Composite nanoparticles, their preparation methods and applications

Abstract

This invention relates to the field of nanomaterials, and discloses a composite nanoparticle, its preparation method, and its application. The preparation method includes: mixing noble metal nanoparticles with an organic synthetic oil and then heating the mixture to react; wherein the organic synthetic oil contains at least one selected from biphenyl compounds, hydrogenated products of biphenyl compounds, biphenyl ether compounds, and alkyl aromatic hydrocarbons. The composite nanoparticle includes a core and a shell covering the core; the core is a noble metal nanoparticle, and the shell is carbon quantum dots; wherein the carbon quantum dots are carbonized products of the organic synthetic oil; and the organic synthetic oil contains at least one selected from biphenyl compounds, hydrogenated products of biphenyl compounds, biphenyl ether compounds, and alkyl aromatic hydrocarbons. This composite nanomaterial exhibits excellent stability and light absorption properties.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials, specifically to a composite nanoparticle, its preparation method, and its application. Background Technology

[0002] Rapid industrial development has brought about a global energy crisis and increasingly serious environmental problems. Vigorously developing renewable energy is the main direction for achieving low-carbon technologies. Solar energy, as a renewable energy source with abundant reserves, has the advantages of being green and clean. Solar thermal utilization is the most common method of solar energy utilization technology. As the core component in solar thermal utilization that converts solar energy into heat energy, surface-type collectors are currently widely used. However, with technological advancements, direct absorption collectors are gaining popularity in research fields due to their superior performance. Their design concept replaces traditional media (water, heat transfer oil, etc.) with nanofluids with high light absorption properties, allowing them to capture solar radiation through volume absorption, effectively improving the photothermal conversion efficiency compared to traditional surface absorption.

[0003] To ensure efficient photothermal conversion in direct absorption solar collectors, nanofluids should possess excellent thermal stability and broad-spectrum light absorption performance. However, prolonged use, high temperatures, and irradiation can all cause nanofluids to agglomerate and settle, leading to system instability and a decrease in photothermal conversion efficiency. Furthermore, solar energy is a full-spectrum electromagnetic wave covering the ultraviolet to far-infrared region. Traditional single-component nanofluids typically only absorb light in a specific wavelength band, resulting in the waste of a large portion of solar radiation energy. In addition, currently widely used methods for improving the stability of nanofluids are mainly divided into two categories: physical dispersion (mechanical ultrasonication, dispersants) and chemical dispersion (particle modification). Physical dispersion is simple to operate but has a short shelf life, is easily affected by environmental factors and quickly fails, and has poor dispersion effects. Chemical dispersion offers superior performance but is complex and time-consuming, and the results are random, making it difficult to replicate in large quantities.

[0004] Therefore, there is an urgent need to provide a composite nanoparticle that can simultaneously achieve both broad-spectrum light absorption performance and long-term stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor stability and poor light absorption performance of existing nanofluids, and to provide a composite nanoparticle, its preparation method and application, which has excellent stability and light absorption performance.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing composite nanoparticles, the method comprising: mixing noble metal nanoparticles with organic synthetic oil and then heating the mixture to react; wherein the organic synthetic oil contains at least one of biphenyl compound, hydrogenated product of biphenyl compound, biphenyl ether compound and alkyl aromatic hydrocarbon.

[0007] Preferably, the organic synthetic oil is selected from... 59. 60. 62. 66. VP-1 and At least one of LT, more preferably 66.

[0008] Preferably, the precious metal is at least one selected from gold, silver, platinum, copper and palladium, more preferably gold and / or silver.

[0009] Preferably, the particle size of the noble metal nanoparticles is 5-16 nm.

[0010] Preferably, the conditions for the heating reaction include at least: a temperature of 140-160°C and a time of 10-30 hours.

[0011] Preferably, the weight ratio of the noble metal nanoparticles to the organic synthetic oil is 1×10⁻⁶. -5 -5×10 -5 :1.

[0012] Preferably, the heating reaction is carried out in a closed container.

[0013] Preferably, before the heating reaction, the volume ratio of the organic synthetic oil to the sealed container is 0.3-0.5:1.

[0014] Preferably, the mixing is ultrasonic mixing.

[0015] Preferably, the conditions for ultrasonic mixing include at least: ultrasonic power of 100-200W and time of 5-15min.

[0016] A second aspect of the present invention provides a composite nanoparticle, the composite nanoparticle comprising a core and a shell covering the core; the core is a noble metal nanoparticle, and the shell is a carbon quantum dot; wherein the carbon quantum dot is a carbonization product of an organic synthetic oil; the organic synthetic oil contains at least one of a biphenyl compound, a hydrogenation product of a biphenyl compound, a biphenyl ether compound, and an alkyl aromatic hydrocarbon.

[0017] Preferably, the organic synthetic oil is selected from... 59. 60. 62. 66. VP-1 and At least one of LT, more preferably 66.

[0018] Preferably, the precious metal is at least one of gold, silver, platinum, and copper, and more preferably gold and / or silver.

[0019] Preferably, the particle size of the noble metal nanoparticles is 5-16 nm.

[0020] Preferably, the particle size of the composite nanoparticles is 6-17 nm.

[0021] The third aspect of the present invention provides the application of composite nanoparticles obtained by the preparation method described in the first aspect and / or composite nanoparticles described in the second aspect in solar collectors.

[0022] The technical effects of the present invention through the above technical solution are as follows:

[0023] The method for preparing composite nanomaterials provided by this invention involves mixing noble metal nanoparticles with organic synthetic oil and then heating the mixture. The organic synthetic oil contains at least one of biphenyl compounds, hydrogenated products of biphenyl compounds, biphenyl ether compounds, and alkyl aromatic hydrocarbons. During the preparation process, carbon quantum dots formed by the organic synthetic oil interact with the noble metal nanoparticles through chemical bonds, forming a core-shell structure with noble metal nanoparticles in the core and carbon quantum dots in the shell. This effectively improves the stability of the composite nanoparticles and allows for the superposition of the light absorption properties of single noble metal nanoparticles and carbon quantum dots, thereby significantly enhancing the light absorption and photoelectric conversion performance of the composite nanoparticles.

[0024] The composite nanoparticles provided by this invention have a core of noble metal nanoparticles and a shell of carbon quantum dots formed by organic synthetic oil. Through the chemical bonding between the noble metal nanoparticles and the carbon quantum dots formed by organic synthetic oil, a core-shell structure is formed, which effectively improves the stability of the composite nanoparticles. Furthermore, it can superimpose the light absorption properties of a single noble metal nanoparticle and carbon quantum dots, thereby greatly improving the light absorption and photoelectric conversion performance of the composite nanoparticles. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the Au-CQDs / T66 composite nanoparticles prepared in Example 1;

[0026] Figure 2 The fluorescence imaging and emission spectra of the Au-CQDs / T66 composite nanoparticles prepared in Example 1 are shown below.

[0027] Figure 3 The absorption spectrum of the Au-CQDs / T66 composite nanoparticles prepared in Example 2 is shown below.

[0028] Figure 4The graph shows the relationship between the solar energy weighted absorption fraction and concentration of the Au-CQDs / T66 composite nanoparticles prepared in Example 1.

[0029] Figure 5 For testing the Au / tT66 nanofluid, Au-CQDs / T66 composite nanoparticles, CQDs nanomaterials and... 66. Heating-cooling curves during photothermal conversion. Detailed Implementation

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] The first aspect of the present invention provides a method for preparing composite nanoparticles, the method comprising: mixing noble metal nanoparticles with organic synthetic oil and then heating the mixture to react; wherein the organic synthetic oil contains at least one of biphenyl compound, hydrogenated product of biphenyl compound, biphenyl ether compound and alkyl aromatic hydrocarbon.

[0032] During their research, the inventors discovered that the carbon quantum dots formed by organic synthetic oil interact with the noble metal nanoparticles through chemical bonds, forming a core-shell structure with noble metal nanoparticles in the core and carbon quantum dots in the shell. This effectively improves the stability of the composite nanoparticles and allows for the superposition of the light absorption properties of single noble metal nanoparticles and carbon quantum dots, thus greatly enhancing the light absorption performance of the composite nanoparticles and improving their photothermal conversion performance.

[0033] In this invention, the biphenyl compound is terphenyl, tetraphenyl, pentadiphenyl, a derivative of terphenyl, a derivative of tetraphenyl, and a derivative of pentadiphenyl. For example, the biphenyl compound is terphenyl, tetraphenyl, or pentadiphenyl.

[0034] In this invention, the hydrogenation product of the biphenyl compound can be a fully hydrogenated product or a partially hydrogenated product. For example, the hydrogenation product of the biphenyl compound can be a hydrogenated terphenyl, a hydrogenated tetraphenyl, or a hydrogenated pentphenyl. Specifically, when the hydrogenation product of the biphenyl compound is a hydrogenated terphenyl, the hydrogenated terphenyl is obtained by partially hydrogenating a mixture of ortho-, meta-, and para-terphenyls in different proportions. For example, the structural formula of the hydrogenated terphenyl can be:

[0035]

[0036] In this invention, the diphenyl ether compound can be a diphenyl ether or a derivative thereof. For example, the diphenyl ether compound can be a diphenyl ether or an alkyl diphenyl ether.

[0037] In this invention, the alkyl aromatic hydrocarbon can be a monoalkyl aromatic hydrocarbon or a polyalkyl aromatic hydrocarbon; for example, the alkyl aromatic hydrocarbon can be at least one of C7, C8, C9 and C10 aromatic hydrocarbons.

[0038] According to the present invention, preferably, the organic synthetic oil is selected from... 59. 60. 62. 66. VP-1 and At least one of LT, more preferably 66. The inventors discovered that, under this preferred embodiment, the extinction properties and high-temperature stability of carbon quantum dots formed by local carbon chain breakage in organic synthetic oils can be improved. The carbon quantum dots and noble metal nanoparticles form a core-shell structure by electrostatic attraction that induces the condensation of chemical bonds, resulting in composite nanoparticles with excellent stability and light absorption, thereby improving the photoelectric conversion performance of the composite nanoparticles.

[0039] According to the present invention, preferably, the noble metal is at least one selected from gold, silver, platinum, copper, and palladium, more preferably gold and / or silver, and even more preferably gold. The inventors have discovered that, under this preferred embodiment, the localized surface plasmon resonance (LSPR) of the noble metal nanoparticles can be improved, thereby enhancing the light absorption and photothermal conversion properties of the composite nanoparticles through their combination with carbon quantum dots.

[0040] According to the present invention, the different particle sizes of noble metal nanoparticles result in different attractive forces on carbon quantum dots, leading to variations in the coating of the noble metal nanoparticles by the carbon quantum dots (coating rate, coating integrity, etc.), and consequently, different particle sizes and properties of the resulting composite nanoparticles. To further improve the stability and light absorption of the composite nanoparticles, preferably, the particle size of the noble metal nanoparticles is 5-16 nm, specifically 5 nm, 10 nm, 16 nm, or any value between the aforementioned two.

[0041] In this invention, the noble metal nanoparticles can be spherical or non-spherical; specifically, when the noble metal nanoparticles are non-spherical, their shape can be rod-shaped, star-shaped, cage-shaped, or bipyramidal. To further improve the light absorption and photothermal conversion performance of the composite nanoparticles, it is preferable that the noble metal nanoparticles are spherical.

[0042] According to the present invention, in order to improve the reaction efficiency and product yield of the heating reaction, preferably, the heating reaction conditions include at least: a temperature of 140-160°C, specifically 140°C, 150°C, 160°C, or any value between the two aforementioned values; a time of 10-30 hours, specifically 10 hours, 20 hours, 30 hours, or any value between the two aforementioned values; and the container containing the reactants can be heated by a bottom-up heating method. The inventors have discovered that, under this preferred embodiment, the process of the generated carbon quantum dots aggregating from micro carbon dots onto the surface of noble metal nanoparticles can be precisely controlled, thereby controlling and adjusting the particle size of the composite nanoparticles.

[0043] According to the present invention, if the amount of carbon quantum dots is too small, the outer shell cannot completely coat the surface of the noble metal nanoparticles, and the noble metal nanoparticles that have not formed a coating are prone to agglomeration and sedimentation. If the amount of carbon quantum dots is too large, the outer shell of the noble metal nanoparticles is too thick, which weakens the extinction performance of the composite nanoparticles. At the same time, the large surface energy also makes the composite nanoparticles prone to agglomeration. Too much or too little carbon quantum dots affects both the stability and light absorption performance of the composite nanoparticles. To further improve the stability and light absorption of the composite nanoparticles, preferably, the weight ratio of the noble metal nanoparticles to the organic synthetic oil is 1×10⁻⁶. -5 -5×10 -5 :1, specifically 1×10 -5 1, 2×10 -5 1, 3×10 -5 1. 4×10 -5 1.5×10 -5 : 1, or any value between the two aforementioned values.

[0044] According to the present invention, in order to further improve the efficiency of the heating reaction and the yield of the product, preferably, the heating reaction is carried out in a closed container.

[0045] According to the present invention, when a certain mass of organic synthetic oil is added to a sealed container before the heating reaction, the organic synthetic oil occupies a corresponding volume in the sealed container, leaving air in the remaining volume. To further improve the efficiency of the heating reaction and the product yield, preferably, before the heating reaction, the volume ratio of the organic synthetic oil to the sealed container is 0.3-0.5:1, specifically 0.3:1, 0.4:1, 0.5:1, or any value between the aforementioned two. It should be noted that "before the heating reaction" refers to mixing the organic synthetic oil and precious metal nanoparticles in a sealed container at room temperature and pressure, such that the volume ratio of the organic synthetic oil to the sealed container is 0.3-0.5:1. Room temperature and pressure typically refer to a temperature of 25°C and a pressure of 1 atmosphere. The inventors discovered that by adjusting the volume ratio of organic synthetic oil to the sealed container and then heating the reaction in a closed container, the longer the reaction time, the greater the change in particle size of the obtained nanocomposite particles, thus enabling the adjustment of the particle size of the prepared nanocomposite particles.

[0046] In this invention, in order to facilitate the control of the volume ratio of organic synthetic oil to the sealed container, a cylindrical reaction flask can be used as the sealed container. The volume ratio of organic synthetic oil to the reaction flask is the ratio of the height of the organic synthetic oil in the reaction flask to the total height inside the reaction flask.

[0047] According to the present invention, the mixing of precious metal nanoparticles and organic synthetic oil can be achieved through simple stirring or ultrasonic mixing, preferably ultrasonic mixing. The inventors have found that, in this preferred embodiment, ultrasonic mixing enables the precious metal nanoparticles to be uniformly dispersed in the organic synthetic oil, thereby further improving the reaction efficiency of the heating reaction and the yield of the product.

[0048] According to the present invention, in order to further improve the reaction efficiency of the heating reaction and the yield of the product, preferably, the ultrasonic mixing conditions include at least: ultrasonic power of 100-200W, specifically 100W, 150W, 200W, or any value between the two aforementioned values; and time of 5-15min, specifically 5min, 10min, 15min, or any value between the two aforementioned values.

[0049] According to the present invention, noble metal nanoparticles can be prepared using conventional methods in the art. In order to further improve the yield of noble metal nanoparticles, preferably, the method for preparing noble metal nanoparticles includes: reacting a noble metal salt with a reducing agent in the presence of a solvent.

[0050] In this invention, when the noble metal nanoparticles are gold nanoparticles, the noble metal salt can be chloroauric acid, the reducing agent can be oleylamine or oleic acid, and the solvent is water. Exemplarily, the preparation method of the gold nanoparticles includes: dissolving chloroauric acid in water, adding oleylamine, with a weight ratio of oleylamine to chloroauric acid of 2-4:1, heating the mixture to boiling and maintaining the boiling state for 90-120 minutes, cooling to room temperature, then adding cyclohexane to the mixture, adjusting the pH to 8-10, and allowing it to stand and separate into layers; wherein the alkaline solution used to adjust the pH is NaOH solution.

[0051] In this invention, when the noble metal nanoparticles are silver nanoparticles, the noble metal salt can be silver nitrate, the reducing agent can be trisodium citrate dihydrate, and the solvent is water. Exemplarily, the preparation method of silver nanoparticles includes: mixing an aqueous solution of silver nitrate with ammonia to obtain a silver ammonia solution; mixing glucose, sodium citrate dihydrate, polyvinylpyrrolidone, and water to obtain solution A, wherein the weight ratio of silver nitrate to sodium citrate dihydrate is 3-5:1; mixing the silver ammonia solution with solution A and heating to 90-100°C for 60-90 minutes.

[0052] A second aspect of the present invention provides a composite nanoparticle, the composite nanoparticle comprising a core and a shell covering the core; the core is a noble metal nanoparticle, and the shell is a carbon quantum dot; wherein the carbon quantum dot is a carbonization product of an organic synthetic oil; the organic synthetic oil contains at least one of a biphenyl compound, a hydrogenation product of a biphenyl compound, a biphenyl ether compound, and an alkyl aromatic hydrocarbon.

[0053] During their research, the inventors discovered that the composite nanoparticles have a core of noble metal nanoparticles and a shell of carbon quantum dots. Through the chemical bonding between the noble metal nanoparticles and the carbon quantum dots, a core-shell structure is formed, which effectively improves the stability of the composite nanoparticles. Furthermore, it can superimpose the light absorption properties of a single noble metal nanoparticle and a carbon quantum dot, thus greatly enhancing the light absorption performance of the composite nanoparticles.

[0054] In this invention, the biphenyl compound is terphenyl, tetraphenyl, pentphenyl, a derivative of terphenyl, a derivative of tetraphenyl, or a derivative of pentphenyl. For example, the biphenyl compound is terphenyl, tetraphenyl, or pentphenyl. The hydrogenation product of the biphenyl compound can be a fully hydrogenated product or a partially hydrogenated product. For example, the hydrogenation product of the biphenyl compound can be hydrogenated terphenyl, hydrogenated tetraphenyl, or hydrogenated pentphenyl. The biphenyl ether compound can be a biphenyl ether or a derivative of a biphenyl ether. For example, the biphenyl ether compound can be a biphenyl ether or an alkyl biphenyl ether. The alkyl aromatic hydrocarbon can be a monoalkyl aromatic hydrocarbon or a polyalkyl aromatic hydrocarbon. Exemplarily, the alkyl aromatic hydrocarbon can be at least one of C7, C8, C9, and C10 aromatic hydrocarbons.

[0055] According to the present invention, preferably, the organic synthetic oil is selected from... 59. 60. 62. 66. VP-1 and At least one of LT, more preferably 66. The inventors discovered that, under this preferred embodiment, the extinction properties and high-temperature stability of carbon quantum dots formed by local carbon chain breakage in organic synthetic oils can be improved. The carbon quantum dots and noble metal nanoparticles form a core-shell structure by electrostatic attraction that induces the condensation of chemical bonds, resulting in composite nanoparticles with excellent stability and light absorption, thereby improving the photoelectric conversion performance of the composite nanoparticles.

[0056] According to the present invention, in order to further improve the light absorption performance of the composite nanoparticles, preferably, the noble metal is at least one of gold, silver, platinum, and copper, more preferably gold and / or silver, and even more preferably gold. The inventors have discovered that, under this preferred embodiment, the localized surface plasmon resonance (LSPR) of the noble metal nanoparticles can be improved, thereby enhancing the light absorption and photothermal conversion performance of the composite nanoparticles through their combination with carbon quantum dots.

[0057] According to the present invention, in order to further improve the stability and light absorption of the composite nanoparticles, preferably, the particle size of the noble metal nanoparticles is 5-16 nm, specifically 5 nm, 10 nm, 16 nm, or any value between the two aforementioned values.

[0058] According to the present invention, preferably, the particle size of the composite nanoparticles is 6-17 nm, specifically 6 nm, 10 nm, 15 nm, 17 nm, or any value between the aforementioned two values. The inventors have discovered that, in this preferred embodiment, carbon quantum dots and noble metal nanoparticles form a core-shell structure through electrostatic attraction, leading to the condensation of chemical bonds, thus giving the composite nanoparticles excellent photothermal conversion capabilities.

[0059] In this invention, the particle size of both noble metal nanoparticles and composite nanoparticles can be tested using a nanoparticle size analyzer. The testing method is based on the principle of dynamic light scattering (the particle size is detected by measuring the fluctuation of the scattered light caused by the Brownian motion of the nanoparticles).

[0060] The third aspect of the present invention provides the application of composite nanoparticles obtained by the preparation method described in the first aspect and / or composite nanoparticles described in the second aspect in solar collectors.

[0061] According to a particularly preferred embodiment of the present invention, a method for preparing composite nanoparticles is provided, comprising the following steps: mixing noble metal nanoparticles with organic synthetic oil, dispersing them under ultrasonic frequency of 100-200W for 5-15 min to obtain a dispersion, and reacting the dispersion in a sealed container at a temperature of 140-160℃ for 10-30 h to obtain composite nanoparticles.

[0062] Among them, organic synthetic oil is 66; The precious metal nanoparticles are gold nanoparticles; The weight ratio of the precious metal nanoparticles to the organic synthetic oil is 1×10⁻⁶. -5 -5×10 -5 :1.

[0063] In the above-mentioned preferred embodiment, the prepared composite nanoparticles form a core-shell structure with noble metal nanoparticles as the core and carbon quantum dots as the shell, which effectively improves the stability and light absorption of the composite nanoparticles, thereby improving their photothermal conversion performance.

[0064] The present invention will be described in detail below through embodiments.

[0065] In the following examples and comparative examples, the organic synthetic oils were all purchased from Suzhou Shounuo Thermal Oil Co., Ltd., and the models were as follows: 66. 59. LT and 55; Unless otherwise specified, all other raw materials are commercially available products.

[0066] Example 1

[0067] (1) Add 9 mL of 1 wt% chloroauric acid solution to 70 mL of deionized water. In a magnetic stirring environment at 800 rpm, adjust the temperature to bring it to a boil and continue for 10 min. A large number of floating bubbles continuously appear at the bottom of the reaction vessel, and water vapor droplets are obvious on the top lid. Add 375 μL of oleylamine and continue boiling for 90 min. Then cool to room temperature. During this process, the color of the solution gradually changes from orange-yellow to light yellow, then transitions to pink, and finally becomes deep wine red and no longer changes. Keep the magnetic stirring speed at 1000 rpm at room temperature. Then add 30 mL of cyclohexane to the above mixture and stir for 60 min. Then adjust the pH of the mixture to 9 by adding 1 mol / L NaOH solution and continue stirring for 60 min. After standing, obvious stratification occurs. The supernatant is wine red Au colloid. Transfer the Au colloid to a reagent bottle and store it in a dark environment at room temperature.

[0068] (2) At room temperature, Au colloid, The mixture of 66 was dispersed for 10 minutes under ultrasonic power of 150W to prepare a 30ppm Au / T66 nanofluid. The Au / T66 nanofluid was placed in a cylindrical reagent bottle at room temperature and pressure, with the ratio of the height of the Au / T66 nanofluid to the height of the internal space of the reagent bottle being 0.4:1. The reagent bottle was sealed and the Au / T66 nanofluid was continuously heated at 150℃ for 20 hours using the heating plate of a magnetic stirrer. After cooling to room temperature, the color changed from wine red to dark red, forming Au-CQDs / T66 composite nanoparticles.

[0069] The scanning electron microscope image of the Au-CQDs / T66 composite nanoparticles prepared in Example 1 is shown below. Figure 1 .

[0070] Example 2

[0071] (1) Add 25 mL of 1 wt% chloroauric acid solution to 70 mL of deionized water. Heat to boiling in a magnetic stirring environment at 800 rpm for 10 min. A large number of floating bubbles continuously appear at the bottom of the reaction vessel, and water vapor droplets are obvious on the top lid. Add 750 μL of oleylamine and continue boiling for 60 min. Then cool to room temperature. During this process, the color of the solution gradually changes from orange-yellow to light yellow, then transitions to pink, and finally to deep wine red and no longer changes. Keep the magnetic stirring speed at 1000 rpm at room temperature. Then add 30 mL of cyclohexane to the above mixture and stir for 60 min. Adjust the pH of the mixture to 8 by adding 1 mol / L NaOH solution and continue stirring for 60 min. After standing, obvious stratification occurs. The supernatant is wine red Au colloid. Transfer the Au colloid to a reagent bottle and store it in a dark environment at room temperature.

[0072] (2) At room temperature, Au colloid, The mixture of 66 was dispersed for 5 minutes under ultrasonic power of 200W to prepare a 10ppm Au / T66 nanofluid. The Au / T66 nanofluid was placed in a cylindrical reagent bottle at room temperature and pressure, with the ratio of the height of the Au / T66 nanofluid to the height of the internal space of the reagent bottle being 0.45:1. The reagent bottle was sealed and the Au / T66 nanofluid was continuously heated at 140℃ for 10 hours using the heating plate of a magnetic stirrer. After cooling to room temperature, the color changed from wine red to dark red, forming Au-CQDs / T66 composite nanoparticles.

[0073] Example 3

[0074] (1) Add 12.5 mL of 1 wt% chloroauric acid solution to 70 mL of deionized water. Heat to boiling at 800 rpm with magnetic stirring for 10 min. A large number of floating bubbles continuously appear at the bottom of the reaction vessel, and water vapor droplets are obvious on the top lid. Add 375 μL of oleylamine and continue boiling for 120 min. Then cool to room temperature. During this process, the color of the solution gradually changes from orange-yellow to light yellow, then to pink, and finally to deep wine red and no longer changes. Keep the magnetic stirring speed at 1000 rpm at room temperature. Then add 30 mL of cyclohexane to the above mixture and stir for 60 min. Adjust the pH of the mixture to 10 by adding 1 mol / L NaOH solution and continue stirring for 60 min. After standing, obvious stratification occurs. The supernatant is wine red Au colloid. Transfer the Au colloid to a reagent bottle and store it at room temperature in the dark.

[0075] (2) At room temperature, Au colloid, The mixture of 66 nanoparticles was dispersed for 15 minutes under ultrasonic power of 100W to prepare a 35ppm Au / T66 nanofluid. The Au / T66 nanofluid was placed in a cylindrical reagent bottle at room temperature and pressure, with the ratio of the height of the Au / T66 nanofluid to the height of the internal space of the reagent bottle being 0.33:1. The reagent bottle was sealed and the Au / T66 nanofluid was continuously heated at 160℃ for 30 hours using the heating plate of a magnetic stirrer. After cooling to room temperature, the color changed from wine red to dark red, forming Au-CQDs / T66 composite nanoparticles.

[0076] Example 4

[0077] Composite nanomaterials were prepared according to the method of Example 1, except that in step (2), organic synthetic oil was used. Replace 66 with: 59 and LT, and 59 and The volume ratio of LT is 1:1.

[0078] Example 5

[0079] (1) Preparation of seed solution: Add 7.5 mL of 0.2 mol / L hexadecyltrimethylammonium bromide (CTAB), 2.5 mL of 1.0 mmol / L chloroauric acid aqueous solution and 600 μL of 0.01 mol / L ice-cold NaBH4 solution in sequence, mix thoroughly and stir for 5 minutes. The mixed solution turns light brown and is left to stand for later use. Then prepare growth solution: Add 100 mL of 1.0 mmol / L chloroauric acid aqueous solution, 100 mL of 0.2 mol / L CTAB, 5 mL of 4.0 mmol / L silver nitrate solution and 80 mmol / L ascorbic acid aqueous solution in sequence, mix thoroughly and stir for 5 minutes. Then, take 300 μL of seed solution and add it to the growth solution, seal and let stand overnight. The upper layer of solution turns purple-pink, indicating that gold nanorod mother liquor has been generated. After centrifugation, the solid is ultrasonically dispersed in water to obtain gold nanorod aqueous solution. The aqueous solution of gold nanorods was then poured into an evaporating dish and dried in an oven at 70°C for 8 hours. The resulting dry solid was gold nanorod powder.

[0080] (2) At room temperature, gold nanorod powder and The mixture of 66 was dispersed for 10 minutes under ultrasonic power of 100W to prepare a 30ppm Au / T66 nanofluid. The Au / T66 nanofluid was placed in a cylindrical reagent bottle with the height ratio of the Au / T66 nanofluid to the internal space of the reagent bottle being 0.4:1. The reagent bottle was sealed and the Au / T66 nanofluid was continuously heated at 150℃ for 10 hours using the heating plate of a magnetic stirrer. After cooling to room temperature, the color changed from grayish-green to dark brown, forming Au-CQDs / T66 composite nanoparticles.

[0081] Example 6

[0082] The composite nanomaterials were prepared according to the method of Example 1, except that in step (2), the ratio of the height of the Au / T66 nanofluid in the reagent bottle to the height of the internal space of the reagent bottle was replaced with 0.6:1, and the heating time was replaced with 4h.

[0083] Example 7

[0084] Composite nanomaterials were prepared according to the method of Example 1, except that in step (2), the reagent bottle was kept open during heating.

[0085] Example 8

[0086] Composite nanomaterials were prepared according to the method of Example 1, except that in step (2), the concentration of Au / T66 nanofluid was replaced with 100 ppm.

[0087] Example 9

[0088] (1) Mix 1 mL of 20 g / L silver nitrate aqueous solution with a small amount of ammonia water to form a silver ammonia solution with a concentration of 0.06 M; at the same time, add 0.1 g of glucose, 0.005 g of trisodium citrate dihydrate and 1 g of polyvinylpyrrolidone (PVP) to 50 mL of deionized water to prepare a solution, stir rapidly and heat to 90 °C; then add the above silver ammonia solution to the prepared solution at 90 °C and stir continuously for 1 h until a gray-green color appears, indicating the formation of silver colloid (during the stirring process, an appropriate amount of deionized water needs to be added continuously to avoid the solution from evaporating to dryness).

[0089] (2) Ag colloid and The Ag / T66 nanofluid was prepared by mixing 66 and dispersing it for 10 minutes under ultrasonic power of 150W to obtain 30ppm Ag / T66 nanofluid. The Ag / T66 nanofluid was placed in a cylindrical reagent bottle with the height ratio of the Ag / T66 nanofluid to the internal space of the reagent bottle being 0.4:1. The reagent bottle was sealed and the Ag / T66 nanofluid was continuously heated at 150℃ for 10 hours using the heating plate of a magnetic stirrer. After cooling to room temperature, the color changed from grayish-green to dark brown, forming Ag-CQDs / T66 composite nanoparticles.

[0090] Comparative Example 1

[0091] Composite nanomaterials were prepared according to the method of Example 1, except that in step (2), the organic synthetic oil was replaced with... 55.

[0092] Comparative Example 2

[0093] A certain amount 66 samples were placed in a container and sealed (leaving an oxygen space). Using the heating plate of a magnetic stirrer, the sample was heated at 150°C for 20 hours from bottom to top. The sample was then cooled to room temperature. The color of the sample changed from colorless and transparent to light yellow, indicating that stable and dispersed CQD nanomaterials were generated at this time.

[0094] Test Example 1

[0095] The particle size of the noble metal nanoparticles and composite nanoparticles prepared in Examples 1-9 and Comparative Examples 1-2 was measured using a nanoparticle size analyzer. The results are shown in Table 1.

[0096] Table 1

[0097] serial number Noble metal nanoparticles (nm) Composite nanoparticles (nm) Example 1 5.9 6.5 Example 2 13.4 14.5 Example 3 15.5 16.8 Example 4 5.8 30.6 Example 5 18.5 21.9 Example 6 5.6 6.2 Example 7 5.8 33.5 Example 8 5.8 10.4 Example 9 27.1 29.1 Comparative Example 1 5.8 106.3 Comparative Example 2 0 0

[0098] Test Example 2

[0099] The fluorescence imaging and emission spectra of the Au / T66 nanofluid and Au-CQDs / T66 composite nanoparticles prepared in Example 1 were measured using a conventional camera and a fluorescence spectrophotometer (Hitachi, RF-7000) at an excitation wavelength of 365 nm. The obtained fluorescence imaging and excitation spectra are shown in the figure. Figure 2 .

[0100] Depend on Figure 2 It can be seen that the Au / T66 nanofluid does not contain carbon quantum dots, and the characteristic peak of Au only appears at the 400 nm position, which confirms that the Au nanofluid appears fluorescent purple after UV excitation in the photographic image. When Au-CQDs / T66 composite nanoparticles are formed, the shell structure formed by carbon quantum dots on the outer layer of the gold core blocks the fluorescence effect of Au, making the characteristic peak of Au no longer observable.

[0101] Figure 1 The TEM scan image of the Au-CQDs / T66 composite nanoparticles shows that the particles remain in a dispersed spherical state under the electron microscope, and the outer layer exhibits a mottled and uneven shape, indicating that Au-CQDs / T66 composite nanoparticles were prepared through a heating reaction.

[0102] Test Example 3

[0103] The absorbance at the LSPR peak of 522 nm of the composite nanoparticles prepared in Examples 1-9 and Comparative Examples 1-2 was measured using a UV-Vis-NIR spectrophotometer. The absorbance was measured again after the composite nanoparticles had been left to stand for one month. The absorbance of the composite nanoparticles in their initial state, after one month of standing, and the rate of decrease in absorbance after one month of standing are shown in Table 2. The absorption spectra of the Au-CQDs composite nanoparticles prepared in Example 2 before (i.e., in their initial state) and after one month of standing are shown in Table 2. Figure 3 .

[0104] Table 2

[0105]

[0106]

[0107] As shown in Table 2, compared to Comparative Example 1, the stability and light absorption of the composite nanoparticles prepared in Examples 1-9 were significantly improved. Although the CQDs nanomaterials in Comparative Example 2 exhibited good stability, their light absorption performance was poor due to the absence of noble metal nanoparticles. Among them, such as... Figure 3As shown, the absorbance of the composite nanoparticles in the ultraviolet region hardly decreases, while the absorbance in the visible and near-infrared regions shows a slight decrease. Taking the LSPR peak at 522 nm as an example, the absorbance decreases by only 0.119 after one month. From the perspective of average absorbance, the absorbance of the composite nanoparticles decreases by about 9% after one month of aging, indicating that the Au-CQDs composite nanoparticles synthesized by self-assembly have excellent stability.

[0108] Test Example 4

[0109] The Au colloid with a particle size of 5.9 nm prepared in Example 1 was combined with... Au / T66 nanofluids with concentrations of 10 ppm, 20 ppm, 30 ppm, 40 ppm, and 50 ppm were prepared by mixing 66 nanofluids. The solar energy weighted absorbance fraction (SABS) of these Au / T66 nanofluids was then measured. The Au / T66 nanofluids were then heated at 150°C for 20 hours to obtain Au / T66 composite nanoparticles, and their SABS were measured. The relationship between the SABS and concentration of the Au / T66 nanofluids and Au / T66 composite nanoparticles is shown in the figure below. Figure 4 As shown.

[0110] The Au colloid with a particle size of 15.5 nm prepared in Example 3 was combined with... Au / T66 nanofluids were prepared by mixing 66 nanoparticles to concentrations of 10 ppm, 20 ppm, 30 ppm, 40 ppm, and 50 ppm, respectively. The solar energy weighted absorbance fractions of these Au / T66 nanofluids were then tested, and the results are shown below. Figure 4 The Au / T66 nanofluid was heated at 150℃ for 20 hours to obtain Au / T66 composite nanoparticles, and their solar energy weighted absorbance fraction was measured. The relationship between the solar energy weighted absorbance fraction and concentration of Au / T66 nanofluid and Au / T66 composite nanoparticles is shown in the figure below. Figure 4 As shown.

[0111] from Figure 4It can be seen that when Au nanoparticles and carbon quantum dots are self-assembled to form composite nanoparticles, the solar energy weighted absorption fraction of Au / T66 nanofluid is 7% when the concentration of gold nanoparticles is 10 ppm, while that of Au / T66 composite nanoparticles is 32%, showing a significant increase in light absorption performance. Furthermore, the solar energy weighted absorption fraction of Au / T66 composite nanoparticles increases with the increase in the concentration of added Au nanoparticles. When the concentration of Au nanoparticles is 50 ppm, the solar energy weighted absorption fraction of the synthesized Au / T66 composite nanoparticles reaches 98.4%, which is close to 100%, indicating that self-assembly significantly enhances the light absorption performance of the composite nanoparticles.

[0112] Test Example 5

[0113] Under solar irradiance, the changes over time were observed for Au / T66 nanofluid and Au-CQDs / T66 composite nanoparticles of the same mass in Example 3, and CQDs nanomaterials in Comparative Example 2. Temperature was measured at 66, and the heating-cooling curve during the photothermal conversion process is shown below. Figure 5 As shown.

[0114] from Figure 5 As can be seen, the equilibrium temperature of a single Au / T66 nanofluid is approximately 46℃, while the equilibrium temperature increases by 3.59℃ after obtaining Au-CQDs / T66 composite nanoparticles through self-assembly; at the same time, relative to The temperature was increased by 10.68℃; at the same time, calculations showed that the solar energy utilization efficiency reached about 86.7%, indicating that Au-CQDs composite nanoparticles have excellent photothermal conversion performance.

[0115] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing composite nanoparticles, characterized in that, The method includes: mixing precious metal nanoparticles with organic synthetic oil, dispersing them under ultrasonic frequency of 100-200W for 5-15 minutes to obtain a dispersion, and heating the dispersion in a sealed container at a temperature of 140-160℃ for 10-30 hours to obtain composite nanoparticles. The composite nanoparticles comprise a core and a shell covering the core, thus obtaining composite nanoparticles; the core is a noble metal nanoparticle, and the shell is a carbon quantum dot; the carbon quantum dot is a carbonization product of an organic synthetic oil; The organic synthetic oil is selected from THERMINOL. ® 59. THERMINOL ® 60. THERMINOL ® 62. THERMINOL ® 66. THERMINOL ® VP-1 and THERMINOL ® At least one of LT, wherein the noble metal is at least one of gold, silver, platinum, copper and palladium, the particle size of the noble metal nanoparticles is 5-16 nm, and the particle size of the composite nanoparticles is 6-17 nm.

2. The preparation method according to claim 1, characterized in that, The organic synthetic oil is THERMINOL. ® 66.

3. The preparation method according to claim 1, characterized in that, The precious metal is gold and / or silver.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The weight ratio of the precious metal nanoparticles to the organic synthetic oil is 1×10⁻⁶. -5 -5×10 -5 :

1.

5. The preparation method according to any one of claims 1 to 3, characterized in that, The heating reaction is carried out in a closed container.

6. The preparation method according to claim 5, characterized in that, Before the heating reaction, the volume ratio of the organic synthetic oil to the sealed container is 0.3-0.5:

1.

7. The application of the composite nanoparticles obtained by the preparation method according to any one of claims 1 to 6 in a solar collector.

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