Fingerprint Detection Research Articles

Citric acid assisted synthesis of luminescent CeF3 and CeF3:Tb3+ nanoparticles: Luminescent &optical properties

Luminescent CeF3 and CeF3:Tb3+ nanoparticles (NPs) were synthesized by citric acid-supported wet chemical method at a lower temperature. X-ray diffraction (XRD) pattern was recorded to examine the crystal structure, particle size, and phase pureness of the nano-products. The shape and size of the as-synthesized nanoproduct were reviewed by transmission electron microscopy (TEM). The development of a hexagonal phase solid solution at the nanoscale by the successful incorporation of Tb3+ ion into the CeF3 crystal lattice was confirmed by the XRD data. The solid solutions of nanocrystalline CeF3:Tb3+ NPs were confirmed by the TEM micrographs. Highly aqueous dispersible, agglomerated, typical porous surface, irregularly spherical shaped, well distributed polycrystalline particles were observed in TEM photographs. The development of a partially transparent colloidal solution with good colloidal stability in the aqueous media was indicated by the examination of optical characteristics. Based on absorption spectral analyses, the occurrence of structural imperfections and their impact on the bandgap energy was explored. The photoluminescence spectrum of the CeF3:Tb NPs was measured to authenticate the successful insertion of Tb3+-ion into the CeF3 crystal matrix. CeF3:Tb NPs exhibit a prominent green color due to a dominant magnetic-dipole (5D4→7F5) emission transition that is visible in the middle of the spectrum at 543 nm on irradiation from a UV light source. The sharp excitation and intense emission transitions astounding luminescence efficiencies indicated that the luminescent NPs are very crystalline. The as-prepared CeF3:Tb NPs have prospective uses in laser-based biological events including fingermark detection, security ink, and bio-tagging agents due to their superior luminescent and optical properties.

Gait Recognition Using Convolutional Neural Network

Biometrics are the body measurements and calculations related to individuals. Biometrics validation is used as a form of identification of individual. Gait recognition system is one of the most advanced technology that people have been working on for a while now that takes center stage in the field of biometrics. Compared to the other types of existing systems of biometric recognition such as fingerprint detection, iris-scanning systems etc., Gait Recognition system ensures no human intervention. This paper focuses on recognition based on a person’s gait. Every person has a distinct gait pattern that is unique to every other person. To train the model CASIA-B dataset has been used. The dataset includes 124 subjects where each sample has undergone Gait Energy Image extraction. Samples with clothing and baggage have been included which changes the silhouette of the person. Therefore, the model has been trained for a wider application where people wear different type of clothing and carry-ons. A Convolutional Neural Network consisting of 8 layers has been trained which performs well on both samples of dataset and an accuracy of 95.45% was obtained on dataset not involving layers of clothing and accuracy of 91.80% was obtained for the sample with clothing and baggage.

Designing orange-red emitting luminescent platform for data security and information encryption based Sm3+ doped BLAO phosphor

Due to the features of great difference and invariability, latent fingerprint (LFP) and lip print (LP) detection has grown to be a vital part of criminal investigation. Due to its environmental friendliness, powder dusting is now the method of choice for visualizing LFPs. The uses of this technology are severely constrained by essential flaws like limited resolution, low sensitivity, and high background interference. To address these issues, a novel orange red emitting BaLaAlO4:Sm3+ (1–5 mol %) (BLAO:Sm) phosphor has been fabricated via solution combustion route. The 4G5/2 → 6H7/2 transition of Sm3+ ions caused the phosphor to generate intense orange-red light at 601 nm under stimulation at 402 nm. The optimal Sm3+ concentration in BLAO is 2 mol % (BLAO:2Sm). The International Commission on Illumination evaluated the colour coordinates (CC), correlated colour temperature (CCT), and colour purity (CP) values based on the photoluminescence emission (PLE) profiles. The acquired CC and the typical National Television System Committee (NTSC) coordinates are compared. Additionally, the usefulness of the phosphor is assessed for the powder dusting technique to detect fingerprints (FPs) on various surfaces. The level 1–3 structure of LFPs and the distinct features of lip prints (LPs) are clearly visible utilizing the BLAO:2Sm phosphor under 402 nm, UV illumination. Fluorescent phosphor is fabricated with the necessary thickening agent in order to create AC inks that mark on various surfaces with high resolution without spreading and tracing. When exposed to UV light, the above ink's drawn design instantly developed and is illuminated with vivid orange red fluorescence emission. The results revealed that the optimized phosphor can garner significant interest for use in personal identification, and security encoding.

Detection of fingerprints on moist crime evidence: A students’ activity

It may be asserted that there is no more effective deterrent to crime than the certainty of detection. Equally true is that there is no surer way to establishing identity than by fingerprints. The detection of fingerprints at the scene of crime is therefore one of the most powerful tools available in casework investigations. However, if the crime evidence is deliberately or accidentally exposed to water, the fingerprints get washed out and cannot be detected by conventional techniques. In this communication, we describe a simple experiment that enables the visualization of fingerprints on moist items.

Realization of Achromatic and Wide-Field Doublet Metalens in Mid-Infrared Spectra

Metalenses has been proposed to replace bulky and heavy refractive lenses. In the mid-infrared (MIR) range, simultaneous realization of wide-field and achromatic imaging for MIR metalense has so far not been achieved. In this letter, we design and fabricate a MIR metalens that achieves achromatic imaging with a field of view (FOV) of 60° in the wavelength range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10~\mu \text{m}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11~\mu \text{m}$ </tex-math></inline-formula> . Experimental results show that the average focusing efficiencies of the metalens are 20.62% at 0° incident angle and 9.1% at 30° incident angle. This metalens provides potential in many applications, such as molecular fingerprint detection, night vision and free space communication.

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.

Ultralong Room-Temperature Phosphorescence of Boron Carbon Oxynitride Nanodots Encapsulated in Pyrophosphate in Dry and Wet States for Fingerprint Detection and Information Protection

Room-temperature phosphorescence (RTP) materials have attracted wide interest due to their long lifetime and free from background autofluorescence. Nevertheless, simultaneous activation of stable long-lived RTP emission in both solid and aqueous phases remains a tremendous challenge. Herein, a molten salt method to synthesize boron carbon oxynitride nanodot-based RTP composites (BCNO nanodots@pyrophosphate) was carried out by employing pyrophosphate as the inert shell for BCNO nanodots. The BCNO nanodots@pyrophosphate1 with the average size of 3.69 nm show bright-green RTP because the introduction of phosphorus is beneficial to the intersystem crossing process and increases the RTP emission. What is more, whether in solid or aqueous dispersion, BCNO nanodots@pyrophosphate1 retains good phosphorescent properties with a high phosphorescence quantum yield (29.5% and 18.6%) and a long lifetime (1.39 and 1.29 s), which lasts over 15 s to the naked eye. This is the first report on BCNO nanodots with RTP in aqueous solution. The unique RTP characteristics allow BCNO nanodots@pyrophosphate as a hopeful indicator for detection of latent fingerprints with high contrast and multilevel information protection.

Preparation, characterization, and application of a red phosphor Ca2InTaO6:Eu3+ in w-LEDs and latent fingerprint detection

Eu3+-doped Ca2InTaO6 phosphors were synthesized by a high-temperature solid-state reaction. Their crystal structure, composition, phase purity, photoluminescence (PL) properties, and thermal quenching mechanism were investigated in this experiment. The band gap of Ca2InTaO6 (3.87 eV) classifies it as an indirect band gap material. X-ray diffraction results confirm the good phase purity of the synthesized material has good phase purity. The Ca2InTaO6 lattice has an orthorhombic structure, which includes the Pnma(No. 62) space group. After being excited at 395 nm, Ca2InTaO6:0.40Eu3+ phosphor showed a red emission peak at 613 nm (5D0→7F2 transition). The optimal doping concentration of Ca2InTaO6:xEu3+ phosphor is x = 0.40. Moreover, Ca2InTaO6:0.40Eu3+ phosphor has a color purity of 99.9%, an internal quantum efficiency (IQE) of up to 90.69% and a thermal activation energy (Ea) of 0.36 eV. The prepared white light-emitting diode (w-LED) possesses satisfactory color rendering index (Ra = 88.3), correlation color temperature (CCT = 5748 K), and Commission International de L′Eclairage (CIE) coordinates (0.327, 0.339). The levelsⅠ-Ⅲ characteristics of the latent fingerprint (LFP) created by Ca2InTaO6:Eu3+ phosphor can also be clearly reflected. These experimental results show that Ca2InTaO6:Eu3+ phosphor can be applied in w-LED production and LFP detection.

Fluorophores-rich natural powder from selected medicinal plants for detection latent fingerprints and cyanide.

Forensic science is currently fast-growing for the development detection of the latent fingerprint. Currently, chemical dust quickly enters the body through touch or inhalation and will be affected by the user. In this research, a study on the comparison of natural powder from four species of medicinal plants (Zingiber montanum, Solanum Indicum L., Rhinacanthus nasutus, and Euphorbia tirucall) for the detection of latent fingerprints is carried out that has fewer adverse effects on the user's body by using such natural substances instead. In addition, the fluorescence properties of the dust have been found in some natural powder for sample detection and appear on multi-colored surfaces to show that the latent fingerprints are more pronounced than ordinary dust. In this study, medicinal plants have also been applied to detect cyanide, as it has been known that it is hazardous for humans and can be used as a poisonous compound to kill someone. The characteristics of each powder have also been analyzed using naked-eye detection under UV light, Fluorescence spectrophotometer, FIB-SEM, and FTIR. All the powder obtained can then be used for high potential detection of latent fingerprints on the non-porous surface with their specific characteristics and trace amounts of cyanide using turn-on-off fluorescent sensing method.

Synthesis and upconversion emission studies of CaYF5:Ho3+/Yb3+ phosphor and its applications in optical thermometry, fingerprint detection, and security ink.

In this work, a CaYF5:Ho3+/Yb3+ upconversion phosphor was synthesized and its structural, morphological, and optical properties were studied. The upconversion emission study was performed at an excitation pump power density of 5 W cm-2 and emissions at 544 nm, 650 nm and 747 nm due to the 5F4(5S2) → 5I8, 5F5 → 5I8 and 5F4(5S2) → 5I7 transitions of the Ho3+ ion, respectively were observed. From temperature-dependent upconversion spectra temperature sensitivity was calculated and sensitivity is found to be 14 × 10-3 K-1 for the synthesized upconversion phosphor. The photothermal conversion efficiency of the prepared sample in ethanol medium was tested. Moreover, the sample was used to develop latent fingerprints on various surfaces and good contrast in recorded images is observed. The invisible ink was prepared using the upconversion phosphor and then written words were recorded in upconversion emission mode.

Label-free SERS ultrasensitive and universal detection of low back pain fingerprint based on SERS substrate.

Low back pain (LBP) seriously endangers human health and quality of life, and the detection of thoracolumbar fasciitis (TLF) is vital for the prevention and treatment of LBP. Surface-enhanced Raman scattering (SERS) is considered as a powerful technique for fingerprint detection due to the inherent richness of the spectral data. In this work, a novel SERS strategy based on a three-dimensional substrate was developed for fingerprint analysis for early diagnosis of TLF. A rat TLF model was established and the model was evaluated from the immunological and behavioral perspectives. Vibrational fingerprints were obtained by SERS testing of isolated fascial tissue and were used to explore the material changes during fasciitis. SERS spectra were analyzed using principal component analysis (PCA) that allowed unambiguous distinction and monitoring of component changes during TLF. Furthermore, in order to further clarify the occurrence and development of TLF, we combined clinical samples for analysis, and investigated the inflammatory factor expression levels of CRP and SAA in TLF. Our results demonstrated that tryptophan, phenylalanine and glycogen could unambiguously distinguish TLF as confirmed by SERS analysis, a method that is capable of noninvasive characterization of and diagnosis of TLF during LBP. We have provided a new tool that may promote in-depth study of the mechanism and treatment of fasciitis.

Enhancement of photoacoustic and upconversion emission in Mg2+/Zn2+ codoped Gd2O3: Er3+/Yb3+ phosphor using 980 nm excitation.

In this work, Er3+/Yb3+ doped Gd2O3 phosphor samples were synthesized through a combustion method and then characterized through X-ray diffraction and FE-SEM techniques. The sample was studied for photoacoustic spectroscopy (PAS) and upconversion (UC) emission spectroscopy techniques using a frequency modulated 980 nm excitation source. A correlation between PA signal (produced due to non-radiative transitions) and UC emission intensity (produced due to radiative transition) is made in order to optimize the sample for both these properties. The phosphor was codoped with Mg2+ and Zn2+ ions to see enhancement in upconversion emission intensity and these ions have enhanced the upconversion emission. Studies show that the present phosphor is appropriate for producing strong upconversion emission intensity along with a strong photoacoustic signal which is beneficial for upconversion-imaging as well as photothermal therapy. The present sample has also shown its potential for detection of fingerprints.

Annealing-assisted optimization for persistency of afterglow of SrAl2O4:Eu2+/Dy3+ microparticles for forensic detection.

In the present work, Eu2+/Dy3+ ions doped/co-doped into persistent SrAl2O4 microparticles have been developed through solid-state synthesis followed by homogenization and particle size reduction in a ball milling device. These particles have shown a broad and long-persistent afterglow around the 528 nm wavelength of electromagnetic radiation through a broad excitation at around 400 nm. The luminescence intensity was optimized through the selection of different annealing temperatures in the range of 1100 °C to 1500 °C, with intervals of 100 °C. Several structural and optical characterization techniques, such as XRD, SEM, FTIR, thermogravimetric analysis, and photoluminescence, were utilized to judge the preparation and ability of these particles in possible applications in latent fingermark detection on various difficult surfaces. The persistency and stability of these particles were calculated using a digital lux meter.

Boosting the terahertz absorption spectroscopy based on the stretchable metasurface.

Terahertz (THz) absorption spectroscopy is widely used for molecular label-free fingerprinting detection, but it is not capable of efficiently analyzing trace-amount sample materials. For improving the efficiency of terahertz absorptance spectroscopy detection, we propose a sensing strategy by treating the geometry sweeping spoof surface plasmon polariton (SSP) of the stretchable metasurface. For the first time, the geometry sweeping can be realized by dynamically stretching the polydimethylsiloxane (PDMS) flexible substrate, leading to the resonant frequency variation of the unit cell. This design provides a significant absorption enhancement factor about 270 times for a 0.1 μm lactose film in a broad terahertz band, enabling the unambiguous identification of different trace-amount samples. The designed method exhibits a novel solution for the enhancement of broad-band terahertz absorption spectroscopy and great application potential in the field of detecting trace-amount samples.

Graphene plasmonics for ultrasensitive imaging-based molecular fingerprint detection

A compact imaging-based metasurface nanophotonic sensor consisting of graphene nanoribbon arrays is proposed. It provides a chemically specific technique to resolve absorption fingerprints without the need for spectrometry and frequency scanning.

TOF-SIMS study of latent fingerprints on challenging substrates with the aid of transfer films.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been applied in forensic science for fingerprint detection. However, due to limitations of the instrument, it is not always possible to directly sample fingerprints on certain substrates. In this report, we indirectly sampled fingerprints using transfer films. First, we optimized the experimental conditions and identified transfer films with better results. We then explored the feasibility of revealing fingerprints after transfer and successfully transferred and revealed the detailed features of fingerprints on several common objects that could not be directly sampled. Fingerprints transferred from smooth surfaces yield clearer feature details in ion images. Additionally, we analyzed the substances in the transferred fingerprints and detected components of morphine and MDMA(3,4-methylenedioxy-n-methylamphetamine). By combining feature details with identified chemical components, the identity of a person can be determined, linking suspects to the crime scene. This work provides a new approach for sample introduction in instrumental analysis, enabling TOF-SIMS to be applied in more scenarios.

Delving into the multifunctionality of Sr2NaMg2V3O12via RE3+ substitution for dual-mode temperature sensing, latent fingerprint detection and security inks

Multifunctionality of vanadate garnet phosphors in latent fingerprint detection, security inks, and dual-mode temperature sensing.

A mid-IR tunable graphene metasurface for ultrasensitive molecular fingerprint retrieval and refractive index sensing

Using the electrically tunable nature of graphene in the mid-IR range, a one-to-many mapping strategy between the metasurface and spectral signals is presented for ultrasensitive molecular fingerprint detection and refractive index sensing.

Aggregation-induced emission solid-state multicolor fluorescent carbon dots for LEDs and fingerprints applications

At present, most of the reported carbon dots (CDs) are still dispersed in the solvent in liquid state. However, solid-state CDs cannot fundamentally prevent the aggregation-caused quenching effect (ACQ), which seriously affects their application. Herein, hydrophobic solid-state luminescent CDs with typical aggregation-induced emission (AIE) behavior were synthesized by simple solvothermal method using dithiosalicylic acid (DSTA) and acetic acid. The AIE behavior of CDs is mainly due to the presence of disulfide bonds, which restrict the intramolecular rotation of CDs surface groups around them, thus generating solid-state fluorescence (SSF) in long-wave emission. In addition, by using MA, urea and sulfonamide to tune the emission behavior of CDs, red, yellow and green AIE CDs named R-CDs, Y-CDs and G-CDs were obtained successfully. The as-prepared CDs powder was further applied to fabricate multi-color light-emitting diodes (LEDs) on UV chips. The fabricated tri-color LED devices can maintain high color purity and color rendering index (CRI). More importantly, the Correlated color temperature (CCT) of the three LED devices was located in the warm light area, which could effectively reduce visual fatigue. Finally, we applied three kinds of AIE CDs in fingerprint detection and effectively displayed the details.

Facile Preparation Strategy of Novel Carbon Dots with Aggregation‐Induced Emission and Room‐Temperature Phosphorescence Characteristics

AbstractAs one of the most promising fluorescent nanomaterials, carbon dots (CDs) are extensively studied. Nevertheless, one‐pot synthesis methods for CDs with both dual emission aggregation‐induced emission (AIE) and room‐temperature phosphorescence (RTP) could lead to significant breakthrough in extensive application fields. Herein, a new class of CDs (E‐CCDs) with reversible luminescence (blue dissolved fluorescence and red AIE) and RTP behavior is obtained with an eco‐friendly, low‐cost one‐pot solvothermal method. E‐CCDs exhibit dual fluorescence emission at 460 (Em‐1) and 600 nm (Em‐2), which is related to different emission centers. The addition of cyanic acid enhances the RTP behavior with a lifetime of 1.17 s, which lasts for ≈9 s to the naked eye. Based on the unique fluorescence and phosphorescence characteristics of CDs, E‐CCDs can be potentially used for fingerprint detection and information encryption.