Titanium dioxide-quantum dot-silicon dioxide composite material with multilayer core-shell structure as well as preparation method and application thereof

Abstract

The invention discloses a titanium dioxide-quantum dot-silicon dioxide composite material with a multilayer core-shell structure as well as a preparation method and application of the titanium dioxide-quantum dot-silicon dioxide composite material. The core layer is composed of titanium dioxide nano-particles, the quantum dot middle layer is adsorbed to the surface of the core layer in a bridging mode through a silane coupling agent, and the compact silicon dioxide shell layer wraps the quantum dot middle layer. The method comprises the following steps: titanium dioxide nanoparticles are subjected to silanization modification to introduce sulfydryl, quantum dots are subjected to ligand exchange to obtain water-soluble sulfhydrylated quantum dots, the water-soluble sulfhydrylated quantum dots and the titanium dioxide nanoparticles form a quantum dot-titanium dioxide compound through interaction of the sulfydryl, and finally, a silicon dioxide shell is formed through silicon source hydrolytic condensation under a weak alkaline condition. Through core-functional layer-shell collaborative design, the problems that a traditional quantum dot composite material is weak in binding force, the quantum dots are prone to falling off and the stability is poor are solved, and the quantum dot composite material can be widely applied to the fields of photoelectric devices, photocatalytic materials and biological fluorescent markers.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, and more specifically, relates to a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material, its preparation method and application. Background Technology

[0002] Quantum dots (QDs), as a novel type of photoactive nanomaterial, possess excellent optical properties such as size-tunable fluorescence emission, high quantum yield, and broad absorption spectrum, and have broad application prospects in optoelectronics, catalysis, and biomedicine. Among them, II-VI and IV-VI group semiconductor quantum dots (such as CdSe and CdS) have become a research hotspot due to their outstanding optical properties.

[0003] Titanium dioxide ( As a wide-bandgap semiconductor material, quantum dots (QD) possess excellent photocatalytic activity and electron transport capabilities, making them an ideal core material for constructing quantum dot-sensitized solar cells and photocatalytic systems. Combining QD with titanium dioxide can achieve synergistic optimization of optical and electron transport performance; however, existing composite methods have significant technical drawbacks: firstly, QD and titanium dioxide are mostly bonded through physical adsorption or electrostatic interactions, resulting in weak bonding and easy detachment of QD during use; secondly, severe interfacial charge recombination affects the overall material performance; and thirdly, QD exposed to the environment is susceptible to corrosion by water and oxygen, leading to photobleaching, oxidation, and other phenomena, resulting in extremely poor stability.

[0004] silicon dioxide ( Quantum dots (QDs) possess strong chemical inertness, good biocompatibility, and tunable structure, making them commonly used as coating protective layers to enhance material stability. Currently, while existing technologies have attempted to prepare quantum dot-titanium dioxide or quantum dot-silica composites, a multilayer core-shell structure system with stable structure, high quantum dot loading, and strong interfacial bonding has not yet been formed. Existing coating technologies suffer from insufficient shell density, stringent preparation conditions (high temperature, high pressure), and poor versatility, making it difficult to meet the performance requirements of practical applications.

[0005] Therefore, developing a multilayer core-shell composite material with a reasonable structural design, mild preparation process, excellent stability, and strong quantum dot loading has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0006] To address the shortcomings or improvement needs of existing technologies, this invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, its preparation method, and its applications. The aim is to solve the technical problems of weak bonding, easy quantum dot detachment, and poor stability in existing quantum dot composite materials. The composite material of this invention adopts a synergistic structural design of "titanium dioxide core - quantum dot intermediate layer - silica shell." A strong bond between quantum dots and titanium dioxide is achieved through the bridging effect of a silane coupling agent and the strong interaction between thiol groups. A dense silica shell constructs a physicochemical protective barrier. Specifically, the silane coupling agent introduces thiol functional groups onto the surface of titanium dioxide, forming a stable bond with the thiolized quantum dots after ligand exchange, completely solving the problem of easy quantum dot detachment in traditional composite methods. The outer silica shell effectively isolates the material from environmental factors such as water and oxygen, inhibits photobleaching and oxidative degradation of quantum dots, and significantly improves the material's optical and chemical stability. Simultaneously, the titanium dioxide core provides a good electron transport channel, and the quantum dot intermediate layer maintains excellent optical properties with adjustable dimensions. These three elements complement each other, achieving simultaneous optimization of material structural stability and optical performance.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material is provided, comprising the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0008] The core layer consists of titanium dioxide nanoparticles with a particle size of 50–200 nm.

[0009] Furthermore, the quantum dots of the intermediate functional layer are II-VI or IV-VI group semiconductor quantum dots, preferably one or more of CdSe, CdS, CdTe, PbS, and ZnSe.

[0010] Secondly, embodiments of the present invention provide a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material, comprising the following steps: S100: Silanization modification of titanium dioxide surface;

[0011] Titanium dioxide nanoparticles were dispersed in a liquid solvent and ultrasonically dispersed until the system was homogeneous. The pH of the reaction system was adjusted with acid, and a silane coupling agent with terminal thiol groups was added. The reaction was carried out at room temperature under magnetic stirring until complete. Then, the mixture was centrifuged, washed several times with methanol, and dried under vacuum to obtain thiolized titanium dioxide. ); S200: Quantum dot ligand exchange;

[0012] Quantum dots with oleic acid (OA) as the original ligand were dispersed in a liquid solvent, diluted to a specific concentration, and then exchange ligands were added. The reaction was carried out under magnetic stirring at room temperature. The mixture was then centrifuged and the supernatant was discarded. The precipitate was washed multiple times with anhydrous ethanol to obtain mercapto-based water-soluble quantum dots (MPA-QDs). S300: Quantum dot adsorption;

[0013] The thiolated titanium dioxide obtained in S100 and the water-soluble thiolated quantum dots obtained in S200 were co-dispersed in chloroform. The reaction was stirred at room temperature until complete, then centrifuged and washed multiple times with chloroform to remove unadsorbed quantum dots, yielding a quantum dot-titanium dioxide composite. ); S400: Silicon dioxide outer shell coating;

[0014] The quantum dot-titanium dioxide composite obtained from S300 was dispersed in a liquid solvent, a silicon source was added, the pH of the system was adjusted, the silicon source was hydrolyzed under weakly alkaline conditions, the reaction was stirred at room temperature until complete, centrifuged and dried, and a silica shell was deposited on its surface to obtain a multilayer core-shell structured composite material. ).

[0015] In S100, the silane coupling agent is γ-mercaptopropyltrimethoxysilane, the reaction solvent is methanol, and the pH of the reaction system is 3-4; the mass ratio of the silane coupling agent to titanium dioxide is 1:(2-4).

[0016] Furthermore, in S200, the exchange ligand is 3-mercaptopropionic acid; the reaction solvent is chloroform.

[0017] Furthermore, in S300, the solvent for the mixed reaction is chloroform.

[0018] Furthermore, in S400, the silicon source is [missing information], the weakly alkaline conditions are achieved by adding an ammonia-ethanol solution, the pH value is adjusted to 8-9, and the reaction solvent is chloroform.

[0019] Furthermore, in S400, the amount of methyl orthosilicate used is 100-500 μL per 15 mL of solvent.

[0020] Thirdly, embodiments of the present invention provide an application of a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material, characterized in that the optoelectronic device fabricated is a quantum dot-sensitized solar cell or a light-emitting diode.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The multi-layered core-shell titanium dioxide-quantum dot-silica composite material of the present invention features a highly efficient and synergistic structural design. It employs a three-layer core-shell structure consisting of a titanium dioxide core, a quantum dot intermediate layer, and a silica outer shell. Titanium dioxide provides electron transport channels and structural support, quantum dots serve as photoactive centers, and silica acts as a protective barrier. These three elements complement each other, achieving synergistic optimization of the material's optical properties and structural stability.

[0022] 2. The multilayer core-shell structured titanium dioxide-quantum dot-silica composite material of the present invention exhibits strong and stable interfacial bonding. The silane coupling agent MPTMS is used for... The modification introduces terminal thiol groups (-SH), which then combine with MPA-QDs that also contain thiol groups (-SH) through a strong SS covalent bond. This results in a stronger and more stable binding force than traditional physical or electrostatic adsorption methods, effectively preventing quantum dots from falling off during use.

[0023] 3. The multi-layered core-shell structure of the titanium dioxide-quantum dot-silica composite material of the present invention exhibits significantly improved stability. The outermost dense silica shell effectively isolates the internal quantum dots from environmental factors such as water and oxygen, greatly improving the photostability and chemical stability of the quantum dots and extending the service life of the material.

[0024] 4. The multilayer core-shell structured titanium dioxide-quantum dot-silica composite material of the present invention has a mild and versatile preparation method. The entire preparation process is carried out at room temperature, under mild conditions, with low energy consumption, simple operation, and easy to scale up production. This method is applicable to quantum dots of different types and sizes (such as CdS, PbS, ZnSe, etc.) and titanium dioxide particles of different sizes, and has good versatility. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation method of a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to an embodiment of the present invention; Figure 2 This invention provides an embodiment of a multilayered core-shell structured titanium dioxide-quantum dot-silica composite material. Transmission electron microscopy (TEM) images of core-shell composite materials clearly show the core ( ), intermediate layer (QDs) and outer layer ( The three-layer structure of TMOS is shown in the right figure. The surface is covered with a layer The left image shows a layer, while the comparative image on the left does not have a covering layer; Figure 3This is a schematic diagram of TEM test results for an embodiment and a comparative example of a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Example 1 like Figure 2 and Figure 3 As shown, this embodiment of the invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0028] like Figure 1 As shown, in a second aspect, embodiments of the present invention provide a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material, comprising the following steps: S100: Silanization modification of titanium dioxide surface.

[0029] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.5 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 200 μL of MPTMS silane coupling agent was added, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged, washed three times with methanol, and dried in a vacuum oven at 60°C for 0.5 hours to obtain a white powder product. .

[0030] S200: Quantum dot ligand exchange.

[0031] Take 600 μL of a 0.9 g / mL CdSe quantum dot solution with oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant. Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdSe QDs).

[0032] S300: Quantum dot adsorption.

[0033] All of the preparations made from S100 The powder and all MPA-CdSe QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. After centrifugation, the mixture was washed twice with chloroform to remove unadsorbed quantum dots, yielding a solid product. .

[0034] S400: Silicon dioxide shell coating.

[0035] S300 obtained The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 200 μL of TMOS was added, followed by dropwise addition of 10 μL of a catalyst solution diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) at room temperature with stirring for 24 hours. After the reaction was complete, the product was centrifuged, washed three times with ethanol, and dried to obtain the final product. powder.

[0036] Example 2 This invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0037] This embodiment provides a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation method in this embodiment is the same as that in Example 1, but the specific parameters are different. The differences are: in S100, the pH is adjusted to 3.0, the amount of MPTMS is 250 μL, and the reaction time is 10 hours; in S200, the reaction time is 4 hours; in S300, the reaction time is 2 hours; and in S400, the amount of TMOS is 300 μL, the pH is adjusted to 8.0, and the reaction time is 20 hours. The specific preparation method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0038] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.0 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 250 μL of MPTMS silane coupling agent (silane coupling agent to titanium dioxide mass ratio 1:2) was added, and the mixture was reacted at room temperature for 10 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. .

[0039] S200: Quantum dot ligand exchange.

[0040] Take 600 μL of a 0.9 g / mL CdSe quantum dot solution with oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 4 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdSe QDs).

[0041] S300: Quantum dot adsorption.

[0042] All of the preparations made from S100 The powder and all MPA-CdSe QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 2 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, and the resulting solid product was obtained. .

[0043] S400: Silicon dioxide shell coating.

[0044] S300 obtained The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 300 μL of TMOS was added (300 μL per 15 mL solvent), followed by dropwise addition of 10 μL of a catalyst diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.0) at room temperature with stirring for 20 hours. After the reaction was complete, the product was centrifuged (8000 rpm for 10 minutes), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product. powder.

[0045] Example 3 This invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0046] This embodiment provides a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation method in this embodiment is the same as that in Example 1, but the specific parameters differ. Specifically, in S100, the pH is adjusted to 4.0, the amount of MPTMS is 167 μL (mass ratio to titanium dioxide 1:3), and the reaction time is 14 hours; in S200, CdS quantum dots are used, the amount of MPA is 7 mL, and the reaction time is 6 hours; in S300, the reaction time is 4 hours; and in S400, the amount of TMOS is 400 μL, the pH is adjusted to 9.0, and the reaction time is 18 hours. The specific preparation method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0047] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 4.0 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 167 μL of MPTMS silane coupling agent (silane coupling agent to titanium dioxide mass ratio 1:3) was added, and the mixture was reacted at room temperature for 14 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. .

[0048] S200: Quantum dot ligand exchange.

[0049] Take 600 μL of a 0.9 g / mL CdS quantum dot solution with oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 7 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 6 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdS QDs).

[0050] S300: Quantum dot adsorption.

[0051] All of the preparations made from S100 The powder and all MPA-CdS QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 4 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, and the resulting solid product was obtained. .

[0052] S400: Silicon dioxide shell coating.

[0053] S300 obtained The solution was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 400 μL of TMOS (400 μL per 15 mL solvent) was added, followed by dropwise addition of 10 μL of a catalyst diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 9.0) at room temperature with stirring for 18 hours. After the reaction was complete, the solution was centrifuged (8000 r / min, 10 min), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product. powder.

[0054] Example 4 This invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0055] This embodiment provides a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation method in this embodiment is the same as that in Example 1, but the specific parameters differ. Specifically, in S100, acetic acid is used to adjust the pH to 3.8, the titanium dioxide particle size is 150 nm, and the amount of MPTMS is 200 μL (mass ratio of MPTMS to titanium dioxide 1:2.5); in S200, ZnSe quantum dots are used, and the amount of MPA is 9 mL; in S300, a mixed solvent of chloroform and ethanol (ethanol volume percentage 10%) is used; and in S400, the amount of TMOS is 100 μL, and the reaction time is 22 hours. The specific preparation method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0056] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.8 with acetic acid. Add 500 mg of titanium dioxide with an average particle size of 150 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 200 μL of MPTMS silane coupling agent (silane coupling agent to titanium dioxide mass ratio 1:2.5) was added, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. .

[0057] S200: Quantum dot ligand exchange.

[0058] Take 600 μL of a 0.9 g / mL ZnSe quantum dot solution containing oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 9 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-ZnSe QDs).

[0059] S300: Quantum dot adsorption.

[0060] All of the preparations made from S100 The powder and all MPA-ZnSe QDs prepared by S200 were co-dispersed in a mixed solvent of chloroform and ethanol (ethanol volume percentage 10%), and magnetically stirred at room temperature for 3 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, yielding the solid product. .

[0061] S400: Silicon dioxide shell coating.

[0062] S300 obtained The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 100 μL of TMOS (100 μL per 15 mL solvent) was added, followed by dropwise addition of 10 μL of a catalyst diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) at room temperature with stirring for 22 hours. After the reaction was complete, the product was centrifuged (8000 r / min for 10 minutes), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product. powder.

[0063] Example 5 This invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0064] This embodiment provides a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation method in this embodiment is the same as that in Example 1, but the specific parameters differ. Specifically, in S100, the pH is adjusted to 3.2, the amount of MPTMS is 220 μL (approximately 1:2.27 mass ratio to titanium dioxide), and the reaction time is 13 hours; in S200, PbS quantum dots are used, and the ethanol / acetone mixed solvent is used for precipitation washing; in S400, the amount of TMOS is 150 μL, the pH is adjusted to 8.8, and the reaction time is 22 hours. The specific preparation method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0065] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.2 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 200 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 125 μL of MPTMS silane coupling agent (silane coupling agent to titanium dioxide mass ratio 1:4) was added, and the mixture was reacted at room temperature for 13 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. .

[0066] S200: Quantum dot ligand exchange.

[0067] Take 600 μL of a 0.9 g / mL oleic acid ligand PbS quantum dot solution (in chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with a 1:1 (volume ratio) ethanol / acetone mixture to obtain MPA-modified quantum dots (MPA-PbS QDs).

[0068] S300: Quantum dot adsorption.

[0069] All of the preparations made from S100 The powder and all MPA-PbS QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, and the resulting solid product was obtained. .

[0070] S400: Silicon dioxide shell coating.

[0071] S300 obtained The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 500 μL of TMOS was added (500 μL per 15 mL solvent), followed by dropwise addition of 10 μL of a catalyst diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.8) at room temperature with stirring for 24 hours. After the reaction was complete, the product was centrifuged (8000 r / min for 10 minutes), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product. powder.

[0072] Example 6 This invention provides a multi-layered core-shell structured titanium dioxide-quantum dot-silica composite material, which consists of the following structure from the inside out: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; Outer shell: A dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

[0073] This embodiment provides a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation method in this embodiment is the same as that in Example 1, but the specific parameters differ. Specifically, in S100, 50nm titanium dioxide and MPTMS are used in a 1:4 mass ratio to titanium dioxide; in S400, 500 μL TMOS is used. The specific preparation method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0074] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.5 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 50 nm (the minimum particle size of titanium dioxide). The powder was ultrasonically dispersed for 10 minutes. Then, 125 μL MPTMS silane coupling agent (silane coupling agent to titanium dioxide mass ratio 1:4, maximum) was added, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. .

[0075] S200: Quantum dot ligand exchange.

[0076] Take 600 μL of a 0.9 g / mL CdTe quantum dot solution (in chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdTe QDs).

[0077] S300: Quantum dot adsorption.

[0078] All of the preparations made from S100 The powder and all MPA-CdTe QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, and the resulting solid product was obtained. .

[0079] S400: Silicon dioxide shell coating.

[0080] S300 obtained The solution was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 500 μL of TMOS was added (maximum volume per 15 mL solvent), followed by dropwise addition of 10 μL of a catalyst diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) with stirring at room temperature for 22 hours. After the reaction was complete, the solution was centrifuged (8000 r / min, 10 min), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product. powder.

[0081] Comparative Example 1 This invention provides a comparative method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation process of this comparative method is basically the same as that of Example 1, except that the silane coupling agent γ-mercaptopropyltrimethoxysilane (MPTMS) in S100 is replaced with γ-aminopropyltriethoxysilane (APTES) without a mercapto group. This aims to verify the key role of the mercapto-containing silane coupling agent in the stability of the bonding between quantum dots and titanium dioxide. The method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0082] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.5 with acetic acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was then mixed with 200 μL of MPTMS silane coupling agent, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged, washed three times with methanol, and dried in a vacuum oven at 60°C for 0.5 hours to obtain a white powder product. .

[0083] S200: Quantum dot ligand exchange.

[0084] Take 3000 μL of a 0.9 g / mL CdSe quantum dot solution (five times the concentration of Example 1) containing oleic acid ligands, diluted with 5 mL of chloroform. Then add 10 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant. Wash the precipitate three times with a mixed solvent of ethanol / acetone to obtain MPA-modified quantum dots (MPA-CdSe QDs).

[0085] S300: Quantum dot adsorption.

[0086] All of the preparations made from S100 The powder and all MPA-CdSe QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. Subsequently, without centrifugation, the next coating operation was carried out directly in the solution.

[0087] S400: Silicon dioxide shell coating.

[0088] S300 obtained 200 μL of TMOS was added to the solution, followed by dropwise addition of 10 μL of a catalyst solution diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) at room temperature with stirring for 18 hours. After the reaction was complete, the product was centrifuged, washed three times with ethanol, and dried to obtain the final product. powder.

[0089] Comparative Example 2 This invention provides a comparative example of a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation process of this comparative example is basically the same as that of Example 1, except that the silanization modification step on the surface of S100 titanium dioxide is omitted. The introduction of thiol groups onto the surface aims to verify the effect of silanization modification on quantum dots and... The crucial role of bonding force. This includes the following steps: S100: Directly take 500 mg of titanium dioxide with an average particle size of 100 nm ( Powder, no silanization modification required, ready for use; S200: Take 600 μL of a 0.9 g / mL CdSe quantum dot solution with oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min). Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdSe QDs). S300: The original titanium dioxide powder from S100 and all MPA-CdSe QDs prepared from S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. The mixture was then centrifuged (8000 r / min, 10 min), washed twice with chloroform to remove unadsorbed quantum dots, yielding the solid product. ; S400: The result obtained from S300 The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 200 μL of TMOS was added, followed by dropwise addition of 10 μL of a catalyst solution diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) with stirring at room temperature for 24 hours. After the reaction was complete, the product was centrifuged three times (8000 r / min, 10 min) and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product.

[0090] Comparative Example 3 This invention provides a comparative example of a method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation process of this comparative example is basically the same as that of Example 1, except that the core exchange ligand 3-mercaptopropionic acid of S200 is replaced with citric acid without a mercapto group, thus disrupting the mercapto-mercapto interactions. This aims to verify the effect of the mercapto-modified ligand on the adsorption stability of quantum dots. The method includes the following steps: S100: Take 15 mL of methanol in a 50 mL round-bottom flask and adjust the pH to 3.5 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 200 μL of MPTMS silane coupling agent was added, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged (8000 r / min, 10 minutes), washed three times with methanol, and dried in a vacuum oven at 60℃ for 0.5 hours to obtain a white powder product. ; S200: Take 600 μL of oleic acid ligand CdSe quantum dot solution with a concentration of 0.9 g / mL (chloroform as solvent), and dilute with 10 mL of chloroform. Then add 8 mL of citric acid solution (replacing 3-mercaptopropionic acid, without mercapto groups), and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant (10000 r / min, 15 min), and wash the precipitate three times with anhydrous ethanol to obtain citric acid-modified quantum dots; S300: All of the materials prepared by S100 The powder and the modified quantum dots prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. The mixture was then centrifuged (8000 r / min, 10 min), and washed twice with chloroform to remove unadsorbed quantum dots, yielding a solid product. ; S400: The result obtained from S300 The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 200 μL of TMOS was added, followed by dropwise addition of 10 μL of a catalyst solution diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) at room temperature with stirring for 24 hours. After the reaction was complete, the product was centrifuged (8000 r / min, 10 min), washed three times with ethanol, and dried in a vacuum oven at 60 °C for 0.5 hours to obtain the final product.

[0091] Comparative Example 4 This invention provides a comparative method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material. The preparation process of this comparative method is basically the same as that of Example 1, except that the silicon source precursor TMOS (tetramethoxysilane) of S400 is replaced with TEOS (tetraethoxysilane), thus altering the hydrolysis-condensation kinetics of the silicon source precursor. This aims to verify the influence of the silicon source precursor type on the structure and properties of the silica outer shell and the overall stability of the composite material. The method includes the following steps: S100: Silanization modification of titanium dioxide surface.

[0092] Take 15 mL of methanol into a 50 mL round-bottom flask and adjust the pH to 3.5 with dilute nitric acid. Add 500 mg of titanium dioxide with an average particle size of 100 nm. The powder was ultrasonically dispersed for 10 minutes. Then, 200 μL of MPTMS silane coupling agent was added, and the mixture was reacted at room temperature for 12 hours under magnetic stirring. After the reaction was complete, the mixture was centrifuged, washed three times with methanol, and dried in a vacuum oven at 60°C for 0.5 hours to obtain a white powder product. .

[0093] S200: Quantum dot ligand exchange.

[0094] Take 600 μL of a 0.9 g / mL CdSe quantum dot solution with oleic acid ligand (chloroform) and dilute with 10 mL of chloroform. Then add 8 mL of 3-mercaptopropionic acid (MPA) solution and stir magnetically at room temperature for 5 hours. After the reaction, centrifuge and discard the supernatant. Wash the precipitate three times with anhydrous ethanol to obtain MPA-modified quantum dots (MPA-CdSe QDs).

[0095] S300: Quantum dot adsorption.

[0096] All of the preparations made from S100 The powder and all MPA-CdSe QDs prepared by S200 were co-dispersed in 15 mL of chloroform and magnetically stirred at room temperature for 3 hours. After centrifugation, the mixture was washed twice with chloroform to remove unadsorbed quantum dots, yielding a solid product. .

[0097] S400: Silicon dioxide shell coating.

[0098] S300 obtained The product was redispersed in 15 mL of chloroform and sonicated to ensure uniform dispersion. 200 μL of TEOS was added, followed by dropwise addition of 10 μL of a catalyst solution diluted 1:1 (v / v) with concentrated ammonia and anhydrous ethanol. The reaction was carried out under weakly alkaline conditions (pH 8.5) at room temperature with stirring for 24 hours. After the reaction was complete, the product was centrifuged, washed three times with ethanol, and dried to obtain the final product. powder.

[0099] The samples prepared in Example 1 and the comparative example were tested: 1. TEM characterization: as shown in the attached document. Figure 1 As shown, the product of Example 1 exhibits a clear core-shell structure. There is a dense layer outside the core. The shell consists of two layers, with quantum dots distributed between them.

[0100] 2. Fluorescence stability test: Initial PLQY values ​​were recorded for the samples prepared in Example 1 and the comparative example. The samples were simultaneously placed in an oven and baked at 85°C for a period of time before the PLQY test. The results showed that the comparative example (uncoated)... The fluorescence of the sample from Example 1 decreased by more than 30% in PLQY within 48 hours, while the fluorescence intensity of the sample from Example 1 decreased by less than 10% under the same conditions, demonstrating that... The shell provides excellent protection.

[0101] TEM tests were performed on the samples prepared in Example 2 and the comparative example: 1. TEM characterization: as shown in the attached document. Figure 2 As shown, the product of Example 2 achieves a higher quantum dot concentration and a thinner coating layer by controlling the amount of reactants.

[0102] 2. Fluorescence Stability Test: Initial PLQY tests were performed on the samples of Example 2. Analysis of the results showed that, under initial non-thermal aging conditions, the thinner coating layer of Example 2 resulted in higher initial light extraction efficiency, specifically: under the same external conditions, the initial PLQY of Example 2 was approximately 5% higher than that of Example 1. Subsequently, the samples prepared in Example 2 and the comparative example were placed in an oven and baked continuously at 85°C. Comparative Example (Uncoated) The fluorescence of the sample in Example 1 decreased by more than 30% in PLQY within 48 hours, while the fluorescence intensity of the sample in Example 2 decreased by less than 10% under the same conditions, but the degree of attenuation was slightly higher than that in Example 1. This proves that a thinner coating layer can result in better initial light emission, but the subsequent protective performance will be relatively reduced.

[0103] In summary, this invention successfully prepared a novel and stable core-shell composite material, which exhibits significant advantages in photostability and has promising application prospects.

[0104] This invention is not limited to the specific embodiments described above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention should also fall within the protection scope of this invention.

Claims

1. A multilayered core-shell structured titanium dioxide-quantum dot-silica composite material, characterized in that, From the inside out, it includes the following structure: Core layer: Titanium dioxide nanoparticles; Intermediate functional layer: quantum dots bridged and adsorbed on the surface of the core layer via silane coupling agents; And the outer shell: a dense silicon dioxide protective layer that surrounds the quantum dot intermediate layer.

2. The multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 1, characterized in that, The titanium dioxide nanoparticles have a particle size of 50–200 nm. The quantum dot is a II-VI or IV-VI group semiconductor quantum dot, preferably one or more of CdSe, CdS, CdTe, PbS, and ZnSe.

3. A method for preparing the composite material as described in claim 1 or 2, characterized in that, Includes the following steps: S100: Silanization modification of titanium dioxide surface: Titanium dioxide nanoparticles were dispersed in a liquid solvent and ultrasonically dispersed until the system was homogeneous. The pH of the reaction system was adjusted with acid, and a silane coupling agent with terminal thiol groups was added. The reaction was carried out at room temperature under magnetic stirring, then centrifuged, washed multiple times with methanol, and dried under vacuum to obtain thiolized titanium dioxide. S200: Quantum dot ligand exchange: Quantum dots with oleic acid as the original ligand were dispersed in a liquid solvent, diluted to a specific concentration, and then exchange ligands were added. The reaction was carried out under magnetic stirring at room temperature. The mixture was then centrifuged and the supernatant was discarded. The precipitate was washed multiple times with anhydrous ethanol to obtain thiolized water-soluble quantum dots. S300: Quantum dot adsorption: The thiolized titanium dioxide obtained in S100 and the water-soluble thiolized quantum dots obtained in S200 were co-dispersed in a liquid solvent. The reaction was carried out at room temperature with stirring. Then, the mixture was centrifuged and washed multiple times with a liquid solvent to remove unadsorbed quantum dots, thus obtaining a quantum dot-titanium dioxide composite. S400: Silicon dioxide outer casing: The quantum dot-titanium dioxide composite obtained from S300 was dispersed in a liquid solvent, a silicon source was added, the pH of the system was adjusted, the silicon source was hydrolyzed under weakly alkaline conditions, the reaction was stirred at room temperature until it was fully reacted, centrifuged and dried, and a silicon dioxide shell was deposited on its surface to obtain a multilayer core-shell structured composite material.

4. The method for preparing the multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 3, characterized in that, In S100, the silane coupling agent is γ-mercaptopropyltrimethoxysilane, the reaction solvent is methanol, and the pH of the reaction system is 3-4.

5. The method for preparing the multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 3, characterized in that, In S200, the exchange ligand is 3-mercaptopropionic acid; the reaction solvent is chloroform.

6. The method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 3, characterized in that, In S300, the solvent for the mixed reaction is chloroform.

7. The method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 3, characterized in that, In S400, the silicon source is methyl orthosilicate, and the weakly alkaline condition is achieved by adding an ammonia-ethanol solution, with the pH value adjusted to 8-9.

8. The method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 7, characterized in that, In S400, the reaction solvent is chloroform.

9. The method for preparing a multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 3, characterized in that, In S100, the mass ratio of silane coupling agent to titanium dioxide is 1:(2-4); In S400, the amount of methyl orthosilicate used is 100-500 μL per 15 mL of solvent.

10. The application of the multilayer core-shell structured titanium dioxide-quantum dot-silica composite material according to claim 1 or 2, characterized in that, The optoelectronic device is a quantum dot sensitized solar cell or a light-emitting diode.

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