Preparation method of fluorescent sulfur quantum dots

Abstract

The invention discloses a preparation method of fluorescent sulfur quantum dots, and relates to the technical field of preparation of sulfur quantum dots. The method comprises the following steps: sequentially adding sublimed sulfur powder, ethylenediamine and a NaOH or KOH solution into a beaker, uniformly mixing, further performing ultrasonic treatment, putting into a reaction kettle, putting into a constant-temperature blast drying oven for reaction, cooling to room temperature after the reaction is finished, and filtering to obtain the high-quality fluorescent sulfur quantum dots. The preparation method is low in cost, simple in preparation step, short in preparation time, environment-friendly and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of sulfur quantum dot preparation, and in particular to a method for preparing fluorescent sulfur quantum dots. Background Art

[0002] Sulfur quantum dots are spherical sulfur nanoparticles at the nanometer level. As an emerging non-metallic quantum dot, sulfur has attracted much attention due to its non-toxicity, abundant reserves and low cost. It has excellent water solubility, chemical stability and biocompatibility, and its fluorescence emission spectrum covers the range from blue light to near-infrared light, providing broad adaptability for applications in multiple fields.

[0003] In the process of research and development of sulfur quantum dot preparation technology, many preparation methods in the existing technology have significant deficiencies. Specifically: the sulfur quantum dot products prepared by the thermal decomposition method have poor uniformity in terms of size, morphology and performance, which is difficult to meet the application scenarios with strict requirements on product consistency; the solvent thermal method has strict requirements on the reaction equipment, and needs to be equipped with a special reaction device that can withstand high temperature and high pressure, and the equipment cost is high and the maintenance is complicated; in the preparation process of the microwave-assisted method, not only the equipment purchase cost is high, but also the energy consumption during the operation process is large, resulting in high comprehensive costs; in the chemical reduction method, due to the high surface activity of sulfur quantum dots during the reaction, agglomeration is very likely to occur, which seriously affects its optical, electrical and other properties; the electrochemical method is limited by the reaction mechanism and equipment conditions, and the output of sulfur quantum dots is low, which cannot meet the needs of large-scale production; although the biosynthesis method has the advantages of green environmental protection, the purity of the prepared sulfur quantum dots is poor and contains more biological impurities, which affects its use in high-precision application fields.

[0004] The hydrothermal synthesis method is based on a high temperature and high pressure reaction environment, which can theoretically provide an efficient path for the preparation of sulfur quantum dots. However, in the traditional hydrothermal synthesis of sulfur quantum dots, there are a series of problems that need to be solved. First, in order to promote the nucleation and growth of quantum dots, complex templates and surfactants are often required. This not only greatly increases the cost of raw materials, but also easily leads to the agglomeration of sulfur quantum dots in the subsequent removal of these additives, and at the same time, defects are generated on the surface of quantum dots, thereby reducing their fluorescence performance and affecting product quality. Second, some hydrothermal synthesis processes have extremely high requirements for reaction equipment, requiring specific materials, specifications and equipment with precise temperature and pressure control functions. Moreover, the reaction conditions of these processes are extremely sensitive and difficult to accurately reproduce, which seriously restricts the application of this method in large-scale industrial production and cannot achieve stable and efficient mass production.

[0005] In order to overcome the above problems, a new hydrothermal synthesis preparation technology is urgently needed that is streamlined, efficient, green and environmentally friendly, does not require complicated additives, can accurately control the size and performance of sulfur quantum dots, and meets the requirements of industrial continuous production. This patent is aimed at this technical gap and innovatively proposes a preparation method for fluorescent sulfur quantum dots, striving to break the shackles of existing sulfur quantum dot preparation technology and promote its widespread application and industrialization process. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing fluorescent sulfur quantum dots.

[0007] The specific steps of the method for preparing fluorescent sulfur quantum dots are as follows:

[0008] 0.26-1.3 g of sulfur source, 1-5 mL of surface modifier, and 25-30 mL of strong alkaline solution (0.5-4 mol / L) are added to a beaker in sequence, mixed, and then ultrasonically mixed in an ultrasonic instrument, and then the ultrasonicated solution is transferred to a reactor, and reacted in a constant temperature blast drying oven at 160-200 °C for 2-10 h. After the reaction is completed and cooled to room temperature, it is filtered in sequence using qualitative filter paper and a needle filter to obtain a fluorescent sulfur quantum dot stock solution;

[0009] Preferably, the sulfur source is sublimed sulfur;

[0010] Preferably, the sublimated sulfur chemical has a purity of 98%;

[0011] Preferably, the surface modifier is ethylenediamine;

[0012] Preferably, the purity of the ethylenediamine drug is 99%;

[0013] Preferably, the reaction temperature is 160-200 °C and the reaction time is 2-10 h;

[0014] Preferably, the strong alkaline solution is NaOH or KOH solution.

[0015] The prepared sulfur quantum dots have the following characteristics:

[0016] (1) The sulfur quantum dots are synthesized in water phase, can be directly dissolved in water phase, and can be applied in the biological field;

[0017] (2) The maximum excitation and emission wavelengths of the sulfur quantum dots synthesized in the present invention are 320 nm and 390 nm, respectively;

[0018] (3) The sulfur quantum dots are spherical in shape and have a uniform particle size distribution. Under optimal conditions, the particle size is between 3.2 nm and 5.6 nm, the average particle size is 4.51 nm, and the interplanar spacing is 0.16 nm.

[0019] (4) The relative quantum yield of the sulfur quantum dots can reach 11.16%;

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: the method of the present invention is simple and rapid, and the synthesized sulfur quantum dots have high fluorescence yield and good water solubility. NaOH or KOH solution can accelerate the dissolution of sublimated sulfur and accelerate the reaction. The one-step hydrothermal method is adopted, which reduces the cumbersome steps and shortens the reaction time, and optically excellent fluorescent sulfur quantum dots can be obtained in only 2-10 h. The maximum excitation and emission wavelengths of the sulfur quantum dots synthesized by the present invention are 320 nm and 390 nm, respectively, and the relative quantum yield is 11.16%. In addition, the synthesized sulfur quantum dots show excellent fluorescence stability. Even if they are placed in a room temperature environment for up to three months, their fluorescence characteristics remain stable without obvious attenuation or changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the TEM image of the sulfur quantum dots in Example 1.

[0022] Figure 2 This is the HRTEM image of the sulfur quantum dots in Example 1.

[0023] Figure 3 This is the Fourier transform infrared spectrum of the sulfur quantum dots in Example 1.

[0024] Figure 4 This is the ultraviolet absorption spectrum of the sulfur quantum dots in Example 1.

[0025] Figure 5 This is the fluorescence optimal excitation emission spectrum of the sulfur quantum dots in Example 1.

[0026] Figure 6 This is the fluorescence optimal excitation emission spectrum of the sulfur quantum dots in Example 2.

[0027] Figure 7 This is the fluorescence optimal excitation emission spectrum of the sulfur quantum dots in Example 3.

[0028] Figure 8 This is the fluorescence optimal excitation emission spectrum of the sulfur quantum dots in Example 4.

[0029] Fig. 9 This is the fluorescence optimal excitation emission spectrum of the sulfur quantum dots in Example 5. DETAILED DESCRIPTION

[0030] Embodiment 1:

[0031] (1) Weigh 0.8 g of sublimated sulfur powder, 3 mL of ethylenediamine, and 27 mL of 1 mol / L NaOH solution, place them in a beaker and mix them;

[0032] (2) The solution obtained in step (1) is placed in a 100 mL centrifuge tube, and ultrasonicated in an ultrasonicator for 20 minutes. The ultrasonicated solution is then placed in a polytetrafluoroethylene liner and finally placed in a reactor. The reaction is carried out in a constant temperature forced air drying oven at 200°C for 4 hours. After the reaction is completed and cooled to room temperature, the solution is filtered using qualitative filter paper and a needle filter in sequence to obtain a fluorescent sulfur quantum dot stock solution.

[0033] The morphology was observed by TEM. Figure 1 As shown in Figure 1, the particle size ranges from 3.2 nm to 5.6 nm, with an average particle size of 4.51 nm. The lattice spacing observed by HRTEM is shown in Figure 1. Figure 2 As shown in Figure 1, the lattice spacing is 0.16 nm. Its infrared spectrum is shown in Figure 1 Figure 3 Its ultraviolet spectrum is shown in Figure 4 Its fluorescence optimal excitation emission spectrum is shown in Figure 5 As shown, the optimal excitation is at 321 nm and the optimal emission is at 389 nm.

[0034] Embodiment 2:

[0035] In the preparation method of this embodiment, the concentration of the NaOH solution is changed to 2 mol / L, and the remaining steps are the same as those in Example 1. The fluorescence optimal excitation emission spectrum is shown in FIG. Figure 6 As shown, the optimal excitation is at 322 nm and the optimal emission is at 383 nm.

[0036] Embodiment 3:

[0037] In the preparation method of this embodiment, the reaction temperature is 160°C, and the remaining steps are the same as those in Example 1. The optimal fluorescence excitation emission spectrum is shown in FIG. Figure 7 As shown, the optimal excitation is at 319 nm and the optimal emission is at 386 nm.

[0038] Embodiment 4:

[0039] In the preparation method of this embodiment, the reaction time is 10 h, and the remaining steps are the same as those in Example 1. The optimal fluorescence excitation emission spectrum is shown in FIG. Figure 8 As shown, the optimal excitation is at 318 nm and the optimal emission is at 380 nm.

[0040] Embodiment 5:

[0041] In the preparation method of this embodiment, NaOH solution is replaced with KOH solution, and the remaining steps are the same as those in Example 1. The fluorescence optimal excitation emission spectrum is shown in FIG. Fig. 9 As shown, the optimal excitation is at 320 nm and the optimal emission is at 387 nm.

[0042] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for preparing fluorescent sulfur quantum dots, characterized in that The specific steps are: 0.26~1.30 g sulfur source, 1~5 mL surface modifier, and 25~30 mL strong alkaline solution (0.5~4 mol / L) were added to a beaker in sequence, mixed evenly, and ultrasonicated in an ultrasonicator for 20 minutes. The ultrasonicated solution was then transferred to a reactor and reacted in a constant temperature blast drying oven at 160~200 ℃ for 2~10 h. After the reaction was completed and cooled to room temperature, it was filtered to obtain a fluorescent sulfur quantum dot stock solution.

2. The preparation method according to claim 1, characterized in that The sulfur source is sublimated sulfur.

3. The preparation method according to claim 1, characterized in that The purity of the sublimated sulfur chemical is 98%.

4. The preparation method according to claim 1, characterized in that The surfactant is ethylenediamine.

5. The preparation method according to claim 1, characterized in that The purity of the ethylenediamine drug is 99%.

6. The preparation method according to claim 1, characterized in that The reaction temperature is 160-200°C and the reaction time is 2-10 h.

7. The preparation method according to claim 1, characterized in that The strong alkaline solution is NaOH or KOH solution.

8. The preparation method according to claim 1, characterized in that In the filtering step, qualitative filter paper and needle filter are used for filtering in sequence.

9. The preparation method according to claim 1, characterized in that The optimal excitation and emission wavelengths of the sulfur quantum dots are 320 nm and 390 nm respectively. Under the optimal conditions, the particle size is between 3.2 nm and 5.6 nm, the average particle size is 4.51 nm, the interplanar spacing is 0.16 nm, and the relative fluorescence quantum yield can reach 11.16%.

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