CN113372910A

CN113372910A - Yellow carbon dot with high photo-thermal stability and preparation thereof

Info

Publication number: CN113372910A
Application number: CN202110757948.1A
Authority: CN
Inventors: 杨永珍; 何品一; 郑静霞; 刘旭光; 许并社
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2021-07-05
Filing date: 2021-07-05
Publication date: 2021-09-10
Anticipated expiration: 2041-07-05
Also published as: CN113372910B

Abstract

The invention relates to a yellow carbon dot with high photo-thermal stability, which is a carbon dot solution obtained by carrying out solvothermal reaction on trimesic acid serving as a carbon source and o-phenylenediamine serving as a nitrogen source in absolute ethyl alcohol. The yellow carbon dots prepared by the method have bright yellow emission and high light stability and thermal stability. The yellow carbon point fluorescent film is mixed with KH-792 and cured to obtain the yellow carbon point fluorescent film which can be used for preparing high-energy white light LD devices and is compounded with 450nm blue light LD to realize pure white light laser illumination.

Description

Yellow carbon dot with high photo-thermal stability and preparation thereof

Technical Field

The invention belongs to the technical field of fluorescent luminescent materials, relates to a fluorescent carbon dot, and particularly relates to a fluorescent carbon dot with high light stability and thermal stability and a preparation method of the fluorescent carbon dot.

Background

As a novel solid-state lighting device, a Laser Diode (LD) has high light-emitting efficiency, a long visible light distance, and a fast response speed, and meanwhile, there is no "light efficiency dip" phenomenon, which is a new rising star in the solid-state lighting field in the future.

LD mainly includes two ways to realize white light illumination. One is to use lasers with different light emitting colors to carry out matching combination, and the light emitted by the lasers forms white light after being compounded. The color rendering index of the method is high, but the light path design is complex, the equipment cost is high, and the light color is not easy to regulate and control, so that the further development of the method is limited. The other is to realize white light emission by combining a blue laser and a yellow fluorescent material, and the mode has the advantages of low manufacturing cost, easy regulation and control of light emission, stable light emitting performance and the like, so the mode is favored by researchers.

However, since the irradiation energy of the LD light source is high, the fluorescent material used in combination with the LD light source is required to have excellent stability. At present, the fluorescent material mainly applied to the LD device is a rare earth-based fluorescent material, which has good stability and mature synthesis process, but has the defects of resource shortage and non-regeneration. Therefore, the development of a green and environment-friendly fluorescent material with good stability is imperative.

Carbon Dots (CDs) as a novel fluorescent material have the advantages of low toxicity, environmental protection, high chemical inertness, adjustable light-emitting wavelength, good stability, wide raw material source and the like. However, most CDs have poor photo-thermal stability and crystallinity, and thus tend to undergo fluorescence quenching when used for LD illumination.

Liu et al (Orange, yellow and blue luminescence carbon dots controlled by y surface state for multicolor cellular imaging, light emission and irradiation [ J]. Mikrochimica Acta2018, 185(12): 539.) the CDs are prepared by a microwave-assisted method by using phenylenediamine as a starting material and formamide as a solvent, but the change of the fluorescence intensity of the CDs under the irradiation of a 365nm UV lamp is large, and the fluorescence stability needs to be improved.

Ding et al (Solvent-cont)rolled synthesis of highly luminescent carbon dots with a wide color gamut and narrowed emission peak widths[J]. Small14(22): 1800612.) CDs are synthesized by a solvothermal method by using o-phenylenediamine and L-glutamic acid as starting materials and formamide, N-dimethylformamide, ethanol and the like as solvents, but the XRD diffraction peak is wide and the crystallinity needs to be further improved.

Disclosure of Invention

The invention aims to provide a yellow carbon dot with high photo-thermal stability and a preparation method of the yellow carbon dot. The carbon dot solution prepared by the invention has bright yellow light emission, and can realize pure white laser illumination by being compounded with a 450nm blue light LD after being cured into a film.

The yellow carbon dot with high photo-thermal stability is a carbon dot solution obtained by carrying out solvothermal reaction on trimesic acid serving as a carbon source and o-phenylenediamine serving as a nitrogen source in absolute ethyl alcohol.

The carbon dot solution prepared by the invention emits bright yellow light under the irradiation of an ultraviolet lamp, and the test shows that the fluorescence Quantum Yield (QY) is 26.37%, so that the requirement of a high-quality white light laser lighting device can be met.

The yellow carbon dot solution has the excitation independent characteristic and higher performancesp ²The conjugation degree, the crystallinity of the yellow carbon dots in the solid state is good, the thermal stability is high, and the yellow carbon dots can bear the high temperature of 250 ℃.

The invention adopts trimesic acid and o-phenylenediamine as starting materials to prepare the yellow carbon dots, on one hand, the yellow carbon dots have higher contentsp ²The conjugated carbon structure is more favorable for forming carbon points with high crystallization degree; meanwhile, the trimesic acid has a carboxyl group, the o-phenylenediamine has an amino group, and the high stability of carbon dots can be obtained by crosslinking benzene rings together through amidation reaction in the solvent thermal reaction process due to the high reactivity between the amino group and the carboxyl group.

Furthermore, the invention provides a preparation method of the yellow carbon dots with high photo-thermal stability, which is characterized by dissolving trimesic acid and o-phenylenediamine solid powder in absolute ethyl alcohol, heating the mixture in a high-pressure reaction kettle in a sealed manner to 180-220 ℃ for solvent thermal reaction, and preparing a yellow brown yellow carbon dot solution.

Further, the preparation method of the invention also comprises a purification treatment of the yellow carbon dot solution. Preferably, the prepared yellow light carbon dot solution is placed in a dialysis bag with the molecular weight cutoff of 500Da and is subjected to dialysis purification treatment in absolute ethyl alcohol.

In the above production method of the present invention, the preferable molar ratio of trimesic acid to o-phenylenediamine is 1: 1.

In the preparation method, more specifically, the solvothermal reaction time is 8-12 h.

Furthermore, the invention also discloses a yellow light carbon dot fluorescent film prepared by using the prepared yellow light carbon dot solution, and specifically, the yellow light carbon dot fluorescent film with high photo-thermal stability is obtained by mixing the prepared yellow light carbon dot solution with a silanization coupling agent N-beta-aminoethyl-gamma-aminopropyltrimethoxysilane (KH-792) to form a film.

More specifically, KH-792 and deionized water are added into the absolute ethyl alcohol solution of the yellow carbon dots after dialysis purification treatment, and after uniform mixing, the mixture is dropwise added onto a sapphire glass sheet, and after curing, the yellow carbon dot fluorescent film is obtained.

The yellow carbon dot fluorescent film prepared by the invention can be used for preparing a high-energy white light LD device.

The yellow carbon dot fluorescent film prepared by the invention is compounded with a blue LD with the wavelength of 450nm, and the pure white laser illumination can be realized.

The yellow carbon dot solution prepared by the invention has no change in fluorescence intensity under long-term UV lamp irradiation, and has excellent fluorescence stability.

Furthermore, the yellow carbon dot solution prepared by the invention is subjected to rotary evaporation treatment, and after the solvent absolute ethyl alcohol is removed, brown carbon dot solid powder is obtained, and has no weight loss phenomenon at the high temperature of 200 ℃, the weight loss amount at the high temperature of 250 ℃ is only 4.63%, and the yellow carbon dot solution has excellent thermal stability.

Therefore, the yellow carbon dots with high photo-thermal stability, which are prepared by the invention, are cured into films and then applied to the white light LD illuminating device, so that the potential of the high-crystallinity carbon dots as a novel laser fluorescent material is effectively proved, and a brand-new solution is provided for realizing white light illumination by a laser.

Drawings

FIG. 1 is a TEM image and a particle size distribution histogram of a yellow carbon dot prepared in example 1.

Figure 2 is an XRD diffractogram of the yellow carbon spot prepared in example 1.

FIG. 3 is the FTIR spectrum of the yellow carbon spot prepared in example 1 and the starting materials trimesic acid and o-phenylenediamine.

FIG. 4 is an XPS plot of the yellow carbon dots produced in example 1.

FIG. 5 is a QY measurement curve of an emission spectrum of a yellow carbon dot ethanol solution at different excitation wavelengths and the yellow carbon dot.

FIG. 6 is a graph showing the fluorescence intensity of a yellow carbon dot ethanol solution as a function of UV irradiation time.

FIG. 7 is the emission spectrum and fluorescence intensity of the yellow carbon dot fluorescent film prepared in example 2 at different excitation wavelengths as a function of UV irradiation time.

FIG. 8 is a thermogravimetric plot of a yellow carbon dot solid powder and a yellow carbon dot fluorescent thin film.

FIG. 9 is an FTIR spectrum of KH-792 and a yellow carbon dot fluorescent film.

Fig. 10 is a graph of emission spectra and color coordinates of a device at different operating voltages for a white LD device based on a yellow carbon dot fluorescent film of application example 1.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are only for more clearly illustrating the technical solutions of the present invention so as to enable those skilled in the art to better understand and utilize the present invention, and do not limit the scope of the present invention.

The names and abbreviations of the experimental methods, production processes, instruments and equipment involved in the examples and comparative examples of the present invention are those commonly known in the art and are clearly and clearly understood in the relevant fields of use, and those skilled in the art can understand the conventional process steps and apply the corresponding equipment according to the names and perform the operations according to the conventional conditions or conditions suggested by the manufacturers.

The various starting materials or reagents used in the examples of the present invention and comparative examples are not particularly limited in their sources, and are all conventional products commercially available. They may also be prepared according to conventional methods well known to those skilled in the art.

The following examples are only preferred embodiments of the present invention and are not intended to limit the present invention in any way. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Example 1.

0.42g of trimesic acid and 0.21g of o-phenylenediamine are weighed, added into 30mL of absolute ethyl alcohol, dissolved uniformly by ultrasonic, placed into a 100mL reaction kettle, and subjected to solvothermal reaction for 10 hours in an oven at 200 ℃. And after the reaction is finished, air cooling to room temperature to obtain a tan carbon dot solution.

And (3) taking out the carbon dot solution, filtering the carbon dot solution by using a 0.22-micron filter membrane, putting the filtrate into a 500Da dialysis bag, and carrying out dialysis treatment in absolute ethyl alcohol for 48 hours, wherein the absolute ethyl alcohol is replaced every 8 hours in the dialysis bag so as to remove fluorescent small molecules and other impurities in the filtrate, thus preparing the yellow carbon dot with high photo-thermal stability.

In this embodiment, the morphology structure and the particle size distribution of the prepared yellow carbon dots are characterized by TEM. The morphology of the yellow carbon dots is shown in fig. 1(a), and the yellow carbon dots are spherical, are uniformly dispersed and have no agglomeration phenomenon. FIG. 1(b) shows that the yellow carbon dots have a particle size distribution of 1.5-4.5 nm and an average particle size of 2.89 nm.

From the HRTEM image in the inset of fig. 1(a), it can be seen that the yellow carbon dots have very distinct lattice fringes with an interplanar spacing of 0.21 nm. The obvious lattice stripes of yellow carbon points indicate that the crystal has higher crystallization degree, indicating higher stability.

And (3) carrying out rotary evaporation treatment on the prepared yellow carbon dot product, removing the solvent absolute ethyl alcohol to obtain tan carbon dot solid powder, and carrying out various performance characterizations on the yellow carbon dot.

Fig. 2 further analyzed the crystallinity of the prepared yellow carbon dots by XRD characterization. In fig. 2, a very sharp diffraction peak appears at a diffraction angle of 26.5 °, which corresponds to the (002) crystal face of graphite, and the narrow half-peak width thereof fully proves that the yellow carbon dot has a very high degree of crystallinity, which is consistent with the characterization result in HRTEM, and the high-crystallinity yellow carbon dot has a high photo-thermal stability, and can be better applied to the field of high-energy laser illumination.

Fig. 3 analyzes the chemical composition and the functional group property of the prepared yellow carbon dot surface by FTIR. In the figure, 1240cm⁻¹Is C ‒ O symmetric stretching vibration peak, 1371cm⁻¹C ‒ N stretching vibration peak of amido bond, 1620cm⁻¹Is the C ═ C stretching vibration peak, 1720cm⁻¹The peak of C ═ O stretching vibration is 3420cm⁻¹The vibration peaks are N ‒ H and O ‒ H stretching vibration peaks. The C ‒ N stretching vibration peak shows that nitrogen is successfully doped into the yellow carbon dots through amidation reaction, and the O ‒ H stretching vibration peak shows that the yellow carbon dots have better water solubility, thereby being beneficial to the hydrolysis reaction in the subsequent film-forming process.

Further analysis of the elemental composition and surface structure of the yellow carbon dot using XPS showed 3 distinct energy level peaks in the XPS survey scan of fig. 4(a), C1s (284.77eV), N1s (399.09eV), and O1s (532.13eV), respectively, with the stronger C1s and O1s peaks indicating that the yellow carbon dot consists primarily of carbon and oxygen, and the weaker N1s peak indicating nitrogen doping of the yellow carbon dot, forming a new surface state.

The high resolution C1s spectrum of FIG. 4(b) shows C ═ C (284.28eV), C ‒ N (285.02eV), C ‒ O (286.25eV), C ═ O (288.88eV), and the aromatic structure π ‒ π^*The existence of concomitant peaks (291.34eV), wherein C ‒ N indicates that nitrogen participates in the formation of yellow carbon dots.

The existence of pyridine nitrogen (398.49eV), amino nitrogen (399.47eV) and pyrrole nitrogen (400.44eV) in the high-resolution N1s spectrum (FIG. 4(c)) indicates that nitrogen is doped into the yellow carbon dot through amidation reaction between amino and carboxyl on the benzene ring, and the doping of nitrogen effectively increases the electron cloud density on the surface of the yellow carbon dot, thereby facilitating the yellow carbon dot to realize long-wavelength emission.

And C ═ O (531.71eV) and C ‒ O (533.24eV) of the high resolution O1s spectrum in FIG. 4(d) demonstrate the existence of carboxyl and hydroxyl, which makes the yellow carbon dot have good water solubility, and the characterization result is consistent with the FTIR result.

And (3) taking a proper amount of carbon dot solid powder, dissolving the carbon dot solid powder in absolute ethyl alcohol again to obtain a yellow carbon dot solution, and inspecting the optical characteristics of the yellow carbon dot solution. In the emission spectrum of the yellow carbon dot of fig. 5(a), when the excitation wavelength is increased from 365nm to 465nm, the emission wavelength is kept unchanged at 532nm, and the characteristic of obvious independent fluorescence excitation is shown, so that the uniform particle size of the yellow carbon dot is laterally verified.

According to the upper left inset, the yellow carbon dot solution under the irradiation of the fluorescent lamp is yellowish, and under the ultraviolet lamp, bright yellow light emission is shown.

And (3) measuring the fluorescence quantum yield QY of the yellow carbon dot solution under the excitation wavelength of 420nm by using rhodamine 6G as a standard substance and adopting a relative method. In FIG. 5(b), the QY value of the ethanol solvent of rhodamine 6G under the test conditions is 95%, and the QY value of the yellow light carbon dot solution is 26.37%.

In the field of laser illumination, the fluorescent conversion material needs to have higher fluorescence stability. In this example, a 150W xenon lamp source having a wavelength of 365nm was used to continuously irradiate the yellow carbon dot solution with UV light to evaluate the light resistance of the yellow carbon dot solution.

Under the UV irradiation lasting as long as 60min in FIG. 6, the fluorescence intensity of the yellow carbon dot solution remains unchanged, which proves the excellent fluorescence stability and laterally proves the higher crystallinity of the yellow carbon dot.

Example 2.

8mg of the carbon dot solid powder prepared in example 1 was weighed, 1mL of absolute ethanol was added, after the powder was sufficiently dissolved, 1mL of silane coupling agent KH-792 and 0.5mL of deionized water were continuously added to the solution, and the solution was uniformly mixed by sonication for 5min to obtain a clear brown solution.

Adding the solution into a weighing bottle with the specification of 25 multiplied by 25mm, and drying in an oven at 50 ℃ for 4 hours.

After the solution in the weighing bottle becomes viscous, dropwise adding the solution onto a sapphire glass sheet, placing the sapphire glass sheet in an oven at the temperature of 60 ℃, and curing after 8 hours to form a yellow carbon dot fluorescent film with bright yellow emission.

The optical properties of the above-prepared yellow carbon dot fluorescent film were examined under the same conditions. In the emission spectrum of the yellow carbon dot fluorescent film in fig. 7(a), as the excitation wavelength is increased from 365nm to 485nm, the fluorescence emission peak position is still 532nm, which remains unchanged, and the film shows the same excitation independent fluorescence characteristic as the solution state, which indicates that the fluorescence property of the yellow carbon dot is not changed by using the film forming agent.

As is evident from the upper left inset, the yellow carbon dot phosphor film appears dark brown under fluorescent light illumination and bright yellow emission under an ultraviolet lamp.

Since the yellow carbon dot fluorescent thin film is to be used as a fluorescent conversion material in an LD with high energy and concentrated light beam, the fluorescent thin film is required to have high fluorescence stability.

The light resistance of the yellow carbon fluorescent film was evaluated by continuous UV irradiation under the same conditions using a xenon lamp light source. FIG. 7(b) shows that the fluorescence intensity of the yellow carbon dot fluorescent film is not changed under UV irradiation lasting for 60min, which proves the excellent fluorescence stability of the yellow carbon dot, and benefits from the high fluorescence stability of the yellow carbon dot.

Further, since the operating temperature of an LD is high, usually about 250 ℃, the yellow carbon dot fluorescent thin film used in combination as a fluorescent conversion material needs to have high fluorescence stability and also high thermal stability.

FIG. 8(a) shows the thermogravimetric curve of a yellow carbon dot solid powder under a nitrogen atmosphere. Since the yellow carbon dots have high crystallization degree, the thermogravimetric curve clearly shows that when the temperature rises to about 200 ℃, the yellow carbon dot solid powder has no obvious weight loss sign, and when the temperature rises to about 250 ℃, the weight loss amount is only 4.63%, so that the yellow carbon dot solid powder has high thermal stability.

From the thermogravimetric curve of the yellow carbon point fluorescent film in fig. 8(b), it can be found that when the temperature rises to about 300 ℃, the weight loss of the fluorescent film is only 3.04%, and the high-energy irradiation requirement of the laser device can be met.

The excellent thermal stability of the yellow carbon point fluorescent film is attributed to the higher crystallization degree of the yellow carbon point, and on the other hand, the yellow carbon point solution is mixed with the film-forming agent KH-792 to be hydrolyzed to generate Si ‒ O bonds, so that the stability of the matrix is further improved.

This is demonstrated by the FTIR spectra of KH-792 and yellow carbon spot fluorescent film of FIG. 9. 1084cm in FTIR spectrum of KH-792^-1Corresponding to the stretching vibration peak of Si ‒ O ‒ C, and appear in the FTIR spectrum of the yellow carbon point fluorescent film at 1024 and 1124cm^-1The stretching vibration peak of Si ‒ O ‒ Si proves that SiO₂The formation of the network structure greatly improves the thermal stability of the fluorescent film.

Example 1 is applied.

In view of the excellent luminescence property and higher photo-thermal stability of the yellow carbon dot solid powder prepared by the invention, the yellow carbon dot fluorescent film prepared by the yellow carbon dot solid powder is used as a fluorescent conversion material to be applied to a white light LD device.

A450 nm laser diode is selected to be combined with a yellow carbon point fluorescent film. And fixing the LD with the wavelength of 450nm on a base of the test bench, connecting the positive and negative wires with an external power supply, and fixing the yellow carbon dot fluorescent film above the LD to obtain the LD lighting device.

The emission spectrum, the color coordinate, the correlated color temperature and the color rendering index of an LD device are tested by adopting a spectral scanning colorimeter of a American PR-655 Spectra Scan model, and the spectral scanning range of the device is 380-780 nm.

And testing the light emitting condition of the LD under different working voltages of 4.8-5.4V. As shown in fig. 10(a), the narrow emission peak at 450nm is from LD, the wider emission region from 475nm to 750nm is from yellow carbon dot fluorescent film, and the LD and yellow carbon dot fluorescent film emit pure white light after being compounded, the color coordinate is (0.31, 0.32), the correlated color temperature is 5971K, and the color rendering index is raised to 71, as shown in fig. 10 (b).

Example 3.

0.21g of trimesic acid and 0.21g of o-phenylenediamine are weighed, added into 40mL of absolute ethyl alcohol, dissolved uniformly by ultrasonic, placed in a 100mL reaction kettle, and subjected to solvothermal reaction for 12 hours in an oven at 180 ℃. And after the reaction is finished, air cooling to room temperature to obtain a tan carbon dot solution.

And (3) taking out the carbon dot solution, filtering the carbon dot solution by using a 0.22-micron filter membrane, putting the filtrate into a 500Da dialysis bag, and carrying out dialysis treatment in absolute ethyl alcohol for 42 hours, wherein the absolute ethyl alcohol is replaced every 6 hours in the dialysis bag so as to remove fluorescent small molecules and other impurities in the filtrate, thus preparing the yellow carbon dot with high photo-thermal stability.

After the dialysis, the solution in the dialysis bag was taken out and subjected to rotary evaporation treatment to obtain carbon dot solid powder.

Weighing 10mg of carbon dot solid powder, adding 1.2mL of absolute ethyl alcohol, after the carbon dot solid powder is fully dissolved, continuously adding 1.1mL of silane coupling agent KH-792 and 0.6mL of deionized water into the solution, and carrying out ultrasonic treatment for 5min to uniformly mix the solution to obtain a clear brown solution.

Example 4.

0.84g of trimesic acid and 0.21g of o-phenylenediamine are weighed, added into 45mL of absolute ethyl alcohol, dissolved uniformly by ultrasonic, placed in a 100mL reaction kettle, and subjected to solvothermal reaction for 8 hours in an oven at 220 ℃. And after the reaction is finished, air cooling to room temperature to obtain a tan carbon dot solution.

And (3) taking out the carbon dot solution, filtering the carbon dot solution by using a 0.22-micron filter membrane, putting the filtrate into a 500Da dialysis bag, and carrying out dialysis treatment in absolute ethyl alcohol for 60 hours, wherein the absolute ethyl alcohol is replaced every 12 hours in the dialysis bag so as to remove fluorescent small molecules and other impurities in the filtrate, thus preparing the yellow carbon dot with high photo-thermal stability.

Weighing 6mg of carbon dot solid powder, adding 0.8mL of absolute ethyl alcohol, after the carbon dot solid powder is fully dissolved, continuously adding 0.8mL of silane coupling agent KH-792 and 0.4mL of deionized water into the solution, and carrying out ultrasonic treatment for 5min to uniformly mix the solution to obtain a clear brown solution.

Example 5.

0.4g of trimesic acid and 0.2g of o-phenylenediamine are weighed, added into 35mL of absolute ethyl alcohol, dissolved uniformly by ultrasonic, placed into a 100mL reaction kettle, and subjected to solvothermal reaction for 11 hours in an oven at 190 ℃. And after the reaction is finished, air cooling to room temperature to obtain a tan carbon dot solution.

And (3) taking out the carbon dot solution, filtering the carbon dot solution by using a 0.22-micron filter membrane, putting the filtrate into a 500Da dialysis bag, and carrying out dialysis treatment in absolute ethyl alcohol for 40 hours, wherein the absolute ethyl alcohol is replaced every 6 hours in the dialysis bag so as to remove fluorescent small molecules and other impurities in the filtrate, thus preparing the yellow carbon dot with high photo-thermal stability.

Weighing 5mg of carbon dot solid powder, adding 0.5mL of absolute ethyl alcohol, after the carbon dot solid powder is fully dissolved, continuously adding 0.6mL of silane coupling agent KH-792 and 0.2mL of deionized water into the solution, and carrying out ultrasonic treatment for 5min to uniformly mix the solution to obtain a clear brown solution.

The above embodiments of the present invention are not intended to be exhaustive or to limit the invention to the precise form disclosed. Various changes, modifications, substitutions and alterations to these embodiments will be apparent to those skilled in the art without departing from the principles and spirit of this invention.

Claims

1. A yellow carbon dot with high photo-thermal stability is characterized in that trimesic acid is used as a carbon source, o-phenylenediamine is used as a nitrogen source, a carbon dot solution obtained by solvothermal reaction in absolute ethyl alcohol emits bright yellow light under the irradiation of an ultraviolet lamp.

2. The method for preparing a yellow carbon dot with high photo-thermal stability of claim 1, which comprises the steps of dissolving solid powder of trimesic acid and o-phenylenediamine in absolute ethyl alcohol, heating the mixture to 180-220 ℃ in a sealed high-pressure reaction kettle, and carrying out solvothermal reaction to prepare the yellow carbon dot solution.

3. The method for preparing a yellow light carbon dot with high photo-thermal stability as claimed in claim 2, wherein the yellow light carbon dot solution is placed in a dialysis bag with a molecular weight cutoff of 500Da and dialyzed and purified in absolute ethanol.

4. The method for preparing a yellow carbon dot with high photo-thermal stability according to claim 2, wherein the molar ratio of the trimesic acid to the o-phenylenediamine is 1: 1.

5. The method for preparing a yellow carbon dot with high photo-thermal stability according to claim 2, wherein the solvothermal reaction time is 8-12 h.

6. A yellow carbon dot fluorescent film with high photothermal stability, which is obtained by mixing the yellow carbon dot with high photothermal stability according to claim 1 with a silanization coupling agent KH-792, and curing to form a film.

7. Use of the yellow carbon dot fluorescent thin film with high photo-thermal stability of claim 6 in the preparation of a white LD device.

8. The use of claim 7, in which the yellow carbon dot fluorescent film is combined with a 450nm blue LD to prepare a white LD device.