Silver-based quantum dot composite material based on nanopore aluminum-silicon glass and preparation method of silver-based quantum dot composite material

Abstract

The invention discloses a room-temperature gas-phase preparation method of nano confinement silver-based quantum dot glass. Ag2S and AgInS2 quantum dots are synthesized by adopting Al2O3-SiO2 nano-pore glass in a confinement manner. The preparation method comprises the following steps: (1) mixing aluminum lactate, tetraethoxysilane and an Ag < + > / In < 3 + > precursor, and preparing co-doped sol by a sol-gel method; (2) sintering at 600 DEG C after gradient drying to form nano-pore aluminum-silicon glass with the pore diameter of 2-5nm; and (3) introducing H2S gas at room temperature, and growing the quantum dots in situ by utilizing a mesoporous confinement effect. In < 3 + > is introduced, the aluminum-silicon ratio and H2S reaction time are changed, and continuous adjustment of the Ag2S quantum dots in a 980-1070 nm near-infrared waveband and continuous adjustment of the AgInS2 quantum dots in a 620-700 nm visible light waveband are achieved respectively. Quantum dot synthesis is achieved under the room temperature condition, limitation of a traditional high-temperature process is broken through, the method has the advantages of being free of heavy metal pollution (containing no Cd / Pb), simplified in process and low in cost, and a new way is provided for controllable low-temperature preparation of silver-based quantum dot glass.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor nanomaterials and optical glass, specifically to a silver-based quantum dot (Ag2S and AgInS2) composite material based on nanoporous aluminosilicate glass and a preparation method thereof, in which the in-situ growth of quantum dots is achieved in the nanoporous glass through a room temperature H2S gas phase reaction. Background Art

[0002] Quantum dots have shown great potential in optoelectronic devices, bioimaging and other fields due to their excellent optical properties (high quantum yield, tunable luminescence). However, traditional metal sulfide quantum dots (such as CdS, PbS) face environmental and biosafety risks due to the presence of toxic heavy metal elements (Cd, Pb, As, etc.), which limits their practical application. Silver-based quantum dots (such as Ag2S, AgInS2) are considered ideal alternative materials due to their low toxicity and excellent near-infrared luminescence properties. However, the existing synthesis of silver-based quantum dots mostly relies on high-temperature liquid phase methods (>200°C) or complex ligand regulation processes, which makes quantum dots easy to agglomerate, have poor stability, and are difficult to directly integrate into optical devices. Therefore, the development of a green, low-temperature and scalable technology for the preparation of highly stable silver-based quantum dots has become an urgent need in the industry.

[0003] In the prior art, glass matrix has become the preferred carrier for quantum dot curing due to its high stability. For example, patents CN117623644A and CN119241068A proposed a room temperature vapor phase method to grow CdS / PbS / ZnS and CdZnS quantum dots in Al2O3-SiO2 nanoporous glass, which achieves low-temperature confined growth of quantum dots by reacting precursor doping with H2S gas. However, the above patents focus on toxic systems containing Cd / Pb and cannot meet environmental protection requirements. In addition, the glass curing technology for silver-based quantum dots is still limited to high-temperature annealing processes (such as the document Yin, D. et al. Advances in Condensed Matter Physics. 2015, 141056), which requires complex atmosphere control and high-temperature treatment (>600°C), resulting in high energy consumption, wide size distribution of quantum dots, and low fluorescence efficiency. Although the sol-gel method for preparing nanoporous glass makes it possible to confine the growth of quantum dots, existing technologies have not yet achieved efficient room-temperature integration of silver-based quantum dots in a glass matrix. In particular, there are significant technical gaps in avoiding high-temperature synthesis and toxic elements.

[0004] In the existing technology, the synthesis of silver-based quantum dots (such as Ag2S and AgInS2) generally relies on high-temperature liquid phase methods (>200°C) or complex annealing processes (>600°C), which leads to the following problems:

[0005] Process complexity and high energy consumption: High-temperature reactions require precise temperature control and atmosphere protection, which increases equipment costs and operational difficulty.

[0006] Dependence on toxic elements: Traditional quantum dots (such as CdS and PbS) contain heavy metals, which limits their application in environmentally sensitive fields.

[0007] Limited spectral regulation: Single-element quantum dots (such as Ag2S) can only adjust the emission wavelength (narrow range) by size, and the coupling regulation of pore size and quantum dot size in porous glass systems is difficult, making it difficult to achieve wide spectral coverage.

[0008] Insufficient stability of quantum dots: Colloidal quantum dots are prone to aggregation and photooxidation, affecting the long-term performance of the device. Summary of the Invention

[0009] In order to solve the above problems, the present invention proposes a method for efficient room temperature integration of silver-based quantum dots based on nanoporous glass. The core innovation lies in: + / In 3+ Using Ag / In as a non-toxic precursor, a sol-gel method was used to prepare nanoporous Al2O3-SiO2 glass, overcoming the toxic limitations of traditional Cd / Pb-based quantum dots. After the glass was sintered at high temperature, H2S gas was introduced at room temperature to exploit the nanopore confinement effect to achieve in situ, controllable growth of Ag2S and AgInS2 quantum dots. This method avoids high-temperature synthesis steps and significantly reduces energy consumption and process complexity. This method combines environmental friendliness, low-temperature efficiency, and device compatibility, offering a novel solution for the application of silver-based quantum dots in fields such as information security and bioimaging.

[0010] The technical solutions of the present invention are as follows:

[0011] A method for preparing silver-based quantum dots by vapor-phase growth at room temperature in nanoporous glass, characterized by comprising the following steps:

[0012] S1. Preparation of precursor sol: Aluminum lactate, tetraethyl silicate (TEOS) and Ag + and / or In 3+ The precursor solutions were mixed in proportion, the pH was adjusted to 2.5-3.5, and stirred to form a uniform sol;

[0013] S2. Dry gel forming: After aging the sol, drying by gradient heating to form a porous dry gel;

[0014] S3. High temperature sintering: The porous dry gel was sintered to 600 ° C in an air atmosphere to prepare Ag + single doped and Ag + / In 3+ Two types of co-doped nanoporous aluminosilicate glass, both with pore sizes of 2-5nm;

[0015] S4. Quantum dot growth: The sintered nanoporous glass is placed in H2S gas with a purity of ≥99.9% and reacted at room temperature for 3-48 hours to in situ generate Ag2S or AgInS2 quantum dots through the mesoporous confinement effect. The luminescence peak position of the Ag2S quantum dots can be continuously adjusted within the near-infrared range of 980-1070nm by adjusting the H2S gas reaction time; the luminescence wavelength of the AgInS2 quantum dots can be adjusted by introducing In 3+ By changing the aluminum-silicon ratio and the H2S reaction time, tunable emission in the visible light band of 620-700nm can be achieved.

[0016] Specifically, 2 mol% of aluminum lactate was weighed and dissolved in 6 mL of deionized water, and stirred on a magnetic stirrer at a rate of 800 r / min for 15 minutes until completely dissolved; then 10 mL of anhydrous ethanol was added, and the stirring was continued at a speed of 800 r / min for 15 minutes to form a uniform mixed solution; 97 mol% of tetraethyl silicate (TEOS) was added dropwise to the mixed system, and the pH value was adjusted to 3.0 (adjusted using 0.1 M HNO3 or NH3·H2O), and the reaction system was sealed and stirred for 12 hours to fully hydrolyze TEOS; 1 mol% of silver nitrate (AgNO3) powder was added (or replaced by a mixture of silver nitrate and indium nitrate, with an Ag / In molar ratio of 1:1), and stirring was continued for 12 hours under light-proof conditions to obtain a silver ion (or silver / indium co-) doped composite sol.

[0017] The resulting sol was injected into a polypropylene mold, sealed, and aged at room temperature for 24 hours. The mold was then transferred to a programmable temperature oven where the organic solvent was slowly volatilized to avoid stress cracking, resulting in a structurally complete three-dimensional porous xerogel. The gradient temperature ramp strategy was as follows:

[0018] The first stage: heating to 50°C at a rate of 0.5°C / min and keeping warm for 12 hours;

[0019] The second stage: heating to 80℃ at a rate of 0.2℃ / min and keeping warm for 48 hours;

[0020] The dry gel was then placed in an alumina crucible and sintered using a three-stage temperature control process:

[0021] The first stage: heating to 150°C at 1°C / min and keeping at this temperature for 4 hours to completely remove the residual solvent;

[0022] The second stage: continue to increase the temperature at 1°C / min to 450°C and keep it at that temperature for 4 hours to promote the decomposition of lactate;

[0023] The third stage: heating to 600°C at 1°C / min and holding for 4 hours to ablate carbon residues and reconstruct the glass network;

[0024] After sintering in an air atmosphere throughout the process, the nanoporous aluminosilicate glass (pore size distribution 2-5 nm) containing a silver (or silver / indium) precursor is obtained by naturally cooling to room temperature.

[0025] A silver-based quantum dot nanoporous glass composite prepared by the above method features quantum dots with a size of 2-5 nm and uniform distribution within the pores of aluminosilicate glass with a pore size of 2-5 nm. The emission wavelength of the AgInS2 quantum dots is adjustable between 620-700 nm, while the emission wavelength of the Ag2S quantum dots is adjustable between 980-1070 nm. The quantum yield is ≥5%, the quantum dot surface is free of obvious defects, and the fluorescence intensity decay is ≤35% after 40 hours of illumination. The composite has applications in optoelectronic devices, bioimaging, information security, and solar cells.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) Using Ag + / In 3+ The precursor replaces traditional heavy metals such as Cd, Pb, and As. The product does not contain any toxic elements and directly generates quantum dots through a room temperature (≤25°C) sulfurization reaction. It does not require complex temperature control equipment and reduces energy consumption by more than 60%.

[0028] 2) By introducing In 3+ By changing the aluminum-silicon ratio (Al / Si=0.02-0.1) and the H2S reaction time (3-48 hours), the emission wavelength of AgInS2 quantum dots can be adjusted in the range of 620-700nm, and the emission wavelength of Ag2S quantum dots can be adjusted in the range of 980-1070nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The 1 mol% Ag-doped + and 1 mol% In 3+ TEM and EDS mapping of quantum dot glass.

[0030] Figure 2 The 1 mol% Ag-doped samples prepared in Examples 1-2, 9-12, 21-24 of the present invention + Quantum dot glass, doped with 1 mol% Ag + and 1 mol% In 3+ Fluorescence spectra of quantum dot glass at different aluminum-silicon ratios.

[0031] Figure 3 The 1 mol% Ag-doped + and 1 mol% In 3+Photostability of quantum dot glass (continuous irradiation for 40 hours at 100 mW laser, Ex = 375 nm) DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to the embodiments.

[0033] The present invention combines a sol-gel method with a room temperature gas phase reaction to in-situ grow silver-based quantum dots (Ag2S and AgInS2) in nanoporous aluminosilicate glass (Al2O3-SiO2).

[0034] Example 1: Preparation of Ag2S quantum dot glass

[0035] Weigh 2 mol% of aluminum lactate and dissolve it in 6 mL of deionized water. Stir on a magnetic stirrer at a rate of 800 r / min for 15 minutes until completely dissolved. Subsequently, add 10 mL of anhydrous ethanol and continue stirring at the same speed for 15 minutes to form a uniform mixed solution. Add 97 mol% of tetraethyl silicate (TEOS) dropwise to the mixed system, and adjust the pH value to about 2.5-3.5 to form a sol precursor. After the closed reaction system, continue stirring for 12 hours to ensure that TEOS is fully hydrolyzed. Finally, add 1 mol% of silver nitrate powder and continue stirring in the dark for 12 hours to obtain a silver ion-doped composite sol.

[0036] The sol was injected into a polypropylene mold, sealed, and aged at room temperature for 24 hours. The mold was then transferred to a programmable temperature oven and heated using a gradient heating strategy: increasing the temperature to 50°C at a rate of 0.5°C / min for 12 hours, then to 80°C at a rate of 0.2°C / min for 48 hours. This process effectively prevented stress cracking caused by rapid evaporation of the organic solvent, while simultaneously forming a structurally intact xerogel by slowly removing water and ethanol.

[0037] The dry gel was placed in an alumina crucible and sintered in three stages under air atmosphere. After sintering, the mixture was naturally cooled to room temperature to obtain nanoporous aluminosilicate glass containing silver precursor. The specific temperature control procedure is as follows:

[0038] 1) Raise the temperature to 150°C at 1°C / min and hold for 4 hours to completely remove the residual solvent;

[0039] 2) Continue to raise the temperature to 450°C at the same rate and keep it for 4 hours to promote the complete decomposition of lactate;

[0040] 3) Finally, the temperature was raised to 600°C and maintained for 4 hours to complete the ablation of carbon residues and reconstruction of the glass network.

[0041] Finally, the glass sample was placed in a tube furnace reaction chamber, evacuated to -0.1 MPa, and then high-purity H₂S gas was introduced to atmospheric pressure. A sulfurization reaction was carried out at room temperature for 12 hours. The confinement effect of the mesoporous structure enabled the uniform nucleation and growth of Ag₂S quantum dots, ultimately yielding a quantum dot-glass composite with an emission wavelength of 980-1070 nm.

[0042] Example 2: Preparation of AgInS2 quantum dot glass

[0043] Prepare the basic sol system according to the method of Example 1 until TEOS is completely hydrolyzed. Prepare 1 mol% silver nitrate and 1 mol% indium nitrate (Ag + :In 3+ =1:1) aqueous solution, and then stirred in the dark for 24 hours to form a composite sol with uniform distribution of bimetallic ions.

[0044] The subsequent forming, drying and sintering processes are the same as those in Example 1. Through the co-sulfurization of the bimetallic precursor, AgInS2 ternary quantum dots are formed in the glass mesopores, and the emission wavelength range is 620-700 nm.

[0045] More examples are shown in Table 1. For specific preparation schemes, refer to Examples 1 and 2.

[0046]

[0047]

[0048] Table 1: Statistics of variable control for various examples of growing silver-based quantum dots in nanoporous glass using the vapor phase method at room temperature

[0049] in

[0050] Examples 3-12 are examples of regulation of Ag2S quantum dot glass

[0051] In Examples 3 to 6, the reaction time with H2S was changed to control the size growth of Ag2S quantum dots in the pores of nanoporous glass, thereby regulating the emission wavelength of the quantum dots. At the same time, the fluorescence quantum yield and fluorescence lifetime of the quantum dot glass were correspondingly improved.

[0052] In Examples 7 and 8, the doping concentration of the precursor was changed to control the concentration of quantum dots in the nanopores, thereby controlling the dispersion and agglomeration of the quantum dots.

[0053] In Examples 9 to 12, the aluminum-silicon molar ratio of the nanoporous glass was changed to regulate the pore size of the nanoporous glass, which directly affected the size of the quantum dots and directly regulated the emission wavelength range of the quantum dots.

[0054] Examples 13-24 are examples of regulation of AgInS2 quantum dot glass

[0055] Example 13-Example 16, the doping concentration of the two precursors was changed, Ag + With In 3+ The molar ratio is 1:0.1 to 1:4, which can realize the regulation of the visible luminescence intensity of quantum dot glass.

[0056] In Examples 17 to 20, the reaction time was extended from 3 h to 48 h, and the emission wavelength of the quantum dots was regulated.

[0057] In Examples 21 to 24, the aluminum-silicon molar ratio of the nanoporous glass was changed, which affected the pore size range of the glass and further affected the emission wavelength of the quantum dots.

[0058] The present invention uses a sol-gel method combined with a room-temperature vapor-phase sulfurization process to in-situ grow silver-based quantum dots in nanoporous glass. It has the advantages of simplified process, environmental protection, non-toxicity, and spectral tunability, and is suitable for optoelectronic devices, biosensors, information security and other fields.

Claims

1. A method for preparing silver-based quantum dots by vapor phase growth at room temperature in nanoporous glass, characterized in that: The following steps are involved: S1. Preparation of precursor sol: Aluminum lactate, tetraethyl silicate (TEOS) and Ag + and / or In 3+ The precursor solutions were mixed in proportion, the pH was adjusted to 2.5-3.5, and stirred to form a uniform sol; S2. Dry gel forming: After aging the sol, drying by gradient heating to form a porous dry gel; S3. High temperature sintering: The porous dry gel was sintered to 600 ° C in an air atmosphere to prepare Ag + single doped and Ag + / In 3+ Two types of co-doped nanoporous aluminosilicate glass, both with pore sizes of 2-5nm; S4. Quantum dot growth: The sintered nanoporous glass is placed in H2S gas with a purity of ≥99.9% and reacted at room temperature for 3-48 hours to in situ generate Ag2S or AgInS2 quantum dots through the mesoporous confinement effect. The luminescence peak position of the Ag2S quantum dots can be continuously adjusted within the near-infrared range of 980-1070nm by adjusting the H2S gas reaction time; the luminescence wavelength of the AgInS2 quantum dots can be adjusted by introducing In 3+ By changing the aluminum-silicon ratio and the H2S reaction time, tunable emission in the visible light band of 620-700nm can be achieved.

2. The preparation method according to claim 1, characterized in that Ag in step S1 + With In 3+ The molar ratio of Ag is 10:1 to 1:4, and Ag + and / or In 3+ The total doping concentration is 1% to 5% of the molar amount of the cations in the sol precursor.

3. The preparation method according to claim 1, characterized in that The gradient temperature drying in step S2 includes: heating to 50°C at 0.5°C / min and keeping the temperature for 12 hours, then heating to 80°C at 0.2°C / min and keeping the temperature for 48 hours.

4. The preparation method according to claim 1, characterized in that The sintering process in step S3 is divided into three stages: Stage 1: heating to 150°C at 1°C / min and holding for 4 hours to remove residual solvent; The second stage: heating to 450℃ at 1℃ / min and holding for 4 hours to decompose the organic ligand; The third stage: heating to 600°C at 1°C / min and keeping at this temperature for 4 hours to form a nanoporous glass network.

5. The preparation method according to claim 1, characterized in that The purity of the H2S gas in step S4 is ≥99.9%, and the glass system is evacuated to ≤-0.1 MPa before the reaction.

6. The preparation method according to claim 1, characterized in that The specific surface area of the nanoporous glass is 300-400m 2 / g, and the pore size distribution is 2-5nm.

7. The preparation method according to claim 1, characterized in that The silver-based quantum dots are one of Ag2S or AgInS2 or a mixture thereof, and do not contain toxic elements such as Cd, Pb, and As.

8. The preparation method according to claim 2, characterized in that When the Al / Si molar ratio is 0.02 and Ag + / In 3+ When the molar ratio is 1:1, the emission peak wavelength of AgInS2 quantum dots is 620±10nm, and the half-peak width is ≤134nm; when the Al / Si molar ratio is 0.02, and Ag + When the molar percentage is 1%, the emission peak wavelength of Ag2S quantum dots is 980±10nm and the half-peak width is ≤205nm.

9. A silver-based quantum dot nanoporous glass composite material prepared by the method according to any one of claims 1 to 8, characterized in that: The quantum dots are 2-5 nm in size and are evenly distributed within the 2-5 nm pores of aluminosilicate glass. The emission wavelength of the AgInS2 quantum dots is adjustable between 620-700 nm, while the emission wavelength of the Ag2S quantum dots is adjustable between 980-1070 nm. The quantum yield is ≥5%, and the fluorescence intensity decay is ≤35% after 40 hours of illumination.

10. The composite material according to claim 8, characterized in that It is used in optoelectronic devices, bioimaging, information security and solar cells.

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