oil-soluble carbon quantum dots and preparation method thereof
阅读说明：本技术 一类油溶性碳量子点及其制备方法 (oil-soluble carbon quantum dots and preparation method thereof ) 是由 张和凤 方来平 于 2019-10-14 设计创作，主要内容包括：本发明涉及一类油溶性碳量子点及其制备方法,制备包括采用表面活性剂为唯一碳源进行一步碳化得到油溶性碳量子点；所述表面活性剂亲油端含有12-30C,且亲水基团结构热稳定性差,易加热分解。表面活性剂包括烷基阴离子型系列、烷基阳离子型系列、吐温系列、司盘系列、糖基系列、甜菜碱系列、卵磷脂系列和氨基酸系列中的一种。一步碳化的方法包括溶剂热法和无溶剂的固相反应法。本发明的碳源种类多,来源广,价廉易得；得到的油溶性碳量子点形貌相似,大小均一,且含有纳米晶体结构。本发明用含有不同元素的表面活性剂作为碳源可制备杂原子掺杂的油溶性碳量子点。(The invention relates to a oil-soluble carbon quantum dot and a preparation method thereof, wherein the preparation method comprises the step of carbonizing by adopting a carbon source which is a surfactant, the lipophilic end of the surfactant contains 12-30C, the hydrophilic group structure has poor thermal stability and is easy to heat and decompose, the surfactant comprises of alkyl anion series, alkyl cation series, tween series, span series, glycosyl series, betaine series, lecithin series and amino acid series, and the step of carbonizing comprises a solvothermal method and a solvent-free solid-phase reaction method.)
The preparation method of the oil-soluble carbon quantum dots is characterized by mainly comprising the step of -step carbonization by using carbon source which is only surfactant, wherein the oleophilic end of the surfactant contains 12-30C, and the hydrophilic group structure has poor thermal stability and is easy to heat and decompose.
2. The method for preparing oil-soluble carbon quantum dots according to claim 1, wherein the surfactant comprises of alkyl anionic series, alkyl cationic series, tween series, span series, glycosyl series, betaine series, lecithin series and amino acid series.
3. The method for preparing the oil-soluble carbon quantum dot according to claim 1, wherein the -step carbonization method comprises a solvothermal method and a solvent-free solid-phase reaction method.
4. The method for preparing the oil-soluble carbon quantum dots according to claim 3, wherein the solvothermal method mainly comprises the following steps:
(1) dispersing a surfactant in a high-boiling point low-polarity solvent, heating to 120-250 ℃ by using an electric heating plate, and cooling to room temperature;
(2) and (3) separating the solvent from the reaction liquid by using diatomite as a medium and petroleum ether and ethyl acetate as eluents, removing insoluble impurities, and concentrating to obtain the oil-soluble carbon quantum dots.
5. The method for preparing the oil-soluble carbon quantum dots according to claim 3, wherein the solvent-free solid phase reaction method mainly comprises the following steps:
(1) uniformly stirring the surfactant and the silica gel, and heating for 5-120 minutes by using microwave;
(2) adding ethyl acetate, performing ultrasonic filtration, and separating silica gel;
(3) and removing insoluble impurities by using diatomite as a medium and petroleum ether and ethyl acetate as an eluent, and concentrating to obtain the oil-soluble carbon quantum dots.
6. The method for preparing oil-soluble carbon quantum dots according to claim 4, wherein 2 to 20g of the surfactant is added per 50 to 400mL of the high-boiling-point low-polarity solvent in the step (1).
7. The method for preparing the oil-soluble carbon quantum dot according to claim 5, wherein the mass ratio of the surfactant to the silica gel is 1: 1-10.
8. The method for preparing the oil-soluble carbon quantum dots according to claim 4, wherein the high-boiling point low-polarity solvent comprises or more of n-alkane series, brominated alkane series, decahydronaphthalene, toluene and diphenyl methyl ether.
9. The oil-soluble carbon quantum dot prepared by the method of claim 1.
Technical Field
The invention belongs to the field of new materials, and particularly relates to oil-soluble carbon quantum dots and a preparation method thereof.
Background
Carbon Quantum Dots (CQDs), also known as Carbon dots (C-dots), are low in price, easy to prepare, low in toxicity, good in biocompatibility, photostability and photobleaching resistance due to its raw material source , and are regarded as the best material for replacing traditional inorganic quantum dots and semiconductor quantum dots in aspects of drug loading, biological imaging, fluorescent probes, etc. however, more than 95% of the Carbon quantum dots reported at present are water-soluble, and still lack a good solution in aspects of large-scale preparation and particle size control, which is an important reason for restricting the further development and application of .
Heretofore, although "top-down" methods of arc discharge, laser ablation, electrochemical oxidation, and the like of macroscopic graphite carbon sources have been used for the preparation of carbon quantum dots, the carbon quantum dot products prepared by these methods are of very low purity and have a very broad size distribution, requiring purification and size classification of the products by means of multiple long-term dialysis and the like before use. Then, from the bottom to the top synthesis methods such as incomplete combustion, thermal cracking and microwave-assisted thermal cracking of small organic molecules and hydrothermal methods of biomass have been developed. The carbon quantum dots synthesized by these "bottom-up" methods are significantly improved in size distribution over the "top-down" methods, but the resulting products still have a broader size distribution. Rhee et al prepared carbon quantum dots with a size distribution between 1.0-5.0 nm by carbonization of glucose in micelles under optimal conditions. In this scale, a broad size distribution can greatly interfere with establishing an accurate carbon quantum dot structure-activity relationship due to a strong size effect. At present, both methods have random characteristics no matter from top to bottom or from bottom to top, and the yield and the product size cannot be controlled accurately; and the yield of carbon quantum dots and the efficiency of fluorescence quantum are not high.
In addition, most of the carbon quantum dots are realized by carbonizing organic small molecules such as citric acid and ethylenediamine or natural products such as orange juice, watermelon, cola and rice, so that the obtained carbon quantum dots are almost water-soluble, the water-soluble property of the quantum dots in the aspect of limits the application of the quantum dots in more aspects, the post-treatment process of the water-soluble quantum dots in the aspect of is relatively troublesome, the water-soluble carbon quantum dots must be separated and purified in a way of changing water and dialysis tapes for a long time in the later period, the time consumption is long, the yield is low, and meanwhile, the aim of mass preparation cannot be realized in objective conditions.
Disclosure of Invention
The method adopts the low-price commercial surfactant as the sole carbon source, does not need redundant synthesis steps, can obtain the oil-soluble carbon quantum dots after carbonizing the hydrophilic end, can obtain the oil-soluble carbon quantum dots with the particle size of by utilizing the steric hindrance effect of long-chain alkane carried by the surfactant, can realize quick carbonization in a short time by utilizing microwave as a heating source, and greatly shortens the preparation time, thereby well solving the problems that the single water-solubility of the current carbon quantum dots cannot be prepared in a large scale, the particle size is difficult to control and the like, and providing possibility for quickly and massively preparing the oil-soluble quantum dots with the particle size of .
A preparation method of oil-soluble carbon quantum dots mainly comprises the step of carbonization by adopting a carbon source which is only a surfactant to obtain the oil-soluble carbon quantum dots, wherein the oleophilic end of the surfactant contains 12-30C, and the hydrophilic group structure has poor thermal stability and is easy to heat and decompose.
The carbon source used in the invention is only substances which are surfactants, the end containing hydrophilic groups is easily carbonized under heating conditions, and the end long-chain alkane is not easily carbonized under the same temperature, most of the prior art adopts at least two substances as the carbon source and has great difference, a small amount of substances are only used as the carbon source, organic substances (such as amine and aldehyde) are used as the carbon source (nonionic) in the work of other people, but the biocompatibility of the substances is not clear, commercial anionic, nonionic and amphoteric surfactants are adopted in the invention, the industrial surfactants are rich in types, the fluorescent core structure and the peripheral carbon chain of the carbon point can be conveniently regulated and controlled by selecting different surfactants, the carbon quantum points with different heteroatom doping and different carbon chain lengths are prepared, the luminous behavior and the dissolubility of the carbon quantum points can be regulated, for example, the carbon quantum point prepared by sucrose ester only contains carbon, hydrogen and oxygen, three elements, the periphery of the carbon quantum point is prepared by using octadecene, the carbon quantum point prepared by using octodecaine, the carbon quantum point prepared by using the same carbon quantum point, the luminous property of the sucrose ester, the carbon quantum point prepared by using the method, the active carbon point prepared by using the method, the active carbon point prepared by using the method of the active carbon point of the method, the method of preparing the method.
The invention provides a method for directly carbonizing hydrophilic groups of surfactants with long-chain alkane aiming at that most of the carbon quantum dots are water-soluble at present, and realizes the rapid synthesis of oil-soluble carbon quantum dots, namely at high temperature, hydrophilic ends of the surfactants can be carbonized to generate carbon dot cores, but lipophilic ends are not carbonized to provide excellent oil solubility, so that the oil-soluble carbon quantum dots are prepared.
Preferably, the surfactant includes alkyl anionic series (sodium alkyl benzene sulfonate, sodium alkyl sulfate, sodium alkyl carboxylate), alkyl cationic series (octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, dodecyl dimethyl amine oxide, octadecyl methyl amine bromide), tween series (
Preferably, the carbonization method includes a solvothermal method and a solvent-free solid-phase reaction method.
Preferably, the solvothermal method for synthesizing the oil-soluble carbon quantum dots mainly comprises the following steps of:
(1) dispersing a surfactant in a high-boiling point low-polarity solvent, heating to 120-250 ℃ by using an electric heating plate, and cooling to room temperature;
(2) and (3) separating the solvent from the reaction liquid by using diatomite as a medium and petroleum ether and ethyl acetate as eluents, removing insoluble impurities, and concentrating to obtain the oil-soluble carbon quantum dots.
Preferably, 2-20g of surfactant is added per 50-400mL of high boiling point low polarity solvent in step (1).
Preferably, the high boiling point low polarity solvent comprises or more of n-alkanes series (n-decanone to n-pentazane), brominated alkanes series (bromooctane to bromotriacontane), decalin, toluene and anisole.
Firstly, dissolving a surfactant in a nonpolar organic solvent to form nano-micelles in a moderate temperature environment, gradually changing single molecules into reverse nano-micelles with hydrophilic ends facing inwards and lipophilic ends facing outwards along with the continuous increase of the temperature of the surfactant in the presence of the nonpolar solvent, wherein the number of the molecules of the surfactant forming the nano-micelles cannot infinitely increase, so that the actual size of each nano-micelle is , the hydrophilic ends at the inner cores of the nano-micelles can be carbonized along with the continuous increase of the temperature, the lipophilic ends are reserved, the carbonization degrees of the micelles are the same within the same time, and therefore, the carbon quantum dots with the size of and the diameter of about 3 nanometers can be prepared.
The solvent thermal method needs to be carried out under the condition of constant feeding concentration, the concentration is too high, the surfactant is not completely dissolved and is not uniformly dispersed, the surfactant is more easily agglomerated in the heating process, more black carbonized precipitates are generated, the yield is low, the particle size is not uniform , the fluorescence is not strong, the concentration is too low, the yield is low, and the fluorescence property of the prepared carbon quantum dot is not strong.
Preferably, the solvent-free solid-phase reaction method for synthesizing the oil-soluble carbon quantum dots mainly comprises the following steps:
(1) uniformly stirring the surfactant and the silica gel, and heating for 5-120 minutes by using microwave;
(2) adding ethyl acetate, performing ultrasonic filtration, and separating silica gel;
(3) and removing insoluble impurities by using diatomite as a medium and petroleum ether and ethyl acetate as an eluent, and concentrating to obtain the oil-soluble carbon quantum dots.
At the moment, the silica gel has the function of dispersing the surfactant, so that the carbon source is heated more uniformly, otherwise, the surfactant is agglomerated in a large amount and heated unevenly.
Preferably, the mass ratio of the surfactant to the silica gel is 1:1-10, and preferably, the method further comprises the steps of performing column chromatography separation on the synthesized oil-soluble carbon quantum dots, separating insoluble impurities, and spin-drying the solution to obtain a carbon quantum dot product with a uniform particle size of .
The method is characterized in that under the condition of not adding any chemical reagent, the oil-soluble carbon quantum dots are prepared in a large scale in a short time by using a microwave-assisted method, after the surfactant and silica gel are uniformly mixed, the hydrophilic end of the surfactant is directly carbonized by using a ' step method' assisted by microwaves, while the lipophilic end with long-chain alkane can not be carbonized, under the condition of not adding any chemical reagent, the oil-soluble carbon quantum dots can be prepared in a large scale in a few minutes with high efficiency.
The oil-soluble carbon quantum dot prepared by the preparation method of the oil-soluble carbon quantum dot.
The invention adopts the microwave as the heating source, can rapidly heat up in a few minutes, is beneficial to the low-cost and large-scale preparation of the oil-soluble carbon quantum dots.
Drawings
FIG. 1 is a schematic representation of the structure of a representative surfactant preferred in the present invention.
FIG. 2 is a schematic diagram showing that the surfactant is carbonized in the presence of a solvent when the solvothermal method is employed in the present invention.
FIG. 3 is a graph showing the solubility of carbon quantum dots prepared according to the present invention in various solvents.
FIG. 4A is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solvothermal method and using sucrose fatty acid ester as a carbon source; b is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solid phase method and sucrose fatty acid ester as a carbon source; c is a TEM image of an oil-soluble carbon quantum dot solution prepared by using sucrose fatty acid ester as a carbon source; d is a fluorescence diagram of the carbon quantum dot solution prepared by a solvothermal method (left) and a solid-phase method (right) under a fluorescent lamp and a 365nm ultraviolet lamp; wherein the concentration of the solution is 5 mg/mL.
A in FIG. 5 is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solvothermal method and
FIG. 6A is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solvothermal method and using soybean lecithin as a carbon source; b, preparing a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution by using a solid phase method and soybean lecithin as a carbon source; c, taking a TEM image of an oil-soluble carbon quantum dot solution prepared by taking soybean lecithin as a carbon source; d is a fluorescence diagram of the carbon quantum dot solution prepared by a solvothermal method (left) and a solid-phase method (right) under a fluorescent lamp and a 365nm ultraviolet lamp; wherein the concentration of the solution is 5 mg/mL.
FIG. 7A is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solvothermal method and dodecyl betaine as a carbon source; b is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solid phase method and dodecyl betaine serving as a carbon source; c, taking a TEM image of an oil-soluble carbon quantum dot solution prepared by taking dodecyl betaine as a carbon source; d is a fluorescence diagram of the carbon quantum dot solution prepared by a solvothermal method (left) and a solid-phase method (right) under a fluorescent lamp and a 365nm ultraviolet lamp; wherein the concentration of the solution is 5 mg/mL.
FIG. 8A is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solid phase method and Tween 80 as a carbon source; b is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solid phase method and sodium cocoyl glutamate serving as a carbon source; the concentration of the solution was 10 mg/mL. C, preparing a fluorescence emission spectrum of the oil-soluble carbon quantum dot solution by using a solid phase method and sodium dodecyl benzene sulfonate as a carbon source; d is a fluorescence emission spectrum of an oil-soluble carbon quantum dot solution prepared by a solid phase method and octadecyl trimethyl ammonium chloride serving as a carbon source;
FIG. 9 is a histogram showing the fluorescence intensity contrast of days and six months for the oil-soluble carbon quantum dot solution prepared by the solvothermal method and the dodecyl betaine as the carbon source, and B is a histogram showing the fluorescence intensity contrast of the oil-soluble carbon quantum dot solution prepared by the solvothermal method and the dodecyl betaine as the carbon source under 365nm ultraviolet wavelength continuous irradiation for different durations, wherein the concentration of each solution is 2.5 mg/mL.
Fig. 10 shows oil-soluble carbon quantum dots prepared in large quantities by a solvent-free solid-phase reaction method and using
FIG. 11 is a graph for exploring the fluorescence quenching effect of iron ion solutions of different concentrations on a carbon quantum dot solution (4 mg/mL).
FIG. 12 shows fluorescence emission spectra of carbon quantum dots prepared by solvothermal method, using sucrose ester as carbon source and decalin as solvent, and using different reaction concentrations.
FIG. 13 is a fluorescence emission spectrum of a carbon quantum dot solution prepared by a solid phase method using ammonium dodecyl sulfate as a carbon source; the concentration of the solution was 10 mg/mL.
Detailed Description
To make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings.
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