Composition for surface modification of quantum dots and preparaion method of water-soluble quantum dots using the same

Abstract

The present invention relates to a composition for surface modification of quantum dots and a method for manufacturing water-soluble quantum dots using the same. More specifically, the invention provides a novel surface modification composition capable of improving photoluminescence quantum efficiency (PLQY) and minimizing full width at half maximum (FWHM) during the process of manufacturing quantum dots, and enables the production of water-soluble surface-modified quantum dots using the same, thereby allowing for application in various fields including bioimaging and device fabrication.

Description

Technology Field

[0001] The present invention relates to a composition for surface modification of quantum dots and a method for manufacturing water-soluble quantum dots using the same. Background Technology

[0002] Indium Phosphate (InP) Quantum Dots (QDs) are semiconductor nanoparticles with a crystal lattice structure composed of indium and phosphorus atoms. These quantum dots possess unique optical and electronic properties due to size-dependent quantum confinement effects. By adjusting the size of the quantum dots, the emission wavelength of InP quantum dots can be precisely controlled; as the size of the quantum dots decreases, the band gap increases, resulting in a shorter emission wavelength. This tunability makes InP quantum dots highly useful in various applications, such as displays, lighting, and bioimaging. One of the key features of InP quantum dots is their high photoluminescence quantum efficiency (PLQY), which results in high efficiency as a light emitter. This characteristic is particularly advantageous in applications requiring vivid and intense colors, such as display and lighting technologies. InP quantum dots boast superior chemical and optical stability compared to other semiconductor quantum dots, such as CdSe or CdTe. This stability plays a crucial role in ensuring the lifespan of application products by minimizing the degradation of optical properties.

[0003] Furthermore, InP quantum dots are evaluated as having relatively high biocompatibility compared to other semiconductor quantum dots containing toxic heavy metals such as cadmium. For this reason, InP quantum dots are suitable for various biomedical applications, including bioimaging, drug delivery, and biosensors. InP quantum dots are used in display technologies, such as QLED (Quantum Dot Light Emitting Diode) displays, to improve color purity, brightness, and energy efficiency, and are utilized in LED lighting applications to enhance Color Reproduction Index (CRI), efficiency, and color saturation. Additionally, thanks to their bright and stable luminescence properties, InP quantum dots are used as fluorescent probes for biological imaging. They are utilized in technologies such as fluorescence microscopy and vivo imaging, and their potential for application in photovoltaic devices to improve light absorption and efficiency is also being investigated. Overall, InP quantum dots offer versatile properties and are being applied in various fields, including optoelectronics, photonics, biotechnology, and renewable energy.

[0004] Meanwhile, water-soluble quantum dots are semiconductor nanocrystals surface-modified or functionalized with hydrophilic functional groups, which allow them to be dispersed in aqueous solutions. These functional groups play a crucial role in stabilizing the quantum dots in water and imparting specific properties required for various applications. Common functional groups in water-soluble quantum dots include carboxyl groups (-COOH), amine groups (-NH2), hydroxyl groups (-OH), polyethylene glycol (PEG), and zwitterionic ligands. Overall, the selection of functional groups for water-soluble quantum dots is determined by desired application requirements, such as surface charge, stability, biocompatibility, and targeting ability.

[0005] Accordingly, the inventors of the present invention realized that if a novel surface modification composition capable of improving photoluminescence quantum efficiency (PLQY) and minimizing full width at half maximum (FWHM) could be prepared during the process of manufacturing quantum dots, then water-soluble surface-modified quantum dots could be manufactured using this composition, thereby enabling applications in various fields including bioimaging and device fabrication, and thus completed the present invention. Prior art literature

[0006] Republic of Korea Published Patent Application No. 10-2009-0114112 The problem to be solved

[0007] The objective of the present invention is to produce a novel surface modification composition that can improve PLQY and minimize FWHM during the process of manufacturing quantum dots, and to apply this to various fields including bioimaging and device fabrication by using it to produce water-soluble surface-modified quantum dots.

[0008] Meanwhile, the technical problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0009] To achieve the above objective, the present invention provides a composition for surface modification of quantum dots comprising 3-mercaptopropyltrimethoxysilane (3-MPTMS) of the following chemical formula 1; and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid of the following chemical formula 2.

[0010] [Chemical Formula 1]

[0011]

[0012] [Chemical Formula 2]

[0013] .

[0014] The weight ratio of the above 3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:0.5 to 3.

[0015] The above quantum dots may be InP, CdSe, CdS, CdTe, PbS, PbSe, or InAs-based quantum dots.

[0016] The above quantum dots may be InP-based quantum dots.

[0017] The above quantum dots may be InP / ZnSe / ZnS.

[0018] The above InP / ZnSe / ZnS has a core nucleus of λ abs It may be a red quantum dot having an absorption peak of 570-590 nm.

[0019] In addition, the present invention provides a method for producing water-soluble quantum dots comprising: (a) a first surface modification step of mixing quantum dots and a 3-MPTMS solution; and (b) a second surface modification step of mixing 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid with the first surface modification product.

[0020] Prior to step (a) above, the method may additionally include step (a-1) of preparing a 3-MPTMS solution by mixing an organic solvent and a pH adjuster with 3-MPTMS.

[0021] The above organic solvent may include one or more selected from the group consisting of N,N'-dimethylformamide (DMF), N-methyl-pyrrolidone (NMP), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc).

[0022] The above pH adjuster may include one or more selected from the group consisting of ammonia water, potassium hydroxide, sodium hydroxide, sodium hydroxide, cesium hydroxide, sodium bicarbonate, and sodium carbonate.

[0023] Step (a-1) above may involve mixing a pH adjuster to adjust the pH to 11 or higher.

[0024] The weight ratio of the quantum dots and 3-MPTMS is 1:5 to 15, and the weight ratio of the 3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:0.5 to 3.

[0025] In addition, the present invention provides a method for preparing water-soluble quantum dots comprising the step of (A) mixing quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid.

[0026] The weight ratio of the above quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:5 to 15:10 to 20. Effects of the invention

[0027] According to the present invention, a novel surface modification composition can be prepared that improves PLQY and minimizes FWHM during the process of manufacturing quantum dots, and by using this to manufacture water-soluble surface-modified quantum dots, it can be applied to various fields including bioimaging and device fabrication.

[0028] Meanwhile, the effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below. Brief explanation of the drawing

[0029] FIG. 1 is a schematic diagram illustrating the process of synthesizing an InP core according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating the process of manufacturing InP / ZnSe / ZnS red quantum dots through a shelling process after etching an InP core according to one embodiment of the present invention. FIG. 3 is a synthesis mechanism of InP / ZnSe / ZnS red quantum dots according to one embodiment of the present invention. FIG. 4 is a schematic diagram illustrating the process of water-soluble surface modification of InP / ZnSe / ZnS red quantum dots using a composition for quantum dot surface modification according to one embodiment of the present invention. FIG. 5 is a schematic diagram illustrating the process of water-soluble surface modification of InP / ZnSe / ZnS red quantum dots using 3-Mercaptopropionic acid (3-MPA) according to a comparative example of the present invention. FIG. 6 is a scanning electron microscope (SEM) image of an InP / ZnSe / ZnS red quantum dot surface modified with a quantum dot surface modification composition according to the present invention [(a) Scale bar: 50 nm (b) Scale bar: 5 nm (first quantum dot) (c) Scale bar: 5 nm (second quantum dot) (d) Scale bar: 5 nm (measurement of core and shell size of the second quantum dot). Figure 7 is the X-ray photoelectron analysis (XPS) result of InP / ZnSe / ZnS red quantum dots surface-modified with a quantum dot surface modification composition according to the present invention. FIG. 8 shows (a) UV visible light spectral analysis (VD=1-(v / p)) and (b) photoluminescence spectral analysis results of InP / ZnSe / ZnS red quantum dots surface-modified with a quantum dot surface modification composition according to the present invention. Specific details for implementing the invention

[0030] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be interpreted as being limited to the embodiments below. These embodiments are provided to more fully explain the present invention to those with average knowledge in the art. Accordingly, the shapes of the elements in the drawings have been exaggerated to emphasize clearer explanations.

[0031] All terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0033] The direct interaction between 3-MPA (3-Mercaptopropionic acid), which is conventionally used as a surface modifier for quantum dots, and the quantum dot surface has shown the problem of reducing PLQY. Accordingly, there is a need for an alternative method that can modify the surface of quantum dots to be water-soluble without damaging PLQY. In order to solve these conventional problems, the present invention proposes a modification method utilizing a binary mixture to enhance ligand exchange and transition water-soluble quantum dots to a polar environment.

[0034] Hereinafter, a composition for surface modification of quantum dots according to the present invention and a method for manufacturing water-soluble quantum dots using the same will be described in detail.

[0036] composition for quantum dot surface modification

[0037] According to the present invention, a composition for surface modification of quantum dots is provided, comprising 3-mercaptopropyltrimethoxysilane (3-MPTMS) of the following chemical formula 1; and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid (5-Oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid) of the following chemical formula 2. When quantum dots are surface modified to be water-soluble using the composition for surface modification of quantum dots according to the present invention, the photoluminescence quantum efficiency (PLQY) is improved and the full width at half maximum (FWHM) can be minimized compared to the case where a conventional surface modification agent (e.g., 3-mercaptopropionic acid, 3-MPA) is used.

[0038] [Chemical Formula 1]

[0039]

[0040] [Chemical Formula 2]

[0041] .

[0042] According to one embodiment of the present invention, the weight ratio of 3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:0.5 to 3, 1:1 to 2, 1:1.2 to 1.8, or 1:1.4 to 1.6, but is not limited thereto. Within the above weight ratio range, the surface of the quantum dot can be modified to be water-soluble while simultaneously exhibiting excellent photoluminescence quantum efficiency.

[0043] According to one embodiment of the present invention, the quantum dot may be an InP, CdSe, CdS, CdTe, PbS, PbSe, or InAs-based quantum dot, but is not limited thereto, and various types of quantum dots requiring water-soluble surface modification may be used. Specifically, the quantum dot may be an InP-based quantum dot, more specifically, the quantum dot may be InP / ZnSe / ZnS, and even more specifically, the InP / ZnSe / ZnS has a core nucleus λ abs It may be a red quantum dot having an absorption peak of 570-590 nm. In this case, if the surface is modified to be water-soluble using a composition for quantum dot surface modification, the surface of the quantum dot can be modified to be water-soluble while simultaneously exhibiting excellent photoluminescence quantum efficiency and a minimized full width at half maximum value.

[0045] Method for manufacturing InP / ZnSe / ZnS quantum dots

[0046] According to the present invention, a method for manufacturing InP / ZnSe / ZnS quantum dots is provided, comprising: (1) an InP core synthesis step; (2) an etching step of the synthesized InP core; and (3) a shelling step of the InP core after etching is completed.

[0047] According to one embodiment of the present invention, the step (1) may include: (1-1) a nucleation step in which In(PA)₃, Zn(OA)₂ and TMS₃P / TOP are mixed and reacted in a ratio of 2:0.5:1 to 2:2:1; and (1-2) a nucleation growth step in which a mixture of In-ODE (In(OAc)3-ODE), Zn-TOA and TMS₃P / TOP is simultaneously injected and reacted.

[0048] In step (1-1) above, if the mixing ratio of In(PA)₃, Zn(OA)₂, and TMS₃P / TOP is 2:0.5:1, 2:1:1, or 2:2:1, uniform and stable quantum dot nuclei can be produced. Additionally, step (1-1) above may be performed by increasing the temperature to 260 to 320°C, 280 to 310°C, or 290 to 310°C, but is not limited thereto.

[0049] The indium precursor (In(PA)₃) used in step (1-1) above can be prepared by mixing In(OAc)₃ (indium acetate), a carboxylic acid (specifically, palmitic acid PA), and 1-octadecene (ODE) in a molar ratio of 1:2 to 5:12 to 18 or 1:2 to 4:15 to 17. Although In(OAc)₃ and the carboxylic acid have high chemical stability and may have low reactivity, after mixing with ODE, at an appropriate temperature (100 to 150°C or 100 to 140°C ° The activity of the precursor can be increased by processing at C (or 100 to 130 or 100 to 120°C). This allows In atoms to effectively participate in quantum dot nucleation. The carboxylic acid acts as a ligand to provide stability to the In precursor and contributes to preventing defect formation on the quantum dot surface. Meanwhile, if the precursor is processed in an argon environment during preparation, oxidation and contamination of the precursor are prevented, enabling the production of high-purity quantum dots.

[0050] The zinc precursor (Zn(OA)₂) used in step (1-1) above can be prepared by mixing Zn(OAc)₂, oleic acid (OA), and trioctylamine (TOA) in a molar ratio of 1:1 to 5:3 to 10 or 1:1.5 to 2.5:4 to 7. Zn plays a key role in the formation of quantum dot core and shell structures and is used as an important Zn-based material in the shelling step. Oleic acid (OA) can increase the stability of the zinc precursor and improve the dispersibility of Zn atoms during the reaction. TOA can help Zn react uniformly by controlling reactivity. The zinc precursor can combine with the In precursor to improve the quality of the core and serve as an appropriate source of Zn atoms during the formation of the shell structure.

[0051] Through the above step (1-2), the quantum dot size is adjusted to optimize it for having an appropriate absorption wavelength, which can control luminescence efficiency and color purity. When the VD value is greater than 0.4, a quantum dot with a high structural completeness is formed, which can maximize optical properties and stability. In addition, if the nucleation reaction is carried out until the absorption wavelength reaches λabs 570-590 nm, the synthesized InP core can be used to synthesize red quantum dots. Furthermore, the above step (1-2) can be performed by increasing the temperature to 260 to 320°C, 280 to 310°C, or 290 to 310°C, but is not limited thereto.

[0052] According to one embodiment of the present invention, step (2) is a step of etching the surface of an InP core using ZnF₂ and a carboxylic acid (an organic acid having C1-C20 carbon atoms, specifically an organic acid having C18 carbon atoms) to remove an oxide film generated during the InP core synthesis process. Since the InP core has the property of easily oxidizing in air, an oxide film may be formed, and because the oxide film thus formed lowers the luminescence efficiency of the quantum dot having the InP core, the step of etching the oxide film is very important. That is, through the above-described etching step, defects on the surface of the quantum dot can be minimized to significantly improve the luminescence efficiency (PLQY), and through the surface treatment of the etching step, the core-shell interface becomes more robust and the durability of the quantum dot can be improved. In addition, the carboxylic acid acts as a surfactant and can play a role in increasing the chemical stability of the quantum dot.

[0053] The above (2) step may be performed at a temperature of 100 to 280°C, 150 to 280°C, 200 to 280°C, or 250 to 270°C for 0.25 to 24 hours, 0.25 to 12 hours, 0.3 to 10 hours, or 0.4 to 1 hour, but is not limited thereto.

[0054] According to one embodiment of the present invention, step (3) is a shelling step of forming a shell on an InP core that has been etched using Zn(OA)₂, TOP-Se and TOP-S at a temperature of 300 to 340°C or 310 to 330°C or 315 or 325°C. The shell structure protects the core, stabilizes the quantum dots from the external environment (humidity, temperature, etc.), and can optimize optical properties by reducing charge separation between the core and the shell.

[0055] The selenium precursor (TOP-Se) and sulfur precursor (TOP-S) used in step (3) above can be prepared by mixing TOP and Se / S, respectively, in a molar ratio of 1:1 to 5 or 1:1.5 to 2.5. When mixed within the above molar ratio range, the uniformity of the shell structure can be ensured, and the luminescence efficiency and environmental stability of the quantum dots can be improved. Selenium (Se) and sulfur (S) are important elements that control the bandgap and luminescence characteristics of quantum dots. TOP-Se and TOP-S can play a role in minimizing defects between the core and the shell and increasing luminescence efficiency. In this process, by adjusting the molar ratio of Se and S to optimize the supply, imbalance problems during the reaction can be prevented, and electronic structure mismatch between the core and the shell can be minimized. Se and S stabilized by the TOP ligand have high reactivity and can support an efficient growth process.

[0056] According to one embodiment of the present invention, after step (3), a step of surface modification to stabilize quantum dots can be further performed by injecting a mixture of zirconium isopropoxide and alkyl thiol (C6-C12, specifically C8) at a temperature of 80 to 280°C or 100 to 280°C or 150 to 280°C or 250 to 270°C. By performing surface modification by injecting a mixture of zirconium isopropoxide and alkyl thiol after the shelling step, the thermal stability and luminescence characteristics of the quantum dots can be improved.

[0058] Method for producing water-soluble quantum dots using a composition for quantum dot surface modification

[0059] According to the present invention, a method for producing water-soluble quantum dots is provided, comprising: (a) a first surface modification step of mixing quantum dots and a 3-MPTMS solution; and (b) a second surface modification step of mixing 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid with the first surface modification product.

[0060] According to one embodiment of the present invention, prior to step (a), the method may additionally include the step of (a-1) preparing a 3-MPTMS solution by mixing an organic solvent and a pH adjuster with 3-MPTMS.

[0061] According to one embodiment of the present invention, the organic solvent may include one or more selected from the group consisting of N,N'-dimethylformamide (DMF), N-methyl-pyrrolidone (NMP), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc), but is not limited thereto, and any type of organic solvent capable of dissolving 3-MPTMS may be used. Specifically, the organic solvent may be DMF.

[0062] According to one embodiment of the present invention, the pH adjuster may include one or more selected from the group consisting of ammonia water, potassium hydroxide, sodium hydroxide, sodium hydroxide, cesium hydroxide, sodium bicarbonate, and sodium carbonate, but is not limited thereto, and any type of basic pH adjuster capable of adjusting the pH of the 3-MPTMS solution to 11 or higher may be used. Specifically, the pH adjuster may be ammonia water.

[0063] According to one embodiment of the present invention, the weight ratio of the quantum dots and 3-MPTMS is 1:5 to 15 or 1:7 to 13 or 1:8 to 12 or 1:9 to 11, and The weight ratio of the above 3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:0.5 to 3, 1:1 to 2, 1:1.2 to 1.8, or 1:1.4 to 1.6. Within the above weight ratio range, the surface of the quantum dot can be modified to be water-soluble while simultaneously exhibiting excellent photoluminescence quantum efficiency.

[0064] In addition, according to the present invention, a method for producing water-soluble quantum dots is provided, comprising the step of (A) mixing quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid.

[0065] The weight ratio of the above quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid may be 1:5 to 15:10 to 20 or 1:7 to 13:12 to 18 or 1:8 to 12:13 to 17 or 1:9 to 11:14 to 16. Within the above weight ratio range, the surface of the quantum dots can be modified to be water-soluble while simultaneously exhibiting excellent photoluminescence quantum efficiency and minimized full width at half maximum values.

[0067] The above description explains the technical concept of the present invention using one embodiment, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments described in this invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention shall be interpreted by the claims, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0068] The present invention will be explained in more detail below through examples.

[0070] Experimental materials

[0071] The experimental materials prepared for the embodiments of the present invention were as follows, and these materials were purchased from Sigma Aldrich (Korea). Additionally, unless otherwise noted, all chemical substances were used exactly as purchased.

[0072] Experimental Materials: Indium acetate (In(OAc)3), tris(trimethylsilyl)phosphine (TMS3P), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), zinc acetate (Zn(OAc)2), trioctylphosphine (TOP), 1-dodecanethiol (DDT), carboxylic acids (RCOOH: acetic acid (AA), propionic acid, palmitic acid (PA), oleic acid (OA), lauric acid (LA), myristic acid (My), hexanoic acid (HA), 10-undecenoic acid (UDA), octanoic acid (OTA)), selenium (Se), sulfur (S), 1-octadecane (ODE), UDA), selenium (Se), sulfur (S), 1-octadecane (ODE), acetone, hexane, ethanol, toluene, trioctylamine (TOA), metal halide (CaF2, SrF2, CuF2, AgF, AuF, CuCl2, AgCl, ZnCl2, HgCl2, BeBr2, MgBr2, CaBr2, SrBr, CuBr2, AgBr, CaCl2, SrCl2, AlCl3, GaCl3, InCl3, MgCl2, SnCl2, PbCl2, LiBr, NaBr, BeF2, MgF2, ZnF2, HgF2, AlF3, GaF3, InF3, NaF, KF, SnF2, PbF2, LiCl, NaBr, KBr, CuBr, AuBr, ZnBr2)

[0074] <Example>

[0075] 1. Preparation and Synthesis of Precursors

[0076] All reactions were carried out using a Schlenk line in an argon environment. The preparation of the precursor mixtures followed specific ratios. First, an indium precursor (In(OAc)3) was prepared by mixing indium acetate (In(OAc)3), palmitic acid (PA), and 1-octadecane (ODE) in a molar ratio of 1:3:16. Additionally, a zinc precursor (Zn(OA)2) was prepared by mixing zinc acetate (Zn(OAc)2), oleic acid (OA), and trioctylamine (TOA) in a molar ratio of 1:2:6. Furthermore, a selenium precursor (TOP-Se) and a sulfur precursor (TOP-S) were prepared by mixing trioctylphosphine (TOP) and Se / S in a ratio of 1:2, respectively. Subsequently, all mixtures were vacuum-treated at a high temperature of 100 to 150°C under a pressure of 0.1-0.15 torr. All prepared precursor mixtures were stored in an argon environment for use in subsequent experiments.

[0078] 2. Synthesis of InP Core

[0079] Referring to Figures 1 and 3, during the core nucleation stage, a mixture composed of In(PA)3, Zn(OA)2, and TMS3P / TOP was mixed in a ratio of 2:2:1, the target emission wavelength range was set to 450–500 nm, and the temperature was gradually increased to 300°C. Subsequently, during the nucleation stage, a mixture of In-ODE, Zn-TOA, and TMS3P / TOP was simultaneously injected at 300°C, and nucleation was carried out by proceeding the reaction until the absorption wavelength reached 570–590 nm and the Volume Distribution (VD) value exceeded 0.4. Upon completion of the reaction, the product was washed with non-polar solvents such as acetone, chloroform, and toluene. The emission wavelength Cores corresponding to the 570-590 nm range were used for the synthesis of red quantum dots (QDs).

[0081] 3. Fabrication of InP / ZnSe / ZnS Red Quantum Dots via Etching and Shelling

[0082] Referring to Figures 2 and 3, the etching of the InP core prepared in Example 2 above was performed at a temperature of 260°C for 30 minutes using a combination of ZnF2 and a carboxylic acid (an organic acid having C18 carbon atoms). After the etching was completed, shelling was carried out at a temperature of 320°C using Zn(OA)2, TOP-Se, and TOP-S, respectively. After shelling, a mixture of zirconium isopropoxide and an alkyl thiol (C8) was injected at a high temperature of 260°C to further perform surface modification for stability. Finally, the product after shelling and surface modification was cooled to room temperature, washed with hexane, chloroform, toluene, heptane, octane, ethanol, etc., and the synthesized QD was stored in normal heptane.

[0084] 4. Surface modification into water-soluble quantum dots using a surface modification composition

[0085] The InP / ZnSe / ZnS red quantum dots prepared from Example 3 above were surface modified into water-soluble quantum dots using an etching composition according to the present invention (3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid).

[0086] Specifically, referring to Fig. 4, 20 ml of DMF was added to 2 g of 3-MPTMS and an aqueous ammonia solution was added to raise the pH to 11 or higher, and the mixture was stirred at room temperature for 3 hours. Then, 0.2 g of InP / ZnSe / ZnS red quantum dots were added to perform primary surface modification, and then 3 g of 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid was added to further modify the surface.

[0088] <Comparative Example>

[0089] 1. Surface modification of water-soluble quantum dots using 3-MPA

[0090] The InP / ZnSe / ZnS red quantum dots prepared from Example 3 above were surface modified into water-soluble quantum dots using 3-MPA (3-Mercaptopropionic acid).

[0091] Specifically, referring to Fig. 5, 2 g of 3-MPA was dissolved in 10 ml of DMF, 2 ml of ammonia water was added and stirred at room temperature for 3 hours, then InP / ZnSe / ZnS red quantum dots were added and stirred for 24 hours. Afterward, the solution was mixed with acetonitrile and the quantum dots were washed using a centrifuge at 9000 rpm for 5 minutes.

[0093] <Experimental Example>

[0094] 1. Scanning Electron Microscope (SEM) Analysis

[0095] Scanning electron microscope images of surface-modified InP / ZnSe / ZnS red quantum dots using an etching composition (3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid) from Example 4 above were analyzed.

[0096] InP / ZnSe / ZnS quantum dots without surface modification have irregular shelling, so improvements are needed to enhance quantum dot stability under harsh environmental conditions. Since a thin shell thickness can cause quantum tunneling and reduce the lifespan of the quantum dots, improving shelling through surface modification is essential.

[0097] Referring to Figure 6, it can be seen that the surface-modified InP / ZnSe / ZnS red quantum dots have a triangular shape and maintain a spherical structure with precise dimensions. Additionally, it was confirmed that the size of the core located at the center is 3.02 nm, and the shelling extends to a range exceeding 4.8 nm.

[0099] 2. X-ray Photoelectronic Analysis (XPS)

[0100] X-ray photoelectron analysis was performed on surface-modified InP / ZnSe / ZnS red quantum dots using an etching composition (3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid) from Example 4 above.

[0101] Referring to Figure 7 and Table 1, XPS analysis confirmed all elements, proving that InP quantum dots were formed with an InP / ZnSe / ZnS structure. Oxygen and carbon signals originate from ligands, while sulfur originates from ZnS. Zinc signals represent the core, ZnSe, and ZnS, and corresponding counter elements were also detected. Zirconium is attributed to the modification of the outer shell. The core is composed of In, P, and Zn, which can be confirmed through the core synthesis process (see Example 2). Additionally, the following elements were identified based on their bonding levels: C1s (285.15 eV), Zn2p3 (1021.73 eV), O1s (532.39 eV), Se3d (54.78 eV), P2p (139.08 eV), S2p (161.08 eV), Zr3d (180.2 eV), and I3d (627.44 eV).

[0102] Name Peak BE FWHM eV Area (P) CPS.eV Atomic % C1s 285.15 3.05 818061.09 69.15 Zn2p3 1021.73 1.82 431883.56 3.43 O1s 532.39 3.14 469864.92 16.43 Se3d 54.78 2.65 107902.28 4.98 P2P 139.08 0 9357.95 0.54 S2p 161.08 2.39 71629.47 2.98 Zr3d 180.2 3.14 262636.2 2.3 I3d3 627.44 1.32 30597.17 0.19

[0104] 3. UV-Visible Spectroscopic Analysis and PL Photoluminescence Spectroscopic Analysis

[0105] UV visible light spectral analysis and PL photoluminescence spectral analysis were performed on surface-modified InP / ZnSe / ZnS red quantum dots using an etching composition (3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid) from Example 4 above.

[0106] Red quantum dots with an InZnP / ZnSe / ZnS core-shell structure were successfully synthesized using an eco-friendly approach, exhibiting enhanced photoluminescence quantum efficiency (PLQY) and a narrowed full width at half maximum (FWHM). The UV-Visible absorption characteristics of the core served as a criterion for selecting the optimal absorption peaks of the red and green QDs. The wavelength and van der Waals value of the core play important roles in determining the FWHM and emission wavelength of the QDs, respectively. When the VD value was 0.4 or less, the FWHM increased beyond 45 nm, whereas when it was 0.4 or greater, the FWHM decreased to 40 nm. Furthermore, fine shelling and etching processes contributed additionally to the reduction of FWHM, ensuring excellent photophysical properties of the synthesized quantum dots.

[0107] The photoluminescence (PL) spectrum provides important information regarding the emission wavelength and full width at half maximum (FWHM) of the quantum dots. A noticeable wavelength change of an average of 40 nm was observed after shelling and etching, indicating that the core wavelength was precisely controlled according to research requirements. Furthermore, the enhancement of PL intensity after the etching process significantly increases the photoluminescence quantum efficiency (PLQY). As a result of etching, PLQY increased by more than 20%; while unetched QDs had a PLQY of less than 75%, etched QDs achieved a PLQY of 100%. In addition, etching significantly improved both FWHM and PLQY.

[0108] The mismatch at the core-shell interface is effectively adjusted through doping and etching at the core-shell interface. By carefully managing the reaction rate of inorganic-organic heteroligands through adjustments of temperature, concentration, and time, shelling at the core interface is enhanced, which consequently affects PLQY and FWHM.

[0109] Etching using ZnF2 / carboxylic acid (a C1 to C20 range HA-organic acid) is emerging as a cost-effective and safe option for quantum dot fabrication. Furthermore, the etching process is adaptable to both polar and non-polar environments, including TOA, ODE, DMF, pyridine, pyrole, TOP, THF, DMSO, and various mixtures thereof. In particular, the polar environment exhibits a higher PLQY (>85%) and lower FWHM (≤40 nm) compared to the non-polar environment, where PLQY remains at approximately 60% and FWHM reaches approximately 65 nm [see Fig. 8].

[0111] 4. Comparative Analysis of Photoluminescence Quantum Efficiency (PLQY) According to Surface Modifiers

[0112] PLQY was analyzed for each of the InP / ZnSe / ZnS red quantum dots surface-modified using the etching composition (3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid) from Example 4 [indicated as InP / ZnSe / ZnS-CFTES in Table 2 below], the InP / ZnSe / ZnS red quantum dots surface-modified using 3-MPA from Comparative Example 1 [indicated as InP / ZnSe / ZnS-MPA in Table 2 below], and the un-surface-modified InP / ZnSe / ZnS red quantum dots [indicated as InP / ZnSe / ZnS in Table 2 below].

[0113] Referring to Table 2 below, InP / ZnSe / ZnS red quantum dots were synthesized with excellent photophysical properties and were surface modified with 3-MPA or the etching composition according to the present invention for application in quantum dot-polymer compositions. Although the PLQY of the InP / ZnSe / ZnS red quantum dots without surface modification was the highest at ≥92%, it can be confirmed that when the surface was modified with the etching composition according to the present invention [InP / ZnSe / ZnS-CFTES], it showed a value of ≥89%, which is higher than the PLQY of the QD when the surface was modified with 3-MPA [InP / ZnSe / ZnS-MPA].

[0115] λ (nm) FWHM (nm) PLQY (%) InP / ZnSe / ZnS 615-630 42±1 ≥92 InP / ZnSe / ZnS-MPA 615-630 42±1 ≥80 InP / ZnSe / ZnS -CFTES 615-630 42±1 ≥89

[0117] Accordingly, the present invention confirmed a synthesis method for InP red quantum dots exhibiting excellent photophysical properties and enhanced water solubility through surface modification. Through the selection of appropriate parameters and an etching process, the PLQY was increased by more than 20%, and the synthesized quantum dots exhibited a full width at half maximum (FWHM) of 40±2 and a photoluminescence quantum efficiency (PLQY) exceeding 95%. Through the surface modification process using the quantum dot composition according to the present invention, quantum dots containing hydrophobic oleic acid were successfully converted into water-soluble quantum dots, which exhibited a PLQY approximately 9% better than quantum dots surface-modified with 3-MPS. These results indicate that quantum dots surface-modified using the quantum dot composition according to the present invention can be effectively utilized in various application fields, including bioimaging and device fabrication.

[0119] The above detailed description is illustrative of the present invention. Furthermore, the foregoing describes preferred embodiments of the present invention, and the present invention may be used in various other combinations, modifications, and environments. That is, modifications or alterations are possible within the scope of the concept of the invention disclosed herein, the scope equivalent to the disclosed content, and / or the scope of the art or knowledge. The described embodiments describe the best state for implementing the technical concept of the present invention, and various modifications required in specific fields of application and uses of the present invention are possible. Accordingly, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Additionally, the appended claims should be interpreted as including other embodiments.

Claims

Claim 1 Composition for quantum dot surface modification comprising 3-mercaptopropyltrimethoxysilane (3-MPTMS) of Formula 1 below; and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid of Formula 2 below: [Formula 1] [Chemical Formula 2] . Claim 2 A composition for quantum dot surface modification according to claim 1, wherein the weight ratio of 3-MPTMS and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid is 1:0.5 to 3. Claim 3 A composition for surface modification of quantum dots according to claim 1, wherein the quantum dots are InP, CdSe, CdS, CdTe, PbS, PbSe, or InAs-based quantum dots. Claim 4 In paragraph 3, the composition for surface modification of quantum dots, wherein the quantum dots are InP-based quantum dots. Claim 5 In claim 4, the quantum dot surface modification composition is in which the quantum dots are InP / ZnSe / ZnS. Claim 6 In claim 5, the above InP / ZnSe / ZnS has a core nucleus of λ abs A composition for surface modification of quantum dots, which is a red quantum dot having an absorption peak of 570-590 nm. Claim 7 A method for producing water-soluble quantum dots comprising: (a) a first surface modification step of mixing quantum dots and a 3-MPTMS solution; and (b) a second surface modification step of mixing 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid with the first surface modification product. Claim 8 A method for manufacturing water-soluble quantum dots according to claim 7, wherein prior to step (a) above, (a-1) a step of preparing a 3-MPTMS solution by mixing an organic solvent and a pH adjuster with 3-MPTMS. Claim 9 A method for producing water-soluble quantum dots according to claim 8, wherein the organic solvent comprises one or more selected from the group consisting of N,N'-dimethylformamide (DMF), N-methyl-pyrrolidone (NMP), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc). Claim 10 A method for manufacturing water-soluble quantum dots according to claim 8, wherein the pH adjuster comprises one or more selected from the group consisting of ammonia water, potassium hydroxide, sodium hydroxide, sodium hydroxide, cesium hydroxide, sodium bicarbonate, and sodium carbonate. Claim 11 A method for manufacturing water-soluble quantum dots according to claim 8, wherein step (a-1) involves mixing a pH adjuster to adjust the pH to 11 or higher. Claim 12 A method for producing water-soluble quantum dots according to claim 7, wherein the weight ratio of the quantum dots to 3-MPTMS is 1:5 to 15, and the weight ratio of the 3-MPTMS to 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid is 1:0.5 to 3. Claim 13 (A) A method for preparing water-soluble quantum dots comprising the step of mixing quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid. Claim 14 A method for producing water-soluble quantum dots according to claim 13, wherein the weight ratio of the quantum dots, 3-MPTMS, and 5-oxo-1-[3-(trimethoxysilyl)propyl]-3-pyrrolidinecarboxylic acid is 1:5 to 15:10 to 20.

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