A method for enhancing fluorescence performance of carbon dots based on talcum powder

Abstract

The application discloses a method for enhancing the fluorescent performance of carbon dots based on talcum powder. Citric acid, urea and talcum powder are weighed according to a mass ratio, transferred to a mortar and ground uniformly; the mixture is transferred to a quartz boat and placed in a tube furnace; in a nitrogen atmosphere, heating to 100-300 DEG C constant temperature reaction 0.5-4 h, cooling to room temperature, taking out and grinding into powder; a certain amount of solid powder is dissolved in ultrapure water to obtain a talcum powder-based carbon dot solution. The application innovatively uses talcum powder as a carbon dot fluorescent enhancer, adopts a ternary solid phase system of "citric acid-urea-talcum powder", combines a nitrogen protection low-temperature polymerization process, regulates the carbon dot performance through the synergistic effect of mineral powder and carbon source, creates a brand-new composite synthesis path, and realizes the significant improvement of the fluorescent performance of carbon dots, wherein the fluorescent intensity can be enhanced by 7 times at most, and the fluorescent color can be controllably changed from blue to green.

Description

Technical Field

[0001] This invention relates to the field of fluorescent nanomaterials, and in particular to a method for enhancing the fluorescence properties of carbon dots based on talc. Background Technology

[0002] Carbon dots (CDs) are spherical carbon nanomaterials typically smaller than 10 nanometers in size. As a novel type of photoluminescent carbon nanoparticle, carbon dots possess unique physicochemical properties and good biocompatibility, exhibiting advantages such as low toxicity, ease of functionalization, good biocompatibility, good photostability, and tunability. Therefore, they are widely used in fields such as anti-counterfeiting and information protection, bioimaging, environmental monitoring, optoelectronic devices, and light-emitting diodes (LEDs). Currently, the main synthesis methods for carbon dots include electrochemical oxidation, hydrothermal methods, and solvothermal methods, but these are limited by low fluorescence quantum yield, high time cost, and long processing times. Therefore, developing a method for the controllable preparation and mass production of CDs is of great significance.

[0003] Currently, there are two main methods to enhance the fluorescence performance of photoluminescence crystals (CDs): surface modification and doping. For example, nitrogen doping can enhance the photoluminescence of CDs, while doping can adjust the photoluminescence wavelength. Surface modification can change the surface structure of CDs, which can not only maintain the original luminescent properties but also greatly improve the fluorescence performance of CDs, such as fluorescence quantum yield and fluorescence stability.

[0004] Talc powder is a mineral powder with hydrated magnesium silicate as its main component. It has stable chemical properties and good resistance to acids and alkalis, fire resistance, and insulation. Therefore, a new method was designed to use talc powder to regulate the fluorescence properties of carbon dots, which is expected to obtain new functional materials and further expand their application value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enhancing the fluorescence performance of carbon dots based on talc. The prepared talc-enhanced carbon dots not only achieve a significant improvement in fluorescence intensity, but also enable the regulation of fluorescence color from blue to cyan-green, thus expanding the application scenarios and fields of carbon dots.

[0006] The technical solution of this invention is a method for enhancing the fluorescence properties of carbon dots based on talc powder, the specific steps of which are as follows:

[0007] (1) Weigh citric acid, urea and talc in a mass ratio of 1~3:1~3:1~5 and transfer them to a mortar and grind them until they are completely mixed.

[0008] (2) Transfer the mixture obtained in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it.

[0009] (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen, repeat at least once, and finally maintain the nitrogen atmosphere until the reaction is completely finished.

[0010] (4) Set the temperature to 100~300 ℃, the time to 0.5~4 h, and perform programmed temperature increase at a rate of 3 ℃ / min;

[0011] (5) After the reaction is complete, cool to room temperature, take out the sample and grind it into powder;

[0012] (6) Dissolve the powder obtained in step (5) in ultrapure water to obtain a talc-based enhanced fluorescent carbon dot (T-CDs) solution.

[0013] Preferably, the mass ratio of citric acid: urea: talc is 1:1:1.

[0014] Preferably, the talc powder has a mesh size of 325, 1500, 3000, 4000, or 5000. More preferably, the talc powder has a mesh size of 3000 or 5000. Even more preferably, the talc powder has a mesh size of 3000.

[0015] Preferably, the talc powder is white talc powder or black talc powder. More preferably, the talc powder is white talc powder.

[0016] Preferably, the temperature in step (4) is set to 150 °C and the time is 0.5 h, with the temperature increased at a rate of 3 °C / min.

[0017] Preferably, the test method for the prepared talc-based enhanced fluorescent carbon dots is as follows: take 1.0 mg of the powder obtained in step (5) and dissolve it in 5.0 mL of ultrapure water to obtain a talc-based enhanced fluorescent carbon dot solution with a concentration of 0.2 mg / mL;

[0018] The talc-based enhanced fluorescent carbon dot solution obtained above was transferred to a quartz cuvette, and fluorescence spectroscopy was performed at a voltage of 400-600 V, a slit width of 5-10 nm, and an excitation wavelength of 350-450 nm to compare the changes in fluorescence intensity before and after the addition of talc.

[0019] The talc-based enhanced fluorescent carbon dots prepared in this invention are synthesized as solid powders, and are mainly used in aqueous solutions. When the carbon dots dissolve in water, they increase fluorescence intensity and undergo color changes. The carbon dot T-CDs solution has the following characteristics:

[0020] (1) It can emit a bright bluish-green fluorescence;

[0021] (2) The fluorescence intensity was increased by 7 times compared with the preparation results without talc.

[0022] This invention uses talc powder (white talc / black talc, different mesh sizes) as an enhancer and key auxiliary material for carbon dot synthesis. Utilizing its stable chemical properties and dispersibility, it achieves a significant increase in fluorescence intensity (up to 7 times) and regulation of fluorescence color from blue to cyan-green without relying on complex surface modification or expensive doping elements. It is a physicochemical synergistic enhancement strategy for carbon dot luminescence performance, with a simpler and lower optimization method.

[0023] This invention features high efficiency and high performance. Controlling the reaction temperature, time, and mass ratio is a key step in synthesizing high-performance T-CDs. The inventors discovered that when the mass ratio of citric acid:urea:talc is 1:1:1, the reaction temperature is 150 °C, the reaction time is 0.5 h, and the talc powder is 3000 mesh, talc powder can best regulate the fluorescence performance of the carbon dots, resulting in not only higher fluorescence intensity but also a change from blue fluorescence to cyan-green fluorescence. Therefore, this invention achieves targeted optimization of fluorescence intensity and emission wavelength through systematic control of the type, mesh size, ratio, and reaction conditions of talc powder.

[0024] Furthermore, by adjusting the mesh size of talc powder (3000 mesh is optimal) and the ratio of raw materials, this invention can change the fluorescence of carbon dots from blue to cyan-green while ensuring high-intensity luminescence, thus achieving precise dual control of "intensity + color".

[0025] In existing technologies, carbon dots prepared using citric acid and urea exhibit blue fluorescence, limiting their application scenarios. When they turn cyan-green, their fluorescence performance improves, making them suitable for designing detection probes. Furthermore, they can be combined with multiple colors for various applications, such as digital encryption, information anti-counterfeiting, and LEDs. Therefore, the T-CDs prepared in this invention not only possess superior fluorescence performance but also expand their application functions and scenarios. They can be used as nanoluminescent materials to construct fluorescence-colorimetric sensors for applications in sensing, fingerprint recognition, and information encryption.

[0026] The preparation method of this invention also has industrialization potential. This invention adopts a low-temperature (100~300 ℃) solid-phase reaction with a yield of 60~80%. In terms of preparation process, a nitrogen-assisted low-temperature solid-phase polymerization method is used. The preparation process is simple and the process conditions are easy to control, which can realize controllable preparation and mass production. It solves the industrialization bottleneck of traditional methods and is a low-cost and large-scale preparation solution. Attached Figure Description

[0027] Figure 1 is a comparison of the emission performance of carbon dots enhanced by white talc powder of different mesh sizes in Example 1.

[0028] Figure 2 shows the fluorescence spectra of T-CDs in Example 1 at different excitation wavelengths.

[0029] Figure 3 shows the maximum excitation wavelength and emission wavelength of T-CDs in Example 1.

[0030] Figure 4 is a comparison of the emission performance of carbon dots regulated by black talc powder in Example 3.

[0031] Figure 5 shows the fluorescence emission pattern of CDs in Comparative Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Any modifications or equivalent substitutions made based on the inventive concept are within the scope of protection of this invention.

[0033] Example 1

[0034] (1) Weigh citric acid, urea and white talc (3000 mesh) in a mass ratio of 1:1:1 and transfer them to a mortar and grind for 15 min until they are completely mixed.

[0035] (2) Transfer the solid mixture in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it.

[0036] (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen. Repeat this process 3 times, and finally maintain the nitrogen atmosphere until the reaction is complete.

[0037] (4) Set the temperature to 150 ℃ and the time to 0.5 h, and perform programmed temperature increase at a rate of 3 ℃ / min;

[0038] (5) After the reaction is completed, cool to room temperature, take out the sample and grind it into powder. The yield is 75%. The yield is calculated as follows: product yield = weight of solid powder obtained after reaction / weight of solid mixture at the time of feeding.

[0039] (6) Dissolve 1.0 mg of solid powder in 5.0 mL of ultrapure water to obtain talc-based fluorescent carbon dots (T-CDs) with a concentration of 0.2 mg / mL.

[0040] (7) Transfer the solution from (6) to a quartz cuvette and perform fluorescence spectroscopy at a voltage of 550 V, a slit width of 5 nm, and an excitation wavelength of 440 nm to compare the changes in fluorescence intensity before and after the addition of talc.

[0041] Analysis of the results showed that the T-CDs prepared with a mesh size of 3000 exhibited the strongest fluorescence (see Figure 1). Under 365°C UV light irradiation, the T-CDs aqueous solution emitted a bright bluish-green fluorescence. The fluorescence intensity of existing CDs is 114, while that of T-CDs is 850. The fluorescence intensity of the T-CDs of this invention is approximately seven times that of existing CDs.

[0042] Figure 2 This indicates that T-CDs exhibit excitation-dependent emission properties, consistent with the optical properties of most carbon dots. Furthermore, the addition of talc further enhances these properties, demonstrating that T-CDs are excellent fluorescent materials. Their maximum excitation and emission wavelengths are 440 nm and 518 nm, respectively (see...). Figure 3 ).

[0043] Under the same preparation conditions, the fluorescence effect of talc-free carbon dots was demonstrated compared to those prepared with citric acid and urea (without talc). Comparing the emission peak positions and intensities under the same testing conditions showed that the addition of talc increased the fluorescence intensity by 7 times.

[0044] Example 2

[0045] (1) Weigh citric acid, urea and white talc (5000 mesh) in a mass ratio of 1:2:1, transfer them to a mortar and grind for 15 min until they are completely mixed.

[0046] (2) Transfer the solid mixture in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it.

[0047] (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen. Repeat this process 3 times, and finally maintain the nitrogen atmosphere until the reaction is complete.

[0048] (4) Set the temperature to 100 ℃ and the time to 1.0 h, and perform programmed temperature increase at a rate of 3 ℃ / min;

[0049] (5) After the reaction was completed, the sample was cooled to room temperature, and then ground into powder. The yield was 68%.

[0050] (6) Dissolve 1.0 mg of solid powder in 5.0 mL of ultrapure water to obtain talc-based fluorescent carbon dots (T-CDs) with a concentration of 0.2 mg / mL.

[0051] (7) Transfer the solution from (6) to a quartz cuvette and perform fluorescence spectroscopy at a voltage of 500 V, a slit width of 10 nm, and an excitation wavelength of 400 nm to compare the changes in fluorescence intensity before and after the addition of talc.

[0052] The results showed that under 365°C UV light irradiation, the T-CDs aqueous solution emitted a bright cyan-green fluorescence, with the fluorescence intensity increasing by 2 times, and exhibited excitation-dependent emission properties.

[0053] Example 3:

[0054] (1) Weigh citric acid, urea and black talc powder (3000 mesh) in a mass ratio of 1:1:1, transfer them to a mortar and grind for 15 min until they are completely mixed.

[0055] (2) Transfer the solid mixture in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it.

[0056] (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen. Repeat this process 3 times, and finally maintain the nitrogen atmosphere until the reaction is complete.

[0057] (4) Set the temperature to 150 ℃ and the time to 0.5 h, and perform programmed temperature increase at a rate of 3 ℃ / min;

[0058] (5) After the reaction was completed, the sample was cooled to room temperature, and then ground into powder. The yield was 65%.

[0059] (6) Dissolve 1.0 mg of solid powder in 5.0 mL of ultrapure water to obtain talc-based fluorescent carbon dots (T-CDs-2) with a concentration of 0.2 mg / mL.

[0060] (7) Transfer the solution from (6) to a quartz cuvette and perform fluorescence spectroscopy tests at a voltage of 550 V, a slit width of 5 nm, and an excitation wavelength of 440 nm. Compare the changes in fluorescence intensity before and after the addition of black talc powder.

[0061] The results showed that under 365°C UV light irradiation, the T-CDs-2 aqueous solution emitted a bright bluish-green fluorescence, with the fluorescence intensity increasing fourfold, and exhibited excitation-dependent emission properties (see [link to data]). Figure 4 ).

[0062] The parameter change in Example 3 was the type of talc powder, namely, the use of black talc powder. Although black talc can also enhance fluorescence performance, some impurities contained in black talc powder (such as organic matter such as humic acid (and reduced iron, manganese and other metal ions)) will affect the fluorescence effect, proving that 3000 mesh white talc powder is the best material.

[0063] Comparative Example 1:

[0064] (1) Weigh citric acid and urea in a mass ratio of 1:1, transfer them to a mortar, and grind for 15 minutes until they are completely mixed.

[0065] (2) Transfer the solid mixture in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it.

[0066] (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen. Repeat this process 3 times, and finally maintain the nitrogen atmosphere until the reaction is complete.

[0067] (4) Set the temperature to 150 ℃ and the time to 0.5 h, and perform programmed temperature increase at a rate of 3 ℃ / min;

[0068] (5) After the reaction was completed, the sample was cooled to room temperature, and then ground into powder. The yield was 75%.

[0069] (6) Dissolve 1.0 mg of solid powder in 5.0 mL of ultrapure water to obtain fluorescent carbon dots (CDs) with a concentration of 0.2 mg / mL.

[0070] (7) Transfer the solution from (6) to a quartz cuvette and perform fluorescence spectroscopy at a voltage of 550 V, a slit width of 5 nm, and an excitation wavelength of 440 nm.

[0071] The results showed that under 365°C UV light irradiation, the CDs aqueous solution emitted a weak bluish-green fluorescence, with the maximum fluorescence emission peak at 506 nm (see Figure 5).

[0072] Compared with Examples 1, 2, and 3, Comparative Example 1 showed poor fluorescence performance of the carbon dots, with a blue fluorescence color. Comparative Example 1 demonstrates the effect of the presence or absence of talc on the performance of carbon dots. Without the addition of talc, the carbon dots prepared by citric acid + urea exhibited only blue fluorescence (consistent with existing reports), and the fluorescence intensity was relatively weak. However, with the addition of talc, the unique physicochemical properties of talc can significantly alter the electronic transition process of the carbon dots, enhancing fluorescence performance and expanding their application value.

[0073] This invention innovatively introduces talc into the carbon dot synthesis system through nitrogen-assisted low-temperature solid-state polymerization. Using citric acid and urea as carbon and nitrogen sources, and by controlling the raw material mass ratio, talc mesh size, and reaction conditions, it achieves a significant increase in carbon dot fluorescence intensity (up to 7 times) and control of the emission color (from blue to cyan-green). It also has the advantages of simple preparation process and mass production capability.

[0074] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical principles disclosed in the present invention, such as using hydrolytic enzymes from other sources with similar specificity, or making equivalent substitutions for the chromatographic packing materials and conditions in the purification step, should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for enhancing the fluorescence properties of carbon dots based on talc, characterized in that, The specific steps of the method are as follows: (1) Weigh citric acid, urea and talc in a mass ratio of 1~3:1~3:1~5 and transfer them to a mortar and grind them until they are completely mixed. (2) Transfer the mixture obtained in (1) into a quartz boat, place it in the center of the quartz tube of the tube furnace, and seal it. (3) Evacuate the quartz tube to ensure that all air is removed, then restore it with nitrogen, repeat at least once, and finally maintain the nitrogen atmosphere until the reaction is completely finished. (4) Set the temperature to 100~300 ℃, the time to 0.5~4 h, and perform programmed temperature increase at a rate of 3 ℃ / min; (5) After the reaction is complete, cool to room temperature, take out the sample and grind it into powder; (6) Dissolve the powder obtained in step (5) in ultrapure water to obtain a talc-based enhanced fluorescent carbon dot solution.

2. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 1, characterized in that, The mass ratio of citric acid, urea, and talc is 1:1:

1.

3. The method for enhancing the fluorescence properties of carbon dots based on talc powder as described in claim 2, characterized in that, The talc powder has a mesh size of 325, 1500, 3000, 4000, or 5000.

4. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 2, characterized in that, The talc powder has a mesh size of 3000 or 5000.

5. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 1, characterized in that, The talc powder is either white talc powder or black talc powder.

6. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 1, characterized in that, The talc powder is white talc powder.

7. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 1, characterized in that, The temperature in step (4) is set to 150 °C and the time is 0.5 h, with the temperature increased at a rate of 3 °C / min.

8. The method for enhancing the fluorescence properties of carbon dots based on talc as described in claim 1, characterized in that, Take 1.0 mg of the powder obtained in step (5) and dissolve it in 5.0 mL of ultrapure water to obtain a talc-based enhanced fluorescent carbon dot solution with a concentration of 0.2 mg / mL; The talc-based enhanced fluorescent carbon dot solution obtained above was transferred to a quartz cuvette, and fluorescence spectroscopy was performed at a voltage of 400-600 V, a slit width of 5-10 nm, and an excitation wavelength of 350-450 nm to compare the changes in fluorescence intensity before and after the addition of talc.

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