Magnetically active dual-mode (stokes / Anti-stokes luminescence) upconversion core-shell nanoparticles designed for latent fingerprint imaging

Abstract

The invention relates to a specially prepared type of upconversion nanomaterial designed for latent fingerprint detection, consisting of a GdF3 core doped with Yb3+ (Ytterbium), Er3+ (Erbium), and Eu3+ (Europium), and a GdF3-based shell layered on top.

Description

[0001] MAGNETICALLY ACTIVE DUAL-MODE (STOKES / ANTI-STOKES LUMINESCENCE) UPCONVERSION CORE-SHELL NANOPARTICLES DESIGNED FOR LATENT FINGERPRINT IMAGING

[0002] TECHNICAL FIELD

[0003] The invention relates to a specially prepared type of upconversion nanomaterial designed for latent fingerprint detection, consisting of a GdF3core doped with Yb3+(Ytterbium), Er3+(Erbium), and Eu3+(Europium), and a GdF3-based shell layered on top.

[0004] PRIOR ART

[0005] The need for defense and security ranks second in Maslow’s hierarchy of needs, immediately following basic necessities. Defense and security are indispensable elements supported by technology, protecting society from threats. Turkiye ranks among the countries with the highest defense industry expenditures globally, with a significant portion allocated to imports. This leads to an outflow of national income abroad. However, because defense industry products are generally of high added value, producing advanced technological goods domestically can contribute to substantial foreign currency inflows. For this reason, it seems essential to turn to the production of high-tech products that are not yet available in our country in this sector. Rapid and accurate detection of latent or visible fingerprints is crucial for public safety, and the materials used in this field are part of the defense industry. More specifically, fingerprint analysis falls within the scope of criminalistics — a discipline focused on the examination and analysis of evidence related to crime scenes.

[0006] The need for more advanced fingerprint detection techniques stems from several reasons:

[0007] Fingerprints are among the most common and valuable types of evidence found at crime scenes. However, they are sometimes weak or degraded due to poor conditions, making them difficult to detect using conventional methods. Advanced fingerprint detection techniques can render such traces visible even under challenging circumstances, facilitating criminal resolution and evidence collection.

[0008] Technological advances enable the development of more sensitive and effective tools for fingerprint detection. New materials, chemicals, imaging techniques, and software offer higher accuracy and reliability. New techniques are essential to counter evolving criminal tactics and preserve fingerprint evidence. Moreover, such techniques support fair trials and accurate decisions.

[0009] Fingerprint detection needs vary depending on the crime — e.g., theft, homicide, terrorism, smuggling — each requiring different scenarios. Advanced techniques can better respond to this diversity.

[0010] Latent fingerprint residues are composed of water-soluble compounds (such as endogenous salts, peptides, carbohydrates, urea) and water-insoluble or lipophilic compounds (such as sterols, wax esters, fatty acids, triglycerides), transferred to surfaces upon contact.

[0011] Fingerprint patterns characterized by ridges and valleys are analyzed at three levels. Level 1 includes macro details like ridge flow and general fingerprint pattern; Level 2 examines ridge bifurcations and terminations in detail; Level 3 reveals fine details such as sweat pores and ridge edge structures. While the first level is useful for the classification of fingerprints, the second level can provide insights into an individual's identity. However, according to forensic experts, the most unique, distinctive, and permanent information for individual identification can be obtained from the third-level model.

[0012] Fingerprints are often found at crime scenes in an invisible form, making them difficult to examine. This challenge has necessitated the development of various techniques to reveal the visible patterns of these residues, commonly referred to as latent fingerprints. These techniques are listed below:

[0013] - Silver nitrate method

[0014] - Cyanoacrylate fuming (CA)

[0015] - 1 ,8-diazafluoren-9-one (DFO) method

[0016] - Ninhydrin (NH) method

[0017] - Quantum dots

[0018] - Carbon dots

[0019] - Metallic nanomaterials

[0020] The existing materials and methods have proven insufficient for effective fingerprint imaging. Therefore, new promising materials are continually synthesized and tested. The disadvantages of currently used methods are outlined below: • Silver Nitrate Method:

[0021] This method is time consuming and can only be used on fingerprints that have been around for less than a week. Professionals must use protective equipment as it can be toxic when in contact with skin or inhaled. It produces low contrast images in many cases and is a costly product.

[0022] • Cyanoacrylate Fuming (CA):

[0023] Cyanoacrylate can cause respiratory problems and allergic reactions when inhaled. The waste generated during the fuming process is harmful to the environment. It causes changes and damage to some surfaces (such as plastic, wood). It is a method that requires application skills and experience and requires wearing special equipment during the process.

[0024] • 1 ,8-Diazafluoren-9-one (DFO) Method:

[0025] It is dangerous if it comes into contact with skin, is inhaled, or swallowed. It requires the use of protective equipment and has a long processing time. Since it is a sensitive method, it sometimes gives low-contrast results. It can cause color changes on some surfaces (such as plastic and wood) and is a costly product.

[0026] • Ninhydrin Method (NH):

[0027] It is a time-consuming process. It is not possible to use it on porous surfaces such as paper and plastic. It is not effective on fingerprints that contain low levels of oil and amino acids, and the fingerprint image created can easily fade. Therefore, it is difficult to store fingerprints that have undergone this process for a long time. It is a relatively expensive technique.

[0028] • Quantum Dots:

[0029] They are dangerous due to the toxic elements they contain. They require the use of protective equipment. Their properties can change due to light and other environmental factors, that is, they are not stable. They are not suitable for use on all types of surfaces and are a method that requires skill and experience. They are costly and, since they are a new technique, standardization procedures are limited.

[0030] • Carbon Dots:

[0031] They exhibit low contrast on some surfaces. Their ability to leave a mark is relatively low. They can not adhere to all surfaces and their use is limited. They can leave residue on the surface and therefore it can be difficult to obtain a fingerprint image. Since it is a new technique, standardization procedures are limited. • Metal Nanomaterials:

[0032] The synthesis of metal nanomaterials is costly. Materials containing metals such as mercury and cadmium are toxic and may produce environmentally hazardous waste. They cannot be applied to all surfaces, and their stability is not high, which can cause storage and field application problems. Their use requires expert skill and experience, and since it is a new technique, standardization procedures are limited.

[0033] OBJECTIVE OF THE INVENTION

[0034] The nanomaterials in question emit higher-energy photons in the UV or visible range (Anti-Stokes shift) upon excitation by low-energy photons in the infrared (IR) or near-infrared (NIR) region. Due to non-overlapping absorption and emission bands and narrow emission band widths (less than 30 nm), the signal can be easily distinguished from the excitation source.

[0035] Compared to organic dyes or quantum dots, these materials offer superior photostability and chemical durability and can emit continuously. They do not cause autofluorescence due to biological components and do not damage residues when excited with low-energy (NIR or I R) photons.

[0036] Applicable to glass, ceramic, leather, fabric, paper, metal, and polymer surfaces.

[0037] This material is synthesized in a short time, with low energy input, and via an environmentally and user-friendly method.

[0038] Thanks to its magnetic properties, excess powder applied to fingerprint surfaces can be easily removed using a magnet to ensure clean imaging.

[0039] This fingerprint powder, composed of nanoparticles, enables high-resolution third-level fingerprint imaging by facilitating both Anti-Stokes (via Er3+) and Stokes (via Eu3+) luminescence.

[0040] The concept offers several advantages:

[0041] - Nanoparticles do not obscure level-three fingerprint details.

[0042] - The synthesis method falls under green chemistry and allows for rapid, eco- and user-friendly production.

[0043] Traditional synthesis methods such as thermal decomposition, hydrothermal / solvothermal synthesis, and high-temperature co-precipitation have drawbacks including high cost, time consumption, toxic by-product generation, and requirements for high temperature and pressure. Green chemistry provides notable advantages. The ultra-fast room temperature precipitation method allows easy synthesis of monodisperse, non-toxic nanoparticles with low energy.

[0044] - Magnetic properties of Gd3+ions help remove excess powder that might obscure fingerprint details.

[0045] - Core-shell structure yields higher luminescence intensity for clearer imaging.

[0046] - When excited at 980 nm, Er3+emits green luminescence (-550 nm, with possible red emission). When excited at 395 nm, Eu3+emits strong red luminescence (-615 nm), supporting detailed imaging.

[0047] Upconversion nanoparticles intended for latent fingerprint detection can be used in various fields such as crime scene investigation, forensic science, narcotics, and counterfeit detection. These materials can help identify and diagnose unknown bodies, criminals, and forgers.

[0048] In Turkiye, current methods provide only second-level fingerprint images, making identification difficult. Third-level fingerprint images reveal more features including sweat pores and can be rapidly matched in databases. The upconversion nanoparticles subject to this patent enable third-level imaging.

[0049] Conventional fingerprint detection techniques can damage chemical markers such as DNA, drugs, and explosives in the fingerprint residue, impairing forensic analysis. This invention allows for the visualization of fingerprints without damaging such residues. Furthermore, because the powder does not interact with biological components, there is no interference and clear images can be obtained. The material is non-toxic and safe for use.

[0050] DETAILED DESCRIPTION OF THE INVENTION

[0051] The nanomaterial subject to the invention is a specially prepared upconversion nanomaterial for latent fingerprint detection, composed of a GdF3core doped with Yb3+, Er3+, and Eu3+, and a GdF3-based shell. The key technical characteristics of the defined upconversion nanoparticles (GdF3:Yb3+:Er3+:Eu3+@GdF3) are listed below:

[0052] Synthesis: The nanomaterial is synthesized using green chemistry. Energy and time consumption are minimal. The synthesis process does not involve toxic components or waste. Composition: The core of the nanoparticles consists of GdF3crystal doped with lanthanide group ions Yb3+, Er3+, and Eu3+. The outer layer (shell) is composed solely of GdF3. This is denoted as GdF3:Yb3+:Er3+:Eu3+@GdF3.

[0053] Size and Morphology: The nanoparticles are controllably synthesized with sizes ranging from 50 to 500 nm. Depending on synthesis conditions, shapes may be spherical, rod-shaped, triangular, etc.

[0054] Crystal Structure: The crystal structure consists of a GdF3core and a GdF3shell, which prevents energy loss and luminescence quenching.

[0055] Optical Properties

[0056] Upconversion Luminescence: Yb3+ions absorb low-energy photons (NIR -980 nm) and transfer the energy in two or more steps to Er3+ions, which then emit light at 550 nm. This upconversion (Anti-Stokes) process separates excitation and emission wavelengths, enabling clear imaging. Luminescence intensity is optimized by adjusting the molar ratios of the ions: 10-25% Yb3+, 1-8% Er3+, and 0.5-2% Eu3+.

[0057] Eu3+Luminescence: Upon excitation with 395 nm light, Eu3+emits strong red luminescence at 615 nm (Stokes shift).

[0058] Excitation Wavelengths: The nanomaterial is excited by NIR light (-980 nm) for efficient energy transfer to Yb3+ions, and optionally by 395 nm light for Eu3+excitation if needed . Magnetic Properties'. Gd3+ions confer magnetic behavior, allowing excess powder on surface to be removed with a magnet.

[0059] Efficiency and Sensitivity: The material exhibits high upconversion efficiency and sensitivity, providing high-resolution latent fingerprint images. Adhesion Properties: The nanomaterial interacts strongly with lipids and other components in fingerprint residues, ensuring firm adherence to ridge patterns and uniform coating.

[0060] Chemical Stability: The material is chemically stable under operational conditions, ensuring long-term reliability for forensic applications.

[0061] Compatibility: The material is compatible with common forensic surfaces including glass, ceramic, leather, fabric, paper, metal, and polymers.

[0062] Detection Mechanism: Converts NIR or 395 nm excitation into visible green and red emission to highlight fingerprint ridge patterns and increase latent print visibility. Also capable of revealing sweat pores.

[0063] Fingerprint Application and Imaging:

[0064] - Hands are first washed with soap.

[0065] - The thumb is gently rubbed on the forehead.

[0066] - The finger is then pressed onto different material surfaces at room temperature to leave latent prints.

[0067] - Nanopowder is gently applied to the surface.

[0068] - After mechanical adhesion to ridge residues, excess powder is removed with a magnet.

[0069] - The powdered print is excited with 395 nm and 980 nm light, and the resulting green, red (Er3+), and red (Eu3+) luminescence images are captured separately using a high-resolution camera.

[0070] Safety Measures:

[0071] - The nanopowder does not contact skin.

[0072] - Non-toxic.

[0073] - Use of gloves and mask is sufficient for safe application.

Claims

CLAIMS1. Magnetic dual-mode (Stokes / anti-Stokes luminescence) upconversion coreshell nanoparticles for use in latent fingerprint imaging, characterized in that the core structure comprises a GdF3crystal doped with Yb3+(Ytterbium), Er3+(Erbium), and Eu3+(Europium), and the shell comprises a GdF3crystal layer coated thereon.

2. Composition according to claim 1 , characterized in that the molar percentages of Yb3+, Er3+, and Eu3+ions in the GdF3crystal structure are 10-25 mol% for Yb3+, 1-8 mol% for Er3+, and 0.5-2 mol% for Eu3+.

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