Latent Fingerprint Images Research Articles

Synthesis and characterization of fluorescent Europium (III) complex based on D-dextrose composite for latent fingerprint detection

A europium salt-Na[Eu(5,5′-DMBP)(phen)3]·Cl3 (Eu(III)-CPLx) was prepared by using various precursors such as 5,5′-Dimethyl-2,2′-bipyridyl (5,5′-DMBP), 1,10-phenanthroline (phen) and europium chloride hexahydrate (EuCl3·6H2O) by a complexation method. The red emission fluorescent Na[Eu(5,5′-DMBP)(phen)3]·Cl3/D-Dextrose (Eu(III)-CPLx/D-Dex) composite was synthesized by using an adsorption method with Eu(III)-CPLx and D-Dextrose (D-Dex). The Eu(III)-CPLx and fluorescent (Eu(III)-CPLx/D-Dex) composites were characterized by numerous techniques. The fluorescent (Eu(III)-CPLx/D-Dex) composite demonstrated a strong red emission and controlled fluorescence quenching in the solid state and was consequently used in latent fingerprint (LFP) detection. The LFPs were developed by using a powder dusting method (PDM) with Eu(III)-CPLx and fluorescent Eu(III)-CPLx/D-Dex composites on different substrates under daylight and UV-light irradiation at 365 nm. The fluorescent Eu(III)-CPLx/D-Dex composite was effectively explored for developing LFP images on various substrates and also acts as a better labeling agent for LFP detection in forensic science crime scene investigations.

Bright red-luminescence of Eu3+ion-activated La10W22O81 microphosphors for noncytotoxic latent fingerprint imaging

An intense red emission from Eu 3+ : La 10 W 22 O 81 (LWO) microphosphor rods has been obtained under UV excitation source for latent fingerprint (LFP) imaging. Microphosphor rods of LWO doped with various concentrations of Eu 3+ ions were synthesized using a hydrothermal assisted solid-state method. XRD revealed that the microphosphors had an orthorhombic structure with the space group of Pbcn (60). FE-SEM showed that the surface morphology of the optimized Eu 3+ (14 mol %): LWO microphosphors were hexagonal rods with pencil-like tips at both ends. TEM evaluation with elemental mapping and XPS analysis confirmed the occurrence of the vital elements in the microrods. FTIR spectral analysis was performed for the analysis of the spectral bands. An intense red emission was obtained from the Eu 3+ doped LWO microphosphors under the excitation of 394 nm ( 7 F 0 → 5 L 6 ) which could be attributed to the hypersensitive transition of 5 D 0 → 7 F 2 pertaining to the Eu 3+ ions. Enhancement of the emission was noticed from the microphosphors when the Eu 3+ content was increased. Optimal red emission was obtained with the Eu 3+ (14 mol %): LWO microphosphor. The photoluminescence intensity was found to be reduced after optimized concentration due to concentration quenching. The quadrupole–quadrupole interaction is found to be responsible for concentration quenching. The luminescent properties were systematically demonstrated using an energy level scheme diagram. The luminescence lifetime was evaluated for all the concentrations of Eu 3+ doped LWO samples. The lifetime decay dynamics has also been clearly elucidated. CIE color coordinates were also evaluated from the luminescence spectra of the microphosphors and they are found to be located in strong red region. A significant luminescence quantum yield was determined for the Eu 3+ (14 mol %): LWO microphosphor. The optimized microphosphor was used in detecting LFPs, employing the powder dusting method commonly used in forensic science. We detected the LFP ridge patterns with high sensitivity, reliability, and selectivity by using the optimized microphosphor. Its non-cytotoxic nature was also evaluated using WI-38 cell lines. Results demonstrated that the Eu 3+ (14 mol %): LWO microphosphor could be a promising candidate for luminescent applications and LFP applications in forensic investigation preferably. • Dazzling red emissive Eu 3+ : La 10 W 22 O 81 microphosphors were synthesized. • Strong red emission was enhanced by increasing the Eu 3+ ion concentration. • Reason for concentration quenching has also been clearly elucidated. • Lifetime, Quantum yield, CIE coordinates and cytotoxicity were extensively studied. • Latent finger print application was performed with optimized sample.

Electrochemiluminescence imaging of latent fingerprints by electropolymerized luminol

An efficient method has been developed for visualizing latent fingerprints by spatially selective electropolymerization of luminol on the ITO electrode. The fingerprint deposited on the electrode surface functions as a mask so that polyluminol is formed on the bare electrode surface. Therefore, electrochemiluminescence is only generated between the ridges of fingerprint, eventually yielding a negative ECL image. This method is easy to operate and safe to examiners. In addition, the second- and third-level details of fingerprints can be well resolved, indicating the potential application for personal identification and forensic investigation.

Label-free physical and electrochemical imaging of latent fingerprints by water and SECM

A label-free method that can doubly image both the physical patterns and the electrochemical information of latent fingerprints (LFPs) on nitrocellulose (NC) membrane has been achieved here by water and scanning electrochemical microscopy (SECM). In this approach, the NC membrane with LFP (LFP/NC) sample was first placed in water, where the different absorption of water onto relatively hydrophobic ridge residues of LFP versus NC membrane background resulted in a high-resolution physical ridge pattern of the fingerprint to naked eyes within just 1–3 s and could further be photographed by a digital camera. Thereafter, the LFP/NC sample was electrochemically imaged by recording the current variations of SECM tip scanning over the label-free fingerprint in the surface-interrogation (SI) mode. The methyl viologen (MV2+) was chosen as the redox mediator to react selectively with the electroactive species in the fingerprint ridge residues rather than furrow regions, which could cause the sharp contrast of the SECM tip current for imaging. Both the collected physical and electrochemical images of LFPs can provide high resolution up to level 2 and level 3 features required for personal identification. In addition, for the first time commercial NC membrane instead of adhesive forensic tape was discovered here for lifting the LFPs from various surfaces, which can then be imaged by this electrochemical approach. Taken together, this method demonstrates a powerful strategy for directly imaging the electrochemical information in LFPs without damaging the fingerprint physical ridge pattern on various substrates, so it has great potentiality in individual identity related applications.

Real-Time Fluorescence In Situ Visualization of Latent Fingerprints Exceeding Level 3 Details Based on Aggregation-Induced Emission.

A water-soluble probe, TPA-1OH, with aggregation-induced emission activity is synthesized and used for expedient real-time fluorescence in situ visualization of latent fingerprints (LFPs). A TPA-1OH aqueous solution exhibits nonfluorescence in pure water while strong fluorescence upon molecular aggregation induced by addition of poor solvent. Fluorescence images of LFPs on a variety of substrates, including rough surfaces such as walls, bricks, and paper, are developed under 405 nm light, by soaking in or spraying with a TPA-1OH aqueous solution (30 μM) without any necessity of organic cosolvents and post-treatment steps. The probe is noncytotoxic at a concentration lower than 50 μM. The development process of LFPs is demonstrated by real-time fluorescence in situ imaging. The exponential relationship between the relative fluorescence intensity and time is deduced from the fitting curve. The LFP images developed by TPA-1OH are evident and intact enough to allow that the level 1-3 details are displayed and analyzed. Noteworthily, the level 3 details of LFPs such as the fingerprint ridge width and the characteristics of the sweat pores are evidently visible under fluorescence microscopy. Even the nanoscopic details exceeding level 3 are visualized under super-resolution microscopy with sub-50 nm optical resolution.

Individual Cloud-Based Fingerprint Operation Platform for Latent Fingerprint Identification Using Perovskite Nanocrystals as Eikonogen.

Fingerprint formed through lifted papillary ridges is considered the best reference for personal identification. However, the currently available latent fingerprint (LFP) images often suffer from poor resolution, have a low degree of information, and require multifarious steps for identification. Herein, an individual Cloud-based fingerprint operation platform has been designed and fabricated to achieve high-definition LFPs analysis by using CsPbBr3 perovskite nanocrystals (NCs) as eikonogen. Moreover, since CsPbBr3 NCs have a special response to some fingerprint-associated amino acids, the proposed platform can be further used to detect metabolites on LFPs. Consequently, in virtue of Cloud computing and artificial intelligence (AI), this study has demonstrated a champion platform to realize the whole LFP identification analysis. In a double-blind simulative crime game, the enhanced LFP images can be easily obtained and used to lock the suspect accurately within one second on a smartphone, which can help investigators track the criminal clue and handle cases efficiently.

Novel red photoluminescence sensor based on Europium ion doped calcium hydroxy stannate CaSn(OH)6:Eu+3 for latent fingerprint detection

Herein, we have synthesized a novel CaSn(OH)6:Eu3+ nanoparticles modified with trisodium citrate (TSC) by using sol-gel technique for latent fingerprint technology. The particles are characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, optical absorption and photoluminescence (PL) studies as well as energy-dispersive spectroscopy (EDS). The morphology of the particles has been determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized nanoparticles CaSn(OH)6:Eu3+ phosphors emitted high intensity fluorescence peak at 616 nm upon excitation at 285 nm, which will provides latent fingerprint images with a high resolution, high contrast, high selectivity, high efficiency and low background interference on various substrates. The results show that CaSn(OH)6:Eu3+ employed in analytical detection of visualization of latent fingerprints (LFPs) for individual identification in forensic science.

Simultaneous imaging of latent fingerprint and quantification of nicotine residue by NaYF4:Yb/Tm upconversion nanoparticles

Numerous investigations have been devoted to visualizing latent fingerprints (LFPs) for personal identification in forensic investigation and age estimation. While simultaneous detection of chemicals in fingerprint residues has yet to be explored. Herein, fluorescent NaYF4:Yb/Tm up-conversion nanoparticles (UCNPs), which can emit blue fluorescence upon 980 nm near-infrared irradiation, have been employed in the imaging of LFPs with high contrast and high sensitivity. The furrows and ridges which provide detailed information of LFP have been displayed clearly by Tm-doped UCNPs. Meanwhile, the quantitation of nicotine residue in LFPs has been achieved based on the blue fluorescence absorbed by I2-nicotine complex, and the data was analyzed by MATLAB with modified OPTA algorithm. It was proved that the established strategy was specific, sensitive, reliable and practical toward nicotine residue in LFPs with a detection limit of 0.05 μg.

Biocompatible Fluorescent Nanodiamonds as Multifunctional Optical Probes for Latent Fingerprint Detection.

There is an immense literature on detection of latent fingerprints (LFPs) with fluorescent nanomaterials because fluorescence is one of the most sensitive detection methods. Although many fluorescent probes have been developed for latent fingerprint detection, many challenges remain, including the low selectivity, complicated processing, high background, and toxicity of nanoparticles used to visualize LFPs. In this study, we demonstrate biocompatible, efficient, and low background LFP detection with poly(vinylpyrrolidone) (PVP) coated fluorescent nanodiamonds (FNDs). PVP-coated FND (FND@PVP) is biocompatible at the cellular level. They neither inhibit cellar proliferation nor induce cell death via apoptosis or other cell killing pathways. Moreover, they do not elicit an immune response in cells. PVP coating enhances the physical adhesion of FND to diverse substrates and in particular results in efficient binding of FND@PVP to fingerprint ridges due to the intrinsic amphiphilicity of PVP. Clear, well-defined ridge structures with first, second, and third-level of LFP details are revealed within minutes by FND@PVP. The combination of this binding specificity and the remarkable optical properties of FND@PVP permits the detection of LPFs with high contrast, efficiency, selectivity, sensitivity, and reduced background interference. Our results demonstrate that background-free imaging via multicolor emission and dual-modal imaging of FND@PVP nanoparticles have great potential for high-resolution imaging of LFPs.

Development of AIEgen–montmorillonite nanocomposite powders for computer-assisted visualization of latent fingermarks

AIE–active montmorillonite nanocomposite powders (AIE–MMT) were developed for computer-assistant latent fingerprint (LFP) imaging.

An aggregation-induced emission luminogen combined with a cyanoacrylate fuming method for latent fingerprint analysis.

Fingerprints remain topologically unchanged in one's whole life, and therefore, have been used as a means to biometrically identify individuals in forensic investigations, law enforcement and access control. Appropriate methods are essential to obtain high-quality fingerprint images. In this contribution, an aggregation-induced emission luminogen tetraphenylethene-based dye FLA-2 was synthesized and characterized for the visualization of latent fingerprints (LFPs). LFPs can be directly visualized by incubating with the dye FLA-2 solution. And, after a cyanoacrylate fuming method pre-treatment stage, fine fingerprint structures can be obtained from level-1 to level-3 details. Two methods were compared using resolution, fluorescence intensity, and scanning electron microscopy imaging to investigate the influence of the cyanoacrylate fuming method pre-treatment stage. Furthermore, the visualization of old LFPs (7 d, 16 d and 30 d) on glass slides, aluminum foil and coin substrates also became effective after the pre-treatment step. The fluorescent LFP images mentioned above were all validated by using an automated fingerprint identification system obtaining positive matches. These results demonstrate the potential of this method to be applied to visualizing LFPs in the field of public security.

Fluorescent silicon nanoparticles as dually emissive probes for copper(II) and for visualization of latent fingerprints.

The work describes dually-emissive silicon nanoparticles (Si NPs) in aqueous dispersion with two emissions. The Si NPs respond to different solvents independently with various wavelength fluorescence emissions (red to green). The fluorescence emission wavelengths and emissive color of Si NPs can be regulated by adjustment of the solvents. Based on the effect of the solvent, a series different emission color Si NPs is obtained(Si NPsA, B, C and D), which exhibit different fluorescence emission in various solvents. Notably, the Si NP-A (dispersed in water) exhibited excellent analytical performance in sensing Cu2+ ions with amazing fluorescent response from green to brilliant blue light. The much more enhancement at 436nm than at 500nm was due to the changing surface chemistry of Si NPs by Cu2+, which was dependent to the concentration of Cu2+ tightly. The excellent sensitivity of Si NP-A towards Cu2+ has been testified with the detection limit as low as 0.91μM by good linear relationship between ratio of fluorescence intensity (I436/I500) and concentration of Cu2+ (2-30μM). The Si NP-A can be exploited as a dual-fluorescence visualization agent for latent fingerprints imaging due to the feature of dual emission. The images exhibited green emission under excited at 254nm, and emerged green light under 365nm, which allowed the Si NP-A applying in development of latent finger prints at complex background. These acquired fingerprints revealed the particular second-level characteristics. Graphical abstractIllustration of the method for preparation of safranine-dyes silica nanoparticle (Si NPs), the evolution of Si NP-A (VSi NPs/Vwate = 1:2). Si NP-B (VSi NPs/Vdichloromethane = 1:1), Si NP-C (VSi NPs/Vethyl acetate = 1:1) and Si NP-D (VSi NPs/Vacetone = 1:1), and the application of water-dispersed silica nanoparticles (Si NP-A) to the detection and visualization of latent fingerprints (LFPs).

Smart Responsive Luminescent Aptamer-Functionalized Covalent Organic Framework Hydrogel for High-Resolution Visualization and Security Protection of Latent Fingerprints.

Covalent organic frameworks (COFs) have been proposed as alternative candidates for "smart" materials due to their ordered π-columnar structures. However, it remains a challenge to develop external-stimuli-responsive luminescent COFs for confidential information protection. Here, we have designed and synthesized a water-dispersible and smart responsive luminescent carboxymethyl cellulose-COF hydrogel encapsulated 5-(dimethylamino)-N,N-bis (pyridin-2-ylmethyl) napthalene-1-sulfonamide, named CMC-COF-LZU1⊃DPYNS, for latent fingerprint imaging and encryption. We show that the fluorescence of CMC-COF-LZU1⊃DPYNS is reversibly switchable upon addition of Cu2+/H2O. This effect endows potential applications of tunable luminescent COFs based hydrogel as an invisible security probe for imaging, recording, storage, and security of latent fingerprint information. It is shown that the latent fingerprint information incubated by the aptamer-functionalized CMC-COF-LZU1⊃DPYNS hydrogel is invisible in the presence of Cu2+, but three levels of fingerprint features with high-resolution patterns could be readable upon addition of H2O under UV light. The design strategy provides a promising platform for the development of smart responsive luminescent COFs and their detection and protection of valuable latent fingerprint information.

Sensitive development of latent fingerprints using Rhodamine B-diatomaceous earth composites and principle of efficient image enhancement behind their fluorescence characteristics

Latent fingerprints, by definition, are not directly visible traces that usually found at crime scenes and need physical or chemical treatment before image capture and fingerprint identification. Research of novel powders for latent fingerprint development and establishment of efficient methods for fingerprint image enhancement have always been key focuses in forensic science and related fields involving chemistry, materials science and biology. Relying on physical adsorption between cationic fluorophores and porous silica, Rhodamine B-diatomaceous earth composites have been prepared as novel fluorescent fingerprint powders. A luminescence mode for latent fingerprint development and image enhancement that matches the fluorescence characteristics of these composites has been theoretically explained and a fingerprint image capture and processing system designed based on it has been successfully constructed. In the luminescence mode, the first and second level information of a latent fingerprint on the surface of an object showing either background interference or not can be precisely visualized and captured. This entire approach is demonstrated to be promising for scenarios of practical application.

Preparation of Aptamer-functionalized Au@pNTP@SiO2 Core-Shell Surface-enhanced Raman Scattering Probes for Raman Imaging Study of Adhesive Tape Transferred-Latent Fingerprints

Abstract The core-shell SERS nanoprobe combined with adhesive tape was used to recognize the latent fingerprints on the surface of the object, which provides an effective solution for the imaging of latent fingerprints on the surface of large immobile or curved objects. First, the Au@pNTP@SiO2 SERS probes modified by aptamers specific to lysozyme were prepared, and characterized by TEM/EDS, and its SERS effects were also tested. Then the probe was incubated with the aged-latent fingerprints on the surface of different objects. Afterwards, the dried latent fingerprint with modified SERS probes was transferred to the adhesive tape and imaged under the confocal Raman microscope. The results showed that the size distribution of the core-shell SERS probe was uniform, which was mostly concentrated in 60 nm, leading to excellent stability and dispersity. The SERS probe also had strong SERS intensity and reproducibility with the characteristic peaks at 723, 855, 1081, 1343 and 1572 cm−1, which were consistent with the previous reports. When applying such SERS probe into the tape-transferred latent fingerprint's imaging, not only the primary structure (pattern) but also the secondary structure (forking and ring points) and the third-level structure of fingerprint (sweat pore) could be clearly observed. The successful development of the SERS imaging of transferred latent fingerprint on adhesive tapes combined with the aptamer-functionalized SERS probe provides an effective method for recognizing latent fingerprints in forensic science, which also has the potential applications in the other areas such as food safety and public safety testing.

Regioselective Functionalization of Stable BN-Modified Luminescent Tetraphenes for High-Resolution Fingerprint Imaging.

A series of novel BN tetraphene derivatives have been prepared successfully for the first time via a post-functionalization strategy. The optical and electronic properties of these derivatives could be tuned systematically by the incorporation of different substituents on the main skeleton. The functionalized BN-containing luminogens have been explored for the detection of latent fingerprints (LFPs) on different substrates, including glass, aluminum foil, plastic, and ironware. This strategy provides great versatility in LFP imaging and good potential in elucidating the chemical information within LFPs, making the strategy valuable in forensic investigations.

Regioselective Functionalization of Stable BN‐Modified Luminescent Tetraphenes for High‐Resolution Fingerprint Imaging

AbstractA series of novel BN tetraphene derivatives have been prepared successfully for the first time via a post‐functionalization strategy. The optical and electronic properties of these derivatives could be tuned systematically by the incorporation of different substituents on the main skeleton. The functionalized BN‐containing luminogens have been explored for the detection of latent fingerprints (LFPs) on different substrates, including glass, aluminum foil, plastic, and ironware. This strategy provides great versatility in LFP imaging and good potential in elucidating the chemical information within LFPs, making the strategy valuable in forensic investigations.

Latent Fingerprint Imaging Using Dy and Sm Codoped HfO2 Nanophosphors: Structure and Luminescence Properties

AbstractThe development of latent fingerprints (LFPs) detected at the site of crime is considered as an imperative physical evidence in forensic investigations. Herein, a rapid and cost‐effective approach using nonhazardous Dy and Sm codoped HfO2 nanophosphors is demonstrated to be utilized for LFP imaging. Sol–gel method can produce Dy and Sm codoped HfO2 of monoclinic phase with crystallite size ranging from ≈10 to 25 nm. While selected area electron diffraction and lattice spacing calculated from high‐resolution transmission electron microscopy confirm monoclinic phase, Le‐Bail profile refinement of X‐ray diffraction (XRD) patterns demonstrate an exponential increase in lattice volume with incorporating various concentrations of Dy and Sm in HfO2 lattice. Exciting Dy and Sm codoped HfO2 with 393 nm photoluminescence spectra show emissions in blue, yellow, and near red regions emerging primarily due to energy transfer from Dy3+ to Sm3+ through multipolar interaction suggested by time resolved decay spectra. Combining excitation and emission spectra, an energy band diagram is proposed. Owing to excellent emissions, Dy and Sm codoped HfO2 are explored for LFP imaging with good selectivity and resolution over multivariate surfaces like float glass and aluminum foil. The third‐level details like enclosure and termination–bifurcation are extracted due to nanosized nature of particles.

Gaze behavior and cognitive states during fingerprint target group localization

BackgroundThe comparison of fingerprints by expert latent print examiners generally involves repeating a process in which the examiner selects a small area of distinctive features in one print (a target group), and searches for it in the other print. In order to isolate this key element of fingerprint comparison, we use eye-tracking data to describe the behavior of latent fingerprint examiners on a narrowly defined “find the target” task. Participants were shown a fingerprint image with a target group indicated and asked to find the corresponding area of ridge detail in a second impression of the same finger and state when they found the target location. Target groups were presented on latent and plain exemplar fingerprint images, and as small areas cropped from the plain exemplars, to assess how image quality and the lack of surrounding visual context affected task performance and eye behavior. One hundred and seventeen participants completed a total of 675 trials.ResultsThe presence or absence of context notably affected the areas viewed and time spent in comparison; differences between latent and plain exemplar tasks were much less significant. In virtually all trials, examiners repeatedly looked back and forth between the images, suggesting constraints on the capacity of visual working memory. On most trials where context was provided, examiners looked immediately at the corresponding location: with context, median time to find the corresponding location was less than 0.3 s (second fixation); however, without context, median time was 1.9 s (five fixations). A few trials resulted in errors in which the examiner did not find the correct target location. Basic gaze measures of overt behaviors, such as speed, areas visited, and back-and-forth behavior, were used in conjunction with the known target area to infer the underlying cognitive state of the examiner.ConclusionsVisual context has a significant effect on the eye behavior of latent print examiners. Localization errors suggest how errors may occur in real comparisons: examiners sometimes compare an incorrect but similar target group and do not continue to search for a better candidate target group. The analytic methods and predictive models developed here can be used to describe the more complex behavior involved in actual fingerprint comparisons.

Latent Fingerprint Identification Using Deep Learning Method

Digital fingerprint is one of the most consistent modalities in up to date biometrics and hence has been broadly studied and deploy in real applications. The accuracy of one Automatic Fingerprint Identification System (AFIS) largely depends on the quality of fingerprint samples, as it has an important impact on the degradation of the matching (comparison) error rates. This thesis generally focuses on the evaluation of biometric quality metrics and Fingerprint Quality Assessment (FQA), particularly in estimating the quality of gray-level latent fingerprint images or represented by minutiae set. By making a refined review of both biometric systems and relevant evaluation techniques, this contribute by the definition of a new evaluation or validation outline for estimating the performance of biometric quality metrics. It is defined to check the quality of latent fingerprint images by statistically measured parameters. In this work, an automatic Region-Of-Interest (ROI)-based latent fingerprint quality assessment technique is proposed by using deep learning. The first stage in our model uses deep learning, namely Region Convolutional Neural Network (R-CNN) to segment a latent fingerprint. In the second stage, feature vectors computed from the segmented latent fingerprint are used as input to a multi-class perceptron that predicts the value of the fingerprint. This proposed approach eliminates the need for manual ROI and feature markup by dormant examiners. Finally, experimental results on NIST SD27 show the effectiveness of our technique in latent fingerprint quality prediction