Preparation method of high-brightness non-flickering plasmon-exciton hybrid nano superstructure
By fabricating plasmon-exciton hybrid nanostructures and utilizing the local field of gold nanoparticles to modulate the exciton decay of quantum dots, the problems of fluorescence scintillation and low quantum yield of quantum dots were solved, achieving high-brightness, flicker-free photon emission, which is suitable for applications with high photon thresholds.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-25
- Publication Date
- 2026-03-24
AI Technical Summary
Quantum dots exhibit fluorescence scintillation behavior and low luminescence efficiency at the single-particle scale, mainly due to the nonradiative Auger recombination process during exciton decay, which limits their application in high photon threshold applications such as quantum dot solar cells and lasers.
By modulating the exciton decay behavior of quantum dots in a localized plasmonic field around gold nanoparticles, a plasmonic-exciton hybrid nanostructure was prepared. The localized field was provided by gold nanoparticles, and fluorescent quantum dots that resonate with the plasmonic absorption peak were selected. The coupling of plasmons and excitons was achieved by using surface-functionalizable and thickness-tunable silica (SiO2) as a spacer layer, thus preparing a single-particle dispersed Au@SiO2-QD nanostructure.
It greatly suppresses the flickering characteristics of quantum dot emission, improves the emission brightness and fluorescence intensity of single quantum dots, and realizes high-brightness flicker-free photon emission behavior, which is suitable for lasers with high emission thresholds and quantum dot electroluminescent diodes (LEDs).
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Figure CN118085867B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor nanomaterials and devices, specifically relating to a method for preparing a high-brightness, flicker-free plasmon-exciton hybrid nanostructure. Background Technology
[0002] Quantum dots possess unique optical properties, including tunable emission wavelengths, high quantum efficiency, and high stability, making them widely used in research fields such as photovoltaics, LED displays, and bioimaging. However, in in-depth, single-particle studies, quantum dots exhibit alternating bright and dark photon intensity states, which significantly limits their application in displays. Furthermore, due to the non-radiative Auger process in the exciton decay of quantum dots, excitons interact with each other, annihilating into a single exciton for either luminescence or no emission. This reduces the fluorescence efficiency of quantum dots, hindering multiphoton generation and limiting their application in high photon threshold applications, such as quantum dot solar cells and lasers.
[0003] To suppress the nonradiative Auger recombination process in quantum dots, two main approaches have been developed to overcome these drawbacks. One approach involves the chemical synthesis of quantum dots, growing one or more shell materials with wide band gaps around the quantum dot core to form a core-shell structure. This passivates the quantum dot surface and slows down the Auger recombination rate, thereby suppressing fluorescence scintillation and increasing emission intensity. This approach requires advanced quantum dot synthesis technology, has a relatively demanding synthesis route, and generates some toxic byproducts during quantum dot preparation, causing environmental pollution and hindering sustainable development. The other approach utilizes plasmonic nanostructures coupled with quantum dots to suppress fluorescence scintillation and nonradiative Auger recombination. The localized field of the plasmonic nanostructure increases the exciton radiative recombination rate of the quantum dot, which is comparable to the nonradiative Auger recombination rate, thus competing with it to suppress fluorescence scintillation characteristics and improve the multiphoton emission behavior and fluorescence emission intensity of the quantum dot.
[0004] CN 114621760 A discloses a perovskite quantum dot with synergistic surface plasmon resonance enhancement and its preparation method. The method includes: preparing a gold seed solution by taking a hexadecyltrimethylammonium bromide solution, a chloroauric acid solution, and a sodium borohydride solution in an ice-water mixture; further adding a mixed solution of hexadecyltrimethylammonium bromide solution, chloroauric acid solution, silver nitrate solution, hydrochloric acid, and ascorbic acid solution to obtain a colloidal solution of gold nanorods; further adding a hexadecyltrimethylammonium bromide solution, tetraethyl orthosilicate, sodium hydroxide solution, and isopropanol solution to obtain an aqueous solution of Au@SiO2 core-shell heterogeneous nanomaterials; further adding a 3-aminopropyltriethoxysilane solution, and dispersing the precipitate in a tetrahydrofuran solution to obtain a tetrahydrofuran solution of amino-modified Au@SiO2 core-shell heterogeneous nanomaterials; and further mixing with the perovskite quantum dot solution to prepare perovskite quantum dots with synergistic surface plasmon resonance enhancement. The preparation method is cumbersome, the prepared nanocomposite structure is non-uniform, the perovskite quantum dots are randomly adsorbed, and the fluorescence enhancement of the perovskite quantum dots is uncontrollable.
[0005] Semiconductor quantum dots possess unique luminescent properties, exhibiting a broad absorption spectrum and a narrow emission spectrum, making them widely applicable in optoelectronics and bioimaging. However, at the single-particle scale, semiconductor quantum dots exhibit fluorescence flickering behavior and low luminescence efficiency, primarily limited by the nonradiative Auger recombination process during exciton decay. This invention proposes a method for preparing nanostructures that suppresses fluorescence flickering while enhancing the fluorescence intensity of quantum dots. This method leverages the localized plasmon field surrounding gold nanoparticles to modulate the exciton decay characteristics of quantum dots, thereby suppressing the Auger recombination process and enabling the quantum dots to exhibit high-brightness, flicker-free photon emission behavior.
[0006] Based on the characteristic that the coupling effect of plasmon fields and excitons alters the optical behavior of quantum dots, this invention provides a hybrid nanostructure of plasmons and excitons. In this superstructure, the fluorescence intensity of quantum dots is enhanced, exhibiting photon emission characteristics without flickering. This hybrid nanostructure of the present invention can achieve complementary advantages in optical performance between plasmons and excitons through their interaction. The preparation method of this invention is novel, low-cost, and simple. In this nanostructure, plasmons and excitons are innovatively combined in one structure, which greatly suppresses the luminescence flickering characteristics of quantum dots and improves the emission brightness of single quantum dots. Summary of the Invention
[0007] To address the shortcomings of fluorescence flickering and low quantum yield in single-particle quantum dots, this invention provides a method for preparing nanostructures that enhance quantum dot emission intensity and suppress fluorescence flickering based on the characteristics of plasmon localized fields. This method utilizes the localized plasmon field surrounding gold nanoparticles to modulate the exciton decay behavior of quantum dots, thereby suppressing Auger recombination and enabling the quantum dots to exhibit high-brightness, flicker-free photon emission. In this invention, plasmons and excitons are constructed within the same nanocomposite structure. Gold (Au) nanoparticles provide the localized field, and fluorescent quantum dots (QDs) ZnCdSeS / ZnS, which resonate with the plasmon absorption peak, provide the excitons. A surface-functionalizable and thickness-tunable silica (SiO2) serves as a spacer layer. Single-particle dispersed Au@SiO2-QD nanostructures are prepared using a chemical synthesis method. This invention offers a novel preparation method with low manufacturing cost and a simple process. It fully utilizes the modulation effect of the localized field of gold nanoparticles on the excitons of quantum dots, thereby effectively improving the quantum efficiency of quantum dots and exhibiting flicker-free characteristics.
[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0009] A method for preparing a high-brightness, flicker-free plasmon-exciton hybrid nanostructure includes the following steps:
[0010] (1) Gold nanoparticle solution was prepared by reducing chloroauric acid with sodium citrate. Gold nanoparticles were prepared at 100°C and surfactant PVP was added. The nanoparticles were then centrifuged and dispersed in an ethanol solution.
[0011] (2) A SiO2 shell was grown using a reverse microemulsion method. Water, ammonia and tetraethyl orthosilicate (TEOS) were added to the gold nanoparticle solution obtained in step (1). The mixture was stirred at room temperature for 4 hours to grow SiO2 on the surface of the gold nanoparticles. An ethanol solution of Au@SiO2 nanoparticles was obtained. The nanoparticles were centrifuged and then dispersed in the ethanol solution. By controlling the amount of TEOS added, SiO2 shells of different thicknesses were precisely grown. The shell thickness could be adjusted from 3 nm to 20 nm. The SiO2 shell was optimized to achieve the maximum coupling strength between the gold nanoparticles and quantum dots, resulting in a high-brightness, flicker-free hybrid nanostructure.
[0012] (3) The surface of Au@SiO2 nanoparticles obtained in step (2) is modified by silanization. 3-aminopropyltrimethoxysilane (APTMS) is added to the Au@SiO2 nanoparticle solution obtained in step (2) and the reaction is carried out by continuous stirring for a period of time to obtain surface-functionalized Au@SiO2 nanoparticles. After being centrifuged and washed twice with anhydrous ethanol, they are dispersed in anhydrous ethanol. The SiO2 shell surface is modified by adding APTMS to facilitate the localization and adsorption of quantum dots by chemical bonding.
[0013] (4) Select an ethanol solution of ZnCdSeS / ZnS with a fluorescence peak at 532nm and mix it with the product of step (3). Stir at low speed and room temperature for a period of time, centrifuge to remove unadsorbed quantum dots, take the precipitate and disperse it again in ethanol to obtain the plasmon-exciton nanohybrid superstructure Au@SiO2-QD.
[0014] Furthermore, the typical preparation method of the gold nanoparticle solution in step (1) is as follows: Prepare 30 mL of 0.77 mM tetrachloroauric acid aqueous solution, boil it, add 5 mL of 10 mM sodium citrate tetrahydrate aqueous solution, react for 15 min, add 0.25 g PVP and stir for 12 hours.
[0015] Furthermore, the plasmon resonance peak of the gold nanoparticles in step (1) is at 530 nm.
[0016] Further, in step (2), 7 mL of gold nanoparticle solution was taken, centrifuged twice, and the precipitate was taken and dispersed in 10 mL of anhydrous ethanol. Then, 5 mL of water, 5 mL of ammonia water, and 10 μL of 10% tetraethyl orthosilicate (TEOS) were added. The mixture was stirred for 4 h, and finally, the precipitate was centrifuged and dispersed in 2 mL of anhydrous ethanol to obtain Au@SiO2 nanoparticle solution.
[0017] Furthermore, in step (3), 0.1 mL of APTMS is added to 2 mL of Au@SiO2 nanoparticle solution.
[0018] Furthermore, in step (3), the stirring reaction is carried out at a temperature of 60°C for 24 hours.
[0019] Furthermore, the material to be prepared is Au nanoparticles, a SiO2 shell, and semiconductor quantum dots with oleic acid and oleylamine as surface ligands.
[0020] Furthermore, in step (4), the fluorescence peak position of the quantum dot selected is matched with the plasmon resonance peak position of the Au nanoparticle, which is required to be around 530 nm. This is to increase the emission rate of the quantum dot by achieving a localized plasmon field near 530 nm, thereby enhancing the emission intensity.
[0021] Furthermore, in step (4), the surface ligands of the quantum dots must contain oleic acid molecules, which can achieve stable chemical bonding through the condensation reaction between the carboxyl groups on the surface of the quantum dots and the amino groups on the silanized SiO2 shell.
[0022] Furthermore, in step (4), the concentration of quantum dots needs to be diluted to less than or equal to 10. -8 M, to achieve single-particle adsorption.
[0023] Furthermore, in step (4), the stirring speed at low speed and room temperature is 500 rpm, and the time is 2 hours.
[0024] Furthermore, in step (4), the prepared mixed solution needs to be cleaned, stirred at low speed and room temperature for 2 hours, centrifuged to remove unadsorbed quantum dots, and the precipitate is then dispersed again in ethanol.
[0025] Based on the characteristic that the coupling effect of plasmon fields and excitons alters the optical behavior of quantum dots, this invention provides a hybrid nanostructure of plasmons and excitons. In this superstructure, the fluorescence intensity of quantum dots is enhanced, exhibiting photon emission characteristics without flickering. This hybrid nanostructure of the present invention can achieve complementary advantages in optical performance between plasmons and excitons through their interaction.
[0026] Compared with the prior art, the advantages of the present invention are:
[0027] 1. The preparation method is simple, easy to operate, safe and non-toxic, and can be easily mass-produced, which is conducive to industrialization.
[0028] 2. The fusion of plasmonic nanostructures and semiconductor quantum dots in a hybrid superstructure is beneficial for applications in quantum dot LEDs and solar cells.
[0029] 3. The preparation method of this invention is novel, with low manufacturing cost and simple process. In this nanostructure, plasmons and excitons are innovatively combined in one structure, which greatly suppresses the luminescence flickering characteristics of quantum dots and improves the emission brightness of single quantum dots. It is expected to be applied in lasers and quantum dot electroluminescent diodes (LEDs) that require high emission thresholds. Attached Figure Description
[0030] A more complete understanding of the invention will become clear and easier to grasp, and its advantages and features will become more readily apparent, by referring to the accompanying drawings and the following detailed description, in which:
[0031] Figure 1 These are transmission electron microscope (TEM) images of Au nanoparticles, quantum dots, and Au@SiO2-QD. (a) TEM image of Au nanoparticles, with an average particle size of approximately 20 nm. (b) TEM image of ZnCdSeS / ZnS quantum dots, with an average particle size of approximately 7 nm. (c) TEM image of Au@SiO2-QD hybrid nanostructures.
[0032] Figure 2 These are transmission electron microscope images of Au@SiO2 prepared in Examples 2-6 and Au@SiO2-QD fluorescence spectra with different shell thicknesses. (ae) shows transmission electron microscope images of Au@SiO2 nanoparticles with different shell thicknesses, and (f) shows Au@SiO2-QD fluorescence spectra with different shell thicknesses.
[0033] Figure 3 These are time-varying trajectory diagrams of the fluorescence intensity of a single quantum dot and a single hybrid nanostructure at the single-particle scale. (a) Time-varying trajectory diagram of the fluorescence intensity of a single quantum dot in free space, and (b) Time-varying trajectory diagram of the fluorescence intensity of a single Au@SiO2-QD hybrid nanostructure. The excitation power is 50 nW. Detailed Implementation
[0034] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.
[0035] Example 1
[0036] Preparation of gold nanoparticle solutions
[0037] Prepare 30 mL of 0.77 mM tetrachloroauric acid aqueous solution, boil it, and then add 5 mL of 10 mM sodium citrate tetrahydrate aqueous solution. After reacting for 15 min, add 0.25 g of PVP and stir for 12 hours. Divide into five equal portions and store them for later use in preparing SiO2 shell structures of different thicknesses by adding different doses of tetraethyl orthosilicate (TEOS).
[0038] Example 2
[0039] The preparation method of the plasmon-exciton nanohybrid superstructure Au@SiO2-QD in this embodiment is as follows:
[0040] (1) Take a portion of the gold nanoparticle solution prepared in Example 1, centrifuge twice, take the precipitate and disperse it in 10 mL of anhydrous ethanol, then add 5 mL of water, 5 mL of ammonia water and 10 μL of 10% tetraethyl orthosilicate (TEOS), stir at room temperature for 4 h, and finally centrifuge to take the precipitate and disperse it in 2 mL of anhydrous ethanol to obtain Au@SiO2 nanoparticle ethanol solution.
[0041] (2) Add 200 μL of ultrapure water to the 2 mL Au@SiO2 nanoparticle ethanol solution prepared in step (1), then add 0.1 mL of APTMS to modify the silica surface. Heat the mixture to 60 °C and stir continuously for 24 hours. Then, wash the modified Au@SiO2 particles twice with anhydrous ethanol by centrifugation and finally disperse them in 1 mL of anhydrous ethanol.
[0042] (3) Take 200 μL of a concentration of 10 -8An ethanol solution of M ZnCdSeS / ZnS (quantum dots containing oleic acid and oleylamine ligands were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., and the fluorescence peak position needs to be around 530nm) was mixed with the product of step (2), stirred at low speed (500rpm) at room temperature for 2 hours, centrifuged to remove unadsorbed quantum dots, and the precipitate was redispersed in ethanol to obtain a plasmon-exciton nanohybrid superstructure Au@SiO2-QD-8, in which the SiO2 thickness is 8nm.
[0043] Example 3
[0044] The only difference from Example 2 is the addition of 2 μL of 10% (v / v) tetraethyl orthosilicate (TEOS). The other preparation methods are the same as in Example 2, resulting in a plasmonic-exciton nanohybrid superstructure Au@SiO2-QD-3, wherein the SiO2 thickness is 3 nm.
[0045] Example 4
[0046] The only difference from Example 2 is the addition of 5 μL of 10% (v / v) tetraethyl orthosilicate (TEOS). The other preparation methods are the same as in Example 2, resulting in a plasmon-exciton nanohybrid superstructure Au@SiO2-QD-6, in which the SiO2 thickness is 6 nm.
[0047] Example 5
[0048] The only difference from Example 2 is the addition of 15 μL of 10% (v / v) tetraethyl orthosilicate (TEOS). The other preparation methods are the same as in Example 2, resulting in a plasmonic-exciton nanohybrid superstructure Au@SiO2-QD-10, wherein the SiO2 thickness is 10 nm.
[0049] Example 6
[0050] The only difference from Example 2 is the addition of 20 μL of 10% (v / v) tetraethyl orthosilicate (TEOS). The other preparation methods are the same as in Example 2, resulting in a plasmonic-exciton nanohybrid superstructure Au@SiO2-QD-17, in which the SiO2 thickness is 17 nm.
[0051] TEOS with a volume fraction of 10% was prepared in the form of 2 μL, 5 μL, 15 μL, and 20 μL, respectively. Other experiments were conducted according to Example 2 to prepare Au@SiO2-QDs with different SiO2 thicknesses. Figure 2As shown, (ae) is a transmission electron microscope image of Au@SiO2 nanoparticles with different shell thicknesses, and (f) is the fluorescence spectrum of Au@SiO2-QD with different shell thicknesses. When the SiO2 thickness is 3 nm, fluorescence quenching occurs due to increased nonradiative energy transfer between plasmons and excitons. As the SiO2 shell thickness increases to 6 nm, 8 nm, and 10 nm, the fluorescence intensity is enhanced, reaching its maximum at 8 nm. If the SiO2 thickness is further increased to 17 nm, the local field of the metal nanoparticles cannot affect the excitons of the quantum dots, and the photons of the quantum dots may be absorbed by the metal nanoparticles, thus causing fluorescence quenching. Figure 2 (f). Therefore, the optimal amount of TEOS used in this invention is 10 μL.
[0052] Figure 3 Figure a shows the evolution of fluorescence intensity of quantum dots over time in free space, i.e., without the influence of plasmon local fields. It clearly shows the fluorescence scintillation behavior of the semiconductor quantum dots as the photon intensity transitions between bright and dark states. When the excitation power is 50 nW, the photon intensity is 150 counts. When we combine quantum dots with gold nanoparticles to form a nanohybrid superstructure, the fluorescence scintillation behavior of the quantum dots is greatly suppressed, such as... Figure 3 As shown in b, we also found that the fluorescence intensity of the quantum dots was 900 counts, which is nearly 6 times stronger than that of the quantum dots. Figure 3 This indicates that in the nano-hybrid structure prepared by the present invention, the fluorescence scintillation behavior of quantum dots is suppressed, while the emission brightness of photons is improved.
[0053] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a high-brightness, flicker-free plasmon-exciton hybrid nanostructure, characterized in that, Includes the following steps: (1) Gold nanoparticles were prepared at 100°C by reducing chloroauric acid with sodium citrate, and the surfactant PVP was added and centrifuged and dispersed in an ethanol solution to obtain a gold nanoparticle solution. (2) Add water, ammonia and tetraethyl orthosilicate (TEOS) to the gold nanoparticle solution obtained in step (1), stir at room temperature for a period of time to grow SiO2 on the surface of gold nanoparticles, and obtain an ethanol solution of Au@SiO2 nanoparticles. Centrifuge and wash the nanoparticles and then disperse them in the ethanol solution. (3) Silanization modification of the surface of Au@SiO2 nanoparticles obtained in step (2): 3-aminopropyltrimethoxysilane APTMS is added to the Au@SiO2 nanoparticle solution obtained in step (2) and stirred for a period of time to obtain surface-functionalized Au@SiO2 nanoparticles. After being centrifuged and washed twice with anhydrous ethanol, they are dispersed in anhydrous ethanol. (4) Select an ethanol solution of quantum dots with a fluorescence peak at 532 nm and mix it with the product of step (3). Stir at low speed and room temperature for a period of time, centrifuge to remove unadsorbed quantum dots, take the precipitate and disperse it again in ethanol to obtain the plasmon-exciton nanohybrid superstructure Au@SiO2-QD. The fluorescence scintillation behavior of quantum dots is suppressed, and the emission brightness of photons is improved. The preparation method of the gold nanoparticle solution in step (1) is as follows: Prepare 30 mL of 0.77 mM tetrachloroauric acid aqueous solution, boil it, add 5 mL of 10 mM sodium citrate tetrahydrate aqueous solution, react for 15 min, add 0.25 g PVP and stir for 12 hours. In step (1), the plasmon resonance peak of the gold nanoparticles is at 530 nm; In step (2), take 7 ml of the gold nanoparticle solution prepared in step (1), centrifuge twice, take the precipitate and disperse it in 10 mL of anhydrous ethanol, then add 5 mL of water, 5 mL of ammonia water and 10 μL of 10% tetraethyl orthosilicate (TEOS), stir the reaction at room temperature for 4 h, and finally centrifuge to take the precipitate and disperse it in 2 mL of anhydrous ethanol to obtain Au@SiO2 nanoparticle solution. In step (3), 0.1 mL of APTMS is added to the 2 mL Au@SiO2 nanoparticle solution obtained in step (2), and the reaction is stirred at 60°C for 24 hours. In step (4), the fluorescence peak position of the quantum dot and the plasmon resonance peak position of the Au nanoparticle are matched. It is required that the local field of the plasmon is around 530 nm to increase the emission rate of the quantum dot and enhance the emission intensity. In step (4), the concentration of quantum dots needs to be diluted to less than or equal to 10. -8 M, to achieve single-particle adsorption; The quantum dots in step (4) are ZnCdSeS / ZnS quantum dots containing oleic acid and oleylamine.
2. The method for preparing the high-brightness, flicker-free plasmon-exciton hybrid nanostructure according to claim 1, characterized in that, In step (4), the stirring speed at low speed and room temperature is 500 rpm, and the time is 2 hours.