A papaya leaf carbon quantum dot and a cleaning agent

Abstract

This invention discloses a papaya leaf carbon quantum dot and a cleaning agent composition containing the papaya leaf carbon quantum dots. The papaya leaf carbon quantum dots are prepared by a hydrothermal reaction of total alkaloids from papaya leaves and citric acid. This invention also discloses a method for preparing the cleaning agent composition and its application in cleaning air conditioning filters of rail transit vehicles; particularly its application in cleaning air conditioning filters of rail transit vehicles during the poplar and willow catkin season. The cleaning agent composition of this invention has a descaling rate of over 95% and is non-corrosive to equipment. Furthermore, equipment cleaned with this cleaning agent also possesses certain rust prevention, self-cleaning, and surface repair capabilities.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemistry and cleaning agents, and particularly relates to a carbon quantum dot of papaya leaf and a cleaning agent containing the carbon quantum dot. BACKGROUND

[0002] The train compartment of a motor train set is a closed space, and needs to rely on the air conditioning system for ventilation. When the motor train is running, dust in the air will adhere to the air conditioner filter screen. When there are foreign matters on the air conditioner filter screen, if not cleaned in time, the filter screen will be blocked, the ventilation in the train compartment will be poor, the air quality in the train will decrease, and at the same time, the air conditioner will not be able to normally dissipate heat and work. Not only the experience of passengers will be affected, but also the safe operation of the motor train set will be endangered. Therefore, the air conditioner filter screen of the motor train set must be cleaned regularly, especially in the season when the cotton and willow catkins are high. However, the motor train set has a high frequency of departure, and the cleaning and repair time is limited. The Chinese invention patent application with the publication number CN115895793A (publication date April 4, 2023) discloses a motor train air conditioner cleaning agent and a preparation method thereof, and the composition is 10-20 parts of mild organic acid, 5-10 parts of surfactant, 1-5 parts of anticorrosive agent, 1-3 parts of water-soluble hydrophobic film-forming agent, 1-3 parts of bactericide, 1-5 parts of acaricide, 60-80 parts of solvent, and also includes 2-3 parts of auxiliary agent; wherein the mild organic acid is composed of hydroxyacetic acid, aminosulfonic acid and methylsulfonic acid in a mass ratio of (3-4):(1-2):(1-2), the surfactant is composed of alkyl glycoside and fatty alcohol polyoxyethylene ether carboxylate in a mass ratio of (4-5):(2-3), the water-soluble hydrophobic film-forming agent is nano zinc oxide and organic bentonite modified water-soluble silicone oil, and the auxiliary agent is composed of polyacrylic acid sodium, cuprous oxide and polytetrafluoroethylene in a mass ratio of (2-3):(5-6):(3-4). Although the patent application discloses that the motor train air conditioner cleaning agent has small corrosion, the components are complex, and the cleaning effect on willow catkins and cotton catkins is unknown.

[0003] Carbon quantum dots (CQDs) are a new type of carbon nanomaterials with particle size less than 10 nm, following carbon nanotubes, nanodiamonds and graphene. CQDs have the advantages of high stability, environmental friendliness and good water solubility. In recent years, the application of CQDs in cleaning, scale removal and scale inhibition has also attracted attention. Li Hui synthesized L-CCQDs and Ly-CCQDs carbon quantum dot scale inhibitors by one-pot hot melt polycondensation method using citric acid and L-ascorbic acid as raw materials, and L-lysine and anhydrous citric acid as raw materials, respectively (Li Hui. Preparation and performance of carboxyl carbon quantum dot scale inhibitor [D]. Northeast Petroleum University. June 6, 2023). The cleaning agent disclosed in the invention patent application "Environmentally friendly nano insulator cleaning agent and preparation method thereof" (publication date July 4, 2023) contains 0.2-0.8% of carbon quantum dots, which are prepared by microwave method using ethylenediamine and citric acid as raw materials.

[0004] So far, there has been no application of CQDs in cleaning the filter screen of the air conditioner of the EMU. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application first provides a papaya leaf carbon quantum dot, and further provides a cleaning agent containing the papaya leaf carbon quantum dot and its application in cleaning the filter screen of the air conditioner of the EMU, especially the filter screen of the air conditioner of the EMU with willow catkins and willow catkins adhered.

[0006] To this end, the present application adopts the following technical solutions:

[0007] A papaya leaf carbon quantum dot, which emits blue fluorescence under 365 nm ultraviolet light, is prepared by a method comprising the following steps:

[0008] I. Preparation of papaya leaf dry powder:

[0009] Fresh papaya leaves are dried, crushed and passed through a 40-60 mesh sieve to obtain papaya leaf dry powder;

[0010] II. Preparation of total alkaloids of papaya leaf

[0011] The papaya leaf dry powder obtained in step I is extracted with 95% ethanol solution for 6 times, the pH is adjusted to 4.0-5.0 each time, soaked overnight, and filtered; the ethanol extract is combined, filtered, the filtrate is extracted with petroleum ether at 40-45℃, and the petroleum ether layer is discarded; the remaining part is adjusted to pH 8.0-9.0 and extracted with chloroform several times until the extract is clear, the chloroform extract is combined, the solvent is recovered under reduced pressure, and dried to obtain total alkaloids of papaya leaf;

[0012] III. Preparation of papaya leaf carbon quantum dots

[0013] The total alkaloids from papaya leaves obtained in step II were evenly dispersed in water, and then reacted with citric acid in a hydrothermal reactor at 190-210°C for 5-10 hours. After naturally cooling to room temperature, the mixture was centrifuged at high speed, filtered, and the filter cake was freeze-dried under vacuum to obtain papaya leaf carbon quantum dots.

[0014] Preferably, in step I, the drying conditions are: 40-60℃ for 48-96 hours; more preferably, 50-55℃ for 60-72 hours.

[0015] Preferably, in step II, the weight of 95% ethanol is 1-3 times the weight of the dried papaya leaf powder, more preferably 2 times, for each cold soaking.

[0016] Preferably, in step II, the volume ratio of petroleum ether to the filtrate is 1:3 to 1:4.

[0017] Preferably, in step II, during chloroform extraction, the amount of chloroform used each time is 0.5-1 times the volume of the extractant, more preferably 1 times the volume of the extractant.

[0018] Preferably, in step III, the mass ratio of the total alkaloids of the papaya leaves to water is 1:1.

[0019] Preferably, the total alkaloids of the papaya leaves are evenly dispersed in water by ultrasound for 20-30 minutes.

[0020] Preferably, the mass ratio of total alkaloids in papaya leaves to citric acid is 1:0.6-1:1; more preferably, it is 1:0.8.

[0021] Preferably, the citric acid is added to the hydrothermal reactor in the form of an aqueous solution with a mass percentage concentration of 15%-25%.

[0022] More preferably, the citric acid aqueous solution has a mass percentage concentration of 20%.

[0023] Preferably, in step III, the reaction temperature of the total alkaloids of papaya leaves with citric acid is 200°C.

[0024] Preferably, in step III, the total alkaloids of papaya leaves react with citric acid in a hydrothermal reactor for 8 hours.

[0025] Preferably, in step III, the high-speed centrifugation speed is 10000 r / min, and the centrifugation time is 5-10 min, more preferably 8 min.

[0026] A second objective of this invention is to provide a cleaning agent composition comprising the papaya leaf carbon quantum dots described herein.

[0027] As a preferred embodiment, the present invention provides a cleaning agent composition comprising, by weight 100%,:

[0028] The present invention comprises 0.8-1% carbon quantum dots from papaya leaves, 3-6% sodium bicarbonate, 8-12% sodium carbonate, 3-6% sodium silicate, 3-5% trans polyether, 0.5-0.8% composite corrosion inhibitor, 1.2-1.5% trisodium dimethylglycine diacetate, 4-5% polyaspartic acid, 2-3% fatty alcohol polyoxyethylene ether, 8-12% ethylene glycol, and the balance being water.

[0029] Preferably, the composite corrosion inhibitor is composed of sodium benzoate, benzotriazole (BTA), and diethanolamine in a mass ratio of 2:1:1.

[0030] The cleaning agent composition of the present invention has the following functions for each component:

[0031] Papaya leaf carbon quantum dots: enhance the corrosion inhibition effect of cleaning agents; form a nanofilm on the surface of the cleaned object, thereby giving the surface non-stick properties;

[0032] Composite corrosion inhibitor: Provides corrosion inhibition for cleaning agents;

[0033] Trisodium methylglycine diacetate: a scale solvent that dissolves surface deposits;

[0034] Polyaspartic acid: a scale inhibitor that helps disperse the components of the cleaning agent described in this invention and stabilize the system;

[0035] Trans polyether: enhances the penetration of cleaning agents and improves their detergency;

[0036] Ethylene glycol: Improves the water solubility of composite corrosion inhibitors.

[0037] Furthermore, a third objective of this invention is to provide a method for preparing the above-mentioned cleaning agent composition, comprising the following steps:

[0038] S1. Prepare each component according to its mass percentage;

[0039] S2. Add water to a mixing device equipped with a stirring device, and while stirring, add sodium bicarbonate, sodium carbonate, and sodium silicate, and stir until evenly mixed;

[0040] S3. Continue to add ethylene glycol, polyaspartic acid, trisodium methylglycine diacetate, composite corrosion inhibitor, trans polyether, and fatty alcohol polyoxyethylene ether in sequence, and stir until uniform;

[0041] S4. Finally, add the papaya leaf carbon quantum dots described in this invention, stir evenly, and the resulting transparent liquid is the cleaning agent composition.

[0042] Preferably, in step S2, the stirring time is 0.5-2 hours, more preferably 1 hour.

[0043] Preferably, in step S3, the stirring time is 1.5-3 hours, more preferably 2 hours.

[0044] Preferably, in step S4, the stirring time is 20 min to 1 h, more preferably 30 min.

[0045] Preferably, in steps S2-S4, the stirring speed is 500-700 r / min.

[0046] The present invention also provides the application of the above-mentioned cleaning agent composition in cleaning air conditioning filters of rail transit vehicles; especially in cleaning air conditioning filters of rail transit vehicles during the season when poplar and willow catkins are flying.

[0047] Preferably, the rail transit vehicles include high-speed trains.

[0048] Specifically, the application includes: diluting the cleaning agent composition of the present invention with water to a mass percentage concentration of 30%-50%, spraying it onto the air conditioning filter to be cleaned, letting it stand for 10-20 minutes, and then rinsing it with tap water.

[0049] Of course, if the air conditioner filter is heavily soiled with poplar catkins, willow catkins or other dirt, the cleaning agent composition described in this invention can be sprayed directly onto the filter, left to stand for an appropriate time, generally 20-30 minutes, and then rinsed clean with water.

[0050] The cleaning agent composition described in this invention is not limited to cleaning air conditioning filters in rail transit vehicles, but can also be used in other scenarios, such as filters in residential and commercial air conditioners, etc.

[0051] Unless otherwise specified, the term "water" in this instruction manual refers to purified water, such as deionized water, distilled water, double-distilled water, etc.

[0052] The cleaning agent described in this invention has strong dissolving, penetrating, and stripping properties, enabling it to quickly loosen plant fibers such as poplar and willow catkins, as well as dust and oxides adhering to the air conditioning filters of high-speed trains, thus dissolving and suspending them in the cleaning agent. The cleaning agent of this invention achieves a descaling rate of over 95%. No corrosion occurs in the equipment during the cleaning process. Furthermore, equipment cleaned with this cleaning agent also possesses certain rust-preventing, self-cleaning, and surface-repairing capabilities. Attached Figure Description

[0053] The present invention will be further described below with reference to the accompanying drawings.

[0054] Figure 1 This is the Nyquist plot (complex impedance plot) obtained in Example 1.

[0055] Figure 2 This is the Bode modulus diagram obtained in Example 1.

[0056] Figure 1 and Figure 2 middle,

[0057] 1:3% HCl;

[0058] 2: 3% HCl + 0.01 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution;

[0059] 3: 3% HCl + 0.1 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution;

[0060] 4: 3% HCl + 1 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution;

[0061] 5: 3% HCl + 3 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution.

[0062] Figure 3 The photographs show the steel surface polished before immersion and the steel surface after immersion in different corrosion inhibitor solutions during the corrosion inhibition performance test in Example 1. Wherein:

[0063] (a): Steel surface polished before immersion;

[0064] (b): Steel surface after immersion in 3% HCl solution for 24 hours;

[0065] (c): Steel surface after being immersed in 3% HCl + 0.01 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution for 24 hours;

[0066] (d): Steel surface after being immersed in 3% HCl + 0.1 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution for 24 hours;

[0067] (e): Steel surface after being immersed in 3% HCl + 1 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution for 24 hours;

[0068] (f): Steel surface after being immersed in 3% HCl + 3 mg / L papaya leaf carbon quantum dot corrosion inhibitor solution for 24 hours.

[0069] Figure 4 The photograph shows the surface repair capability test results of the cleaner prepared in Example 2, wherein:

[0070] A: A photo of the hard material before cleaning;

[0071] B: Photos of the same area of ​​the hard material after cleaning.

[0072] Figure 5 The photograph shows the surface repair capability test results of the cleaner prepared in Example 3, wherein:

[0073] A: A photo of the hard material before cleaning;

[0074] B: Photos of the same area of ​​the hard material after cleaning.

[0075] Figure 6 The photograph shows the surface repair capability test results of the cleaner prepared in Example 4, wherein:

[0076] A: A photo of the hard material before cleaning;

[0077] B: Photos of the same area of ​​the hard material after cleaning.

[0078] Figure 7 The photograph shows the results of Example 5's test of the cleaning agent's ability to remove poplar and willow catkins, among other things.

[0079] A: The train's air conditioning filter before cleaning;

[0080] B: The cleaned air conditioning filter of the high-speed train. Detailed Implementation

[0081] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0082] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products. Example 1: Preparation and Performance Study of Carbon Quantum Dots from Papaya Leaves

[0083] 1. Preparation of Papaya Carbon Quantum Dots

[0084] 1.1 Hydrothermal preparation of papaya leaf carbon quantum dots I:

[0085] I. Preparation of Papaya Leaf Powder

[0086] Take 200 kg of fresh papaya leaves, dry them at 55℃ for 72 hours, pulverize them and pass them through a 60-mesh sieve to obtain 35 kg of dried papaya leaf powder.

[0087] II. Preparation of total alkaloids from papaya leaves

[0088] Take 32 kg of dried papaya leaf powder, extract it by cold soaking in 64 kg of 95% ethanol solution, adjust the pH to 4.0-5.0 with hydrochloric acid, soak overnight, and filter. Repeat the cold soaking extraction 6 times. Combine the ethanol extracts and filter them at 55℃. Extract the filtrate with 1 / 3 volume of petroleum ether and discard the petroleum ether portion. Adjust the pH of the remaining portion to 8.0-9.0 with ammonia water, and then extract it with 1 volume of chloroform. Repeat the extraction several times until the chloroform extract is clear. Combine the chloroform extracts, recover the solvent under reduced pressure, and dry at 55℃ to obtain 87 g of total alkaloids from papaya leaves.

[0089] III. Hydrothermal Preparation of Carbon Quantum Dots from Papaya Leaves

[0090] 50 mg of total alkaloids from papaya leaves was added to 50 ml of deionized water and sonicated for 20 min to obtain an aqueous solution of total alkaloids from papaya leaves. This aqueous solution was transferred to a hydrothermal reactor, and then 80 ml of a 20% (w / w) citric acid aqueous solution was added. The reaction was continued at 200 °C for 8 hours. After naturally cooling to room temperature, the reaction mixture was centrifuged at 10000 r / min for 10 min, filtered, and the filter cake was freeze-dried under vacuum to obtain powdered papaya leaf carbon quantum dots I (23 mg), which exhibited blue fluorescence under a 365 nm UV lamp.

[0091] Two more aqueous solutions of total alkaloids from papaya leaves were prepared using the same method. These solutions were reacted separately with 80 ml of 20% (w / w) citric acid aqueous solution in a hydrothermal reactor at temperatures of 180℃ and 230℃, respectively. At 180℃, the resulting lyophilized powder showed no blue fluorescence under 365 nm UV light, indicating that no carbon quantum dots were obtained. At 230℃, only 2 mg of the lyophilized powder exhibited blue fluorescence at 365 nm.

[0092] Therefore, the reaction temperature for preparing papaya leaf carbon quantum dots by hydrothermal method should be around 200℃, for example, 190-210℃.

[0093] 2. Performance Study and Measurement of Carbon Quantum Dot I from Papaya Leaves

[0094] 2.1 Study on biodegradability

[0095] According to GB / T15818-2018 "Test Methods for Biodegradability", the carbon quantum dots I of papaya leaves were tested. The determination was performed using the foam method described therein.

[0096] The degradation rate of the 80 mg / L papaya leaf carbon quantum dot solution was 100% on day 7.

[0097] This demonstrates that the papaya leaf carbon quantum dots of the present invention have excellent environmental performance.

[0098] 2.2 Study on corrosion inhibition performance

[0099] The papaya leaf carbon quantum dots prepared according to the above method were used to prepare aqueous solutions of 0.01 mg / L, 0.1 mg / L, 1 mg / L and 3 mg / L with water, respectively. 10 ml of each of these aqueous solutions was added to 500 ml of 3% HCl aqueous solution and mixed thoroughly to obtain corrosion inhibitor solutions of different concentrations.

[0100] 45# steel specimens were immersed in corrosion inhibitor solutions of different concentrations and a 3% HCl aqueous solution for 24 hours. Electrochemical impedance spectroscopy was measured using an electrochemical workstation, and Nyquist and Bode modulus plots of the steel in corrosion inhibitor solutions of different concentrations were obtained. (See figures below.) Figure 1 and Figure 2 In the Nyquist and Bode modulus diagrams, a larger capacitive arc radius indicates a lower corrosion rate of the metal, meaning the corrosion inhibitor has a higher inhibition efficiency. For example... Figure 1 and Figure 2 As shown, the capacitive arc radius increases with the increase of the concentration of carbon quantum dots from papaya leaves, indicating that carbon quantum dots from papaya leaves can significantly reduce the corrosion of steel, especially when the concentration is 3 mg / L, the corrosion inhibition effect is the best.

[0101] Figure 3 The photographs show the surface condition of the steel before and after the corrosion inhibition test. Before the test, the steel surface was smooth. Figure 3 (a) After steel was immersed in a 3% HCl solution without the addition of the papaya leaf carbon quantum dots described in this invention for 24 hours, severe corrosion pits appeared on the surface. Figure 3 (b) After adding papaya leaf carbon quantum dots, the corrosion of the steel surface was slightly reduced, and a rough protective layer appeared on the surface. Figure 3 (c) and (d) show that as the concentration of carbon quantum dots from papaya leaves increases, a denser and more obvious protective layer appears on the steel surface, and the corrosion phenomenon disappears. Figure 3 (e) and (f)).

[0102] In summary, the papaya leaf carbon quantum dots of the present invention have significant anti-corrosion and corrosion-inhibiting effects.

[0103] Examples 2-5: A cleaning agent

[0104] The cleaning agents in Examples 2-5 all contain papaya leaf carbon quantum dots prepared according to the method in Example 1. The specific composition is shown in Table 1, and they are prepared by the following method:

[0105] S1. Prepare each component according to its mass percentage;

[0106] S2. Add water to a mixing device equipped with a stirring device, and while stirring, add sodium bicarbonate, sodium carbonate, and sodium silicate, and stir until evenly mixed;

[0107] S3. Continue to add ethylene glycol, polyaspartic acid, trisodium methylglycine diacetate, composite corrosion inhibitor, trans polyether, and fatty alcohol polyoxyethylene ether in sequence, and stir until uniform;

[0108] S4. Finally, add the papaya leaf carbon quantum dots prepared according to the method in Example 1, stir evenly, and the resulting transparent solution is the target product.

[0109] Comparative Examples 1-3: A cleaning agent

[0110] The specific compositions of the cleaning agents in Comparative Examples 1-3 are shown in Table 1, and they were prepared according to the same methods and steps as in Examples 2-5.

[0111] Table 1. Composition of the cleaning agents in Examples 2-5 and Comparative Examples 1-3 (unit: % w / w)

[0112]

[0113]

[0114] *: The composite corrosion inhibitor is a mixture of sodium benzoate, BTA, and diethanolamine in a mass ratio of 2:1:1. Test Example 1: Determination of the cleaning agent performance in the examples and comparative cases.

[0115] 1. Oil stain cleaning power:

[0116] According to Q / CR468-2015 "Cleaning Agents for the External Surfaces of High-Speed ​​Trains", paint coating test pieces were used. The cleaning agents from Examples 2-5 and Comparative Examples 1-3 were prepared into 5% (w / w) solutions using deionized water. 500 ml of each solution was placed in a beaker, and the beakers were then placed in a constant temperature water bath at (40±2)℃. The oil-stained test pieces (pre-weighed) were fixed onto the fixture of the washing machine and fully immersed in the solutions in each beaker for 3 minutes. After soaking and washing, the test pieces were placed in an oven at (50±2)℃ for drying, cooling, and weighing. The cleaning power was calculated. The results are shown in Table 2.

[0117] Table 2 shows the results of the oil-stain cleaning power tests of the cleaning agents in each example and comparative example.

[0118] Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Cleaning power 70％ 86％ 95％ 82％ 80％ 58％ 66％

[0119] The results show that the cleaning agent of Example 4 has the best degreasing ability.

[0120] 2. Metal corrosivity

[0121] The cleaning agents from Examples 2-5 and Comparative Examples 1-3 were each prepared into 5% (w / w) solutions using deionized water to obtain test solutions. Brass, aluminum alloy, and steel sheets were weighed separately using a balance and placed into the prepared test solutions. These solutions were then placed in a constant-temperature water bath at (40±2)℃ for 4 hours. After the test, the test pieces were removed, rinsed with clean water, washed twice with anhydrous ethanol, dried with hot air, and then dried and cooled. The appearance of the test pieces was observed and rated. The results are shown in Table 3.

[0122] Table 3. Results of metal corrosivity tests on the cleaning agents of the examples and comparative examples.

[0123] Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Brass 0 grade 0 grade 0 grade 0 grade 0 grade 1 grade 1 grade Aluminum alloy 1 grade 1 grade 0 grade 1 grade 1 grade 2 grade 2 grade Steel sheet 0 grade 0 grade 0 grade 0 grade 1 grade 2 grade 1 grade

[0124] The results show that the metal corrosivity of the cleaning agents of the present invention is less than that of the comparative examples, with the least corrosivity in Example 4.

[0125] 3. Contact Angle Test

[0126] According to GB / T 30693-2014 Measurement of Contact Angle between Plastic Film and Water, the contact angle of the cleaning agents in each embodiment and comparative example on the plastic surface was measured using a video contact angle measuring instrument. The results are shown in Table 4.

[0127] The results show that the water contact angle of the cleaning agent of the present invention is significantly greater than that of the comparative examples, especially the contact angle of Example 4, which is the largest, indicating that the cleaning agent of the present invention can impart a certain self-cleaning property to the surface.

[0128] Table 4 shows the contact angles of the cleaning agents with water in the examples and comparative examples.

[0129] Number Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Contact angle 100° 120° ＞160° 110° 70° 55° 20°

[0130] 4. Foaming properties

[0131] According to the method specified in GB / T13173, the instantaneous foam height of the cleaning agent in each example and comparative example was tested at (40±2)℃ / mm, and the results are shown in Table 5.

[0132] Table 5. Results of foaming property tests for the cleaning agents in the examples and comparative examples.

[0133]

[0134] The higher the instantaneous foam height of the cleaning agent, the better its cleaning performance. The results show that the instantaneous foam height of the cleaning agents of the present invention is significantly higher than that of the comparative examples, with Example 4 showing the highest instantaneous height, indicating the best cleaning performance.

[0135] 5. Impact on sealant (polyurethane)

[0136] The cleaning agents of Examples 2-4 and Comparative Examples 1-3 were prepared into 5% (w / w) solutions using deionized water to obtain test solutions. Following the method specified in GB / T 1690, each test solution was placed in a constant temperature water bath at 50℃±2℃. Sealant test pieces (pre-weighed) were immersed in each test solution and kept at this temperature for 48 hours. Afterward, they were removed, dried, weighed, and their appearance was observed. The rate of change in mass was calculated, and the results are shown in Table 6.

[0137] Table 6 shows the effect of cleaning agents on polyurethane sealants in the examples and comparative examples.

[0138]

[0139] The results show that the cleaning agent of the present invention has a significantly smaller effect on polyurethane sealant than the comparative example, with the cleaning agent of Example 4 having the least effect.

[0140] 6. Conclusion

[0141] Through testing of the cleaning agent's detergency, metal corrosion resistance, contact angle, foaming properties, and impact on sealants, the cleaning agent of the present invention is generally superior to the comparative example, wherein Example 4 is a preferred embodiment of the present invention.

[0142] Further application of the preferred implementation scheme in Example 5

[0143] 1. Surface repair

[0144] The cleaning agents from Examples 2, 3, and 4 were respectively prepared into 5% (w / w) solutions with deionized water. Hard plastic test pieces with obvious scratches were immersed in the solutions for 30 minutes, then removed and rinsed thoroughly with tap water. It was found that the scratches on the surface of all test pieces were significantly reduced. The results are shown below. Figure 4 , 5 And 6.

[0145] Figure 4 , 5 Image A in Figure 6 is a photograph of the test piece before soaking, and obvious scratches are visible. Figure 4 , 5 Image B in Figure 6 shows the specimen after soaking. Compared to before soaking, the scratches are significantly reduced.

[0146] The test results show that the cleaning agent of the present invention has the function of repairing surface scratches.

[0147] 2. Cleaning poplar (willow) catkins

[0148] The cleaning agent from Example 4 was prepared into a 30% (w / w) solution with deionized water. This solution was sprayed onto the surface of the train's air conditioning filter screen, which was covered with poplar (willow) catkins. The solution was left to stand for 10 minutes, then rinsed with tap water. The results are shown below. Figure 7 .

[0149] Figure 7 As shown, before cleaning, the air conditioning filter of the high-speed train was covered with white poplar (willow) fluff (A), and after cleaning, the air conditioning filter returned to its original condition (B). This demonstrates that the cleaning agent of the present invention can quickly and thoroughly clean the poplar (willow) fluff from the air conditioning filter.

Claims

1. A type of papaya leaf carbon quantum dot, exhibiting blue fluorescence under 365 nm ultraviolet light, is prepared by a method comprising the following steps: I. Preparation of Papaya Leaf Powder: Take fresh papaya leaves, dry them, and pulverize them through a 40-60 mesh sieve to obtain dried papaya leaf powder; II. Preparation of total alkaloids from papaya leaves The dried papaya leaf powder obtained in step I was extracted 6 times by cold soaking in 95% ethanol solution, adjusting the pH to 4.0-5.0 each time, soaking overnight, and then filtering. The ethanol extracts were combined, filtered, and the filtrate was extracted with petroleum ether at 40-45℃. The petroleum ether layer was discarded. The pH of the remaining part was adjusted to 8.0-9.0 and extracted multiple times with chloroform until the extract was clear. The chloroform extracts were combined, the solvent was recovered under reduced pressure, and the extract was dried to obtain the total alkaloids of papaya leaves. III. Preparation of carbon quantum dots from papaya leaves The total alkaloids from papaya leaves obtained in step II were evenly dispersed in water, and then reacted with citric acid in a hydrothermal reactor at 190-210°C for 5-10 hours. After naturally cooling to room temperature, the mixture was centrifuged at high speed, filtered, and the filter cake was freeze-dried under vacuum to obtain papaya leaf carbon quantum dots.

2. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step I, the drying conditions are: 40-60℃ for 48-96 hours.

3. The papaya leaf carbon quantum dots according to claim 2, characterized in that, In step I, the drying conditions are: 50-55℃ for 60-72 hours.

4. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step II, each time the 95% ethanol is used for cold soaking, the weight of the ethanol is 1-3 times the weight of the dried papaya leaf powder.

5. The papaya leaf carbon quantum dots according to claim 4, characterized in that, In step II, each time the 95% ethanol is used for cold soaking, the weight of the ethanol is twice the weight of the dried papaya leaf powder.

6. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step II, the volume ratio of petroleum ether to the filtrate is 1:3 to 1:

4.

7. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step II, during chloroform extraction, the amount of chloroform used each time is 0.5-1 times the volume of the extracted liquid.

8. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step III, the mass ratio of total alkaloids in papaya leaves to water is 1:

1.

9. The papaya leaf carbon quantum dots according to claim 1 or 8, characterized in that, In step III, the total alkaloids of papaya leaves are evenly dispersed in water by ultrasound for 20-30 minutes.

10. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step III, the mass ratio of total alkaloids in papaya leaves to citric acid is 1:0.6 - 1:

1.

11. The papaya leaf carbon quantum dots according to claim 10, characterized in that, In step III, the mass ratio of total alkaloids in papaya leaves to citric acid is 1:0.

8.

12. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step III, the citric acid is added to the hydrothermal reactor in the form of an aqueous solution with a mass percentage concentration of 15%-25%.

13. The papaya leaf carbon quantum dots according to claim 12, characterized in that, The citric acid aqueous solution has a mass percentage concentration of 20%.

14. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step III, the reaction temperature of total alkaloids from papaya leaves with citric acid is 200℃.

15. The papaya leaf carbon quantum dots according to claim 1 or 14, characterized in that, In step III, the total alkaloids of papaya leaves react with citric acid in a hydrothermal reactor for 8 hours.

16. The papaya leaf carbon quantum dots according to claim 1, characterized in that, In step III, the high-speed centrifugation speed is 10000 r / min, and the centrifugation time is 5-10 min.

17. The papaya leaf carbon quantum dots according to claim 16, characterized in that, In step III, centrifuge at high speed for 8 minutes.

18. A cleaning agent composition comprising papaya leaf carbon quantum dots as claimed in any one of claims 1 to 17.

19. The cleaning agent composition according to claim 18, comprising, by weight 100%,: The papaya leaf carbon quantum dots as described in any one of claims 1 to 17 are: 0.8-1% sodium bicarbonate, 3-6% sodium carbonate, 8-12% sodium carbonate, 3-6% sodium silicate, 3-5% trans polyether, 0.5-0.8% composite corrosion inhibitor, 1.2-1.5% trisodium methylglycine diacetate, 4-5% polyaspartic acid, 2-3% fatty alcohol polyoxyethylene ether, 8-12% ethylene glycol, and the balance being water.

20. The cleaning agent composition according to claim 19, characterized in that, The composite corrosion inhibitor is composed of sodium benzoate, benzotriazole and diethanolamine in a mass ratio of 2:1:

1.

21. A method for preparing the cleaning agent composition according to claim 19 or 20, comprising the following steps: S1. Prepare each component according to its mass percentage; S2. Add water to a mixing device equipped with a stirring device, and while stirring, add sodium bicarbonate, sodium carbonate, and sodium silicate, and stir until evenly mixed; S3. Continue to add ethylene glycol, polyaspartic acid, trisodium methylglycine diacetate, composite corrosion inhibitor, trans polyether, and fatty alcohol polyoxyethylene ether in sequence, and stir until uniform; S4. Finally, add the papaya leaf carbon quantum dots as described in any one of claims 1 to 17, stir evenly, and the resulting transparent liquid is the cleaning agent composition.

22. The preparation method according to claim 21, characterized in that, In step S2, the stirring time is 0.5-2 hours.

23. The preparation method according to claim 22, characterized in that, In step S2, the stirring time is 1 hour.

24. The preparation method according to claim 21, characterized in that, In step S3, the stirring time is 1.5-3 hours.

25. The preparation method according to claim 24, characterized in that, In step S3, the stirring time is 2 hours.

26. The preparation method according to claim 21, characterized in that, In step S4, the stirring time is 20 min to 1 h.

27. The preparation method according to claim 26, characterized in that, In step S4, the stirring time is 30 minutes.

28. The preparation method according to claim 21, characterized in that, In steps S2-S4, the stirring speed is 500-700 r / min.

29. The use of the cleaning agent composition of claim 19 or 20 or the cleaning agent composition directly obtained by the preparation method according to any one of claims 21 to 28 in cleaning air conditioning filters of rail transit vehicles.

30. The use of the cleaning agent composition of claim 19 or 20 or the cleaning agent composition directly obtained by the preparation method according to any one of claims 21 to 28 in cleaning the air conditioning filters of rail transit vehicles during the poplar and willow catkin season.

31. The application according to claim 29 or 30, characterized in that, The rail transit vehicles include high-speed trains.

32. The application according to claim 29 or 30, characterized in that, The application includes: diluting the cleaning agent composition with water to a mass percentage concentration of 30%-50%, spraying it onto the air conditioning filter to be cleaned, letting it stand for 10-20 minutes, and then rinsing it with tap water.

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