CN113736465B - Dual-mode fluorescent nanoparticle composite material, preparation method and application - Google Patents

Abstract

The invention discloses a dual-mode fluorescent nanoparticle composite material, a preparation method and application, wherein the composite material is prepared from up-conversion luminescent nanoparticles and a EuSe semiconductor material, wherein the EuSe semiconductor material is uniformly coated on the surfaces of the up-conversion luminescent nanoparticles to form a heterogeneous particle structure; the fluorescent light can emit two kinds of fluorescent light with different colors under the excitation of two laser light sources with different wavelengths, and the emitted fluorescent light can be clearly seen by naked eyes, so that the fluorescent light can be widely applied to the fields of optical anti-counterfeiting, information safety and the like. The composite material provided by the invention has the advantages of uniform appearance, good dispersibility and high stability; the preparation method provided by the invention has the advantages of simple steps, easiness in control and high repeatability; the material of the invention ensures that the formed anti-counterfeiting pattern is bright and clear and has high aesthetic feeling through the synergistic effect of the components and the structure, and can meet the anti-counterfeiting requirement of high-grade products.

Description

A dual-mode fluorescent nanoparticle composite material, preparation method and application

technical field

The invention relates to the technical field of nanomaterials and optical anti-counterfeiting, in particular to a dual-mode fluorescent nanoparticle composite material, a preparation method and an application.

Background technique

The counterfeiting and counterfeiting of high-end commodities is a growing and long-standing global problem, which is common in daily life, deceives consumers, and seriously affects the normal circulation of commodities and brand reputation. At present, counterfeit and shoddy products produced by illegally forging packaging, trademarks, documents, etc. have penetrated into many industries, including medicine, food, clothing, luxury goods, jewelry, software, banknotes, diplomas and certificates, etc. The above-mentioned counterfeit and counterfeit items not only disturb the normal economic development order, but also damage the reputation of enterprises, and even pose a major threat to the health of consumers. Therefore, anti-counterfeiting materials and technologies are receiving more and more attention, and governments are also working hard to develop advanced anti-counterfeiting technologies to protect important documents from being copied.

Applying fluorescent materials to anti-counterfeiting is one of the most effective technical means at present. With the deepening of research, more and more optical materials, such as carbon quantum dots, metal organic frameworks, etc., are increasingly used for anti-counterfeiting. Chinese invention patent application CN201810836592.9 discloses a preparation method and application of a rare earth-doped NaYF ₄ /carbon quantum dot dual-mode fluorescent nanocomposite material, which combines rare earth-doped NaYF ₄ up-conversion nanoparticles modified with cationic surfactants. The aqueous dispersion is mixed with the carbon quantum dot solution, then lye, ethyl acetate and ethyl orthosilicate are added to the mixed solution, and the surface of the rare earth doped NaYF ₄ particles is coated with a silica shell layer by using the sol-gel chemistry principle. At the same time, the carbon quantum dots are encapsulated in the shell layer to prepare a core-shell type nanocomposite material. The preparation method effectively avoids the aggregation and quenching of the carbon quantum dots, and can be prepared into ink, and the prepared composite material can be used in the field of anti-counterfeiting through inkjet printing.

However, the preparation method provided by the above-mentioned technical solution of the patent application has many steps, complicated processes, and is not easy to control; the dual-mode fluorescent nanocomposite material provided by the above-mentioned technical solution of the patent application has low intensity under the excitation of near-infrared and ultraviolet dual-mode light sources, and is not easy to pass through the naked eye. For direct identification, it is used as a fluorescent filler to disperse into ink for outputting invisible fluorescent anti-counterfeiting patterns, which are dim, have low definition, and have low aesthetics, which cannot meet the anti-counterfeiting needs of high-end products and reduce their practicability.

SUMMARY OF THE INVENTION

Aiming at the problems in the prior art that the above-mentioned preparation methods are complex and the material properties are insufficient, and the patterns formed cannot meet the requirements of high-end product anti-counterfeiting patterns for brightness, clarity, and high aesthetics, the purpose of the present invention is to provide a dual-mode fluorescent nanometer The particle composite material, preparation method and application solve the above problems by simultaneously improving the composition, structure and preparation process of the material, specifically using europium selenide (EuSe) to coat upconversion nanoparticles.

For achieving the above object, the technical scheme provided by the present invention is:

A dual-mode fluorescent nanoparticle composite material, characterized in that the composite material is made of upconversion luminescent nanoparticles and EuSe semiconductor material, wherein the EuSe semiconductor material is uniformly coated on the surface of the upconversion luminescent nanoparticle to form a heterogeneous particle structure.

The composite material can emit fluorescence that is clearly visible to the naked eye under the excitation of two different wavelength light sources, respectively forming dual-mode fluorescence of up-conversion luminescence and down-transfer luminescence.

A method for preparing the dual-mode fluorescent nanoparticle composite material, characterized in that it comprises the following steps:

(1) Weigh a set amount of selenium powder, add it into a single-necked bottle, add tri-n-octylphosphorus in a set proportion, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, until the solution in the bottle is clear and transparent, forming the first Dispersions;

(2) Weigh a set amount of europium source and add it to the three-necked flask, then add the first dispersion liquid, oleylamine, oleic acid, octadecene and the up-conversion luminescent nanoparticles whose surface ligand is oleic acid in turn according to the set ratio The cyclohexane dispersion liquid was heated to 280-300 °C under the protection of argon atmosphere, reacted for 3 hours, cooled to room temperature, and then added acetone; the sample was precipitated, washed with acetone ultrasonically, and centrifuged to obtain EuSe-coated rare earth upconversion Luminescent nanoparticles, namely dual-mode fluorescent nanoparticle composites.

The europium source in the step (2) includes but is not limited to europium nitrate, europium chloride, europium acetate and hydrates thereof.

In the step (2), relative to 1 mmol of selenium powder, the amount of tri-n-octyl phosphorus is 2-3 mL.

In the step (2), the temperature during the ultrasonic treatment is 15-35° C., the ultrasonic time is 20-40 minutes, and the frequency of the ultrasonic wave is set to 39KHz-41KHz.

In the step (2), with respect to the europium source of 1 mmol, the consumption of the first dispersion liquid is 2 to 3 mL, the consumption of oleylamine is 3 to 5 mL, the consumption of oleic acid is 1 to 2 mL, and the consumption of octadecene is 30 mL. ~35mL, and the amount of upconversion nanoparticles whose surface ligand is oleic acid is 1~2mmol.

An application of the dual-mode fluorescent nanoparticle composite material is characterized in that it is used as a dual-mode fluorescent filler to prepare solid or liquid products applied to up/down conversion dual-mode optical anti-counterfeiting.

An application of the dual-mode fluorescent nanoparticle composite material, characterized in that it is used as a dual-mode fluorescent filler to prepare solid or liquid products for up/down conversion dual-mode optical information storage or information security.

Compared with the prior art, the beneficial effects of the present invention are:

1. The dual-mode fluorescent nanoparticle composite material and preparation method provided by the present invention, by simultaneously improving the composition, structure and preparation process of the material, specifically using europium selenide (EuSe) to coat the up-conversion nanoparticles, through specific components The synergistic effect of the composite material and the structure improves the fluorescence intensity of the composite material, and the composite material has uniform size, good dispersion, stable structure and performance, and has the advantages of up/down conversion dual-mode light emission, which makes the anti-counterfeiting formed by using it. The pattern has the characteristics of bright, clear, and high aesthetics, which can meet the anti-counterfeiting needs of high-end products; compared with the existing optical anti-counterfeiting materials, the material has the following outstanding advantages: (1) the use of fewer types of raw materials, the preparation process is simple and efficient, High repeatability; (2) The material has stable structure, uniform shape and good monodispersity; (3) The material has the characteristics of up/down conversion dual-mode luminescence; (3) The structure and components cooperate with each other to avoid multiple The decrease in fluorescence intensity due to cross-relaxation between doping species of lanthanide ions.

2. The preparation method of the dual-mode fluorescent nanoparticle composite material provided by the present invention utilizes EuSe semiconductor to coat up-conversion nanoparticles to obtain a nano-composite material with up/down conversion luminescence function. The method has simple steps, convenient operation, and reaction conditions. It is easy to control and has high repeatability, and the obtained product has good consistency and good dispersion, and is easy to industrialize.

3. The dual-mode fluorescent nanoparticle composite material provided by the present invention has uniform size, good dispersibility, stable structure and performance, and has the advantages of up/down conversion dual-mode luminescence. Under the irradiation, it can emit up-conversion visible light, and the europium selenide semiconductor can emit down-transfer blue light visible to the naked eye under the irradiation of ultraviolet light. Therefore, it can be widely used in the fields of up/down conversion dual-mode optical anti-counterfeiting, information security, and storage.

Description of drawings

1 is a transmission electron microscope (TEM) photograph of the NaYF ₄ : Yb, Tm nanoparticle and EuSe-coated NaYF ₄ : Yb, Tm nanoparticle composite material obtained in Example 1 of the present invention;

2 is a fluorescence spectrum diagram of the EuSe-coated NaYF ₄ :Yb,Er nanoparticle composite material obtained in Example 2 of the present invention under excitation by a 980 nm laser light source.

Fig. 3 is the fluorescence spectrum of the composite material of EuSe-coated NaYF ₄ : Yb, Ho nanoparticles obtained in Example 3 of the present invention under excitation by a 365 nm laser light source;

4 is a picture of the anti-counterfeiting application of the composite material using EuSe to coat NaGdF ₄ : Yb, Tm nanoparticles according to Example 7 of the present invention.

The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

Detailed ways

Example 1:

The dual-mode fluorescent nanoparticle composite material provided in this embodiment is specifically a composite material of EuSe-coated NaYF ₄ : Yb, Tm up-conversion luminescent nanoparticles.

The dual-mode fluorescent nanoparticle composite material provided in this embodiment is made of NaYF ₄ :Yb,Tm upconversion luminescent nanoparticles and EuSe semiconductor material, wherein the EuSe semiconductor material is uniformly coated on NaYF ₄ :Yb,Tm A heterogeneous particle structure is formed on the surface of the nanoparticle; the composite material can emit fluorescence clearly visible to the naked eye under the excitation of two different wavelength laser light sources, respectively forming dual-mode fluorescence of up-conversion luminescence and down-transfer luminescence.

The preparation method of the EuSe-coated NaYF ₄ :Yb, Tm up-conversion luminescent nanoparticle composite material provided in this embodiment includes the following steps:

(1) Weigh 1mmol of selenium powder and add it to the single-necked bottle, then add 2mL of tri-n-octylphosphorus, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, the temperature during ultrasonic treatment is controlled to be 25 ° C, the ultrasonic time is 20 minutes, the ultrasonic wave The frequency is 40KHz. Sonicate until the solution in the bottle is clear and transparent, forming the first dispersion.

(2) take by weighing the EuCl ₃ 6H ₂ O of 1mmol and add in the there-necked flask, then add the first dispersion liquid of 2mL, 3mL oleylamine, 1mL oleic acid, 30mL octadecene and 1mmol surface ligands are _NaYF of oleic acid : The cyclohexane dispersion of Yb, Tm up-conversion luminescent nanoparticles was reacted at a high temperature of 280-300 °C for 3 hours under an argon protective atmosphere. After cooling to room temperature, add 40 mL of acetone to precipitate the obtained composite material, place the material in a high-speed centrifuge, set the centrifuge rotation speed to be 8000 rev/min, and finish the centrifugation to obtain the EuSe-coated NaYF ₄ : Yb, Tm nanoparticles composite material.

During the research process, the inventor's team found that in the previous research on rare earth dual-mode luminescence anti-counterfeiting system, a variety of rare earth elements with up-conversion and down-transfer characteristics were often uniformly mixed in the same material, while lanthanides often occurred. Cross-relaxation leads to a decrease in luminous intensity, which makes the formed anti-counterfeiting images and text unclear (low definition) and difficult to distinguish. The rare earth luminescent material used in the present invention has excellent optical properties such as narrow-band emission peak, long fluorescence lifetime and high stability, but how to combine it with lanthanide elements to avoid the cross-relaxation site is the research focus of the present invention. Technical problems that need to be solved. The dual-mode fluorescent nanoparticle composite material provided in this embodiment, through the synergy of material components and structure, can emit fluorescence clearly visible to the naked eye under the excitation of two different wavelength laser light sources, respectively forming up-conversion luminescence and The dual-mode fluorescence of down-transfer luminescence solves this technical problem.

Most of the rare earth light-emitting systems based on the present invention for storing anti-counterfeiting information have the disadvantages of a single fluorescence mode, the need for a specific and expensive excitation light source, and the inability to adjust the light-emitting color, resulting in limited information storage and anti-counterfeiting capacity and the risk of deciphering. problem and start the research and development of new materials. The dual-mode luminescent material provided by the invention can fuse different fluorescent colors of up-conversion luminescence and down-transfer luminescence onto the same luminescence platform, improve the scientific and technological content of anti-counterfeiting technology, establish technical barriers to prevent counterfeiting and counterfeiting, and at the same time identify genuine products Provide efficient and convenient technical means.

As shown in Figure 1, (a) is the TEM image of NaYF ₄ :Yb,Tm nanoparticles, (b) is the TEM image of the composite material of EuSe coated NaYF ₄ :Yb,Tm nanoparticles, the figure shows EuSe The morphology and properties of the composite material obtained by coating the nanoparticles with semiconductors changed significantly, and became peanut (ellipsoid)-shaped nanoparticles.

An application of the aforementioned dual-mode fluorescent nanoparticle composite material, which is used as a dual-mode fluorescent filler to prepare a solid or liquid product for up/down conversion dual-mode optical anti-counterfeiting, which can be specifically used in the manufacture of printing anti-counterfeiting ink and special anti-counterfeiting paper Wait.

Example 2:

The dual-mode fluorescent nanoparticle composite material, preparation method, and application provided in this embodiment are basically the same as those in Example 1, except that the dual-mode fluorescent nanoparticle composite material is specifically EuSe-coated NaYF _{4 .} : Yb,Er upconversion luminescent nanoparticle composites.

The present embodiment provides a synthesis and preparation process of EuSe-coated NaYF ₄ :Yb,Er nanoparticle composite material, which includes the following steps:

(1) Weigh 1mmol of selenium powder and add it to the single-necked bottle, then add 2mL of tri-n-octylphosphorus, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, the temperature during ultrasonic treatment is controlled to be 25 ° C, the ultrasonic time is 20 minutes, the ultrasonic wave The frequency is 40KHz. Sonicate until the solution in the bottle is clear and transparent, forming the first dispersion.

(2) take by weighing the EuCl ₃ 6H ₂ O of 1mmol and add in the there-necked flask, then add the first dispersion liquid of 2mL, 3mL oleylamine, 1mL oleic acid, 30mL octadecene and 1mmol surface ligands are _NaYF of oleic acid : The cyclohexane dispersion of Yb and Er nanoparticles was reacted at a high temperature of 280-300°C for 3 hours under an argon atmosphere. After cooling to room temperature, add 40 mL of acetone to precipitate the obtained composite material, place the material in a high-speed centrifuge, set the centrifuge rotation speed to be 8000 rev/min, and remove the lower layer precipitation after centrifugation to obtain EuSe-coated NaYF ₄ : Yb, Er nanoparticles composite material.

As shown in Figure 2, the EuSe-coated NaYF ₄ :Yb,Er nanoparticle composite material mainly emits green light and red light under the excitation of 980nm laser light source, the green light peak is at 545nm, and the red light peak is at 654nm.

Example 3:

The dual-mode fluorescent nanoparticle composite material, preparation method, and application provided in this embodiment are basically the same as those in Example 1, except that the dual-mode fluorescent nanoparticle composite material is specifically EuSe-coated NaYF _{4 .} : Yb,Ho nanoparticle composites.

The present embodiment provides a synthesis and preparation method of EuSe-coated NaYF ₄ :Yb,Ho nanoparticle composite material, which includes the following steps:

(1) Weigh 1mmol of selenium powder and add it to the single-necked bottle, then add 2mL of tri-n-octylphosphorus, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, the temperature during ultrasonic treatment is controlled to be 25 ° C, the ultrasonic time is 20 minutes, the ultrasonic wave The frequency is 40KHz. Sonicate until the solution in the bottle is clear and transparent, forming the first dispersion.

(2) take by weighing the EuCl ₃ 6H ₂ O of 1mmol and add in the there-necked flask, then add the first dispersion liquid of 2mL, 3mL oleylamine, 1mL oleic acid, 30mL octadecene and 1mmol surface ligands are _NaYF of oleic acid : The cyclohexane dispersion of Yb,Ho nanoparticles was reacted at 280-300℃ for 3 hours under argon atmosphere. After cooling to room temperature, 40 mL of acetone was added to precipitate the obtained composite material, the material was placed in a high-speed centrifuge, the centrifuge speed was set to 8000 rev/min, and the centrifugation was over to remove the lower layer of precipitation to obtain EuSe-coated NaYF ₄ : Yb, Ho nanoparticle composite Material.

As shown in Figure 3, the EuSe-coated NaYF ₄ :Yb,Ho nanoparticle composite material mainly emits blue light under the excitation of 365 nm light source, and the highest emission peak is located at 425 nm.

Example 4:

The dual-mode fluorescent nanoparticle composite material, preparation method, and application provided in this embodiment are basically the same as those in Example 1, except that the dual-mode fluorescent nanoparticle composite material is specifically EuSe-coated NaErF _{4 .} : Tm nanoparticle composites.

This embodiment provides a synthesis and preparation process of EuSe-coated NaErF ₄ :Tm nanoparticle composites, including the following steps:

(1) Weigh 1mmol of selenium powder and add it to the single-necked bottle, then add 2mL of tri-n-octylphosphorus, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, the temperature during ultrasonic treatment is controlled to be 25 ° C, the ultrasonic time is 20 minutes, the ultrasonic wave The frequency is 40KHz. Sonicate until the solution in the bottle is clear and transparent, forming the first dispersion.

(2) take by weighing the EuCl ₃ 6H ₂ O of 1mmol and add in the there-necked flask, then add the first dispersion liquid of 2mL, 3mL oleylamine, 1mL oleic acid, 30mL octadecene and 1mmol surface ligands are _NaErF of oleic acid : Cyclohexane dispersion of Tm nanoparticles, react at 280-300°C for 3 hours under argon atmosphere. After cooling to room temperature, 40 mL of acetone was added to precipitate the obtained composite material, the material was placed in a high-speed centrifuge, the centrifuge speed was set to 8000 rpm, and the centrifugation was completed to remove the lower layer of precipitate to obtain EuSe-coated NaErF ₄ : Tm nanoparticle composite material.

Example 5:

The dual-mode fluorescent nanoparticle composite material, preparation method and application provided in this embodiment are basically the same as those in Example 1, except that the dual-mode fluorescent nanoparticle composite material, specifically, EuSe-coated NaGdF ₄ : Yb, Tm nanoparticle composites.

The present embodiment provides a synthesis and preparation process of EuSe-coated NaGdF ₄ : Yb, Tm nanoparticle composite material, which includes the following steps:

(1) Weigh 1mmol of selenium powder and add it to the single-necked bottle, then add 2mL of tri-n-octylphosphorus, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, the temperature during ultrasonic treatment is controlled to be 25 ° C, the ultrasonic time is 20 minutes, the ultrasonic wave The frequency is 40KHz. Sonicate until the solution in the bottle is clear and transparent, forming the first dispersion.

(2) take by weighing the EuCl ₃ 6H ₂ O of 1mmol and add in the there-necked flask, then add the _NaGdF that the first dispersion liquid of 2mL, 3mL oleylamine, 1mL oleic acid, 30mL octadecene and 1mmol surface ligands are oleic acid : The cyclohexane dispersion of Yb, Tm nanoparticles was reacted at a high temperature of 280-300 °C for 3 hours under an argon atmosphere. After cooling to room temperature, add 40 mL of acetone to precipitate the obtained composite material, place the material in a high-speed centrifuge, set the centrifuge rotation speed to be 8000 rev/min, and finish the centrifugation to obtain the EuSe-coated NaGdF ₄ : Yb, Tm nanoparticles composite material.

Example 6:

The dual-mode fluorescent nanoparticle composite material, preparation method, and application provided in this embodiment are basically the same as those in Example 1, except that the dual-mode fluorescent nanoparticle composite material, specifically, uses PVP to improve the EuSe package The water-solubility of the NaGdF ₄ : Yb, Tm nanoparticle composite material covered; the preparation method further comprises the step of using PVP to improve the water solubility of the EuSe-coated NaGdF ₄ : Yb, Tm nanoparticle composite material:

(3) Dissolving the dual-mode fluorescent nanoparticle composite material synthesized in step (2) (EuSe-coated NaGdF ₄ : Yb, Tm nanoparticle composite material in Example 5) in a cyclohexane solution to form a first dispersion liquid ;

(4) take by weighing 0.5mmol NOBF ₄ and place it in a single-necked bottle, add 10mL of dichloromethane solution, place the single-necked bottle in an ultrasonic oscillator for ultrasonic treatment, temperature control during ultrasonic treatment is 25 ℃, ultrasonic time is 20 minutes, ultrasonic wave The frequency is 40KHz. Ultrasonic until the solution in the bottle is clear and transparent to form the second dispersion;

(5) get the first dispersion liquid of 5mL and the second dispersion liquid of 5mL in the same single-necked bottle, place the single-necked bottle in the ultrasonic oscillator for ultrasonic treatment, temperature control during ultrasonic treatment is 25 ℃, and ultrasonic time is 20 minutes , the ultrasonic frequency is 40KHz. The solution was centrifuged at 15,000 rpm to obtain a solid precipitate, and the solid precipitate was dissolved in 5-8 mL of deionized water to form a third dispersion;

(6) Weigh 0.1 mmol of polyvinylpyrrolidone and place it in a single-necked bottle, add 10 mL of deionized water and stir for 0.5 hour, and control the temperature to be 30° C. during stirring. forming a fourth dispersion;

(7) Take 2.5 mL of the third dispersion liquid and 2.5 mL of the fourth dispersion liquid and place them in a single-necked flask and stir; the temperature during stirring is controlled to be 50° C.; the time during stirring is controlled to be 24 hours to obtain a PVP-modified dual-mode fluorescent nanoparticle composite Materials (EuSe-coated NaGdF ₄ : Yb, Tm nanoparticle composites).

Similarly, this step can also improve the water solubility of the dual-mode fluorescent nanoparticle composite materials prepared in Examples 1-4.

Example 7:

This embodiment provides a specific application of the dual-mode fluorescent nanoparticle composite material in the field of anti-counterfeiting, which is used as a dual-mode fluorescent filler to prepare solid or liquid products for up/down conversion dual-mode optical anti-counterfeiting.

Specifically, this embodiment provides a process of using EuSe to coat NaGdF ₄ : Yb, Tm nanoparticle composite materials for anti-counterfeiting applications, which includes the following steps:

(1) The composite material of EuSe coated NaGdF ₄ : Yb, Tm nanoparticles synthesized as described in Example 5 is dispersed in a cyclohexane solution to form a first dispersion (which can be further prepared with other components) Printing ink);

(2) synthesizing and using PVP-modified EuSe to coat NaGdF ₄ : Yb, Tm nanoparticle composites described in Example 6 to form a second dispersion;

(3) Apply the first dispersion liquid and the second dispersion liquid evenly on different parts of the non-fluorescent paper respectively, and then place the non-fluorescent paper in a drying box to dry for 10 minutes, and control the temperature of the drying box to be 60°C. The fluorescent paper is dried and then tested for fluorescence.

As shown in Figure 4, (a) is the photo of the non-fluorescent paper coated with EuSe coated NaGdF ₄ :Yb,Tm nanoparticle composite material under natural light; (b) is under the irradiation of 365nm UV lamp, the EuSe package has been coated The photo of the non-fluorescent paper coated with NaGdF ₄ : Yb, Tm nanoparticle composite material confirms that the composite material emits blue light under the irradiation of 365 nm ultraviolet light; (c) under the irradiation of 980 nm near-infrared light, the NaGdF ₄ has been coated with EuSe : The photo of the non-fluorescent paper of the Yb, Tm nanoparticle composite material, confirming that the composite material emits violet light under the irradiation of 980 nm near-infrared light;

In other embodiments, the dual-mode fluorescent nanoparticle composite material can be used as an anti-counterfeiting filler, and can be further used with other components to make liquid anti-counterfeiting products such as printing inks and water-based coatings, and form solid anti-counterfeiting products after drying.

Example 8:

The application of the dual-mode fluorescent nanoparticle composite material provided in this example is to use it as a dual-mode fluorescent filler to prepare solid or liquid products for up/down conversion dual-mode optical information storage or information security. Specifically, the NaGdF ₄ : Yb, Tm nanoparticle composite material prepared in Example 6 was coated with PVP to improve the water-solubility of EuSe, as an anti-counterfeiting filler, and added to the water-based papermaking slurry to form non-uniformity during the papermaking forming process. , Natural anti-counterfeiting graphics, and obtain anti-counterfeiting special paper after drying.

The key point of the present invention is to coat a layer of europium selenide semiconductor on the surface of rare earth up-conversion luminescent nanoparticles, so that the two cooperate with each other. Converting visible light, the europium selenide semiconductor can emit down-transfer blue light visible to the naked eye under the irradiation of ultraviolet light. The europium selenide-coated rare earth up-conversion nano-particle composite material provided by the invention can be used in the fields of up/down conversion dual-mode optical anti-counterfeiting, information security, storage and the like. The preparation method provided by the invention has the advantages of simple steps, easy control, high repeatability and the like.

The above descriptions are merely preferred embodiments of the present invention, and do not limit the present invention in any form. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make many possible changes to the technical solution of the present invention by using the methods and technical contents disclosed above or change them into equivalent embodiments of equivalent changes. Therefore, all equivalent modifications made according to the structure, structure and principle of the present invention without departing from the content of the technical invention scheme should be covered within the protection scope of the present invention.

Claims (9)

1. A dual-mode fluorescent nanoparticle composite material is characterized in that the composite material is made of up-conversion luminescent nanoparticles and a EuSe semiconductor material, wherein the EuSe semiconductor material is uniformly coated on the surfaces of the up-conversion luminescent nanoparticles to form a heterogeneous particle structure; the composite material can emit fluorescence clearly visible to naked eyes under the excitation of two laser light sources with different wavelengths, and forms dual-mode fluorescence of up-conversion luminescence and down-conversion luminescence respectively.

2. A method of preparing the dual-mode fluorescent nanoparticle composite of claim 1, comprising the steps of:

(1) weighing selenium powder with a set amount, adding the selenium powder into a single-mouth bottle, adding tri-n-octylphosphine according to a set proportion, and placing the single-mouth bottle into an ultrasonic oscillator for ultrasonic treatment until the solution in the bottle is clear and transparent to form a first dispersion liquid;

(2) weighing a europium source with a set amount, adding the europium source into a three-neck flask, sequentially adding a first dispersion liquid, oleylamine, oleic acid, octadecene and a cyclohexane dispersion liquid of upconversion luminescent nanoparticles with surface ligands of oleic acid according to a set proportion, heating to 280-300 ℃ under the protection of argon atmosphere, reacting for 3 hours, cooling to room temperature, and adding acetone; and precipitating the sample, ultrasonically washing the sample by using acetone, and centrifugally separating the sample to obtain the EuSe-coated rare earth up-conversion luminescent nano-particles, namely the dual-mode fluorescent nano-particle composite material.

3. The method for preparing a dual mode fluorescent nanoparticle composite according to claim 2, wherein the europium source in step (2) is one of europium nitrate, europium chloride, europium acetate, and hydrates thereof.

4. The preparation method of the dual-mode fluorescent nanoparticle composite material as claimed in claim 2, wherein in the step (1), the amount of tri-n-octylphosphine is 2-3 mL relative to 1mmol of selenium powder.

5. The preparation method of the dual-mode fluorescent nanoparticle composite material as claimed in claim 2, wherein the temperature during the ultrasonic treatment in the step (1) is 15 to 35 ℃, the ultrasonic time is 20 to 40 minutes, and the frequency of the ultrasonic wave is set to be 39 to 41 KHz.

6. The method for preparing a dual mode fluorescent nanoparticle composite material according to claim 2, wherein in step (2), the amount of the first dispersion liquid is 2 to 3mL, the amount of oleylamine is 3 to 5mL, the amount of oleic acid is 1 to 2mL, the amount of octadecene is 30 to 35mL, and the amount of upconversion nanoparticles with surface ligands of oleic acid is 1 to 2mmol relative to 1mmol of europium source.

7. The method of preparing the dual-mode fluorescent nanoparticle composite of claim 2, further comprising improving the EuSe coating NaGdF using PVP ₄ The water-solubility of the Yb, Tm nano particle composite material comprises the following steps:

(3) dissolving the dual-mode fluorescent nanoparticle composite material synthesized in the step (2) in a cyclohexane solution to form a first dispersion liquid;

(4) weighing 0.5mmol NOBF ₄ Placing the mixture into a single-mouth bottle, adding 10mL of dichloromethane solution, placing the single-mouth bottle into an ultrasonic oscillator for ultrasonic treatment, wherein the temperature is controlled to be 25 ℃ during ultrasonic treatment, the ultrasonic time is 20 minutes, and the frequency of ultrasonic wave is 40 KHz; performing ultrasonic treatment until the solution in the bottle is clear and transparent to form a second dispersion liquid;

(5) placing 5mL of the first dispersion and 5mL of the second dispersion in the same single-mouth bottle, and placing the single-mouth bottle in an ultrasonic oscillator for ultrasonic treatment, wherein the temperature is controlled to be 25 ℃, the ultrasonic time is 20 minutes, and the frequency of ultrasonic waves is 40 KHz; centrifuging at 15000 r/min to obtain solid precipitate, and dissolving the solid precipitate in 5-8 mL of deionized water to form a third dispersion;

(6) weighing 0.1mmoL of polyvinylpyrrolidone, placing into a single-mouth bottle, adding 10mL of deionized water, stirring for 0.5 h, and controlling the temperature to be 30 ℃ during stirring to form a fourth dispersion;

(7) placing 2.5mL of the third dispersion and 2.5mL of the fourth dispersion in a single-mouth bottle for stirring; controlling the temperature to be 50 ℃ during stirring; the stirring time is controlled to be 24 hours, and the PVP modified dual-mode fluorescent nano-particle composite material is obtained.

8. The application of the dual-mode fluorescent nanoparticle composite material as claimed in claim 1, wherein the dual-mode fluorescent nanoparticle composite material is used as a dual-mode fluorescent filler to prepare a solid or liquid product for up/down conversion dual-mode optical anti-counterfeiting.

9. Use of the dual-mode fluorescent nanoparticle composite material of claim 1 as a dual-mode fluorescent filler for the preparation of solid or liquid products for up/down conversion dual-mode optical information storage or information security.

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