CN102703061A - Method for performing fluorescent anti-counterfeit by ZnO quantum dots - Google Patents

Abstract

The invention provides a method for performing fluorescent anti-counterfeit by ZnO quantum dots. According to the method, the ZnO quantum dots with even appearance and controllable size are prepared out and then subjected to deep ultraviolet irradiation to check the fluorescent property, thus realizing high deep ultraviolet light selectivity of ZnO quantum dots; and finally the product is marked so as to realize the anti-counterfeit effect. In comparison with the traditional fluorescent anti-counterfeit method, the ZnO quantum dots used by the method is used in the fluorescent anti-counterfeit field for the first time, the process is simple and the cost is low; the anti-counterfeit material is prepared without poison side products and environmental pollution; the ZnO quantum dots generated by the method are clear, high in purity, adjustable in size, and higher in deep ultraviolet light selectivity, so that the anti-counterfeit property is greatly enhanced.

Description

Fluorescence anti-counterfeiting method using ZnO quantum dots

technical field

The invention relates to a fluorescent anti-counterfeiting method, in particular to a fluorescent anti-counterfeiting method using ZnO quantum dots.

Background technique

At present, fluorescent materials commonly used in fluorescent anti-counterfeiting marks are mainly divided into two categories: 1. Organic fluorescent materials, which are unsaturated molecules with large conjugates, mostly excited by sunlight, and can be used for decorative printing with obvious colors, but they are easy to oxidize 2. Inorganic fluorescent materials, which have strong radiation resistance and good stability, can be applied to fluorescent screens and fluorescent lamps, but they are difficult to decompose in oily media and have poor water resistance. The board has certain wear and erosion, and the commonly used inorganic fluorescent materials are toxic and pollute the environment. the

At present, UV-excited fluorescent fibers widely used in banknotes, passports, stamps, securities and various anti-counterfeiting labels have a wide sensitive ultraviolet band, and their excitation selectivity is not high enough, and they are generally only suitable for integration with paper materials. It is also required to be included in the paper synthesis, and cannot be modified or embedded in the later stage, which increases the difficulty and cost of product production.

Due to their large fluorescence efficiency and size-dependent fluorescence tunability, organic semiconductor quantum dots have been widely studied in the fields of fluorescent labeling and fluorescent sensing in recent years. Traditional Cd-based semiconductor quantum dots such as CdTe and CdSe have high fluorescence efficiency, and the fluorescence color can be adjusted from green to red with size. However, its toxicity and environmental pollution problems seriously restrict its practical application. Relatively speaking, ZnO quantum dots are green, non-toxic, easy to prepare in batches, and have sufficient and cheap raw materials. They are expected to be practically applied in bioluminescent labels and fluorescent anti-counterfeiting labels.

Contents of the invention

The purpose of the present invention is to provide a method for fluorescent anti-counterfeiting using ZnO quantum dots to overcome the shortcomings of traditional fluorescent anti-counterfeiting methods, such as poor material stability, complex production process, high cost, toxicity and environmental pollution. Uniform, size-controllable ZnO quantum dots, and the prepared ZnO quantum dots are irradiated with deep ultraviolet light to verify their fluorescence properties, ensuring that the ZnO quantum dots have high deep ultraviolet light selectivity, and finally mark the items to achieve anti-counterfeiting effect .

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A method for applying ZnO quantum dots to carry out fluorescent anti-counterfeiting, comprising the following steps:

1. Preparation of ZnO quantum dots, the specific preparation process is as follows:

(1) Add Zn(CH3COO)2·2H2O to absolute ethanol, raise the temperature to 80°C and carry out rapid stirring for 2 hours, then cool down to 0°C to generate zinc acetate ethanol with [Zn] ion concentration of 0.1 mol/L solution;

(2) Add LiOH·H2O into absolute ethanol and perform ultrasonic dissolution for 20 minutes to generate a lithium hydroxide ethanol solution with an [OH] ion concentration of 0.1-0.4 mol/L;

(3) Add the lithium hydroxide ethanol solution dropwise to the zinc acetate ethanol solution, and stir rapidly for 3 hours to generate a ZnO quantum dot solution with an average diameter of ZnO quantum dots of 2-10 nanometers; the average diameter of the ZnO quantum dots is passed through Zn The molar ratio of (CH3COO)2·2H2O and LiOH·H2O is controlled, and the range of molar ratio is 1:1-1:4;

(4) Clean and precipitate ZnO quantum dots by centrifugation or adding excess n-heptane, redisperse ZnO quantum dots in absolute ethanol, and lower the temperature below 0 ℃ to save ZnO quantum dots; ZnO quantum dots are not used immediately For fluorescent anti-counterfeiting, ZnO quantum dots also need to be wrapped, and SiO2 or PVP is preferably used to wrap ZnO quantum dots.

2. The fluorescence properties of ZnO quantum dots were verified by deep ultraviolet light irradiation

The wavelength of the deep ultraviolet light is preferably less than 300 nanometers.

3. Mark items with verified ZnO quantum dots for anti-counterfeiting

It is preferable to use a mixture of 502 glue and ZnO quantum dots to mark articles for anti-counterfeiting.

Compared with the traditional fluorescent anti-counterfeiting method, ZnO quantum dots used in this method are used in the field of fluorescent anti-counterfeiting for the first time. Quantum dots are clean, high-purity, adjustable in size, have good selectivity for deep ultraviolet light, and have greatly improved anti-counterfeiting performance.

Description of drawings

Fig. 1 is a flow chart of the implementation of the fluorescent anti-counterfeiting method using ZnO quantum dots according to the present invention.

Fig. 2 is a flow chart of the implementation of step (1) of the present invention for preparing ZnO quantum dots.

Detailed ways

Below in conjunction with accompanying drawing, the present invention will be further described:

As shown in Figure 1, the night vision image enhancement method provided by the present invention comprises the following steps:

Firstly, ZnO quantum dots are prepared, and the specific preparation process is as follows:

2.18 grams of Zn(CH3COO)2.2H2O was added to 100 milliliters of absolute ethanol, and the temperature was raised to 80

℃ and rapid stirring for 2 hours, and then cooled to 0 ℃ to generate a zinc acetate ethanol solution with a [Zn] ion concentration of 0.1 mol/L as a precursor solution; add 0.42-1.68 g of LiOH·H2O to 100 mL of In absolute ethanol, carry out ultrasonic dissolution for 20 minutes to generate a lithium hydroxide ethanol solution with an [OH] ion concentration of 0.1-0.4 mol/liter; add the lithium hydroxide ethanol solution dropwise to the zinc acetate ethanol solution, and stir rapidly for 3 hours, a ZnO quantum dot solution with an average diameter of ZnO quantum dots of 2-10 nanometers is generated. In the preparation process, temperature, reaction time, precursor solution concentration and reactant molar ratio etc. all can affect the size of ZnO quantum dot, the present invention mainly controls the size of ZnO quantum dot by controlling the molar ratio of zinc acetate and lithium hydroxide, zinc acetate and The molar ratio of lithium hydroxide is the molar ratio of [Zn] ions to [OH] ions. During the experiment, the molar ratios were respectively selected as 1:1, 1:1.4, 1:2, 1:3, and 1:4 to prepare ZnO quantum dots with a uniform shape and an average diameter of 2-10 nanometers; wash and precipitate ZnO quantum dots by centrifugation or adding excess n-heptane, redisperse them in absolute ethanol, and lower the temperature below 0 °C to preserve ZnO quantum dots.

The morphology of the prepared ZnO quantum dots is relatively uniform in spherical shape, the size distribution is relatively concentrated, and it is a hexagonal wurtzite structure with high crystallization quality. If the ZnO quantum dots obtained through the above process are not immediately used for fluorescent anti-counterfeiting and need to be stored for a long time, they are easy to agglomerate in the solution and affect the fluorescence efficiency. point stability.

Secondly, the fluorescence performance of ZnO quantum dots should be verified by irradiating ZnO quantum dots with deep ultraviolet light:

The fluorescent color of ZnO quantum dots is adjustable in size. Under the irradiation of deep ultraviolet light, it can change from blue to orange in turn with the increase of the size of ZnO quantum dots. For example, ZnO quantum dots with an average diameter of 2-10 nanometers have a wavelength of 264 nanometers Under the irradiation of deep ultraviolet light, it shows a rich color from blue to orange yellow, but it is colorless under the irradiation of sunlight and ultraviolet light with a wavelength of more than 300 nanometers, indicating that ZnO quantum dots have deep ultraviolet light excitation selectivity. , showing a unique and more excitation-selective fluorescent anti-counterfeiting performance. Subsequently, we measured the photoluminescence (PL) spectrum and photoexcitation (PLE) spectrum. The visible luminescence peak of the PL spectrum was red-shifted from 427 nm to 564 nm, and the corresponding PLE spectrum also had a significant red-shift.

Finally, use the verified ZnO quantum dots to mark items for anti-counterfeiting:

Some items are simply marked with ZnO quantum dots, such as sticking the freshly prepared ZnO quantum dot solution with a fine brush, and marking paper money, coins, CDs and glass. The banknotes marked with the ZnO quantum dot solution were irradiated under sunlight, ultraviolet light with a wavelength of 365 nanometers and deep ultraviolet light with a wavelength of 254 nanometers. It can be seen that the original fluorescent anti-counterfeiting marks in the banknotes have the same The fluorescent response of ZnO quantum dots is only visible in blue under the deep ultraviolet light with a wavelength of 254 nm. The coins, CDs and glass marked with ZnO quantum dot solution were irradiated with deep ultraviolet light with a wavelength of 254 nm, and the ZnO quantum dot marking imprint showed different colors, indicating that ZnO quantum dots can be used to design complex and diverse anti-counterfeiting Marking, more importantly, it shows that ZnO quantum dots can be used for embedded body anti-counterfeiting of non-paper commodities, breaking through the limitations of traditional paper-based label anti-counterfeiting, improving anti-counterfeiting capabilities, and providing security in the process of commodity circulation. Merchants at all levels provide a simple means of marking.

In order to improve the efficiency of marking operations and facilitate assembly line production, a mixture of ZnO quantum dot solution and 502 glue can be used to mark items in batches.

Claims (7)

1. use the method that the ZnO quantum dot carries out fluorescence falsification preventing for one kind, it is characterized in that may further comprise the steps:

(1) preparation ZnO quantum dot;

(2) through DUV irradiation ZnO quantum dot checking fluorescence property;

(3) carry out false proof with the quantum dot-labeled article of the ZnO of empirical tests.

2. application ZnO quantum dot according to claim 1 carries out the method for fluorescence falsification preventing, it is characterized in that: the process of preparation ZnO quantum dot is following in the said step (1):

(1) with Zn (CH3COO) 22H ₂O joins in the absolute ethanol, is warming up to 80 ℃ and carry out 2 hours quick stirring, is cooled to 0 ℃ again, and generating [Zn] ionic concn is the zinc acetate ethanolic soln of 0.1 mol;

(2) with LiOHH ₂O joins in the absolute ethanol, carries out 20 minutes ultrasonic dissolution, and generating [OH] ionic concn is the Lithium Hydroxide MonoHydrate ethanolic soln of 0.1-0.4 mol;

(3) the Lithium Hydroxide MonoHydrate ethanolic soln is dropwise joined in the zinc acetate ethanolic soln, stirred fast 3 hours, generating ZnO quantum dot mean diameter is the ZnO quantum dot solution of 2-10 nanometer;

(4) through centrifugal or add that excessive normal heptane cleans and deposition ZnO quantum dot, the ZnO quantum dot is dispersed in the absolute ethanol again, reduces the temperature to and preserve the ZnO quantum dot below 0 ℃.

3. application ZnO quantum dot according to claim 2 carries out the method for fluorescence falsification preventing, and it is characterized in that: the mean diameter of ZnO quantum dot is through Zn (CH3COO) 22H in the said process (3) ₂O and LiOHH ₂The mol ratio of O is controlled, and the mol ratio span is 1:1-1:4.

4. application ZnO quantum dot according to claim 2 carries out the method for fluorescence falsification preventing, it is characterized in that: when the ZnO quantum dot in the said process (4) is not used for fluorescence falsification preventing immediately, also need the ZnO quantum dot is wrapped up processing.

5. application ZnO quantum dot according to claim 4 carries out the method for fluorescence falsification preventing, it is characterized in that: adopt SiO2 or PVP that the ZnO quantum dot is wrapped up processing.

6. application ZnO quantum dot according to claim 1 carries out the method for fluorescence falsification preventing, and it is characterized in that: the deep ultraviolet light wavelength is less than 300 nanometers in the said step (2).

7. application ZnO quantum dot according to claim 1 carries out the method for fluorescence falsification preventing, it is characterized in that: adopt 502 glue and ZnO quantum dot mixture tagged items to carry out false proof in the said step (3).

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