A lifetime signal combination coding method based on quantum dot solutions and its application

Abstract

This invention provides a lifetime signal combination encoding method based on quantum dot solutions. The encoding method includes the following steps: S1, preparing core-shell quantum dot solutions with transition metal element doping of different lifetimes according to different doping amounts; S2, combining quantum dot solutions with different lifetimes in different proportions to obtain quantum dot solutions with different lifetime encoding levels; using fluorescence lifetime imaging microscopy and phasor analysis, based on vector laws, to control the quantum dot lifetime levels, achieving precise design, prediction, and analysis; S3, using quantum dot solutions with different lifetime encoding levels as printing ink, printing encrypted patterns, resulting in clusters at different positions in the phasor diagram; S4, using another quantum dot ink as a key, superimposing it on the encrypted pattern of S3, causing changes in the cluster positions in the phasor diagram, and decoding the key positions to obtain the actual encrypted information.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation, and in particular to quantum dot solutions with different lifetimes, phasor analysis, and methods for encoding lifetime signals. Background Technology

[0002] The lifetime (τ) of a fluorescent substance refers to the time required for photons to decay to 1 / e of their original intensity. Unlike fluorescence intensity, fluorescence lifetime is an inherent property of the substance and is unaffected by concentration, excitation intensity, or other factors. Therefore, fluorescence lifetime imaging (FLI) has become a widely used technique. In practical applications, regardless of the type of fluorescence lifetime microscope used, the processing of fluorescence lifetime data is a crucial step. Traditionally, determining the fluorescence decay curve requires least-squares fitting analysis for each pixel in the image. This method requires selecting a suitable fitting model (e.g., single, double, triple exponential decay, or non-exponential decay) and acquiring a large number of photons (typically >1000) to achieve an effective fit. These limitations make the data analysis of fluorescence lifetime imaging very time-consuming.

[0003] Phasor analysis is a method to simplify lifetime information from raw fluorescence lifetime imaging, converting the decay signal of each pixel in the image into a point on the phasor diagram. This conversion is represented on the phasor diagram as a semicircular curve with a radius of 0.5 centered at (G=0.5, S=0), known as a semicircle. In the phasor semicircle, pixels exhibiting single exponential decay behavior are located on the semicircle, while pixels exhibiting multi-exponential decay behavior are located inside the semicircle. Multiple pixels with similar fluorescence decay characteristics are located in close regions on the phasor diagram, forming "phasor clusters," which facilitate data visualization and cluster analysis. An important characteristic of the phasor diagram is that the phasor endpoints corresponding to multi-exponential decay processes are located within the set formed by connecting the lifetime phasor endpoints of their respective single-exponential decay components, and the distance from the endpoints is inversely proportional to the intensity of their contribution. These characteristics play a crucial role in quantifying, visualizing, and clustering fluorescence lifetime data.

[0004] Current methods for processing fluorescence lifetime signals based on phasor analysis mainly focus on unmixing complex fluorescence lifetime signals in biological samples. However, existing methods suffer from several problems: difficulty in accurately designing, predicting, and interpreting complex fluorescence lifetime combinations; poor signal analysis accuracy; and low efficiency. Summary of the Invention

[0005] Therefore, those skilled in the art are dedicated to developing a method that can accurately design, predict, and analyze complex lifetime combination signals in order to obtain highly stable, fast, and intuitive lifetime combination signals.

[0006] To achieve the above objectives, the present invention provides a lifetime signal combination encoding method based on quantum dot solution, the encoding method comprising the following steps:

[0007] S1. Prepare core-shell quantum dot solutions with transition metal element doping of different lifetimes according to different doping amounts;

[0008] S2. Quantum dot solutions with different lifetimes are combined in different proportions to obtain quantum dot solutions with different lifetime codes. The quantum dot solutions with different lifetime codes are then used to control the quantum dot lifetime levels using fluorescence lifetime imaging microscopy and phasor analysis based on the vector rule, so as to achieve precise design, prediction and analysis.

[0009] S3. Using quantum dot solutions with different lifetime codes as printing ink, encrypted patterns are printed, and clusters appear at different positions in the phasor diagram.

[0010] S4. Using another quantum dot ink as a key, it is superimposed and printed on the encrypted pattern of S3. The cluster positions in the phasor diagram change. By decoding the position of the key, the real encrypted information is obtained.

[0011] In step S4, the cluster positions of the "key" in the phasor diagram and the cluster positions of the quantum dot solution printing inks with different levels of lifetime encoding in S3 follow the phasor addition rule.

[0012] In step S1, the transition metal doped core-shell quantum dots include at least one of zinc selenide / zinc sulfide core-shell quantum dots, manganese sulfide / zinc sulfide core-shell quantum dots, cadmium selenide / zinc sulfide core-shell quantum dots, and indium phosphide / zinc sulfide core-shell quantum dots.

[0013] In step S1, the transition metal elements include one or more of manganese, copper, zinc, silver, and cobalt.

[0014] In step S1, the core-shell quantum dots doped with transition metal elements of different lifetimes are large Stokes shift quantum dots of different lifetimes, ranging from microseconds to nearly milliseconds.

[0015] In step S2, the quantum dots with different lifetimes have the same number of photons under the same excitation intensity. Solutions with different lifetimes but the same number of photons are mixed in different volume ratios. Based on the vector addition principle in the semicircle, the positions of the quantum dot solutions with different lifetimes on the semicircle are designed and predicted.

[0016] Step S1 includes the following steps:

[0017] S11. Add zinc source and manganese source to solvent in different proportions to form a mixed solution, degas it, heat it and add selenium precursor solution, then add zinc precursor solution to obtain Mn:ZnSe core solution with different manganese ion doping amount.

[0018] S12. Degas the Mn:ZnSe core solutions with different manganese ion doping amounts obtained in step S11, and add Zn(OA)2-OT mixed precursor solution after heating. Keep warm for a period of time to obtain Mn:ZnSe / ZnS core-shell quantum dot solutions with different manganese ion doping amounts; that is, core-shell quantum dot solutions doped with transition metal elements with different lifetimes.

[0019] As one embodiment of the present invention, the ratio of zinc source to manganese source is 40-53:1-3, 10-15:1-3, 4-8:1-3, 1-5:1-3 and 1-3:1-3 to obtain core-shell quantum dots with transition metal elements doped with different lifetimes.

[0020] In S11, the concentration of the zinc source in the mixed solution is 0.01-0.03 mol / L, and the concentration of the manganese source is 0.0005-0.001 mol / L.

[0021] In S11, the zinc source includes at least one of zinc acetate, zinc stearate, zinc acetate, and zinc sulfate; the manganese source includes at least one of manganese oxide, manganese stearate, manganese acetate, and manganese dichloride.

[0022] In S11, the selenium precursor is prepared by ultrasonically dispersing selenium powder into a solvent (the solvent can be n-octadecene and / or oleylamine) to form a selenium solution with a concentration of 0.01-0.03 g / L.

[0023] In S11, zinc and sulfur precursors are prepared by the following method: zinc source is added to solvent for degassing treatment, heated to 300-305℃ and held for 10-30 min, cooled to 130-160℃ and sulfur source is added; wherein, sulfur source is at least one of n-octyl mercaptan, thioacetamide and sulfur powder.

[0024] In S11, the solvent is a mixed solution of n-octadecene and oleic acid, with a volume ratio of n-octadecene to oleic acid of 0.5-1.5:0.5-1.5.

[0025] As one embodiment of the present invention, step S11 includes the following steps:

[0026] S111. Preparation of zinc precursor: Mix zinc source, oleic acid and octadecene, stir and heat to 120-130℃ under a protective atmosphere and vacuum treatment, then reintroduce the protective atmosphere and heat to 280-300℃ and hold for 20-30 min, then cool to 250-260℃ to obtain zinc precursor.

[0027] Preparation of selenium precursor: Selenium powder, octadecene and oleylamine were mixed and ultrasonically treated to obtain selenium precursor;

[0028] S112. Preparation of Mn:ZnSe core quantum dot stock solution: Zinc source, octadecene and different amounts of manganese source are mixed separately, stirred under a protective atmosphere and heated to 120-130℃ for vacuum treatment, then the protective atmosphere is reintroduced and the temperature is raised to 280-300℃, selenium precursor is injected, and after holding at 300-320℃ for 5-10 min, zinc precursor solution is injected, and after holding at 300-320℃ for 5-10 min, after cooling to 75-85℃, Mn:ZnSe core quantum dot stock solutions with different manganese ion doping amounts are obtained.

[0029] S113. Purification of Mn:ZnSe core quantum dots: Mix the core quantum dot stock solution obtained in step S12 with n-hexane, add acetone or anhydrous ethanol to precipitate the quantum dots, collect the precipitate by centrifugation, and wash it multiple times with a mixture of n-hexane and acetone to obtain purified Mn:ZnSe core solutions with different manganese ion doping amounts.

[0030] In step S111, the zinc source includes zinc oxide.

[0031] In step S112, the zinc source includes zinc stearate; the manganese source includes manganese stearate.

[0032] As one embodiment of the present invention, step S12 includes the following steps:

[0033] S121. Preparation of Zn(OA)2-OT mixed precursor solution: Zinc source, oleic acid and octadecene are mixed, stirred under a protective atmosphere and heated to 100-120℃ for vacuum treatment, then a protective atmosphere is introduced and the temperature is raised to 300-320℃ and held for 10-20 min, then cooled to 120-150℃ and sulfur source is injected and held at 120-150℃ to obtain Zn(OA)2-OT precursor solution;

[0034] S122. Preparation of Mn:ZnSe / ZnS core-shell quantum dots: The Mn:ZnSe core solutions with different manganese ion doping amounts obtained in step S1 are dissolved in octadecene. The solution is heated to 100-120℃ under a protective atmosphere and then vacuumed. Subsequently, a protective atmosphere is introduced and the temperature is raised to 300-320℃ to grow the ZnS shell. The Zn(OA)2-OT precursor solution from step S21 is injected into the core. After holding at 300-320℃ for 30-60 min, Mn:ZnSe / ZnS core-shell quantum dot solutions with different manganese ion doping amounts are obtained.

[0035] In S221, the sulfur source includes at least one of n-octyl mercaptan, thioacetamide, and sulfur powder; the zinc source includes at least one of zinc acetate, zinc stearate, zinc acetate, and zinc sulfate; in the Zn(OA)2-OT precursor solution, the concentration of the zinc source is 0.01-0.03 mol / L, and the concentration of the sulfur source is 0.0005-0.001 mol / L.

[0036] And / or, the volume ratio of octadecene to oleic acid is 0.5-1.5:0.5-1.5.

[0037] In another embodiment of the present invention, step S2 includes the following steps:

[0038] S21. Preparation of Zn(OA)2-OT mixed precursor solution: Zinc oxide, oleic acid and octadecene are mixed, stirred under a protective atmosphere and heated to 100-120℃ for vacuum treatment, then a protective atmosphere is introduced and the temperature is raised to 300-320℃ and held for 10-20 min, then cooled to 120-150℃ and n-octyl mercaptan is injected and held at 120-150℃ to obtain Zn(OA)2-OT precursor solution;

[0039] S22. Preparation of Mn:ZnSe / ZnS core-shell quantum dots: The Mn:ZnSe core solutions with different manganese ion doping amounts obtained in step S1 are dissolved in octadecene. The solution is heated to 100-120℃ under a protective atmosphere and then vacuumed. Subsequently, a protective atmosphere is introduced and the temperature is raised to 300-320℃ to grow the ZnS shell. The Zn(OA)2-OT precursor solution from step S21 is injected into the core. After holding at 300-320℃ for 30-60 min, Mn:ZnSe / ZnS core-shell quantum dot solutions with different manganese ion doping amounts are obtained.

[0040] The protective atmosphere mentioned above includes inert gases such as nitrogen and argon.

[0041] Step S2 includes the following steps:

[0042] S21. Quantum dot solutions with different lifetimes are excited by the same excitation light (405nm) and their concentrations are adjusted using a diluent (toluene) to make the number of photons emitted consistent.

[0043] S22. Take quantum dot solutions with the same number of photons but different lifetimes and place them on a fluorescence lifetime imaging microscope for detection. Collect lifetime signals and convert them into clusters on a phasor semicircle, which are defined as the first-order lifetime code of the quantum dot solution.

[0044] S23. Two different quantum dot solutions with primary lifetime encoding are mixed in a specific volume ratio to obtain a quantum dot mixed solution with secondary lifetime encoding. A quantum dot smear is prepared and placed on a fluorescence lifetime imaging microscope for detection. The lifetime signal is collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0045] S24. The quantum dot solutions with primary lifetime encoding and secondary lifetime encoding are mixed in different volume ratios to obtain the quantum dot solution with tertiary lifetime encoding. The quantum dot smears are then placed on a fluorescence lifetime imaging microscope for detection. The lifetime signals are collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0046] S25. Select at least two different levels of lifetime-encoded quantum dot solutions and mix them in various combinations and different volume ratios to obtain a multi-level composite lifetime-encoded quantum dot solution. Make a quantum dot smear of the solution and place it on a fluorescence lifetime imaging microscope for detection. Collect lifetime signals and convert them into clusters on a phasor semicircle. Each cluster represents a unique combination of lifetime information to achieve more complex and diverse lifetime encoding.

[0047] As one embodiment of the present invention, step S2 includes the following steps:

[0048] S21. The concentration of quantum dot solutions with different lifetimes was adjusted by using a diluent (toluene) under excitation light (405nm) to make the number of emitted photons consistent.

[0049] S22. Take quantum dot solutions with the same number of photons but different lifetimes and place them on a fluorescence lifetime imaging microscope for detection. Collect lifetime signals and convert them into clusters on a phasor semicircle, which are defined as the first-order lifetime code of the quantum dot solution.

[0050] S23. Two different quantum dot solutions with primary lifetime encoding are mixed in a specific volume ratio to obtain a quantum dot mixed solution with secondary lifetime encoding. A quantum dot smear is prepared and placed on a fluorescence lifetime imaging microscope for detection. The lifetime signal is collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0051] S24. The quantum dot solutions with primary lifetime encoding and secondary lifetime encoding are mixed in different volume ratios to obtain the quantum dot solution with tertiary lifetime encoding. The quantum dot smears are then placed on a fluorescence lifetime imaging microscope for detection. The lifetime signals are collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0052] S25. Two different quantum dot solutions with secondary lifetime encoding are mixed in different volume ratios to obtain a quantum dot solution with quaternary lifetime encoding. Quantum dot smears are prepared and placed on a fluorescence lifetime imaging microscope for detection. The lifetime signals are collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0053] S26. Quantum dot solutions with second-order lifetime coding and third-order lifetime coding are mixed in different volume ratios to obtain quantum dot solutions with fifth-order lifetime coding. Quantum dot smears are prepared and placed on a fluorescence lifetime imaging microscope for detection. The lifetime signals are collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0054] S27. Mix two different quantum dot solutions with tertiary lifetime encoding at different volume ratios; or mix three different quantum dot solutions with secondary lifetime encoding at different volume ratios to obtain a quantum dot solution with sixth lifetime encoding. Place the solution on a fluorescence lifetime imaging microscope for detection, collect lifetime signals and convert them into clusters on a phasor semicircle, with each cluster representing different lifetime information.

[0055] Step S3 includes the following steps:

[0056] S31. Quantum dot solutions with different levels of lifetime coding are named as four-digit numbers according to the "intensity / lifetime" method, where the first two digits represent fluorescence intensity and the last two digits represent fluorescence lifetime.

[0057] S32. Select at least two quantum dot solutions as inks and print a specific pattern according to the printing schematic diagram;

[0058] S33. Perform intensity imaging on the printed pattern to obtain intensity encryption information based on the difference in fluorescence intensity of the quantum dot solution;

[0059] S34. Perform lifetime imaging on the printed pattern and combine it with phasor analysis to obtain lifetime clusters. By performing a "gate" operation on the lifetime clusters of a specific quantum dot solution, lifetime encryption information based on the fluorescence lifetime difference of the quantum dot solution is obtained.

[0060] Step S4 includes the following steps:

[0061] S41. Select four quantum dot solutions with different lifetime encodings as printing inks and name them A, B, C and D respectively;

[0062] Among them, quantum dot solutions A, B, and D have different lifetimes but the same number of photons; C is obtained by mixing A and B.

[0063] S42. Print the pattern according to the encrypted pattern design using a high-precision nanomaterial deposition inkjet printing system;

[0064] S43. According to the vector rule of the phasor diagram, when quantum dot solutions A and B with different lifetimes but the same number of photons are mixed in equal proportions, the position of the mixed solution C in the phasor diagram is located at the midpoint of the line connecting A and B; this shows that the position of C can be determined by the known properties of solutions A and B and the rules of the phasor diagram.

[0065] S44. Introduce another quantum dot solution with a different lifetime as the "key" to decipher the mystery, and name it K. Theoretically, when K and A, which have different lifetimes but the same number of photons, are mixed in equal proportions to form a mixture F, then F is located at the midpoint of the line connecting A and K in the phasor diagram; when K and D, which have the same number of photons, are mixed in equal proportions to form a mixture E, E is located at the midpoint of the line connecting A and K; when B and K are mixed in equal proportions to obtain a mixture G, G is located at the midpoint of the line connecting B and K in the phasor diagram.

[0066] S45. Dilute or concentrate the four quantum dot solutions with different lifetimes (K, A, B, and D) from step S44 so that the number of photons satisfies A = B = D = K.

[0067] S46. The K ink from step S44 is superimposed and printed onto the encrypted pattern from step S42; based on the vector rules of the phasor diagram, the cluster positions of the phasor diagram change: A is converted to F, B is converted to G, D is converted to E, and C is converted to E; thus, the encrypted pattern is further encrypted.

[0068] S47. By decoding the location of cluster E, the true information "SJTU" is obtained.

[0069] This invention prepares smears of quantum dot solutions with different lifetimes, and uses fluorescence lifetime imaging microscopy and phasor analysis based on the vector rule to control the lifetime levels of quantum dots, thereby achieving precise design, prediction and analysis.

[0070] The phasor analysis method is a data processing method for fluorescence lifetime signals.

[0071] The phasor analysis method can directly convert the lifetime information of each pixel in the fluorescence intensity imaging image into a point in the phasor image.

[0072] The phasor diagram is a semicircle with G as the horizontal axis, ranging from 0 to 1, and S as the vertical axis, ranging from 0 to 0.5.

[0073] Each point in the semicircle represents a corresponding lifespan information. The lifespan decreases from left to right. The (0,0) coordinate represents an infinite lifespan, and the (0,1) coordinate represents an infinitely small lifespan.

[0074] The lifetime information on the semicircle compass follows the vector addition rule. Geometrically, the phasor endpoints corresponding to the two lifetime mixed materials should be located on the line connecting the lifetime phasor endpoints corresponding to each lifetime material, and the distance from the endpoints is determined by the proportion of the two components.

[0075] Quantum dot solutions with different lifetimes were used as printing inks, and encrypted patterns were printed using a high-precision nanomaterial inkjet deposition printing system, resulting in clusters appearing at different positions in the phasor diagram.

[0076] Using a quantum dot ink as the "key K," which is overlaid on the previous encrypted pattern, the cluster positions in the phasor diagram change. By decoding the position of the "key," the real encrypted information can be obtained.

[0077] The "key" is a quantum dot ink with a different lifetime. When it is superimposed on the previous pattern, due to the combination of multiple fluorescence lifetimes and the additive rules in the phasor diagram, the positions of the clusters at three different locations change, thereby achieving encryption and decoding.

[0078] According to another aspect of the present invention, a fluorescence lifetime analysis method based on the combination of fluorescence lifetime imaging microscopy and phasor analysis as described above is also provided. The method can be used to accurately design, predict and analyze the lifetime signals of quantum dot solutions with different lifetime codes, and realize a multi-level lifetime combination encoding method through hierarchical control.

[0079] According to another aspect of the present invention, a dynamic encryption strategy based on the phasor addition rule of "lifetime + strength" is also provided for use in the field of anti-counterfeiting encryption.

[0080] The application of the lifetime signal combination encoding method based on quantum dot solution in the field of anti-counterfeiting encryption is also within the scope of protection of this invention.

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] 1. This invention provides a method for preparing quantum dot solutions with different lifetime codes. By changing the amount of transition metal elements added during the quantum dot preparation process, quantum dot solutions with different lifetimes can be obtained.

[0083] 2. This invention utilizes fluorescence lifetime imaging microscopy and phasor analysis techniques, combined with the vector addition rule in a semicircular compass, to mix quantum dot solutions with different lifetimes in a specific ratio. Through hierarchical control, it enables the design, prediction, and analysis of lifetime combination signals.

[0084] 3. This method is a visual fluorescence lifetime analysis approach that does not require fitting, and it is much faster than traditional fitting methods. Furthermore, it can present pixels with similar decay characteristics as "phasor clusters," providing powerful data visualization capabilities and facilitating data clustering analysis. Using this method, dynamic encryption strategies based on fluorescence intensity and lifetime can be implemented, which has significant implications and broad application prospects in the field of encryption and anti-counterfeiting. Attached Figure Description

[0085] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0086] Figure 1 These are TEM images of quantum dot nanoparticles obtained in Example 1 of this invention and lifetime decay curves of six different quantum dots with different lifetimes; (where a is an electron microscope image of the quantum dots; b is a lifetime decay curve of six different manganese-doped quantum dots).

[0087] Figure 2 This is a first-order lifetime encoded phasor cluster diagram of six different lifetime quantum dot solutions obtained in Example 2 of the present invention;

[0088] Figure 3 This is a phasor cluster diagram of the quantum dot solution obtained in Example 3 of the present invention, from second-level lifetime coding to sixth-level lifetime coding; where a is second-level coding, which can be obtained from two first-level codings; b is third-level coding, which can be obtained from first-level coding and second-level coding; c is fourth-level coding and fifth-level coding, where fourth-level coding can be obtained from two second-level codings, and fifth-level coding can be obtained from second-level coding and third-level coding; d and e are both sixth-level coding, where diagram d is obtained from three second-level codings, diagram e is obtained from two third-level codings, and f is an integrated diagram of all coding clusters from first-level to sixth-level.

[0089] Figure 4 This is a two-dimensional "strength + lifetime" encryption strategy diagram obtained in Embodiment 4 of the present invention; wherein:

[0090] a is a schematic diagram of a printing design using two quantum dot inks, 0101 and 0102, which have the same strength but different lifespans;

[0091] b shows the actual printing results using two quantum dot inks, 0101 and 0102, which have the same strength but different lifespans.

[0092] c is a schematic diagram of a printing design using four types of quantum dot inks: 0101, 0102, 0201, and 0202.

[0093] Image d shows the actual printing results using four types of quantum dot inks: 0101, 0102, 0201, and 0202.

[0094] e is the phasor result diagram of the phasor analysis performed on the results of Figure b;

[0095] f is the phasor result diagram of the phasor analysis performed on the results of figure d;

[0096] g is used to identify the decoding clusters in graph e, which can yield the true information graph;

[0097] h represents the identification of the decoding clusters in Figure f, which yields the true information map;

[0098] Figure 5 This is a diagram of the dynamic encryption and anti-counterfeiting strategy obtained in Embodiment 5 of this invention; wherein:

[0099] 'a' is a schematic diagram of dynamic encryption anti-counterfeiting, which includes the four types of inks used for printing: A, B, C, and D.

[0100] b is a schematic diagram of an encryption pattern designed using four types of quantum dot inks, A, B, C, and D. Print out the design using A, B, C, and D.

[0101] c is the in-situ superposition of key ink K onto image b to obtain the true information image;

[0102] d represents the phasor analysis of the actual printed pattern designed according to diagram b;

[0103] e assigns different pseudocolors to the four clusters A, B, C, and D in Figure d to obtain the corresponding phasor pseudocolor superposition encryption map;

[0104] f is a pseudo-color image of the individual phasors for the clusters corresponding to the four quantum dot inks A, B, C, and D in Figure d;

[0105] Figure g is the phasor diagram of the key ink K;

[0106] Figure h shows the phasor diagram obtained by overlaying the printed key ink K in situ onto the encrypted pattern in Figure e.

[0107] Figure i shows the phasor pseudocolor pattern for the clusters corresponding to the four quantum dot inks E, F, and G in Figure h, where E represents the real information. Detailed Implementation

[0108] The following description further illustrates the structures involved in this invention and the technical terms used therein. These descriptions are merely illustrative of how the invention is implemented and do not constitute any limitation on the invention. The scope of the invention is defined and expressed by the claims.

[0109] organic solvents

[0110] Organic solvents are a large class of organic compounds widely used in daily life and production. They have relatively small molecular weights and are found in paints, adhesives, varnishes, and cleaning agents. Commonly used organic solvents include styrene, perchloroethylene, trichloroethylene, ethylene glycol ether, and triethanolamine. Organic solvents can dissolve some water-insoluble organic compounds (such as oils, waxes, resins, rubber, and dyes). They are characterized by being liquid at room temperature and pressure, having high volatility, and maintaining the properties of both the solute and solvent unchanged during dissolution. Solvents do not chemically react with the solute and are therefore inert.

[0111] Inert organic solvents mainly include benzene, toluene, xylene, o-xylene, m-xylene, p-xylene, hexamethylbenzene, ethylbenzene, n-propylbenzene, isopropylbenzene, biphenyl, diphenylmethane, triphenylmethane, styrene, phenylacetylene, naphthalene, tetrahydronaphthalene, anthracene, phenanthrene, pyrene, chloroform, N-methylpyrrolidone, diphenyl ether, acetone, methyl butyl ketone, methyl isobutyl ketone, cyclohexanone, isoflurane, diacetone alcohol, silicone, and tetraethylene glycol dimethyl ether. Ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, nitrobenzene, carbon tetrachloride, dichloroethane, chlorobenzene, dichlorobenzene, dichloromethane, chloropicrin, bromomethane, dichloropropane, dibromoethylene, trichloromethane, dimethyl sulfoxide, acetone, acetonitrile, dimethylformamide, carbon tetrachloride, cyclohexane, cyclohexanone, toluenecyclohexanone, pyridine, phenol, carbon tetrachloride, isooctane, diethyl ether, pentane, hexane, propylene oxide, etc.

[0112] In some embodiments, the organic solvent used in this invention to form the dispersed phase between the polymer and the organic solvent is one of toluene, ethylbenzene, chloroform, dichloromethane, acetone, acetonitrile, and diethyl ether.

[0113] quantum dots

[0114] Quantum dots are semiconductor nanostructures that confine excitons in three spatial directions. Sometimes referred to as "artificial atoms," "superlattices," "superatoms," or "quantum dot atoms," they are a new concept proposed in the 1990s. Quantum dots are semiconductor nanocrystals with radii smaller than or close to the Bohr exciton radius. Due to their unique fluorescent nanoeffects, they exhibit a broad and continuously distributed excitation spectrum, a narrow and symmetrical emission spectrum, and the emission wavelength can be tuned by changing the particle size and composition. They possess strong fluorescence intensity, slow bleaching rate, and high sensitivity, making them widely used in photocatalysis, photosensitive sensors, luminescent materials, and fluorescent probe labeling. In particular, quantum dots composed of Group IIB and Group VIA elements (such as CdSe) have significant value in biomedical fluorescent probe labeling and sensors due to their exceptionally good fluorescence emission properties in the visible and near-infrared spectral regions. Quantum dots possess separated quantized energy spectra. The corresponding wavefunctions are spatially located within the quantum dot but extend across several lattice periods. A quantum dot has a small number (1-100) of integer numbers of electrons, holes, or electron-hole pairs, meaning that the amount of charge it carries is an integer multiple of the elementary charge. Quantum dots mainly include CdSe / ZnS, CdSe / CdS, CdTeSe / ZnS, CdTe / CdSe / ZnS, CdTe, Ag2S, Ag2Se, InAs, InP, HgTe, PbS, PbSe, CuInS2, CuInSe2, CdSeTe, CdHgTe, InP / ZnS, InAs / CdSe, C dTe / CdS, CdTe / ZnS, CdTe / CdSe, ZnTe / CdTe, ZnTe / CdSe, ZnTe / CdS, CdSeTe / CdS, Cu :CdS / ZnS, Mn:ZnSe / ZnS, CuInS2 / ZnS, CuInSe2 / ZnS, CsPbCl3, CsPbBr3, CsPbI3, Cs Pb(Cl / Br)3, CsPb(Br / I)3, CH3NH3PbI3, CH3NH3PbBr3, CdSe, CdS, ZnSe, ZnTe, ZnO, HgSe, HgS, CaAs, InCaAs, CdSe / ZnSe, CdS / ZnS, CdS / Ag2S, CdS / Cd(OH)2, CdSe / ZnSe , CdS / HgS, CdS / HgS / CdS, ZnS / CdS, ZnS / CdS / ZnS, ZnS / HgS / ZnS / CdS, CdSe / CuSe, Cd SeTe / CdS / ZnS, CdSe / CdS / ZnS, CdS:Mn, ZnS:Mn, CdS:Cu, ZnS:Cu, CdS:Tb, ZnS:Tb, etc.

[0115] In some embodiments, the quantum dots with different lifetimes in this invention mainly include (CdSe / ZnS, CdSe / CdS, CdTeSe / ZnS, CdTe / CdSe / ZnS, CdTe, Ag2S, Ag2Se, InAs, InP, HgTe, PbS, PbSe, CuInS2, CuInSe2, CdSeTe, CdHgTe, InP / ZnS, InAs / CdSe, CdTe / CdS, CdTe / ZnS) , CdTe / CdSe, ZnTe / CdTe, ZnTe / CdSe, ZnTe / CdS, CdSeTe / CdS, Cu:CdS / ZnS, Mn:ZnSe / ZnS, CuInS2 / ZnS, CuInSe2 / ZnS, CsPbCl3, CsPbBr3, CsPbI3, CsPb(Cl / Br)3, CsPb(Br / I)3, CH3NH3PbI3, CH3NH3PbBr3), etc.

[0116] Example 1: Preparation of core-shell quantum dot solutions doped with transition metals of different lifetimes

[0117] The quantum dots prepared in this embodiment are Mn:ZnSe / ZnS, and the specific preparation steps are as follows:

[0118] (1) Take 406.9 mg of zinc oxide, 7.05 mL of oleic acid and 12.95 mL of octadecene, place them in a three-necked glass flask, heat to 120 °C under nitrogen protection and magnetic stirring, and evacuate for 1 h. After re-introducing nitrogen, heat to 280 °C, hold for 20 min, and then cool to 250 °C to obtain the zinc oleate precursor.

[0119] (2) Take 156 mg of selenium powder, 5.6 mL of octadecene and 2.4 mL of oleylamine into a centrifuge tube, and mix them by sonication for 5 min to obtain the selenium precursor.

[0120] (3) Take 243 mg of zinc stearate, 20 mL of octadecene, and (5 mg, 10 mg, 20 mg, 40 mg, 80 mg, 160 mg) of manganese stearate respectively in a three-necked glass flask. Under nitrogen protection and magnetic stirring, heat to 120 °C and evacuate for 1 h. Introduce nitrogen and heat to 300 °C, then rapidly inject selenium precursor. Hold at 300 °C for 5 min, then inject 1.6 mL of zinc oleate precursor solution dropwise. Cool to 200 °C, then inject 1.6 mL of zinc oleate precursor dropwise. Heat to 260 °C and hold for 10 min, then inject 1.6 mL of zinc oleate precursor dropwise again. After 10 min, inject 1.6 mL of zinc oleate precursor for the third time, hold for 5 min, and then cool to obtain Mn:ZnSe core quantum dot stock solutions with different manganese ion doping amounts.

[0121] (4) Add 25 mL of n-hexane to the Mn:ZnSe core quantum dot stock solutions with different manganese ion doping amounts from step (3), mix well, and then add a large amount of acetone to precipitate the quantum dots in the stock solution. Centrifuge at 10,000 rpm for 5 min. Then wash three times with a mixture of n-hexane and acetone at a volume ratio of 2:7, centrifuging at 10,000 rpm for 5 min each time. Collect the precipitate, disperse the purified Mn:ZnSe core quantum dots with different manganese ion doping amounts in toluene, and store at 4℃ for later use.

[0122] (5) Take 781 mg of zinc oxide, 9 mL of oleic acid and 22.5 mL of octadecene, place them in a three-necked glass flask, heat to 100 °C under nitrogen protection and magnetic stirring, start vacuuming while continuing to heat to 120 °C, vacuum for 30 min, then introduce nitrogen gas, heat to 315 °C and hold for 15 min. Finally, cool the reaction solution to 150 °C, inject 3.2 mL of n-octyl mercaptan (OT), and keep at 150 °C for later use to obtain a mixed precursor solution of zinc oleate and OT (Zn(OA)2-OT precursor solution).

[0123] (6) Centrifuge the toluene solutions of Mn:ZnSe core quantum dots with different manganese ion doping amounts from (4) at low speed, and dissolve the supernatant in 10 mL of octadecene. Under nitrogen protection and magnetic stirring, heat to 100℃, evacuate for 30 min, introduce nitrogen, and heat to 310℃ to grow the ZnS shell. Inject 9 mL of the Zn(OA)2-OT precursor solution from step (5) at an injection rate of 6 mL / h using a syringe pump, and keep warm at 310℃ for 30 min to obtain Mn:ZnSe / ZnS core-shell structure quantum dots with different manganese ion doping amounts. When cooled to 80℃, wash with hexane and acetone (volume ratio of 2:7) by centrifugation. The centrifugation and washing method is the same as in step (4). Finally, dissolve the purified quantum dots in toluene and store at 4℃. The TEM image is shown below. Figure 1 As shown (where a is a high-resolution electron microscope image of the quantum dots; b is the lifetime decay curve of six different manganese-doped quantum dots).

[0124] (7) Through Figure 1 It can be found that by changing the amount of manganese stearate doping, six different quantum dot solutions with different lifetime decay curves can be obtained.

[0125] Example 2: Level 1 Lifetime Coding

[0126] (1) The six quantum dot solutions with different lifetimes in Example 1 were diluted with toluene. Under the excitation of 405nm excitation light, the concentration was adjusted (so that the final concentration was 10mg / mL) to make the number of emitted photons consistent.

[0127] (2) Six quantum dot solutions with the same number of photons but different lifetimes were each coated with 10 μL onto a coverslip to form quantum dot smears, which were then examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water mirror, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channel was 615 / 40 nm.

[0128] (3) Fluorescence imaging was performed on regions of uniform quantum dot emission, and lifetime signals were collected using the FastFLIM FLIMbox from ISS. After imaging, the fluorescence images were directly converted into six types of clusters on a phasor semicircle using SimFCS-64 software (e.g., Figure 2 This is defined as the first-order lifetime encoding of quantum dot solutions, i.e. Figure 2 QDt 11 -QDt 16 Six quantum dot lifetime-encoded clusters.

[0129] Example 3: Multi-level lifetime coding

[0130] (1) According to the vector rule of the phasor semicircle, when the photon numbers of two quantum dot solutions with first-order lifetime encoding are the same, their cluster positions on the semicircle are known. For example, two quantum dot solutions with first-order lifetime encoding, namely QDt... 11 -QDt 16 When any two quantum dots are mixed in different volume ratios, the resulting sample's cluster position on a semicircular compass lies on the line connecting the clusters of the two solutions before mixing, and is equidistant from both sides. This is defined as a second-order lifetime encoding. Similarly, based on this principle, hierarchical design and control of quantum dot solution lifetimes can be achieved.

[0131] (2) For secondary lifetime coding, QDt is divided into volumes of 5:1, 4:2, 3:3, 2:4 and 1:5. 11 and QDt 16 Two quantum dot solutions were mixed to obtain five quantum dot mixed solutions, which were named QDt. 21 QDt 22 QDt 23 QDt 24 and QDt 25 ;

[0132] QDt was prepared at a 1:1 volume ratio. 13 and QDt 14 The two quantum dot solutions were mixed and named QDt. 26 ;

[0133] QDt was prepared at a 1:1 volume ratio. 12 and QDt 13The two quantum dot solutions were mixed and named QDt. 27 ,

[0134] All quantum dot solutions were prepared into quantum dot smears and examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water mirror, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channel was 615 / 40 nm. The fluorescence imaging images were directly converted into clusters on a phasor semicircle using SimFCS-64 software, such as... Figure 3 As shown in the secondary encoding in 'a', each cluster represents different lifetime information.

[0135] (3) For the three-level lifetime coding, the first-level coding obtained in Example 2 and the second-level coding obtained in step (2) of Example 3 are mixed according to different volume ratios.

[0136] like Figure 3 The three-level encoding in b is shown below:

[0137] Quantum dot solution QDt was mixed at a volume ratio of 1:1. 13 and QDt 21 The third-level lifetime code QDt is obtained. 31 ;

[0138] Quantum dot solution QDt was mixed at a volume ratio of 1:1. 14 and QDt 25 The third-level lifetime code QDt is obtained. 32 ;

[0139] All quantum dot solutions were prepared into quantum dot smears and examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water microscope, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channels were 615 / 40 nm. The fluorescence images were directly converted into clusters on a phasor semicircle using SimFCS-64 software, representing different lifetime information.

[0140] (4) For the fourth-level lifetime coding, any two second-level codes obtained in step (2) of Example 3 are mixed according to different volume ratios.

[0141] like Figure 3 As shown in c, the quantum dot solution QDt is mixed at a volume ratio of 2:1. 26 and QDt 23 Quantum dot smears were fabricated to obtain fourth-level lifetime encoded QDt. 41The samples were examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water mirror, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channels were 615 / 40 nm. The fluorescence images were directly converted into clusters on a phasor semicircle using SimFCS-64 software, representing different lifetime information.

[0142] (5) For the five-level lifetime coding, the second-level coding obtained in step (2) of Example 3 and the third-level coding obtained in step (3) can be mixed in different volume ratios.

[0143] like Figure 3 As shown in c, quantum dot solutions QDt are mixed at a volume ratio of 1:1. 26 and QDt 31 The five-level lifetime code QDt is obtained. 51 Quantum dot smears were prepared and examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water microscope, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channels were 615 / 40 nm. The fluorescence images were directly converted into clusters on a phasor semicircle using SimFCS-64 software, representing different lifetime information.

[0144] (6) For Level 6 lifetime coding.

[0145] The three different secondary codes obtained in step (2) of Example 3 are mixed in different volume ratios to obtain a six-level lifetime code; such as Figure 3 As shown in d, the quantum dot solution QDt can be mixed in a volume ratio of 1:1:1. 22 QDt 24 and QDt 26 By mixing, a six-level lifetime code QDt is obtained. 61 ;

[0146] The two types of tertiary coding obtained in step (3) are mixed in different volume ratios to obtain a 6th lifetime coding quantum dot solution. For example... Figure 3 As shown in e, the quantum dot solution QDt is mixed in volume ratios of 2:1 and 1:2. 31 and QDt 32 By mixing, a six-level lifetime code QDt is obtained. 62 and QDt 63Quantum dot solutions were prepared into quantum dot smears, which were then examined using a fluorescence lifetime imaging microscope. The objective lens was a 60x water mirror, the excitation light was 405 nm, the excitation frequency was 1000 Hz, the detector was an APD detector, and the fluorescence channels were 615 / 40 nm. The fluorescence images were directly converted into clusters on a phasor semicircle using SimFCS-64 software, representing different lifetime information. All quantum dot lifetime-coded clusters from level one to level six are shown below. Figure 3 f.

[0147] Example 4

[0148] Two quantum dot solutions were selected, one for primary encoding QDt. 14 Quantum dot solutions and secondary coding QDt 26 Quantum dot solutions are named using the four-digit number "0000" according to their "strength / lifetime" (QDt). 14 For "0101", QDt 26 "0102" represents QDt 14 and QDt 26 The fluorescence intensity is consistent, both being "01"; however, the fluorescence lifetimes are different, QDt 14 The lifetime is "01", QDt 26 Its lifespan is "02".

[0149] (1) QDt 14 “0101” and QDt 26 Using “0102” as ink, print the pattern “8888” according to the printing diagram.

[0150] (2) Perform intensity imaging on “8888” to obtain the intensity encryption information of “8888”.

[0151] (3) Lifetime imaging of “8888” was performed, and phasor analysis was further combined to obtain two lifetime clusters. By analyzing the lifetime cluster QDt 26 The "circle gate" reveals the encrypted lifespan information for "2024".

[0152] (4) Select four quantum dot solutions (two different concentrations of QDt) 14 and two different concentrations of QDt 26 As ink,

[0153] The four-digit number "0000" is named according to "strength and lifespan".

[0154] Solution 1 (QDt) 14 The value is "0101", and the solution is QDt. 26 The value is "0102", and the solution is QDt. 14 The value is "0201", and the solution is QDt.26 The value is "0202", and the solution is QDt. 14 ) and solution two (QDt) 26 The fluorescence intensity of the solutions was consistent, both showing "01", and the solution tri(QDt) showed the same fluorescence intensity. 14 ) and solution four (QDt) 26 The fluorescence intensity of the solutions was consistent, both showing "02", and the solution was QDt. 14 ) and solution three (QDt) 14 The fluorescence lifetimes of the solutions were consistent, both being "01", and solution 2 (QDt) was also consistent. 26 ) and solution four (QDt) 26 The fluorescence lifetimes of all of them are consistent, both being "02".

[0155] (5) Use solution one "0101", solution two "0102", solution three "0201" and solution four "0202" as ink to print the pattern "8888" according to the printing diagram.

[0156] (6) Perform intensity imaging on “8888” to obtain the intensity encryption information of “1111”.

[0157] (7) Lifetime imaging of “8888” was performed, and phasor analysis was further combined to obtain two lifetime clusters. The lifetime clusters QDt were analyzed. 26 The "circle gate" yields the encrypted lifespan information of "1896".

[0158] Figure 4 This is the two-dimensional "strength + lifetime" encryption strategy obtained in this embodiment; Figure 4 This is a two-dimensional "strength + lifetime" encryption strategy diagram obtained in Embodiment 4 of the present invention; wherein:

[0159] a is a schematic diagram of a printing design using two quantum dot inks, 0101 and 0102, which have the same strength but different lifespans;

[0160] b shows the actual printing results using two quantum dot inks, 0101 and 0102, which have the same strength but different lifespans.

[0161] c is a schematic diagram of a design for printing using four types of quantum dot inks: 0101, 0102, 0201, and 0202.

[0162] Image d shows the actual printing results using four types of quantum dot inks: 0101, 0102, 0201, and 0202.

[0163] e is the phasor result diagram of the phasor analysis performed on the results of Figure b;

[0164] f is the phasor result diagram of the phasor analysis performed on the results of figure d;

[0165] g is used to identify the decoding clusters in graph e, which can yield the true information graph;

[0166] h is used to identify the decoding clusters in Figure f, which can yield the true information map.

[0167] Example 5

[0168] Four quantum dot solutions with different lifetimes (QDt) were selected. 14 ,QDt 63 ,QDt 13 and QDt 41 As printing inks, they are named A, B, C, and D respectively. The photon counts of A, B, and D are adjusted to be consistent. C is obtained by mixing A and B with the same photon count and volume. The pattern is printed according to the encrypted pattern design drawing through a high-precision nanomaterial deposition inkjet printing system.

[0169] (1) According to the vector rule of the phasor diagram, when quantum dot solutions A and B with different lifetimes but the same number of photons are mixed in equal proportions, the position of the mixed solution C in the phasor diagram is located at the midpoint of the line connecting A and B. Similarly, when quantum dot solutions "key K" with different lifetimes but the same number of photons are mixed in equal proportions with A, the position of the mixed solution F in the phasor diagram is located at the midpoint of the line connecting A and "key K". Likewise, the position of E can be determined from "key K" and D, and the position of G can be determined from "key K" and B.

[0170] (2) Using quantum dot solutions with lifetimes different from A, B, C, and D as “key K”, the number of photons of the three quantum dot printing inks with different lifetimes in step (1) and the “key K” ink is adjusted so that the number of photons satisfies A = B = D = K.

[0171] (3) The “key K” ink from step (2) is superimposed and printed on the encryption pattern of step (1). Due to the vector rules of the phasor diagram described in step (2), the following changes are achieved at the cluster position of the phasor diagram: A is converted to F, B is converted to G, D is converted to E, and C is also converted to E.

[0172] (4) By decoding the location of cluster E, the real information “SJTU” is obtained.

[0173] Figure 5This is a diagram of the dynamic encryption anti-counterfeiting strategy obtained in Embodiment 5 of this invention; where a is a schematic diagram of dynamic encryption anti-counterfeiting, including four inks A, B, C and D used for printing; b is a schematic diagram of the encryption pattern designed using four quantum dot inks A, B, C and D. A, B, C and D are used to print the pattern b according to the design, and then key ink K is superimposed in situ to obtain the real information pattern c. c is the actual printed pattern designed according to the left image of b. d is the phasor analysis performed on the actual printed pattern, assigning different pseudo-colors to the four clusters A, B, C and D to obtain the corresponding phasor pseudo-color superposition pattern e. f is the individual phasor pseudo-color pattern for the clusters corresponding to the four quantum dot inks A, B, C and D in figure d; g is the phasor pattern of key ink K; h is the phasor pattern obtained by superimposing key ink K in situ on the encryption pattern in figure e; i is the phasor pseudo-color pattern for the clusters corresponding to the four quantum dot inks E, F and G in figure h, where E represents the real information.

[0174] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A lifetime signal combination encoding method based on quantum dot solution, characterized in that, The encoding method includes the following steps: S1. Prepare core-shell quantum dot solutions with transition metal element doping of different lifetimes according to different doping amounts; S2. Quantum dot solutions with different lifetimes are combined in different proportions to obtain quantum dot solutions with different lifetime encoding levels. The quantum dot solutions with different lifetime encoding levels are then used to control the quantum dot lifetime levels using fluorescence lifetime imaging microscopy and phasor analysis based on the vector rule, so as to achieve precise design, prediction and analysis. S3. Using quantum dot solutions with different lifetime codes as printing ink, encrypted patterns are printed, and clusters appear at different positions in the phasor diagram. S4. Using another quantum dot ink as a key, it is superimposed and printed on the encrypted pattern of S3. The position of the clusters in the phasor diagram changes. By decoding the position of the key, the real encrypted information is obtained. Step S2 includes the following steps: S21. Under the same excitation light, quantum dot solutions with different lifetimes are adjusted in concentration using a diluent to make the number of emitted photons consistent. S22. Take quantum dot solutions with the same number of photons but different lifetimes and place them on a fluorescence lifetime imaging microscope for detection. Collect lifetime signals and convert them into clusters on a phasor semicircle, which are defined as the first-order lifetime code of the quantum dot solution. S23. Two different quantum dot solutions with primary lifetime encoding are mixed in a specific volume ratio to obtain a quantum dot mixed solution with secondary lifetime encoding. A quantum dot smear is prepared and placed on a fluorescence lifetime imaging microscope for detection. The lifetime signal is collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information. S24. The quantum dot solutions with primary lifetime encoding and secondary lifetime encoding are mixed in different volume ratios to obtain the quantum dot solution with tertiary lifetime encoding. The quantum dot smears are then placed on a fluorescence lifetime imaging microscope for detection. The lifetime signals are collected and converted into clusters on a phasor semicircle, with each cluster representing different lifetime information. S25. Select at least two different levels of lifetime-encoded quantum dot solutions and mix them in various combinations and different volume ratios to obtain a multi-level composite lifetime-encoded quantum dot solution. Make a quantum dot smear of the solution and place it on a fluorescence lifetime imaging microscope for detection. Collect lifetime signals and convert them into clusters on a phasor semicircle. Each cluster represents a unique combination of lifetime information to achieve more complex and diverse lifetime encoding.

2. The lifetime signal combination coding method according to claim 1, characterized in that, Step S1 includes the following steps: S11. Add zinc source and manganese source to solvent in different proportions to form a mixed solution, degas it, heat it and add selenium precursor solution, then add zinc precursor solution to obtain Mn:ZnSe core solution with different manganese ion doping amount. S12. Degas the Mn:ZnSe core solutions with different manganese ion doping amounts obtained in step S11, and add Zn(OA)2-OT mixed precursor solution after heating. Keep warm for a period of time to obtain Mn:ZnSe / ZnS core-shell quantum dot solutions with different manganese ion doping amounts; that is, core-shell quantum dot solutions doped with transition metal elements with different lifetimes.

3. The lifetime signal combination coding method according to claim 2, characterized in that, Step S11 includes the following steps: S111. Preparation of zinc precursor: Mix zinc source, oleic acid and octadecene, stir and heat to 120-130℃ under a protective atmosphere and vacuum treatment, then reintroduce the protective atmosphere and heat to 280-300℃ and hold for 20-30 min, then cool to 250-260℃ to obtain zinc precursor. Preparation of selenium precursor: Selenium powder, octadecene and oleylamine were mixed and ultrasonically treated to obtain selenium precursor; S112. Preparation of Mn:ZnSe core quantum dot stock solution: Zinc source, octadecene and different amounts of manganese source are mixed separately, stirred under a protective atmosphere and heated to 120-130℃ for vacuum treatment, then the protective atmosphere is reintroduced and the temperature is raised to 280-300℃, selenium precursor is injected, and after holding at 300-320℃ for 5-10 min, zinc precursor solution is injected, and after holding at 300-320℃ for 5-10 min, the temperature is lowered to 75-85℃ to obtain Mn:ZnSe core quantum dot stock solutions with different manganese ion doping amounts; S113. Purification of Mn:ZnSe core quantum dots: Mix the core quantum dot stock solution obtained in step S12 with n-hexane, add acetone or anhydrous ethanol to precipitate the quantum dots, collect the precipitate by centrifugation, and wash it multiple times with a mixture of n-hexane and acetone to obtain purified Mn:ZnSe core solutions with different manganese ion doping amounts.

4. The lifetime signal combination coding method according to claim 2, characterized in that, Step S12 specifically includes the following steps: S121. Preparation of Zn(OA)2-OT mixed precursor solution: Zinc source, oleic acid and octadecene are mixed, stirred under a protective atmosphere and heated to 100-120℃ for vacuum treatment, then a protective atmosphere is introduced and the temperature is raised to 300-320℃ and held for 10-20 min, then cooled to 120-150℃ and sulfur source is injected and held at 120-150℃ to obtain Zn(OA)2-OT precursor solution; S122. Preparation of Mn:ZnSe / ZnS core-shell quantum dots: The Mn:ZnSe core solutions with different manganese ion doping amounts obtained in step S1 are dissolved in octadecene. The solution is heated to 100-120℃ under a protective atmosphere and then vacuumed. Subsequently, a protective atmosphere is introduced and the temperature is raised to 300-320℃ to grow the ZnS shell. The Zn(OA)2-OT precursor solution from step S21 is injected into the core. After holding at 300-320℃ for 30-60 min, Mn:ZnSe / ZnS core-shell quantum dot solutions with different manganese ion doping amounts are obtained.

5. The lifetime signal combination coding method according to claim 4, characterized in that, In S121, the sulfur source includes at least one of n-octyl mercaptan, thioacetamide, and sulfur powder; And / or, the zinc source includes at least one of zinc acetate, zinc stearate, zinc acetate, and zinc sulfate.

6. The lifetime signal combination coding method according to claim 1, characterized in that, In step S21, the wavelength of the excitation light is 405 nm.

7. The lifetime signal combination coding method according to claim 1, characterized in that, Step S3 includes the following steps: S31. Quantum dot solutions with different levels of lifetime coding are named as four-digit numbers according to the "intensity / lifetime" method, where the first two digits represent fluorescence intensity and the last two digits represent fluorescence lifetime. S32. Select at least two quantum dot solutions as inks and print a specific pattern according to the printing schematic diagram; S33. Perform intensity imaging on the printed pattern to obtain intensity encryption information based on the difference in fluorescence intensity of the quantum dot solution; S34. Perform lifetime imaging on the printed pattern and combine it with phasor analysis to obtain lifetime clusters. By performing "gating" operations on the lifetime clusters of a specific quantum dot solution, lifetime encryption information based on the fluorescence lifetime difference of the quantum dot solution is obtained.

8. The lifetime signal combination coding method according to claim 1, characterized in that, Step S4 includes the following steps: S41. Select four quantum dot solutions with different lifetime encodings as printing inks and name them A, B, C and D respectively; Among them, quantum dot solutions A, B, and D have different lifetimes but the same number of photons; C is obtained by mixing A and B. S42. Print the pattern according to the encrypted pattern design using a high-precision nanomaterial deposition inkjet printing system; S43. According to the vector rule of the phasor diagram, when quantum dot solutions A and B with different lifetimes but the same number of photons are mixed in equal proportions, the position of the mixed solution C in the phasor diagram is located at the midpoint of the line connecting A and B; this shows that the position of C can be determined by the known properties of solutions A and B and the rules of the phasor diagram. S44. Introduce another quantum dot solution with a different lifetime as the "key" to decipher the problem, and name it K. Theoretically, when K and A with different lifetimes but the same number of photons are mixed in equal proportions to form a mixture F, then F is located at the midpoint of the line connecting A and K in the phasor diagram. When K and D with the same number of photons are mixed in equal proportions to form a mixture E, E is located at the midpoint of the line connecting A and K. When B and K are mixed in equal proportions to obtain a mixture G, G is located at the midpoint of the line connecting B and K in the phasor diagram. S45. The four quantum dot solutions with different lifetimes, K, A, B and D, are diluted or concentrated so that the number of photons satisfies A = B = D = K. S46. The K ink from step S44 is superimposed and printed onto the encrypted pattern from step S42; based on the vector rules of the phasor diagram, the cluster positions of the phasor diagram change: A is converted to F, B is converted to G, D is converted to E, and C is converted to E; thus, the encrypted pattern is further encrypted. S47. By decoding the location of cluster E, the true information "SJTU" is obtained.

9. The application of a lifetime signal combination encoding method based on quantum dot solution as described in any one of claims 1-8 in the field of anti-counterfeiting encryption.

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