Preparation method and application of AgBiX2 nanocrystal
By using thiol organic reagents to prepare AgBiX2 nanocrystals, the safety and cost issues of existing methods have been solved, and nanocrystals with controllable morphology and good stability have been achieved, expanding their application in the field of electromagnetic wave absorption, especially showing high-efficiency absorption performance in the Ku and K bands.
Patent Information
- Application Number
- CN202511301773.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-12
- Publication Date
- 2025-12-12
AI Technical Summary
Existing methods for synthesizing AgBiX2 nanocrystals are complex and costly, use highly toxic raw materials, have poor nanocrystal stability, and lack control over morphology and size. Their applications are limited to photoelectric conversion and thermoelectric fields, and have not been fully developed in the field of electromagnetic wave absorption.
Using thiol organic reagents as green solvents and ligands, AgBiX2 nanocrystals with controllable morphology and good stability were prepared through low-temperature dissolution and reactivity control. These nanocrystals were then applied to electromagnetic wave absorbing materials, exhibiting particularly excellent performance in the Ku and K bands.
A safe and economical method for synthesizing nanocrystals was achieved, resulting in AgBiX2 nanocrystals with uniform size and good monodispersity, which possess excellent electromagnetic wave absorption performance, thus expanding their application in electromagnetic shielding and stealth technology.
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Figure CN121107459A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of nanomaterial preparation, and particularly relates to a preparation method and application of AgBiX2 nanocrystals. BACKGROUND
[0002] With the rapid development of the fifth generation mobile communication technology (5G), the Internet of Things and military stealth technology, electromagnetic wave signals in space are increasingly dense, and the problem of electromagnetic radiation pollution caused thereby is becoming increasingly serious, which not only poses a potential threat to human health, but also seriously affects the accuracy and stability of electronic devices. Therefore, developing new wave-absorbing materials that can efficiently absorb electromagnetic waves and have the characteristics of "thin, light, wide and strong" has become a hot spot and an urgent need of current research.
[0003] At present, the traditional wave-absorbing materials widely studied mainly include ferrite, carbon material and MXene. Ferrite material mainly relies on magnetic loss mechanism, although it has strong absorption capacity, but has the shortcomings of large density, sharp performance attenuation at high frequency, narrow absorption frequency band, etc. Carbon materials (such as graphene, carbon nanotubes) are known for their lightweight and high electrical conductivity, but they have poor impedance matching, are easy to form surface reflection, and the loss mechanism of pure carbon materials is single. Although emerging two-dimensional materials such as MXene exhibit excellent electrical conductivity and controllability, their preparation process is complex, the cost is high, and the environmental stability is insufficient. These limitations to a large extent limit their wide application.
[0004] AgBiX2 (X = S, Se) as a I-V-VI ternary chalcogenide semiconductor material has attracted attention due to its high atomic number of constituent elements and the characteristics of narrow band gap and high carrier mobility of the material itself. These characteristics make it have great application potential in the fields of photoelectric detectors, solar cells and thermoelectric conversion, and there have been many reports on related synthesis and application research.
[0005] Although AgBiX2 material shows great potential, the synthesis of high-quality nanocrystals still faces severe challenges, which restricts its application exploration in various fields, especially in the emerging field of electromagnetic wave absorption.
[0006] The existing synthesis methods mainly have the following problems:
[0007] First, the method is complex and costly. The widely used hot injection method usually requires complex equipment (such as Schlenk line) and strict inert atmosphere protection, and often uses expensive and toxic precursors such as hexamethyldisilthiane as a sulfur source or selenium source, which not only greatly increases the production cost and process difficulty, but also brings huge safety and environmental risks. The hydrothermal / solvothermal method has the problems of high reaction temperature, long reaction time, high energy consumption and easy generation of impurities (such as Ag2S and Bi2S3).
[0008] Second, the nanocrystals are not stable enough. The prepared AgBiX2 colloidal nanocrystals are prone to surface oxidation and decomposition into Ag2X and Bi2S3 under oxygen and light, resulting in rapid degradation of their photoelectric properties and poor storage stability. Although some studies have attempted to passivate surface defects by post-injection of metal halides, this method increases the complexity of the process steps and introduces additional metal ions, which may have unpredictable effects on the intrinsic properties of the nanocrystals.
[0009] Third, the morphology and size are not controllable. Many methods (such as some solvothermal methods) have poor control over reaction kinetics, making it difficult to obtain nanocrystals with uniform size and good monodispersity, which directly affects the uniformity and repeatability of material properties. In addition, some "low-temperature one-step methods" aimed at reducing reaction conditions generally face the problem of poor controllability of morphology and size, making it difficult to obtain products with good monodispersity and high purity, which directly affects the uniformity and reliability of material properties.
[0010] Fourth, the application field is limited. So far, almost all studies on AgBiX2 nanocrystals have focused on photoelectric conversion and thermoelectricity, and the development of their synthesis methods has also served these applications. There is no research on the application of AgBiX2 nanocrystals in the field of electromagnetic wave absorption, and its great potential for wave absorption has not been explored.
[0011] Therefore, it is of great innovation value and necessity to develop a general synthesis method that can avoid the use of highly toxic raw materials from the source, is simple and green, can simultaneously achieve excellent morphology control and environmental stability, and can provide performance guarantees for new electromagnetic wave absorption applications. SUMMARY
[0012] To solve the above technical problems, the present application provides a preparation method and application of AgBiX2 nanocrystals.
[0013] The present application provides a simple and controllable method for synthesizing AgBiX2 nanocrystals without the use of highly toxic raw materials. The method uses thiol organic reagents as green solvents and ligands, effectively solving the problems of low-temperature dissolution and reaction activity control of X sources (especially Se sources).
[0014] The more important purpose of the present application is to apply AgBiX2 as a new and efficient electromagnetic wave absorption material for the first time, disclose its excellent electromagnetic wave absorption performance in the microwave band, especially in the Ku and K bands, and expand the application of AgBiX2 nanomaterials in electromagnetic shielding and stealth technology.
[0015] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:
[0016] A preparation method of AgBiX2 nanocrystals, wherein X is one or both of S and Se, the preparation method comprising the following steps:
[0017] I. uniformly mixing a silver source, a bismuth source and a high-boiling non-coordinating solvent, degassing, and then heating to 90-120 DEG C under an inert atmosphere and maintaining for a period of time to obtain a transparent solution I;
[0018] II. uniformly mixing X elemental powder, a thiol organic reagent and oleylamine, heating and stirring until completely dissolved to obtain a solution II;
[0019] III. under the protection of an inert atmosphere and stirring, injecting the solution II at a temperature of 50-70 DEG C into the solution I at a temperature of 90-100 DEG C;
[0020] IV. after the reaction is completed, cooling to room temperature, and then centrifuging, washing and drying to obtain the AgBiX2 nanocrystals.
[0021] Compared with the prior art, the present application has the following remarkable beneficial effects:
[0022] I. Innovation and advantages in the synthesis method:
[0023] Safety, low toxicity, economic efficiency: compared with the traditional method using highly toxic or expensive precursors, the present application innovatively uses a thiol organic reagent as a green solvent and reaction medium, successfully realizes low-temperature and high-efficiency dissolution and conversion of solid-state sulfur / selenium powder, and completely eliminates high safety risks and high-cost raw materials, thereby realizing the safety and economy of synthesis from the source.
[0024] Controllable morphology, good stability: compared with the prior art which may lead to uneven morphology or requires complex post-treatment, the present application effectively regulates the nucleation and growth process of the nanocrystals through the synergistic coordination of the thiol reagent and oleylamine, and high-quality AgBiX2 nanocrystals with uniform size and good monodispersity can be obtained in one step. The obtained product benefits from a stable surface state and exhibits excellent environmental stability without any post-passivation treatment.
[0025] Simple process, easy to scale up: the method described in the present application has simple steps, low equipment requirements, mild reaction conditions, high repeatability and reliability, and overcomes the shortcomings of complex process routes and difficult control in some prior art, and is more suitable for large-scale production.
[0026] II. Breakthrough in application performance:
[0027] Exploiting new application fields: the present application first discloses the great potential of AgBiX2 nanocrystals in electromagnetic wave absorption, especially high-frequency microwave absorption, and fills the research gap of this material in the wave absorption field.
[0028] Excellent comprehensive wave-absorbing performance: thanks to the dielectric loss caused by the narrow band gap and high mobility of the AgBiX2 nanocrystals, as well as the strong polarization relaxation caused by the large specific surface area and interface effect under nanoscale, the composite wave-absorbing material exhibits extremely strong absorption intensity (the reflection loss RL can be lower than -40 dB), wide effective absorption bandwidth and relatively thin matching thickness (< 2 mm).
[0029] Rich loss mechanisms: the nanocrystal wave-absorbing agent has multiple loss mechanisms such as conductive loss, dielectric polarization loss and interface polarization loss, which synergistically work to achieve high-efficiency and wide-band wave-absorbing. BRIEF DESCRIPTION OF DRAWINGS
[0030] Figure 1 is a preparation process flow chart of AgBiX2 nanocrystals of the present application;
[0031] Figure 2 is an X-ray diffraction pattern of AgBiSe2 nanocrystals prepared in Example 1;
[0032] Figure 3 is a transmission electron microscope photo of AgBiSe2 nanocrystals prepared in Example 1;
[0033] Figure 4 is an electromagnetic wave absorption performance chart of electromagnetic wave absorption composite material of AgBiSe2 / carbon nanotube electromagnetic wave absorption composite material prepared in Example 3;
[0034] Figure 5 is an X-ray diffraction pattern of AgBiS2 nanocrystals prepared in Example 2;
[0035] Figure 6 is a transmission electron microscope photo of AgBiS2 nanocrystals prepared in Example 2;
[0036] Figure 7 is an electromagnetic wave absorption performance chart of electromagnetic wave absorption composite material of AgBiS2 / carbon nanotube electromagnetic wave absorption composite material prepared in Example 3. DETAILED DESCRIPTION
[0037] Detailed implementation one: a preparation method of AgBiX2 nanocrystals, wherein X is one or both of S and Se in the AgBiX2, and the preparation method comprises the following steps:
[0038] I. uniformly mix a silver source, a bismuth source and a high-boiling non-coordinating solvent, degas, then heat to 90-120℃ under inert atmosphere and keep for a period of time to obtain transparent solution I;
[0039] II. Mixing X element powder, mercaptan organic reagent and oleylamine uniformly, heating and stirring until completely dissolved to obtain solution II;
[0040] III. Under the protection of inert atmosphere and stirring, solution II with a temperature of 50-70℃ is injected into solution I with a temperature of 90-100℃;
[0041] IV. After the reaction is completed, cooling to room temperature, and then centrifugal washing and drying to obtain the AgBiX2 nanocrystals.
[0042] The present embodiment uses mercaptan organic reagent to replace traditional toxic or expensive precursors, realizes low-toxicity, low-temperature and high-efficiency dissolution of X source, and successfully prepares AgBiX2 (X: S, Se) nanocrystals with controllable morphology, good dispersion and air stability through hot injection reaction. The method has a simple reaction process, and overcomes many defects of existing methods in safety, cost and process. More importantly, the prepared AgBiX2 nanocrystals are applied as electromagnetic wave absorbers for the first time, and experiments show that after being compounded with carbon materials, they exhibit extremely strong absorption characteristics, wide effective absorption bandwidth and thin matching thickness in the frequency band of 2-18 GHz, and have great application potential in electromagnetic shielding and stealth coating.
[0043] Specific implementation method two: the difference between the present embodiment and the specific implementation method one is that the silver source in step one is silver nitrate, silver acetate or silver acetylacetone; the bismuth source in step one is bismuth nitrate, bismuth chloride or bismuth acetate; and the high-boiling non-coordinating solvent in step one is 1-octadecene or liquid paraffin. The other steps are the same as those in the specific implementation method one.
[0044] Specific implementation method three: the difference between the present embodiment and one of the specific implementation method one or two is that the molar ratio of the silver source to the bismuth source in step one is 0.8: (1.0-1.2); the amount-of-substance ratio of the silver source to the volume of the high-boiling non-coordinating solvent in step one is 0.8 mmol: (10 mL-20 mL); and the X element powder in step two is sulfur powder or selenium powder. The other steps are the same as those in the specific implementation method one or two.
[0045] Specific implementation method four: the difference between the present embodiment and one of the specific implementation methods one to three is that the mercaptan organic reagent in step two is alkyl mercaptan; and the alkyl mercaptan is ethanedithiol, n-octyl mercaptan, dodecanethiol or octadecanethiol. The other steps are the same as those in the specific implementation methods one to three.
[0046] Embodiment five: the difference between this embodiment and one of embodiments one to four is that the molar ratio of the X single-element powder in step two to the silver source in step one is 2:(0.8-1.2); the molar ratio of the thiol organic reagent in step two to oleylamine is (0.5-2):1; the volume ratio of the amount of substance of the X single-element powder in step two to the thiol organic reagent is 2 mmol:(3 mL-5 mL). The other steps are the same as embodiments one to four.
[0047] Embodiment six: the difference between this embodiment and one of embodiments one to five is that the holding time in step one is 90 min-120 min; the heating temperature in step two is 50℃-70℃; the inert atmosphere in steps one and three is nitrogen. The other steps are the same as embodiments one to five.
[0048] Embodiment seven: this embodiment is an AgBiX2 nanocrystal for preparing an electromagnetic wave absorbing composite material, and the electromagnetic wave absorbing composite material is applied in electromagnetic shielding materials, stealth coating or microwave absorption devices.
[0049] Embodiment eight: the difference between this embodiment and one of embodiments one to seven is that an AgBiX2 nanocrystal is compounded with a carbon material to prepare an electromagnetic wave absorbing composite material. The other steps are the same as embodiments one to seven.
[0050] Embodiment nine: the difference between this embodiment and one of embodiments one to eight is that the carbon material is one or more of carbon nanotubes, graphene, carbon fibers and carbon black; the mass fraction of the AgBiX2 nanocrystal in the electromagnetic wave absorbing composite material is 10%-70%. The other steps are the same as embodiments one to eight.
[0051] Embodiment ten: the difference between this embodiment and one of embodiments one to nine is that the electromagnetic wave absorbing composite material has significant electromagnetic wave absorption performance in the 2-18 GHz microwave frequency band. The other steps are the same as embodiments one to nine.
[0052] The beneficial effects of the present application are verified by the following examples:
[0053] Example 1: a preparation method of an AgBiX2 nanocrystal, comprising the following steps:
[0054] I. In a 100 mL three-necked round-bottom flask, 0.8 mmol of silver acetate (Ag(OAc), 99.5%), 1.0 mmol of bismuth acetate (Bi(OAc)3, 99.9%) and 20 mL of 1-octadecene (ODE, 90.0%) were sequentially added and mixed well. The flask was connected to a Schlenk line, and vacuum-nitrogen cycles were performed three times at room temperature to remove water and low-boiling impurities. Then, the system was heated to 100°C at a rate of 5°C / min under N2atmosphere, and vacuum and stirring were continued at this temperature for 1.5 hours to obtain a transparent solution I;
[0055] II. 2 mmol of selenium powder (Se, ≥99.99%) was placed in a 20 mL glass vial, and then 3 mL of dodecanethiol (DDT, ≥98%) and 3 mL of oleylamine (OLA, 80-90%) were added to the vial and mixed well. The mixture was stirred at 50°C until the selenium powder was completely dissolved to obtain a solution II.
[0056] III. Under the protection of nitrogen atmosphere and stirring at 2000 rpm, the solution II at 50°C was injected into the solution I at 100°C.
[0057] IV. After the reaction was completed, the system was cooled to room temperature to obtain a reaction solution. Then, 20 mL of acetone was added to the reaction solution, and the mixture was centrifuged at 6000 rpm for 5 minutes. The supernatant was discarded, and the collected precipitate was redispersed in a mixed solvent of toluene / acetone (volume ratio 1:3) and centrifuged. This purification process was repeated three times. Finally, the obtained black precipitate was placed in a vacuum drying oven and dried at room temperature for 30 minutes to obtain black powder-shaped AgBiSe2nanocrystals with a yield of about 0.28 g.
[0058] Example 2: A method for preparing AgBiX2nanocrystals, comprising the following steps:
[0059] I. In a 100 mL three-necked round-bottom flask, 0.8 mmol of silver acetate (Ag(OAc), 99.5%), 1.0 mmol of bismuth acetate (Bi(OAc)3, 99.9%) and 20 mL of 1-octadecene (ODE, 90.0%) were sequentially added and mixed well. The flask was connected to a Schlenk line, and vacuum-nitrogen cycles were performed three times at room temperature to remove water and low-boiling impurities. Then, the system was heated to 100°C at a rate of 5°C / min under N2atmosphere, and vacuum and stirring were continued at this temperature for 1.5 hours to obtain a transparent solution I;
[0060] II. 2 mmol of sulfur powder (S, ≥99.99%) was placed in a 20 mL glass vial, then 3 mL of dodecanethiol (DDT, ≥98%) and 3 mL of oleylamine (OLA, 80-90%) were added into the vial and mixed well; the solution II was prepared by continuously stirring at 50°C until the selenium powder was completely dissolved;
[0061] III. The solution II at 50°C was injected into the solution I at 100°C under the protection of nitrogen atmosphere and stirring at 2000 rpm;
[0062] IV. After the reaction was completed, the reaction solution was cooled to room temperature; 20 mL of acetone was added into the reaction solution, and the mixture was centrifuged at 6000 rpm for 5 min; the supernatant was discarded, and the collected precipitate was redispersed in a mixed solvent of toluene / acetone (1:3 by volume) and centrifuged; the purification process was repeated for 3 times; finally, the obtained black precipitate was placed in a vacuum drying oven and dried at room temperature for 30 min, and finally the black powder of AgBiS2 nanocrystals was obtained.
[0063] Example 3: Electromagnetic wave absorption performance test:
[0064] I. Preparation of AgBiSe2 / carbon nanotube electromagnetic wave absorption composite material:
[0065] The dried AgBiSe2 nanocrystal powder prepared in Example 1 was mixed with carbon nanotubes at a mass ratio of 1:1, and ultrasonic dispersion was performed for half an hour to ensure uniform mixing, thereby obtaining an AgBiSe2 / carbon nanotube electromagnetic wave absorption composite material; the AgBiSe2 / carbon nanotube electromagnetic wave absorption composite material was mixed with a paraffin matrix to obtain a mixture (the mass fraction of the AgBiSe2 / carbon nanotube electromagnetic wave absorption composite material in the mixture was 25%); the mixture was pressed into a coaxial ring sample with an inner diameter of 3.0 mm and an outer diameter of 7.0 mm;
[0066] II. Preparation of AgBiS2 / carbon nanotube electromagnetic wave absorption composite material:
[0067] The dried AgBiS2 nanocrystal powder prepared in Example 2 was mixed with carbon nanotubes at a mass ratio of 1:1, and ultrasonic dispersion was performed for half an hour to ensure uniform mixing, thereby obtaining an AgBiS2 / carbon nanotube electromagnetic wave absorption composite material; the AgBiS2 / carbon nanotube electromagnetic wave absorption composite material was mixed with a paraffin matrix to obtain a mixture (the mass fraction of the AgBiS2 / carbon nanotube electromagnetic wave absorption composite material in the mixture was 38%); the mixture was pressed into a coaxial ring sample with an inner diameter of 3.0 mm and an outer diameter of 7.0 mm;
[0068] The S parameters (S11 and S21) of the coaxial ring are tested in the frequency range of 2-18 GHz by using a vector network analyzer (VNA), and the reflection loss (RL) value is calculated by the classical transmission line theory. The RL value is calculated according to the following formula:
[0069] wherein, Z0 is the impedance of free space (377 Ω), Z in is the input impedance.
[0070] The test results show that:
[0071] AgBiSe2 composite material: when the matching thickness is 2.0 mm, the maximum reflection loss value (RL min ) is -49.85 dB at 10.0 GHz, and the effective absorption bandwidth (RL < -10 dB) is 2.44 GHz.
[0072] AgBiS2 composite material: when the matching thickness is 2.0 mm, the maximum reflection loss value is -43.94 dB at 10.44 GHz, and the effective absorption bandwidth is 2.64 GHz.
[0073] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art, according to the technical solution and the inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.
Claims
1. A method for preparing AgBiX2 nanocrystals, characterized in that, X is one or both of S and Se, and the preparation method comprises the following steps: I. uniformly mixing a silver source, a bismuth source and a high-boiling non-coordinating solvent, degassing, and then heating to 90-120 DEG C under an inert atmosphere and maintaining for a period of time to obtain a transparent solution I; II. uniformly mixing X elemental powder, a thiol organic reagent and oleylamine, and heating and stirring until completely dissolved to obtain a solution II; III. under the protection of an inert atmosphere and stirring, injecting the solution II at a temperature of 50-70 DEG C into the solution I at a temperature of 90-100 DEG C; IV. after the reaction is completed, cooling to room temperature, and then centrifuging, washing and drying to obtain the AgBiX2 nanocrystals.
2. The method for preparing AgBiX2 nanocrystals according to claim 1, characterized in that, The silver source in step I is silver nitrate, silver acetate or silver acetylacetone; the bismuth source in step I is bismuth nitrate, bismuth chloride or bismuth acetate; and the high-boiling non-coordinating solvent in step I is 1-octadecene or liquid paraffin.
3. The method for preparing AgBiX2 nanocrystals according to claim 1, characterized in that, The molar ratio of the silver source to the bismuth source in step I is 0.8: (1.0-1.2); the volume ratio of the silver source to the high-boiling non-coordinating solvent in step I is 0.8 mmol: (10-20 mL); and the X elemental powder in step II is sulfur powder or selenium powder.
4. The method for preparing AgBiX2 nanocrystals according to claim 1, characterized in that, The thiol organic reagent in step II is an alkyl mercaptan; and the alkyl mercaptan is ethanedithiol, n-octyl mercaptan, dodecanethiol or octadecanethiol.
5. The method for preparing AgBiX2 nanocrystals according to claim 1, characterized in that, The molar ratio of the X elemental powder to the silver source in step II is 2: (0.8-1.2); the molar ratio of the thiol organic reagent to oleylamine in step II is (0.5-2):1; and the volume ratio of the X elemental powder to the thiol organic reagent in step II is 2 mmol: (3-5 mL).
6. The method for preparing AgBiX2 nanocrystals according to claim 1, characterized in that, The time for maintaining in step I is 90-120 min; the heating temperature in step II is 50-70 DEG C; and the inert atmosphere in steps I and III is nitrogen.
7. Use of AgBiX2 nanocrystals prepared according to the method of claim 1, characterized in that, An AgBiX2 nanocrystal is used for preparing an electromagnetic wave absorbing composite material, and the electromagnetic wave absorbing composite material is applied in electromagnetic shielding materials, stealth coating or microwave absorbing devices.
8. Use of AgBiX2 nanocrystals according to claim 7, characterized in that An AgBiX2 nanocrystal is compounded with a carbon material to prepare an electromagnetic wave absorbing composite material.
9. Use of AgBiX2 nanocrystals according to claim 8, characterized in that, The carbon material is one or more of carbon nanotubes, graphene, carbon fibers and carbon black; and the mass fraction of the AgBiX2 nanocrystals in the electromagnetic wave absorbing composite material is 10-70%.
10. Use of AgBiX2 nanocrystals according to claim 8, characterized in that, The electromagnetic wave absorbing composite material has significant electromagnetic wave absorbing performance in the 2-18 GHz microwave frequency band.