Fluorescent silicon nanoparticles, a preparation method thereof and water-soluble fluorescent anti-counterfeiting ink

Abstract

This application provides fluorescent silicon nanoparticles, their preparation method, and a water-soluble fluorescent anti-counterfeiting ink, relating to the field of silicon nanomaterials technology. The preparation method of the fluorescent silicon nanoparticles includes: mixing and reacting a silicon source, a reducing agent, and water to obtain the fluorescent silicon nanoparticles; wherein the silicon source includes 3-aminopropyltriethoxysilane; and the reducing agent includes humic acid. The fluorescent silicon nanoparticles prepared in this application appear green under 365nm ultraviolet light irradiation and can be applied to water-soluble fluorescent anti-counterfeiting inks. This application uses a low-cost, simple, readily available, rapid, convenient, and mild preparation method to prepare fluorescent silicon nanoparticles with excellent acid and alkali resistance, light resistance, and salt resistance. When applied to fluorescent anti-counterfeiting inks, they can produce clear and bright fluorescent patterns.

Description

Technical Field

[0001] This application relates to the field of silicon nanomaterials technology, and in particular to a fluorescent silicon nanoparticle, its preparation method, and a water-soluble fluorescent anti-counterfeiting ink. Background Technology

[0002] In recent years, information security and anti-counterfeiting have attracted widespread attention, and the demand for developing new anti-counterfeiting materials and technologies has become increasingly urgent. The most effective and direct method to distinguish genuine products from counterfeits is through anti-counterfeiting technology. Among these, fluorescent anti-counterfeiting technology based on fluorescent materials is widely used due to its advantages such as rapid identification, ease of operation, time-saving, and strong anti-counterfeiting performance. Currently, commonly used fluorescent anti-counterfeiting materials mainly include semiconductor quantum dots, carbon quantum dots, polymer fluorescent materials, and rare-earth complex fluorescent nanoparticles. Although these high-performance fluorescent materials have achieved good anti-counterfeiting applications, they also have significant drawbacks, such as poor photostability, high toxicity, complex preparation, and high cost.

[0003] Compared to traditional light-emitting semiconductor quantum dots and organic fluorescent dyes, water-soluble fluorescent silicon nanoparticles (SiNPs) represent a new research hotspot in the field of fluorescent nanomaterials. Due to their abundant and inexpensive resources, excellent biocompatibility and biodegradability, low toxicity, high fluorescence intensity, excellent fluorescence stability / resistance to photobleaching, and ease of surface modification, they are considered ideal fluorescent materials and are widely used in fluorescence sensing, bioimaging, disease diagnosis, and many other fields. For example, SiNPs have been successfully used to detect dopamine, heparin, tetracycline, intracellular pH, and reactive oxygen species. More importantly, SiNPs can be biodegraded in mouse models, and the degradation product, orthosilicic acid, is well compatible with many biological tissues and is ultimately cleared and excreted through the kidneys without causing significant toxicity to mice. This indicates that SiNPs possess good biocompatibility and biosafety, as well as low toxicity. Therefore, designing and preparing low-cost, non-toxic, and photostable SiNPs for application in fluorescent anti-counterfeiting materials is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide fluorescent silicon nanoparticles, their preparation method, and water-soluble fluorescent anti-counterfeiting ink. By using a low-cost, simple, readily available, rapid, convenient, and mild preparation method, fluorescent silicon nanoparticles with excellent acid and alkali resistance, light resistance, and salt resistance are prepared. When applied to fluorescent anti-counterfeiting ink, clear and bright fluorescent patterns can be obtained.

[0005] To achieve the above objectives, the technical solution of this application is as follows:

[0006] This application provides a method for preparing fluorescent silicon nanoparticles, comprising:

[0007] The fluorescent silicon nanoparticles are obtained by mixing and reacting a silicon source, a reducing agent, and water.

[0008] The silicon source includes 3-aminopropyltriethoxysilane;

[0009] The reducing agent includes humic acid.

[0010] Preferably, the mixture includes:

[0011] After dissolving the reducing agent in an alkaline solution to prepare a reducing agent solution, the silicon source and the reducing agent solution are then added to the water.

[0012] Optionally, when the reducing agent is humic acid, the alkaline solution is a 1 wt% sodium hydroxide solution; the concentration of humic acid in the reducing agent solution is 5 mmol / L-20 mmol / L.

[0013] More preferably, during the mixing process, the volume ratio of the silicon source, the reducing agent solution, and the water is (0.5-0.8):(1.0-2.5):(2.5-3).

[0014] Preferably, the reaction comprises:

[0015] After the mixture is obtained, the mixture is stirred continuously at a speed of 800 rpm to 1200 rpm under standard atmospheric pressure and a temperature of 10℃-40℃ for 20 min to 40 min.

[0016] Preferably, after the reaction is completed, the process further includes:

[0017] After the reaction was completed, the solution was transferred to a 500Da-1000Da dialysis bag for dialysis to obtain the purified fluorescent silicon nanoparticles.

[0018] Preferably, after obtaining the fluorescent silicon nanoparticles, the solution is diluted with water and stored at 2℃-6℃.

[0019] This application also provides a fluorescent silicon nanoparticle, which is prepared using the above-described method for preparing fluorescent silicon nanoparticles.

[0020] Preferably, the fluorescent silicon nanoparticles appear green under 365nm ultraviolet light irradiation;

[0021] The fluorescent silicon nanoparticles have a particle size of 2.2 nm to 3.0 nm.

[0022] This application also provides a water-soluble fluorescent anti-counterfeiting ink, comprising fluorescent silicon nanoparticles prepared by the above-described method for preparing fluorescent silicon nanoparticles.

[0023] The beneficial effects of this application are:

[0024] The method for preparing fluorescent silicon nanoparticles in this application uses humic acid as a reducing agent to synthesize silicon nanoparticles with obvious fluorescence in one step. The preparation method is low in cost, simple, fast and convenient, with mild conditions and readily available raw materials. No further chemical modification or complex and expensive instruments are required.

[0025] The fluorescent silicon nanoparticles of this application exhibit excellent photostability and chemical stability after prolonged irradiation with a 365nm ultraviolet lamp, in a high-concentration salt environment, or in an acidic or alkaline environment with a pH of 3-12, and can be used for fluorescent anti-counterfeiting technology in complex external environments.

[0026] In the water-soluble fluorescent anti-counterfeiting ink of this application, the fluorescent silicon nanoparticles prepared by the above preparation method can perform fluorescent writing and fluorescent pattern drawing imaging. Under ultraviolet light irradiation, clear and bright fluorescent patterns can be obtained, which is particularly suitable for packaging printing of food, beverages and pharmaceuticals. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0028] Figure 1 The XRD pattern of the fluorescent silicon nanoparticles prepared in Example 1;

[0029] Figure 2 TEM image of the fluorescent silicon nanoparticles prepared in Example 1;

[0030] Figure 3 The UV-Vis absorption spectrum of the fluorescent silicon nanoparticles prepared in Example 1;

[0031] Figure 4 The fluorescence excitation and emission spectra of the fluorescent silicon nanoparticles prepared in Example 1 are shown below.

[0032] Figure 5 A bar chart showing the fluorescence intensity of silicon nanoparticles prepared using different amounts of humic acid.

[0033] Figure 6 A bar chart showing the fluorescence intensity of silicon nanoparticles prepared using different reaction times;

[0034] Figure 7 The images show the silicon nanoparticle solutions prepared with different amounts of APTES under 365nm UV light irradiation.

[0035] Figure 8 The images show the actual results of silicon nanoparticle solutions prepared using different silicon sources under 365nm ultraviolet light irradiation.

[0036] Figure 9 The images show the actual results of silicon nanoparticle solutions prepared with different reducing agents under 365nm ultraviolet light irradiation.

[0037] Figure 10 Sunlight imaging and fluorescence imaging under a 365nm ultraviolet lamp are shown for the butterfly pattern replicated on Xuan paper by the water-soluble fluorescent anti-counterfeiting ink prepared in Example 1 after it has been air-dried.

[0038] Figure 11 Sunlight imaging and fluorescence imaging under a 365nm ultraviolet lamp are shown for the peony flower pattern replicated on Xuan paper by the water-soluble fluorescent anti-counterfeiting ink prepared in Example 1 after it has been air-dried.

[0039] Figure 12 Sunlight imaging and fluorescence imaging under a 365nm ultraviolet lamp after the bamboo pattern replicated on Xuan paper by the water-soluble fluorescent anti-counterfeiting ink prepared in Example 1 is shown.

[0040] Figure 13 Sunlight imaging and fluorescence imaging under a 365nm ultraviolet lamp after the characters "Gan Nong" written on Xuan paper with the water-soluble fluorescent anti-counterfeiting ink prepared in Example 1 have dried;

[0041] Figure 14 The fluorescence intensity test results of the fluorescent silicon nanoparticles prepared in Example 1 in NaCl solutions of different concentrations are shown.

[0042] Figure 15 The fluorescence intensity test results of the fluorescent silicon nanoparticles prepared in Example 1 in PBS buffer solutions with pH 3-12 are shown.

[0043] Figure 16 The fluorescence intensity test image shows the fluorescence intensity of the fluorescent silicon nanoparticles prepared in Example 1 after continuous irradiation under a 446nm ultraviolet lamp for 60 minutes.

[0044] Figure 17 The fluorescence emission spectra of the fluorescent silicon nanoparticle solution prepared in Example 1 after the addition of different concentrations of CRM are shown.

[0045] Figure 18 The graph shows the linear relationship between the fluorescence intensity difference F0-F and the CRM concentration of the fluorescent silicon nanoparticle solution prepared in Example 1. Detailed Implementation

[0046] As used in this article:

[0047] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus. The conjunction "composed of" excludes any unnamed elements, steps, or components.

[0048] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0049] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0050] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0051] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0052] This application provides a method for preparing fluorescent silicon nanoparticles, comprising: mixing a silicon source, a reducing agent, and water, and reacting them to obtain the fluorescent silicon nanoparticles. The silicon source includes aminopropyltriethoxysilane (APTES), and the reducing agent includes humic acid.

[0053] It should be noted that in the preparation method of this application, different silicon source materials and different reducing agents are used to react and prepare fluorescent silicon nanoparticles with different fluorescence effects. For example, when 3-aminopropyltrimethoxysilane (APTMS) or N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAMO) is mixed with humic acid, the fluorescent particles prepared by DAMO have the weakest fluorescence effect, which is almost invisible. Although APTMS has a fluorescence effect, it is not as good as the fluorescence effect of the APTES prepared by this application.

[0054] In one embodiment of this application, the mixing includes: dissolving the reducing agent in an alkaline solution to prepare a reducing agent solution, and then adding the silicon source and the reducing agent solution to the water.

[0055] More preferably, when the reducing agent is humic acid, the alkaline solution is a 1 wt% sodium hydroxide solution.

[0056] Humic acid was dissolved in a 1 wt% NaOH solution to prepare a humic acid solution. Then, the silicon source 3-aminopropyltriethoxysilane and the humic acid solution were added to water and mixed and stirred.

[0057] It should be noted that the water used in this application is preferably ultrapure water or deionized water.

[0058] In one embodiment of this application, the concentration of humic acid in the reducing agent solution is 5 mmol / L to 20 mmol / L, for example, it can be 5 mmol / L, 10 mmol / L, 15 mmol / L, 20 mmol / L, or any value between 5 mmol / L and 20 mmol / L. More preferably, an aqueous solution of humic acid with a concentration of 10 mmol / L is selected.

[0059] In one embodiment of this application, during mixing, the volume ratio of silicon source, reducing agent solution and water is (0.5-0.8):(1.0-2.5):(2.5-3), for example, it can be any value between 0.5:1.0:2.5, 0.6:1.2:2.7, 0.7:1.5:3.0, 0.8:1.5:2.7, 0.8:2.0:3.0, 0.8:2.5:2.7 or (0.5-0.8):(1.0-2.5):(2.5-3), more preferably 0.8:1.5:2.7.

[0060] In one embodiment of this application, the conditions required for the reaction include: standard atmospheric pressure and a temperature of 10°C-40°C, for example, any value between 10°C, 15°C, 20°C, 25°C, 30°C, 40°C, or 10°C-40°C; continuous stirring of the mixed solution at a speed of 800 rpm-1200 rpm, for example, any value between 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, or 800 rpm-1200 rpm; and a reaction time of 20 min-40 min, for example, any value between 20 min, 25 min, 30 min, 35 min, 40 min, or 20 min-40 min.

[0061] More preferably, the reaction is carried out at a temperature of 25°C-30°C and a stirring speed of 1000 rpm for 30 minutes.

[0062] In one embodiment of this application, after the reaction is completed, the method further includes: transferring the solution after the reaction to a 500Da-1000Da dialysis bag for dialysis to obtain purified fluorescent silicon nanoparticles.

[0063] Specifically, 0.8 mL of 3-aminopropyltriethoxysilane and 1.5 mL of 10 mM humic acid solution were added to a round-bottom flask containing 2.7 mL of ultrapure water. The mixture was stirred using a magnetic stirrer at 1000 rpm for 30 min. After the reaction was complete, the mixture was dialyzed to obtain purified fluorescent silicon nanoparticles. The prepared silicon nanoparticles are generally diluted with water to obtain a silicon nanoparticle solution, which is then stored at 2℃-6℃ for later use, preferably at 4℃.

[0064] The preparation method is simple, uses readily available raw materials, can be carried out at room temperature and pressure, and requires a short reaction time, which greatly reduces the preparation cost of fluorescent silicon nanoparticles and improves the preparation efficiency of the product.

[0065] This application also provides a fluorescent silicon nanoparticle, which is prepared using the above-described method for preparing fluorescent silicon nanoparticles.

[0066] It is understandable that, because the above preparation method is carried out in water, the prepared nanoparticles are water-soluble, that is, the fluorescent silicon nanoparticles are water-soluble fluorescent silicon nanoparticles.

[0067] In one embodiment of this application, fluorescent silicon nanoparticles appear green under 365nm ultraviolet light irradiation.

[0068] In one embodiment of this application, the fluorescent silicon nanoparticles have a particle size of 2.2 nm to 3.0 nm, the particles have a spherical structure, and the average particle size is 2.6 nm.

[0069] This application also provides a water-soluble fluorescent anti-counterfeiting ink, comprising the aforementioned fluorescent silicon nanoparticles.

[0070] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0071] Example 1

[0072] This embodiment provides a fluorescent silicon nanoparticle, and the specific preparation method includes:

[0073] At room temperature and pressure, 0.8 mL of 3-aminopropyltriethoxysilane (APTES) and 1.5 mL of 10 mM humic acid solution were added to a round-bottom flask containing 2.7 mL of ultrapure water. The mixture was stirred at 1000 rpm for 30 min using a magnetic stirrer at room temperature and pressure. After the reaction, the solution was transferred to a dialysis bag with a molecular weight of 1000 Da for dialysis to obtain purified fluorescent silicon nanoparticles. The purified nanoparticles were diluted 50 times with water to obtain a silicon nanoparticle solution, which was then sealed and stored at 4°C for later use.

[0074] This embodiment provides a water-soluble fluorescent anti-counterfeiting ink, comprising: a silicon nanoparticle solution prepared as described above in this embodiment.

[0075] Example 2

[0076] The preparation method of the fluorescent silicon nanoparticles in this embodiment is the same as that in Example 1, except that the amount of 3-aminopropyltriethoxysilane added is changed from 0.8 mL to 0.6 mL.

[0077] Example 3

[0078] The preparation method of fluorescent silicon nanoparticles in this embodiment is the same as in Example 1, except that the 10mM humic acid solution is replaced by 1.0mL instead of 1.5mL.

[0079] Example 4

[0080] The preparation method of fluorescent silicon nanoparticles in this embodiment is the same as in Example 1, except that the 10mM humic acid solution is replaced by 2.0mL instead of 1.5mL.

[0081] Example 5

[0082] The preparation method of fluorescent silicon nanoparticles in this embodiment is the same as in Example 1, except that the 10mM humic acid solution is replaced by 2.5mL instead of 1.5mL.

[0083] Example 6

[0084] The preparation method of fluorescent silicon nanoparticles in this embodiment is the same as in Example 1, except that the stirring reaction time is changed from 30 min to 20 min.

[0085] Example 7

[0086] The preparation method of fluorescent silicon nanoparticles in this embodiment is the same as in Example 1, except that the stirring reaction time is changed from 30 min to 40 min.

[0087] Comparative Example 1

[0088] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the amount of 3-aminopropyltriethoxysilane added is changed from 0.8 mL to 1.0 mL.

[0089] Comparative Example 2

[0090] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the amount of 3-aminopropyltriethoxysilane added is changed from 0.8 mL to 1.5 mL.

[0091] Comparative Example 3

[0092] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the amount of 3-aminopropyltriethoxysilane added is changed from 0.8 mL to 2.0 mL.

[0093] Comparative Example 4

[0094] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the 10 mM humic acid solution is replaced with 0.5 mL instead of 1.5 mL.

[0095] Comparative Example 5

[0096] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the 10 mM humic acid solution is replaced by 3.0 mL instead of 1.5 mL.

[0097] Comparative Example 6

[0098] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the stirring reaction time is changed from 30 min to 10 min.

[0099] Comparative Example 7

[0100] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the stirring reaction time is changed from 30 min to 50 min.

[0101] Comparative Example 8

[0102] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the stirring reaction time is changed from 30 min to 60 min.

[0103] Comparative Example 9

[0104] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that 3-aminopropyltriethoxysilane is replaced with 3-aminopropyltrimethoxysilane (APTMS).

[0105] Comparative Example 10

[0106] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that aminopropyltriethoxysilane is replaced with N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAMO).

[0107] Comparative Example 11

[0108] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the humic acid solution is replaced with sodium citrate solution.

[0109] Comparative Example 12

[0110] The preparation method of the fluorescent silicon nanoparticles in this comparative example is the same as that in Example 1, except that the humic acid solution is replaced with bovine serum albumin solution.

[0111] The silicon nanoparticles prepared in the various embodiments and comparative examples were characterized by XRD. The results showed that the nanoparticle samples prepared in the embodiments and comparative examples of this application were all amorphous silicon. Figure 1 XRD patterns of fluorescent silicon nanoparticles for Example 1 are shown.

[0112] Simultaneously, the fluorescent silicon nanoparticles prepared in Example 1 were characterized by TEM. The results showed that the silicon nanoparticles in the sample of Example 1 had good monodispersity, exhibited a spherical structure, a particle size distribution of 2.2-3.0 nm, and an average particle size of approximately 2.6 nm. Figure 2 As shown.

[0113] The nanosamples prepared in Example 1 were also subjected to UV-Vis absorption spectroscopy and fluorescence excitation and emission spectroscopy tests, and the results are as follows: Figure 3 , Figure 4 As shown. By Figure 3As can be seen, the obvious absorption peaks at 300 nm and 330 nm belong to the π-π* transition of C=C, while the absorption peak at 540 nm belongs to the n-π* transition of C=O. Figure 4 As can be seen, the maximum excitation wavelength of silicon nanoparticles is 446 nm, and the maximum emission wavelength is 504 nm.

[0114] Then, the fluorescence intensity of the silicon nanoparticle solutions prepared in Examples 1, 3-7, and 4-8 was tested, and the results are as follows: Figure 5 , Figure 6 As shown. Figure 5 The figure represents the effect of different amounts of humic acid on the fluorescence intensity of the prepared silicon nanoparticles. Figure 6 The figure represents the effect of different reaction times on the fluorescence intensity of the prepared silicon nanoparticles. As shown in the figure, the silicon nanoparticles prepared with humic acid dosage of 1.0 mL–2.5 mL and reaction time of 20 min–40 min exhibited relatively high fluorescence intensity. More preferably, the silicon nanoparticles prepared with humic acid dosage of 1.5 mL and reaction time of 30 min achieved the highest fluorescence intensity.

[0115] This application also tested the fluorescence effect of the silicon nanoparticle solutions prepared in Examples 1-2 and Comparative Examples 1-3 under 365nm ultraviolet light irradiation, such as Figure 7 As shown, Figure 7 From left to right, the amounts of APTES used are 0.6 mL, 0.8 mL, 1 mL, 1.5 mL, and 2 mL. The fluorescence effects of the silicon nanoparticle solutions prepared in Comparative Examples 9-10 and Example 1 under 365 nm ultraviolet light irradiation were tested. Figure 8 As shown, Figure 8 From left to right, the silicon sources are APTMS, APTES, and DAMO. The fluorescence effects of the silicon nanoparticle solutions prepared in Comparative Examples 11-12 and Example 1 under 365nm ultraviolet light irradiation were tested. Figure 9 As shown, Figure 9 From left to right, the reducing agents are sodium citrate, bovine serum albumin, and humic acid.

[0116] Depend on Figure 7 It is evident that the fluorescence effect is better when the amount of the silicon source 3-aminopropyltriethoxysilane is 0.6 mL-0.8 mL, especially when the amount is 0.8 mL, the fluorescence effect is the best. Figure 8 , Figure 9 It is evident that, compared to APTMS and DAMO, the fluorescence effect obtained by using 3-aminopropyltriethoxysilane (APTES) as the silicon source in this application is the best; and compared to sodium citrate and serum albumin, the fluorescence effect obtained by using humic acid as the reducing agent in this application is the best.

[0117] For the water-soluble fluorescent anti-counterfeiting inks prepared in each of the examples and comparative examples, a small amount of the ink solution was taken with a writing brush, and the patterns of butterflies, peonies, and bamboo were respectively replicated on rice paper according to their textures. At the same time, the two characters "Gannong" were manually written on the rice paper. After the solution on the rice paper was naturally air-dried, it was found that a pale yellow trace appeared on the surface of the rice paper, as shown respectively in Figure 10 , Figure 11 , Figure 12 , Figure 13 the left figures in

[0118] Then, the air-dried images were irradiated under an ultraviolet lamp at 365 nm. The images under ultraviolet light irradiation are shown respectively in Figure 10 , Figure 11 , Figure 12 , Figure 13 the right figures in . It can be seen that the patterns and handwriting of butterflies, peonies, bamboo, and "Gannong" are clear and complete, and the patterns show obvious green fluorescence, the edges of the images are neat, and the important details are clearly visible.

[0119] The results after the pattern replication and air-drying indicate that: the fluorescent silicon nanoparticles prepared in this application can be used as an excellent fluorescent material for the production of anti-counterfeiting labels.

[0120] In addition, the salt resistance, acid and alkali resistance, and light resistance properties of the fluorescent silicon nanoparticles were also tested in this application. Specifically, the fluorescent silicon nanoparticles prepared in Example 1 were added to NaCl solutions with different concentrations, and the fluorescence intensities in NaCl solutions with different concentrations were tested as shown in Figure 14 . It was found that the fluorescence intensity did not change significantly, indicating that the fluorescent silicon nanoparticles have excellent salt stability and can be used in an environment with high ionic strength.

[0121] The fluorescent silicon nanoparticles prepared in Example 1 were added to PBS buffer solutions with different pH values (3 - 12), and the fluorescence intensities were tested, as shown in Figure 15 . It was found that the fluorescence intensity remained basically constant, indicating that it is very stable within a wide pH range.

[0122] The solution of the fluorescent silicon nanoparticles prepared in Example 1 was continuously irradiated under a 446 nm ultraviolet lamp for 60 min, and the fluorescence intensity was tested, as shown in Figure 16 . It was found that the fluorescence intensity remained unchanged all the time, indicating that the fluorescent silicon nanoparticles have excellent anti-photobleaching properties.

[0123] The above results show that the fluorescent silicon nanoparticles have good photothermal properties and chemical stability.

[0124] This application also tested the use of fluorescent silicon nanoparticles with carmine. Specifically, equal volumes of carmine solutions of different concentrations were added to the silicon nanoparticle solution prepared in Example 1. The final concentrations of carmine were 0, 10, 20, 30, 40, 50, 60, 70, 80, and 90 μmol / L. The fluorescence intensity values ​​of the resulting solutions were tested, and the results are as follows. Figure 17 , Figure 18 As shown.

[0125] from Figure 17 It can be seen that the fluorescence intensity was significantly quenched after adding different concentrations of carmine solution to the silicon nanoparticle solution. As the concentration of carmine solution increased, the fluorescence intensity of the silicon nanoparticle solution continuously decreased.

[0126] Based on this, a new method for fluorescent detection of carmine was established, such as... Figure 18 As shown, when the concentration of the carmine solution is in the range of (0-90) μmol / L, there is a good linear relationship between F0-F and the concentration c of the carmine solution, and the linear fitting equation is F0-F=-6.1453+4.3537c(μmol / L), with a correlation coefficient R. 2 =0.9980, the limit of detection (LOD) is 0.056 μmol / L, which is far below the national allowable amount.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0128] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the embodiments claimed above can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing fluorescent silicon nanoparticles, characterized by, The application relates to a fluorescent silicon nanoparticle and a preparation method thereof. The silicon source, the reducing agent and water are mixed and reacted to obtain the fluorescent silicon nanoparticle. The silicon source is 3-aminopropyl triethoxysilane. The reducing agent is humic acid. The mixing comprises the following steps: after the reducing agent is dissolved in lye to prepare a reducing agent solution, the silicon source and the reducing agent solution are added into the water. The lye is a 1wt% sodium hydroxide solution. The concentration of humic acid in the reducing agent solution is 5mmol / L-20mmol / L. When the mixing is performed, the volume ratio of the silicon source, the reducing agent solution and the water is (0.5-0.8):(1.0-2.5):(2.5-3). The reaction comprises the following steps: after the mixing solution is obtained, the mixing solution is continuously stirred at a standard atmospheric pressure, a temperature of 10-40 DEG C and a rotating speed of 800-1200 rpm to perform the reaction, and the reaction time is 20-40 min.

2. The production method according to claim 1, wherein After the reaction is completed, the following steps are further included: The solution after the reaction is transferred into a dialysis bag with a molecular weight of 500-1000 Da to perform dialysis, and the purified fluorescent silicon nanoparticle is obtained.

3. The production method according to claim 1 or 2, characterized by, After the fluorescent silicon nanoparticle is obtained, the fluorescent silicon nanoparticle solution is obtained by diluting the fluorescent silicon nanoparticle with water, and the fluorescent silicon nanoparticle solution is stored in an environment with a temperature of 2-6 DEG C.

4. Fluorescent silicon nanoparticles, characterized in that, The fluorescent silicon nanoparticle is prepared by the preparation method of any one of claims 1-3.

5. The fluorescent silicon nanoparticles of claim 4, wherein, The fluorescent silicon nanoparticle presents green under the irradiation of 365nm ultraviolet light. The particle size of the fluorescent silicon nanoparticle is 2.2-3.0nm.

6. A water-soluble fluorescent security ink, characterized in that, The fluorescent silicon nanoparticle is prepared by the preparation method of any one of claims 1-5.

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