Chiral carbon quantum dots for optical limiting and preparation method thereof

Abstract

The present invention discloses a method for preparing chiral carbon quantum dots for optical limiting, comprising the following steps: Step 1, preparing chiral carbon quantum dots containing N and S; Step 2, purifying the chiral carbon quantum dots prepared in Step 1 by dialysis membrane to remove unreacted substances. The present invention also discloses chiral carbon quantum dots for optical limiting, which utilize atomic doping and chirality control to reduce the band gap and enhance optical limiting performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonlinear optics, relates to a method for preparing chiral carbon quantum dots for optical limiting, and further relates to chiral carbon quantum dots for optical limiting. Background Art

[0002] Since the development of laser technology, the powerful energy of lasers has brought convenience to people's lives, but it has also caused damage to the eyes and skin. In addition, lasers may cause irreparable damage to precision equipment. Therefore, based on the protection of the human body and some photodiodes, it is necessary to prepare an optical limiting material with ultrafast response and physical and chemical stability. In addition, this material has become a key development direction of the optoelectronics industry and is of great significance for resisting high-power ultrafast lasers. Up to now, the preparation process of some materials for linear optical limiting is relatively heavy and the preparation process is relatively complicated. Therefore, the development of an optical limiting material with a simple preparation process and non-toxic, green and environmentally friendly has become the key. In addition, optical limiting materials require a faster response time and stable physical and chemical properties. Chirality is introduced into carbon quantum dots, which exhibit excellent photophysical properties. Chirality is used to adjust the optical limiting properties of CQD. L / D-cysteine ​​is used as a precursor to prepare L / D-CysCQD. N and S elements are related to sp 2 The carbon core formed by the hybrid carbon bonding has a structure similar to D-π-A, which enhances the electron transport ability, reduces the band gap, and improves the optical limiting performance. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing chiral carbon quantum dots for optical limiting, which utilizes atomic doping and chirality regulation to reduce the band gap and enhance the optical limiting performance.

[0004] Another object of the present invention is chiral carbon quantum dots for optical limiting.

[0005] The first technical solution adopted by the present invention is a method for preparing chiral carbon quantum dots for optical limiting, which specifically includes the following steps:

[0006] Step 1, preparation of chiral carbon quantum dots containing N, S;

[0007] Step 2: purify through a dialysis membrane to remove unreacted substances in the N, S-containing chiral carbon quantum dots prepared in step 1.

[0008] The first technical solution of the present invention is also characterized in that:

[0009] The specific process of step 1 is:

[0010] In step 1.1, dissolve 1-3 g of chiral cysteine ​​and an equal amount of citric acid in 20-60 mL of deionized water and stir for 10-30 min until completely dissolved.

[0011] Step 1.2, transfer the solution obtained in step 1.1 to a high-pressure reactor and react at 120-180°C for 60-120 minutes. After the reaction is completed, cool to room temperature, remove impurities, and then remove a large amount of water solvent by rotary evaporation to obtain a gel-like substance, thereby obtaining chiral carbon quantum dots containing N, S.

[0012] In step 1.2, the specific process of impurity removal is: the post-reaction solution is passed through a 0.22 μm water-based microporous filter membrane to remove large particles.

[0013] The specific process of step 2 is as follows: dichloromethane is added to the reaction bottle, and oil-soluble impurities are removed by ultrasound. The above process is repeated three to four times, and the precipitate after removing the impurities is collected. The precipitate is then dispersed in 5 mL of water, and then the solution is stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution is collected and freeze-dried to form a yellow-brown powder to obtain the product.

[0014] In step 2, the amount of dichloromethane used is 5-20 mL.

[0015] In step 2, the ultrasonication time is 5 to 10 minutes.

[0016] In step 2, the freeze-drying time is 24-48 hours.

[0017] The second technical solution adopted by the present invention is that the chiral carbon quantum dots for optical limiting are prepared by the above-mentioned method for preparing chiral carbon quantum dots for optical limiting.

[0018] The beneficial effects of the present invention are that the present invention uses chiral amino acids as a doping source to improve the optical limiting performance of the material; in addition, the chiral source can further enhance its optical limiting performance. The preparation of the present invention is relatively simple and takes a short time. All preparation raw materials are cheap and readily available, and the resulting product is green, environmentally friendly, non-toxic, and suitable for use in the human body and devices. The use of atomic doping and chirality regulation to reduce the band gap enhances the optical limiting performance. Compared with the preparation of other optical limiting materials, the preparation is more environmentally friendly, low-cost, has good water solubility, and has good thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a band gap energy diagram of L-CysCQD and D-CysCQD prepared in Examples 1 and 2 of the method for preparing chiral carbon quantum dots for optical limiting of the present invention;

[0020] Figure 2 (a) shows the light limiting transmittance with a linear transmittance of 80%;

[0021] Figure 2(b) shows the light limiting transmittance with a linear transmittance of 65%;

[0022] Figure 2 (c) shows the light limiting transmittance when the linear transmittance is 50%;

[0023] Figure 3 UV absorption spectra of L-CysCQD prepared under the conditions of Comparative Example 1, Example 1, Example 3, and Example 5;

[0024] Figure 4 (a) shows the temperature change error bars of L-CysCQD before and after laser irradiation for 2 h;

[0025] Figure 4 (b) shows the change in the optical limiting performance of L-CysCQD after 2 h of laser irradiation;

[0026] Figure 5 This is a comparison chart of the transmittance of L-CysCQDs prepared in Example 1, Example 3, and Example 5. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The method for preparing chiral carbon quantum dots for optical limiting of the present invention specifically comprises the following steps:

[0029] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0030] Dissolve 1-3 g of chiral cysteine ​​(including L-Cys and D-Cys) and an equal amount of citric acid in 20-60 mL of deionized water and stir for 10-30 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and react at 120-180°C for 60-120 minutes. After the reaction is complete, cool to room temperature and filter the solution through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, remove the bulk of the aqueous solvent using a rotary evaporator to yield a gel-like substance, which is the N,S-containing chiral carbon quantum dots.

[0031] Step 2, purification of chiral carbon quantum dots: remove unreacted substances from the N, S-containing chiral carbon quantum dots prepared in step 1 and purify them through a dialysis membrane. Specifically:

[0032] 5-20 mL of dichloromethane was added to the reaction flask containing the N,S chiral carbon quantum dots prepared in step 1. Oil-soluble impurities were removed by ultrasonication for 5-10 minutes. This process was repeated three to four times. The impurity-free precipitate was collected and then dispersed in 5 mL of water. The solution was then stored for four days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. The solution was then collected and freeze-dried for 24-48 hours to form a yellow-brown powder, the product (L-CysCQD, D-CysCQD).

[0033] The concentration of the chiral carbon quantum dot solution is prepared as follows:

[0034] A solution of L / D-CysCQD with a concentration of 0.5 mg / mL to 2 mg / mL was prepared with deionized water until the linear transmittance of the solution was 50% to 80%.

[0035] Example 1

[0036] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0037] Take 1 g of L-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 120°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0038] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities removal was collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product L-CysCQD.

[0039] Example 2

[0040] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0041] Take 1 g of D-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 120°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0042] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product D-CysCQD.

[0043] Example 3

[0044] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0045] Take 1 g of L-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 150°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0046] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities removal was collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product L-CysCQD.

[0047] Example 4

[0048] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0049] Take 1 g of D-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 150°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0050] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product D-CysCQD.

[0051] Example 5

[0052] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0053] Take 1 g of L-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 180°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0054] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities removal was collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product L-CysCQD.

[0055] L-CysCQD aqueous solutions with linear transmittances of 80% (0.5 mg / mL), 65% (1.25 mg / mL), and 50% (2 mg / mL) were prepared using deionized water.

[0056] Example 6

[0057] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0058] Take 1 g of D-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 180°C for 90 minutes. After the reaction is completed and cooled to room temperature, the reaction solution is passed through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the large amount of aqueous solvent is removed using a rotary evaporator to obtain a gel-like substance.

[0059] In step 2, 5 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 5 minutes. This process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, the product D-CysCQD.

[0060] Deionized water was used to prepare D-CysCQD aqueous solutions with linear transmittances of 80% (0.5 mg / mL), 65% (1.25 mg / mL), and 50% (2 mg / mL).

[0061] Comparative Example 1 (In steps 1 and 2, the chiral carbon quantum dots of the doping source were not completely carbonized at 90°C, resulting in poor optical limiting effect)

[0062] Take 1 g of L-Cys and 1 g of citric acid and add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to an autoclave and place it at 90°C for 90 minutes. After the reaction is completed, cool to room temperature and pass the reaction solution through a 0.22 μm water-based microporous filter to remove large particles. Subsequently, remove the bulk of the aqueous solvent using a rotary evaporator to obtain a gel-like substance.

[0063] The chiral carbon quantum dots were freed of unreacted substances and purified by dialysis membrane. 10 mL of dichloromethane was introduced into the reaction flask, and oil-soluble impurities were removed by ultrasound for 10 min. The above process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, namely L-CysCQD.

[0064] Example 7

[0065] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0066] Dissolve 3 g of L-Cys and an equal amount of citric acid in 60 mL of deionized water and stir for 10 minutes until completely dissolved. The entire solution is then transferred to an autoclave and reacted at 120°C for 60 minutes. After the reaction is complete and cooled to room temperature, the solution is filtered through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the aqueous solvent is removed using a rotary evaporator to yield a gel-like substance, which is the N,S-containing chiral carbon quantum dots.

[0067] In step 2, 20 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 10 minutes. This process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 24 hours to form a yellow-brown powder, the product L-CysCQD.

[0068] Example 8

[0069] Step 1, preparation of chiral carbon quantum dots containing N, S, specifically:

[0070] Dissolve 2 g of L-Cys and an equal amount of citric acid in 40 mL of deionized water and stir for 30 minutes until completely dissolved. The entire solution is then transferred to an autoclave and reacted at 120°C for 120 minutes. After the reaction is complete and cooled to room temperature, the solution is filtered through a 0.22 μm aqueous microporous filter to remove large particles. Subsequently, the aqueous solvent is removed using a rotary evaporator to yield a gel-like substance, which is the N,S-containing chiral carbon quantum dots.

[0071] In step 2, 10 mL of dichloromethane was added to the reaction flask, and oil-soluble impurities were removed by ultrasonication for 8 minutes. This process was repeated three to four times. The precipitate after impurities were collected and then dispersed in 5 mL of water. The solution was then stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa. Subsequently, the solution was collected and freeze-dried for 36 hours to form a yellow-brown powder, the product L-CysCQD.

[0072] Figure 1 Band gap energy diagrams of L-CysCQD and D-CysCQD prepared in Examples 1 and 2 of the present invention's method for preparing chiral carbon quantum dots for optical limiting. Ultraviolet spectroscopy was used to measure the band gap width, revealing that the band gap of the D-isomer is smaller than that of the L-isomer. This reduction in band gap provides a foundation for enhancing electron transfer and improving optical limiting performance.

[0073] Figures 2(a) to 2(c) show the transmittance of L-CysCQD and D-CysCQD prepared in Examples 5 and 6. Figure 2(a) shows the linear transmittance when the linear transmittance is 80%. When the linear transmittance is 80%, the nonlinear transmittance of L-CysCQD is 95.47%, and the nonlinear transmittance of D-CysCQD is 93.94%.

[0074] Figure 2 (b) shows the optical limiting transmittance with a linear transmittance of 65%. The nonlinear transmittances of L-CysCQD are 59.12% and 52.76% for D-CysCQD.

[0075] Figure 2 (c) shows the optical limiting transmittance with a linear transmittance of 50%; the nonlinear transmittance of L-CysCQD is 55.60%, and the nonlinear transmittance of D-CysCQD is 42.65%;

[0076] Figures 2(a) to 2(c) demonstrate that, under identical preparation conditions and solution concentrations, the optical limiting performance of D-CysCQDs is superior to that of L-CysCQDs. Furthermore, the optical limiting performance increases with increasing concentration.

[0077] Figure 3 The UV absorption spectra of L-CysCQDs prepared under the conditions of Comparative Example 1, Example 1, Example 3, and Example 5 show no absorption peak at 300-400 nm at 90°C, indicating no carbonization. Under reaction conditions of 120-180°C, the absorption peak at 300-400 nm increases with increasing temperature, demonstrating that carbonization increases with increasing temperature.

[0078] Figure 4(a) shows the temperature change error bars of L-CysCQD before and after 2 hours of laser irradiation. Since laser irradiation generates heat energy, a thermal imaging instrument was used to characterize the temperature change of the chiral carbon quantum dots prepared in this invention to investigate whether they can be applied to instruments or the human body under laser irradiation. After 2 hours of laser irradiation, the temperature change of the material was measured using an infrared imager. To visualize the data, error bars are used. This demonstrates that under 2 hours of laser irradiation, the temperature change is minimal and the product is stable.

[0079] Figure 4(b) shows the change in the optical limiting performance of L-CysCQDs after 2 hours of laser irradiation, comparing the performance before and after laser irradiation. Figure 4(b) shows that the optical limiting performance of L-CysCQDs remains essentially unchanged after irradiation. This demonstrates that these chiral carbon quantum dots can maintain a relatively stable temperature under laser irradiation, potentially opening the possibility of incorporating optical limiting materials into wearable devices and instruments.

[0080] Figure 5 The L-CysCQDs prepared in Example 1, Example 3, and Example 5 were compared to find that their optical limiting performance increased with increasing temperature.

Claims

1. Application of chiral carbon quantum dots as optical limiting materials, characterized by: The preparation method of chiral carbon quantum dots specifically comprises the following steps: Step 1, preparation of chiral carbon quantum dots containing N, S; The specific process of step 1 is: In step 1.1, dissolve 1-3 g of chiral cysteine ​​and an equal amount of citric acid in 20-60 mL of deionized water and stir for 10-30 min until completely dissolved. Step 1.2, transferring the solution obtained in step 1.1 to a high-pressure reactor, reacting at 120-180° C. for 60-120 minutes, cooling to room temperature, removing impurities, and then removing a large amount of water solvent by rotary evaporation to obtain a gel-like substance, namely, obtaining chiral carbon quantum dots containing N, S; Step 2: purify through a dialysis membrane to remove unreacted substances in the N, S-containing chiral carbon quantum dots prepared in step 1.

2. The use of chiral carbon quantum dots as an optical limiting material according to claim 1, characterized in that: In step 1.2, the specific process of impurity removal is: passing the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles.

3. The use of chiral carbon quantum dots as an optical limiting material according to claim 1, characterized in that: The specific process of step 2 is as follows: adding dichloromethane to the reaction bottle, removing oil-soluble impurities by ultrasound, repeating the above process three to four times, collecting the precipitate after removing the impurities, and then dispersing the precipitate in 5 mL of water, and then storing the solution for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, collecting the solution and freeze-drying it to form a yellow-brown powder to obtain the product.

4. The use of chiral carbon quantum dots as an optical limiting material according to claim 3, characterized in that: In step 2, the amount of dichloromethane used is 5-20 mL.

5. The use of chiral carbon quantum dots as an optical limiting material according to claim 3, characterized in that: In step 2, the ultrasonication time is 5 to 10 minutes.

6. The use of chiral carbon quantum dots as an optical limiting material according to claim 3, characterized in that: In step 2, the freeze-drying time is 24-48 hours.

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