Biomass fluorescent carbon quantum dot and preparation method thereof
Technical Field
The invention relates to the field of nano materials, in particular to a biomass fluorescent carbon quantum dot and a preparation method thereof.
Background
The quantum dot has excellent optical and electrochemical properties, and has excellent properties such as quantum confinement effect, surface effect, size effect and the like when being used as a quasi-zero-dimensional nano material, so that the quantum dot is well applied to the fields of photoelectric devices, biological imaging, drug identification, sensing, catalysis and the like. However, most of the conventional quantum dots are semiconductor quantum dots, and heavy metal elements contained in the conventional quantum dots are high in biotoxicity, so that the application of the conventional quantum dots is limited. The development of low-toxicity or non-toxic quantum dot materials to replace semiconductor quantum dots has thus received great attention and extensive research.
The carbon quantum dots are carbon nano-particles with the particle size of less than 10nm, are a basic structural unit of a future nano-electronic device and a novel luminescent material, and have great potential application value in the fields of biosensing and biomedicine. Compared with the traditional quantum dots, the carbon quantum dots not only have excellent optical performance and electrochemical performance, but also have the characteristics of low toxicity, chemical inertness, easy functionalization, easy water solubility, good biocompatibility, high economic benefit and the like, so that the carbon quantum dots have attractive application prospects in the biomedical fields of photocatalysis, sensors, photoelectric devices, biological imaging, medical diagnosis and the like.
There are two main methods for synthesizing carbon quantum dots, namely a bottom-up method for reducing the size of a block material to a nano level by a physical or chemical method, such as an arc discharge method, a laser ablation method, an electrochemical method, etc., and a top-down method for preparing nano-level carbon quantum dots by changing a small molecular carbon source from a small size to a large size by a chemical synthesis method. Carbon sources for preparing carbon quantum dots have been developed from inorganic carbon materials such as carbon nanotubes, graphite, carbon black, candle ash, natural gas soot, activated carbon, charcoal ash, and carbon fiber, to organic carbon-containing natural products such as citric acid, saccharides, starch, vitamins, peanut skin, watermelon skin, and coffee grounds.
At present, biomass carbon quantum dots are mainly prepared through a hydrothermal reaction. The hydrothermal reaction of biomass is a chemical reaction which is carried out in a sealed pressure vessel under certain temperature and pressure conditions by taking water as a solvent. After the hydrothermal reaction, the carbon quantum dots are suspended and dispersed in the solution, and the pure product can be further obtained through the steps of centrifugal separation, dialysis purification and the like. The method has the advantages of simple and green hydrothermal preparation process, controllable surface and size of the obtained quantum dots and the like, and is widely applied to the method for preparing the fluorescent carbon quantum dots by using the biomass. The invention patent (201610054674.9A N, P, S co-doped fluorescent carbon quantum dot and a preparation method and application thereof) takes biomass fungi as a carbon source, and removes precipitated impurities and the like after hydrothermal reaction to obtain supernatant, namely a carbon quantum dot aqueous solution. The invention patent (201410222883.0A fluorescent amino carbon quantum dot and its preparation method and application) uses xylan as carbon source, and the supernatant obtained by removing precipitate after hydrothermal reaction in ammonia water solution is fluorescent amino carbon quantum water solution. The invention patent (201410554087.7 a macroscopic preparation method of fluorescent carbon quantum dots) adds bee pollen into ultrapure water, puts into a reaction kettle after ultrasonic treatment for hydrothermal reaction, and then removes precipitates to obtain a fluorescent carbon quantum solution. The invention patent (201410753601.X method for preparing nitrogen-doped carbon quantum dots based on shrimp waste) puts the shrimp waste and ultrapure water into a tetrafluoroethylene hydrothermal reaction kettle for hydrothermal reaction, and then performs suction filtration, collection, purification, concentration and drying to obtain the nitrogen-doped carbon quantum dots. However, in the process of preparing biomass carbon quantum dots by a hydrothermal method, a large amount of hydrothermal coke which is insoluble in a solution is generated, and the amount of carbon quantum dots which are generated by hydrothermal and suspended in a reaction solution is small, so that the yield of carbon quantum prepared by the hydrothermal method is low.
In the invention of preparing carbon quantum dots by biomass, a part of the bottom-up method is also provided, wherein biomass raw materials are firstly carbonized to obtain carbon materials, and then the carbon materials are treated by other methods to reduce the size of the carbon materials to reach the nanometer level. The invention patent (201510439569.2 a soybean-based carbon quantum dot and porous carbon material and preparation thereof) is that the crushed soybean is carbonized in inert gas at low temperature, the carbonized product is dipped in water, and then the supernatant is separated and purified to obtain the soybean-based carbon quantum dot. The invention patent (201510096178.5 a preparation method of biomass-based carbon quantum dots) carbonizes or activates biomass materials to obtain carbonized products, and nano-quantizes the carbonized products by adopting concentrated acid mixed liquor to obtain the water-soluble fluorescent carbon quantum dots. In the process of processing the carbon material, the method has the defects of complex process, high energy consumption, large environmental pollution, strong equipment corrosion and the like, and simultaneously has the defect of low yield of the carbon quantum dots caused by insufficient decomposition of the carbon material.
At present, the preparation operation process of biomass carbon quantum is complex, the energy consumption is high, the environmental pollution is large, the yield is low, and the large-scale production and application of the carbon quantum dot are limited. Therefore, the development of a simple, high-efficiency and high-yield biomass carbon quantum dot preparation method has very important significance and value.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide the preparation method of the biomass fluorescent carbon quantum dots, which has the advantages of low energy consumption, high yield, environmental protection, simple operation and low equipment cost.
The invention also aims to provide the substance fluorescent carbon quantum dot obtained by the preparation method.
The purpose of the invention is realized by the following technical scheme:
a preparation method of biomass fluorescent carbon quantum dots comprises the following steps:
(1) under the condition of room temperature, adding water into the biomass, the alkaline matter and the hydrogen peroxide for mixing to obtain a mixed solution, and stirring to obtain a transparent and clear carbon quantum dot solution;
the biomass is biomass hydrothermal coke or low-temperature carbonized biomass;
(2) and (2) filtering and dialyzing the carbon quantum dot solution obtained in the step (1) to obtain the purified water-soluble carbon quantum dot.
Preferably, the concentration of the hydrogen peroxide in the mixed solution in the step (1) is 0.001-1 g/mL.
More preferably, the concentration of the hydrogen peroxide in the mixed solution in the step (1) is 0.006-0.024 g/mL.
Preferably, OH in the mixed solution of step (1)—The concentration of (b) is 0.0001-5 mol/L.
More preferably, OH in the mixed solution of the step (1)—The concentration of (b) is 0.01-0.5 mol/L.
Preferably, the mass of the biomass hydrothermal coke or low-temperature carbonized biomass in the step (1) is 0.1-10% of the mass of the mixed solution.
The preparation method of the biomass fluorescent carbon quantum dot comprises the following steps of (1):
the biomass is used as a raw material, water is used as a solvent, and a black solid product which is not dissolved or dispersed in a solution is obtained by chemical reaction in a sealed pressure container.
Preferably, the preparation method of the low-temperature carbonized biomass in the step (1) comprises the following steps:
biomass is taken as a raw material and carbonized at the temperature of 150-350 ℃ in inert gas to obtain the low-temperature biomass carbon.
The biomass is at least one of glucose, fructose, xylose, glucosamine, citric acid, chitosan, chitin, hemicellulose and cellulose.
The biomass fluorescent carbon quantum dot is prepared by the preparation method of the biomass fluorescent carbon quantum dot.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) compared with the prior method for obtaining the carbon quantum dots by separating clear liquid, the method has high yield and can meet the requirement of large-scale production.
(2) The fluorescent carbon quantum dot prepared by the invention can emit blue visible light under the excitation of ultraviolet light and has good light resistance.
(3) The raw materials used in the preparation process are wide in source, cheap and easy to obtain.
(4) The preparation method of the invention fully utilizes the originally waste and cheap biomass hydrothermal coke and the low-temperature carbonized biomass carbon, and has the advantages of environmental protection.
(5) The preparation method of the invention has the advantages of cheap and easily available required medicines, low medicine concentration, little corrosion to equipment and little environmental pollution.
(6) The preparation process is simple, the required equipment is simple, and the cost is extremely low.
Drawings
FIG. 1 is a projection electron microscope image of carbon quantum dots prepared in example 1;
FIG. 2 is a graph showing a distribution of particle sizes of 252 quantum dots in a statistical TEM image of carbon quanta prepared in example 1;
FIG. 3 is a fluorescence spectrum of the quantum dot prepared in example 1;
FIG. 4 is a fluorescence spectrum of the quantum dot prepared in example 2;
FIG. 5 is a fluorescence spectrum of the quantum dot prepared in example 3;
FIG. 6 is a fluorescence spectrum of the quantum dot prepared in example 4;
FIG. 7 is a fluorescence spectrum of the quantum dot prepared in example 6;
FIG. 8 is a fluorescence spectrum of the quantum dot prepared in example 7;
FIG. 9 is a fluorescence spectrum of the quantum dot prepared in example 8;
fig. 10 is a fluorescence spectrum of the quantum dot prepared in example 9.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
Weighing glucose water-heat coke 0.1g, dispersing in 50mL NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.1mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering and dialyzing the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 97.9 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to a projection electron microscope, particle size distribution, and fluorescence spectrum characterization. The obtained carbon quantum dots are found to have good dispersibility in water, the diameter is 1-4nm, and the average diameter is 2.42nm (252 counts). The test results are shown in FIGS. 1, 2 and 3.
Example 2
Weighing glucose water-heat coke 0.1g, dispersing in 50mL NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.1mol/L, H2O2The concentration is 0.02g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 96.5 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 4.
Example 3
Weighing glucose water-heat coke 0.1g, dispersing in 50mL NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.05mol/L, H2O2The concentration is 0.02g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 43 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 5.
Example 4
Weighing 0.1g of glucosamine water-heat coke, dispersing in 50mL of NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.02mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 96.3 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 6.
Example 5
Weighing 0.1g of glucosamine water-heat coke, dispersing in 50mL of NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.02mol/L, H2O2The concentration is 0.02g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 44.5 percent.
Example 6
Weighing industrial hemicellulose hydrothermal coke 0.1g, and dispersing in 50ml of NaOH and H2O2In the mixed solution, the concentration of NaOH is 0.05mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 96.5 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 7.
Example 7
0.1g of chitosan water is weighed and dispersed in 50mLNaOH and H2O2In the mixed solution, the concentration of NaOH is 0.05mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. The prepared carbon quantum dotsAnd filtering, dialyzing and freeze-drying the solution to obtain the pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 97.3 percent.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 8.
Example 8
0.1g of cellulose hydrothermal coke is weighed and dispersed in 50mLNaOH and H2O2In the mixed solution, the concentration of NaOH is 0.1mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 93.4%.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 9.
Example 9
Weighing 0.1g of biomass carbon obtained by low-temperature carbonization of glucose and dispersing in 50mLNaOH and H2O2In the mixed solution, the concentration of NaOH is 0.1mol/L, H2O2The concentration is 0.01g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 76.9%.
The fluorescent carbon quantum dots obtained in this example were subjected to fluorescence spectrum characterization, and the test results are shown in fig. 10.
Example 10
Weighing 0.1g of biomass carbon obtained by low-temperature carbonization of glucose and dispersing in 50mLNaOH and H2O2In the mixed solution, the concentration of NaOH is 0.1mol/L, H2O2The concentration is 0.02g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 65.06%.
Example 11
Weighing 0.1g of biomass carbon obtained by low-temperature carbonization of glucose and dispersing in 50mLNaOH and H2O2MixingIn the solution, the concentration of NaOH is 0.05mol/L, H2O2The concentration is 0.02g/mL, and the mixture is fully stirred to obtain a brown clear fluorescent carbon quantum dot solution. And filtering, dialyzing and freeze-drying the prepared carbon quantum dot solution to obtain a pure fluorescent carbon quantum dot product. The yield of the fluorescent carbon quantum dots is 56.1 percent.
Ink experiments
0.005g of the fluorescent carbon quantum dot prepared in example 1 is weighed and dissolved in water, a sample is transferred to a 50mL volumetric flask, and a fluorescent ink aqueous solution with the concentration of 0.1mg/mL can be obtained after constant volume. Filtering and diluting fluorescent ink by using a microporous filter membrane, washing a common brush pen, washing the diluted fluorescent ink, writing on filter paper, naturally drying the ink, irradiating by using an ultraviolet lamp, and enabling the filter paper to present a light green pattern on a writing position. The fluorescent carbon quantum dots prepared by the method further prepare fluorescent ink, and the fluorescence has no obvious change and photobleaching property under the irradiation of ultraviolet light for a long time.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.