Nanoparticle based on W-VO2-coated AA core-shell structure, preparation method of nanoparticle and thermochromic intelligent window

Abstract

The invention belongs to the technical field of building glass and coating materials thereof, and discloses nanoparticles based on a W-VO2-AA core-shell structure, a preparation method of the nanoparticles and a thermochromism smart window.The method comprises the steps that glacial acetic acid is prepared into a precursor solution, ascorbic acid powder is added and stirred, and W-VO2 nanoparticles are added and subjected to ultrasonic dispersion so that the W-VO2 nanoparticles can be evenly dispersed; heating the obtained turbid liquid to react, cleaning for multiple times after the reaction is completed, centrifuging to obtain a sample, and drying; and finally, uniformly distributing the nanoparticles with the W-VO2-coated AA core-shell structure in PVP (Polyvinyl Pyrrolidone) to form a uniformly dispersed thin film. The solar modulation rate of the W-VO2 / PVP thermochromic intelligent window is greatly improved, meanwhile, the high visible light transmittance is kept, the antagonism between the two optical properties of the visible light transmittance and the solar modulation efficiency is weakened or even broken through, and the thermochromic development of the intelligent window and the radiation refrigeration field is further promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of architectural glass and its coating materials, and specifically relates to a nanoparticle based on a W-VO2@AA core-shell structure and a preparation method thereof, and an application in a thermochromic smart window. Background Art

[0002] Building energy consumption accounts for 45.5% of the country's total energy consumption, while building carbon emissions account for 50.9% of the country's total carbon emissions. About 20% of energy consumption and carbon emissions are generated during the operation of the building, which is used to meet daily energy needs such as indoor lighting, air conditioning, ventilation and heating. Windows are an indispensable part of the building envelope, providing landscape, light transmission and ventilation functions. However, compared with other building components, the extremely poor light and heat regulation performance of glass windows has caused a lot of energy loss. Therefore, windows play an important role in changing the energy demand of buildings. By improving the thermal and optical properties of architectural glass, it is possible to reduce heat loss and reduce heating and cooling energy consumption, thereby contributing to the country's "dual carbon" goals.

[0003] Traditional smart windows mainly include thermochromic, electrochromic, photochromic, etc. However, their large-scale promotion and use are hindered by their requirements for conversion rate, number of cycles, durability, optical performance, environmental protection, and large size and low cost. Therefore, it is an urgent problem to provide a feasible low-cost, multi-band modulation, high-performance adjustable radiative cooling thermochromic smart window development method.

[0004] As a phase change material, vanadium dioxide (VO2) will change into a phase change material when the temperature rises to the phase change temperature (T c ), VO2 will undergo a reversible phase transition from semiconductor phase (M phase) to metal phase (R phase), its carrier concentration will increase suddenly, and its optical properties will also change suddenly. Therefore, VO2 has broad prospects in the application of thermochromic smart windows. In the research of VO2 thermochromic smart windows, how to simultaneously improve the visible light transmittance (T lum ), solar modulation capability (△T sol) and reducing the phase transition temperature have become the main problems hindering its development. Researchers have developed a variety of methods to improve performance, including element doping, core-shell structure and multilayer film structure. Element doping is to dope elements (such as tungsten, hydrogen, zirconium, magnesium, hafnium, tantalum, etc.) during the preparation of vanadium dioxide, occupy or affect the position of V and O, destroy or distort the V-V chain in the monoclinic structure, reduce the orbital splitting gap, enhance the electron concentration of vanadium dioxide, and thus reduce the thermal driving force of electron movement. Since the doping of tungsten will cause the phase transition temperature of vanadium dioxide to drop to 48°C, it is very consistent with the actual needs of life. However, element doping often leads to a decrease in the thermochromic performance of smart windows. Although the phase transition temperature is reduced, its visible light transmittance and solar modulation efficiency are reduced, which makes it unable to meet the needs of practical applications. The visible light transmittance and solar modulation ability of thermochromic smart windows are also very important. Researchers propose to use micro-nanostructure design to solve the problem of performance improvement. According to different structures, it can be divided into hybridization, core-shell structure, multilayer film structure, etc. By preparing core-shell nanoparticles, localized surface plasmon resonance absorption can be used to enhance the optical modulation depth and change the wavelength of the absorption peak, but this often leads to lower T lum Multilayer film structures often add anti-reflection layers based on the principle of refractive index gradient, which can improve T to a certain extent. lum , but it often leads to the problem of insufficient solar energy regulation ability and fails to meet the requirements of effectively regulating room temperature.

[0005] Ascorbic acid (AA), as a biologically active organic substance, has been used by researchers to achieve hydrogen doping of VO2. AA can have a surface coordination effect with VO2. Due to the unique dienol structure of ascorbic acid, it can inject electrons into the VO2 lattice through the formed COV bond, thereby increasing the carrier density inside VO2. In existing studies, researchers often use AA to reduce the phase transition temperature of VO2 and enhance its acid resistance and antioxidant properties. Summary of the invention

[0006] In view of the problem that dimming devices based on vanadium dioxide materials currently used in microelectronics fields such as smart windows and radiative cooling cannot simultaneously improve visible light transmittance and solar energy modulation efficiency, the present invention provides a nanoparticle based on W-VO2@AA core-shell structure and its preparation method and thermochromic smart window, which greatly improves the solar energy modulation rate of W-VO2 / PVP thermochromic smart window while maintaining a high visible light transmittance, weakens or even breaks the antagonism between the two optical properties of visible light transmittance and solar energy modulation efficiency, and further promotes the development of thermochromism in the field of smart windows and radiative cooling.

[0007] According to one aspect of the present invention, a nanoparticle based on a W-VO2@AA core-shell structure is provided, which is prepared by the following preparation method:

[0008] S1. Add ascorbic acid powder to the precursor solution and stir at room temperature to fully dissolve it;

[0009] The precursor solution is prepared by dissolving glacial acetic acid in deionized water and stirring until uniformly mixed; the molar ratio of glacial acetic acid to ascorbic acid in the precursor solution is (0-10.5):1;

[0010] S2, adding W-VO2 nanoparticles to the solution obtained in S1, and performing ultrasonic dispersion to make the W-VO2 nanoparticles dispersed evenly;

[0011] S3. The suspension obtained in S2 is reacted at 80-90°C for 8-10 hours. After the reaction is completed, it is washed several times, and the sample is centrifuged and dried.

[0012] According to another aspect of the present invention, a method for preparing nanoparticles based on a W-VO2@AA core-shell structure is provided, characterized in that it comprises the following steps:

[0013] S1. Dissolve glacial acetic acid in deionized water to prepare a precursor solution, and stir until uniformly mixed;

[0014] S2, adding ascorbic acid powder to the precursor solution obtained in S1, stirring at room temperature to fully dissolve it, adding W-VO2 nanoparticles, and ultrasonically dispersing the W-VO2 nanoparticles to uniformly disperse them;

[0015] S3. The suspension obtained in S2 is reacted at 80-90°C for 8-10 hours. After the reaction is completed, it is washed several times, and the sample is centrifuged and dried.

[0016] In the above-mentioned nanoparticles based on W-VO2@AA core-shell structure and preparation method thereof:

[0017] Preferably, in S1: the molar ratio of glacial acetic acid to ascorbic acid in the precursor solution is (3.5-7):1.

[0018] Preferably, in S2, the molar ratio of W-VO2 nanoparticles to ascorbic acid is 1:(7-10).

[0019] Preferably, in S3: washing with deionized water and anhydrous ethanol for multiple times.

[0020] According to another aspect of the present invention, a thermochromic smart window is provided, which is prepared from the above-mentioned nanoparticles based on the W-VO2@AA core-shell structure.

[0021] Furthermore, the preparation of the thermochromic smart window includes the following steps:

[0022] (1) adding the W-VO2@AA core-shell structure nanoparticles and PVP to anhydrous ethanol and subjecting them to ultrasonic oscillation, then uniformly distributing them by magnetic stirring and then allowing them to stand for use;

[0023] (2) coating the supernatant of the suspension obtained in step (1) on the surface of the pretreated glass substrate to obtain a thermochromic smart window.

[0024] Preferably, the mass ratio of the W-VO2@AA core-shell structured nanoparticles to PVP in step (1) is 1:30.

[0025] Preferably, the pretreatment in step (2) comprises: firstly, ultrasonically cleaning the glass substrate in an acetone solution, then ultrasonically cleaning the glass substrate in anhydrous ethanol, and finally ultrasonically cleaning the glass substrate in deionized water, and drying the glass substrate for later use.

[0026] Preferably, the coating in step (2) comprises: first dropping the supernatant of the suspension obtained in step (1) onto the surface of the pretreated glass substrate, then spin coating using a spin coater, first rotating at a low speed, then rotating at a high speed, and finally drying for standby use.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a composite structure of W-VO2@AA / PVP. On the one hand, an organic core-shell structure is formed on the surface of W-VO2. Since its refractive index is lower than that of W-VO2, it can be used as an anti-reflection layer. Due to the unique dienol structure of ascorbic acid, electrons can be injected into the W-VO2 lattice through the formed COV bonds, thereby increasing the carrier density inside W-VO2, so that the overall structure has a greater shielding effect on near-infrared light. The introduction of PVP material can not only be used as a dispersant but also as a transparent material to increase the transmittance of visible light. The refractive index of PVP is lower than that of ascorbic acid, and it can form a three-layer film with ascorbic acid and tungsten-doped vanadium dioxide. The three materials form a three-layer anti-reflection structure with a gradient increasing refractive index, which can improve the transmittance of the entire structure to visible light.

[0029] Based on this, the present invention prepares a W-VO2@AA / PVP thermochromic smart window with all-round high performance that is more suitable for practical applications. While greatly improving the solar modulation rate of the W-VO2 / PVP thermochromic smart window, it maintains a high visible light transmittance. The overall performance of W-VO2@AA / PVP is improved by 80% compared with W-VO2 / PVP, weakening or even breaking the antagonism between the two optical properties of visible light transmittance and solar modulation efficiency. It further promotes the development of thermochromism in the field of smart windows and radiative cooling. With the development of microelectronic devices towards miniaturization and reliability, the W-VO2@AA core-shell structure has become an important means to improve the performance of microelectronic devices, further providing preparation experience for experimental results and promoting the development of microelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart for preparing the thermochromic smart window samples of Examples 1-6 of the present invention.

[0031] Figure 2 Visible-mid-infrared infrared spectra of the thermochromic smart window samples prepared in Examples 1-6 of the present invention; (a) shows the transmittance of different samples in the 380-2500nm band; (b) based on the data obtained by the spectrophotometer, the thermochromic properties of different samples are calculated and statistically analyzed.

[0032] Figure 3 Schematic diagram of the control principle of the thermochromic smart window samples prepared in Examples 1-6 of the present invention.

[0033] Figure 4 This is a scanning electron microscope image of the thermochromic smart window sample prepared in Example 1 of the present invention.

[0034] Figure 5 This is a physical picture of the thermochromic smart window sample prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0036] like Figure 1 As shown, the present invention provides a nanoparticle based on W-VO2@AA core-shell structure and a preparation method thereof, successfully designs and prepares the W-VO2@AA core-shell structure model on transparent glass through the refractive index gradient and LSPR principle, optimizes the drug mass ratio and method, sets stirring parameters, drying parameters, and spin coating parameters to effectively prepare a radiation cooling type thermochromic smart window, provides a higher visible light transmittance, and improves its ability to modulate thermal radiation and near-infrared regulation.

[0037] Example 1

[0038] The specific steps of its preparation are as follows:

[0039] Step 1: Preparation before synthesis

[0040] A1: Cleaning experimental equipment and substrates

[0041] The beaker, medicine spoon, glass substrate and magnet were ultrasonically cleaned to ensure the cleanliness of their surfaces. The cleaning process of the substrate was as follows: an appropriate amount of anhydrous ethanol was poured into the beaker and ultrasonically cleaned for 15 minutes to ensure that the impurities and dust in the beaker were removed; the substrate was placed in a clean beaker and ultrasonically cleaned with acetone and anhydrous ethanol for 15 minutes respectively; finally, the cleaned substrate was taken out, transferred to a tray and placed in an oven for drying for 15 minutes.

[0042] A2: Weighing ascorbic acid, PVP, and W-VO2 nanoparticles

[0043] Use a high-precision electronic scale to weigh 4.403 g of ascorbic acid powder; 300 mg of W-VO2 nanoparticles; and 600 mg of PVP powder, and use a measuring cylinder to measure 10 ml of glacial acetic acid and 25 ml of deionized water, respectively.

[0044] Step 2: Preparation of W-VO2@AA core-shell structure:

[0045] A1: Preparation of precursor solution

[0046] 10 ml of glacial acetic acid was dissolved in 25 ml of deionized water and stirred at 30° C. for 30 minutes to prepare a precursor solution.

[0047] A2: Preparation of W-VO2@AA core-shell structure

[0048] Take 4.403g of ascorbic acid powder and add them to the precursor solution, stir at 25-40℃ to fully dissolve it, add appropriate amount of W-VO2, ultrasonically disperse it at 25-40℃ to make the nanoparticles evenly dispersed, put the prepared suspension into a constant temperature box and keep it at 60-90℃ for 6-10h. After the reaction is completed, it is washed with deionized water and anhydrous ethanol several times and centrifuged to obtain the sample. The obtained sample is placed in a constant temperature box and kept at 60-70℃ for 8-12h and dried to obtain a black powder.

[0049] Step 3: Preparation of W-VO2(NP)&PVP solution:

[0050] A1: Take 3 ml of anhydrous ethanol:

[0051] 600 mg PVP was added to 3 ml anhydrous ethanol and ultrasonically dispersed at 40°C for 30 min to form a dispersion.

[0052] A2: Add W-VO2@AA powder:

[0053] W-VO2@AA was added to the dispersion and ultrasonic oscillation was continued for 1 h. Finally, it was stirred by a magnetic stirrer for 4 h and then allowed to stand for 24 h for use.

[0054] Step 3: Preparation of composite layer:

[0055] A1: Spin coating composite layer

[0056] Use a pipette to measure 140 μL of W-VO2@AA(NP)&PVP solution and drop it on a transparent glass substrate. The spin coating parameters are adjusted to a low speed of 800 r / min for 10 s and a high speed of 2000 r / min for 20 s.

[0057] A2: Heating the composite layer

[0058] After the composite layer was spin-coated, it was heated at 60°C for 5 minutes to remove the surface haze and dry it. The resulting sample was numbered S10.

[0059] Example 2

[0060] A composite layer was prepared on a transparent glass substrate according to the specific steps of Example 1, the only difference being that 0 ml of glacial acetic acid was used in A2 in step 1 and A1 in step 2, and the obtained sample was numbered S0.

[0061] Example 3

[0062] A composite layer was prepared on a transparent glass substrate according to the specific steps of Example 1, the only difference being that 2.5 ml of glacial acetic acid was used in A2 in step 1 and A1 in step 2, and the obtained sample was numbered S2.5.

[0063] Example 4

[0064] A composite layer was prepared on a transparent glass substrate according to the specific steps of Example 1, the only difference being that 5 ml of glacial acetic acid was used in A2 in step 1 and A1 in step 2, and the obtained sample was numbered S5.

[0065] Example 5

[0066] A composite layer was prepared on a transparent glass substrate according to the specific steps of Example 1, the only difference being that 15 ml of glacial acetic acid was used in A2 in step 1 and A1 in step 2, and the obtained sample was numbered S15.

[0067] Example 6

[0068] A composite layer was prepared on a transparent glass substrate according to the specific steps of Example 1, the only difference being that 20 ml of glacial acetic acid was used in A2 in step 1 and A1 in step 2, and the obtained sample was numbered S20.

[0069] The transmittance curves of the thermochromic smart window samples (S0, S2.5, S5, S10, S15, S20) prepared in Examples 1-6 of the present invention and the thermochromic smart window sample (W) prepared by W-VO2 without any treatment were tested at 25°C and 80°C using an ultraviolet-near infrared-visible spectrophotometer. Figure 2 Visible-mid-infrared infrared spectra of different samples; (a) shows the transmittance of different samples in the 380-2500nm band; (b) based on the data obtained by the spectrophotometer, the thermochromic properties of different samples are calculated and statistically analyzed.

[0070]

[0072] ΔT sol =T sol，c -T sol，h (3)

[0074] ΔT NIR =T NIR，c -T NIR，h (4)

[0076] ΔT l u m =ΔT sol -ΔT NIR (5)

[0077] In formulas (1)-(5), T(λ) is the spectral transmittance at wavelength λ, is the relationship between the light sensitivity of the human eye and the wavelength. is the solar radiation energy distribution spectrum when the angle between the sun and the horizon is 37°, T lum为 Visible light transmittance of materials at low temperature (T lum ,L) and visible light transmittance at high temperature (T lum ,H) average value, T sol ,L,T sol ,H are the solar spectrum transmittance at low temperature (25℃) and high temperature (80℃), ΔT sol is the solar modulation capability, ΔT NIR is the near-infrared modulation capability, ΔT lum Represents visible light modulation capability.

[0078] like Figure 2 As shown, with the increase of the molar ratio of glacial acetic acid to AA, when the molar ratio is less than or equal to 3.5:1, with the increase of the molar ratio, the visible light transmittance and solar modulation rate of the prepared film both show a more obvious increase, which is due to the increase of AA shell thickness and electron injection amount.

[0079] When the molar ratio is greater than 3.5:1 and less than or equal to 7:1, the visible light transmittance of the composite film will decrease slightly, and the solar modulation rate will increase significantly. At this time, as the amount of electron injection increases, the LSPR absorption peak will have a significant blue shift, and the influence of electron concentration becomes the main factor, resulting in a decrease in visible light transmittance.

[0080] When the molar ratio is greater than 7:1 and less than or equal to 10.5:1, excess glacial acetic acid will inhibit the reaction, causing the thermochromic performance to gradually decrease but still higher than the control group.

[0081] When the molar ratio is greater than 10.5:1 and less than 14:1, the thermochromic properties tend to be consistent with the control group.

[0082] Figure 3 The reaction mechanism of the present invention is described, AA and W-VO2 will have a surface coordination effect, AA is adsorbed on the surface of W-VO2 through COV bonds to form a core-shell structure, and the electrons in AA are injected into the W-VO lattice through COV bonds. Glacial acetic acid can simultaneously regulate the thickness of the shell and the concentration of injected electrons.

[0083] Figure 4 The picture of S10 sample was taken by field emission scanning electron microscope (SEM). Figure 4 The W-VO2 core and the AA shell can be clearly observed. AA has a darker color due to its larger atomic number.

[0084] Figure 5 It is a W-VO2@AA / PVP smart window model of S10 sample prepared by spin coating on transparent glass substrate.

[0085] It can be seen that the nanoparticles based on the W-VO2@AA core-shell structure and the preparation method thereof provided by the present invention can be effectively applied to radiation cooling smart windows, and their spectral characteristics are characterized, and their ability to modulate thermal radiation and near-infrared regulation is improved, which meets the performance requirements in the field of smart windows and radiation cooling. The process is simple and the preparation cost is reduced, thus promoting the development of microelectronic devices.

[0086] The technical solutions disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the contents of this article and appropriately changing the conditions, routes and other links. Although the methods and preparation techniques of the present invention have been described through preferred embodiments, relevant technicians can obviously modify or re-combine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims

1. A method for preparing nanoparticles based on W-VO2@AA core-shell structure, characterized in that: The steps include: S1. Add ascorbic acid powder to the precursor solution and stir at room temperature to fully dissolve it; The precursor solution is prepared by dissolving glacial acetic acid in deionized water and stirring until uniformly mixed; the molar ratio of glacial acetic acid to ascorbic acid in the precursor solution is (0-10.5):1; S2, adding W-VO2 nanoparticles to the solution obtained in S1, and performing ultrasonic dispersion to make the W-VO2 nanoparticles dispersed evenly; S3. The suspension obtained in S2 is reacted at 80-90°C for 8-10 hours. After the reaction is completed, it is washed several times, and the sample is centrifuged and dried.

2. The method for preparing nanoparticles based on W-VO2@AA core-shell structure according to claim 1, characterized in that: In S1: the molar ratio of glacial acetic acid to ascorbic acid in the precursor solution is (3.5-7):

1.

3. The method for preparing nanoparticles based on W-VO2@AA core-shell structure according to claim 1, characterized in that: In S2: the molar ratio of W-VO2 nanoparticles to ascorbic acid is 1:(7-10).

4. The method for preparing nanoparticles based on W-VO2@AA core-shell structure according to claim 1, characterized in that: In S3: washing with deionized water and anhydrous ethanol for multiple times.

5. A nanoparticle based on W-VO2@AA core-shell structure, characterized in that: Obtained by the preparation method according to any one of claims 1 to 4.

6. A thermochromic smart window, characterized in that: The nanoparticles are prepared using the W-VO2@AA core-shell structure nanoparticles as described in claim 5.

7. The thermochromic smart window according to claim 6, characterized in that: The preparation method thereof comprises the following steps: (1) adding the W-VO2@AA core-shell structure nanoparticles and PVP to anhydrous ethanol and subjecting them to ultrasonic oscillation, then uniformly distributing them by magnetic stirring and then allowing them to stand for use; (2) coating the supernatant of the suspension obtained in step (1) on the surface of the pretreated glass substrate to obtain a thermochromic smart window.

8. The thermochromic smart window according to claim 7, characterized in that: The mass ratio of the W-VO2@AA core-shell structured nanoparticles to PVP in step (1) is 1:

30.

9. The thermochromic smart window according to claim 7, characterized in that: The pretreatment in step (2) includes: firstly, ultrasonically cleaning the glass substrate in an acetone solution, then ultrasonically cleaning the glass substrate in anhydrous ethanol, and finally ultrasonically cleaning the glass substrate in deionized water, and then drying the glass substrate for later use.

10. The thermochromic smart window according to claim 7, characterized in that: The coating in step (2) includes: firstly dropping the supernatant of the suspension obtained in step (1) onto the surface of the pretreated glass substrate, then using a spin coater for spin coating, first rotating at a low speed, then rotating at a high speed, and finally drying for use.

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