.

End-to-end latent fingerprint enhancement using multi-scale Generative Adversarial Network

Latent fingerprint enhancement is paramount as it dramatically influences matching accuracy. This process is often challenging due to varying structured noise and background patterns. The prints may be of arbitrary sizes and scales with a high degree of occlusion. There is a need for creating an end-to-end system that handles different conditions reliably to streamline this often lengthy and tricky process. In this work, we propose a Generative Adversarial Network (GAN) based architecture that effectively captures multi-scale context using Atrous Spatial Pyramid Pooling (ASPP). We have trained the network on a synthetically generated dataset, carefully designed to represent real-world latent prints. By avoiding the reconstruction of spurious ridges and only enhancing valid ridges, we avoid the generation of false minutiae, leading to better matching performance. We obtained state-of-the-art results in Sensor to Latent matching using the IIITD MOLF and Latent to Latent Matching using IIITD Latent datasets.

Mn2+-activated NaYF4:Yb, Er red-emitting nanophosphors for accurate latent fingerprint identification by an Artificial Intelligence program

The development and comparison of Latent Fingerprint Patterns (LFPs) constitute critical components of research in fingerprint detection and identification. However, the development of nanomaterials visualization and digital algorithms for LFPs analysis are mostly studied independently, resulting in inaccurate LFPs. This research synthesized a series of efficient red-emitting NaYF4:20 %Yb, 2 %Er, x%Mn (x = 0, 5, 10, 15, 20, 25, 30, 35, and 40) upconversion nanoparticles (UCNPs) for image development, which were combined with a digital algorithm for accurate LFP recognition. The eightfold increase in luminescence intensity of NaYF4:Yb, Er, 30 %Mn at 653 nm effectively avoids interference from biological tissue fluorescence. This improvement is credited to the efficient reverse energy transfer mechanism between Er3+ and Mn2+ ions, specifically the transition sequence 4S3/2(Er3+) → 4T1(Mn2+) → 4F9/2(Er3+). Furthermore, a MATLAB program was employed to process the fluorescent images of LFPs developed using the UCNPs nanophosphors, achieving a high matching score of 90.09 % for the optimized sample, significantly outperforming traditional benchmarks. These results demonstrate the superior effectiveness of the NaYF4:Yb, Er, 30 %Mn nanophosphor, combined with digital processing algorithms, for practical LFP recognition applications.

Enhanced fluorescence imaging of level 1–3 latent fingerprints on multi-materials through lipophilicity-tunable probes

Latent fingerprints (LFPs) are crucial for personal information security and forensic medicine. In recent years, there has been a lot of attention on fluorescence probes for LFP imaging, but the effect of lipophilicity on LFP's imaging performance has not been fully explored. Herein, three naphthalimide-based AIE probes (TPA-NA-Pr, TPA-NA-OH, TPA-COOH) with different lipophilicity were designed and analyzed. After optimizations, TPA-NA-Pr and TPA-NA-OH were found to be able to visualize LFPs within 2 seconds under 405 nm LED lamp excitation. By immersing materials with the probe solution or spraying the probe solution on different material surfaces, a series of high-quality LFP images could be quickly developed. Even LFP level 3 details (such as sweat pores) could be directly observed with naked eyes. The probe solution stored for 2 months did not precipitate or deteriorate, but still can be used for accurate LFP imaging on different substrates with high-resolution level 1–3 details. This study provides insights into the role of lipophilicity on LFP probes and furnishes two LFP probes with extended lifespan and reduced costs for their real-life applications in personal identification and criminal investigation scenarios.

Electrochemical visualization of latent fingerprints using polyphenazine dyes on brass cartridges

This work is focused on the visualization of latent fingerprints left on unfired brass cartridges. Polymer films were prepared from 2 mM neutral red or 5 mM toluidine blue using two different electrochemical methods (cyclic voltammetry or chronoamperometry) with relatively short polymerization times. The conditions for the deposition of conductive polymers, poly(neutral red) and poly(toluidine blue), from a neutral medium (phosphate buffer with 0.1 M KNO3 or 0.1 M KNO3, respectively) were optimized to produce high-quality visualization of the remaining fingerprints on the brass substrates. The surface morphology and quality of the polymer films after the electrochemical deposition of both polyphenazine dyes were characterized by stereomicroscope. Phenazine dyes, which were used for the visualization of fingerprints, have been shown to provide different degrees of homogeneity in the deposited film. Furthermore, the dependence of the stability of the monomer solutions on their age, use, and storage conditions are discussed. Finally, a methodology is proposed for how to apply this technique of visualizing latent fingerprints with observed details of papillary lines in forensic practice.Graphical abstract

AI-authenticated latent fingerprint developed using ultra-bright nitrogen-doped carbon dots-intercalated Zn(OH)2 nanosheets

AI-authenticated latent fingerprint developed using ultra-bright nitrogen-doped carbon dots-intercalated Zn(OH)2 nanosheets

Study on four pyridine-based difluoroboron compounds for mechanofluorochromic behaviors, the ink-free writing and detection of latent fingerprints

With the increasing demand for multifunctional aggregation-induced emission materials, four pyridine-based difluoroboron compounds (1, 2, 3, and 4) with the anthryl unit as an electron donor and difluoroboron moiety as the electron acceptor were designed and successfully synthesized. It found that four compounds displayed significantly intramolecular charge transfer characteristics and solvatochromism phenomena. The other compounds possessed mechanofluorochromic behaviors under external mechanical stimulation except compound 1, owing to its lesser change value of the dipole moment between the ground and excited states. More importantly, they exhibited potential application in the field of ink-free writing due to reversible mechanochromism during the grinding and fumigation process. Additionally, four compounds were used for detection of latent fingerprints on the glass surface due to their excellent aggregation effects in the THF/water mixtures. This research provides a reference for exploring multifunctional aggregation-induced emission difluoroboron compounds with brightness luminescence.

Luminescent carbon dots encapsulating in Eu3+ doped gahnite spinel nanocomposite for boosting thermal sensing, advanced level III detection and intelligent anti-counterfeiting applications

The exceptional optical properties of carbon dots (CDs) position them as a highly promising category of multifunctional carbon-based nanomaterials. When hydrothermally prepared CDs are incorporated into europium-doped zinc aluminate ZnAl2O4 nanophosphors (ZAO:Eu3+ NPs) synthesized via ultrasonication method, the resulting CDs@ZAO:Eu3+ nanocomposite (NCs) exhibits a broad excitation band, with a prominent peak at approximately 393 nm, perfectly matching the emission wavelength range (500–750 nm) of near-ultraviolet (n-UV) LED chips. Significantly, the CDs (5 wt %)@ZAO:Eu3+ NCs exhibit a remarkable 12.5 folds enhancement in photoluminescence (PL) intensity compared to ZAO:Eu3+ alone, thanks to the Förster Resonance Energy Transfer (FRET) between CDs and Eu3+ ions. This enhancement in luminescence could stem from the CDs capturing electrons and facilitating energy transfer to the luminescent Eu3+ ions. Utilizing CDs to enhance fluorescence presents a straightforward and eco-friendly approach for boosting luminescence properties. Impressively, even under elevated temperatures reaching 420 K, the thermal stability of CDs (5 wt %)@ZAO:Eu3+ NCs remains outstanding, retaining 90 % of its initial luminescence intensity. This highlights its exceptional thermal stability, characterized by a high activation energy of 0.27 eV. With an impressive internal quantum efficiency (IQE) of 87.01 %, the optimized composite also achieves remarkable colour purity (CP), reaching 99.5 %. The relative sensitivity was 1.36 %, at 300 K. Thus, CDs@ZAO:Eu3+ is a promising material for non-contact optical thermometry applications. Utilizing the optimized NCs through a simple powder dusting technique effectively develops latent fingerprints (LFPs) on various surfaces, revealing fingerprints (FPs) under 365 nm UV light. Additionally, the study investigates diverse pore parameters including number, position, size, shape, and inter-spacing. Furthermore, optimized NCs are utilized to create a transparent anti-counterfeiting (AC) ink, offering effective AC features through its red emission under 365 nm UV light.

Dual-mode excitable Vis/NIR-II luminescence of lanthanide-doped core@multishell nanostructures for anti-counterfeiting and imaging of latent fingerprints

The development of luminescent materials that can simultaneously realize multiple emissions can help improve the reliability of anti-counterfeiting and the security of encrypted information. Lanthanide-doped nanomaterials are very suitable for advanced anti-counterfeiting applications because of their abundant 4 f energy levels and near-infrared (NIR) laser excitability. Herein, we design lanthanide-doped core@multishell nanoparticles NaYF4:Yb,Er/Ho/Tm@NaYF4@NaYF4:Nd@NaYF4, which can realize upconversion luminescence of Er/Ho/Tm under 980 nm excitation, as well as non-overlapping NIR-II luminescence under 980 nm or 808 nm excitation. By precisely controlling the distribution of lanthanide ions in the core-shell layer, the luminescence interference of nanomaterials under different wavelength excitation can be avoided. Experiments show that multi-color security and information encryption under NIR laser excitation can be achieved using aqueous inks containing the designed multilayered core-shell nanostructures, which are covert and difficult to forge. And the multilayer core-shell nanopowder can be used for efficient identification of latent fingerprints on complex surfaces.

Investigating the influence of carbon dots on β-Ca2SiO4:Ce3+ phosphors derived from agro-waste for diverse applications

A series of blue-emitting composite based on 3 wt% carbon dots in β-Ca2SiO4:Ce3+ (3 wt% CDs@β-CSO:Ce3+) was synthesized through a hydrothermal method, aiming to enhance applications in latent fingerprint (LFP) detection, anti-counterfeiting (AC) measures, and optical thermometry. The X-ray diffraction (XRD) analysis confirmed that these phosphors possess a monoclinic crystal structure. Under 356 nm excitation, the Ce3+ doped β-Ca2SiO4 phosphors (β-CSO:Ce3+) display a broad blue emission peak at 431 nm, attributed to the 5d → 4f electric dipole transition of Ce3+, while the inclusion of Carbon dots (CDs) shifts this emission to 442 nm. This shift and the improved photoluminescence (PL) intensity are thought to result from the Fӧrster Resonance Energy Transfer (FRET) mechanism. The optimal concentration of Ce3+ ions was determined to be 5 mol%, as higher concentrations led to a decrease in emission intensity due to concentration quenching (CQ). Additionally, a fabricated white light diode using these phosphors achieved chromaticity coordinates of (0.344, 0.330) according to the Commission International de L'Eclairage (CIE), with the CIE, correlated colour temperature (CCT), and colour purity (CP) metrics indicating a bright green output with values of (0.1486, 0.0433), 1759 K, and 96.4%, respectively. The optimized 3 wt% CDs@β-CSO:5Ce3+ composite demonstrated a remarkable CP of 99.9%. Notably, the phosphors maintained 85.77% of their emission intensity at 423 K, showcasing exceptional thermal stability. A novel approach utilizing sketch pen and brush mode was developed to apply the optimized AC security ink, allowing for the creation of various intricate patterns. The resulting AC tags featured high resolution and durability. These findings underscore the 3wt%CDs@β-CSO:5Ce3+ composite as superior luminescent materials for use in fields requiring LFP, AC strategies, and optical thermometry.

Mechanofluorochromic behaviors and latent fingerprint detection of triphenylamine-based compounds with mono-/bis-BF2 fluorophores

To better understand the relationship between molecular structure of the mono-/bis-BF2-core compounds and mechanofluoroboron behaviors, two pyridine-based difluoroboron compounds with triphenylamine group (TPA-ts-BF2 and TPA-ts-2BF2) were designed and successfully synthesized, which TPA-ts-BF2 including a BF2 fluorophore and TPA-ts-2BF2 containing the bisBF2 fluorophores. Based on the photophysical properties measurements results, it was found that TPA-ts-2BF2 had more excellent intramolecular charge transfer characteristics than that of TPA-ts-BF2, and exhibited significant aggregation-induced emission activity, however, TPA-ts-BF2 displayed typical aggregation-caused quenching phenomenon. Meanwhile, the emission spectrum of the solid powders of TPA-ts-2BF2 was red-shifted 52 nm after grinding, that of TPA-ts-BF2 was red-shifted 46 nm, which was resulted from crystalline state switching to amorphous state. According to the theoretical calculations, we conjectured that TPA-ts-BF2 with uncoordinated amide linkage moiety had a tendency to forming a more twisted conformance and higher molecular polarity, which made that mechanofluorochromic behavior was worse than that of TPA-ts-2BF2. Additionally, TPA-ts-2BF2 was applied to latent fingerprint detection due to its prime aggregation-induced emission property.

Recent Progress of Advanced AIE Materials for Visualization of 3‐Level Latent Fingerprints

The 3‐level features of Latent fingerprints (LFPs) are pivotal in linking suspects with problematic or incomplete fingerprint data, constituting one of the most robust forms of evidence. Aggregation‐induced emission (AIE) materials, known for their heightened emissive properties in high aggregation states, provide a robust and powerful approach for developing techniques for 3‐level details of LFPs. So far, tremendous efforts have been devoted to solving high background fluorescence interference during the 3‐level LFPs visualization process. This review commences with an overview of 3‐level features and summarizes the interaction and mechanism of visualizing LFPs involving AIE materials and LFPs secretions. Moreover, it encompasses strategies to enhance the contrast and brightness of 3‐level LFPs images. We highlight the mechanism of AIE's physicochemical properties and their effects on the visualization of 3‐level LFPs. Additionally, we provide insights into potential challenges and opportunities in this emerging field.

Exploring sustainable forensics: silica nanoparticle powder derived from rice husk waste for aged fingermark development and the chemistry of surface interactions

BackgroundPowder-based fingermark ridge visibility enhancement is a common technique employed in crime scenes due to ease of application and robustness of the application method. Pigmented powders created a contrast between the surfaces and developed ridgelines and are generally metals or metal oxides based. Previous research showed the successful development of fresh latent fingermarks using rice husk-derived silica nanoparticles on various surfaces. Nevertheless, there has been less previous evidence for the efficiency of the silica nanoparticle powder on aged fingermark development. Therefore, the aim here is to investigate the efficacy of the powder on aged fingermarks relative to commercial formulation to gauge the feasibility of having naturally derived powder as a possible alternative for field application and commercialisation.ResultsRigorous testing over a range of non- and semi-porous surfaces at varied ageing conditions revealed a minimal disparity in the performance of both powders on most surfaces. Still, silica nanoparticles exhibited superiority in terms of selectivity on silica-based surfaces. Close up analysis of developed fingermarks using electron microscope exposed clear demarcation between fingermark ridges and valleys using silica nanoparticles.ConclusionsFindings revealed that the interaction chemistry between powder particles and surface material either enhances or lowers the fingermark development capacity depending on the type of surface tested.

Enhancement imaging of developed latent blood fingerprints using TOF-SIMS

As one of the most common types of evidence in violent cases, blood fingerprints play an important role in identifying suspects. Typically, Latent blood fingerprints from a crime scene require the application of chemical development reagents followed by photographing to visualize the ridge detail. However, conventional development techniques are not effective in the visualization of poor latent blood fingerprints due to the formation conditions. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a surface analysis technique that combines high mass resolution and high spatial resolution to recover through mass spectrometry imaging (MSI) to reveal fingerprints that are invisible to the naked eye, especially conventional visualization methods. In this study, an enhancement method for latent blood fingerprints was established by analyzing blood fingerprints that showed poor visibility using conventional methods (acid yellow, amido black 10B, tetramethylbenzidine) on plastic sheets, aluminum foil, various papers, and other objects. Additionally, blood samples were diluted with distilled water at concentration gradients of 1:5, 1:10, 1:20, and 1:100 to test the method's sensitivity. Latent fingerprints of blood that aged 14, 30, and 54 days were also examined. Results showed that this method not only enhances the development of fingerprints under challenging conditions but also allows for the recovery of incomplete fingerprints and the separation of overlapping fingerprints. Compared to conventional methods, this approach significantly improves the development effect of latent blood fingerprints while maintaining universality, reliability and practicality.

Meticulously designed red emission carbon dots as efficient and stable luminescent species for rapid latent fingerprint recognition and light emitting diodes

The preparation of carbon dots (CDs) emitting long wavelength has attracted more attentions due to their unique advantages in biological and optoelectronic fields, including the wide absorption, long PL lifetime and deep-tissue penetration. Herein, we prepare the nitrogen and sulfur co-doped red emission carbon dots (R-CDs) from the 2,4-diaminodiphenylamine (DDA) and thiourea via a solvothermal reaction, which exhibit reliable red emission at 613 nm and possess a high quantum yield (QY) of 34 %. Meanwhile, the structural analysis and theoretical calculation reveal that the sulfur doping from thiourea increases the nitrogen and oxygen content of CDs, leading to the red emission observed in R-CDs. Subsequently, we design an integrated fingerprints recognition system based on the R-CDs phosphors for the imaging of latent fingerprints (LFPs) and fast LFPs recognition, expanding the application of biometric identification and comparison technology based on fluorescence. Finally, we successfully apply the R-CDs into red and white light-emitting diodes, improving plant growth efficiency. As a result, this work provides a new in-depth insight of red emission CDs and expands the application in latent fingerprint recognition and light-emitting diodes.

Latent fingerprint visualization with the novel white fluorescent fingerprint powders

Based on carbazole derivatives, a new fluorescent dye G-D was constructed. White fluorescent fingerprint powder was constructed by proportionally blending montmorillonite with G-D and the previously synthesized dyes (B-D and R-D). White fluorescent fingerprint powder is obvious in the dark and can be subjected to minimal fluorescent background interference. The white fluorescent fingerprint powder was successfully used to develop latent fingerprints left on various surfaces, including glass, tin foil, marble, acrylic plate with bright fluorescence, painted wood and coins. Impressively, the white fluorescent fingerprint powder also has excellent applications in developing aged fingerprints and replication. For complex criminal investigation activities, the white fingerprint powder with high resolution, wide applicability and real-time development is a competitive visualization means.

The effectiveness of natural indigo/kaolinite composite powder in the development of latent fingermarks

BackgroundComposites are materials that have multiple phases and have attracted much attention as they are able to improve physical and chemical properties of an isolated material. In this sense, these composites are commonly used as key components for two purposes: coloring and improving the operational properties; besides that, they have alternative synthesis routes that respect the principles of green chemistry. Thus, this reports the development of a new composite using natural products, indigo and kaolinite, for application in papilloscopy as a new nontoxic fingermark developer.ResultsThe composite was obtained via green procedures and was characterized by spectroscopic and chromatographic techniques. Thus, to investigate the potential of the material as a fingermark developer, different techniques were applied such as depletion, aging, comparison with commercial powder, and development of latent fingermarks on different surfaces. Tests revealed that the composite presented good contrast and adhesion with the latent fingermarks, even after 15 days of deposition.ConclusionsThis study presents a natural indigo/kaolinite composite powder that showed similar or higher efficiency when compared to the commercial fingerprint powder and was able to develop identifiable natural and sebaceous fingermarks.Key points• A composite was formed from eco-friendly materials.• The composite formation follows the concepts of green chemistry and low cost.•The composite was applied as a latent fingermark developer.

Non-destructive and simultaneous development and enhancement of latent fingerprints on stainless steel based on the electrochromic effect of electrodeposited manganese oxides

Latent fingerprints, as one of the most frequently encountered traces in crime scene investigation and also one of the largest sources of forensic evidence, can play a critical role in determining the identity of a person who may be involved in a crime. Due to the invisible characteristic of latent fingerprints, exploring efficient techniques to visualize them (especially the ones resided on metallic surfaces) while retain the biological and chemical information (e.g., touch DNA) has become a multidisciplinary research focus. Herein we reported a new and highly sensitive electrochemical interfacial strategy of simultaneously developing and enhancing latent fingerprints on stainless steel based on synchronous electrodeposition and electrochromism of manganese oxides in a neutral aqueous electrolyte. By utilizing a specially designed device for electrochemical testing and image capture, a series of electrochemical measurements, physical characterization and image analysis have been applied to evaluate the feasibility, development accuracy and enhancement efficacy of the proposed electrochemical system. The qualitative and quantitative analysis on the in situ and ex situ fingerprint images indicates that the three levels of fingerprint features can be precisely developed and effectively enhanced. Forensic DNA typing has also been performed to reveal actual impact of the proposed electrochemical system on subsequent analysis of touch DNA in fingerprint residues. The ratio of detected loci after electrochemical treatment reaches up to 98.5 %, showing non-destructive nature of this fingerprint development and enhancement technique.

Multimodal responsive Dy3+, Li+ activated Gd2MgTiO6 phosphors for ideal wLED, potent anti-counterfeiting, fingerprint visualization, and encryption coding

The Gd2MgTiO6 is an infant luminescence host that portrays eclectic applications in displays, security devices, and forensic studies. The perovskites are synthesized by facile combustion method, decreasing the synthesis conditions from 1573 K, 5 h to 1173 K, 4 h, from conventional routes. The phosphors are then activated with Dy3+ ions, giving photoluminescence emission in the blue, yellow, and red regions of the visible spectrum owing to (4F9/2 → 6H15/2), (4F9/2 → 6H13/2), and (4F9/2 → 6H11/2) transitions respectively. Further, monovalent Li+, divalent Sr2+, or trivalent Sm3+ ions are co-doped in the crystal matrix, which chiefly enhances the optical and crystalline properties for Li+ sensitization. Under 351 nm excitation, these samples show CIE coordinates (0.3290, 0.3313), color temperature 5759 K, color rendering index 86, and color purity of 2.5 %; signifying ideal white light emission for wLED with quantum efficiency 43 %. Under 980 nm excitation, these phosphors gave noble red emission, which can be effectually applied as a level 3 latent fingerprint visualization tool in criminology. The white and red emissions on UV and NIR excitation respectively are combined for potent anti-counterfeiting security ink and encryption coding; which marked a new methodology for the multifunctional application of a single phosphor matrix.

Synthesis and Spectroscopic Characterization of Novel Fluorescent quinolinyl hydrazone for Latent Fingerprint and Anticounterfeiting Applications

Synthesis and Spectroscopic Characterization of Novel Fluorescent quinolinyl hydrazone for Latent Fingerprint and Anticounterfeiting Applications