Fluorescent nanoparticle compositions and their use in latent fingerprint development

Abstract

This invention provides a fluorescent nanoparticle composition and its application in latent fingerprint development. In this invention, the fluorescent nanoparticles, SiO2@C, have a particle size of 50 nm to 200 nm. These fluorescent nanoparticles can be applied to cutting tools, silicon wafers, wood, or rusty iron sheets. The fluorescent nanoparticles SiO2@C of this invention emit fluorescent signals of different colors, such as blue, green, and red, under different excitation wavelengths, adapting to background surfaces of different colors. Compared with other nanoparticles in the prior art, the nanoparticles of this invention exhibit brighter and more uniform fluorescence under excitation, significantly enhancing the contrast between fingerprints and background objects. They can be applied to various smooth or rough substrates such as cutting tools, silicon wafers, and wood, clearly displaying fingerprint features with higher levels of detail.

Description

Technical Field

[0001] This invention relates to the field of latent fingerprint detection technology, and in particular to a fluorescent nanoparticle composition, as well as a method for preparing the composition and its application in latent fingerprint development. Background Technology

[0002] Latent fingerprint development is a common method for forensic examination in criminal cases. Existing latent fingerprint development techniques mainly include chemical methods (such as ninhydrin method and silver nitrate method), physical methods (such as powder brushing method), and optical methods (such as laser excitation). These traditional methods mostly suffer from technical defects such as insufficient sensitivity (e.g., poor development effect on old, complex backgrounds, or special materials), high hazard (some chemical reagents such as ethyl cyanoacrylate are toxic), and destruction of physical evidence.

[0003] Nanoparticles are a novel type of material applicable to latent fingerprint development. For example, Chinese invention patent application CN113528118A discloses a magnetic fluorescent nanoparticle, comprising magnetic nanoparticles as a substrate, a mesoporous spiky silica intermediate layer coating the substrate, and a fluorescent material deposited and crystallized within the mesoporous silica channels and distributed on the outer surface. When this particle is brushed onto the latent fingerprint area, it can be used to develop fingerprints under ultraviolet light. However, the preparation method of this nanoparticle is relatively complex, the required raw materials are difficult to obtain or expensive, and the development effect of this particle on rough surfaces is poor.

[0004] Therefore, there is an urgent need in this field for a more readily available latent fingerprint display technology with better display results. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a new material for latent fingerprint development, which further improves the latent fingerprint development effect on rough surfaces.

[0006] Therefore, this invention provides the application of fluorescent nanoparticles SiO2@C in latent fingerprint development.

[0007] In this invention, the particle size of the fluorescent nanoparticles SiO2@C is 50 nm to 200 nm.

[0008] According to a preferred embodiment, the fluorescent nanoparticles SiO2@C are brushed onto the latent fingerprint area and revealed using lasers and / or white light (400~700nm) with wavelengths of 365 nm, 450 nm, 530 nm, and 830 nm.

[0009] In this invention, the object containing the latent fingerprint area can be a knife, silicon wafer, wood, or rusty iron sheet.

[0010] In this invention, the fluorescent nanoparticles SiO2@C can be prepared using a modified Stöber method (GHIMIRE PP, JARONIEC M. Renaissance of Stöber method for synthesis of colloidal particles: New developments and opportunities[J]. Journal of Colloid and Interface Science, 2021, 584: 838-865). First, the modified Stöber method is used to prepare nano-SiO2 particles. The Stöber method is a method for producing SiO2 nanospheres using the hydrolysis-condensation process of tetraethyl orthosilicate (TEOS) under ammonia catalysis. Its main reaction principle consists of two processes: hydrolysis and condensation. In the hydrolysis step, tetraethyl orthosilicate is used as the SiO2 precursor, and the ethoxy (Si-OR) group in the penta-complex transition state is nucleophilically replaced with a silanol group (-Si-OH). This reaction process is carried out in the presence of water. Because the OH- ions in NH3·H2O are more nucleophilic than those in water, NH3·H2O can act as a catalyst in this reaction, accelerating the hydrolysis process. The reaction principle is as follows:

[0011]

[0012] Then, in the condensation step, the silanol groups (-Si-OH) in the siloxane condense to form (Si-O-Si) bonds, and the reaction principle is as follows:

[0013] Then, using SiO2 nanoparticles as a template, nano-SiO2@C was further prepared.

[0014] The synthesis of SiO2@C core-shell nanospheres utilizes the aforementioned principle; under the action of ammonia, the generated...

[0015]

[0016] SiO2 nanospheres surface with OH - Combining with negatively charged molecules, by adding a carbon source (such as phenolic resin) and NH4+ 4+ The positive and negative charges combine and spontaneously aggregate on the surface of SiO2 nanospheres, forming SiO2@RF organic spheres. These SiO2@RF organic spheres are then placed in a protective atmosphere and sintered at high temperature to carbonize the organic matter, thus forming SiO2@C core-shell nanospheres. Those skilled in the art can adjust the size and structure of the SiO2@C core-shell nanospheres by modifying the parameters of the preparation process.

[0017] Compared to other nanoparticles (such as silica nanoparticles), the fluorescent nanoparticles SiO2@C of this invention possess color tunability, emitting fluorescent signals of different colors such as blue, green, and red under different excitation wavelengths, thus adapting to background surfaces with different colors. This multicolor emission characteristic allows it to exhibit bright and uniform fluorescence under ultraviolet or visible light excitation, significantly enhancing the contrast between fingerprints and background objects.

[0018] This invention demonstrates through experiments that fluorescent nanoparticles SiO2@C can clearly display the first, second, and even third-level features of fingerprints on smooth substrates such as blades, silicon wafers, and wood, especially fine details such as sweat pores. The amount of detail information is higher than that of nano-silica particles and is significantly better than traditional latent fingerprint display materials such as bronze powder and aluminum powder.

[0019] Furthermore, the fluorescent nanoparticles SiO2@C of the present invention are also suitable for fingerprint display on multi-colored and patterned backgrounds, effectively overcoming the recognition difficulties of traditional powders on complex backgrounds, with no obvious background interference.

[0020] When the fluorescent nanoparticles of this invention are used in latent fingerprint development, they do not damage the surface of the object being tested. The particle material is safe and non-toxic, requires no chemical pretreatment, avoids contamination of physical evidence, and is highly safe for the human body.

[0021] The fluorescent nanoparticles of this invention are easy to use and can adapt to the detection needs of different scenarios by using lasers of different wavelengths. They are also highly compatible and can be used with existing physical evidence discovery equipment (such as conventional laser survey instruments), making them widely applicable and easy to promote. Attached Figure Description

[0022] Figure 1 Electron micrograph of SiO2 particles from Example 1;

[0023] Figure 2 Electron micrographs of SiO2@C particles from Example 2;

[0024] Figure 3 It is a fluorescence spectrum;

[0025] Figure 4 XPS plot;

[0026] Figure 5-6 Electron micrograph of latent fingerprint region on unpolished silicon wafer surface using SiO2 particles;

[0027] Figure 7-8 Electron microscopy images of latent fingerprint regions on an unpolished silicon wafer surface using SiO2@C particles;

[0028] Figure 9-13The images show the development and imaging of the surface of SiO2@C particle metal cutting tools using 365nm, 450nm, 530nm, and 830nm lasers and white light excitation, respectively.

[0029] Figure 14-18 The images show the development and imaging of the surface of SiO2 particle metal cutting tools using 365nm, 450nm, 530nm, and 830nm lasers and white light excitation, respectively.

[0030] Figures 19-20 The images show SiO2 particles and SiO2@C particles on a smooth glass slide, respectively, developed using ultraviolet light excitation.

[0031] Figure 21-22 These images show the development of SiO2 particles and SiO2@C particles on a wooden board surface using ultraviolet light excitation.

[0032] Figure 23-24 These are images of SiO2 particles and SiO2@C particles on an iron sheet surface, respectively, developed using white light excitation. Detailed Implementation

[0033] In this invention, unless otherwise specified, “%” for explaining proportions refers to weight percentage, and “:” refers to weight ratio.

[0034] Example 1 Preparation of nano-SiO2@C particles

[0035] GHIMIRE PP, JARONIEC M. Renaissance of Stöber method for synthesis of colloidal particles: New developments and opportunities[J]. Journal of Colloid and Interface Science, 2021, 584: 838-865 teaches the synthesis of SiO2@C nanoparticles using the Stöber method.

[0036] According to this teaching, after preparing SiO2 nanoparticles, SiO2@C core-shell nanospheres can be further prepared using the SiO2 nanoparticles as templates. Utilizing this principle, under the action of ammonia, the surface of the generated SiO2 nanospheres combines with OH- ions, becoming negatively charged, while the added carbon source (such as phenolic resin) reacts with NH4+. 4+The positively charged particles spontaneously aggregate onto the surface of SiO2 nanospheres under the interaction of positive and negative charges, forming SiO2 organic spheres. These organic SiO2 spheres are then sintered at high temperature under a protective atmosphere, carbonizing the organic matter to form SiO2@C core-shell nanospheres. The size and structure of the SiO2@C core-shell nanospheres can be controlled by adjusting the preparation process. For example, adjusting the concentration of ammonia, the ratio of alcohol to water, the proportion of precursors, and changing the type of silicon source precursor can all affect the reaction rate during the hydrolysis-condensation process, thus influencing the size of the generated SiO2@C core-shell nanospheres. For instance, increasing the proportion of water accelerates the hydrolysis rate, resulting in larger SiO2 particles; increasing the concentration of ammonia significantly increases the OH- ion concentration. - The quantity will also promote the formation of larger nanospheres.

[0037] SiO2 particles and SiO2@C particles obtained by TEM scanning, such as Figure 1-2 As shown.

[0038] Fluorescence spectra of the two nanoparticles were tested under conditions where the excitation peak (Ex) was at a similar position (approximately 520 nm), indicating that the obtained SiO2 and SiO2@C nanospheres have similar excited-state energy levels. For both samples, the emission peak (Em) intensity was slightly higher than the excitation peak, and a signal appeared at a position almost identical to the excitation and emission wavelengths. This signal originates from elastic Rayleigh scattering or resonant Rayleigh scattering. The carbon coating on the surface of the SiO2@C nanospheres introduces light absorption and interface scattering centers, leading to fluorescence quenching and a relatively weaker scattering signal. Furthermore, the carbon material itself has broadband absorption characteristics, strongly absorbing within the excitation wavelength range, thus reducing the intensity of the excitation light reaching the SiO2 matrix. Therefore, the fluorescence intensity of the SiO2@C nanospheres is significantly lower than that of pure, uncoated SiO2 nanospheres. Figure 3 As shown.

[0039] X-ray photoelectron spectroscopy (XPS) of two types of nanoparticles, such as Figure 4 As shown.

[0040] XPS analysis revealed structural changes on the SiO2 surface after the carbon coating, corresponding to Si2p, C1s, and O1s, respectively. The intrinsic XPS spectra of the original carbon-coated SiO2 all showed Si2p peaks at approximately 103 eV, attributed to Si... 4 ⁺-O bonds. Uncoated SiO2 surfaces typically exhibit a weak C1s signal around 284.78 eV, originating from adsorbed heterogeneous carbon from the environment. After carbon deposition, the C1s intensity increases significantly. The main component corresponds to the CC / CH bonds at -284.8 eV, while a small amount of CO bonds contribute at -286.5 eV, indicating that the carbon capping layer contains graphitic carbon and oxide functional groups.

[0041] Example 2: Performance Testing

[0042] Compare the development capabilities of SiO2 particles and SiO2@C particles on different surfaces.

[0043] Fingerprint samples were left on the surface of an unpolished silicon wafer. Small amounts of SiO2 particles and SiO2@C particles were respectively applied to the latent fingerprint area and then observed under an electron microscope. Figure 5-8 As shown in the figure. The results indicate that both different nanoparticles can display fingerprint features on a silicon wafer.

[0044] Fingerprint samples were left on the surface of a metal cutting tool. A small amount of SiO2@C particles was applied to the latent fingerprint area, and then developed using lasers at 365 nm, 450 nm, 530 nm, and 830 nm, and white light (400 nm-700 nm), respectively. Images of the latent fingerprints were then taken. Figure 9-13 As shown. A small amount of SiO2 particles was applied to the latent fingerprint area, and then developed using 365nm, 450nm, 530nm, and 830nm lasers and white light, respectively. Latent fingerprint images were then taken for each development, as shown. Figure 14-18 As shown in the figure, the results indicate that SiO2@C particles can clearly display fingerprints under light excitation at all wavelengths, but SiO2 particles are almost unable to display latent fingerprints under 365nm laser light. Furthermore, under 450nm laser light, SiO2@C particles exhibit significantly stronger fluorescence, thus providing better clarity and contrast in fingerprint display.

[0045] Fingerprint samples were left on a smooth glass slide. Small amounts of SiO2 particles and SiO2@C particles were respectively applied to the latent fingerprint area, and then ultraviolet light was used for penetrating imaging. Figures 19-20 As shown in the figure. The results indicate that SiO2@C particles exhibit better clarity and contrast, resulting in a better display effect.

[0046] Fingerprint samples were left on a rough wooden surface. Small amounts of SiO2 particles and SiO2@C particles were applied to the latent fingerprint area, and then imaged using ultraviolet light. Figure 21-22 As shown in the figure. The results indicate that both types of nanoparticles can display fingerprint details.

[0047] Fingerprint samples were left on the smooth patch surface. Small amounts of SiO2 particles and SiO2@C particles were applied to the latent fingerprint area, and then imaged using ultraviolet light. Figure 23-24 As shown in the figure. The results indicate that SiO2@C particles exhibit better clarity and contrast, resulting in a better display effect.

[0048] The above results demonstrate that the fluorescent nanoparticles SiO2@C of this invention can emit fluorescent signals of different colors, such as blue, green, and red, under different excitation wavelengths, thus adapting to background surfaces of different colors. Compared with nano-SiO2 particles, the nanoparticles of this invention exhibit brighter and more uniform fluorescence under excitation, significantly enhancing the contrast between fingerprints and background objects. Furthermore, they can be applied to various smooth or rough substrates such as blades, silicon wafers, and wood, clearly displaying fingerprint features with higher levels of detail.

Claims

1. Application of fluorescent nanoparticles SiO2@C in latent fingerprint development.

2. The application according to claim 1, characterized in that... The fluorescent nanoparticles SiO2@C have a particle size of 50 nm to 200 nm.

3. The application according to claim 1, characterized in that... The fluorescent nanoparticles SiO2@C were brushed onto the latent fingerprint area and then revealed using lasers and / or white light with wavelengths of 365 nm, 450 nm, 530 nm, and 830 nm.

4. The application according to claim 3, characterized in that... The object containing the latent fingerprint area is a knife, silicon wafer, wood, or rusty iron sheet.

Images