An ionic structure containing nitrogen-doped carbon quantum dots, a preparation method thereof, and applications thereof

Abstract

The present invention relates to a nitrogen-containing carbon quantum dot with an ionic structure, and the structure of the nitrogen-containing carbon quantum dot with an ionic structure is as follows:. Meanwhile, the present invention also discloses a preparation method and an application of the nitrogen-containing carbon quantum dot with an ionic structure. The preparation method of the present invention is simple, and the obtained nitrogen-containing carbon quantum dot with an ionic structure has good lubricating performance, solves the problems of insufficient lubrication and anti-wear performance of carbon quantum dots and poor dispersibility in non-polar lubricating oils, and expands the lubrication and anti-wear performance and application prospects of carbon quantum dots as lubricating oil additives.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating additives, and particularly relates to an ionic structure-containing nitrogen carbon quantum dot, a preparation method thereof, and an application thereof. Background Art

[0002] Friction and wear are important reasons for energy loss in industrial production, accounting for about 23% annually. It is necessary to find suitable lubricating materials for effective lubrication to reduce friction and wear. Carbon quantum dots are zero-dimensional fluorescent carbon nanomaterials with a quasi-spherical structure, with a size below 10 nm, and have characteristics superior to traditional lubricating materials such as self-repair, high strength, and strong interfacial adsorption. As a nanomaterial, carbon quantum dots play a basic role in the lubrication field, such as rolling, repairing, polishing, etc., and can repair the fine damage on the surface of the friction pair. In addition, a carbon protection film can be formed in the friction area through deposition. At the same time, the surface of carbon dots synthesized by the bottom-up method has various functional groups. By adjusting the types of precursors, carbon quantum dots with different structures can be obtained, which have strong modifiability and broaden the potential of carbon quantum dots as lubricating materials. However, the surface of carbon quantum dots generally contains oxygen-containing functional groups, with a relatively large polarity, and has poor long-term dispersion stability in non-polar lubricating oils, making it difficult to be used as an additive. Secondly, carbon quantum dots are prone to aggregation and need to be surface-modified to weaken the aggregation effect and improve the performance of carbon dots.

[0003] At present, there have been many studies on the modification methods of carbon quantum dots. Under the condition of maintaining their nanomaterial characteristics, surface modification is carried out by covalent bond grafting to weaken the self-aggregation of carbon dots and improve the dispersion stability of carbon dots in lubricating oils. However, the covalent bond modification method has high requirements for the functional groups of the modifier, the types of modifiers are single, the steps are cumbersome, and because it does not contain an ionic structure, the adsorption at the friction interface is relatively weak. In addition, ionic liquids can also be selected as modifiers to endow carbon quantum dots with an ionic structure, but the structures of ionic liquids that can be selected in this way are also few, and the obtained carbon quantum dots have a relatively strong polarity and poor dispersion stability in non-polar lubricating oils, and cannot be used as lubricating oil additives.

[0004] Ionic liquids refer to ionic compounds composed of organic cations and organic / inorganic anions that are in a liquid state near room temperature. The unique ionic structure, low saturated vapor pressure, and strong structural designability of ionic liquids make them potential high-performance lubricating materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an ionic structure-containing nitrogen carbon quantum dot with good lubricating performance.

[0006] Another technical problem to be solved by the present invention is to provide a preparation method of the nitrogen-containing carbon quantum dots with an ionic structure.

[0007] The third technical problem to be solved by the present invention is to provide an application of the nitrogen-containing carbon quantum dots with an ionic structure.

[0008] To solve the above problems, a kind of nitrogen-containing carbon quantum dots with an ionic structure according to the present invention is characterized in that the structure of the nitrogen-containing carbon quantum dots with an ionic structure is as follows:

[0009] 。

[0010] The preparation method of the nitrogen-containing carbon quantum dots with an ionic structure as described above includes the following steps:

[0011] ⑴ Prepare nitrogen-containing carbon quantum dots:

[0012] Mix o-phenylenediamine and salicylic acid, heat at 160-250 °C for 0.5-2 h, then add absolute ethanol to the reaction system and ultrasonically disperse for 20-60 min to obtain a mixed solution; centrifuge the mixed solution at 8000-10000 r / min for 5-10 min, dialyze the obtained supernatant for 12-24 h and then perform suction filtration, collect solid substance A, and vacuum dry it at 60-90 °C for 24-48 h to obtain nitrogen-containing carbon quantum dot powder;

[0013] ⑵ Prepare ionic structure carbon quantum dots:

[0014] Dissolve the nitrogen-containing carbon quantum dot powder in absolute ethanol to obtain a nitrogen-containing carbon quantum dot ethanol solution with a concentration of 50 mg / mL; slowly drop an excessive amount of bromoalkane into the nitrogen-containing carbon quantum dot ethanol solution, and stir and reflux at 70-90 °C for 48-72 h; after the reaction is completed, rotary evaporate to remove the solvent, add petroleum ether to dissolve the excessive bromoalkane, perform suction filtration, collect solid substance B, and vacuum dry the solid substance B at 60-90 °C for 24-48 h to obtain alkylated nitrogen-containing carbon quantum dot powder; dissolve the alkylated nitrogen-containing carbon quantum dot powder in absolute ethanol to obtain an alkylated nitrogen-containing carbon quantum dot ethanol solution with a concentration of 50 mg / mL; add an excessive amount of sodium salt to the alkylated nitrogen-containing carbon quantum dot ethanol solution and stir at room temperature for 12-24 h; after the reaction is completed, rotary evaporate to remove the solvent, add dichloromethane and water thereto, perform liquid separation operation, collect the lower organic phase, rotary evaporate to remove the solvent from the organic phase, and then vacuum dry it at 60-90 °C for 24-48 h to obtain the nitrogen-containing carbon quantum dots with an ionic structure.

[0015] In the step ⑴, the mass ratio of o-phenylenediamine, salicylic acid and absolute ethanol is 18.16:23.19:100.

[0016] In step (2), the bromoalkane refers to one of bromobutane, bromohexane, bromooctane, and bromododecane; the sodium salt refers to one of sodium bis(2-ethylhexyl) phosphate, sodium diphosphate decyl, and sodium bis(2,4,4-trimethylpentyl) phosphonate.

[0017] An application of a nitrogen-containing carbon quantum dot with an ionic structure as described above, characterized in that: the nitrogen-containing carbon quantum dot with an ionic structure is used as an additive in non-polar lubricating oil.

[0018] The present invention has the following advantages compared with the prior art:

[0019] 1. Drawing on the unique structure and synthesis method of ionic liquids, the present invention adopts a two-step method. First, through an alkylation reaction, a nitrogen-doped carbon quantum dot with a common anion structure is obtained, and then through an ion exchange method, the carbon quantum dot is anion-functionalized to obtain a nitrogen-containing carbon quantum dot with different anion structures.

[0020] 2. The present invention obtains an ionic structure carbon quantum dot by ion-bond modification of the formed carbon quantum dot, solving the problem of easy aggregation of carbon quantum dot materials.

[0021] 3. By doping nitrogen elements, the present invention increases the active sites in the carbon quantum dot structure, thereby performing anion-functionalization modification, solving the problems of insufficient lubrication and anti-wear performance of carbon quantum dots and poor dispersibility in non-polar lubricating oils, and expanding the lubrication and anti-wear performance and application prospects of carbon quantum dots as lubricating oil additives.

[0022] 4. The nitrogen-containing carbon quantum dot with an ionic structure described in the present invention is used as a non-polar lubricating oil additive, showing excellent lubrication and anti-wear performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0024] Figure 1 It is the transmission electron microscope photograph (a) and particle size distribution diagram (b) of the nitrogen-containing carbon quantum dot of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] A nitrogen-containing carbon quantum dot with an ionic structure, and the structure of the nitrogen-containing carbon quantum dot with an ionic structure is as follows:

[0026] 。

[0027] The preparation method of the nitrogen-containing carbon quantum dot with an ionic structure includes the following steps:

[0028] (1) Preparation of nitrogen-containing carbon quantum dots:

[0029] Mix o-phenylenediamine and salicylic acid, heat at 160 - 250 °C for 0.5 - 2 h, then add absolute ethanol to the reaction system and ultrasonically disperse for 20 - 60 min to obtain a mixed solution; centrifuge the mixed solution at 8000 - 10000 r / min for 5 - 10 min, dialyze the obtained supernatant for 12 - 24 h and then perform suction filtration, collect solid substance A, and vacuum dry at 60 - 90 °C for 24 - 48 h to obtain nitrogen-containing carbon quantum dot powder.

[0030] Among them: The mass ratio (g / g) of o-phenylenediamine, salicylic acid, and absolute ethanol is 18.16:23.19:100.

[0031] ⑵ Prepare ionic structure carbon quantum dots:

[0032] Dissolve the nitrogen-containing carbon quantum dot powder in absolute ethanol to obtain a nitrogen-containing carbon quantum dot ethanol solution with a concentration of 50 mg / mL; slowly drop an excessive amount of bromoalkane into the nitrogen-containing carbon quantum dot ethanol solution, and stir and reflux at 70 - 90 °C for 48 - 72 h; after the reaction is completed, remove the solvent by rotary evaporation, add petroleum ether to dissolve the excessive bromoalkane, perform suction filtration, collect solid substance B, and vacuum dry solid substance B at 60 - 90 °C for 24 - 48 h to obtain alkylated nitrogen-containing carbon quantum dot powder; dissolve the alkylated nitrogen-containing carbon quantum dot powder in absolute ethanol to obtain an alkylated nitrogen-containing carbon quantum dot ethanol solution with a concentration of 50 mg / mL; add an excessive amount of sodium salt to the alkylated nitrogen-containing carbon quantum dot ethanol solution and stir at room temperature for 12 - 24 h; after the reaction is completed, remove the solvent by rotary evaporation, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, remove the solvent from the organic phase by rotary evaporation, and then vacuum dry at 60 - 90 °C for 24 - 48 h to obtain ionic structure nitrogen-containing carbon quantum dots.

[0033] Among them: The bromoalkane refers to one of bromobutane, bromohexane, bromooctane, and bromododecane; the sodium salt refers to one of sodium bis(2-ethylhexyl) phosphate, sodium diphosphate decyl ester, and sodium bis(2,4,4-trimethylpentyl) phosphonate.

[0034] An application of ionic structure nitrogen-containing carbon quantum dots: The ionic structure nitrogen-containing carbon quantum dots are used as additives in non-polar lubricating oils.

[0035] Example 1 A preparation method of ionic structure nitrogen-containing carbon quantum dots, comprising the following steps:

[0036] ⑴ Prepare nitrogen-containing carbon quantum dots:

[0037] 18.16 g of o-phenylenediamine and 23.19 g of salicylic acid were added to a beaker and maintained at 220 °C for 1 h. After stopping heating, 100 g of absolute ethanol was added to the reaction system, and ultrasonic dispersion was carried out for 40 min, followed by centrifugation at 10,000 r / min for 5 min. The supernatant was dialyzed for 24 h, then filtered by suction, and the solid substance A was collected and dried in a vacuum drying oven at 90 °C for 48 h to obtain 3 g of nitrogen-doped carbon quantum dot powder. The transmission electron microscope photograph and particle size distribution diagram of its microscopic morphology are as shown in Figure 1 shown. According to the TEM image, the nitrogen-doped carbon quantum dots with ionic structure in the present invention are spherical in structure, without obvious aggregation, and have a uniform particle size distribution, with an average particle size between 1.5 - 1.9 nm.

[0038] ⑵ Preparation of ionic structure carbon quantum dots:

[0039] 1 g of nitrogen-doped carbon quantum dot powder was dissolved in 20 ml of absolute ethanol and added to a round-bottom flask. An excessive amount of bromobutane was slowly dropped into it, and the reaction was stirred and refluxed at 70 °C for 48 h. After the reaction was completed, the solvent was removed by rotary evaporation, petroleum ether was added to dissolve the excessive bromoalkane, and then filtered by suction. The solid substance B was collected and dried in a vacuum drying oven at 60 °C for 24 h to obtain alkylated nitrogen-doped carbon quantum dot powder. 1 g of alkylated nitrogen-doped carbon quantum dot powder was dissolved in 20 ml of absolute ethanol, and an excessive amount of sodium bis(2-ethylhexyl) phosphate was added thereto, and the reaction was stirred at room temperature for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation, dichloromethane and water were added thereto, and liquid separation operation was carried out. The lower organic phase was collected, and then the solvent was removed by rotary evaporation and further dried in vacuo at 60 °C for 24 h to obtain 1.23 g of ionic structure nitrogen-doped carbon quantum dots, denoted as B-NCDs-DEHP.

[0040] Example 2 A preparation method of ionic structure nitrogen-doped carbon quantum dots, comprising the following steps:

[0041] ⑴ The preparation method of preparing nitrogen-doped carbon quantum dots is the same as that in Example 1.

[0042] ⑵ Preparation of ionic structure carbon quantum dots:

[0043] Dissolve 1 g of nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add it to a round-bottom flask, slowly drop an excessive amount of bromohexane into it, and stir and reflux at 80 °C for 60 h. After the reaction, rotary evaporate to remove the solvent, add petroleum ether to dissolve the excessive bromohexane, then perform suction filtration, collect the solid substance B, and dry it in a vacuum drying oven at 70 °C for 36 h to obtain alkylated nitrogen-containing carbon quantum dot powder. Dissolve 1 g of alkylated nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add an excessive amount of sodium bis(2-ethylhexyl) phosphate to it, and stir at room temperature for 18 h. After the reaction, rotary evaporate to remove the solvent, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, then remove the solvent by rotary evaporation, and then dry it in a vacuum at 70 °C for 36 h to obtain 1.19 g of ion-structured nitrogen-containing carbon quantum dots, denoted as H-NCDs-DEHP.

[0044] Example 3 A preparation method of ion-structured nitrogen-containing carbon quantum dots, comprising the following steps:

[0045] ⑴ The preparation method of preparing nitrogen-containing carbon quantum dots is the same as that in Example 1.

[0046] ⑵ Prepare ion-structured carbon quantum dots:

[0047] Dissolve 1 g of nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add it to a round-bottom flask, slowly drop an excessive amount of bromooctane into it, and stir and reflux at 80 °C for 60 h. After the reaction, rotary evaporate to remove the solvent, add petroleum ether to dissolve the excessive bromooctane, then perform suction filtration, collect the solid substance B, and dry it in a vacuum drying oven at 70 °C for 36 h to obtain alkylated nitrogen-containing carbon quantum dot powder. Dissolve 1 g of alkylated nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add an excessive amount of sodium bis(2-ethylhexyl) phosphate to it, and stir at room temperature for 18 h. After the reaction, rotary evaporate to remove the solvent, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, then remove the solvent by rotary evaporation, and then dry it in a vacuum at 70 °C for 36 h to obtain 1.16 g of ion-structured nitrogen-containing carbon quantum dots, denoted as O-NCDs-DEHP.

[0048] Example 4 A preparation method of ion-structured nitrogen-containing carbon quantum dots, comprising the following steps:

[0049] ⑴ The preparation method of preparing nitrogen-containing carbon quantum dots is the same as that in Example 1.

[0050] ⑵ Prepare ion-structured carbon quantum dots:

[0051] Dissolve 1 g of nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add it to a round-bottom flask, slowly drop an excessive amount of dodecyl bromide into it, and stir and reflux at 90 °C for 72 h. After the reaction, remove the solvent by rotary evaporation, add petroleum ether to dissolve the excessive dodecyl bromide, then perform suction filtration, collect solid substance B, and dry it in a vacuum drying oven at 90 °C for 36 h to obtain alkylated nitrogen-containing carbon quantum dot powder. Dissolve 1 g of alkylated nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add an excessive amount of sodium bis(2-ethylhexyl) phosphate to it, and stir at room temperature for 24 h. After the reaction, remove the solvent by rotary evaporation, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, then remove the solvent by rotary evaporation, and then dry it at 90 °C in a vacuum for 36 h to obtain 1.17 g of ion-structured nitrogen-containing carbon quantum dots, denoted as DD-NCDs-DEHP.

[0052] Example 5 A method for preparing ion-structured nitrogen-containing carbon quantum dots, comprising the following steps:

[0053] ⑴ The method for preparing nitrogen-containing carbon quantum dots is the same as that in Example 1.

[0054] ⑵ Prepare ion-structured carbon quantum dots:

[0055] Dissolve 1 g of nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add it to a round-bottom flask, slowly drop an excessive amount of octyl bromide into it, and stir and reflux at 80 °C for 60 h. After the reaction, remove the solvent by rotary evaporation, add petroleum ether to dissolve the excessive octyl bromide, then perform suction filtration, collect solid substance B, and dry it in a vacuum drying oven at 70 °C for 36 h. Dissolve 1 g of the dried product in 20 ml of absolute ethanol, add an excessive amount of sodium diphenyl phosphate to it, and stir at room temperature for 24 h. After the reaction, remove the solvent by rotary evaporation, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, then remove the solvent by rotary evaporation, and then dry it at 90 °C in a vacuum for 48 h to obtain 1.18 g of ion-structured nitrogen-containing carbon quantum dots, denoted as O-NCDs-DDP.

[0056] Example 6 A method for preparing ion-structured nitrogen-containing carbon quantum dots, comprising the following steps:

[0057] ⑴ The method for preparing nitrogen-containing carbon quantum dots is the same as that in Example 1.

[0058] ⑵ Prepare ion-structured carbon quantum dots:

[0059] Dissolve 1 g of nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, and add it to a round-bottom flask. Slowly drop an excessive amount of octyl bromide into it, and stir and reflux at 80 °C for 60 h. After the reaction is completed, rotary evaporate to remove the solvent, add petroleum ether to dissolve the excessive octyl bromide, then perform suction filtration, collect the solid substance B, and dry it in a vacuum drying oven at 70 °C for 36 h to obtain alkylated nitrogen-containing carbon quantum dot powder. Dissolve 1 g of alkylated nitrogen-containing carbon quantum dot powder in 20 ml of absolute ethanol, add an excessive amount of sodium bis(2,4,4-trimethylpentyl)phosphonate to it, and stir at room temperature for 24 h. After the reaction is completed, rotary evaporate to remove the solvent, add dichloromethane and water to it, perform liquid separation operation, collect the lower organic phase, then rotary evaporate to remove the solvent, and then vacuum dry at 80 °C for 36 h to obtain 1.19 g of ionic structure nitrogen-containing carbon quantum dots, denoted as O-NCDs-DTPP.

[0060] Comparative Example

[0061] First, add 32.242 g (0.1 mol) of diisooctyl phosphate to a round-bottom flask. Under stirring conditions, slowly drop an equimolar amount of di-n-butylamine into the flask. After dropping is completed, stir and react at room temperature for 24 h. After the reaction is completed, vacuum dry the product at 80˚C for 24 h to obtain an ionic liquid with the same functional anion as the ionic structure nitrogen-containing carbon quantum dot B-NCDs-DEHP in Example 1, denoted as [N44HH][DEHP].

[0062] Friction performance test of ionic structure nitrogen-containing carbon quantum dots as lubricating oil additives:

[0063] On a four-ball friction and wear tester, investigate the lubricating and anti-wear performance of the ionic structure nitrogen-containing carbon quantum dots of the present invention as a lubricating additive for PAO base oil, and compare with the [N44HH][DEHP] ionic liquid in the comparative example. The addition amount of the ionic structure nitrogen-containing carbon quantum dots or the ionic liquid is 0.01%.

[0064] Select a load of 98 N, a temperature of room temperature, a rotation speed of 1200 r / min, an experimental time of 60 min, and the experimental balls are GCr15 steel balls. After the friction experiment is completed, use an optical microscope to measure the wear scar diameter. The friction experiment results are shown in Table 1.

[0065] Table 1 Comparison of average friction coefficients of base oil and base oil containing ionic structure nitrogen-containing carbon quantum dots or ionic liquid

[0066]

[0067] As can be seen from Table 1, compared with the base oil (PAO) and the [N44HH][DEHP] ionic liquid in the comparative example, the nitrogen-containing carbon quantum dots with an ionic structure of the present invention have excellent tribological properties.

[0068] In summary, the nitrogen-containing carbon quantum dots with an ionic structure of the present invention have good solubility in the non-polar lubricating oil PAO. As an additive for PAO, they exhibit good lubricating properties and outstanding anti-wear properties, and can be used as high-performance lubricating and anti-wear additives in the field of lubrication engineering.

Claims

1. An ionic structure nitrogen-doped carbon quantum dot, Characterized in that: The structure of the ionic structure nitrogen-doped carbon quantum dot is as follows: 。 2. A preparation method of an ionic structure nitrogen-doped carbon quantum dot according to claim 1, Comprising the following steps: ⑴ Preparation of nitrogen-doped carbon quantum dots: Mix o-phenylenediamine and salicylic acid, heat at 160~250 °C for 0.5~2 h, then add absolute ethanol to the reaction system and ultrasonically disperse for 20~60 min to obtain a mixed solution; the mixed solution is centrifuged at 8000~10000 r / min for 5~10 min, and the obtained supernatant is dialyzed for 12~24 h and then filtered by suction to collect solid substance A, which is vacuum-dried at 60~90 °C for 24~48 h to obtain nitrogen-doped carbon quantum dot powder; ⑵ Preparation of ionic structure carbon quantum dots: Dissolve the nitrogen-doped carbon quantum dot powder in absolute ethanol to obtain a nitrogen-doped carbon quantum dot ethanol solution with a concentration of 50 mg / mL; slowly drop an excessive amount of bromoalkane into the nitrogen-doped carbon quantum dot ethanol solution, and stir and reflux at 70~90 °C for 48~72 h; after the reaction is completed, rotary evaporate to remove the solvent, add petroleum ether to dissolve the excessive bromoalkane, filter by suction, collect solid substance B, and vacuum-dry the solid substance B at 60~90 °C for 24~48 h to obtain alkylated nitrogen-doped carbon quantum dot powder; the alkylated nitrogen-doped carbon quantum dot powder is dissolved in absolute ethanol to obtain an alkylated nitrogen-doped carbon quantum dot ethanol solution with a concentration of 50 mg / mL; add an excessive amount of sodium salt to the alkylated nitrogen-doped carbon quantum dot ethanol solution and stir at room temperature for 12~24 h; after the reaction is completed, rotary evaporate to remove the solvent, add dichloromethane and water thereto, perform liquid separation operation, collect the lower organic phase, rotary evaporate the organic phase to remove the solvent, and then vacuum-dry at 60~90 °C for 24~48 h to obtain ionic structure nitrogen-doped carbon quantum dots.

3. A preparation method of an ionic structure nitrogen-doped carbon quantum dot according to claim 2, Characterized in that: In the step ⑴, the mass ratio of o-phenylenediamine, salicylic acid, and absolute ethanol is 18.16:23.19:

100.

4. A preparation method of an ionic structure nitrogen-doped carbon quantum dot according to claim 2, Characterized in that: In the step ⑵, the bromoalkane refers to one of bromobutane, bromohexane, bromooctane, and bromododecane; the sodium salt refers to one of sodium bis(2-ethylhexyl) phosphate, sodium diphosphate decyl ester, and sodium bis(2,4,4-trimethylpentyl) phosphonate.

5. An application of an ionic structure nitrogen-doped carbon quantum dot according to claim 1, Characterized in that: The ionic structure nitrogen-doped carbon quantum dot is used as an additive in non-polar lubricating oil.

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