Latent Fingerprint Images Research Articles

New fluorescent electrospun polymer materials containing phenothiazinyl carboxylate metal salts for versatile latent fingerprint detection

In this work the synthesis and structural characterization by NMR and single crystal X-Ray Diffraction of four new phenothiazine-carboxylate salts (lithium, sodium, potassium, and calcium salts respectively) is reported together with a description of their use as contrast agents in the fabrication of new fluorescent electrospun polyvinylpyrrolidone nanomaterials suitable for latent fingerprint (LFP) detection were reported.The optical properties of the new fluorophores and fluorescent electrospun polymer (FEP) nanomaterials (λem = 448–467 nm) were evaluated by UV–Vis absorption/emission spectroscopy. Fluorescence lifetime imaging microscopy (FLIM) analysis indicated an intense and uniform fluorescence in solid state, with fluorescence lifetime increasing significantly for FEP material (8–11 ns) in comparison to the correspondent blank fluorophore. Scanning electron microscopy (SEM) investigations revealed the size of the new FEP materials situated in the nanometric range with fiber or granular morphology.The newly synthesized FEP nanomaterials were successfully tested in the detection of LFP from various smooth or porous surfaces such as glass, metal, plastic, ceramic or wood and demonstrated a versatile capability of direct visualization in UV and daylight of enhanced LFP, as well as of primary lifts collected by gently pressing the polymeric mats on the tested surfaces. The quality of the collected LFPs images was determined mainly by the fluorophore structure, best visualization results being obtained with the phenothiazine sodium carboxylate salt. The new FEP nanomaterials appear suitable for highly accurate forensic investigations, supporting a direct analysis by photography, an expeditive and non-hazardous alternative for avoiding the disadvantages of techniques such as dusting or chemical treatment currently applied in the dactyloscopic identification of a suspect person at the crime scene.

A pillar[5]arene-based artificial light-harvesting system with red emission for high-resolution imaging of latent fingerprints

An artificial LHS with red emission based on pillar[5]arene was fabricated using 1% Nile red as the energy acceptor. The prepared powder was successfully used for high-contrast fluorescence imaging of latent fingerprints.

Perylene diimide with solid-state NIR luminescence for imaging of latent fingerprints (sweat pores)

PDI 2 showed near-IR emission at 683 nm, 99.53% red colour purity and a thick film morphology with holes for daylight and fluorescence imaging of fingerprints (levels 1–3).

Physical visualization and squalene-based scanning electrochemical microscopy imaging of latent fingerprints on PVDF membrane.

Fingerprints have long been the gold standard for personal identification in forensic science. However, realizing the high-resolution enhancement of eccrine LFPs is difficult using the traditional methods and the label-free detection of fingerprint residue information is also challenging. Herein, we propose two enhancement strategies for LFPs on PVDF membrane (LFPs/PVDF) using blue-black ink staining and scanning electrochemical microscopy (SECM). The blue-black ink staining method was used for the first time to develop three types (sebaceous, natural and eccrine) of LFPs/PVDF based on the difference in wettability between the fingerprint residues and PVDF membrane. The enhanced fingerprints clearly displayed levels 1-3 features with high contrast and low background interference. Furthermore, we achieved chemical imaging of the LFP/PVDF samples, where their possible visualization mechanisms were ascribed to the electrochemical reactivity of squalene and difference in wettability between the LFP and PVDF membrane, which was first proposed and investigated by SECM imaging and water contact angle (WCA) measurements, respectively. Significantly, SECM imaging not only provided fingerprint patterns without any labelling but also revealed the spatial distribution information of squalene in LFPs simultaneously. In addition, it was also demonstrated that LFPs deposited on various surfaces were first successfully transferred to the PVDF membrane, and then further developed with both methods, making them general for personal identity-related applications. Taken together, the blue-black ink staining method can easily and quickly obtain level 3 features of LFPs/PVDF and the SECM approach can non-invasively image the topography and chemical information of LFPs/PVDF, and thus they can be potentially selected according to various requirements in forensic scenarios.

Nanosheets of two-dimensional photoluminescent lanthanide phosphonocarboxylate frameworks decorated with free carboxylic groups for latent fingerprint imaging.

The synthesis, structural characterization, exfoliation, and photophysical studies of two-dimensional (2-D) lanthanide phosphonates, named Ln(m-pbc); [Ln(m-Hpbc)(m-H2pbc)(H2O)] (Ln = Eu, Tb; m-pbc = 3-phosphonobenzoic acid) based on the phosphonocarboxylate ligand, are reported. These compounds are neutral polymeric 2D layered structures with pendent uncoordinated carboxylic groups between layers. The nanosheets were obtained by a top-down strategy involving sonication-assisted solution exfoliation and characterized by atomic force microscopy and transmission electron microscropy, showing lateral dimensions from nano- to micro-meter scales, and thicknesses down to several layers. The photoluminescence studies demonstrate that the m-pbc ligand acts as an efficient antenna toward Eu and Tb(III) ions. The emission intensities of dimetallic compounds are clearly enhanced after incorporation of Y(III) ions due to the dilution effect. Ln(m-pbc)s were then applied for labelling latent fingerprints. It is worth noting that the reaction between active carboxylic groups and fingerprint residues benefits the labelling, showing efficient imaging for fingerprints on all kinds of material surfaces.

Pyridoxal Derived AIEgen for Fluorescence Turn-off Sensing of Cu2+ and Fe2+ Ions and Fluorescence Imaging of Latent Fingerprints.

Schiff base 4-((E)-((E)-(2-hydroxybenzylidene)hydrazono)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol (HSP) was synthesized by condensing vitamin B6 cofactor pyridoxal with salicylaldehyde hydrazone, and characterized by standard spectroscopic techniques (FT-IR, 1H NMR, 13C NMR, and ESI-MS). The solution of HSP in DMSO/HEPES (10mM, pH = 7.4) mixed solvents with varying HEPES fractions (fw) from 0 to 95% showed aggregation-induced emission (AIE). The AIE active HSP in 95% HEPES gave intense fluorescent emission at 570nm was employed for the detection of metal ions. The fluorescence of HSP was quenched upon adding Cu2+ and Fe2+ ions. The association constant (Ka) of the Schiff base HSPwith Cu2+and Fe2+ions was estimated as 4.08 × 105M-1 and 1.23 × 105M-1, respectively by using the online analysis tool BindFit v0.5. The HSP showed the detection limit down to 1.75µM and 1.89µM for Cu2+ and Fe2+ ions, respectively. Further, the aggregates of HSP were applied to visualize latent fingerprints (LFPs) over a non-porous glass slide.

Applications for data security and latent fingerprint visualization using blue-emitting surface-modified LZO:Ce3+ nanophosphor

The development of technology related to forensic is still beneficial and requires for continued research and the implementation of evaluation procedures. In this context, the current work focuses on the production of blue light emitting La2Zr2O7 nanophosphors (LZO) (NPs) doped with Ce3+ ions and surface modified with oleyl amine (OA) are employed for data security and latent fingerprint imaging applications. The formation of the pure pyrochlore phase is confirmed from powder X-ray diffraction (PXRD). The structural analysis is performed from Rietveld refinement . Scanning electron microscope (SEM) and transmission electron microscopy are used to study the surface morphology and crystallite size estimation respectively. Photoluminescence (PL) emission spectra exhibit all the characteristic emission peaks of Ce3+ ions. The surface modified NPs by OA exhibited 2-fold enhancement in the emission intensity as compared to unmodified NPs, which is due to effective intramolecular energy transfers from coordinated ligands to the activated Ce3+ ions, called the antenna effect. The most trustworthy proof of a person's identity can be found in the ridge characteristics revealed by the observed latent fingerprints employing surface modified nanophosphor. The chemical bonding between the nanophosphor and chemical components contained in the fingerprints, which enables the majority of authenticated sweat pores, further confirmed by high resolution photographs of formed latent fingerprints. The NPs which have OA grafted onto them can be made into security ink that can be used to create hidden inscriptions with a basic brush technique as well as screen print and decoded under 283 nm light illumination. The features of the NPs, which is a real-time option for latent fingerprint formation and anti-counterfeiting technologies are significantly improved by the surface modification technique .

Emerging Latent Fingerprint Imaging Technologies (Instrumental Methods)-A Review of Recent Literature

There have been tremendous scientific and technological developments in the 21st century. The field of fingerprints has also not been left untouched from the same

Early warning of Diaporthe infection in kiwifruit soft rot by plasmonic dimer-enhanced Raman spectroscopy.

Diaporthe genus is the dominant pathogens of kiwifruit soft rot with long incubation period and rapid onset and very hard to detect in advance. It is of great significance to develop point-of-care tests for disease prevention and field management. Here we screen a pair of genus-level primers for constructing plasmonic dimer Rayleigh/Raman spectroscopy, which enables rapid, specific, and sensitive detection of Diaporthe genus in real kiwifruits. Dark-filed Rayleigh scattering clearly visualizes the target-induced dimer assembly of nanoprobes. Plasmonic dimer-enhanced Raman spectroscopy has high specificity for 12 common isolates of Diaporthe genus in one batch samples with highly accurate results and much higher sensitivity than polymerase chain reaction (PCR). It realizes the recognition of Diaporthe infection at an early stage of 24h when the kiwifruits do not have any noticeable symptoms. It demonstrates a bright prospect of point-of-care tests for early warning of kiwifruit soft rot infection and quality control.

Photostable aggregation-induced emission of iridium(III) complex realizing robust and high-resolution imaging of latent fingerprints

Preparation of AIEgens with excellent photostability is of vital importance to acquire the optimal performance of aggregation-induced emission (AIE) and remains challenging. In this paper, a handy structural design strategy based on iridium(III) complexes for the creation of photostable AIEgens is reported. The synergistic effect of phenyl and carbazole improves the rotational activity of substituents, then activates the AIE property of iridium(III) complexes with considerably improved photostability. In addition, prompt and high-resolution imaging of latent fingerprints on tinfoil, glass, plastic, and steel is presented by immersion in an aqueous solution of IrCzPh for 60 s. With the aid of photostable AIE, legible and intact fingerprint images demonstrate ultrahigh definition, which can display down to level 3 of fingerprint details and accurately authenticate individual characteristics. Meanwhile, outstanding anti-aging performance of fingerprint images is emerged with no contrast attenuation under 365 nm irradiation for 60 min or aged in natural light for 7 days. Noteworthily, ultrahigh-contrast dynamic imaging of local fingerprint details is achieved.

Synthesis of D-A typed AIE luminogens in isomeric architecture and their application in latent fingerprints imaging

Among the emitters in powder dusting to visualize the latent fingerprints (LFPs), aggregation-induced emission luminogens (AIEgens) are well employed for their high brightness and resistance to photo-bleaching. However, the serious background interference and low resolution still limit their fast development. Therefore, to further enhance the signal-to-noise ratio in LFPs imaging, especially to improve the analysis for level 3 details, donor-acceptor (D-A) typed AIEgens of DTPA-2,3-P, DTPA-2,5-P and DTPA-2,6-P are designed here. It is observed that strong emission covering from 450 nm to 650 nm can be obtained for all these molecules, especially that a high PLQY value of 10.06% in solids is achieved in DTPA-2,3-P. This is much higher than that of the other two cases (0.80% and 0.51%). By utilizing the DTPA-2,3-P in powder dusting, fluorescence imaging of LFPs can be clearly captured on both smooth and rough substrates. Moreover, confocal laser scanning microscope (CLSM) enables us to achieve high-resolution LFPs imaging in both 2D and 3D views, providing more detailed information of fingerprints pores in width, distance, distribution, and shapes. The results here demonstrate that highly emissive AIEgen of DTPA-2,3-P could be an excellent candidate for the visualization of fingerprints, thus providing the potential application in criminal investigation in the future.

A multifunctional fluorescent molecule with AIE characteristics for SO2 derivatives detection, fluorescence ink and latent fingerprint imaging

With the increasing interest and demand for multifunctional fluorescence materials, a judicious and facile design is essential but still challenging. Herein, a new multifunctional fluorescence molecule (TCMn) with AIE characteristics was rationally designed and synthesized. TCMn could not only specifically recognize exogenous and endogenous SO2 derivatives (HSO3- /SO32-) in living cells, but also could be used as a fluorescent ink. The TCMn solution as a fluorescence ink exhibited excellent fluorescence stability and resistance to photobleaching. More importantly, TCMn was used for visualizing latent fingerprints on different object surfaces. This work provides a new strategy for molecular design and development of multifunctional fluorescent molecular materials for practical applications.

Instantaneous visual imaging of latent fingerprints in water

Instantaneous visual imaging of latent fingerprints in water

A single-phase white emitting nanophosphor with refined crystal structure and extremely luminescent characteristics for WLEDs and latent fingerprint detection

Rare earth (RE) elements activated luminescent phosphor materials play a critical role in optoelectronics and advanced forensic applications. For white light-emitting diodes (WLEDs) and latent fingerprints (LFPs) detection, we employed a wet chemical approach to synthesize Bi3+/Eu3+ coactivated Y2O3 single-phase white emitting nanophosphor at low temperatures. Experiments are carried out on the photoluminescence (PL) behavior of the nanophosphor as well as the qualitative and quantitative structural characterizations of two different symmetric sites of the crystal. The nanophosphor emitted blue, green, and a strong red emission bands with optimal intensity when exposed to ultraviolet (UV) radiation, resulting in white light when these three emission bands were combined. The observed PL-spectra of the Bi3+ ion is fragmented into two sub-bands occupying Bi3+(I) and Bi3+(II) sites, with stokes shifts of 2.94 × 103 cm−1 and 9.06 × 103 cm−1 respectively. The efficient energy transfer mechanism of Bi3+(I)/Bi3+(II)→Eu3+ was investigated using the PL-emission spectra. Under excitations at 326 and 342 nm, the Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates and correlated color temperature (CCTs) exhibited the tunable white color. Furthermore, the nanophosphor was utilized to observe the clear skin ridge pattern of the fingerprints under 254 UV nm light. The findings of these experiments revealed that the produced nanophosphor could be a suitable candidate for WLEDs and LFP imaging applications.

Instantaneous High‐Resolution Visual Imaging of Latent Fingerprints in Water Using Color‐Tunable AIE Pincer Complexes

Instant visualization of latent fingerprints is developed by using a series of water-soluble terpyridine zinc complexes as aggregation-induced emission probes in pure water, under UV light or ambient sunlight. By simply soaking, or spraying with an aqueous solution of the probe, bright yellow fluorescence images with high contrast and resolution are readily developed on various surfaces including tinfoil, glass, paper, steel, leather, and ceramic tile. Remarkably, latent fingerprints can be visualized within seconds including details of whorl and sweat pores. The color of emission can be tuned from blue to orange by modifying the pincer ligands, allowing direct imaging under sunlight. These inexpensive, water-resistant, and color-tunable probes provide a practical approach for latent fingerprints recording and analysis, security protection, as well as criminal investigation in different scenarios.

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

Fingerprints are important biological details and play an important role in identifying personal information. To assist the identification of latent fingerprints (LFPs) which are the frequently-met cases in practical application, LFPs are usually made visible/detectable by development (imaging) techniques. In this work, an amphiphilic probe (denoted as HNP) was designed and synthesized. Its amphiphilic nature was confirmed by its single crystal structure and lipid-water partition coefficient (P = 1.38). It showed good solubility in water and bright red AIE (aggregation-induced emission) emission upon visible light excitation (∼410 nm), which satisfied the requirements for LFPs development/imaging. Photophysical parameters (absorption spectrum, emission spectrum, and emission quantum yield), LFPs imaging performance and bio-safety of probe HNP were discussed and reported. It was found that HNP showed efficient AIE effect in aggregated state. After meeting the lipids in LFPs, HNP AIE effect was activated, showing emission “turn-on” phenomenon and LFPs pattern. This mechanism was confirmed by micromorphology analysis. Corresponding dynamics were discussed as well. Good stability and durability were observed for HNP development/imaging. Details down to level 3 were successfully retrieved with high contrast.

Highly emissive dimethylamino naphthalenyl phenylethene derivatives for visualization of latent fingerprints and imaging of lysosomes

Organic fluorescent materials have been widely used in various fields including visualization of latent fingerprints and imaging of lysosomes. High-performance organic fluorescent molecules based on simple molecular structures are still limited and highly demanded for high-definition and high-contrast imaging of latent fingerprints and lysosomes. In this work, two organic fluorescent molecules (DANPAN and DANBEN) were developed based on dimethylamino naphthalenyl phenylethene structure. These two molecules have quite different fluorescent properties, and the position of cyano group significantly affects the optical properties of these dimethylamino naphthalenyl phenylethene derivatives. Compound DANPAN shows strong yellow emission in solid state, while compound DANBEN has strong fluorescent emission in organic solutions. In addition to these differences, both compounds have large Stokes shifts and positive solvatochromic properties. Further studies showed that these compounds could be used to display latent fingerprints on various substrate surfaces. The obtained fingerprint images have excellent contrast and high resolution. It is also found that these molecules could specifically stain lysosomes in living cell within short incubation time. This work provides a series of new high-performance organic fluorescent materials with diverse applications.

Time-Gated Imaging of Latent Fingerprints with Level 3 Details Achieved by Persistent Luminescent Fluoride Nanoparticles.

The discovery of X-ray-charged persistent luminescence (PersL) in fluoride nanoparticles enables these materials to emit photons without real-time excitation, which provides a great possibility for the development of new luminescent nanotechnologies. In this work, we developed NaLuF4:Mn nanoparticles with intense green PersL and functionalized surfaces and accordingly achieved time-gated imaging of latent fingerprints (LFPs) with Level 3 details. These surface-modified NaLuF4:Mn nanoparticles exhibited near-spherical morphology, long-lasting emission for several hours, appropriate trap depth distribution, and tight chemical bonding with amino acids from fingerprints, thus greatly improving the accuracy of LFP imaging in a variety of environments. The developed NaLuF4:Mn PersL nanoparticles are expected to find broad applications in the fields of LFP imaging and in vivo biological imaging.

Self-quenching-resistant fluorescent tunable sulfur quantum dots

Fluorescence-tunable sulfur quantum dots (SQDs) were obtained by an assembly-fission process and assisted etching with H2O2. The morphological and structural characterization indicated that the obtained SQDs possess excellent dispersion, high water solubility and abundant surface functional groups, which is beneficial to its further application. In the Gaussian software, the electron cloud density distribution around the entire molecular structure is simulated and the density generalization calculations confirms that the main reason for the red shift of emission is the synergistic effect of SQDs size and surface states. Moreover, blue fluorescent SQDs (B-SQDs) showed high sensitivity and specific selectivity toward berberine hydrochloride with detection limits as low as 0.24 nM, and have been successfully used for water sample and actual drug detection. It is noteworthy that the solid-state luminescence properties of SQDs are mainly attributed to the adsorption of chain PEG on the surface of SQDs. By mixing SQDs with epoxy resin, dual-color fluorescent films were prepared and used as the fluorescence conversion layer to manufacture high-performance light-emitting diodes. The CIE (Commission Internationale d′Eclairage) coordinates of WLED is (0.27,0.29), CCT (Correlated color temperature) is 5793 K and CRI (Color rendering index) is 85.2. Moreover, the prepared SQDs are highly fluorescent and enable latent fingerprint imaging for identity recognition. This work has advanced the development of SQDs for analytical sensing, optical devices, and fingerprint imaging.

Aptamer functionalization and high-contrast reversible dual-color photoswitching fluorescence of polymeric nanoparticles for latent fingerprints imaging

Exploiting the intelligent stimuli-responsive fluorescent materials, which can selectively recognize lysozyme in fingerprints and enable high-contrast imaging, is still a challenge in latent fingerprints (LFPs) detection. Herein, based on Fluorescence Resonance Energy Transfer (FRET) mechanism, aptamer functionalization and high-contrast reversible dual-color photoswitching fluorescence of polymeric nanoparticles (LBA-RPFPNs) have been successfully constructed for efficient imaging of LFPs. Experiments results showed that LBA-RPFPNs displayed good water dispersibility, fast photo-responsiveness, favorable photoreversibility and good long-term stability. Of note, the aptamer possessed the ability of LBA-RPFPNs to target lysozyme in LFPs, thus realizing the selectivity of LFPs. Furthermore, the fluorescence of LBA-RPFPNs was reversibly switched between green and red through UV/visible light, achieving for high-contrast imaging of LFPs. This strategy provides good potential in disclosing the valuable information within LFPs.