Method for co-producing carbon-based solid acid and carbon quantum dots from rape seed cakes, carbon-based solid acid and application thereof, and carbon quantum dots and application thereof

Abstract

The invention discloses a method for co-producing carbon-based solid acid and carbon quantum dots from rape seed cakes, the carbon-based solid acid and application thereof, and the carbon quantum dots and application thereof, and relates to the technical field of biomass conversion. The method for co-producing the carbon-based solid acid and the carbon quantum dots from the rape seed cakes comprises the following steps: mixing rape seed cake powder and water, and carrying out hydrothermal carbonization treatment to obtain a hydrothermal carbonization product; and carrying out solid-liquid separation on the hydrothermal carbonization product to obtain the carbon-based solid acid and the carbon quantum dots. According to the technical scheme, co-production of the carbon-based solid acid and the carbon quantum dots from the rape seed cakes is achieved, the prepared carbon-based solid acid is used for preparing the 5-hydroxymethylfurfural, and the advantage of being high in yield is achieved; the prepared carbon quantum dot is used for detecting baicalein or tetracycline, and has the advantage of wide detection range. According to the technical scheme, the rape seed cakes serve as raw materials, co-production of the carbon-based solid acid and the carbon quantum dots is achieved through a simple and safe hydrothermal method, and high economical efficiency and practicability are achieved.

Description

Technical Field

[0001] The present invention relates to the field of biomass conversion, and in particular to a method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, carbon-based solid acid and application thereof, and carbon quantum dots and application thereof. Background Art

[0002] Carbon-based solid acid is a heterogeneous catalyst widely used in the chemical industry, with the advantages of high acid density, water resistance, no pollution, and reusability. It is usually used in acid-catalyzed reactions, with high stability and good thermal stability, but existing carbon-based solid acids often need to be prepared by carbonization of raw materials and sulfonation with concentrated sulfuric acid, which is not only cumbersome but also highly dangerous.

[0003] Carbon quantum dots are a type of zero-dimensional carbon nanomaterial with significant fluorescent properties. They are water-soluble, light-stable, low-toxic, green and environmentally friendly, and resistant to photobleaching, and have important application value in the field of detection. However, the carbon sources for synthesizing carbon quantum dots are mostly organic matter, carbon nanotubes, carbon fibers, graphite rods, and activated carbon, and the cost of these raw materials is relatively high.

[0004] Therefore, improving the defects of complicated preparation process of carbon-based solid acid and high preparation cost of carbon quantum dots remains a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] The main purpose of the present invention is to propose a method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, carbon-based solid acid and application, carbon quantum dots and application, aiming to solve the problems of low rapeseed cake utilization efficiency, poor economy, complicated carbon-based solid acid preparation process and high carbon quantum dot preparation cost.

[0006] To achieve the above object, the present invention proposes a method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, comprising the following steps:

[0007] Mixing rapeseed cake powder and water, and performing hydrothermal carbonization treatment to obtain a hydrothermal carbonization product;

[0008] The hydrothermal carbonization product is subjected to solid-liquid separation to obtain carbon-based solid acid and carbon quantum dots.

[0009] In one embodiment, the step of mixing rapeseed cake powder and water and performing hydrothermal carbonization to obtain a hydrothermal carbonized product comprises:

[0010] The rapeseed cake powder, the sulfonating agent and water are mixed and subjected to hydrothermal carbonization treatment to obtain a hydrothermal carbonization product.

[0011] In one embodiment, the rapeseed cake powder has a particle size of 40 to 80 meshes; and / or,

[0012] The mass ratio of the rapeseed cake powder to water is 1:(10-100); and / or,

[0013] The temperature of the hydrothermal carbonization treatment is 180-250° C.; and / or,

[0014] The hydrothermal carbonization treatment time is 1 to 24 hours.

[0015] In one embodiment, the mass ratio of the rapeseed cake powder to the sulfonating agent is 1:(0.5-2); and / or,

[0016] The sulfonating agent includes any one of p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, 5-methoxy-2-aminobenzenesulfonic acid and p-toluenesulfonic acid.

[0017] In one embodiment, the step of performing solid-liquid separation on the hydrothermal carbonization product to obtain carbon-based solid acid and carbon quantum dots comprises:

[0018] Carrying out solid-liquid separation on the hydrothermal carbonization product to obtain a solid and a filtrate;

[0019] The solid matter is sequentially washed and dried to obtain a carbon-based solid acid; the filtrate is sequentially dialyzed and freeze-dried to obtain carbon quantum dots.

[0020] The present invention provides a carbon-based solid acid, which is prepared according to the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, and the specific surface area of ​​the carbon-based solid acid is 1 to 100 cm 3 / g, and the acid strength of the carbon-based solid acid is 0.22-1.54 mmol / g.

[0021] The present invention provides an application of the carbon-based solid acid in catalyzing fructose dehydration reaction.

[0022] The present invention provides a carbon quantum dot, which is prepared according to the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake.

[0023] The present invention proposes an application of the carbon quantum dots in detecting baicalein.

[0024] The present invention proposes an application of the carbon quantum dots in detecting tetracycline.

[0025] The beneficial effects of the technical solution of the present invention are as follows:

[0026] The technical solution of the present invention is to crush the cheap and readily available rapeseed cake, directly perform hydrothermal carbonization treatment or add a sulfonating agent to perform hydrothermal carbonization treatment together, and then perform solid-liquid separation on the obtained hydrothermal carbonization product, the obtained solid is the carbon-based solid acid, and the obtained filtrate is the solution containing carbon quantum dots, thereby realizing the co-production of carbon-based solid acid and carbon quantum dots, the process is simple and environmentally friendly, broadens the application scope of rapeseed cake, and has high economic efficiency. In addition, the carbon-based solid acid prepared from rapeseed cake can be used to efficiently catalyze fructose to obtain 5-hydroxymethylfurfural, and the yield can reach more than 90%; the carbon quantum dots prepared by direct hydrothermal carbonization of rapeseed cake can be used to detect baicalin, and the carbon quantum dots prepared by hydrothermal carbonization of rapeseed cake and sulfonating agent can be used to detect tetracycline, and the detection method is convenient and fast, with high sensitivity and a wide linear range. In addition, the technical solution of the present invention can prepare two carbon quantum dots with different fluorescent properties by controlling whether to add a sulfonating agent, and has good controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0028] Figure 1 This is a process flow chart of an embodiment of co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake provided by the present invention;

[0029] Figure 2 This is a process flow chart of another embodiment of the co-production of carbon-based solid acid and carbon quantum dots from rapeseed cake provided by the present invention;

[0030] Figure 3 The fluorescence emission spectra of the carbon quantum dot solutions prepared in Examples 1-4 of the present invention and the actual images under sunlight and ultraviolet light;

[0031] Figure 4 is a quenching curve diagram of the carbon quantum dots prepared in Example 1 of the present invention and baicalein;

[0032] Figure 5 This is a diagram showing the effect of the fluorescence of the carbon quantum dots prepared in Example 3 of the present invention being quenched by tetracycline at different concentrations;

[0033] Figure 6 This is a quenching curve diagram of the carbon quantum dots prepared in Example 3 and tetracycline.

[0034] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0038] Rapeseed oil is one of the main edible oils in my country. During the production process of rapeseed oil, rapeseed cake is its main residual material. At present, the main ways to dispose of rapeseed cake are direct waste, animal feed or preparation into organic fertilizer: the direct waste disposal method not only wastes resources, but also easily harms the ecological environment; when used as animal feed, it needs to go through a complex detoxification process, so the economic benefit is not high; when used to prepare organic fertilizer, it is usually used directly as a fertilizer, and there is a problem of insufficient nutrients resulting in weak fertility, so it is difficult to apply on a large scale, resulting in a great waste of resources.

[0039] Carbon-based solid acid is a heterogeneous catalyst widely used in the chemical industry, with the advantages of high acid density, no fear of water, no pollution, and reusability. It is usually used for acid-catalyzed reactions, with high stability and good thermal stability, but the existing carbon-based solid acid often needs to be prepared by carbonization of raw materials and sulfonation of concentrated sulfuric acid, which is not only cumbersome but also highly dangerous. In addition, carbon quantum dots are a type of zero-dimensional carbon nanomaterial with significant fluorescence properties, which has the characteristics of water solubility, photostability, low toxicity, green environmental protection, and resistance to photobleaching, and has important application value in the field of detection. However, the carbon sources for synthesizing carbon quantum dots currently use organic matter, carbon nanotubes, carbon fibers, graphite rods, and activated carbon, and the cost of such raw materials is relatively high. Therefore, improving the defects of cumbersome preparation process of carbon-based solid acid and high preparation cost of carbon quantum dots is still a technical problem that technicians in this field need to solve urgently.

[0040] In view of this, the present invention proposes a method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake.

[0041] See also Figure 1 In one embodiment of the present invention, the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake comprises the following steps:

[0042] Mixing rapeseed cake powder and water, and performing hydrothermal carbonization treatment to obtain a hydrothermal carbonization product;

[0043] The hydrothermal carbonization product is subjected to solid-liquid separation to obtain carbon-based solid acid and carbon quantum dots.

[0044] The inventors found that rapeseed cake is a better choice for synthesizing carbon-based solid acid and carbon quantum dot materials, given that it contains high levels of protein and polysaccharides. The technical solution of the present invention uses rapeseed cake, which is cheap and easily available, as raw material, directly hydrothermally carbonizes the rapeseed cake, and then separates the hydrothermal carbonization product into solid and liquid. The obtained solid is the carbon-based solid acid, and the obtained filtrate is the solution containing carbon quantum dots, thereby realizing the co-production of carbon-based solid acid and carbon quantum dots from rapeseed cake, with mild synthesis conditions, simple and environmentally friendly process, and a wide range of raw material sources, which are renewable and highly economical.

[0045] It should be noted that the conventional method of preparing carbon-based solid acid from biomass usually includes carbonization and sulfonation processes, that is, selecting suitable biomass materials for pyrolysis or carbonization at high temperature to generate carbon-rich precursor materials, and then treating the carbon-containing precursor materials with a sulfonating agent to introduce sulfonic acid groups (-SO3H), thereby improving the catalytic activity of carbon-based solid acids. The technical solution of the present invention uses rapeseed cake as a raw material to prepare carbon-based solid acid, and no additional sulfonating agent is required to achieve carbon-based solid acid with good catalytic performance. The prepared carbon-based solid acid has components of carbon, oxygen, nitrogen and sulfur elements, including acidic groups such as hydroxyl and carboxyl.

[0046] In addition, rapeseed cake contains a high level of protein. The use of protein-rich raw materials to prepare carbon quantum dots has many advantages, such as improving quantum yield and making its luminescence performance better; such as excellent optical properties, nitrogen doping in protein can improve the optical properties of carbon quantum dots, so that the prepared carbon quantum dots have higher fluorescence efficiency and stability; such as multifunctionality, the prepared carbon quantum dots not only have good optical properties, but may also retain some functional groups of the raw materials, so that they show higher selectivity and functionality in specific applications; such as good biocompatibility and low toxicity. The technical solution of the present invention uses rapeseed cake as raw material, and the prepared carbon quantum dots have excellent luminescence performance, biocompatibility and low tolerance.

[0047] In order to further improve the catalytic activity of the prepared carbon-based solid acid and regulate the luminescence performance of carbon quantum dots, the present invention also proposes a method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake. Figure 2 , Figure 2 This is a process flow chart of another embodiment of the co-production of carbon-based solid acid and carbon quantum dots from rapeseed cake provided by the present invention. The steps of mixing rapeseed cake powder and water, performing hydrothermal carbonization treatment, and obtaining a hydrothermal carbonization product include:

[0048] The rapeseed cake powder, the sulfonating agent and water are mixed and subjected to hydrothermal carbonization treatment to obtain a hydrothermal carbonization product.

[0049] By hydrothermally carbonizing rapeseed cake and sulfonating agent, and then separating the obtained hydrothermal carbonization product into solid and liquid, the obtained solid is carbon-based solid acid, and the obtained filtrate is a solution containing carbon quantum dots, thereby realizing the co-production of carbon-based solid acid and carbon quantum dots from rapeseed cake, with mild synthesis conditions, simple and environmentally friendly process, wide source of raw materials, renewable, and high economy. The carbon-based solid acid prepared after adding sulfonating agent has components of carbon, oxygen, nitrogen and sulfur elements, including acidic groups such as hydroxyl, carboxyl and sulfonic acid groups. The prepared carbon quantum dots are nitrogen and sulfur doped carbon quantum dots. Compared with the carbon-based solid acid prepared without adding sulfonating agent, the addition of sulfonating agent is beneficial to increase the number of sulfonic acid groups in carbon-based solid acid, improve the acid strength of carbon-based solid acid, and improve catalytic activity; at the same time, sulfur element can be introduced into carbon quantum dots, thereby improving its fluorescence properties.

[0050] In an embodiment of the present invention, before hydrothermal carbonization, the rapeseed cake is pulverized to obtain rapeseed cake powder, so that the particle size of the rapeseed cake powder is 40-80 meshes, which is conducive to the full reaction of the rapeseed cake powder and improves the utilization rate.

[0051] In an embodiment of the present invention, the mass ratio of the rapeseed cake powder to water is 1:(10-100). The mass ratio of the rapeseed cake powder to water is set to 1:(10-100), and the yield of carbon-based solid acid and carbon quantum dots prepared from rapeseed cake is high, the reaction efficiency is high, and the material performance is stable. In one embodiment of the present invention, the mass ratio of the rapeseed cake powder to water is set to 1:50.

[0052] In an embodiment of the present invention, the temperature of the hydrothermal carbonization treatment is 180-250°C, and the time of the hydrothermal carbonization treatment is 1-24 hours. In one embodiment of the present invention, considering the yield and cost, the temperature of the hydrothermal carbonization treatment is set to 200-220°C, and the time of the hydrothermal carbonization treatment is set to 2 hours.

[0053] In an embodiment of the present invention, the mass ratio of the rapeseed cake powder to the sulfonating agent is 1:(0.5-2). Setting the mass ratio of the rapeseed cake powder to the sulfonating agent within the above range is conducive to preparing carbon-based solid acids and carbon quantum dots with good comprehensive performance.

[0054] In an embodiment of the present invention, the sulfonating agent includes any one of p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, 5-methoxy-2-aminobenzenesulfonic acid, and p-toluenesulfonic acid.

[0055] It should be noted that sulfuric acid or sulfur trioxide is usually used as a sulfonating agent to prepare carbon-based solid acids. The technical solution of the present invention selects aromatic sulfonic acid compounds as sulfonating agents, which can not only increase the sulfonic acid groups in the prepared carbon-based solid acid, improve the acidity of the material, and thus improve the catalytic performance; it can also modify the prepared carbon quantum dots to prepare nitrogen and sulfur co-doped carbon quantum dots, change the fluorescence characteristics of the carbon quantum dots and broaden the application range of the carbon quantum dots. In one embodiment of the present invention, p-aminobenzenesulfonic acid is selected as the sulfonating agent.

[0056] In an embodiment of the present invention, the step of performing solid-liquid separation on the hydrothermal carbonization product to obtain carbon-based solid acid and carbon quantum dots comprises:

[0057] Carrying out solid-liquid separation on the hydrothermal carbonization product to obtain a solid and a filtrate;

[0058] The solid matter is sequentially washed and dried to obtain a carbon-based solid acid; the filtrate is sequentially dialyzed and freeze-dried to obtain carbon quantum dots.

[0059] After the rapeseed cake powder is subjected to a hydrothermal carbonization reaction, the hydrothermal carbonization product includes unreacted raw materials and by-products in addition to carbon-based solid acid and carbon quantum dots. The hydrothermal carbonization product is separated into solid and liquid by centrifugation or filtration to obtain a solid and a filtrate. Subsequently, the solid is washed with deionized water to remove the unreacted raw materials until the filtrate is neutral; then, the washed solid is dried at 120°C to obtain a purified carbon-based solid acid. The filtrate is dialyzed to remove unreacted raw materials, by-products and small molecule impurities, and then the dialyzate after dialysis is freeze-dried to obtain purified carbon quantum dots, and the prepared carbon quantum dots have a uniform particle size distribution and are convenient for storage.

[0060] The present invention provides a carbon-based solid acid, which is prepared according to the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, and the specific surface area of ​​the carbon-based solid acid is 1 to 100 cm 3 / g, and the acid strength of the carbon-based solid acid is 0.22-1.54 mmol / g.

[0061] The present invention provides an application of the carbon-based solid acid in catalyzing fructose dehydration reaction.

[0062] The carbon-based solid acid is used as a catalyst to catalyze the dehydration of fructose to prepare 5-hydroxymethylfurfural (HMF), and the steps of preparing 5-hydroxymethylfurfural with the carbon-based solid acid include:

[0063] The carbon-based solid acid, fructose and dimethyl sulfoxide (DMSO) are mixed and reacted at 90 to 140° C. for 0.5 to 5 hours to obtain 5-hydroxymethylfurfural;

[0064] Wherein, the mass ratio of the carbon-based solid acid to fructose is (1:1) to (1:10).

[0065] Specifically, fructose is dissolved in DMSO and then a carbon-based solid acid is added. Using DMSO as a solvent, DMSO can effectively promote the dehydration reaction of fructose, and has a high fructose conversion rate and HMF selectivity. The prepared carbon-based solid acid is used to prepare 5-hydroxymethylfurfural, which has the advantages of high yield, high economy and practicality. In one embodiment of the present invention, the catalytic efficiency and yield are comprehensively considered, and the catalytic conditions are set to react at 120°C for 2 hours.

[0066] The present invention proposes an application of the carbon quantum dots in detecting baicalein.

[0067] Specifically, the step of detecting baicalein comprises:

[0068] The carbon quantum dots are dissolved in deionized water to prepare a carbon quantum dot solution of a certain concentration, and different concentrations of baicalin are added to the carbon quantum dot solution to obtain a plurality of carbon quantum dot solutions containing different baicalin concentrations;

[0069] Under the set excitation wavelength of the carbon quantum dots, fluorescence measurements are performed on the multiple carbon quantum dot solutions containing different baicalin concentrations to obtain a standard curve, wherein the abscissa of the standard curve is the concentration of baicalin, and the ordinate is the fluorescence quenching efficiency; the sample to be tested is added to the carbon quantum dot solution, and under the set excitation wavelength of the carbon quantum dots, fluorescence measurement is performed on the sample to be tested to obtain the fluorescence quenching efficiency; the concentration of baicalin in the sample to be tested is determined according to the fluorescence quenching efficiency and the standard curve.

[0070] The technical solution of the present invention uses carbon quantum dots to detect baicalein. The detection method is convenient and rapid, has high sensitivity and a wide linear range, and also broadens the application scope of rapeseed cake and improves the economy of rapeseed cake.

[0071] The present invention proposes an application of the carbon quantum dots in detecting tetracycline.

[0072] Specifically, the step of detecting tetracycline comprises:

[0073] The carbon quantum dots are dissolved in deionized water to prepare a carbon quantum dot solution of a certain concentration, and tetracycline of different concentrations is added to the carbon quantum dot solution to obtain a plurality of carbon quantum dot solutions containing different tetracycline concentrations;

[0074] Under the set excitation wavelength of the carbon quantum dots, fluorescence measurements are performed on the multiple carbon quantum dot solutions containing different tetracycline concentrations to obtain a standard curve, wherein the abscissa of the standard curve is the concentration of tetracycline, and the ordinate is the fluorescence quenching efficiency; the sample to be tested is added to the carbon quantum dot solution, and under the set excitation wavelength of the carbon quantum dots, the fluorescence measurement of the sample to be tested is performed to obtain the fluorescence quenching efficiency; the concentration of tetracycline in the sample to be tested is determined according to the fluorescence quenching efficiency and the standard curve.

[0075] The technical solution of the present invention uses carbon quantum dots to detect tetracycline. The detection method is convenient and rapid, has high sensitivity and a wide linear range, and also broadens the application scope of rapeseed cake and improves the economy of rapeseed cake.

[0076] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0077] In the following examples, the rapeseed cakes are from an oil processing plant in Miaotan Town, Gucheng County, Hubei Province, and can be directly taken and crushed.

[0078] Example 1

[0079] A method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake comprises the following steps:

[0080] (1) adding 1 g of 40-80 mesh rapeseed cake powder into 50 mL of ultrapure water to obtain a mixture, transferring the mixture into a reactor, and then hydrothermally carbonizing at 200° C. for 2 h;

[0081] (2) After the reaction is completed, the mixture is cooled to room temperature, and the hydrothermal carbonization product is separated by centrifugation to obtain a black solid and a filtrate, and the solid is washed with deionized water until the filtrate is neutral to obtain a purified solid, and then the purified solid is dried at 120° C. to obtain a carbon-based solid acid;

[0082] The filtrate was dialyzed with a 1000Da dialysis bag for 12 h to obtain a dialysis filtrate, and then the dialysis filtrate was freeze-dried at -50°C for 24 h to obtain carbon quantum dots.

[0083] Example 2

[0084] Compared with Example 1, the difference is that in step (1), 0.5 g of p-aminobenzenesulfonic acid is added to carry out hydrothermal carbonization; the specific steps are as follows:

[0085] (1) adding 1 g of 40-80 mesh rapeseed meal and 0.5 g of p-aminobenzenesulfonic acid into 50 mL of ultrapure water to obtain a mixture, transferring the mixture into a reactor, and then hydrothermally carbonizing the mixture at 200° C. for 2 h;

[0086] (2) After the reaction is completed, the mixture is cooled to room temperature, and the hydrothermal carbonization product is separated by centrifugation to obtain a black solid and a filtrate, and the solid is washed with deionized water until the filtrate is neutral to obtain a purified solid, and then the purified solid is dried at 120° C. to obtain a carbon-based solid acid;

[0087] The filtrate was dialyzed with a 1000Da dialysis bag for 12 h to obtain a dialysis filtrate, and then the dialysis filtrate was freeze-dried at -50°C for 24 h to obtain carbon quantum dots.

[0088] Example 3

[0089] Compared with Example 2, the difference is that the mass of p-aminobenzenesulfonic acid in step (1) is 1 g;

[0090] Example 4

[0091] Compared with Example 2, the difference is that the mass of p-aminobenzenesulfonic acid in step (1) is 2 g.

[0092] The fluorescence properties of the carbon quantum dots prepared in Examples 1-4 were tested. The test results are as follows: Figure 3 shown. Figure 3 The fluorescence emission spectra of the carbon quantum dot solutions prepared in Examples 1-4 of the present invention and the actual pictures under sunlight and ultraviolet light, wherein CDs-1 represents the carbon quantum dots of Example 1, CDs-2 represents the carbon quantum dots of Example 2, CDs-3 represents the carbon quantum dots of Example 3, and CDs-4 represents the carbon quantum dots of Example 4. Figure 3 It can be seen that carbon quantum dots with different fluorescence emission wavelengths, different fluorescence colors and different fluorescence intensities can be obtained by controlling whether to add p-aminobenzenesulfonic acid and the amount of p-aminobenzenesulfonic acid.

[0093] Example 5

[0094] Compared with Example 1, the difference is that the temperature of the hydrothermal carbonization treatment in step (1) is 220°C.

[0095] Example 6

[0096] Compared with Example 3, the difference is that the temperature of the hydrothermal carbonization treatment in step (1) is 220°C.

[0097] The carbon-based solid acid in Examples 1-6 was used to catalyze fructose dehydration to test its catalytic performance. The specific test steps are as follows:

[0098] 0.5 g of fructose was added to a 10 mL thick-walled pressure bottle and dissolved in 3 mL of DMSO solution. 0.1 g of the carbon-based solid acid of Example 1-6 was added to the above mixture as a catalyst. The reactor was heated to 120° C. and reacted for 2 h. After the reaction was completed, the catalyst and the reaction product were separated by centrifugation. The product solution was analyzed by high performance liquid chromatography. The results are shown in Table 1.

[0099] Table 1 Catalytic performance of carbon-based solid acids of Examples 1-6 for fructose dehydration to 5-hydroxymethylfurfural

[0100]

[0101] As shown in Table 1, the catalytic effects of Examples 2-4 and Example 6 are better than those of Example 1 and Example 5, indicating that the introduction of a sulfonating agent and the rapeseed cake powder for hydrothermal carbonization treatment is beneficial to improving the catalytic activity of the prepared carbon-based solid acid, and improving the fructose conversion rate and the yield of 5-hydroxymethylfurfural. As shown in the test results of Examples 1-6, the carbon-based solid acid prepared by the present invention can be used to efficiently catalyze fructose to obtain 5-hydroxymethylfurfural, and the maximum yield can reach more than 90%.

[0102] Example 7

[0103] An application of carbon quantum dots in detecting baicalein comprises the following steps:

[0104] (1) dissolving 0.001 g of the carbon quantum dots of Example 1 in 100 mL of deionized water to prepare a carbon quantum dot solution, and adding different concentrations of baicalein to the carbon quantum dot solution to obtain a plurality of carbon quantum dot solutions containing different baicalein concentrations;

[0105] (2) setting the excitation wavelength of the carbon quantum dots to 360 nm, and performing fluorescence measurement on the multiple carbon quantum dot solutions containing different baicalein concentrations prepared in step (1) to obtain a standard curve, wherein the abscissa of the standard curve is the baicalein concentration, and the ordinate is the fluorescence quenching efficiency;

[0106] (3) adding the sample 1 to be tested to the carbon quantum dot solution, and performing fluorescence measurement on the sample 1 under the set excitation wavelength of the carbon quantum dots to obtain the fluorescence quenching efficiency; determining the concentration of baicalein in the sample 1 according to the fluorescence quenching efficiency and the standard curve, and the test result is as follows: Figure 4 shown.

[0107] Figure 4 is a quenching curve of the carbon quantum dot A prepared in Example 1 and baicalein, wherein: Figure 4 (A) is a graph showing the effect of baicalein on the fluorescence intensity of the carbon quantum dots of Example 1 of the present invention at 450 nm. Figure 4 (B) is a linear relationship diagram of the fluorescence quenching efficiency of the carbon quantum dots of Example 1 of the present invention at 450nm and the concentration of baicalein, Figure 4 It can be seen that with the increase of baicalein concentration, the fluorescence intensity of carbon quantum dots gradually weakened, and accordingly, the carbon quantum dots changed from blue-green to light yellow under ultraviolet light. The carbon quantum dots showed a good linear relationship in the baicalein concentration range of 0 to 170 μM, and had a wide detection range.

[0108] Example 8

[0109] An application of carbon quantum dots in detecting tetracycline comprises the following steps:

[0110] (1) dissolving 0.001 g of the carbon quantum dots of Example 3 in 100 mL of deionized water to prepare a carbon quantum dot solution, and adding tetracycline of different concentrations to the carbon quantum dot solution to obtain a plurality of carbon quantum dot solutions containing different tetracycline concentrations;

[0111] (2) setting the excitation wavelength of the carbon quantum dots to 375 nm, and performing fluorescence measurement on the plurality of carbon quantum dot solutions containing different tetracycline concentrations prepared in step (1) to obtain a standard curve, wherein the abscissa of the standard curve is the concentration of tetracycline, and the ordinate is the fluorescence quenching efficiency;

[0112] (3) adding the sample 2 to be tested to the carbon quantum dot solution, and performing fluorescence measurement on the sample 2 under the set excitation wavelength of the carbon quantum dots to obtain the fluorescence quenching efficiency; determining the concentration of tetracycline in the sample 2 according to the fluorescence quenching efficiency and the standard curve, and the test result is as follows: Figure 5 and Figure 6 shown.

[0113] Figure 5 The fluorescence of the carbon quantum dots prepared in Example 3 is quenched by tetracycline at different concentrations. Figure 5 It can be seen that as the concentration of added tetracycline gradually increases, the sky blue fluorescence of the carbon quantum dots gradually weakens until the concentration of tetracycline reaches 200 μM, when the fluorescence is basically quenched, indicating that tetracycline can effectively quench the carbon quantum dots prepared in this example. Figure 6 is a quenching curve diagram of the carbon quantum dots prepared in Example 3 and tetracycline, wherein: Figure 6 (A) is a graph showing the effect of tetracycline on the fluorescence intensity of carbon quantum dots at 455 nm in Example 3 of the present invention. Figure 6 (B) is a linear relationship diagram of the fluorescence quenching efficiency of the carbon quantum dots of Example 3 of the present invention at 455 nm and the tetracycline concentration, Figure 6 It can be seen that the carbon quantum dots show a good linear relationship in the tetracycline concentration range of 0 to 200 μM.

[0114] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake, characterized in that: The following steps are involved: Mixing rapeseed cake powder and water, and performing hydrothermal carbonization treatment to obtain a hydrothermal carbonization product; The hydrothermal carbonization product is subjected to solid-liquid separation to obtain carbon-based solid acid and carbon quantum dots.

2. The method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake according to claim 1, characterized in that: The step of mixing rapeseed cake powder and water and performing hydrothermal carbonization treatment to obtain a hydrothermal carbonized product comprises: The rapeseed cake powder, the sulfonating agent and water are mixed and subjected to hydrothermal carbonization treatment to obtain a hydrothermal carbonization product.

3. The method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake according to claim 1 or 2, characterized in that: The particle size of the rapeseed cake powder is 40 to 80 meshes; and / or, The mass ratio of the rapeseed cake powder to water is 1:(10-100); and / or, The temperature of the hydrothermal carbonization treatment is 180-250° C.; and / or, The hydrothermal carbonization treatment time is 1 to 24 hours.

4. The method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake as claimed in claim 2, characterized in that: The mass ratio of the rapeseed cake powder to the sulfonating agent is 1:(0.5-2); and / or, The sulfonating agent includes any one of p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, 5-methoxy-2-aminobenzenesulfonic acid and p-toluenesulfonic acid.

5. The method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake as claimed in claim 1, characterized in that: The step of performing solid-liquid separation on the hydrothermal carbonization product to obtain carbon-based solid acid and carbon quantum dots comprises: Carrying out solid-liquid separation on the hydrothermal carbonization product to obtain a solid and a filtrate; The solid matter is sequentially washed and dried to obtain a carbon-based solid acid; the filtrate is sequentially dialyzed and freeze-dried to obtain carbon quantum dots.

6. A carbon-based solid acid, characterized in that The carbon-based solid acid is prepared according to the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake according to any one of claims 1 to 5, and the specific surface area of ​​the carbon-based solid acid is 1 to 100 cm 3 / g, and the acid strength of the carbon-based solid acid is 0.22-1.54 mmol / g.

7. Use of the carbon-based solid acid as claimed in claim 6 in catalyzing fructose dehydration reaction.

8. A carbon quantum dot, characterized in that The carbon quantum dots are prepared according to the method for co-producing carbon-based solid acid and carbon quantum dots from rapeseed cake according to any one of claims 1 to 5.

9. Use of the carbon quantum dots as claimed in claim 8 in detecting baicalein.

10. Use of the carbon quantum dots as claimed in claim 8 in detecting tetracycline.

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