Chiral carbon quantum dot for optical limiting and preparation method thereof

Abstract

The invention discloses a preparation method of chiral carbon quantum dots for optical limiting. The preparation method specifically comprises the following steps: step 1, preparing N and S-containing chiral carbon quantum dots; and 2, purifying through a dialysis membrane, and removing unreacted substances in the chiral carbon quantum dots containing N and S prepared in the step 1 to obtain the chiral carbon quantum dots containing N and S. The invention also discloses a chiral carbon quantum dot for optical limiting, the band gap is reduced by using atom doping and chiral regulation, and the optical limiting performance is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of nonlinear optics, and relates to a method for preparing chiral carbon quantum dots for optical limiting. The invention also 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 ultrafast response and physically and chemically stable optical limiting material. 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, it is key to develop an optical limiting material with a simple preparation process and non-toxic, green and environmentally friendly. In addition, the optical limiting material requires a faster response time and stable physical and chemical properties. The chirality is introduced into carbon quantum dots, which show excellent photophysical properties. Chirality is used to adjust the optical limiting properties of CQD. L / D-cysteine ​​was used as a precursor to prepare L / D-CysCQD. N and S elements are related to sp 2 The carbon core formed by the combination of hybrid carbons has a structure similar to D-π-A. This enhances the electron transport capability, 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 photolimiting.

[0005] The first technical solution adopted by the present invention is a method for preparing chiral carbon quantum dots for optical limiting, which specifically comprises the following steps: Step 1, preparation of chiral carbon quantum dots containing N and S; Step 2, purifying through a dialysis membrane to remove unreacted substances in the N, S-containing chiral carbon quantum dots prepared in step 1, to obtain.

[0006] The first technical solution of the present invention is also characterized in that: The specific process of step 1 is: 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, transfer the solution obtained in step 1.1 to a high-pressure reactor, react at 120-180°C for 60-120 minutes, and after the reaction is completed, cool to room temperature, remove impurities, and then remove a large amount of water solvent by a rotary evaporator to obtain a gel-like substance, that is, chiral carbon quantum dots containing N, S.

[0007] In step 1.2, the specific process of impurity removal is: the solution after the reaction is passed through a 0.22 μm water system microporous filter membrane to remove large particles.

[0008] The specific process of step 2 is: 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 using a dialysis membrane with a molecular weight cutoff of 0.5 kDa to store the solution for 4 days; then, collecting the solution and freeze-drying it to form a yellow-brown powder to obtain the product.

[0009] In step 2, the amount of dichloromethane used is 5-20 mL.

[0010] In step 2, the ultrasonic time is 5 to 10 minutes.

[0011] In step 2, the freeze-drying time is 24-48 hours.

[0012] 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 preparation method of the chiral carbon quantum dots for optical limiting.

[0013] The beneficial effect of the present invention is that the present invention uses chiral amino acids as doping sources 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 easily available, and the resulting products are green, environmentally friendly and non-toxic, and can be applied to the human body and devices. The band gap is reduced by atomic doping and chiral regulation, and the optical limiting performance is enhanced. Compared with the preparation of other optical limiting materials, it is more green and environmentally friendly, low in price, has good water solubility, and has good thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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; Figure 2 (a) shows the light limiting transmittance with a linear transmittance of 80%; Figure 2 (b) shows the light limiting transmittance with a linear transmittance of 65%; Figure 2 (c) shows the light limiting transmittance when the linear transmittance is 50%; Figure 3The UV absorption spectrum of L-CysCQD prepared under the conditions of Comparative Example 1, Example 1, Example 3, and Example 5; Figure 4 (a) shows the temperature variation error bars of L-CysCQD before and after laser irradiation for 2 h; Figure 4 (b) is a graph showing the optical limiting performance changes of L-CysCQD after 2 h of laser irradiation; Figure 5 This is a comparison chart of the transmittance of L-CysCQDs prepared in Example 1, Example 3, and Example 5. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The method for preparing chiral carbon quantum dots for optical limiting of the present invention specifically comprises the following steps: Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1-3 g of chiral cysteine ​​(including L-Cys and D-Cys) and an equal amount of citric acid and dissolve them in 20-60 mL of deionized water. Stir under a stirrer for 10-30 min until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and react at 120-180°C for 60-120 min. After the reaction is completed, wait for it to cool to room temperature, pass the reacted solution through a 0.22μm water-based microporous filter membrane to remove large particles, and then remove a large amount of water solvent through a rotary evaporator to obtain a gel-like substance, which is the chiral carbon quantum dots containing N, S.

[0017] Step 2, purification of chiral carbon quantum dots: remove the unreacted substances in the chiral carbon quantum dots containing N and S prepared in step 1, and purify them through a dialysis membrane. Specifically: 5-20 mL of dichloromethane was added to the reaction bottle containing N, S chiral carbon quantum dots prepared in step 1, and oil-soluble impurities were removed by ultrasound for 5-10 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 24-48 hours to form a yellow-brown powder, and the product (L-CysCQD, D-CysCQD) was obtained.

[0018] The concentration of the chiral carbon quantum dot solution is prepared as follows: 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%.

[0019] Example 1 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of L-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 120°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0020] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product L-CysCQD was obtained.

[0021] Example 2 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of D-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 120°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0022] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product D-CysCQD was obtained.

[0023] Example 3 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of L-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 150°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0024] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product L-CysCQD was obtained.

[0025] Example 4 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of D-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 150°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0026] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product D-CysCQD was obtained.

[0027] Example 5 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of L-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 180°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0028] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product L-CysCQD was obtained.

[0029] Deionized water was used to prepare L-CysCQD aqueous solutions with linear transmittances of 80% (0.5 mg / mL), 65% (1.25 mg / mL), and 50% (2 mg / mL).

[0030] Example 6 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 1 g of D-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 180°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0031] Step 2, 5 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 5 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 48 hours to form a yellow-brown powder, and the product D-CysCQD was obtained.

[0032] 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).

[0033] Comparative Example 1 (In steps 1 and 2, the chiral carbon quantum dots of the doping source were not completely carbonized at 90°C, and the optical limiting effect was poor) Take 1 g of L-Cys and 1 g of citric acid, and then add them to 20 mL of deionized water. Stir under a stirrer for 20 minutes until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and place it at 90°C for 90 minutes. After the reaction is completed, wait for it to cool to room temperature, and pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles. Subsequently, a large amount of water solvent is removed by a rotary evaporator to obtain a gel-like substance.

[0034] The above chiral carbon quantum dots were purified by dialysis membrane after removing unreacted substances. 10 mL of dichloromethane was introduced into the reaction bottle, and oil-soluble impurities were removed by ultrasound for 10 min. The above process was repeated three to four times. The precipitate from which impurities were removed 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, namely L-CysCQD.

[0035] Example 7 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 3 g of L-Cys and an equal amount of citric acid and dissolve them in 60 mL of deionized water. Stir for 10 min under a stirrer until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and react at 120 ° C for 60 min. After the reaction is completed, wait for it to cool to room temperature, pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles, and then remove a large amount of water solvent through a rotary evaporator to obtain a gel-like substance, which is the chiral carbon quantum dots containing N, S.

[0036] Step 2, 20 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 10 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 24 hours to form a yellow-brown powder, and the product L-CysCQD was obtained.

[0037] Example 8 Step 1, preparation of chiral carbon quantum dots containing N, S, specifically: Take 2 g of L-Cys and an equal amount of citric acid and dissolve them in 40 mL of deionized water. Stir for 30 min under a stirrer until completely dissolved. Then, transfer the entire solution to a high-pressure reactor and react at 120 ° C for 120 min. After the reaction is completed, wait for it to cool to room temperature, pass the reacted solution through a 0.22 μm water-based microporous filter membrane to remove large particles, and then remove a large amount of water solvent through a rotary evaporator to obtain a gel-like substance, which is the chiral carbon quantum dots containing N, S.

[0038] Step 2, 10 mL of dichloromethane was added to the reaction bottle, and the oil-soluble impurities were removed by ultrasound for 8 min. The above process was repeated three to four times. The precipitate with impurities removed was collected, and then the precipitate was dispersed in 5 mL of water, and then the solution was stored for 4 days using a dialysis membrane with a molecular weight cutoff of 0.5 kDa; then, the solution was collected and freeze-dried for 36 hours to form a yellow-brown powder, and the product L-CysCQD was obtained.

[0039] Figure 1 The band gap energy diagrams 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; the width of the band gap was tested by ultraviolet spectroscopy, and it was observed that among the L-type and D-type isomers, the band gap of the entire D-type isomer is smaller than the band gap of the L-type isomer. Reducing the band gap provides a basis for enhancing electron transfer and improving optical limiting performance; Figure 2 (a) to Figure 2 (c) are the transmittances of L-CysCQD and D-CysCQD prepared in Example 5 and Example 6. Figure 2 (a) is 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%. 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. 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%; Figures 2 (a) to 2 (c) show that under the same preparation conditions and solution concentration, the optical limiting performance of D-CysCQD is better than that of L-CysCQD. In addition, as the control concentration increases, the optical limiting performance also gradually increases.

[0040] Figure 3 The L-CysCQD prepared under the conditions of Comparative Example 1, Example 1, Example 3, and Example 5 has no absorption peak at 300-400 nm at 90°C in the UV absorption spectrum, proving that it is not carbonized. Under the reaction conditions of 120-180°C, as the temperature increases, the absorption peak at 300-400 nm increases, proving that the degree of carbonization increases with increasing temperature.

[0041] 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, in order to study whether the chiral carbon quantum dots prepared by the present invention can be applied to instruments or the human body under laser irradiation, a thermal imaging instrument is used to characterize their temperature changes. After 2 hours of laser irradiation, the temperature change of the material for 2 hours was measured using an infrared imager. In order to visualize the data, error bars are used to present it. It is proved that under 2 hours of laser irradiation, the temperature change is small and the product is stable; Figure 4 (b) is a graph showing the change in the optical limiting performance of L-CysCQD after laser irradiation for 2 hours, comparing before and after laser irradiation. From Figure 4 (b), we can conclude that the optical limiting of L-CysCQD has basically not changed after irradiation. This proves that this chiral carbon quantum dot can maintain a relatively stable temperature state under laser irradiation, which provides the possibility of introducing optical limiting materials into human wearable devices and instruments.

[0042] Figure 5 It is the L-CysCQD prepared in Example 1, Example 3, and Example 5. Through comparison, it is found that as the temperature increases, the optical limiting performance thereof is enhanced.

Claims

1. A method for preparing chiral carbon quantum dots for optical limiting, characterized in that: The specific steps include: Step 1, preparation of chiral carbon quantum dots containing N and S; Step 2, purifying through a dialysis membrane to remove unreacted substances in the N, S-containing chiral carbon quantum dots prepared in step 1, to obtain.

2. The method for preparing chiral carbon quantum dots for optical limiting according to claim 1, characterized in that: The specific process of step 1 is as follows: 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, transfer the solution obtained in step 1.1 to a reactor, react at 120-180°C for 60-120 min, and after the reaction is completed, cool to room temperature, remove impurities, and then remove a large amount of water solvent by rotary evaporator to obtain a gel-like substance, that is, chiral carbon quantum dots containing N, S.

3. The method for preparing chiral carbon quantum dots for optical limiting according to claim 2, characterized in that: In the step 1.2, the specific process of removing impurities is: passing the solution after the reaction through a 0.22 μm water system microporous filter membrane to remove large particles.

4. The method for preparing chiral carbon quantum dots for optical limiting according to claim 1, characterized in that: The specific process of step 2 is: 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.

5. The method for preparing chiral carbon quantum dots for optical limiting according to claim 4, characterized in that: In the step 2, the amount of dichloromethane used is 5-20 mL.

6. The method for preparing chiral carbon quantum dots for optical limiting according to claim 4, characterized in that: In step 2, the ultrasonic time is 5 to 10 minutes.

7. The method for preparing chiral carbon quantum dots for optical limiting according to claim 4, characterized in that: In step 2, the freeze-drying time is 24-48 hours.

8. Chiral carbon quantum dots for optical limiting, prepared by the method for preparing chiral carbon quantum dots for optical limiting as claimed in any one of claims 1 to 7.

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