A method for manufacturing a graphene-metal nanoparticle radio frequency identification tag

Abstract

The present invention provides a method for making a graphene-metal nanoparticle radio frequency identification tag, comprising the following steps: step 1, microwave treatment of expandable graphite; step 2, mixing the graphite treated in step 1 with dihydro-levulinone to form a dispersion having a concentration of 10 mg / ml; step 3, ultrasonic stirring treatment of the dispersion obtained in step 2; step 4, centrifuging the solution treated in step 3, sieving the supernatant, removing the unpeeled large particles, forming a graphene dispersion, and then concentrating the graphene dispersion by vacuum rotary evaporation; step 5, taking sodium silver powder slurry, graphene slurry and 4-aminothiophenol, heating to 100 ° C and stirring and mixing to obtain a printing liquid; step 6, printing the radio frequency identification tag antenna on coated paper using the printing liquid obtained in step 5. The present invention effectively reduces the resistance of the antenna, improves the signal receiving efficiency of the antenna, and reduces the cost of the antenna.

Description

Technical Field

[0001] The invention belongs to the technical field of radio frequency identification tags, and in particular relates to a method for manufacturing a graphene-metal nanoparticle radio frequency identification tag. Background Art

[0002] Radio Frequency Identification (RFID) is recognized as the best way to realize the Internet of Things due to its fast reading, good confidentiality and high degree of automation. At present, the mainstream process of RFID coding is through etching. However, this method has limitations such as serious environmental pollution, cumbersome steps and low precision, which restricts its application scenarios. Printed RFID is a new technology that can directly code packaging materials through conductive ink printing, which can perfectly solve the defects of the former.

[0003] At present, printed RFID mainly uses micro-silver or nano-silver paste, but the silver powder is expensive and has oxidation and migration problems, resulting in high prices, poor stability, short lifespan and other problems for related RFID antenna products. Although the emerging graphene paste has advantages in terms of price and lifespan, it is not conductive enough to meet the needs of IoT identification.

[0004] Silver-graphene mixed slurry, with silver particles as the main conductive phase and graphene as the gap filler, can theoretically combine the advantages of both. However, due to problems such as structure and dispersibility, this type of slurry has not yet shown obvious advantages in terms of cost and conductivity, and has therefore not yet been applied to the field of printed RFID. Summary of the invention

[0005] The present invention aims to solve the above technical problems and provides a method for manufacturing a graphene-metal nanoparticle radio frequency identification tag, combining silver material and graphene material as the antenna of the radio frequency identification tag.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for manufacturing a graphene-metal nanoparticle radio frequency identification tag comprises the following steps:

[0008] Step 1, subjecting expandable graphite to microwave treatment to expand the volume of graphite;

[0009] Step 2, mixing the graphite treated in step 1 with dihydro-levoglucosyl ketone to form a dispersion with a concentration of 10 mg / ml;

[0010] Step 3, subjecting the dispersion obtained in step 2 to ultrasonic stirring at a temperature not exceeding 40° C.;

[0011] Step 4, centrifuging the solution after the treatment in step 3, taking the supernatant and sieving it to remove the unpeeled large particles to form a graphene dispersion, and then concentrating the graphene dispersion by vacuum rotary evaporation;

[0012] Step 5, taking the sodium silver powder slurry, the graphene slurry and the 4-aminothiophenol, heating them to 100° C. and stirring and mixing them to obtain a printing liquid;

[0013] Step 6: Print the RFID tag antenna on coated paper using the printing liquid obtained in step 5.

[0014] As a preferred technical solution, step 2 further comprises adding sodium hydroxide to the dispersion to neutralize it to a pH of 7.5.

[0015] As a preferred technical solution, in step 5, the weight proportions of the nano-silver powder slurry, graphene slurry and 4-aminothiophenol are: 5-7 parts of the nano-silver powder slurry, 3-4 parts of the graphene slurry, and 0.5-1 part of 4-aminothiophenol.

[0016] As a preferred technical solution, the step 6 further comprises drying at 100° C. for 20 minutes after printing.

[0017] As a preferred technical solution, the method for making a graphene-metal nanoparticle radio frequency identification tag further includes:

[0018] Step 7, performing roller pressing treatment on the RFID tag antenna;

[0019] Step 8, using conductive glue to connect the RFID chip to the RFID tag antenna by dispensing method, and heat and cure at a temperature of 100° C. for 20 minutes to form a finished RFID tag.

[0020] As a preferred technical solution, in step 7, the roller treatment conditions are: pressure 1MPa, temperature 100°C, roller speed 0.5m / min, and the thickness of the RFID tag antenna after roller treatment is 12μm, the square resistance is 1.7Ω / sq, and the connection resistance is 50Ω.

[0021] After adopting the above technical solution, the present invention has the following advantages:

[0022] (1) A method for making a graphene-metal nanoparticle radio frequency identification tag of the present invention uses a graphene-silver mixed slurry to print a radio frequency identification tag antenna, and realizes high-quality bonding between the nanosilver particles and the graphene in the slurry through a connecting molecule: 4-aminobenzenethiol is used as a connecting molecule of graphene-silver powder, and the amine group at one end of the molecule can form a strong non-covalent interaction with the graphene, while the thiol group at the other end can form a covalent bond with the silver particles. The radio frequency identification tag made by the manufacturing method of the present invention uses silver particles as the main conductive phase and graphene as a gap filler, which effectively reduces the resistance of the antenna, improves the signal receiving efficiency of the antenna, and reduces the cost of the antenna.

[0023] (2) A method for preparing a graphene-metal nanoparticle radio frequency identification tag of the present invention comprises adding sodium hydroxide to a dispersion of graphite and dihydro-levoglucosyl ketone to make the dispersion present a weak alkaline environment, which helps to adjust the Zeta potential of the graphene surface and improve the stability of the dispersion.

[0024] (3) In a method for preparing a graphene-metal nanoparticle radio frequency identification tag of the present invention, dihydro-levoglucosyl ketone is added to a graphite dispersion and stirred to prevent the graphene nanosheets from agglomerating again. Dihydro-levoglucosyl ketone is a bipolar solvent, and its Hansen solubility parameter is similar to that of graphene. It has a stronger dissolving effect on graphene than commonly used n-methylpyrrolidone (NMP), dimethylacetamide (DMF), etc., and has no biological toxicity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a radio frequency identification tag antenna;

[0026] Figure 2 Atomic force microscope topological structures of comparative example 2 (left) and this embodiment (right) after diluted spin coating. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example:

[0029] A method for manufacturing a graphene-metal nanoparticle radio frequency identification tag comprises the following steps:

[0030] Step 1: Place 100-mesh expandable graphite in a ceramic container, place it in a household microwave oven, and microwave it at 800 W for 30 seconds. The volume of the graphite is observed to expand, and the gas produced by interlayer decomposition reduces the interlayer van der Waals force of the graphite.

[0031] Step 2: Mix the graphite treated in step 1 with dihydro-levulinone to form a dispersion with a concentration of 10 mg / ml. Tests show that the dispersion is weakly acidic (pH ~ 5.5), and a trace amount of sodium hydroxide is added to neutralize it to pH ~ 7.5. The weak alkaline environment helps to adjust the Zeta potential of the graphene surface and improve the stability of the dispersion.

[0032] Step 3: The dispersion obtained in step 2 is placed in a 100W ultrasonic bath for 20 hours, and ice is continuously added during the ultrasonic bath to ensure that the temperature of the ultrasonic bath does not exceed 40°C. The solution is stirred at 600 rpm by a stirrer. Ultrasonic waves can peel expanded graphite into graphene nanosheets, and the stirring by adding dihydro-levoglucosyl ketone can prevent the graphene nanosheets from agglomerating again. Dihydro-levoglucosyl ketone is a bipolar solvent with a Hansen solubility parameter similar to that of graphene. It has a stronger dissolving effect on graphene than commonly used n-methylpyrrolidone (NMP), dimethylacetamide (DMF), etc., and has no biological toxicity.

[0033] Step 4: After ultrasonic treatment, the solution was centrifuged at 500 rpm for 10 minutes, and the supernatant was passed through a 300-mesh steel mesh to remove large particles that were not peeled off to form a graphene dispersion. According to the weighing result after drying, the graphene concentration under this condition was about 4.5 mg / ml. The graphene dispersion was concentrated by vacuum rotary evaporation (90°C, vacuum degree -0.09) to a concentration of 50 mg / ml.

[0034] Step 5: Take 6 parts of sodium silver powder slurry (in this example, Heraeus C8728 silver slurry with a silver content of 45%), 4 parts of graphene slurry and 0.5 parts of 4-aminothiophenol, heat to 100°C and stir to mix. 4-aminothiophenol is used as a graphene-silver powder connecting molecule. The amine group at one end of the molecule can form a strong non-covalent interaction with graphene, while the thiol group at the other end can form a covalent bond with the silver particles. The advantages of this molecule include:

[0035] (1) Amino groups form a strong non-covalent interaction with graphene, which does not destroy the two-dimensional conjugated structure of graphene and has high electron transfer efficiency.

[0036] (2) The mercapto groups form covalent bonds with the silver particles, which are stable and the interfacial electron transfer loss is almost zero.

[0037] (3) The length of the connected benzene structure is only 0.36nm. After the graphene-silver connection, the interface electron transmission is dominated by elastic tunneling, and the interface electron transmission efficiency is high. However, interface loss is the main reason for the conductivity loss of the conductive paste. At the same time, the delocalization of benzene ring electrons further improves the electron transmission efficiency. Experiments have shown that further increasing the proportion of graphene or reducing the proportion of 4-aminobenzenethiol will have a significant impact on the conductivity of the printed product.

[0038] Step 6: Select a 300-mesh screen printing plate to print the antenna on coated paper. Adjust the scraper pressure, angle, scraping speed and other parameters according to the printing results, and dry at 100°C for 20 minutes after printing. After drying, the antenna thickness is 16μm, the square resistance is 3.8Ω / sq, and the antenna structure is as follows: Figure 1 shown.

[0039] Step 7: The antenna obtained in step 6 is subjected to roller pressing. The roller pressing conditions are pressure 1MPa, temperature 100℃, roller speed 0.5m / min. After the roller pressing, the antenna thickness is 12μm and the square resistance is about 1.7Ω / sq. The resistance at the connection is 50Ω. The roller pressing process can improve the conductivity of the antenna and enhance the uniformity and wear resistance of the antenna.

[0040] Step 8: Use conductive glue (such as Heinz ABLESTIKEMI8880S) to connect the chip (such as Caravelle Onlyone minimalist chip, impedance 50Ω, operating frequency 840MHz-960MHz, unit price 0.05 yuan) to the printed antenna by dispensing method, and heat and cure at 100℃ for 20 minutes to form a Figure 1 The finished RFID tag is shown.

[0041] The production method of the above embodiment was adopted, and the variables were controlled for comparison.

[0042] Comparative Example 1: In step 5, the nano-silver powder slurry contains 75% pure silver slurry, and the other conditions are the same.

[0043] Comparative Example 2: In step 5, 4-aminothiophenol was not added, and only 6 parts of sodium silver powder slurry and 4 parts of graphene slurry were added, and the other conditions were the same.

[0044] Comparative Example 3: In step 7, the silver-graphene mixed slurry was not subjected to the roller pressure treatment process, and the other conditions were the same.

[0045] Comparative Example 4: In step 5, only 4 parts of graphene slurry were added, and the other conditions were the same.

[0046] The slurry of this embodiment and the slurry of comparative example 2 were diluted 200 times (the diluent was dihydro-levulinone) and spin-coated on a silicon wafer. Figure 2As shown, it can be seen from the atomic force microscopy that the silver particles in Comparative Example 2 are obviously agglomerated and unevenly distributed, while the silver particles are evenly distributed after adding the connecting molecules.

[0047] The printing label parameters are shown in Table 1:

[0048] Table 1 Printing label parameters

[0049]

[0050] When reading, the reader faces the antenna and performs a test every 0.5 meters. For example, 2-2.5m means that the chip information can be read normally at a distance of 2m, but cannot be read at a distance of 2.5m.

[0051] Increasing the thickness of printed materials can further reduce the square resistance of printed materials. Experiments show that when a 200-mesh grid is used, the antenna thickness is about 28μm, and the square resistance can reach 0.6Ω / sq. However, since the attenuation of RF energy is exponentially related to distance, the improvement of conductivity does not significantly improve the reading distance, but it will significantly increase the consumption and cost of slurry.

[0052] At the same time, the surface of the antennas in Comparative Example 1, Comparative Example 3 and this embodiment was lightly scraped three times with a blade. The square resistance of Comparative Example 3 increased to 60Ω / sq (increased 15 times), and the square resistance of this embodiment was 3.4Ω / s (increased two times), indicating that the roller process can improve the wear resistance of printed products. The square resistance of Comparative Example 1 increased to 6.5Ω / sq (increased 6 times), indicating that graphene can stabilize the silver particles in the printed products.

[0053] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0054] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for making a graphene-metal nanoparticle radio frequency identification tag, characterized in that: The following steps are involved: Step 1, subjecting expandable graphite to microwave treatment to expand the volume of graphite; Step 2, mixing the graphite treated in step 1 with dihydro-levoglucosyl ketone to form a dispersion with a concentration of 10 mg / ml, and adding sodium hydroxide to the dispersion to neutralize it to a pH of 7.5; Step 3, subjecting the dispersion obtained in step 2 to ultrasonic stirring at a temperature not exceeding 40° C.; Step 4, centrifuging the solution after the treatment in step 3, taking the supernatant and sieving it to remove the unpeeled large particles to form a graphene dispersion, and then concentrating the graphene dispersion by vacuum rotary evaporation; Step 5, taking a sodium silver powder slurry, a graphene slurry and 4-aminothiophenol, the weight proportions of the sodium silver powder slurry, the graphene slurry and the 4-aminothiophenol are: 5-7 parts of the sodium silver powder slurry, 3-4 parts of the graphene slurry, and 0.5-1 part of 4-aminothiophenol, heating to 100° C. and stirring and mixing to obtain a printing liquid; Step 6, using the printing liquid obtained in step 5 to print the RFID tag antenna on coated paper; Step 7, performing roller pressing treatment on the RFID tag antenna, the roller pressing treatment conditions are: pressure 1MPa, temperature 100°C, roller speed 0.5m / min, after the roller pressing treatment, the thickness of the RFID tag antenna is 12μm, the square resistance is 1.7Ω / sq, and the connection resistance is 50Ω; Step 8, using conductive glue to connect the RFID chip to the RFID tag antenna by dispensing method, and heat and cure at a temperature of 100° C. for 20 minutes to form a finished RFID tag.

2. The method for making a graphene-metal nanoparticle radio frequency identification tag according to claim 1, characterized in that: The step 6 further includes drying at 100° C. for 20 minutes after printing.

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