CN113789167B - Preparation method of room-temperature phosphorescent material based on carbon nano tube - Google Patents

Abstract

The invention discloses a preparation method of a room temperature phosphorescent material based on carbon nanotubes, which takes carboxylated single-wall carbon nanotubes as a main body, boric acid and urea as dispersion matrix precursors, the carbon nanotubes are embedded into a matrix, and hydrogen bonds and covalent bonds are formed at the interface between the carbon nanotubes and the matrix for microwave reaction, so as to prepare the room temperature phosphorescent material based on the nanotubes, and the material has the following characteristics: 1) Embedding the dispersed carboxylated single-wall carbon nanotubes into a matrix, and realizing room-temperature scaliness of the carbon nanotube base for the first time; 2) Hydrogen bond and covalent bond formed by carboxylated single-wall carbon nanotubes and matrix at the interface are important factors for realizing phosphorescence; 3) The service life reaches 476.6ms, and the macroscopic afterglow exceeds 4.0s; 4) The material is synthesized by one-step reaction, the raw materials are cheap, the operation is simple, no byproducts are generated, and the yield is close to 100%.

Description

A kind of preparation method of room temperature phosphorescent material based on carbon nanotube

technical field

The invention relates to the technical field of low-dimensional carbon nano-room temperature phosphorescence, in particular to a preparation method of a carbon nanotube-based room temperature phosphorescence material.

Background technique

Room-temperature phosphorescent materials have attracted increasing attention due to their fascinating optical properties for a wide range of applications in information security, optoelectronics, and biochemistry. Low-dimensional carbon materials are a general term for a class of materials that cannot be ignored in the field of room-temperature phosphorescent materials due to their unique geometry, tunable structure, good biocompatibility, environmental friendliness, and excellent optical and electronic properties. An important part of. Among them, the optical properties of single-walled carbon nanotubes have attracted much attention due to their wide application prospects. So far, several strategies to achieve photoluminescence of carbon nanotubes through dispersion and functionalization have been developed. One of the most common techniques is the sonication of nanotubes with surfactants in aqueous suspension, the adsorption of surfactant molecules to the sidewalls of dispersed SWCNTs produces electrostatically or sterically stabilized aqueous dispersions. , CNTs can be purified and separated by this liquid-phase method; in addition, photoluminescence has been observed by growing individual CNTs in zeolite channels.

Although the above studies have promoted the development of the optical properties of carbon nanotubes, their short luminescence lifetime (nanosecond level) limits the development and application of the optical properties of carbon nanotubes. Therefore, it is of great significance to develop a carbon nanotube-based room temperature phosphorescent material with long lifetime. At present, there are many studies on low-dimensional carbon nano-room temperature phosphorescent materials, mainly focusing on the room temperature phosphorescence of carbon quantum dots and graphene. Summarizing the reported literature, the most prominent challenges in the realization of low-dimensional carbon nano-room temperature phosphorescent materials are the lack of triplet excitons and non-radiative inactivation. The strategy they adopted is as follows: On the one hand, heteroatoms with empty p-orbitals (for example, N, P, F, and B) are introduced to narrow the energy level difference between the triplet and singlet states, thereby effectively filling the triplet excitons ; On the other hand, limit the rate of non-radiative transition by immobilization (formation of hydrogen bond, covalent bond, embedding matrix, etc.), and inhibit the non-radiative transition process.

Contents of the invention

The purpose of the present invention is to provide a method for preparing carbon nanotube-based room temperature phosphorescent material, which uses carboxylated single-walled carbon nanotubes as the main body, and obtains nanotube-based room temperature phosphorescent material by virtue of the synergistic fixation of hydrogen bonds and covalent bonds.

For reaching this purpose, the present invention adopts following technical scheme:

1. A preparation method of carbon nanotube-based room temperature phosphorescent material, with carboxylated single-walled carbon nanotubes as the main body, boric acid and urea as the dispersion matrix precursor, the specific steps are as follows:

1) Prepare an aqueous dispersion of carbon nanotubes. Disperse the carbon nanotubes in a sample bottle filled with deionized water for ultrasonic treatment, and let stand to obtain a uniform dispersion of carbon nanotubes in the upper layer, which is set aside.

2) Preparation and treatment of reaction solution. Add deionized water, boric acid, urea and the uniform carbon nanotube dispersion in step 1) into a clean 100ml small beaker, and ultrasonicate for 3-5min.

3) Place the small beaker containing the reaction solution in step 2) in a microwave oven for microwave reaction, the carbon nanotubes are embedded in the matrix, the carbon nanotubes and the matrix form hydrogen bonds and covalent bonds at the interface, and off-white solid powder is obtained.

4) After the reaction is completed, scrape the product in step 3) with a medicine spoon while it is hot, and quickly transfer it to a dry sample bottle, and keep it sealed.

2. A further technical solution, the carbon nanotubes in step 1) are carboxylated single-walled carbon nanotubes containing defects.

3. A further technical solution, in the step 1) the ultrasonic time is 2 hours, and the time is left to stand for 3 minutes.

4. further technical scheme, described step 2) in the mass ratio of boric acid and urea is about 1: 2, the amount of deionized water is enough to dissolve boric acid and urea.

5. Further technical scheme, the microwave reaction condition in described step 3) is: gear is high fire, and reaction time is 10min.

Compared with the prior art, the present invention has the following beneficial effects:

The dispersed carboxylated single-walled carbon nanotubes are embedded in the matrix, and the carbon nanotube-based room temperature phosphorescent material is realized for the first time; the hydrogen bond and covalency formed at the interface between the carboxylated single-walled carbon nanotubes and the matrix are important to realize phosphorescence. Factors; the lifespan reaches 476.6ms, and the afterglow of the naked eye exceeds 4.0s; the invention adopts a one-step reaction to synthesize the material, the raw material is cheap, the operation is simple, and there is no by-product, and the yield is close to 100%.

Description of drawings

Fig. 1 is a photograph of the room temperature phosphorescent material prepared in Example 1 of the present invention under sunlight, when the ultraviolet lamp is irradiated (fluorescence) and after the ultraviolet lamp is turned off (phosphorescence).

Fig. 2 is a topography diagram of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention under a high-magnification transmission electron microscope;

Fig. 3 a is the C 1s high-resolution X-ray photoelectron spectroscopy (XPS) comparison diagram of the phosphorescent material (c-CNT@BNO) and its matrix (BNO) prepared in Example 1 of the present invention, wherein the abscissa represents the binding energy, and the ordinate Indicates the relative photoelectron current intensity;

Figure 3b is a comparison chart of the Fourier transform infrared spectrum (FTIR) of the long afterglow material (c-CNT@BNO) and its matrix (BNO) prepared in Example 1 of the present invention, where the abscissa is the wave number, and the ordinate is the transmittance ( %);

Figure 4a is a comparison chart of the Fourier transform infrared spectrum (FTIR) of the long afterglow material (c-CNT@BNO) and its reactants (c-CNT, Urea and BA) prepared in Example 1 of the present invention, where the abscissa is the wave number, The ordinate is the transmittance (%);

Fig. 4 b is the B 1s high-resolution X-ray photoelectron spectrum (XPS) comparison diagram of the phosphorescent material prepared in Example 1 of the present invention, wherein the abscissa represents the binding energy or kinetic energy, and the ordinate represents the relative photoelectron current intensity;

Fig. 5a is the fluorescence and phosphorescence spectrogram of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention after being excited by 240nm (best excitation wavelength) ultraviolet light, wherein the abscissa is the wavelength, and the ordinate is the intensity;

Fig. 5b is a phosphorescence lifetime diagram of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention after being excited by 240nm (best excitation wavelength) ultraviolet light.

Fig. 6a is the UV-Vis absorption spectrum and phosphorescence excitation spectrum of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention.

Figure 6b is the fluorescence and phosphorescence spectra of the product obtained from the control experiment of hydroxylated carbon nanotubes, and the internal pictures are the optical pictures of the product under sunlight, ultraviolet light and when the ultraviolet lamp is turned off, respectively.

Detailed ways

In order to facilitate understanding of the present invention, the present invention enumerates the following examples. The examples are only to help the understanding of the present invention, and should not be regarded as specific limitations on the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Example 1

A method for preparing a carbon nanotube-based room temperature phosphorescent material, the specific steps are as follows:

1) Prepare an aqueous dispersion of carbon nanotubes. Excess carboxylated single-walled carbon nanotubes were dispersed in a wide-mouth sample bottle filled with 20ml of deionized water, ultrasonicated for 2 hours, and left to stand for 3 minutes for later use to obtain a uniform carbon nanotube dispersion in the upper layer.

2) Preparation and treatment of reaction solution. Add 13.5ml of deionized water, 0.6g of boric acid, 0.3g of urea, and 1.5ml of the uniform carbon nanotube dispersion in step 1) into a clean 100ml small beaker, and sonicate for 3-5min.

3) Put the small beaker containing the reaction solution in step 2) in a microwave oven for microwave reaction, the gear is set to high heat, and the reaction time is 10 minutes. An off-white solid powder was obtained.

4) After the reaction is completed, scrape the product with a medicine spoon while it is hot and quickly transfer it to a dry sample bottle, and keep it sealed.

The product was characterized as follows:

1. Take pictures of carbon nanotube-based room temperature phosphorescent materials under sunlight, when the UV lamp is irradiated and after the UV lamp is turned off

It appears as off-white powder under sunlight, emits blue fluorescence and green phosphorescence, and the phosphorescence can last for more than 4s.

2. Analysis of morphology, size and aggregation state of carbon nanotube-based room temperature phosphorescent materials by scanning electron microscope

Disperse the powder of the carbon nanotube-based room temperature phosphorescent material in step 4) into deionized water, and place it for 24 hours to ensure that it is dispersed to the greatest extent. Drop-coated on the micro-grid carbon film, dried, and scanned with a high-power transmission electron microscope. The test results are shown in Figure 2. From the picture, it can be seen that the carbon nanotubes are in a state of single dispersion under the action of the matrix.

3. Verify that the phosphorescent material prepared in Example 1 of the present invention has newly formed hydrogen bonds

As shown in Figure 3a, the C 1s binding energy of C=O is blue-shifted from 289.4eV to 289.6eV; The stretching vibration peaks (3435-3200cm ^-1 ) of BNO become stronger relative to their matrix (BNO). It shows that hydrogen bonds exist in nanotube-based room temperature phosphorescent materials.

4. Verify that the phosphorescent material prepared in Example 1 of the present invention has newly formed covalent bonds

The FTIR of phosphorescent materials can indicate the chemical bonds on the surface, as shown in Figure 4a, the corresponding chemical bonds can correspond to the raw materials used to synthesize nanoparticles, such as BO, NH, C in c-CNT, Urea and BA. =O and other chemical bonds. In addition, the absorption peak at 1250 ^cm may originate from newly formed BC bonds. B 1s high-resolution X-ray photoelectron spectroscopy showed that there were BO (193.1eV), BCO ₂ (192.6eV) and BN (190.8eV) bonds in the long afterglow powder. The two confirm each other, indicating that BC bonds are generated in the prepared phosphorescent material.

5. Using a steady-state/transient fluorescence spectrometer to test the optical properties of carbon nanotube-based room temperature phosphorescent materials

Fig. 5 a and Fig. 5 b are respectively the fluorescence, phosphorescence spectrogram and phosphorescence attenuation diagram of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention after being excited by ultraviolet light at the optimum excitation wavelength (240nm), and the optimum values of fluorescence and phosphorescence The emission wavelengths are 463nm and 480nm respectively, showing blue fluorescence and green phosphorescence; the phosphorescence lifetime is 476.6ms.

6. Analyze the luminescence source of carbon nanotube-based room temperature phosphorescent materials by comparing UV-Vis absorption spectrum and excitation spectrum and combining with control experiments

Fig. 6a is the UV-Vis absorption spectrum and phosphorescence excitation spectrum of the carbon nanotube-based room temperature phosphorescent material in Example 1 of the present invention. The absorption spectrum (dotted line) has a strong absorption peak at 240nm and a weak shoulder near 300nm, which are derived from the π-π* transition in the ^sp2 carbon of the typical graphene structure (C=C) and the carbonyl group on the carbon nanotube surface, respectively The n-π* transition of (C=O). The phosphorescence excitation spectrum (solid line) shows a narrow peak at 240 nm that highly overlaps the absorption region of the C=C bond, indicating that the triplet excited state is mainly derived from the π-π* transition on the localized ^sp2 -C subdomain; meanwhile, The overlap of the excitation peak near 355 nm with the weak shoulder near 300 nm in the absorption spectrum implies that the n-π* transition of C=O may be another source of phosphorescence. It has been demonstrated that C=O can effectively enhance the spin-orbit coupling and facilitate the generation of triplet excitons. In order to determine the key role of C=O in realizing carbon nanotube-based room temperature phosphorescence, a control experiment was carried out using hydroxylated carbon nanotubes (h-CNTs) instead of carboxylated carbon nanotubes (c-CNTs) in Example 1. Figure 6b is the fluorescence and phosphorescence spectra of the product obtained from the control experiment of hydroxylated carbon nanotubes, and the internal pictures are the optical pictures of the product under sunlight, ultraviolet light and when the ultraviolet lamp is turned off, respectively. Neither fluorescence nor phosphorescence was found, most likely due to the absence of C=O bonds in h-CNTs. The key role of C=O in realizing carbon nanotube-based room-temperature phosphorescence is demonstrated.

In summary, the luminescence of the carbon nanotube-based room-temperature phosphorescent material in Example 1 of the present invention has the above two sources.

Claims (2)

1. A preparation method of carbon nanotube-based room temperature phosphorescent material, characterized in that: taking carboxylated single-walled carbon nanotubes as the main body, boric acid and urea are dispersed matrix precursors, comprising the steps of: 1) dispersing the carboxylated single-walled carbon nanotubes in deionized water for ultrasonic treatment, and standing to obtain a uniform carboxylated single-walled carbon nanotube dispersion in the upper layer; 2) Add deionized water, boric acid, urea in a clean container to form a dispersed matrix precursor solution, the mass ratio of boric acid and urea is about 2:1, the amount of deionized water is enough to dissolve boric acid and urea; Step 1) The uniform carbon nanotube aqueous dispersion in the medium is mixed with the dispersed matrix precursor solution and subjected to ultrasonic treatment; 3) Place the container containing the reaction solution in step 2) in a microwave oven for microwave reaction, the carboxylated single-walled carbon nanotubes are embedded in the matrix, and the carboxylated single-walled carbon nanotubes and the matrix form hydrogen bonds and covalent bonds at the interface , to obtain an off-white solid powder; the covalent bond is a B-C bond. 2. The method for preparing a carbon nanotube-based room-temperature phosphorescent material as claimed in claim 1, characterized in that: in the step 1), the ultrasonic time is 2 hours, and the time for standing still is 3 minutes.

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