Latent Fingerprints Research Articles

Multimodal Biometric System Fusion Using Fingerprint and Iris with Convolutional Neural Network

Biometric sensing technology became everyday life frequent component as a result of world requirement for info security and safety legislation. A strong and efficient individual authentication has appeared because of new developments in multimodal biometrics. Multimodal biometrics integrates different biological traits in trying for creating considerable effect on identification performance. Latent fingerprint biometrics refer to effective human identification system for criminals given the accessible crime evidence shreds. Although, biometric trait restrictions like intra-class variation, sensed data noise, lack of individuality caused low matching score that possesses a negative effect on recognition and investigation process. This paper uses two unimodal biometrics—the fingerprint and the iris—applied as multi-biometrics to show that using these biometrics can produce excellent results with high accuracy. Every biometric result is weighted for involvement in the final decision, and the decision level is utilized for fusion. For every biometric result integration effect, a neural network is used. The datasets' experimental findings have demonstrated a notable biometric system identification capability. The accuracy performance of the suggested approach is 100, the FAR is 0.1, and the EER is 0.1. To demonstrate the efficacy of the suggested system, the suggested method is contrasted with a few other approaches currently in use.

Rational design of fluorescent nanoparticles: From wavelength redshift to increased water solubility for stable and high-resolution imaging of latent fingerprints

Efficient and accurate visual identification of latent fingerprints is crucial in areas such as criminal investigation and information security. Aggregation-induced luminescence (AIE) fluorescent materials are widely used in this field because of their strong fluorescence and easy functionalization. They have attracted significant interest and emerged as a promising area since the introduction of the AIE concept. Here a new water-soluble fluorescent nanoparticle, flu-p-DITPA, through amphiphilic self-assembly with amphiphilic polymers macro-CTA-mPEG2000 (P1) and exhibits typical AIE properties. The core molecule, indo-DITPA, derived from the triphenylamine backbone, was obtained through rational molecular design and theoretical calculations, and the calculated results were confirmed with experimental results. The photophysical properties of indo-DITPA and flu-p-DITPA have been meticulously studied, revealing their remarkable characteristics. Taking advantage of their favorable photophysical properties, good water solubility, and biocompatibility, the researchers have devised a simple yet effective method for visualizing latent fingerprints (LFPs) with high resolution under UV light. This method enables the easy decoding of latent fingerprint information at primary, secondary, and tertiary levels. Importantly, this technique is simple, rapid, and user-friendly, marking a significant step forward in the field of forensic science and fingerprint analysis.

The highly efficient and stable near-infrared phosphor Ca3MgSnGe3O12: Cr3+ for multifunctional application

The investigation of efficient and stable near-infrared (NIR) luminescent materials is crucial for rapidly developing near-infrared spectroscopic techniques. Herein, NIR phosphors Ca3MgSnGe3O12: Cr3+ with ultra thermal stability and high internal quantum yield (IQY) are explored. The emission intensity remained at 91.75 %@423 K of room temperature and the IQY/EQE reaches 91.41 %/34.04 % after doping the H3BO3 flux agent for optimization. Moreover, a single luminescence center was identified by cryogenic photo luminescence spectroscopy (PL) from 4 K to 300 K and lifetime decay curve. Importantly, NIR light can easily removes all kinds of background interference that cannot be easily eliminated by visible light, which is not only widely used in night vision and biological tissue penetration, but also has higher application prospects in NIR fingerprint detection. Moreover, it clearly displays high level of fingerprint details under high temperature conditions and after water immersion, thus it is perfectly suited for using in Automatic Fingerprint Identification System (AFIS) systems. Therefore, Ca3MgSnGe3O12: Cr3+ NIR pc-LEDs have great potential for latent fingerprint detection at actual crime scenes.

DACTYLOGRAPHY: The Scientific Study of Fingerprint

Fingerprint analysis has become important because of its reliability and scientific explanation in the courts. Fingerprint has three principles classification, uniqueness and identification. Now there are digital biometric scanner has the ability to access by fingerprint within a minute. This Automated Fingerprint Identification System has made easier to accessible. But the reliability would be little less than other ways to identify fingerprints. Because due to the malfunction of the scanner database can be manipulated or hacked by anyone to access the security. There are various types of fingerprints which needed to know for analyzing it. These types are 1. Patent Fingerprint(visible) 2. Latent Fingerprint(invisible) 3. Plastic/3d; to developing fingerprints there are different methods for different types of fingerprint. Fingerprint experts tend to develop fingerprint in crime scene for solving the crime. Whereas fingerprint become most important physical evidence in matter of solving crime. For developing to analyzing fingerprint expertise would be necessary for establishment. But there are various challenges for forensic experts which are distort prints, smudge prints, contaminated crime scene, database error, partial prints, etc. for the recording of the fingerprint on the wall also be challenging for experts which only can be recorded by photography. Henry classification system would be time consuming to evaluate the recorded fingerprints. Then there is chemical method to develop fingerprint due to the secretion of sweat, oil and other body fluids which make an invisible print. The outermost skin layers have various pores through where body fluid tend to secrets which is responsible for making fingerprints. To make it visible various chemical need to apply so that the secreted body fluid will react with chemical and its visibility will appear. There are some pattern types which tend to administer the individuality such as Arch, Loop and Whorl. Every pattern in itself is unique which can’t be match with any other person. Another way is ridge characteristics which is also valuable way to identify fingerprint. Because of its unique characteristics which tend to differ for every person and not only one characteristics but also 14 ridge characteristics are possible to identify through fingerprint. Porescopy and Edgescopy these are other ways to identify fingerprints but it is not practicable in India right now. There are basic two ways to develop latent fingerprints powder method and chemical methods. Through powder method, various powder and brushes will be need to develop fingerprints but it need to be know the surface where fingerprints are found. In chemical method there would be various chemical compound which needed to apply for the development of the latent fingerprints

Green Synthesis of Nanoparticles for Forensic Applications: A Comprehensive Review on Latent Fingerprint Development

Green Synthesis of Nanoparticles for Forensic Applications: A Comprehensive Review on Latent Fingerprint Development

A Comprehensive Review of Small Particle Reagent Efficacy in Developing Latent Fingerprints Immersed in Water: An Empirical Analysis

A latent fingerprint is a shred of inevitable evidence left on a scene of the crime by the offender. Being aware of fingerprints, offenders tend to deteriorate all possible pieces of evidence by different methods that include burning, immersing the evidence in water, and many more. Water-immersed latent fingerprints are still viable for the development process due to the presence of water-insoluble components (Lipids, oils, etc.) in the latent fingerprint. Different methods have been tested for the imaging of water-immersed latent fingerprints among which Small Particle Reagent (SPR) was found to be the most efficient by many researchers. This method involves the application of fine particles suspended in a reagent based liquid medium onto the surface containing latent prints immersed in water, resulting in the development of highly detailed fingerprint impressions. The reagent comprised of hydrophobic head and hydrophilic tails that adhere to latent fingerprint and suspended particle respectively and thus act as a junction among them. The diverse composition of Small Particle Reagent, various surfaces for taking impressions of latent fingerprint (followed by immersing in water), the Shelf life of SPR, immersion time of latent fingerprint, and various immersion medium studied by researchers has been reviewed in this paper. The maximum shelf life of SPR reported by a researcher is 6 months and the maximum immersion time is 45 days. Furthermore, the need for green synthesis of SPR is emphasized due to its toxicity caused by long-term exposure.

Strongly Fluorescent Blue-Emitting La2O3: Bi3+ Phosphor for Latent Fingerprint Detection.

Blue-emitting bismuth-doped lanthanum oxide (La2O3: Bi3+) with various concentrations of Bi was synthesized using the sol-gel combustion method and used for visualization of latent fingerprints (LFPs). An X-ray diffraction (XRD) study revealed the hexagonal structure of the phosphors and total incorporation of the bismuth in the La2O3 matrix. Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used to study the morphology and the relative vibrations of the synthesized samples. Photoluminescence (PL) studies showed strong blue emission around 460 nm due to the 3P1 → 1S0 transition. Clear bright-blue fingerprint images were obtained with the powder dusting method on various surfaces like aluminum, compact discs, glass, wood and marble. A first evaluation of these images indicated a clear visualization of all three levels of details and a very high contrast ranging from 0.41 on marble to 0.90 on aluminum. As a further step, we used an algorithm for extracting fingerprint minutiae with which we succeeded in detecting all three levels of fingerprint details and even the most difficult ones, like open and closed pores. According to these analyses, La2O3: Bi phosphor is demonstrated to be an effective blue fluorescent powder for excellent visualization of latent fingerprints.

Influence of carbon dots integrated in Pr3+ doped gahnite nanophosphor for thermal sensing, data fortification and fingerprint visualization analysis through YOLOv8x deep learning embedded model

The remarkable optical properties of carbon dots (CDs) render them highly promising as a versatile group of carbon-based nanomaterials. Integrating hydrothermally synthesized CDs into zinc aluminate doped with Pr3+ ions (ZnAl2O4:Pr3+) nanophosphors (ZAO:Pr3+ NPs) fabricated via the solution combustion (SC) technique holds great potential. The aim of synthesizing these nanocrystals (NCs) is to explore their potential uses in optical thermometry and anti-counterfeiting (AC) measures. The synthesized nanoparticles (NPs) and nanocomposites (NCs) underwent characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra to verify their phase, morphology, particle size, oxidation state, and chemical composition. When excited at 447 nm, the Pr3+ doped ZAO: NPs exhibited an orange-red emission band at 614 nm. A remarkable enhancement in PL intensity, by a factor of 39.02 folds, is noted upon embedding CDs into the ZAO:Pr3+ NPs (CDs@ ZAO:Pr3+). The enhanced PL intensity can be ascribed to the Förster resonance energy transfer (FRET) mechanism. Even at a temperature of 423 K, the NPs retains 95.4% of its emission intensity compared to that at room temperature, showcasing exceptional thermal stability. The 5 wt% CDs@ZAO:1Pr3+ NCs demonstrate a high colour purity (CP) of 98.3%. Moreover, these NCs hold promise for optical thermometry applications across a broad temperature range spanning from 303 to 463 K. Utilizing the exceptional ZAO:1Pr3+ NPs and 5 wt% CDs@ZAO:1Pr3+ NCs, two representative white light emitting diodes (w-LEDs) have been successfully developed, boasting satisfactory luminous efficacy and colour-rendering index (CRI). This underscores their potential for high-performance w-LED applications. Simultaneously, a highly sensitive, non-contact optical thermometer has been engineered, featuring maximum relative sensitivities of approximately 44.51×10−4K−1 and 75.48×10−4K−1 at the emission intensities corresponding to 673, 693, 712 and 735 nm, respectively. We have developed a simple brush mode technique for creating a variety of patterns using the manufactured AC security ink. The latent fingerprints (LFPs) visualized using 5 wt% CDs@ZAO:1Pr3+ NCs exhibit excellent resolution and contrast, enabling the easy identification of fingerprint characteristics from levels I-III. Employing deep learning utilizing the YOLOv8x algorithm, fluorescence images of the revealed LFPs demonstrate remarkable alignment with standard controls, suggesting a high degree of similarity. In addition, the fabricated white light emitting diode (w-LED) boasts a favorable colour rendering index (Ra=87) alongside Commission International de L′Eclairage (CIE) coordinates (0.617, 0.376). Consequently, the inclusion of 5wt% CDs@ZAO:1Pr3+NPs showcases remarkable luminescent attributes and holds promising prospects across various applications.

Curcumin Analogues as Organic Fluorophores for Latent Fingerprint Imaging

AbstractSynthesis and characterization of two curcumin analogues BAA and Br‐AA via a condensation reaction was reported. Both the synthesized organic luminophores exhibited aggregation‐induced emission (AIE) with bright yellow and green emission respectively. Increase in the water% enhanced the emission by both the compounds confirmed the AIE property. A detailed study of latent fingerprints visualization was also carried out for both the analogues. Both the compounds showed good to normal capability to develop latent fingerprints (LFPs). Compound BAA performed better as a fluorescent material to develop LFPs compared to Br‐AA. The LFPs developed were analyzed to obtain 1–3 level of fingerprint patterns under UV 365 nm illumination. The LFPs developed using BAA exhibited excellent efficiency, sensitivity, high contrast with low background interreference. All three levels of fingerprint patterns were identified by BAA. However, Br‐AA showed inability to develop high clarity images of latent fingerprints. The solid‐state emission nature of the analogues was also evaluated from their emission spectra and CIE coordinates were found to be were (0,187, 0.518) and (0.265, 0.484) for BAA and Br‐AA respectively.

Study on mechanofluorochromism, ink-free writing, and latent fingerprint imaging of the functionalized difluoroboron compounds with methyl and methoxy

Two difluoroboron compounds including amide linkage moiety, compound F-1 with methoxy group and compound F-2 with methyl group, were designed and successfully synthesized. The results indicated that the solid powders of two compounds both displayed mechanofluorochromism phenomena, which originated from phase transformation between the well-ordered microcrystalline and amorphous states, and the intramolecular charge transfer, as well as the mechanofluorochromism of compound F-1 was better than that of compound F-2 due to larger dipole moment change value between the ground and excited states. Additionally, compound F-1 had more twisted molecular spatial conformation, which exhibited aggregation-induced emission in mixtures of THF/water, yet compound F-2 was observed aggregation-caused quenching phenomenon. It was gratified that two compounds had the potential application in the field of ink-free writing owing to their reversibly mechanofluorochromism behaviors, not only that, compound F-1 could be used to latent fingerprint imaging because of its aggregation-induced emission feature.

A Novel Synthesis Method of Dumbbell-like (Gd1-xTbx)2O(CO3)2·H2O Phosphor for Latent Fingerprint.

A novel method for synthesizing dumbbell-shaped (Gd1-xTbx)2O(CO3)2·H2O (GOC:xTb3+) phosphors using sodium carbonate was investigated. An amount of 1 mmol of stable fluorescent powder can be widely prepared using 3-11 mmol of Na2CO3 at a pH value of 8.5-10.5 in the reaction solution. The optimal reaction conditions for the phosphors were determined to be 7 mmol for the amount of sodium carbonate and a pH of 9.5 in the solution. Mapping analysis of the elements confirmed uniform distribution of Gd3+ and Tb3+ elements in GOC:xTb3+. The analysis of fluorescence intensity shows that an optimal excitation wavelength of 273 nm is observed when the concentration of Tb3+ is between 0.005 and 0.3. The highest emission intensity was observed for GOC:0.05Tb3+ with a 57.5% maximum quantum efficiency. The chromaticity coordinates show that the color of GOC:Tb3+ is stable and suitable for fluorescence recognition. Latent fingerprint visualization reveals distinctive features like whorls, hooks, and bifurcations. Therefore, the sodium carbonate method offers an effective alternative to traditional urea chemical reaction conditions for preparing GOC:Tb3+.

Supremacy of l-glutamic acid on cerium doped ZnS nanoparticles for enhanced structural, morphological, optical properties and their applications in antimicrobial activity with efficient detection of latent fingerprints

The pure Zinc Sulphide (ZnS) and l-Glutamic acid capped Cerium doped Zinc Sulphide nanoparticles of different concentrations (0, 5, 10 & 15 mol %) was developed via a simple chemical co-precipitation strategy. l-Glutamic acid is the a minimum hazardous, non-essential amino acid group, and its capped properties are optimal for semiconducting nanoparticles that include ZnS. It also has a considerable effect on enhancing the structural, optical, and photoluminescent properties of Ce-doped ZnS nanoparticles. The produced nanoparticles were examined using X-ray diffraction (XRD), dynamic light scattering (DLS), Field emission scanning electron microscope (FESEM), Fourier transform Infrared spectroscopy (FT-IR), Photoluminescence (PL), and UV–Vis spectrometer. The XRD pattern revealed that all of the generated nanostructures have a cubic form with diffraction planes (111), (220), and (311), and the dimensions of the crystallite ranging from 1.685 nm to 2.144 nm. Its morphological view of nanoparticles was investigated utilizing FESEM. DLS testing demonstrated that the particle sizes were less than 30 nm. The functional groups of nanoparticles have been identified using FTIR investigations. PL investigations suggested the existence of substantial emission bands. The ultraviolet–visible scrutiny exhibited an optical band gap that spans 3.12–3.77 eV. The antimicrobial activity analysis was examined by the gram-positive and gram-negative bacteria in pure ZnS, l-glutamic acid-capped ZnS, and glutamic-capped 15 mol% Ce-doped ZnS, with their inhibitory zones also verified. Finally, it was ascertained that this type of nanoparticles was highly effective to reveal the fingerprints detection purposes in forensic applications.

Rapid, autonomous and ultra-large-area detection of latent fingerprints using object-driven optical coherence tomography

The detection of latent fingerprints plays a crucial role in criminal investigations and biometrics. However, conventional techniques are limited by their lack of depth-resolved imaging, extensive area coverage, and autonomous fingerprint detection capabilities. This study introduces an object-driven optical coherence tomography (OD-OCT) to achieve rapid, autonomous and ultra-large-area detection of latent fingerprints. First, by utilizing sparse sampling with the robotic arm along the slow axis, we continuously acquire B-scans across large, variably shaped areas (∼400 cm2), achieving a scanning speed up to 100 times faster. In parallel, a deep learning model autonomously processes the real-time stream of B-scans, detecting fingerprints and their locations. The system then performs high-resolution three-dimensional imaging of these detected areas, exclusively visualizing the latent fingerprints. This approach significantly enhances the imaging efficiency while balancing the traditional OCT system's trade-offs between scanning range, speed, and lateral resolution, thus offering a breakthrough in rapid, large-area object detection.

Tetraphenylethylene tethered 1-(pyridine-2-yl)imidazo[1,5-a]pyridine: Synthesis, aggregation induced emission, copper(II) ion detection and imaging of latent fingerprint

The development of aggregation induced emissive probe with high sensitivity and selectivity for Cu2+ ions is a fascinating research in biomedical sciences. In this context, we have successfully synthesized an aggregation induced emissive probe for the selective detection of Cu2+ ions by incorporating a 1-(pyridine-2-yl)imidazo[1,5-a]pyridine arm in the tetraphenylethylene framework. The aggregates have been characterized using pivotal microscopic and photophysical measurements. The results exhibits that the aggregates have a spherical shape with an average size of 90 nm and a fluorescence quantum yield of ∼23 %. The aggregated fluorescent probe exhibited an excellent selectivity towards Cu2+ ions with a detection limit of 83 nM and presented a good efficacy over diverse environmental water samples. Furthermore, the quenching type is delineated as static due to complexation followed by deaggregation which was supported by dynamic light scattering and Tyndall effect experiments. In addition, the high solid state emissive property of the probe makes it a potential candidate for latent fingerprint analysis to gather level 2 and 3 information thereby playing a substantial role in forensic investigations.

Two Aggregation‐Induced Emission Actives Triphenylamine‐Based Salicylaldimine Compounds for Latent Fingerprints Detection

AbstractTo further explore the candidate materials for latent fingerprints detection, two triphenylamine‐based salicylaldimine compounds containing phenoxazine moiety (TPA‐PXZ) and carbazole unit (TPA‐Cz) were designed and successfully synthesized, respectively. They exhibited intramolecular charge transfer transitions and aggregation‐induced emission properties. Based on quantum chemical calculation results, it was found that compounds TPA‐Cz and TPA‐PXZ had twisted spatial configuration, which were responsible for aggregation‐induced emission. Meanwhile, the morphology of two compounds nano‐aggregates in the THF/water mixtures with 60 % and 80 % water content was tested. To our delight, the developers that prepared by compounds TPA‐Cz and TPA‐PXZ both were used for latent fingerprints detection on the surface of glasses, and they emitted purple fluorescence, as well as the distinct fingerprint imaging could be easily distinguished fingerprint level 1–3 details. We believe that TPA‐Cz and TPA‐PXZ both are the promising candidate for latent fingerprints detection.

Forensic identification of fingerprints on various substrates based on fluorescent carbon nanodots from date seeds assisted by Tracker software

Fingerprint identification is done by observing fingerprint patterns usually found on various surfaces at crime scenes. However, fingerprints are easily damaged, erased, and/or lost. Therefore, alternative materials are needed that can preserve fingerprint patterns. In this study, we use carbon nanodots (C-dots). This research aims to prepare and characterize C-dots made from date seeds, and then determine the robustness of the latent fingerprints using C-dots on various printed substrates assisted by Tracker software. This is experimental research of preparing and characterizing fluorescent C-dots from date seeds and printing fingerprints on various substrates. The C-dots were prepared using oven and microwave heating methods and characterized using an ultraviolet-visible (UV-Vis) spectrophotometer, photoluminescence (PL), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and particle size analyzer (PSA). The substrates used for printing the fingerprints were plastic, ceramic, paint, and glass. Based on the characterization results, the C-dots have i) an absorption peak at wavelength of 252.2 nm (core) and band gap energy of 3.27 eV, ii) an emission wavelength of 495 nm emitting cyan color, iii) an amorphous structure based on the diffraction pattern, iv) functional groups of C-H, CC, CC, and O-H, and v) particle sizes of 1.3 nm (< 10 nm). Moreover, the results of the fingerprint identification based on the visualization test were successful because a subject’s fingerprint pattern was formed and various patterns were identified. In the robustness test, the latent fingerprints lasted 30 days and then slightly faded in the whorls pattern.

Development of silica gel from Lapindo volcanic mud as fluorescent fingerprint powder based on methyl orange

Fingerprint powder remains one of the most effective techniques for identifying individuals from their latent fingerprints. Visualizing latent fingerprints requires powder with high color contrast and strong adhesive to be easily applied on various substrates. The utilization of silica gel extracted from local materials of Lapindo volcanic mud can be applied for fluorescent fingerprint powder based on methyl orange. The powder was synthesized by the sol-gel method, followed by the impregnation of methyl orange as a dye with varying loads. The powders exhibit an amorphous structure and nanoparticle size with an average particle diameter of 80.93 nm by spherical morphology interconnected to form agglomerations. The powder contains silanol, siloxane, azo, and carboxylate functional groups derived from its precursors. The dusting method proves the performance of fluorescent fingerprint powder on porous and non-porous substrates hereafter observed under white light and UV light. The powder containing 0.05 gs of methyl orange per gram of silica gel is the most effective in revealing fingerprint patterns on non-porous surfaces. It has mesoporous properties with a specific surface area of 7.95 m2g−1 and a pore diameter of 23.14 nm. SiMO retained its full capability after two years of storage, indicating it is a great choice for forensic investigations.

A novel fluoroapatite-type phosphor Ca2Y8(BO4)2(SiO4)4F2:Eu3+ with high quantum efficiency and good thermal stability for multimodal applications☆

A novel Eu3+ doped fluorapatite red phosphor Ca2Y8(BO4)2(SiO4)4F2:Eu3+ with pure phase was synthesized in this study. Density functional theory (DFT) calculation and diffuse reflection spectrum analysis reveal its potential as a matrix for phosphors excited by ultraviolet light. Eu3+ has a 7F0→5L6 transition at 394 nm, and the prepared phosphor exhibits a high emission intensity at 614 nm, which may be attributed to the 5D0-7F2 energy transition at the lower symmetry site of Eu3+. The optimal doping concentration of the phosphor is determined to be 11 mol%, with concentration quenching attributed to the exchange interaction mechanism. The overall color purity of the phosphor is up to 99.88%, with an internal quantum efficiency as high as 91.15%. Notably, Ca2Y8(BO4)2(SiO4)4F2:11 mol%Eu3+ (CYBSF:11 mol%Eu3+) phosphors exhibit good thermal stability, with a thermal quenching temperature (T1/2) of 552 K and the intensity of emission at 423 K still at 88.89% of that at 298 K. The activation energy of the phosphor is up to 0.30287 eV. Its comprehensive luminescence performance surpasses that of commercial red phosphor, making it suitable for near ultraviolet excited warm white light emitting diode (NUV-WLED) with a high color rendering index (Ra = 82) and a correlation color temperature (CCT) of 4339 K. Moreover, the phosphor achieves latent fingerprint visualization and anti-counterfeiting ink on different material surfaces: glass, aluminum foil, plastic and paper. Overall, the fluorapatite CYBSF:11 mol%Eu3+ phosphor holds great potential for multimodal applications due to its high quantum efficiency and good thermal stability.

Encapsulating Fe3O4 Nanoparticles and Carbon Dots in a Metal-Organic Framework for Magnetic Fluorescent Taggants.

Magnetic fluorescent composite nanomaterials have broad application prospects in the fields of biological imaging, anticounterfeiting identification, suspicious object tracking, and identification of latent fingerprints in forensic medicine. For an effective taggant, a clearly visible identifying mark is necessary to enable observers to capture labeling information quickly and accurately, even from a distance. The preparation method of magnetic fluorescent composite materials is complicated and usually needs different surface modification and assembly processes. The limited loading capacity of fluorescent materials also limits the fluorescence properties of the composite, so it is difficult to produce obvious fluorescence as a taggant to meet the requirements of visible labeling. In this study, a core-shell structure of a magnetic fluorescent composite was prepared by using the metal-organic framework ZIF-8 as the host of fluorescent materials and an encapsulation shell coated on the Fe3O4 nanoparticles. The porous ZIF-8 is beneficial for increasing the loading capacity of fluorescent materials to ensure the fluorescence performance of the composite materials. Further modification of the composite surface prevented the desorption of fluorescent materials from the pores of ZIF-8, enabling the samples to maintain good fluorescence properties even after multiple washing cycles. The preparation method is simple, rapid, and cost-effective, and the prepared magnetic fluorescent composite nanomaterial has high magnetic separation performance and fluorescence performance, making it a promising material for identification, marking, and tracking.

Preliminary investigations into the use of the ancient pigments Han blue and Han purple as luminescent dusting powders for the detection of latent fingermarks

Here we present our preliminary studies into the inorganic pigments Han blue (BaCuSi4O10) and Han purple (BaCuSi2O6) as near-infrared luminescent fingerprint dusting powders. These pigments were developed in ancient China around 800 BCE and both show luminescence in the NIR region. There remains, however, ambiguity in the literature concerning their photophysical properties. Samples of Han blue and Han purple artist’s pigments were characterized by optical microscopy, infrared, ultraviolet-visible absorbance and luminescence spectroscopy. Their performance as fingerprint dusting powders, without any further treatment, on non-porous surfaces were compared to exfoliated lipophilic coated Egyptian blue and commercial fluorescent powders in a pilot study. These results demonstrate for the first time that both ancient pigments show promise as alternative dusting powders for latent fingermarks.