CN109135738B - Waste tobacco stem-based nitrogen-doped carbon dots and synthesis method and application thereof - Google Patents
Waste tobacco stem-based nitrogen-doped carbon dots and synthesis method and application thereof Download PDFInfo
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Abstract
The invention provides a method for synthesizing nitrogen-doped carbon dots based on waste tobacco stems, which is prepared by taking the waste tobacco stems as a carbon source, taking water as a solvent to carry out hydrothermal reaction in a reaction kettle, and filtering, dialyzing, concentrating and drying after the reaction is finished. The surface of the nitrogen-doped carbon dot is rich in functional groups such as carboxyl, amino and the like, has an average particle size of about 4.7 nm, is good in water solubility, can emit bright fluorescence under the excitation of ultraviolet light, has a fluorescence emission behavior depending on excitation, and can be applied to aspects such as biological imaging as a fluorescence probe.
Description
Technical Field
The invention belongs to the technical field of carbon point synthesis, and particularly relates to a nitrogen-doped carbon point based on waste tobacco stems, a synthesis method and application thereof.
Background
The tobacco stems are byproducts of the cigarette industry and account for about 25-30% of the weight of the tobacco leaves. The tobacco stem has high content of cell wall substances, mainly comprises cellulose, hemicellulose, pectin and lignin, and also has various effective components such as nicotine, solanesol, chlorogenic acid, protein, amino acid and the like, thereby having high utilization value. However, due to the limitation of the prior art, tens of thousands of tons of tobacco stems are abandoned every year in China at present, and the environment is polluted while great resource waste is caused. Therefore, the development of new technology and the widening of high-valued utilization ways of tobacco stems become new research hotspots in the tobacco industry.
The carbon dots are carbon-based nano materials with at least one dimension below l0 nm and fluorescent properties. The carbon dots have the advantages of abundant raw material resources, excellent chemical inertness, high biocompatibility, good water solubility, adjustable emission spectrum, photobleaching resistance and the like, so the carbon dots have wide application prospects in the aspects of biological imaging, biological medicine, chemical sensing, photocatalysis, photoelectric devices and the like in recent years. The natural biomass material is rich in protein, sugar, fat and the like, and is an ideal green precursor for preparing carbon dots. The carbon dots prepared by adopting different carbon sources have different application potentials in the field of basic research due to different surface structures and fluorescence properties. The tobacco stems contain abundant carbohydrates, proteins and amino acids, a carbon source and a nitrogen source can be provided for preparing carbon dots, the reaction activity of the carbon dots can be increased by more active functional groups, and a new way is provided for recycling the tobacco stems. At present, no report related to the preparation of nitrogen-doped carbon dots by using waste tobacco stems is available.
Disclosure of Invention
The invention aims to provide nitrogen-doped carbon dots based on waste tobacco stems, which take stems rejected in cigarette production as carbon sources, and prepare the nitrogen-doped carbon dots with excellent luminescence property by adopting a one-step hydrothermal method, so that the effective utilization rate of the waste tobacco stems is improved, and the resource waste is reduced.
The invention also provides a synthetic method of the nitrogen-doped carbon dots of the waste tobacco stems and application of the nitrogen-doped carbon dots as a fluorescent probe in the aspect of biological imaging.
The invention adopts the following technical scheme:
a synthesis method of nitrogen-doped carbon dots based on waste tobacco stems is characterized in that waste tobacco stems are used as a carbon source, water is used as a solvent, hydrothermal reaction is carried out in a reaction kettle, and after the reaction is finished, the waste tobacco stems are filtered, dialyzed, concentrated and dried to obtain the nitrogen-doped carbon dots.
The method for synthesizing the nitrogen-doped carbon dots based on the waste tobacco stems comprises the following steps:
1) mixing the cleaned and dried tobacco stalk powder with distilled water, and performing hydrothermal reaction in a reaction kettle at the temperature of 190 ℃ and 210 ℃ for 5-15 hours;
2) after the reaction is finished, naturally cooling to room temperature, and filtering by using filter paper; dialyzing the obtained filtrate for at least 48 hours by using a dialysis membrane with the molecular weight cut-off of 100-500 Da to obtain a carbon point solution;
3) and carrying out rotary evaporation, concentration and freeze drying on the carbon dot solution to obtain brown carbon dot powder.
Specifically, in order to obtain a better hydrothermal reaction effect, in the step 1), the reaction conditions are that according to a feed-liquid ratio of 0.5-2 g: 10 mL of tobacco stem powder and distilled water are preferably added.
Preferably, in the step 2), the filter paper is 15-20 μm qualitative filter paper, so as to remove the particle phase precipitate better; the dialysis membrane was dialyzed for 72 hours.
The invention provides a nitrogen-doped carbon dot synthesized by the synthesis method.
The invention also provides application of the nitrogen-doped carbon dots as a fluorescent probe in biological imaging.
In order to reduce resource waste and improve the effective utilization rate of waste tobacco stems, the invention takes the rejected stems in the production of cigarettes as a carbon source, adopts a one-step hydrothermal method to prepare nitrogen-doped carbon points, and obtains the nitrogen-doped carbon points with excellent luminescence property by optimizing synthesis conditions. Compared with the prior art, the invention has the following beneficial effects:
1) the method takes the waste tobacco stems as a carbon source, and realizes nitrogen doping of carbon points and amino surface modification by a one-step hydrothermal method. The test shows that: the nitrogen-doped carbon dot has excellent water solubility and luminescence property, can emit bright blue fluorescence under the excitation of ultraviolet light, has fluorescence emission behavior depending on excitation, has the maximum excitation and emission wavelengths of 330 nm and 440 nm respectively, has the quantum yield of 7.4 percent, and can be used as a fluorescence probe to be applied to biological imaging and the like;
2) the synthetic method has mild process, environmental protection and easy operation, and opens up a new way for the comprehensive utilization of the tobacco stems.
Drawings
FIG. 1 is a high resolution TEM image (left) and a distribution image (right) of carbon dots;
FIG. 2 is an infrared absorption spectrum (left) and an X-ray photoelectron spectrum (right) of a carbon dot;
FIG. 3 shows the UV-visible absorption spectrum and the fluorescence emission spectrum of a carbon dot (excitation wavelength of 330 nm; the inset is a picture of the carbon dot in water under natural light (left) and ultraviolet light (right));
FIG. 4 is a three-dimensional fluorescence spectrum (left) of carbon dots and a fluorescence emission spectrum (right) at an excitation wavelength of 330-400 nm.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited thereto.
In the following examples, the main experimental instruments used are listed below:
BSA22AS model Single-disk electronic balance (Beijing Sidoolis instruments, Inc.), DHG-9030A model electric heating constant temperature forced air drying oven (Shanghai Jing Macro Experimental Equipment, Inc.), RE52CS model rotary evaporator (Shanghai Yangrong Biochemical Instrument Co., Ltd.), freeze dryer (Beijing Bo Yi kang Experimental Equipment, Inc.), F-7000 fluorescence spectrophotometer (Hitachi Ltd.), U-3900 ultraviolet visible spectrophotometer (Hitachi Ltd.), Nicolet-6700 model infrared spectrometer (Thermo Scientific), ESCALAB 250 photoelectron spectrometer (Thermo Scientific), JEM-2100F model field emission electron transmission electron microscope (JEOL), Hamamatsu Quantaurus-QY absolute fluorescence quantum yield (Hamamatsu Photonic spectrometer).
Example 1
A synthetic method of nitrogen-doped carbon dots based on waste tobacco stems comprises the following steps:
1) taking tobacco stems removed in the leaf shred winnowing process, cleaning, freeze-drying and grinding into powder;
2) weighing 0.5 g of tobacco stalk powder, adding 10 mL of distilled water, transferring to a 25 mL of hydrothermal reaction kettle with a polytetrafluoroethylene lining, and carrying out hydrothermal reaction for 10 hours at 200 ℃;
3) after the reaction is finished, naturally cooling to room temperature, and filtering by using qualitative filter paper with the diameter of 15-20 microns; dialyzing the obtained filtrate for 72 hours by using a dialysis membrane with the molecular weight cutoff of 100-500 Da to obtain a carbon point solution;
3) and (4) carrying out rotary evaporation and concentration on the carbon dot solution, and carrying out freeze drying by a freeze dryer to obtain brown nitrogen-doped carbon dot powder.
And (5) characterizing the structure and the performance of the carbon dots.
(1) Characterization by a high-resolution transmission electron microscope:
FIG. 1 shows a high-resolution transmission electron micrograph (left) and a particle size distribution chart (right) of carbon dots. As shown in fig. 1, the nitrogen-doped carbon dots prepared by the waste stipe are in a quasi-spherical shape with uniform dispersion, and no obvious lattice stripe is observed, and the nitrogen-doped carbon dots are in an amorphous structure; the particle size distribution is 2-8 nm, the particle size distribution is narrow and symmetrical, and the average particle size is about 4.7 nm through statistical calculation.
(2) Infrared absorption spectrum and X-ray photoelectron spectroscopy:
FIG. 2 shows an infrared absorption spectrum (left) and an X-ray photoelectron spectrum (right) of a carbon dot. From the X-ray photoelectron spectrum, it can be seen that: the carbon dots contain three elements of carbon, nitrogen and oxygen, and the high content of the elements of nitrogen and oxygen means that the prepared sample is the carbon dots which are rich in oxygen and doped with nitrogen. 3375 cm in the infrared absorption spectrum-1And 3265 cm-1Absorption peaks at (A) are respectively assigned to-OH and-NH2Symmetrical stretching vibration peaks of (1); 2920 cm-1And 2855 cm-1The peak is the asymmetric and symmetric stretching vibration peak of C-H; 1600 cm-1The bending vibration peak of N-H is positioned; 1680 cm-1And 1120 cm-1The stretching vibration peaks of C = O and C-O, respectively; 1295 cm-1And 1395 cm-1The stretching vibration peaks of C-N and C = N, respectively. The carbon dot surface is rich in-OH, -NH2And a functional group such as-COOH, so that it has excellent water dispersibility.
(3) Optical characterization of carbon dots:
FIG. 3 shows the UV-visible absorption spectrum and the fluorescence emission spectrum of a carbon dot (excitation wavelength of 330 nm; the inset shows a picture of an aqueous solution of a carbon dot under natural light (left) and ultraviolet light (right)). As shown in FIG. 3, the transition absorption of pi-pi of the conjugated double bond and the transition absorption of n-pi of the carbonyl group and pyridine nitrogen in the carbon dot structure cause ultraviolet absorption in the range of 240 to 290 nm. Under the irradiation of an ultraviolet lamp, the carbon dot aqueous solution emits bright blue fluorescence; when the excitation wavelength is 330 nm, the fluorescence emission intensity of the carbon dots is maximum, the emission peak is positioned at 440 nm, and the measured quantum yield is about 7.4%.
(4) Fluorescence properties of carbon dots:
FIG. 4 is a three-dimensional fluorescence spectrum (left) of carbon dots and a fluorescence emission spectrum (right) at an excitation wavelength of 330-400 nm. The three-dimensional fluorescence spectra and emission spectra at different excitation wavelengths in fig. 4 show: as the excitation wavelength is shifted from 330 nm to 400 nm, the maximum emission wavelength is red-shifted from 440 nm to 500 nm, and the fluorescence intensity gradually decreases. The particle size of the prepared carbon dots is not uniformly distributed, and the surface energy defect sites are more, so that the phenomenon of depending on the change of the excitation wavelength is caused, and meanwhile, the excitation-dependent emission characteristic provides a theoretical basis for multicolor imaging of the carbon dots.
Example 2
A synthetic method of nitrogen-doped carbon dots based on waste tobacco stems comprises the following steps:
1) mixing cleaned and dried tobacco stalk powder and distilled water according to a material-liquid ratio of 1 g: 10 mL of the mixture is subjected to hydrothermal reaction in a reaction kettle at 190 ℃ for 12 hours;
2) after the reaction is finished, naturally cooling to room temperature, and filtering by using qualitative filter paper with the diameter of 15-20 microns; dialyzing the obtained filtrate for 72 hours by using a dialysis membrane with the molecular weight cutoff of 100-500 Da to obtain a carbon point solution;
3) and (4) carrying out rotary evaporation and concentration on the carbon dot solution, and carrying out freeze drying by a freeze dryer to obtain brown carbon dot powder.
Example 3
A synthetic method of nitrogen-doped carbon dots based on waste tobacco stems comprises the following steps:
1) mixing cleaned and dried tobacco stalk powder with distilled water according to a material-liquid ratio of 2 g: 10 mL of the mixture is subjected to hydrothermal reaction for 6 hours in a reaction kettle at the temperature of 210 ℃;
2) after the reaction is finished, naturally cooling to room temperature, and filtering by using qualitative filter paper with the diameter of 15-20 microns; dialyzing the obtained filtrate for 72 hours by using a dialysis membrane with the molecular weight cutoff of 100-500 Da to obtain a carbon point solution;
3) and (4) carrying out rotary evaporation and concentration on the carbon dot solution, and carrying out freeze drying by a freeze dryer to obtain brown carbon dot powder.
In conclusion, the waste peduncles rejected in the cigarette production are used as carbon sources, the nitrogen-doped carbon dots are prepared by a one-step hydrothermal method, the surfaces of the nitrogen-doped carbon dots are rich in functional groups such as carboxyl groups, amino groups and the like, the water solubility is good, bright blue fluorescence can be emitted under the excitation of ultraviolet light, and the nitrogen-doped carbon dots have fluorescence emission behaviors depending on the excitation, and can be used as fluorescence probes to be applied to aspects such as biological imaging and the like. In the synthesis process, other reagents are not required to be added, the method is environment-friendly and easy to operate, byproducts in the cigarette processing process are effectively utilized, and a new way is provided for high-value utilization of the tobacco stems.
Finally, it should be noted that: the above embodiments are merely illustrative and not restrictive of the technical solutions of the present invention, and any equivalent substitutions and modifications or partial substitutions made without departing from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.
Claims (4)
1. The nitrogen-doped carbon dots based on the waste tobacco stems are characterized by being synthesized through the following steps:
1) mixing the cleaned and dried tobacco stalk powder with distilled water, and performing hydrothermal reaction in a reaction kettle at the temperature of 190 ℃ and 210 ℃ for 6-12 hours;
2) after the reaction is finished, naturally cooling to room temperature, and filtering by using filter paper; dialyzing the obtained filtrate for at least 48 hours by using a dialysis membrane with the molecular weight cut-off of 100-500 Da to obtain a carbon point solution;
3) the carbon dot solution is obtained by rotary evaporation, concentration and freeze drying;
the obtained nitrogen-doped carbon dots are in a uniformly dispersed quasi-spherical shape, and an amorphous structure, wherein no obvious lattice stripe is observed; the particle size distribution is 2-8 nm, the particle size distribution is narrow and symmetrical, and the average particle size is 4.7 nm through statistical calculation.
2. The nitrogen-doped carbon dot based on the waste tobacco stems as claimed in claim 1, wherein in the step 1), the nitrogen-doped carbon dot based on the waste tobacco stems is prepared by mixing the following components in a material-to-liquid ratio of 0.5-2 g: 10 mL of tobacco stem powder and distilled water were added.
3. The nitrogen-doped carbon dot based on the waste tobacco stems as claimed in claim 1, wherein in the step 2), the filter paper is qualitative filter paper with the diameter of 15-20 μm; the dialysis membrane was dialyzed for 72 hours.
4. Use of the nitrogen-doped carbon dot of claim 1 as a carbon-based nanomaterial with fluorescent properties.
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| CN109929550A (en) * | 2019-04-16 | 2019-06-25 | 山西大学 | A kind of N doping blue-fluorescence carbon quantum dot and its preparation method and application |
| CN110054171A (en) * | 2019-04-25 | 2019-07-26 | 贺州学院 | A kind of preparation method of biomass near-infrared fluorescent carbon dots |
| CN110104629A (en) * | 2019-05-20 | 2019-08-09 | 河南师范大学 | The method for synthesizing fluorescent carbon point as raw material one step hydro thermal method using wild gleditsia sinensis |
| CN110155984B (en) * | 2019-06-12 | 2021-02-02 | 浙江科技学院 | Method for synthesizing biomass fluorescent carbon dots by hydrothermal method with soybean dregs as raw material and application |
| CN113287782A (en) * | 2021-02-01 | 2021-08-24 | 云南中烟工业有限责任公司 | Carboxylated carbon-based adsorbent for cigarette filter tip and preparation method and application thereof |
| CN113148979B (en) * | 2021-02-05 | 2022-11-08 | 贵州省烟草科学研究院 | Method for preparing carbon dots with different colors under same wavelength by using tobacco waste and application |
| CN114137048B (en) * | 2021-06-28 | 2024-03-12 | 中北大学 | Preparation method and application of nitrogen-doped graphene quantum dot with sunflower pectin as carbon source |
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| CN106967425A (en) * | 2016-11-23 | 2017-07-21 | 云南省烟草公司文山州公司 | Using cigarette stalk as the preparation method and application of the fluorescent carbon quantum dot of raw material |
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| CN106967425A (en) * | 2016-11-23 | 2017-07-21 | 云南省烟草公司文山州公司 | Using cigarette stalk as the preparation method and application of the fluorescent carbon quantum dot of raw material |
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| Carbon dots derived from tobacco for visually distinguishing and detecting three kinds of tetracyclines;Miao Hong;《Nanoscale》;20180404;第10卷(第17期);第8140页右栏倒数第1段-8141页左栏第1段，图1(A) * |
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