CN115246641A - Self-luminous fluorescent material in visible light region and preparation method thereof - Google Patents

Abstract

The invention discloses a self-luminous fluorescent material in a visible light region and a preparation method thereof, and the method comprises the following steps of adding primary CNTs into mixed acid of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid, stirring the mixture at room temperature by using a stirrer, and carrying out ultrasonic treatment to obtain uniform solution; adding a small amount of strong oxidant into the uniform solution for multiple times, heating, stirring and preserving heat for a period of time; and (3) performing cold quenching after the heat preservation time is finished: will contain 0.3% ₂ O ₂ Freezing the aqueous solution into ice, placing the ice into a beaker, adding the mixed solution, stirring, and adding a proper amount of H ₂ O ₂ Dropping into the slowly stirred reaction mixture with a dropper until no gas appears; carrying out centrifugal washing on the mixed solution, drying and collecting a product; the invention treats the carbon nano tube by a simpler method, and leads the untied multi-wall carbon nano tube fluorescent material to be in the state of not needing functionalization and adding fluorescent substancesLuminescence at 436nm and 467nm, and self luminescence verified with metal ions.

Description

Self-luminous fluorescent material in visible light region and preparation method thereof

technical field

The invention relates to the technical field of luminescence, in particular to a fluorescent material capable of self-luminescence of multi-walled carbon nanotubes in the visible light region under ultraviolet light irradiation and a preparation method thereof. The tube itself exhibited photoluminescence in the visible light region, and was verified as self-luminescence with metal ions.

Background technique

Carbon nanotubes, also known as bucky tubes, are one-dimensional quantum materials with a special structure (the radial dimension is in the order of nanometers, the axial dimension is in the order of micrometers, and both ends of the tube are basically sealed). Carbon nanotubes are mainly composed of several to dozens of layers of coaxial circular tubes of carbon atoms arranged in a hexagonal shape. Carbon nanotubes, as one-dimensional nanomaterials, are light in weight, have perfectly connected hexagonal structures, and possess many unusual electrical and optical properties. In recent years, with the in-depth research of carbon nanotubes and nanomaterials, their broad application prospects have also been continuously shown. The prior art "Research on the Fluorescence Properties of Functionalized Multi-Walled Carbon Nanotubes" reported that the carbon nanotubes were acidified to remove impurities by methods such as acid reflux, so that the carbon nanotubes were photoluminescent in the near-infrared region with low fluorescence intensity; or Carbon nanotubes can exhibit photoluminescence in the visible light region by functionalizing or adding fluorescent substances, but they cannot display photoluminescence in the visible light region.

Therefore, the prior art has shortcomings and needs to be improved.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a self-luminous fluorescent material in the visible light region and a preparation method thereof in view of the deficiencies of the prior art.

The technical scheme of the present invention is as follows:

A method for preparing a self-luminous fluorescent material in the visible light region, A1, adding the original CNTs to a mixed acid of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid, using a stirrer to stir the mixture at room temperature, and performing ultrasonic treatment to obtain Homogeneous solution; A2, adding a small amount of strong oxidant to the homogeneous solution for several times, heating, stirring, and holding for a period of time; A3, cold shock after the holding time is over: freeze the aqueous solution containing 0.3% H ₂ O ₂ into ice and put it into a beaker , add the mixed solution and stir with a glass rod, A4, drop an appropriate amount of H ₂ O ₂ into the slowly stirred reaction mixture with a dropper, until no gas appears; A5, the mixed solution is centrifuged and washed, and the product is collected by drying .

In the preparation method, in step A1, the volume ratios of concentrated sulfuric acid, concentrated nitric acid, and concentrated hydrochloric acid are respectively 1-5:1:1.

In the preparation method, in step A1, stirring is performed at room temperature for 10-30 minutes; the ultrasonic temperature is maintained at 40° C., and the ultrasonic time is 10 hours.

In the preparation method, in step A2, the added strong oxidant includes one of potassium permanganate, potassium dichromate and potassium chlorate, divided into 5-10 parts by mass, and added to the solution in 5-10 times, each time adding The mass is 0.04~0.2g, and the interval is 10~15min each time, heated to 50℃, and kept for 1~2h.

In the preparation method, in step A3, after the end of the holding time, the mixed solution is subjected to cold shock: the aqueous solution containing 0.3% H ₂ O ₂ is frozen into ice, placed in the mixed solution, and stirred.

In the described preparation method, in step A4, add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, and repeat this step several times until no gas appears.

In the preparation method, in step A5, the mixed solution is subjected to several centrifugal washings, after the first centrifugation of the mixed solution, the supernatant is poured off, and in the second centrifugation, the H ₂ SO ₄ solution is used to wash the first time. For the product obtained by the first centrifugation, the H ₂ SO ₄ solution is prepared with a volume ratio of distilled water and concentrated sulfuric acid of 1-3:1; The pH value of the solution is tested, and when the pH value is 6, the washing is completed, and the product is collected by drying to obtain a multi-walled carbon nanotube fluorescent material capable of self-luminescence in the visible light region.

In the preparation method, in step A5, the multi-walled carbon nanotube fluorescent materials with different diameters obtained by centrifugation at different rotational speeds of 5000-10000 r/min are uCNT-15, uCNT-23 and uCNT-45, respectively, and the corresponding average diameters are 10-20nm, 20-30nm and 30-50nm carbon nanotubes.

A multi-walled carbon nanotube fluorescent material capable of self-luminescence in the visible light region is obtained by any one of the methods; the diameter after unzipping is expanded to 30 nm to 60 nm; The tear edge carries a variety of oxygen-containing groups such as hydroxyl and carboxyl groups, which increase defects and increase the band gap value of carbon nanotubes. This structure enables carbon nanotubes to emit light in the visible light region, and the higher the oxygen content. , the more defects in the sample, the better the unzipping effect and the greater the fluorescence intensity. From the detected XPS data, it can be seen that the oxygen content of uCNT-15 is the highest.

Through the method of the present invention, the carbon nanotubes are treated by a relatively simple method, and without the need for functionalization and addition of fluorescent substances, the unwrapped multi-walled carbon nanotube fluorescent materials emit light at 436 nm and 467 nm, and metal ions are used. It was verified that it was self-luminous.

Description of drawings

Figure 1 shows the TEM images of the pristine multi-walled carbon nanotubes CNT-15 with the best disentanglement effect and the disentangled multi-walled carbon nanotubes fluorescent material uCNT-15.

FIG. 2 is the XPS spectra of pristine multi-walled carbon nanotubes and unwrapped multi-walled carbon nanotube fluorescent materials.

FIG. 3 is the excitation spectrum (a) and emission spectrum (b) of the unwrapped multi-walled carbon nanotube fluorescent material s.

FIG. 4 is a graph showing the fluorescence emission of the multi-walled carbon nanotube fluorescent material CNT-15 with the best disentanglement effect in the presence of different concentrations of different metal ions.

Figure 5 is a flow chart of the method of the present invention.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments.

Example 1

To the three-necked flask, add 36 ml of strong acid solution with a volume ratio of 1:1:1 of concentrated sulfuric acid: concentrated nitric acid: concentrated hydrochloric acid and 0.2 g of original multi-walled carbon nanotubes CNT-15 (CNT-15, CNT-23 and CNTs). -45, corresponding to carbon nanotubes with an average diameter of 10-20nm, 20-30nm and 30-50nm respectively), stirred at room temperature for 30min, then ultrasonicated for 10h, and the ultrasonic temperature was maintained at about 40°C. After ultrasonication, 5 parts of 0.2g potassium permanganate of the same mass were added at 10min intervals. After the addition of potassium permanganate was completed, the mixed solution was heated to 50°C and kept for 2h, with the temperature not exceeding 50°C. After the holding time is _over , perform cold shock _: freeze the aqueous solution containing 0.3% H2O2 into ice and put it into a beaker, add the mixed solution and stir with a glass rod. Add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, repeat the above operation of adding 0.2 ml of 30 % H ₂ O ₂ solution several times until no gas appears. Then, the mixed solution was centrifuged and washed several times. It should be noted that after centrifuging the mixed solution for the first time, the supernatant was poured out. In the second centrifugation, H ₂ SO ₄ solution (distilled water and concentrated The ratio of sulfuric acid was 1:1), which was used to wash the product obtained from the first centrifugation. The product obtained by the second centrifugation was subjected to several centrifugal washings with pure water, and the supernatant obtained by centrifugation was subjected to a pH test, and the pH value was 6. After washing, the product was dried and collected, and the CNTs and uCNTs of different diameters were collected. XPS test analysis.

Example 2

Add 36ml of strong acid solution and 0.2g of original multi-walled carbon nanotubes CNT-23 according to the volume ratio of concentrated sulfuric acid: concentrated nitric acid: concentrated hydrochloric acid to 2:1:1 into the three-necked flask, stir at room temperature for 20min, and maintain the ultrasonic temperature at About 40 ℃, and then ultrasonic for 10h. After ultrasonication, 5 parts of 0.2g potassium dichromate of the same mass were added at 10min intervals. After the addition of potassium dichromate was completed, the mixed solution was heated to 50°C, kept for 2h, and the temperature should not exceed 50°C. After the holding time is _over , perform cold shock _: freeze the aqueous solution containing 0.3% H2O2 into ice and put it into a beaker, add the mixed solution and stir with a glass rod. Add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, repeat the above operation of adding 0.2 ml of 30 % H ₂ O ₂ solution several times until no gas appears. Then, the mixed solution was centrifuged and washed several times. It should be noted that after centrifuging the mixed solution for the first time, the supernatant was poured out. In the second centrifugation, H ₂ SO ₄ solution (distilled water and concentrated The ratio of sulfuric acid was 2:1), which was used to wash the product obtained from the first centrifugation. The product obtained by the second centrifugation was subjected to multiple centrifugal washings with pure water, and the supernatant obtained by centrifugation was subjected to a pH test. The pH value was 6. After washing, the product was dried and collected. XPS analysis was performed on CNTs and uCNTs with different diameters.

Example 3

Add 36ml of strong acid solution and 0.2g of original multi-walled carbon nanotubes CNT-45 according to the volume ratio of concentrated sulfuric acid: concentrated nitric acid: concentrated hydrochloric acid to 3:1:1 into the three-necked flask, stir at room temperature for 10 minutes, and maintain the ultrasonic temperature at About 40 ℃, and then ultrasonic for 10h. After ultrasonication, 5 parts of 0.2g potassium chlorate of the same mass were added at 10min intervals. After the addition of potassium chlorate, the mixed solution was heated to 50°C and kept for 2h, with the temperature not exceeding 50°C. After the holding time is _over , perform cold shock _: freeze the aqueous solution containing 0.3% H2O2 into ice and put it into a beaker, add the mixed solution and stir with a glass rod. Add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, repeat the above operation of adding 0.2 ml of 30 % H ₂ O ₂ solution several times until no gas appears. Then, the mixed solution was centrifuged and washed several times. It should be noted that after centrifuging the mixed solution for the first time, the supernatant was poured out. In the second centrifugation, H ₂ SO ₄ solution (distilled water and concentrated The ratio of sulfuric acid was 2:1), which was used to wash the product obtained from the first centrifugation. The product obtained by the second centrifugation was subjected to multiple centrifugal washings with pure water, and the supernatant obtained by centrifugation was subjected to a pH test. The pH value was 6. After washing, the product was dried and collected. XPS analysis was performed on CNTs and uCNTs with different diameters.

The following is the relevant detection data of embodiment 1-3:

Figure 1 shows the TEM images of the pristine multi-walled carbon nanotubes CNT-15 with the best disentanglement effect and the disentangled multi-walled carbon nanotubes fluorescent material uCNT-15. The XPS test analysis of CNTs and uCNTs with different diameters shows that the oxygen content increases after the multi-walled carbon nanotubes are unzipped, and oxygen-containing groups are introduced. Differently, the greater the oxygen content, the higher the degree of unzipping. Figure 2 shows the XPS spectra of the original multi-wall carbon nanotubes and the unwrapped multi-wall carbon nanotube fluorescent materials.

The photoluminescence spectrum of the unwrapped multi-walled carbon nanotube fluorescent material was obtained at room temperature at an excitation wavelength of 331 nm. Figure 3 shows the excitation spectrum and emission spectrum of the unwrapped multi-walled carbon nanotube fluorescent material. The higher the oxygen content, the more defects in the sample and the greater the fluorescence intensity. It can be seen from the detected XPS data that uCNT-15 has the highest oxygen content. Select the multi-walled carbon nanotube fluorescent material CNT-15 with the best disentanglement effect, disperse it in pure water, and prepare the disentangled multi-walled carbon nanotube fluorescent material into an aqueous solution with a concentration of 0.024 mg/ml, respectively. Different concentrations of metal ions such as Zn ²⁺ , Co ²⁺ , Ni ²⁺ and Mn ²⁺ were added dropwise, and the fluorescence quenching of the disentangled multi-walled carbon nanotubes in the presence of different metal ions was compared. Fig. 4 is the fluorescence emission map of the multi-walled carbon nanotube fluorescent material CNT-15 with the best unraveling effect in the presence of metal ions such as Zn ²⁺ , Co ²⁺ , Ni ²⁺ and Mn ²⁺ at different concentrations.

Example 4

Add 36ml of strong acid solution and 0.2g of original multi-walled carbon nanotubes CNT-15 according to the volume ratio of concentrated sulfuric acid: concentrated nitric acid: concentrated hydrochloric acid to the three-necked flask, stir at room temperature for 30 minutes, and maintain the ultrasonic temperature at About 40 ℃, and then ultrasonic for 10h. After ultrasonication, 5 parts of 0.16g potassium permanganate of the same mass were added, with an interval of 10 minutes each time. After the addition of potassium permanganate was completed, the mixed solution was heated to 50 °C and kept for 2 hours, and the temperature should not exceed 50 °C. After the holding time is _over , perform cold shock _: freeze the aqueous solution containing 0.3% H2O2 into ice and put it into a beaker, add the mixed solution and stir with a glass rod. Add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, repeat the above operation of adding 0.2 ml of 30 % H ₂ O ₂ solution several times until no gas appears. Then, the mixed solution was centrifuged and washed several times. It should be noted that after centrifuging the mixed solution for the first time, the supernatant was poured out. In the second centrifugation, H ₂ SO ₄ solution (distilled water and concentrated The ratio of sulfuric acid was 3:1), which was used to wash the product obtained from the first centrifugation. The product obtained by the second centrifugation was subjected to multiple centrifugal washings with pure water, and the supernatant obtained by centrifugation was subjected to a pH test. The pH value was 6. After washing, the product was dried and collected.

Example 5

Add 36ml of strong acid solution and 0.2g of original multi-walled carbon nanotubes CNT-23 according to the volume ratio of concentrated sulfuric acid: concentrated nitric acid: concentrated hydrochloric acid to 5:1:1 into the three-necked flask, stir at room temperature for 20min, and maintain the ultrasonic temperature at About 40 ℃, and then ultrasonic for 10h. After the ultrasound, 5 parts of 0.12g potassium permanganate of the same mass were added, and the interval was 10 minutes each time. After the addition of potassium permanganate was completed, the mixed solution was heated to 50 °C, kept for 2 hours, and the temperature should not exceed 50 °C. After the holding time is _over , perform cold shock _: freeze the aqueous solution containing 0.3% H2O2 into ice and put it into a beaker, add the mixed solution and stir with a glass rod. Add 0.2 ml of 30% H ₂ O ₂ solution to the mixed solution, stir evenly with a glass rod, repeat the above operation of adding 0.2 ml of 30 % H ₂ O ₂ solution several times until no gas appears. Then, the mixed solution was centrifuged and washed several times. It should be noted that after centrifuging the mixed solution for the first time, the supernatant was poured out. In the second centrifugation, H ₂ SO ₄ solution (distilled water and concentrated The ratio of sulfuric acid was 3:1), which was used to wash the product obtained from the first centrifugation. The product obtained by the second centrifugation was subjected to multiple centrifugal washings with pure water, and the supernatant obtained by centrifugation was subjected to a pH test. The pH value was 6. After washing, the product was dried and collected.

It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (9)

1. A preparation method of a self-luminous fluorescent material in a visible light region is characterized by comprising the following steps of A1, adding primary CNTs into mixed acid of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid, stirring the mixture at room temperature by using a stirrer, and carrying out ultrasonic treatment to obtain uniform solution; a2, adding a small amount of strong oxidant into the uniform solution for multiple times, heating, stirring and preserving heat for a period of time; a3, during heat preservationAnd (3) performing cold quenching after the time is finished: will contain 0.3% of H ₂ O ₂ Freezing the aqueous solution into ice, placing the ice into a beaker, adding the mixed solution, stirring, A4, adding a proper amount of H ₂ O ₂ Dropping into the slowly stirred reaction mixture with a dropper until no gas appears; and A5, centrifugally washing the mixed solution, and drying to collect the product.

2. The method according to claim 1, wherein in step A1, the volume ratio of concentrated sulfuric acid, concentrated nitric acid, and concentrated hydrochloric acid is 1 to 5:1:1.

3. the preparation method according to claim 1, wherein in step A1, stirring is performed at room temperature for 10 to 30min; the ultrasonic temperature is maintained at 40 ℃ and the ultrasonic time is 10h.

4. The preparation method according to claim 1, wherein in the step A2, the added strong oxidant comprises one of potassium permanganate, potassium dichromate and potassium chlorate, the strong oxidant is added into the solution in 5-10 times according to 5-10 parts by mass, the mass of the added oxidant is 0.04-0.2 g each time, the interval between each time is 10-15 min, the solution is heated to 50 ℃, and the temperature is kept for 1-2 h.

5. The method according to claim 1, wherein in step A3, the mixed solution is quenched after the holding time is over: will contain 0.3% of H ₂ O ₂ The aqueous solution of (a) is frozen into ice and put into the mixed solution, and stirred.

6. The method according to claim 1, wherein 0.2ml of 30% H is added to the mixed solution in step A4 ₂ O ₂ The solution, stirred well with a glass rod, was repeated several times until no gas appeared.

7. The method according to claim 1, wherein in the step A5, the mixed solution is centrifugally washed a plurality of times, and after the mixed solution is centrifuged for the first time, the supernatant is centrifugedThe liquid is poured off and, during the second centrifugation, H is used ₂ SO ₄ Washing the product of the first centrifugation with a solution, H ₂ SO ₄ The solution is prepared by distilled water and concentrated sulfuric acid with the volume ratio of 1-3: 1; and (3) centrifugally washing the product obtained by the second centrifugation for 5-10 times by using distilled water, carrying out pH test on the supernatant obtained by the centrifugation, finishing the washing when the pH value is 6, drying and collecting the product, and thus obtaining the multi-walled carbon nanotube fluorescent material capable of self-illuminating in a visible light region.

8. The preparation method of claim 7, wherein in step A5, the multi-walled carbon nanotube fluorescent materials with different diameters are respectively uCNT-15, uCNT-23 and uCNT-45 obtained by centrifugation at different rotation speeds of 5000-10000 r/min, and the average diameters of the multi-walled carbon nanotube fluorescent materials are respectively 10-20nm, 20-30nm and 30-50 nm.

9. A multi-walled carbon nanotube fluorescent material capable of self-luminescence in the visible light region, obtained by the method of any one of claims 1 to 8; the diameter after untwisting is expanded to 30 nm-60 nm; the multi-wall carbon nanotube fluorescent material can carry various oxygen-containing groups such as hydroxyl and carboxyl on the torn edge by a zipper releasing method, so that the defects are increased, and the band gap value of the carbon nanotube can be increased.

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