阅读说明：本技术 基于近红外发光量子点的防伪和信息保密方法 (Anti-counterfeiting and information security method based on near-infrared light-emitting quantum dots ) 是由 张加涛 张书萍 徐萌 李建中 白冰 于 2020-11-23 设计创作，主要内容包括：本发明提供了一种基于近红外发光量子点的防伪和信息保密方法。通过将同时具有可见光-近红外光双模荧光发射特性的掺杂量子点油墨进行打印,得到防伪标记；然后在紫外光激发下,采用具有滤掉可见光能力的滤光片滤掉发射的可见光,并采用红外观测设备获取图案信息,根据是否能观察到荧光图案鉴别真伪,或者根据观察到的荧光图案确定保密信息。本发明还通过在防伪标记基础上打印干扰图样,增加防伪和保密的复制或破解难度。本发明选用的掺杂量子点是通过循环热注入法包覆钝化壳层得到,荧光性能更稳定。因此,本发明操作简单,能够实现较强的防伪和保密作用,仅通过手机摄像头就能进行鉴别和获取保密信息,简单快捷,便于推广应用。(The invention provides an anti-counterfeiting and information security method based on near-infrared luminous quantum dots. Printing the doped quantum dot ink with visible light-near infrared light dual-mode fluorescence emission characteristics to obtain an anti-counterfeiting mark; and then, under the excitation of ultraviolet light, filtering out the emitted visible light by using an optical filter with the capability of filtering out the visible light, acquiring pattern information by using infrared observation equipment, and identifying the authenticity according to whether the fluorescent pattern can be observed or not, or determining confidential information according to the observed fluorescent pattern. The invention also increases the difficulty of copying or cracking of anti-counterfeiting and confidentiality by printing the interference pattern on the basis of the anti-counterfeiting mark. The doped quantum dots are obtained by coating a passivated shell layer by a cyclic heat injection method, and the fluorescence performance is more stable. Therefore, the method is simple to operate, can realize stronger anti-counterfeiting and confidentiality functions, can identify and acquire confidential information only through the camera of the mobile phone, is simple and quick, and is convenient to popularize and apply.)

1. An anti-counterfeiting and information security method based on near-infrared luminous quantum dots is characterized by comprising the following steps:

s1, selecting a doped quantum dot with visible light-near infrared light dual-mode fluorescence emission characteristics, preparing the doped quantum dot into printable anti-counterfeiting ink, and printing according to a first preset pattern to obtain an anti-counterfeiting mark;

s2, under excitation, transmitting the fluorescence emitted by the anti-counterfeiting mark obtained in the step S1 through an optical filter with the capability of filtering visible light, then acquiring pattern information by adopting infrared observation equipment, and identifying authenticity according to whether the fluorescence pattern can be observed or not, or determining confidential information according to the observed fluorescence pattern.

2. The near infrared luminescence quantum dot-based anti-counterfeiting and information security method according to claim 1, wherein the steps of the anti-counterfeiting and information security method further comprise: before or after the anti-counterfeiting mark is printed, preparing the intrinsic quantum dots only having the visible light fluorescence effect into interference ink, and printing according to a second preset pattern to obtain an interference pattern; or uniformly mixing the interference ink and the anti-counterfeiting ink, and then printing according to a first preset pattern to obtain the anti-counterfeiting mark.

3. The method for anti-counterfeiting and information security based on the near-infrared luminescent quantum dots according to claim 2, wherein the intrinsic quantum dots and the doped quantum dots emit visible light with the same fluorescence color after being excited.

4. The method as claimed in claim 2, wherein the first predetermined pattern and the second predetermined pattern are different patterns partially or completely overlapped.

5. The near-infrared light-emitting quantum dot-based anti-counterfeiting and information privacy method according to claim 1 or 2, wherein the doped quantum dots include, but are not limited to, one or more of Cu-doped CdSe quantum dots, Cu-doped CdSe/CdS core-shell quantum dots, Cu-doped CdSe/ZnS core-shell quantum dots, Cu-doped InP/ZnS quantum dots, Ag-doped CdSe/CdS core-shell quantum dots, Ag-doped CdSe/ZnS core-shell quantum dots, Ag-doped InP quantum dots, and Ag-doped InP/ZnS quantum dots.

6. The anti-counterfeiting and information confidentiality method based on the near-infrared light-emitting quantum dots according to claim 1 or 5, wherein the doped quantum dots are metal-doped core-shell quantum dots with passivated shell layers, which are prepared by a cyclic thermal injection method, and the metal-doped core-shell quantum dots with passivated shell layers are prepared by the following steps:

s11, dispersing the metal-doped quantum dots into a solvent, adding a ligand solution containing metal ions doped in the metal-doped quantum dots with a preset content into the solvent, and vacuumizing until the solvent is completely extracted;

s12, heating the reaction system processed in the step S11 to 160-200 ℃, injecting a solution containing a metal element of the passivation layer into the reaction system, reacting for 5-15 min, then injecting a sulfur powder solution, continuously heating to 220-260 ℃, keeping the temperature, reacting for 15-30 min, and recording as first circulation heat injection;

s13, cooling the reaction system processed in the step S12 to 160-200 ℃, repeating the operation of the step S12 for a plurality of times, and sequentially recording as second-time circulating heat injection, … and nth-time circulating heat injection; n is a positive integer greater than or equal to 3;

s14, cooling the reaction solution processed in the step S13 to room temperature, centrifugally separating, and washing to obtain the shell-passivated metal-doped core-shell quantum dot.

7. The method for preventing forgery and information security based on near infrared luminescence quantum dot as claimed in claim 6, wherein in step S11, the molar ratio of metal ion in said ligand solution to cation contained in said metal doped quantum dot is (0.1-0.4): 1; the metal doped quantum dots include, but are not limited to, one or more of Cu doped CdSe quantum dots, Cu doped InP quantum dots, Ag doped CdSe quantum dots, Ag doped InP quantum dots.

8. The method for preventing counterfeiting and securing information based on the near-infrared emission quantum dots according to claim 6, wherein in step S12, the molar ratio of the passivation layer metal element to the cations contained in the metal doped quantum dots is (0.1-0.4): 1, and the addition amount of the sulfur powder solution is the same as that of the solution containing the passivation layer metal element; the content of the solution containing the metal element of the passivation layer added in the cycle heat injection process of the nth time is 1.1-1.25 times of that of the solution of the metal element of the nth-1 time.

9. The anti-counterfeiting and information confidentiality method based on the near-infrared luminescence quantum dots according to claim 8, wherein a plurality of shell layer passivated metal doped core-shell quantum dots prepared by different circulating heat injection times are added in the anti-counterfeiting ink.

10. The method for anti-counterfeiting and information confidentiality based on near-infrared light-emitting quantum dots according to claim 3, wherein the intrinsic quantum dots include, but are not limited to, one or more of CdSe quantum dots, CdSe/CdS core-shell quantum dots, CdSe/ZnS core-shell quantum dots, CdSe/ZnSe core-shell quantum dots, InP quantum dots and InP/ZnS quantum dots.

11. The method for preventing forgery and securing information based on near infrared emission quantum dots according to claim 1, wherein in step S2, the filter is a cut-off filter, and a cut-off edge of the cut-off filter is 780 to 850 nm; the infrared observation equipment is a mobile phone camera.

Technical Field

The invention relates to the technical field of quantum dot anti-counterfeiting, in particular to an anti-counterfeiting and information security method based on near-infrared light-emitting quantum dots.

Background

With the continuous development of social economy, the living standard of people is continuously improved by rich and colorful commodities. Meanwhile, counterfeit products are also in full of the market. Counterfeit and shoddy commodities and market fraud behaviors have become important factors for restricting the sustainable, rapid and healthy development of national economy in China. Meanwhile, in the information-based society, the confidentiality of text and picture information is more and more important, and the leakage of the information can bring opportunities to lawbreakers, so that economic and personal injuries are caused. With the continuous development of science and technology in recent years, quantum dot materials are gradually discovered by people due to excellent fluorescence performance and are gradually applied to the anti-counterfeiting field to solve the problems of anti-counterfeiting, information encryption and the like.

The single visible fluorescence emitted by the common quantum dot material after being excited can be simulated by some alternative materials, and the excellent anti-counterfeiting effect cannot be obtained. In order to further improve the technical barrier and the counterfeiting difficulty, it is necessary to endow a quantum dot material with a dual-mode fluorescence emission characteristic. Controllable doping of the luminescent quantum dots is realized by a cation exchange method, so that the luminescent quantum dots can simultaneously obtain visible region fluorescence and near-infrared region fluorescence under the excitation of ultraviolet light. The human eye can directly observe the fluorescence in the visible light region, the human eye cannot directly observe the fluorescence in the near infrared light region, the observation needs to be carried out by means of equipment, the method has strong confusion, and the anti-counterfeiting performance of the quantum dot material is improved to a great extent. This feature also allows near infrared light to be used as an efficient security mode that is not easily observed and broken by the naked eye.

In view of the above, there is a need to design an improved anti-counterfeiting and information security method based on near infrared light-emitting quantum dots to solve the above problems.

Disclosure of Invention

The invention aims to provide an anti-counterfeiting and information security method based on near-infrared luminous quantum dots. Printing the doped quantum dot ink with visible light-near infrared light dual-mode fluorescence emission characteristics to obtain an anti-counterfeiting mark; and then, under the excitation of ultraviolet light, filtering out the emitted visible light by using an optical filter with the capability of filtering out the visible light, acquiring pattern information by using infrared observation equipment, and identifying the authenticity according to whether the fluorescent pattern can be observed or not, or determining confidential information according to the observed fluorescent pattern. Thus, stronger anti-counterfeiting and confidentiality effects can be realized.

In order to achieve the above object, the present invention provides an anti-counterfeiting and information security method based on near infrared luminescence quantum dots, comprising the following steps:

s1, selecting a doped quantum dot with visible light-near infrared light dual-mode fluorescence emission characteristics, preparing the doped quantum dot into printable anti-counterfeiting ink, and printing according to a first preset pattern to obtain an anti-counterfeiting mark;

s2, under excitation, transmitting the fluorescence emitted by the anti-counterfeiting mark obtained in the step S1 through an optical filter with the capability of filtering visible light, then acquiring pattern information by adopting infrared observation equipment, and identifying authenticity according to whether the fluorescence pattern can be observed or not, or determining confidential information according to the observed fluorescence pattern.

As a further improvement of the invention, the anti-counterfeiting and information security method further comprises the following steps: before or after the anti-counterfeiting mark is printed, preparing the intrinsic quantum dots only having the visible light fluorescence effect into interference ink, and printing according to a second preset pattern to obtain an interference pattern; or uniformly mixing the interference ink and the anti-counterfeiting ink, and then printing according to a first preset pattern to obtain the anti-counterfeiting mark.

As a further improvement of the invention, the intrinsic quantum dots and the doped quantum dots emit visible light with the same fluorescence color after being excited.

As a further improvement of the present invention, the first predetermined pattern and the second predetermined pattern are different patterns that are partially overlapped or completely overlapped.

As a further improvement of the present invention, the doped quantum dots include, but are not limited to, one or more of Cu-doped CdSe quantum dots, Cu-doped CdSe/CdS core-shell quantum dots, Cu-doped CdSe/ZnS core-shell quantum dots, Cu-doped InP/ZnS quantum dots, Ag-doped CdSe/CdS core-shell quantum dots, Ag-doped CdSe/ZnS core-shell quantum dots, Ag-doped CdSe/ZnSe core-shell quantum dots, Ag-doped InP quantum dots, and Ag-doped InP/ZnS quantum dots.

As a further improvement of the invention, the doped quantum dots are shell-passivated metal doped core-shell quantum dots prepared by a cyclic heat injection method.

As a further improvement of the invention, the preparation method of the shell layer passivated metal doped core-shell quantum dot comprises the following steps:

s11, dispersing the metal-doped quantum dots into a solvent, adding a ligand solution containing metal ions doped in the metal-doped quantum dots with a preset content into the solvent, and vacuumizing until the solvent is completely extracted;

s12, heating the reaction system processed in the step S11 to 160-200 ℃, injecting a solution containing a metal element of the passivation layer, reacting for 5-15 min, then injecting a sulfur powder solution, continuously heating to 220-260 ℃, keeping the temperature, reacting for 15-30 ℃, and recording as first circulation heat injection;

s13, cooling the reaction system processed in the step S12 to 160-200 ℃, repeating the operation of the step S12 for a plurality of times, and sequentially recording as second-time circulating heat injection, … and nth-time circulating heat injection; n is a positive integer greater than or equal to 3;

s14, cooling the reaction solution processed in the step S13 to room temperature, centrifugally separating, and washing to obtain the shell layer passivated metal doped core-shell quantum dot.

In a further improvement of the present invention, in step S11, the molar ratio of the metal ions in the ligand solution to the metal-doped quantum dots is (0.1-0.4): 1. The metal doped quantum dots include, but are not limited to, one or more of Cu doped CdSe quantum dots, Cu doped InP quantum dots, Ag doped CdSe quantum dots, Ag doped InP quantum dots.

In a further improvement of the invention, in step S12, the molar ratio of the passivation layer metal element to the cations contained in the metal-doped quantum dots is (0.1-0.4): 1, and the addition amount of the sulfur powder solution is the same as that of the solution containing the passivation layer metal element; the content of the solution containing the metal element of the passivation layer added in the cycle heat injection process of the nth time is 1.1-1.25 times of that of the solution of the metal element of the nth-1 time.

As a further improvement of the invention, the anti-counterfeiting ink is added with a plurality of shell layer passivated metal doped core-shell quantum dots prepared by different circulating heat injection times.

As a further improvement of the invention, the intrinsic quantum dots include but are not limited to one or more of CdSe quantum dots, CdSe/CdS core-shell quantum dots, CdSe/ZnS core-shell quantum dots, CdSe/ZnSe core-shell quantum dots, InP quantum dots and InP/ZnS quantum dots.

As a further improvement of the present invention, in step S2, the infrared observation device is a camera of a mobile phone.

In a further improvement of the present invention, in step S2, the filter is a cut-off filter, and the cut-off edge of the cut-off filter is 780-850 nm.

The invention has the beneficial effects that:

1. according to the anti-counterfeiting and information security method based on the near-infrared light-emitting quantum dots, the interference information is printed by using the intrinsic quantum dots with visible light fluorescence, the security information is printed by using the doped quantum dots with visible light fluorescence and near-infrared fluorescence on the basis of the interference information, and under the condition of ultraviolet lamp irradiation, the anti-counterfeiting and security character and picture information acquisition is realized in a mode of recording the near-infrared fluorescence through a camera and an optical filter. Compared with the traditional fluorescent encryption technology, the method is more difficult to crack, can identify and acquire confidential information only through a mobile phone camera, is simple and rapid, and is convenient to popularize and apply.

2. The invention provides an anti-counterfeiting and information security method based on near-infrared light-emitting quantum dots, which adopts intrinsic quantum dots with visible light fluorescence and doped quantum dots with visible light fluorescence and near-infrared fluorescence simultaneously to perform double printing, wherein two groups of printed patterns are preferably different patterns which are partially or completely printed in an overlapping way, the two patterns are overlapped and staggered, pattern information seen by naked eyes is obviously different from near-infrared pattern information (such as lines, positions and the like) acquired by an optical filter and infrared equipment, and the copying difficulty can be increased. Even with the similar method of the present invention, it is difficult to perfectly reproduce the two patterns in the interlaced form designed by the present invention.

3. According to the anti-counterfeiting and information confidentiality method based on the near-infrared light-emitting quantum dots, the doped quantum dots which simultaneously have visible light fluorescence and near-infrared fluorescence are shell-passivated metal-doped core-shell quantum dots prepared by a cyclic heat injection method. By reasonably controlling the number of times of circulating heat injection and the addition amount of circulating heat injection in each time, the fluorescent property of the prepared shell layer passivated metal doped core-shell quantum dot can be regulated, so that the shell layer passivated metal doped core-shell quantum dot with diversified fluorescent properties is obtained. And then, a plurality of shell layer passivated metal doped core-shell quantum dots with slightly different fluorescence properties are mixed and printed, and the information such as the preparation method, the formula design of the printing ink and the like is required to be clearly mastered for copying, so that the copying difficulty can be further increased.

Drawings

In fig. 1, (a1) and (a2) are patterns observed by the human eye under natural light irradiation of the interference patterns printed in step (1) and step (2) in example 2, respectively.

In fig. 2, (a1) and (a2) show the patterns observed by the human eye under the irradiation of an ultraviolet lamp for the interference patterns printed in step (1) and step (2) of example 2, respectively.

In fig. 3, (a1) and (a2) are respectively the observation patterns of the interference pattern printed in step (1) and step (2) in example 2, under the irradiation of an ultraviolet lamp, the camera is matched with an optical filter (800 nm).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to specific embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme of the present invention are shown in the specific embodiments, and other details not closely related to the present invention are omitted.

In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention provides an anti-counterfeiting and information security method based on near-infrared luminous quantum dots, which comprises the following steps:

s1, selecting a doped quantum dot with visible light and near-infrared fluorescence simultaneously, preparing the doped quantum dot into printable anti-counterfeiting ink, and printing according to a first preset pattern to obtain an anti-counterfeiting mark;

s2, under the excitation of ultraviolet light, transmitting the fluorescence emitted by the anti-counterfeiting mark obtained in the step S1 through an optical filter with the capability of filtering visible light, then acquiring pattern information by adopting infrared observation equipment, and identifying the authenticity according to whether the fluorescence pattern can be observed or not, or determining confidential information according to the observed fluorescence pattern.

The infrared observation equipment can be a mobile phone camera. The filter is a cut-off filter, and the cut-off edge of the cut-off filter is 780-850 nm. When the fluorescence emitted by the anti-counterfeiting mark penetrates through the optical filter with the capability of filtering out visible light, the optical filter filters out light rays with the wavelength within the cut-off edge, and because the anti-counterfeiting mark comprises doped quantum dots with visible light and near-infrared fluorescence, the near-infrared fluorescence cannot be filtered, and the near-infrared fluorescence cannot be seen by naked eyes, and the near-infrared image of the anti-counterfeiting mark can be obtained by shooting through a camera of a mobile phone. Thus, the authenticity of the product can be identified by judging whether the near infrared image is the same as the genuine product or not, or the secret information can be determined according to the observed fluorescent pattern.

Preferably, the steps of the anti-counterfeiting and information security method further comprise: before or after the anti-counterfeiting mark is printed, preparing the intrinsic quantum dots only having the visible light fluorescence effect into interference ink, and printing according to a second preset pattern to obtain an interference pattern; or uniformly mixing the interference ink and the anti-counterfeiting ink, and then printing according to a first preset pattern to obtain the anti-counterfeiting mark.

For example: in the final printed pattern, the second preset pattern and the first preset pattern may be identical patterns overlapped with each other, and at this time, the interference ink and the anti-counterfeiting ink may be mixed uniformly and then printed synchronously, or one of the inks may be used for printing first, and then on the basis of printing, the other ink is printed in an overlapped manner, preferably, synchronous printing is performed. The second preset pattern and the first preset pattern can be different patterns which are partially or completely printed in an overlapped mode, the two patterns are overlapped and staggered, the copying difficulty can be increased, and even if a similar method is adopted, the two patterns are difficult to perfectly copy in the staggered mode designed by the invention. The second predetermined pattern and the first predetermined pattern may also be part of the final pattern, respectively, i.e. not overlapping each other.

Preferably, the first predetermined pattern and the second predetermined pattern are different patterns that are partially overlapped or completely overlapped. By doing so, the difficulty of copying the anti-counterfeit mark can be increased.

The intrinsic quantum dots and the doped quantum dots emit visible light with the same fluorescence color after being excited. So set up, can cause the visual puzzlement for the observer is difficult to discern the pattern through the naked eye and prints for different multiple printing ink, further increases the duplication degree of difficulty.

The metal-doped quantum dots include, but are not limited to, one or more of Cu-doped CdSe quantum dots, Cu-doped CdSe/CdS core-shell quantum dots, Cu-doped CdSe/ZnS core-shell quantum dots, Cu-doped CdSe/ZnSe core-shell quantum dots, Cu-doped InP/ZnS quantum dots, Ag-doped CdSe/CdS core-shell quantum dots, Ag-doped CdSe/ZnS core-shell quantum dots, Ag-doped InP quantum dots, and Ag-doped InP/ZnS quantum dots.

The doped quantum dots are preferably shell-passivated metal doped core-shell quantum dots prepared by a cyclic thermal injection method. The preparation method of the shell layer passivated metal doped core-shell quantum dot comprises the following steps:

s11, dispersing the metal-doped quantum dots into a solvent, adding a ligand solution containing metal ions doped in the metal-doped quantum dots with a preset content, and vacuumizing until the low-boiling-point solvent is completely extracted;

s12, heating the reaction system processed in the step S11 to 160-200 ℃, injecting a solution containing a metal element of the passivation layer, reacting for 5-15 min, then injecting a sulfur powder solution, continuously heating to 220-260 ℃, keeping the temperature, reacting for 15-30 ℃, and recording as first circulation heat injection;

s13, cooling the reaction system processed in the step S12 to 160-200 ℃, repeating the operation of the step S2 for a plurality of times, and sequentially recording as second-time circulating heat injection, … and nth-time circulating heat injection; n is a positive integer greater than or equal to 3;

s14, cooling the reaction solution processed in the step S13 to room temperature, centrifugally separating, and washing to obtain the shell layer passivated metal doped core-shell quantum dot.

In step S11, the molar ratio of the metal ions in the ligand solution to the cations contained in the metal-doped quantum dots is (0.1-0.4): 1. For example, when the metal-doped quantum dot is a Cu-doped CdSe quantum dot, the ligand solution containing the metal ion doped in the metal-doped quantum dot is a ligand solution containing Cu ions, such as a methanol solution of copper nitrate. The prepared shell-passivated metal-doped core-shell quantum dot can be a Cu-doped CdSe/CdS core-shell nanocrystal, a Cu-doped CdSe/ZnS core-shell nanocrystal, an Ag-doped CdSe/CdS core-shell nanocrystal, an Ag-doped CdSe/ZnS core-shell nanocrystal, a Cu-doped InP/ZnS nanocrystal, an Ag-doped InP/ZnS nanocrystal and the like.

In step S12, the molar ratio of the metal element of the passivation layer to the cation contained in the metal-doped quantum dot is (0.1-0.4): 1, and the addition amount of the sulfur powder solution is the same as that of the solution containing the metal element of the passivation layer; the content of the solution containing the metal element of the passivation layer added in the cycle heat injection process of the nth time is 1.1-1.25 times of that of the solution of the metal element of the nth-1 time. Through repeated step-by-step cyclic heat injection of the solution of the metal element of the passivation layer and the sulfur powder solution, the escape of the metal doped in the metal doped quantum dot can be effectively prevented, and the prepared shell layer passivated metal doped core-shell quantum dot has the advantages of few surface defects, good stability and high fluorescence quantum efficiency.

The anti-counterfeiting ink is added with a plurality of shell layer passivated metal doped core-shell quantum dots prepared by different circulating heat injection times. By the operation, the fluorescent property of the prepared shell layer passivated metal doped core-shell quantum dot can be regulated and controlled by reasonably controlling the number of times of circulating heat injection and the addition amount of each circulating heat injection, so that the shell layer passivated metal doped core-shell quantum dot with diversified fluorescent properties is obtained. A plurality of shell layer passivated metal doped core-shell quantum dots with slightly different fluorescence properties are adopted for mixed printing, and if imitation is to be carried out, the preparation method and the ink formula design of the invention must be mastered, so that the copying difficulty can be further increased.

The intrinsic quantum dots include, but are not limited to, one or more of CdSe quantum dots, CdSe/CdS core-shell quantum dots, CdSe/ZnS core-shell quantum dots, CdSe/ZnSe core-shell quantum dots, InP quantum dots and InP/ZnS quantum dots.

Example 1

An anti-counterfeiting and information security method based on near-infrared luminous quantum dots comprises the following steps:

s1, adding the prepared Cu-doped CdSe/CdS quantum dots into a proper amount of toluene, uniformly mixing to obtain printable anti-counterfeiting ink, and printing the printable anti-counterfeiting ink according to a preset pattern to obtain an anti-counterfeiting mark;

and S2, under the excitation of ultraviolet light, transmitting the fluorescent light emitted by the anti-counterfeiting mark obtained in the step S1 through an optical filter with the capability of filtering visible light, then acquiring pattern information by adopting infrared observation equipment (such as simple equipment like a smart phone camera) and identifying authenticity according to whether the fluorescent pattern can be observed or not, or determining confidential information according to the observed fluorescent pattern.

Example 2

An anti-counterfeiting and information security method based on near-infrared luminous quantum dots comprises the following steps:

(1) printing of interference information: and (3) loading the intrinsic CdSe/CdS quantum dot toluene ink into an ink box, then placing the ink box into a printer, and printing on parchment paper without a fluorescent brightener according to second preset pattern information which is designed in advance to obtain an interference pattern.

Preparing intrinsic CdSe/CdS quantum dot ink:

(11) 0.6mmol of cadmium oxide, 3mmol of stearic acid and 12ml of octadecene were placed in a 50ml three-neck flask, and nitrogen was introduced to raise the temperature to 250 ℃. Then 1.5ml of selenium powder octadecylene suspension with the concentration of 0.1M is injected, 0.3ml of selenium powder octadecylene suspension with the concentration of 0.1M is added after 10 minutes, 0.15ml of selenium powder octadecylene suspension with the concentration of 0.1M is added after 3-4 minutes, and then 0.15ml of selenium powder octadecylene suspension with the concentration of 0.1M is added for multiple times at intervals of 3-4 minutes until the first exciton peak position of the intrinsic CdSe quantum dot is about 610 nm. Then, the temperature was reduced to 50 ℃ and 6ml of n-butylamine and 25ml of ethanol were added thereto, and after sufficient stirring, centrifugation was carried out at 8000 rpm for 5 minutes. After the supernatant was removed and 10ml of n-hexane and 20ml of ethanol were added thereto, the mixture was thoroughly washed and centrifuged at 8000 rpm for 5 minutes. And pouring the supernatant, adding 10ml of n-hexane, 1ml of chloroform and 30ml of acetone, fully washing, centrifuging at 8000 rpm for 5 minutes, pouring the supernatant, and dispersing the precipitate into 60ml of n-hexane to obtain the intrinsic CdSe quantum dots.

(12) 35ml of an n-hexane solution of intrinsic CdSe quantum dots were taken, and then 1.25ml of oleic acid, 0.75ml of tributylphosphine, and 20ml of octadecene were added in this order. The device is vacuumized at room temperature and slowly heated to 80 ℃, and the temperature is further raised to 180 ℃ after n-hexane is completely pumped out. At this point 0.434ml of 0.1M cadmium stearate in octadecene was injected and held at that temperature for 10 minutes, then 0.434ml of 0.1M sulfur powder in octadecene was injected and immediately warmed to 250 ℃ and held for 20 minutes. Then cooled to 180 ℃ and injected with 0.538ml of a 0.1M solution of cadmium stearate in octadecene and held at this temperature for 10 minutes, then injected with 0.538ml of a 0.1M solution of sulfur powder in octadecene and immediately heated to 250 ℃ and held for 20 minutes. Then, according to the method, 0.653ml, 0.779ml and 0.916ml of octadecylene solution of cadmium stearate with the concentration of 0.1M and octadecylene solution of sulfur powder with the concentration of 0.1M are respectively injected. Then, the temperature is reduced to room temperature, 80ml of isopropanol is added, the mixed solution is centrifuged for 6 minutes at 8500 revolutions, the supernatant is poured off, the bottom precipitate is dispersed into 20ml of toluene, and the mixture is filtered by an organic filter membrane with the pore diameter of 220 nm.

(2) Printing of confidential information: and (3) filling the Cu-doped CdSe/CdS quantum dot toluene ink into an ink box, then putting the ink box into a printer, and continuously printing on the basis of the interference pattern printed in the step (1) according to the pre-designed first preset pattern information to obtain the final anti-counterfeiting mark.

The Cu-doped CdSe/CdS quantum dot is prepared by the following steps:

(21)Cu₂preparation of Se quantum dots: 0.5mmol of copper acetate and 4ml of oleylamine were mixed and put in a 50ml three-necked flask, then nitrogen gas was introduced and the temperature was raised to 130 ℃, and then a mixed solution of 2ml of n-dodecylmercaptan, 1ml of oleylamine, 0.5ml of n-dodecylmercaptan and 19mg of selenium powder was added in this order and the reaction was maintained at that temperature for 15 minutes. After cooling to room temperature, 15ml of ethanol was added to the flask, and then the flask was centrifuged at 4000 rpm for 5 minutes, and the supernatant was decanted and the bottom precipitate was dispersed in 10ml of n-hexane.

(22) Preparation of Cu-doped CdSe quantum dots: 1mmol of cadmium acetate, 10ml of octadecene and 1ml of tributylphosphine are mixed and added into a 50ml three-neck flask, nitrogen is introduced to heat up to 80 ℃, and then 10ml of Cu is added₂Adding a normal hexane solution of Se quantum dots into a flask, heating to 150 ℃ after the normal hexane is completely volatilized, keeping reacting for 15 minutes, cooling to room temperature, adding 40ml of isopropanol, centrifuging for 6 minutes at 8000 revolutions, pouring out a supernatant, and dispersing bottom precipitate into 40ml of normal hexane.

(23) Preparing Cu-doped CdSe/CdS quantum dots: 35ml of Cu-doped CdSe quantum dot n-hexane solution is taken, and then 1.25ml of oleic acid, 0.75ml of tributylphosphine, 0.75ml of copper nitrate methanol solution with the concentration of 0.1M and 20ml of octadecene are sequentially added. The apparatus was evacuated at room temperature and slowly warmed to 80 ℃ until n-hexane was completely withdrawn.

(24) The temperature was then raised to 180 ℃ at which time 0.415ml of a 0.1M solution of cadmium stearate in octadecene was injected and held at that temperature for 10 minutes, then 0.415ml of a 0.1M solution of sulfur powder in octadecene was injected and immediately raised to 250 ℃ and held for 20 minutes. Then, the temperature was decreased to 180 ℃ and 0.513ml of a 0.1M solution of cadmium stearate in octadecene was injected and maintained at the temperature for 10 minutes, and then 0.513ml of a 0.1M solution of sulfur powder in octadecene was injected and immediately increased to 250 ℃ and maintained for 20 minutes. Then, according to the method, 0.620ml, 0.738ml and 0.866ml of octadecylene solution of cadmium stearate with the concentration of 0.1M and octadecylene solution of sulfur powder with the concentration of 0.1M are respectively injected in sequence.

(25) And then cooling to room temperature, adding 80ml of isopropanol, centrifuging the mixed solution at 8500 r for 6 minutes, pouring out supernatant, taking bottom precipitate, and obtaining the Cu-doped CdSe/CdS quantum dot.

(3) The printed information was irradiated with ultraviolet light, and character or pattern information was recorded with a camera without using a filter and with a filter (filter having a cut-off edge of 800nm), respectively.

As shown in fig. 1, it can be seen that, when the printed pattern is placed under natural light, the colors of the interference pattern and the security pattern are consistent and cannot be distinguished by naked eyes, as shown in (a1) and (a2) of fig. 1, under the irradiation of an ultraviolet lamp, the left and right sides of the printed pattern are observed by human eyes only, and the left and right sides of the printed pattern show pale violet fluorescent patterns, as shown in (a1) and (a2) of fig. 2; under the irradiation of an ultraviolet lamp, the camera is shielded by a filter with the cut-off edge of 800nm for taking a picture, the right pattern still observes an obvious pale violet fluorescent pattern, the edge of the pattern is clearly visible, and the left pattern is hardly visible, so that high-level anti-counterfeiting can be realized by the difference, as shown in (a1) and (a2) in fig. 3.

In addition, the red fluorescence of the doped quantum dots and the red fluorescence of the intrinsic quantum dots are consistent or close in color and are recorded by the camera as interference information, and the near-infrared fluorescence of the doped quantum dots penetrates through the optical filter and is recorded by the camera as security information, so that the high security function of the information can be realized.

Example 3

Compared with embodiment 2, the difference between the anti-counterfeiting and information security method based on the near-infrared light-emitting quantum dots is that the second preset pattern in the step (1) and the first preset pattern in the step (2) are patterns which are designed and printed in a mutually staggered mode. The rest is substantially the same as embodiment 2, and will not be described herein. By doing so, the pattern information seen by naked eyes is obviously different from the near-infrared pattern information (such as lines, positions and the like) acquired by the optical filter and the infrared device. Thereby increasing the difficulty of replication and the level of security.

Example 4

Compared with the example 2, the difference is that in the step (2), the Cu-doped CdSe/CdS quantum dot toluene ink also comprises Cu-doped CdSe/CdS quantum dots which are prepared by three times and four times of circulating heat injection times, besides the Cu-doped CdSe/CdS quantum dots prepared by the preparation method in the example 2. The Cu-doped CdSe/CdS quantum dots prepared by the three methods have approximately the same content. The rest is substantially the same as embodiment 2, and will not be described herein. The Cu-doped CdSe/CdS quantum dots prepared by different circulating heat injection times have certain differences in fluorescence emission performance, so that the copying difficulty and the confidentiality grade of the anti-counterfeiting pattern can be increased.

In summary, the anti-counterfeiting and information security method based on the near-infrared light-emitting quantum dots provided by the invention adopts the intrinsic quantum dots with visible light fluorescence and the doped quantum dots with visible light fluorescence and near-infrared fluorescence for double printing, and realizes anti-counterfeiting and security character and picture information acquisition by recording the near-infrared fluorescence through the camera and the optical filter. The two groups of printed patterns are preferably different partially or completely printed patterns in an overlapping mode, the two patterns are overlapped and staggered, pattern information seen by naked eyes is obviously different from near-infrared pattern information (such as lines, positions and the like) acquired through the optical filter and the infrared equipment, and the copying difficulty can be increased. Therefore, the method is simple to operate, can realize stronger anti-counterfeiting and confidentiality functions, can identify and acquire confidential information only through the camera of the mobile phone, is simple and quick, and is convenient to popularize and apply.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.