High-performance core-shell colloidal quantum well nanocrystal, colloidal nanocrystal self-assembly echo wall mode laser and preparation method of high-performance core-shell colloidal quantum well nanocrystal
By self-assembling a ring-shaped core-shell colloidal quantum well nanocrystalline film within a quartz optical fiber, the problems of uneven gain film and complex core/gradient shell CQW preparation caused by the traditional drop-casting method are solved, realizing a low-threshold, high-stability CQW-WGM laser with broad prospects for micro-nano laser and biological detection applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-04-03
AI Technical Summary
The colloidal nanocrystalline WGM laser gain film prepared by the traditional drop-casting method is non-uniform, resulting in significant scattering loss and high laser threshold. Furthermore, the preparation process of the core/gradient shell CQW is complex and has low reproducibility, making it difficult to realize the practical application of high-performance CQW-WGM lasers.
Core-shell colloidal quantum well nanocrystals were formed by reacting cadmium myristate with a selenium precursor solution. Subsequently, a CdS buffer layer and a Cd1-xZnxS alloy shell were added. Through capillary effect, the nanocrystals self-assembled in a quartz optical fiber to form a ring-shaped core-shell colloidal quantum well nanocrystal film, thus forming a whispering-gallery optical microcavity structure.
This technology achieves low-threshold, high-stability CQW-WGM laser output with a simplified fabrication process, improving the uniformity of gain films and the repeatability of material preparation, while reducing optical loss and operational complexity.
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Figure CN121780148A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of laser technology, and more specifically, to a high-performance core-shell colloidal quantum well nanocrystal, a colloidal nanocrystal self-assembled whispering-gallery mode laser, and its fabrication method. Background Technology
[0002] Micro / nano laser devices based on colloidal nanocrystals combine the advantages of solution processing, the excellent luminescent properties of nanomaterials, and the optical field manipulation capabilities of micro / nano structures, showing great promise in flexible electronics and integrated optoelectronics. Among various colloidal nanocrystal materials, two-dimensional colloidal quantum wells (CQWs) stand out due to their one-dimensional quantum confinement effect along the thickness direction, possessing characteristics such as the narrowest emission linewidth, larger absorption cross-section, higher exciton binding energy, and slowest Auger recombination rate. CQWs with core-shell structures combine the unique optical properties of quantum wells with the stability and efficiency advantages of core-shell structures, making them the most promising optical gain materials. Combining CQWs with whispering-gallery (WGM) optical microcavities with high quality factor and small mode volume holds promise for realizing low-threshold, high-performance miniaturized lasers.
[0003] However, achieving high-performance CQW-WGM lasers faces two major challenges: first, the poor film quality and uncontrollable performance caused by traditional drop-casting processes; and second, the complex and low reproducibility of the preparation process of advanced core-shell materials (such as graded-shell CQW).
[0004] Specifically, traditional colloidal nanocrystalline WGM lasers typically employ a drop-casting method to form a gain film on the surface of microspheres. The drop-casting method produces inhomogeneous gain films, introducing significant scattering losses, limiting the microcavity quality factor, and increasing the lasing threshold. Furthermore, the randomness of the process leads to poor spectral repeatability, hindering practical application. On the other hand, core / gradient shell CQWs, as highly promising gain materials, can effectively reduce interface defects by smoothing lattice mismatch. However, their traditional fabrication relies on real-time, precise control of the precursor ratio and temperature, making the operation complex and difficult to guarantee reproducibility.
[0005] Therefore, breaking through existing technological bottlenecks and developing a simple, stable, and efficient alternative method is an inevitable requirement for promoting the practical application of CQW-WGM lasers.
[0006] In view of this, the present invention is proposed. Summary of the Invention
[0007] The purpose of this invention is to provide a high-performance core-shell colloidal quantum well nanocrystal, a colloidal nanocrystal self-assembled whispering-gallery mode laser, and a method for preparing the same, in order to solve or improve the above-mentioned technical problems.
[0008] This invention can be implemented as follows: In a first aspect, the present invention provides a method for preparing high-performance core-shell colloidal quantum well nanocrystals, comprising the following steps: Cadmium myristate was reacted with a selenium precursor solution and 1-octadecene, followed by the addition of cadmium acetate to continue the reaction, resulting in a nuclear colloidal quantum trap nanocrystal dispersion. A mixture of 1-octadecene, a portion of cadmium precursor solution, and a portion of sulfur precursor solution was mixed, followed by the addition of a nuclear colloidal quantum well nanocrystal dispersion, and then further addition of a portion of cadmium precursor solution and a portion of sulfur precursor solution to form a CdS buffer layer. Subsequently, a zinc precursor solution and a portion of sulfur precursor solution were added to form CdS on the surface of the CdS buffer layer. 1-x Zn x S alloy shell; then annealing and cooling to obtain high-performance core-shell colloidal quantum well nanocrystals; The selenium precursor solution is obtained by mixing selenium powder with 1-octadecene; the cadmium precursor solution is obtained by heating a mixture of cadmium oleate and 1-octadecene; the sulfur precursor solution is obtained by mixing 1-octylthiol and 1-octadecene; and the zinc precursor solution is obtained by heating a mixture of zinc oleate, oleylamine, and 1-octadecene.
[0009] In an optional embodiment, the heating temperature during the preparation of the cadmium precursor solution is 68°C to 72°C. And / or, in the cadmium precursor solution, the ratio of cadmium oleate to 1-octadecene is (0.35 mmol / L to 0.45 mmol / L): (1.5 mL to 2.5 mL).
[0010] In an optional embodiment, the heating temperature during the zinc precursor solution preparation process is 68°C to 72°C. And / or, in the zinc precursor solution, the ratio of zinc oleate, oleylamine and 1-octadecene is (0.12 mmol~0.15 mmol):(0.2 mL~0.3 mL):(0.4 mL~0.6 mL).
[0011] In an optional embodiment, the ratio of 1-octylthiol to 1-octadecene in the sulfur precursor solution is (80 μL~90 μL):(3.5 mL~4.5 mL). And / or, in the selenium precursor solution, the ratio of selenium powder to 1-octadecene is (94.5 mg ~ 95 mg): (7.5 mL ~ 8.5 mL).
[0012] In an optional embodiment, the preparation of the nuclear colloidal quantum well nanocrystal dispersion includes: sequentially adding 335 mg to 345 mg of cadmium myristate, 1.5 mL to 2.5 mL of selenium precursor solution and 25 mL to 30 mL of 1-octadecene into a container, venting the air at 58 °C to 62 °C, and then heating up. When the temperature of the reaction solution reaches 192 °C to 194 °C, 78 mg to 82 mg of cadmium acetate is added to the reaction solution, and the temperature is further increased to 235 °C to 245 °C and held for 8 min to 12 min. Then, the solution is cooled to room temperature in an ice bath to terminate the reaction.
[0013] In an optional embodiment, the reaction product is washed with methanol and stored in n-hexane solvent.
[0014] In an optional embodiment, the preparation of high-performance core-shell colloidal quantum well nanocrystals includes: adding 7 mL to 9 mL of 1-octadecene to a container, venting the atmosphere at 58 °C to 62 °C, then raising the temperature to 295 °C to 305 °C and allowing it to stand in an inert environment; when the system temperature drops to 148 °C to 152 °C, injecting 0.1 mL to 0.2 mL of cadmium precursor solution and sulfur precursor solution into the reaction solution at a rate of 6.5 mL / h to 7.5 mL / h; subsequently, injecting a core-shell colloidal quantum well nanocrystal dispersion; then, injecting 2.5 mL to 2.8 mL of cadmium precursor solution and 2.5 mL to 2.8 mL of sulfur precursor solution at a rate of 6.5 mL / h to 7.5 mL / h; subsequently, injecting 0.8 mL to 1.2 mL of zinc precursor solution and 0.8 mL to 1.2 mL of sulfur precursor solution at a rate of 6.5 mL / h to 7.5 mL / h.
[0015] In an optional embodiment, annealing is performed at 280°C to 320°C for 15 to 25 minutes.
[0016] Secondly, the present invention provides a high-performance core-shell colloidal quantum well nanocrystal, which is prepared by any of the preparation methods described in the foregoing embodiments.
[0017] Thirdly, the present invention provides a colloidal nanocrystal self-assembled whispering-gallery mode laser, wherein the raw materials for preparing the colloidal nanocrystal self-assembled whispering-gallery mode laser include quartz optical fiber and the high-performance core-shell colloidal quantum well nanocrystals described in the aforementioned embodiments.
[0018] Fourthly, the present invention provides a method for fabricating a self-assembled whispering-gallery mode laser using colloidal nanocrystals as described in the foregoing embodiments, comprising the following steps: immersing a quartz optical fiber in a high-performance core-shell colloidal quantum well nanocrystal solution; through capillary effect, after the high-performance core-shell colloidal quantum well nanocrystal solution has fully wetted and filled the interior of the quartz optical fiber, placing the quartz optical fiber horizontally so that the nanocrystals inside the quartz optical fiber gradually gather at the end of the quartz optical fiber as the solvent evaporates, and self-assemble on the inner surface of the quartz optical fiber to form a ring-shaped distributed core-shell colloidal quantum well nanocrystal thin film, constituting a whispering-gallery optical microcavity structure.
[0019] The beneficial effects of this invention include: This invention provides a novel method for fabricating a self-assembled whispering-gallery mode laser from colloidal nanocrystals. This method is simple, easy to operate, and highly reproducible. It not only simplifies the fabrication process of core-shell colloidal quantum well nanocrystals, but also utilizes a fused silica capillary with low optical loss and a naturally circular structure as an optical microcavity to support the whispering-gallery mode. The capillary effect drives the spontaneous injection of the colloidal quantum well solution into the tube, and through solvent evaporation, a dense and flat gain film is formed on the inner wall through self-assembly. Ultimately, this achieves low threshold, high stability, and simple fabrication of CQW-WGM laser output. Attached Figure Description
[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a flowchart illustrating the preparation process of high-performance core-shell colloidal quantum well nanocrystals in this invention. Figure 2 This is a schematic diagram and physical image of the fabrication of the colloidal nanocrystal self-assembled whispering-gallery mode laser of the present invention; Figure 3 Optical microscope images of the WGM micro / nano laser at different pump powers in the application example; Figure 4 The graph shows the change in luminous intensity of the WGM micro / nano laser under different light intensities in the application example. The location of the sudden increase in intensity represents the emission threshold of the WGM laser. Figure 5 The output spectrum and resonant wavelength of the WGM micro / nano laser in the application example are simulated when the wavelength is above the laser threshold. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0023] The following provides a detailed description of the high-performance core-shell colloidal quantum well nanocrystals, the colloidal nanocrystal self-assembled whispering-gallery mode laser, and their fabrication methods provided by this invention.
[0024] This invention provides a method for preparing high-performance core-shell colloidal quantum well nanocrystals, such as... Figure 1 As shown, it includes the following steps: S0: Prepare the solutions of each precursor.
[0025] In some alternative embodiments, the selenium precursor solution is obtained by mixing selenium powder with 1-octadecene. Exemplarily, the ratio of selenium powder to 1-octadecene in the selenium precursor solution can be (94.5 mg to 95 mg):(7.5 mL to 8.5 mL).
[0026] In some optional embodiments, the cadmium precursor solution is obtained by heating a mixture of cadmium oleate and 1-octadecene. Exemplarily, the ratio of cadmium oleate to 1-octadecene in the cadmium precursor solution can be (0.35 mmol / L to 0.45 mmol / L):(1.5 mL to 2.5 mL). The heating temperature during the preparation of the cadmium precursor solution can be 68°C to 72°C, such as 68°C, 69°C, 70°C, 71°C, or 72°C, or other values within the range of 68°C to 72°C.
[0027] In some alternative embodiments, the sulfur precursor solution is obtained by mixing 1-octylthiol and 1-octadecene. Exemplarily, the ratio of 1-octylthiol to 1-octadecene in the sulfur precursor solution can be (80 μL~90 μL):(3.5 mL~4.5 mL).
[0028] In some optional embodiments, the zinc precursor solution is obtained by heating a mixture of zinc oleate, oleylamine, and 1-octadecene. Exemplarily, the ratio of zinc oleate, oleylamine, and 1-octadecene in the zinc precursor solution can be (0.12 mmol~0.15 mmol):(0.2 mL~0.3 mL):(0.4 mL~0.6 mL). The heating temperature during the preparation of the zinc precursor solution can be 68°C~72°C, such as 68°C, 69°C, 70°C, 71°C, or 72°C, or other values within the range of 68°C~72°C.
[0029] S1: Cadmium myristate was reacted with a selenium precursor solution and 1-octadecene, followed by the addition of cadmium acetate to continue the reaction, resulting in a nuclear colloidal quantum trap nanocrystal dispersion.
[0030] In some optional embodiments, 335 mg to 345 mg of cadmium myristate, 1.5 mL to 2.5 mL of selenium precursor solution, and 25 mL to 30 mL of 1-octadecene can be added sequentially to a container, and the mixture is vented at 58°C to 62°C (the venting time can be 25 min to 35 min). Then the temperature is increased, and when the temperature of the reaction solution reaches 192°C to 194°C, 78 mg to 82 mg of cadmium acetate is added to the reaction solution. The temperature is then increased to 235°C to 245°C and held for 8 min to 12 min. Finally, the mixture is cooled to room temperature in an ice bath to terminate the reaction.
[0031] Furthermore, the reaction product was washed with methanol and stored in hexane solvent. Before preparing the shell, the optical density of the solution was diluted to 20 by adding hexane solvent.
[0032] S2: Mix 1-octadecene, a portion of the cadmium precursor solution, and a portion of the sulfur precursor solution, then add a nuclear colloidal quantum well nanocrystal dispersion, followed by the addition of another portion of the cadmium precursor solution and a portion of the sulfur precursor solution to form a CdS buffer layer; subsequently, add a zinc precursor solution and a portion of the sulfur precursor solution to form CdS on the surface of the CdS buffer layer. 1-x Zn x An S alloy shell was then formed; subsequently, annealing and cooling were performed to obtain high-performance core-shell colloidal quantum well nanocrystals.
[0033] In some optional embodiments, 7 mL to 9 mL of 1-octadecene can be added to the container, and the atmosphere can be vented at 58°C to 62°C (venting time can be 25 min to 35 min). The temperature is then raised to 295°C to 305°C and allowed to stand in an inert environment (such as a nitrogen atmosphere). When the system temperature drops to 148°C to 152°C, 0.1 mL to 0.2 mL of cadmium precursor solution and sulfur precursor are injected into the reaction solution at a rate of 6.5 mL / h to 7.5 mL / h. The solution was first prepared; then, a colloidal quantum well nanocrystal dispersion was injected; subsequently, 2.5 mL to 2.8 mL of cadmium precursor solution and 2.5 mL to 2.8 mL of sulfur precursor solution were injected at a rate of 6.5 mL / h to 7.5 mL / h to form a CdS buffer layer; subsequently, 0.8 mL to 1.2 mL of zinc precursor solution and 0.8 mL to 1.2 mL of sulfur precursor solution were injected at a rate of 6.5 mL / h to 7.5 mL / h to form CdS buffer layer on the surface of the CdS buffer layer. 1-x Zn x S alloy shell.
[0034] In some alternative embodiments, annealing can be performed at 280°C to 320°C (e.g., 280°C, 290°C, 300°C, 310°C, or 320°C) for 15 min to 25 min (e.g., 15 min, 20 min, or 25 min).
[0035] Furthermore, the reaction product can be washed with methanol (the number of washing times can be, for example, 1 to 3 times) to obtain core-shell colloidal quantum well nanocrystal precipitate, which is then stored in n-hexane solvent for later use, so that the concentration of the high-performance core-shell colloidal quantum well nanocrystal solution is 10 mg / mL to 20 mg / mL.
[0036] It should be noted that the shell thickness can also be adjusted by controlling the concentration and quantity of the injected shell precursor, or Cd can be prepared on other nuclear colloidal nanocrystals. 1-x Zn x S alloy shell.
[0037] Accordingly, the present invention also provides a high-performance core-shell colloidal quantum well nanocrystal, which is prepared by the above-described preparation method.
[0038] Furthermore, this invention also provides a colloidal nanocrystal self-assembled whispering-gallery mode laser, which is fabricated using quartz optical fiber and the aforementioned high-performance core-shell colloidal quantum well nanocrystals. This colloidal nanocrystal self-assembled whispering-gallery mode laser exhibits a low threshold, high quality factor, and superior laser mode and performance.
[0039] Accordingly, the present invention also provides a method for preparing the above-mentioned colloidal nanocrystal self-assembled whispering-gallery mode laser, such as... Figure 2 As shown, for example, it may include the following steps: immersing a quartz optical fiber in a high-performance core-shell colloidal quantum well nanocrystal solution (e.g., Figure 2 In (a), through the capillary effect, after the high-performance core-shell colloidal quantum well nanocrystal solution has fully wetted and filled the interior of the quartz optical fiber (as shown in Figure (a)), Figure 2 In Figures (b) and (d), where (b) is a schematic diagram and (d) is a physical image, a quartz optical fiber is placed horizontally so that the nanocrystals inside the quartz optical fiber gradually gather at the end of the quartz optical fiber as the solvent evaporates, and self-assemble on the inner surface of the quartz optical fiber to form a ring-shaped core-shell colloidal quantum well nanocrystal thin film, constituting a whispering-gallery optical microcavity structure (e.g., Figure 2 (c) and (e), where (c) is a schematic diagram and (e) is a physical image.
[0040] In some alternative embodiments, the diameter of the quartz optical fiber can be 110μm to 120μm, and the length can be, for example, 0.8cm to 1.2cm.
[0041] By using a fused silica capillary with low optical loss and a naturally circular structure as an optical microcavity to support whispering-gallery mode, the capillary effect drives the spontaneous injection of colloidal quantum well solution into the tube. Through solvent evaporation, a dense and flat gain film is formed on the inner wall, ultimately achieving low threshold, high stability and simple fabrication of CQW-WGM laser output.
[0042] The whispering-gallery mode optical microcavity constructed using CQW material proposed in this invention has at least the following advantages over existing CQW-WGM lasers: Firstly, the solution provided by this invention improves the uniformity of the gain film and simplifies the material preparation process. Secondly, by leveraging the capillary effect, a high-performance CQW-WGM laser can be successfully fabricated through a simple process. This device allows for precise control of its WGM spectral characteristics at the micro- and nano-scale by adjusting parameters such as the size of the quartz capillary or the concentration of the CQW solution. This CQW-WGM laser has broad application prospects in fields such as micro- and nano-lasers and biodetection.
[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0044] Example 1 This embodiment provides a high-performance core-shell colloidal quantum well nanocrystal, the preparation method of which includes: S0: Preparation of precursor solution.
[0045] 94.75 mg of selenium powder was dissolved in 8 mL of 1-octadecene and sonicated for 20 min to obtain a selenium precursor solution. 0.4 mmol of cadmium oleate and 2 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 15 min, and heated to 70 °C under a nitrogen atmosphere to obtain a cadmium precursor solution. 84 μL of 1-octylthiol was dissolved in 4 mL of 1-octadecene to obtain a sulfur precursor solution. 0.14 mmol of zinc oleate, 0.25 mL of oleylamine, and 0.5 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 15 min, and heated to 70 °C under a nitrogen atmosphere to obtain a zinc precursor solution.
[0046] S1: Preparation of nuclear colloidal quantum well nanocrystal dispersion.
[0047] 340 mg of cadmium myristate, 2 mL of selenium precursor solution, and 28 mL of 1-octadecene were sequentially added to a three-necked flask. The mixture was vented at 60 °C for 30 min, then heated. When the reaction solution reached 193 °C, 80 mg of cadmium acetate was rapidly added. The temperature was further increased to 240 °C and maintained at this temperature for 10 min. The flask was then placed in an ice bath to cool to room temperature, terminating the reaction. The reaction product was washed twice with methanol and then stored in hexane for later use. Before preparing the shell, the optical density of the solution was diluted to 20 by adding hexane to obtain a core-colloidal quantum well nanocrystal dispersion.
[0048] S2: Preparation of high-performance core-shell colloidal quantum well nanocrystals.
[0049] 8 mL of 1-octadecene was added to a round-bottom three-necked flask, and the mixture was vented at 60 °C for 30 min. The temperature was then raised to 300 °C, and an inert environment was maintained under nitrogen protection. When the system temperature dropped to 150 °C, 0.15 mL of cadmium and sulfur precursor solutions were injected into the reaction solution at a rate of 7 mL / h. Subsequently, a nuclear colloidal quantum well nanocrystal dispersion was injected. Then, 2.6 mL of cadmium and sulfur precursor solutions were slowly injected at a rate of 7 mL / h to promote the growth of the CdS buffer shell. Finally, 1 mL of zinc and 1 mL of sulfur precursor solutions were injected at a rate of 7 mL / h to grow CdS on the outside of the CdS buffer layer. 1-x Zn x S-alloy shell. After all precursors were injected, the system was annealed at 300°C for 20 min, and then the flask was placed in an ice bath to cool to room temperature to terminate the reaction. The reaction product was washed twice with methanol to obtain core-shell colloidal quantum well nanocrystal precipitate, which was stored in n-hexane solvent for later use. The concentration of the high-performance core-shell colloidal quantum well nanocrystal solution was 20 mg / mL.
[0050] Example 2 This embodiment provides a high-performance core-shell colloidal quantum well nanocrystal, the preparation method of which includes: S0: Preparation of precursor solution.
[0051] 94.5 mg of selenium powder was dissolved in 7.5 mL of 1-octadecene and sonicated for 20 min to obtain a selenium precursor solution. 0.35 mmol of cadmium oleate and 1.5 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 12 min, and heated to 68 °C under a nitrogen atmosphere to obtain a cadmium precursor solution. 80 μL of 1-octylthiol was dissolved in 3.5 mL of 1-octadecene to obtain a sulfur precursor solution. 0.12 mmol of zinc oleate, 0.2 mL of oleylamine, and 0.4 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 12 min, and heated to 68 °C under a nitrogen atmosphere to obtain a zinc precursor solution.
[0052] S1: Preparation of nuclear colloidal quantum well nanocrystal dispersion.
[0053] 335 mg of cadmium myristate, 1.5 mL of selenium precursor solution, and 25 mL of 1-octadecene were sequentially added to a three-necked flask. The mixture was vented at 58 °C for 35 min, then heated. When the reaction solution reached 192 °C, 78 mg of cadmium acetate was rapidly added. The temperature was further increased to 235 °C and maintained at this temperature for 12 min. The flask was then placed in an ice bath to cool to room temperature, thus terminating the reaction. The reaction product was washed twice with methanol and then stored in hexane for later use. Before preparing the shell, the optical density of the solution was diluted to 20 by adding hexane to obtain a core-colloidal quantum well nanocrystal dispersion.
[0054] S2: Preparation of high-performance core-shell colloidal quantum well nanocrystals.
[0055] 7 mL of 1-octadecene was added to a round-bottom three-necked flask, and the mixture was vented at 58 °C for 35 min. The temperature was then raised to 295 °C, and an inert environment was maintained under nitrogen protection. When the system temperature dropped to 148 °C, 0.1 mL of cadmium precursor solution and sulfur precursor solution were injected into the reaction solution at a rate of 6.5 mL / h. Subsequently, a nuclear colloidal quantum well nanocrystal dispersion was injected. Then, 2.5 mL of cadmium precursor solution and 2.5 mL of sulfur precursor solution were slowly injected at a rate of 6.5 mL / h to promote the growth of the CdS buffer shell. Finally, 0.8 mL of zinc precursor solution and 0.8 mL of sulfur precursor solution were injected at a rate of 6.5 mL / h to grow CdS on the outside of the CdS buffer layer. 1-x Zn x S-alloy shell. After all precursors were injected, the system was annealed at 280°C for 25 min, and then the flask was placed in an ice bath to cool to room temperature to terminate the reaction. The reaction product was washed twice with methanol to obtain core-shell colloidal quantum well nanocrystal precipitate, which was stored in n-hexane solvent for later use. The concentration of the high-performance core-shell colloidal quantum well nanocrystal solution was 15 mg / mL.
[0056] Example 3 This embodiment provides a high-performance core-shell colloidal quantum well nanocrystal, the preparation method of which includes: S0: Preparation of precursor solution.
[0057] 95 mg of selenium powder was dissolved in 8.5 mL of 1-octadecene and sonicated for 20 min to obtain a selenium precursor solution. 0.45 mmol of cadmium oleate and 2.5 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 18 min, and heated to 72 °C under a nitrogen atmosphere to obtain a cadmium precursor solution. 90 μL of 1-octylthiol was dissolved in 4.5 mL of 1-octadecene to obtain a sulfur precursor solution. 0.15 mmol of zinc oleate, 0.3 mL of oleylamine, and 0.6 mL of 1-octadecene were mixed in a long-necked flask, the mixture was purged for 18 min, and heated to 72 °C under a nitrogen atmosphere to obtain a zinc precursor solution.
[0058] S1: Preparation of nuclear colloidal quantum well nanocrystal dispersion.
[0059] 345 mg of cadmium myristate, 2.5 mL of selenium precursor solution, and 30 mL of 1-octadecene were sequentially added to a three-necked flask. The mixture was vented at 62 °C for 25 min, then heated. When the reaction solution reached 194 °C, 82 mg of cadmium acetate was rapidly added. The temperature was further increased to 245 °C and maintained at this temperature for 8 min. The flask was then placed in an ice bath to cool to room temperature, thus terminating the reaction. The reaction product was washed twice with methanol and then stored in hexane for later use. Before preparing the shell, the optical density of the solution was diluted to 20 by adding hexane to obtain a core-colloidal quantum well nanocrystal dispersion.
[0060] S2: Preparation of high-performance core-shell colloidal quantum well nanocrystals.
[0061] Nine mL of 1-octadecene was added to a round-bottom three-necked flask, and the mixture was vented at 62 °C for 25 min. The temperature was then raised to 305 °C, and an inert environment was maintained under nitrogen protection. When the system temperature dropped to 152 °C, 0.2 mL of cadmium precursor solution and sulfur precursor solution were injected into the reaction solution at a rate of 7.5 mL / h. Subsequently, a nuclear colloidal quantum well nanocrystal dispersion was injected. Then, 2.8 mL of cadmium precursor solution and 2.8 mL of sulfur precursor solution were slowly injected at a rate of 7.5 mL / h to promote the growth of the CdS buffer shell. Finally, 1.2 mL of zinc precursor solution and 1.2 mL of sulfur precursor solution were injected at a rate of 7.5 mL / h to grow CdS on the outside of the CdS buffer layer. 1-x Zn x S alloy shell. After all precursors were injected, the system was annealed at 320°C for 15 min, and then the flask was placed in an ice bath to cool to room temperature to terminate the reaction. The reaction product was washed twice with methanol to obtain core-shell colloidal quantum well nanocrystal precipitate, which was stored in n-hexane solvent for later use. The concentration of the high-performance core-shell colloidal quantum well nanocrystal solution was 10 mg / mL.
[0062] Example 4 This embodiment provides a self-assembled whispering-gallery mode laser using colloidal nanocrystals. The preparation method includes: immersing a quartz optical fiber with a diameter of 115 μm and a length of 2 cm into the high-performance core-shell colloidal quantum well nanocrystal solution described in Example 1; after the high-performance core-shell colloidal quantum well nanocrystal solution has fully wetted and filled the interior of the quartz optical fiber, the quartz optical fiber is placed horizontally; as the solvent evaporates, the nanocrystals inside the fiber tube gradually gather at the top and self-assemble on the inner surface of the fiber to form a ring-shaped distributed core-shell colloidal quantum well nanocrystal thin film, constituting a whispering-gallery optical microcavity structure.
[0063] Application examples This application example provides a WGM micro / nano laser, which includes a 532 nanosecond laser as a light source and a colloidal nanocrystal self-assembled whispering-gallery mode laser provided in Example 4.
[0064] Excitation by a nanosecond laser (pulse width 1 ns, repetition frequency 60 Hz), Figure 3 Optical microscope images of the WGM micro / nano laser at different pump powers are shown.
[0065] Figure 3 In (a), the excitation state is below the laser threshold, where only weak spontaneous emission fluorescence is observed, and no laser is formed. When the pump power exceeds the laser threshold ( Figure 3 In Figure (b), a clear closed whispering-gallery mode optical path can be observed, which directly confirms that a stable WGM laser has been successfully generated. The smooth morphology of the inner surface of the fiber and the uniformity of the CQW distribution in the WGM micro / nano laser effectively suppress the scattering loss of optical resonance, allowing the internal circulating light to oscillate and amplify continuously with the least possible loss, ultimately leading to the generation of laser behavior.
[0066] Figure 4 The curve showing the relationship between the integrated fluorescence intensity of the WGM micro / nano laser and the excitation energy is presented. Figure 4 As shown, the fluorescence integral intensity exhibits a nonlinear sharp increase at a specific energy point. Through linear fitting, the excitation energy corresponding to the intersection of the two fitted lines is the laser threshold, calculated to be 0.94 mJ / cm². 2 This value is significantly lower than the typical threshold (tens of mJ / cm) of conventional WGM lasers, which directly proves that the WGM micro / nano lasers prepared in this invention have low optical loss, and also reflects the good uniformity of the self-assembled CQW thin film.
[0067] Figure 5Simulation results of the output spectrum and resonant wavelength above the lasing threshold of the 115 μm diameter WGM micro / nano laser provided in Example 4 are presented. The quality factor (Q factor) of the microcavity is a key parameter for measuring its optical confinement capability; a higher Q factor generally means a narrower laser linewidth and a lower lasing threshold. According to the formula Q = ... λ / FWMH Calculations show that the Q factor of this laser is approximately 4791, which is significantly higher than that of conventional WGM micro / nano lasers (which are typically only a few hundred).
[0068] Furthermore, according to WGM resonance theory formula 2 πn R= mλ , Figure 5 The figure above shows the distribution of theoretical resonant wavelengths for the corresponding diameter. The simulation results are in excellent agreement with the experimental data, strongly confirming the whispering-gallery mode nature of this laser.
[0069] In summary, the method for fabricating a self-assembled whispering-gallery mode (WGM) laser using colloidal nanocrystals provided by this invention is simple and easy to operate. This method not only simplifies the fabrication process of core-shell colloidal quantum well (CQW) nanocrystals but also enables the self-assembly of CQWs on the inner surface of an optical fiber to form a ring-shaped WGM micro / nano laser through capillary effects. The resulting WGM micro / nano laser exhibits excellent performance and, compared to existing WGM micro / nano lasers, has a lower laser threshold, lower cost, and is easier to operate.
[0070] The applicant declares that the above embodiments are merely illustrative examples of the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the core design spirit and principles of the present invention, any substitutions, modifications, or variations made by those skilled in the art to the solutions, such as selecting quartz optical fibers of different sizes, using other high-performance colloidal nanocrystals, organic dye molecules, or perovskite solutions as gain media, or utilizing capillary effects to introduce other types of gain media solutions, should all be covered within the scope of protection claimed by this patent.
Claims
1. A method for preparing high-performance core-shell colloidal quantum well nanocrystals, characterized in that, Includes the following steps: Cadmium myristate was reacted with a selenium precursor solution and 1-octadecene, followed by the addition of cadmium acetate to continue the reaction, resulting in a nuclear colloidal quantum trap nanocrystal dispersion. A mixture of 1-octadecene, a portion of cadmium precursor solution, and a portion of sulfur precursor solution was mixed, followed by the addition of the nuclear colloidal quantum well nanocrystal dispersion, and then further addition of a portion of cadmium precursor solution and a portion of sulfur precursor solution to form a CdS buffer layer; subsequently, a zinc precursor solution and a portion of sulfur precursor solution were added to form CdS on the surface of the CdS buffer layer. 1-x Zn x S alloy shell; then annealing and cooling to obtain high-performance core-shell colloidal quantum well nanocrystals; The selenium precursor solution is obtained by mixing selenium powder with 1-octadecene; the cadmium precursor solution is obtained by heating a mixture of cadmium oleate and 1-octadecene; the sulfur precursor solution is obtained by mixing 1-octylthiol and 1-octadecene; and the zinc precursor solution is obtained by heating a mixture of zinc oleate, oleylamine, and 1-octadecene.
2. The preparation method according to claim 1, characterized in that, The heating temperature during the preparation of the cadmium precursor solution is 68℃~72℃; And / or, in the cadmium precursor solution, the ratio of cadmium oleate to 1-octadecene is (0.35 mmol / L to 0.45 mmol / L): (1.5 mL to 2.5 mL).
3. The preparation method according to claim 1, characterized in that, The heating temperature during the preparation of the zinc precursor solution is 68℃~72℃; And / or, in the zinc precursor solution, the ratio of zinc oleate, oleylamine and 1-octadecene is (0.12 mmol~0.15 mmol):(0.2 mL~0.3 mL):(0.4 mL~0.6 mL).
4. The preparation method according to claim 1, characterized in that, In the sulfur precursor solution, the ratio of 1-octylthiol to 1-octadecene is (80 μL~90 μL):(3.5 mL~4.5 mL); And / or, in the selenium precursor solution, the ratio of selenium powder to 1-octadecene is (94.5 mg~95 mg):(7.5 mL~8.5 mL).
5. The preparation method according to claim 1, characterized in that, The preparation of the nuclear colloidal quantum well nanocrystal dispersion includes: adding 335 mg to 345 mg of cadmium myristate, 1.5 mL to 2.5 mL of the selenium precursor solution and 25 mL to 30 mL of 1-octadecene sequentially into a container, venting the air at 58 °C to 62 °C, and then heating up. When the temperature of the reaction solution reaches 192 °C to 194 °C, 78 mg to 82 mg of cadmium acetate is added to the reaction solution, and the temperature is further increased to 235 °C to 245 °C and held for 8 min to 12 min. Then, the solution is cooled to room temperature in an ice bath to terminate the reaction. Preferably, the reaction product is washed with methanol and stored in n-hexane solvent.
6. The preparation method according to claim 1, characterized in that, The preparation of the high-performance core-shell colloidal quantum well nanocrystals includes: adding 7 mL to 9 mL of 1-octadecene to a container, venting the gas at 58 °C to 62 °C, then raising the temperature to 295 °C to 305 °C and allowing it to stand in an inert environment; when the system temperature drops to 148 °C to 152 °C, injecting 0.1 mL to 0.2 mL of cadmium precursor solution and sulfur precursor solution into the reaction solution at a rate of 6.5 mL / h to 7.5 mL / h; then injecting the core-shell colloidal quantum well nanocrystal dispersion; subsequently, injecting 2.5 mL to 2.8 mL of cadmium precursor solution and 2.5 mL to 2.8 mL of sulfur precursor solution at a rate of 6.5 mL / h to 7.5 mL / h; then, injecting 0.8 mL to 1.2 mL of zinc precursor solution and 0.8 mL to 1.2 mL of sulfur precursor solution at a rate of 6.5 mL / h to 7.5 mL / h.
7. The preparation method according to claim 1, characterized in that, Annealing was performed at 280℃~320℃ for 15min~25min.
8. A high-performance core-shell colloidal quantum well nanocrystal, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.
9. A colloidal nanocrystal self-assembled whispering-gallery mode laser, characterized in that, The raw materials for preparing the colloidal nanocrystal self-assembled whispering-gallery mode laser include quartz optical fiber and the high-performance core-shell colloidal quantum well nanocrystals as described in claim 8.
10. A method for fabricating a colloidal nanocrystal self-assembled whispering-gallery mode laser as described in claim 9, characterized in that, Includes the following steps: Quartz optical fiber is immersed in a high-performance core-shell colloidal quantum well nanocrystal solution. Through capillary effect, after the high-performance core-shell colloidal quantum well nanocrystal solution has fully wetted and filled the interior of the quartz optical fiber, the quartz optical fiber is placed horizontally so that the nanocrystals inside the quartz optical fiber gradually gather at the end of the quartz optical fiber as the solvent evaporates, and self-assemble on the inner surface of the quartz optical fiber to form a ring-shaped distributed core-shell colloidal quantum well nanocrystal thin film, thus forming a whispering-gallery optical microcavity structure.