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 photobleaching.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 450nm to 650nm 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.

High-Resolution Imaging of Latent Fingerprints through Near-Infrared Organoboron AIEgens

A new class of near-infrared(NIR)fluorescent organoboron AIEgens was successfully developed for latent fingerprints(LFPs)imaging.They exhibit real-time and in situ high-resolution imaging performance at 1-3 levels of LFPs by spraying method.In addition,we systematically elucidate the fingerprint imaging mechanism of these AIEgens.Significantly,the excellent level 3 structural imaging capabilities enable the application of them for analyzing incomplete LFPs and identifying individuals in different scenarios.

Advances in the development and component recognition of latent fingerprints

Fingerprints have been used as an indispensable tool for personal identification in forensic investigations since the late 19 th century. At present, fingerprinting technology has moved away from its forensic roots and is incorporating a broader scientific range, e.g., material science, spectroscopy and spectral analysis, and even in vitro diagnosis. After a brief introduction to latent fingerprints, this mini-review presents the pioneering progresses of fingerprinting technologies including(i) material and electrochemical techniques, and(ii) spectral and spectroscopy imaging techniques and immunological techniques capable of both the visualization of a fingerprint and the detection of chemicals present in it. Finally, perspectives on this rapidly developing field are discussed.

Simultaneous extraction of level 2 and level 3 characteristics from latent fingerprints imaged with quantum dots for improved fingerprint analysis

Fingerprints are unique and life-long to everyone, so they occupy very important statuses in forensic science. However, due to the limit of current imaging technologies and instruments, recognition and matching of fingerprints are mostly based on their level 2 structures（bifurcation, crossover, and etc.）.Moreover, in real-world cases, fingerprints collected in the field are often incomplete or damaged, which adds further difficulty in fingerprint analysis. Quantum dots（QDs） are superior fluorescent imaging agents for latent fingerprints, which can provide both level 2 and level 3（sweat pores） details. Here, we used red-emitting N-acetylcysteine-capped Cd Te QDs as imaging agent for staining of eccrine LFPs. The numbers of level 2 and level 3 features that can be mapped are significantly larger than those obtained by cyanoacrylate fuming, a standard technique being adopted at forensic scene. Therefore, the level 2 and level 3 characteristics from QD-staining were simultaneously extracted for improved fingerprint analysis.A preliminary fingerprint matching based modified Pore Matching algorithm was thus developed based on the integration of both level 2 and level 3 characteristics. Satisfactory results of fingerprint matching were obtained, demonstrating the advantage of the QD-staining for advanced fingerprint analysis.

Blue light-induced rare-earth free phosphors for the highly sensitive and selective imaging of latent fingerprints based on enhanced hydrophobic interaction

The demand for in-situ detection of latent fingerprints(LFPs)in ways of high sensitivity,high selectivity,high contrast,low cost and user-friendly is still urgent.To overcome this challenge,a moisture-stable,red-emitting fluoride phosphor K_(3)AlF_(6):Mn^(4+)(KAF:Mn^(4+))with an organic hydrophobic skin was prepared.The phosphor has a uniform and superfine morphology with excellent luminescence properties.More importantly,this non-ultraviolet(UV)or non-near infrared(NIR)induced phosphor was proved to be an ideal fluorescent label for LFP imaging,which is both friendly for touch DNA analysis and compatible to forensic light sources.The well-defined ridge details with little background interference on various surfaces were presented by the oleic acid(OA)modified KAF:Mn^(4+)(KAF:Mn^(4+)-OA)phosphor in few seconds using the powder dusting method.To confirm the high selectivity of KAF:Mn^(4+)-OA for LFP imaging,an efficient quantitative evaluation method is proposed with the aid of ImageJ&Origin software.Due to the superiority of the Mn^(4+)-doped fluoride for the rapid imaging of LFPs in terms of lowcost,high compatibility and good availability,it is expected to be a promising candidate for forensic science as well as fluorescence imaging in other fields instead of rare earth luminescent materials.

Versatile core-shell magnetic fluorescent mesoporous microspheres for multilevel latent fingerprints magneto-optic information recognition

Latent fingerprints are extremely vital for personal identification and criminalinvestigation,and potential information recognition techniques have been widelyused in the fields of information and communication electronics.Although physicalpowder dusting methods have been frequently employed to develop latent fingerprintsand most of them are carried out by using single component powders ofmicron-sized fluorescent particles,magnetic powders,or metal particles,there isstill an enormous challenge in producing high-resolution image of latent fingerprintsat different backgrounds or substrates.Herein,a novel and effectivenanoimpregnation method is developed to synthesize bifunctional magnetic fluorescentmesoporous microspheres for latent fingerprints visualization by growthof mesoporous silica(mesoSiO_(2))on magical Fe_(3)O_(4) core and then deposition offluorescent YVO4:Eu^(3+)nanoparticles in the mesopores.The obtainedFe_(3)O_(4)@mesoSiO_(2)@YVO4:Eu^(3+)microspheres possess spatially isolated magneticcore and fluorescent shell which were insulated by mesoporous silica layer.Dueto their small particle size of submicrometer scale,high magnetization and lowmagnetic remanence as well as the combined magnetic and fluorescent properties,the microspheres show superior performance in visual latent fingerprint recognitionwith high contrast,high anti-interference,and sensitivity as well as goodretention on multifarious substrates regardless of surface permeability,roughness,refraction,colorfulness,and background fluorescence interference,and it makesthem ideal candidates for practical application in fingerprint visualization andeven magneto-optic information storage.

Detection of latent fingerprints using luminescent Gd_(0.95)Eu_(0.05)PO_(4) nanorods

Lanthanide ions doped luminescent materials are widely studied for latent fingerprint detection.However,most of these materials are synthesized at very high temperatures and use UV C light for visualization,which is harmful to eye,skin,etc.Herein,the Gd_(0.95)Eu_(0.05)PO_(4) nanorods synthesized by a simple co-precipitation method at 185℃ were reported for latent fingerprint visualization under 395 nm light.The Gd_(0.95)Eu_(0.05)PO_(4) nanomaterial has monoclinic crystal structure and shows rod-shaped morphology.Further,these Gd_(0.95)Eu_(0.05)PO_(4) nanorods exhibit excellent photoluminescence properties and strong fuchsia emission under UV light.These nanorods have been employed for developing latent fingerprints on various porous and non-porous substrates by the powder dusting technique,which exhibits clear and well defined details with high contrast,selectivity and sensitivity under 395 nm UV light.Latent fingerprints developed after 72 h of their deposition also show clear contrast with these nanorods.Therefore,the Gd_(0.95)Eu_(0.05)PO_(4) nanorods can be used for latent fingerprint visualization applications.

A Study on Automatic Latent Fingerprint Identification System

Latent fingerprints are the unintentional impressions found at the crime scenes and are considered crucial evidence in criminal identification.Law enforcement and forensic agencies have been using latent fingerprints as testimony in courts.However,since the latent fingerprints are accidentally leftover on different surfaces,the lifted prints look inferior.Therefore,a tremendous amount of research is being carried out in automatic latent fingerprint identification to improve the overall fingerprint recognition performance.As a result,there is an ever-growing demand to develop reliable and robust systems.In this regard,we present a comprehensive literature review of the existing methods utilized in latent fingerprint acquisition,segmentation,quality assessment,enhancement,feature extraction,and matching steps.Later,we provide insight into different benchmark latent datasets available to perform research in this area.Our study highlights various research challenges and gaps by performing detailed analysis on the existing state-of-the-art segmentation,enhancement,extraction,and matching approaches to strengthen the research.

Eu-MOF-Based Fluorescent Ratiometric Sensor by Detecting 3,4,5-Trihydroxybenzoic for Fingerprint Visualization on Porous Objects

Latent fingerprints(LFPs)at the crime scene are served as important clues to locate the trajectory of criminal behavior and portray the characteristics of the suspect.Therefore,visualizing LFPs is of considerable significance.In this work,the europium metal-organic framework(Eu-MOF)sensor was successfully constructed for sensitive detection of gallic acid(3,4,5-trihydroxybenzoic acid,GA)and visualization of the sweat LFPs.The boric-acid-modified Eu-MOF was prepared by using the simple one-pot solvothermal method using Eu as the metal i ion center and 3,5-dicarboxybenzeneboronic acid(BBDC)as the organic ligand.The sensor showed desirable photoluminescent performance through the chelating of BBDC with Eu3+.The sensor exhibited the satisfactory linear relationship to GA in the range of 1 nM to 20 nM with a low detection limit of 0.34 nM under the optimized conditions.The prepared sensor with ideal selectivity to GA was successfully applied for visualizing LFPs on porous substrates with the high contrast and superior stability.Given the good performance of the sensor,all fingerprint images obtained from 1200 samples presented clear friction ridges and met the identification criteria.Notably,the sensor had less impact on the subsequent deoxyribonucleic acid(DNA)detection,displaying a promising perspective for applications in extracting physical evidence of site investigation.

Exploring the Potential of Syzygium cumini(L.)Skeels(Jamun)Seed Powder as an Eco-Friendly Agent for Developing Friction Ridges on Porous and Nonporous Surfaces

Background:Development of obscured fingerprints on a diverse range of surfaces is a crucial aspect of forensic investigations.Aims and Objectives:In this particular study,the utilization of Syzygium cumini(L.)Skeels(Jamun)seed powder was examined for the purpose of revealing hidden fingerprints on a variety of surfaces,including both permeable and impermeable substrates.Materials and Methods:The seed powder was extracted using a simple process and was analysed using multiple analytical techniques.The efficacy of the jamun seed powder in developing latent fingerprints was evaluated.Results:The findings of this investigation demonstrate that the jamun seed powder was capable of producing fingerprint patterns of exceptional quality and clarity on numerous surfaces.Conclusion:This research highlights the potential use of jamun seed powder as a practical and effective alternative for the development of hidden fingerprints in forensic investigations,while also providing cost-effectiveness.

Recent progress in background-free latent fingerprint imaging

Owing to their unique pattern and abundant chemical composition, latent fingerprints （LFPs） can serve as ＂ID cards＂ and ＂information banks＂ of donors and therefore are valuable for forensic investigation, access control, and even medical diagnosis. LFP imaging has attracted considerable attention, and a great variety of contrast agents has been developed. In LFP imaging, background signals such as background fluorescence from the underlying surface can seriously blur the LFP images and decrease imaging sensitivity; thus, great efforts have been made to eliminate background interference. Here, we stratify the recent progress in background-free LFP imaging by making use of the difference in properties between contrast agents and background compounds. For example, near-infrared （NIR） light-activatable contrast agents can efficiently remove background signals in LFP imaging because the background compounds cannot be excited by NIR light, showing that the difference in excitation properties between contrast agents and background compounds can be employed to eliminate background interference. This review is organized around background-free LFP imaging based on the difference in optical properties between contrast agents and background compounds： （i） different excitation wavelengths, （ii） different emission wavelengths, （iii） different luminescence lifetime values, （iv） different plasmonic properties, （v） different photothermal properties, and （vi） different electrochemiluminescence properties.

Effects of storage time on DNA profiling success from archived latent fingerprint samples using an optimised workflow

Due to recent improvements in forensic DNA testing kit sensitivity,there has been an increased demand in the criminal justice community to revisit past convictions or cold cases.Some of these cases have little biological evidence other than touch DNA in the form of archived latent fingerprint lift cards.In this study,a previously developed optimised workflow for this sample type was tested on aged fingerprints to determine if improved short tandem repeat(STR)profiles could be obtained.Two-year-old samples processed with the optimised workflow produced an average of approximately five more STR alleles per profile over the traditional method.The optimised workflow also produced detectable alleles in samples aged out to 28 years.Of the methods tested,the optimised workflow resulted in the most informative profiles from evidence samples more representative of the forensic need.This workflow is recommended for use with archived latent fingerprint samples,regardless of the archival time.

A general powder dusting method for latent fingerprint development based on AIEgens

Powder dusting method is the most practically useful approach for latent fingerprint development in the crime scene. Herein, a general powder dusting method has been explored for latent fingerprint development based on aggregation-induced emission luminogens(AIEgens). A series of tetraphenylethene(TPE) derivatives with multiple diphenylamine(DPA), namely, TPE-DPA,TPE-2 DPA and TPE-4 DPA, were selected as candidates to dope with magnetic powders and applied for latent fingerprint development. After screening, the magnetic powder 3 doped with TPE-4 DPA proves to be the best, in terms of fluorescent intensity, resolution and adhesiveness. Afterwards, the magnetic powder 3 was applied for visualization of latent fingerprint on various smooth and porous substrates, including glass, stainless steel, leaf, ceram, plastic bag, lime wall, wood and paper money.Specific details, such as island, core, termination and bifurcation, can be clearly observed for the fluorescent fingerprint images.

Latent fingerprint enhancement on conductive substrates using electrodeposition of copper

We presented a novel method for the development of a latent fingerprint by selective electrodeposition of a copper thin film from sulfate solution onto the conductive substrate between fingerprint ridges to generate a negative image of the fingerprint deposit. After optimizing the parameters(deposition time, deposition potential, and copper concentration), the preferential electrodeposition of copper films allowed latent fingerprints on six kinds of conductive surfaces(indium/tin oxide-coated glass, silver sheet, platinum sheet, gold sheet, copper sheet, and a stainless steel coin) to be successfully developed with high resolution. In addition, this technique could also be exploited to visualize latent fingerprints on rough and dirty surfaces. The quality of the developed fingerprints was estimated visually and the morphology of the copper film was characterized by field emission scanning electron microscopy.

Green mediated synthesis of lanthanum doped zinc oxide:Study of its structural,optical and latent fingerprint application

The present paper summarises the synthesis of La3+doped zinc oxide nanoparticles using Aloe vera gel by solution combustion method and the characterization using a powder X-ray diffractometer(PXRD),a transmission electron microscope(TEM),an X-ray photometric spectrometer(XPS),a Raman spectrometer and their applications in optical devices and latent fingerprinting.PXRD pattern confirms the crystallite size of La3+doped ZnO varies from 13 to 20 nm.Crystallite size varies inversely with doping concentration.Photoluminescence properties are found to be the maximum for 2 mol% doping concentration.PL spectra extends the use of ZnO:La3+nanoparticles in blue green LED.These nanoparticles also have superior property as a fluorescent labels in fingerprints.

A dual-stimuli-responsive intelligent layered lanthanide hydroxide for application in information security and latent fingerprint identification

With the rapid changes in the field of information,the research and development of optical storage materials with high security and large storage capacity are particularly important in the development of contemporary society.However,conventional memo ry materials with static fluorescent outputs have the disadvantages of easy simulation and forgery,which limits their practical application in the protection of confidential information.In this research,a dual-stimuli-responsive intelligent fluorescent material based on Tb^(3+)and Eu^(3+)ions doped layered lanthanide hydroxide(LYH:Eu_(x)Tb_(1-x)DPA)was fabricated,which can realize reversible multi-color luminescence conversion(from green to red)by varying the pH and temperature.Combined with the Morse code and security pattern,the multiple encryption and decryption of confidential information and anti-counterfeiting can also be realized.Therefore,the obtained intelligent fluorescent material has a great application prospect for information security.In addition,due to the excellent color tunability,the material can provide the possibility to obtain potential fingerprints with high contrast and no background interference on different color substrates.The unique dual-stimuli-responsive behavior of this material provides more ingenious design inspiration for the design of multi-color intelligent fluorescent devices.

Plasmonic polydopamine-modified TiO_(2)nanotube substrates for surface-assisted laser desorption/ionization mass spectrometry imaging

Mass spectrometry imaging(MSI)has made the spatio-chemical characterization of a broad range of small-molecule metabolites within biological tissues possible.However,available matrix-assisted laser desorption/ionization mass spectrometry(MALDI-MS)suffers from severe background interferences in low-mass ranges and inhomogeneous matrix deposition.Thus,surface-assisted LDI-MS(SALDI-MS)has been an attractive alternative for high-sensitivity detection and imaging of small biomolecules.In this study,we construct a new composite substrate,hydrophobic polydopamine(hPDA)-modified TiO_(2)nanotube(TDNT)coated with plasmonic gold nanoparticle(AuNP-hPDA-TDNT),as a dual-polarity SALDI substrate using an easy and cost-effective fabrication approach.Benefitting from the synergistic effects of TDNT semiconductor and plasmonic PDA modification,this SALDI substrate exhibits superior performance for dual-polarity detection of a vast diversity of small molecules.Highly reduced background interferences,lower detection limits,and spot-to-spot repeatability can be achieved using AuNP-hPDA-TDNT substrates.Due to its unique imprinting performance,various metabolites and lipids can be visualized within jatropha integerrima petals,ginkgo leaves,strawberry fruits,and latent fingerprints.More valuably,the universality of this matrix-free substrate is demonstrated for mapping spatial distribution of lipids within mouse brain tissue sections.Considered together,this AuNP-hPDA-TDNT material is expected to be a promising SALDI substrate in various fields,especially in nanomaterial development and life sciences.

Flux blended synthesis of novel Y2O3：Eu^3＋ sensing arrays for highly sensitive dual mode detection of LFPs on versatile surfaces

In the present communication,various fluxes blended Y2 O3：Eu3＋（5 mol%） nanopowders（NPs） were successfully fabricated by solution combustion method.PXRD pattern confirms body-centered cubic structure of the prepared samples.Energy band gap（Eg） of the fabricated products was estimated and is found to be in the range of 3.13-3.32 eV.Photoluminescence（PL） emission spectra exhibit sharp and intense peaks at ～579,592,614,657,704 nm corresponding to 5 D0→7 FJ（J = 0,1,2,3 and 4） transitions of Eu3＋ ions.Significance of fluxes for enhancing the PL emissions was extensively studied.Photometric studies of the prepared samples are located in pure red region.Optimized NPs were explored as a novel sensing agent for visualization of latent fingerprints（LFPs） on various surfaces including porous,semiporous and non-porous surfaces followed by powder dusting technique.Various experiments including aging,temperature,scratching and aquatic fresh water treatment tests were performed to evaluate applicability of the fabricated NPs.Visualized LFPs exhibit well defined ridge details including most authenticated sweat pores are also revealed with high sensitivity,selectivity,little background hindrance and less toxicity.Aforementioned results evidence that the method and fabricated NPs can be considered to be simple,rapid and economical and provide novel sensing platform for LFPs visualization in prospective forensic applications.

Natural interface-mediated self-assembly of graphene-isolatednanocrystals for plasmonic arrays construction and personalized information acquisition

As Interface mediated self-assembly of nanocrystals provide excellent strategy for sensing,catalysis or photonics,the construction of innovative interfaces and development of versatile strategies for nanocrystal synthesis are urgently needed.Herein,latent fingerprints(LFPs),the most common markers for human identity,are used as naturally accessible interface for organization of graphene isolated nanocrystals(GINs).Excitingly,the selective adsorption of GINs on lipidic ridge provides a universal approach for the in-situ construction of the plasmonic arrays.Such system with intrinsic chrominance and Raman signal enables the high resolution colorimetric and surfaced-enhanced Raman spectroscopy(SERS)dual-mode imaging,which can detail the structures of the LFPs from 1st to 3rd level even the LFPs are shielded.Furthermore,the interface can be constructed on diverse materials by a simple finger-pressing process and the densely packed arrays can serve as superior SERS substrate for label-free,non-invasive acquisition of molecule information especially residues in LFPs.The combination of chemical composition with detailed structures efficiently recognizes the human identity and could help link it to a crime scene.Overall,the LFPs can act as natural platform for interface mediated localized assembly and personalized information acquisition for forensic science or precise medicine.