A method for producing a wurtzite zinc sulfide

Abstract

The application belongs to the technical field of zinc sulfide preparation, and provides a preparation method of wurtzite zinc sulfide. In the preparation method, N,N'-dimethylethylenediamine (DMEDA) and water are mixed to obtain a mixed solvent; the mixed solvent, a zinc salt and thiourea are mixed, and a mixed solution obtained is subjected to a solvothermal reaction to obtain the wurtzite zinc sulfide. In the application, N,N'-dimethylethylenediamine is used as a structure directing agent, and high temperature and particle agglomeration are avoided; meanwhile, N,N'-dimethylethylenediamine can effectively regulate the nucleation and growth kinetics of crystals, significantly improve the crystallization quality of a product, and spherical wurtzite zinc sulfide is prepared. Data of examples show that the wurtzite zinc sulfide prepared by the application has a wider direct band gap, which indicates that the wurtzite zinc sulfide has more excellent optical performance and a lower defect state density.

Description

Technical Field

[0001] This invention relates to the field of zinc sulfide preparation technology, and in particular to a method for preparing zinc sulfide from wurtzite. Background Technology

[0002] Zinc sulfide, as an important group II-VI semiconductor material, has attracted widespread attention due to its wide bandgap, high refractive index, and excellent visible light transmittance. Zinc sulfide mainly exists in two crystal phases: cubic zincblende and hexagonal wurtzite. Although the wurtzite phase is metastable at low temperatures, its superior luminous efficiency and anisotropic growth behavior make it more favored in optoelectronic device applications.

[0003] However, traditional zinc sulfide synthesis methods (such as solid-state reaction or simple precipitation) mainly produce the thermodynamically stable cubic sphalerite phase. The transformation to the wurtzite phase usually requires high-temperature treatment, which not only leads to high energy consumption and particle agglomeration, but also makes it difficult to control the morphology. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing wurtzite zinc sulfide. The preparation method provided by the present invention uses N,N'-dimethylethylenediamine as a structure directing agent, avoiding high temperature and particle agglomeration, and obtaining spherical wurtzite zinc sulfide.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing zinc sulfide from wurtzite, comprising the following steps: N,N'-dimethylethylenediamine (DMEDA) and water were mixed to obtain a mixed solvent; The mixed solvent, zinc salt and thiourea are mixed, and the resulting mixture is subjected to a solvothermal reaction to obtain the zinc sulfide of wurtzite.

[0006] Preferably, the volume ratio of N,N'-dimethylethylenediamine (DMEDA) to water is 3:17 to 13:7.

[0007] Preferably, the molar ratio of zinc in the zinc salt to sulfur in the thiourea is 1:2.5~3.5.

[0008] Preferably, the concentration of zinc salt in the mixture is 0.2~0.3 mol / L.

[0009] Preferably, the zinc salt is zinc sulfate.

[0010] Preferably, mixing the mixed solvent, zinc salt, and thiourea includes the following steps: mixing the mixed solvent and zinc salt, first stirring to obtain a zinc precursor solution; mixing the zinc precursor solution and thiourea, second stirring to obtain the mixed solution.

[0011] Preferably, the rotation speed of the first stirring and the second stirring are independently 200~300 rpm, and the time is independently 20~40 min.

[0012] Preferably, the temperature of the solvothermal reaction is 140~180℃ and the time is 14~18h.

[0013] Preferably, after the solvothermal reaction, the method further includes: performing solid-liquid separation on the obtained reaction solution and collecting the precipitate; washing and drying the precipitate in sequence to obtain the zinc sulfide from wurtzite.

[0014] Preferably, the solid-liquid separation method is vacuum filtration; the washing reagent is water; and the drying temperature is 50~70℃ for 4~6 hours.

[0015] This invention provides a method for preparing zinc sulfide from wurtzite.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The method of this invention avoids the drawbacks of traditional methods, such as high energy consumption, particle agglomeration, and irregular morphology, which involve high-temperature treatment to transform the zinc sulfide into the wurtzite phase. It achieves the direct synthesis of uniformly morphological wurtzite ZnS nanoparticles under simple low-temperature (140~180℃) conditions. Compared with methods that do not use organic amine regulators or other primary amine regulators, this invention uses DMEDA as a structure-directing agent, which can induce the growth of zinc sulfide along the (100) and (101) crystal planes. At the same time, DMEDA, as a highly efficient structure-directing agent and kinetic regulator in the water-based mixed system, significantly reduces the formation temperature of the wurtzite phase, avoiding the drawbacks of traditional methods that rely on high-temperature calcination. The resulting product has uniform size and the process is simple. In addition, DMEDA avoids particle agglomeration. Furthermore, N,N'-dimethylethylenediamine can effectively regulate the nucleation and growth kinetics of crystals, significantly improving the crystal quality of the product and obtaining spherical wurtzite zinc sulfide. Data from the examples show that the wurtzite zinc sulfide prepared by the present invention has a wider direct band gap, which indicates that it has superior optical properties and a lower defect state density.

[0017] The beneficial effects of the preparation method provided by this invention are as follows: 1. Crystal form control: This invention utilizes N,N'-dimethylethylenediamine to effectively guide the crystallization of metastable wurtzite phase under low-temperature conditions. The prepared zinc sulfide is a pure wurtzite phase, avoiding the drawbacks of traditional methods that require high-temperature calcination.

[0018] 2. Morphology control: Compared with the irregularly agglomerated zinc sulfide particles synthesized by traditional methods, N,N'-dimethylethylenediamine can effectively guide the morphology control and crystallization process of wurtzite zinc sulfide, promoting the formation of uniform nanoparticles.

[0019] 3. Improvement in optical performance: through the Tauc equation ( αhν ) 2 =B( hν - Eg ) Calculate the direct band gap of ZnS ( Eg In this invention, the zinc sulfide from wurtzite prepared using the N,N'-dimethylethylenediamine system has the highest band gap value of 3.60 eV, which is significantly higher than the band gap value of the product obtained without the N,N'-dimethylethylenediamine system. Attached Figure Description

[0020] Figure 1 The X-ray diffraction patterns of zinc sulfide prepared in Examples 1-5 and Comparative Examples 1-3 are shown below. Figure 2 The Raman spectra of zinc sulfide prepared in Examples 1-5 and Comparative Examples 1-3 are shown. Figure 3 The images are scanning electron microscope (SEM) images of the zinc sulfide prepared in Examples 1-5 and Comparative Examples 1-3. Detailed Implementation

[0021] This invention provides a method for preparing zinc sulfide from wurtzite, comprising the following steps: N,N'-dimethylethylenediamine (DMEDA) and water were mixed to obtain a mixed solvent; The mixed solvent, zinc salt and thiourea are mixed, and the resulting mixture is subjected to a solvothermal reaction to obtain the zinc sulfide of wurtzite.

[0022] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0023] This invention involves mixing N,N'-dimethylethylenediamine (DMEDA) and water (referred to as the first mixture) to obtain a mixed solvent. In this invention, the water is preferably deionized water. The volume ratio of N,N'-dimethylethylenediamine (DMEDA) to water is preferably 3:17 to 13:7, specifically preferably 3:17, 4:16, 5:15, 6:14, 7:13, 8:12, 9:11, 10:10, 11:9, 12:8, or 13:7, and more preferably 7:13. In this invention, the first mixture is preferably carried out under magnetic stirring conditions, with the stirring speed preferably at 200-300 rpm, more preferably at 250 rpm; the stirring time is preferably 20-40 min, more preferably 30 min; and the magnetic stirring is preferably carried out in a magnetic stirrer.

[0024] This invention significantly reduces the formation temperature of the wurtzite phase by using DMEDA as a highly efficient structure-directing agent and kinetic regulator in an aqueous mixed system, avoiding the drawbacks of traditional methods that rely on high-temperature calcination. Furthermore, the resulting product has uniform size, and the process is simple. Simultaneously, the N,N'-dimethylethylenediamine of this invention induces zinc sulfide to grow along the (100) and (101) crystal planes, significantly regulating the formation of the wurtzite crystal phase.

[0025] After obtaining the mixed solvent, the present invention mixes the mixed solvent, zinc salt, and thiourea (CH4N2S), and the resulting mixture undergoes a solvothermal reaction to obtain the zinc sulfide from wurtzite. In the present invention, the zinc salt is preferably zinc sulfate, more preferably zinc sulfate heptahydrate (ZnSO4·7H2O). In the present invention, the molar ratio of zinc in the zinc salt to sulfur in the thiourea is preferably 1:2.5~3.5, more preferably 1:3. In the present invention, the concentration of zinc salt in the mixture is preferably 0.2~0.3 mol / L, more preferably 0.25 mol / L. In the present invention, mixing the mixed solvent, zinc salt, and thiourea includes the following steps: mixing the mixed solvent and zinc salt, first stirring to obtain a zinc precursor liquid; mixing the zinc precursor liquid and thiourea, second stirring to obtain the mixture. In the present invention, the stirring speed of the first stirring is preferably 200~300 rpm, more preferably 250 rpm; the stirring time is preferably 20~40 min, more preferably 30 min. In this invention, the stirring speed of the second stirring is preferably 200-300 rpm, more preferably 250 rpm; the stirring time is preferably 20-40 min, more preferably 30 min.

[0026] In this invention, the temperature of the solvothermal reaction is 140~180℃, preferably 140℃, 160℃ or 180℃, and more preferably 160℃; the time is preferably 14~18h, preferably 16h. In this invention, the solvothermal reaction is preferably carried out in a high-pressure reactor.

[0027] Following the solvothermal reaction, the present invention preferably further includes: performing solid-liquid separation on the obtained reaction solution to collect the precipitate; and washing and drying the precipitate sequentially to obtain the zinc sulfide from wurtzite. In this invention, the solid-liquid separation is preferably performed by vacuum filtration; the washing reagent is preferably water, more preferably deionized water; the drying temperature is preferably 50-70°C, more preferably 60°C, and the drying time is preferably 4-6 hours, more preferably 5 hours.

[0028] In this invention, the optimal volume ratio of N,N'-dimethylethylenediamine to water was determined to be 7:13, and the solvothermal reaction temperature was 160℃, ensuring that the product is a uniformly morphological nanoparticle with stable performance. The prepared wurtzite zinc sulfide has a band gap value of up to 3.60 eV, which is significantly higher than that of the product obtained without N,N'-dimethylethylenediamine.

[0029] The following detailed description of the preparation method of zinc sulfide from wurtzite provided by the present invention, in conjunction with the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 A method for preparing zinc sulfide from wurtzite includes the following steps: Step 1: Measure 6.0 mL of DMEDA and 34.0 mL of deionized water in a volume ratio of 3:17, mix them, and place them in a magnetic stirrer. Stir at 250 rpm for 30 min to obtain a mixed solvent.

[0031] Step 2: Add 2.88g of zinc sulfate heptahydrate to the mixed solvent and stir continuously at 250rpm for 30min to obtain zinc precursor solution.

[0032] Step 3: Add 2.28g of thiourea to the zinc precursor solution at a zinc-sulfur source molar ratio of 1:3, and continue stirring at 250rpm for 30min to obtain a clear and homogeneous mixture.

[0033] Step 4: Transfer the homogeneous mixture obtained in Step 3 to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, and react at 160 °C for 16 h.

[0034] Step 5: Collect the white precipitate from the white slurry obtained after the reaction is completed by vacuum filtration, and then wash it thoroughly with deionized water.

[0035] Step 6: Place the washed white precipitate in a vacuum drying oven and dry it at 60°C for 5 hours to finally obtain spherical wurtzite zinc sulfide product.

[0036] Example 2 The difference from Example 1 is as follows: In step 1, 14.0 mL of DMEDA and 26.0 mL of deionized water were measured at a volume ratio of 7:13. After mixing, the mixture was placed in a magnetic stirrer and stirred at 250 rpm for 30 min to obtain a mixed solvent.

[0037] Example 3 The difference from Example 1 is as follows: In step 1, 26.0 mL of DMEDA and 14.0 mL of deionized water were measured in a volume ratio of 13:7, mixed and placed in a magnetic stirrer, and stirred magnetically at 250 rpm for 30 min to obtain a mixed solvent.

[0038] Example 4 The difference from Example 1 is as follows: In step 1, 14.0 mL of DMEDA and 26.0 mL of deionized water were measured at a volume ratio of 7:13. After mixing, the mixture was placed in a magnetic stirrer and stirred at 250 rpm for 30 min to obtain a mixed solvent.

[0039] In step 4, the homogeneous mixture obtained in step 3 is transferred to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 140 °C for 16 h.

[0040] Example 5 The difference from Example 1 is as follows: In step 1, 14.0 mL of DMEDA and 26.0 mL of deionized water were measured at a volume ratio of 7:13. After mixing, the mixture was placed in a magnetic stirrer and stirred at 250 rpm for 30 min to obtain a mixed solvent.

[0041] In step 4, the homogeneous mixture obtained in step 3 is transferred to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 180 °C for 16 h.

[0042] Comparative Example 1 The difference from Example 1 is as follows: In step 1, 40 mL of deionized water was used as the reaction solvent at a volume ratio of 0:1, and DMEDA was not added.

[0043] Comparative Example 2 To elucidate the unique role of N,N'-dimethylethylenediamine (DMEDA) in the synthesis of ZnS, the difference from Example 1 is as follows: In step 1, 14.0 mL of ethylenediamine (en) and 26.0 mL of deionized water were measured in a volume ratio of 7:13. After mixing, the mixture was placed in a magnetic stirrer and stirred magnetically at 250 rpm for 30 min to obtain a mixed solvent.

[0044] Comparative Example 3 To elucidate the unique role of N,N'-dimethylethylenediamine (DMEDA) in the synthesis of ZnS, the difference from Example 1 is as follows: In step 1, 14.0 mL of N,N,N',N'-tetramethylethylenediamine (TMEDA) and 26.0 mL of deionized water were measured in a volume ratio of 7:13. After mixing, the mixture was placed in a magnetic stirrer and stirred magnetically at 250 rpm for 30 min to obtain a mixed solvent.

[0045] Test Example 1 The products from Examples 1-5 and Comparative Examples 1-3 were subjected to X-ray diffraction analysis, and the X-ray diffraction patterns were obtained as follows: Figure 1 As shown, (a) is the XRD pattern of the products obtained from different ratios of DMEDA and deionized water in Examples 1-3, (b) is the XRD pattern of the products obtained from different temperatures in Examples 4 and 5, (c) is the XRD pattern of the product obtained in Comparative Example 1, and (d) is the XRD pattern of the products obtained in Comparative Examples 2 and 3. Figure 1 As shown in (a), the products obtained in Examples 1-3 all exhibit diffraction peaks near 2θ of 26.82°, 28.55°, 30.67°, 39.78°, 47.44°, 51.94°, and 56.45°, which completely correspond to the crystal planes in the wurtzite zinc sulfide standard card (JCPDS Card No. 36-1450), indicating that the obtained products are all wurtzite phases, and no other impurity diffraction peaks appear. Figure 1 As shown in (b), all samples synthesized between 140℃ and 180℃ were wurtzite ZnS. With increasing temperature, the diffraction peaks gradually became sharper and narrower, indicating increased crystallinity. Figure 1 As shown in (c), the product obtained in Comparative Example 1 exhibits diffraction peaks at 2θ of 28.56°, 47.87°, and 56.73°, which perfectly correspond to the crystal planes in the zinc sphalerite sulfide standard card (JCPDS Card No. 05-0500), indicating that the obtained product is a zinc sphalerite phase. Figure 1 As shown in (d), the en and TMEDA-based samples only exhibit broadened diffraction peaks, indicating insufficient crystallinity and phase control. These results fully demonstrate that the addition of DMEDA has a significant regulatory effect on the formation of the wurtzite crystal phase.

[0046] Test Example 2 The products from Examples 1-5 and Comparative Example 1 were subjected to Raman spectroscopy tests, and the Raman spectra were obtained, as shown in the figure. Figure 2 In the examples, (a) shows the Raman spectra of the products obtained from different proportions of DMEDA and deionized water in Examples 1-3, (b) shows the Raman spectra of the products obtained from different temperatures in Examples 4 and 5, (c) shows the Raman spectrum of the product obtained in Comparative Example 1, and (d) shows the Raman spectra of the products obtained in Comparative Examples 2 and 3. Figure 2As shown in (a), the Raman spectra of the products obtained in Examples 1-3 confirmed the regulatory effect of DMEDA on the crystal morphology of zinc sulfide wurtzite. The TO mode intensity of the products increased with increasing DMEDA concentration. This indicates that under mild conditions (160°C), DMEDA controls the morphology of ZnS by regulating nucleation kinetics and guides the crystallization of the metastable wurtzite phase. Figure 2 As shown in (b), in Examples 4-5, the intensity of the LO and TO modes increased and the peak shape narrowed with increasing temperature, confirming the improvement in crystallinity. Furthermore, the sample synthesized at 180°C showed a weak but broad peak at LA, which is attributed to the second-order scattering process associated with high crystallinity and long-range order. Figure 2 As shown in (c), the TO modulus strength of the product obtained in Comparative Example 1 is weak. Figure 2 As shown in (d), the Raman spectra of en and the TMEDA-based sample exhibit weakening and broadening characteristics. These results corroborate the XRD patterns of Test Example 1, indicating that under low-temperature conditions, DMEDA effectively guides the crystallization of the metastable wurtzite phase.

[0047] Test Example 3 The products from Examples 1-5 and Comparative Examples 1-3 were characterized by scanning electron microscopy, and the corresponding scanning electron microscope images were obtained. The results are shown in the figure below. Figure 3 Wherein, (a) is a scanning electron microscope (SEM) image of the product obtained in Example 1, (b) is a scanning electron microscope (SEM) image of the product obtained in Example 2, (c) is a scanning electron microscope (SEM) image of the product obtained in Example 3, (d) is a scanning electron microscope (SEM) image of the product obtained in Example 4, (e) is a scanning electron microscope (SEM) image of the product obtained in Example 5, (f) is a scanning electron microscope (SEM) image of the product obtained in Comparative Example 1, (g) is a scanning electron microscope (SEM) image of the product obtained in Comparative Example 2, and (h) is a scanning electron microscope (SEM) image of the product obtained in Comparative Example 3. Figure 3 As shown in (a), the zinc sulfide particles obtained in Example 1 are smaller and have clearer outlines, exhibiting uniform agglomerate size, as... Figure 3 As shown in (b), Example 2 yielded uniform, quasi-spherical ZnS nanoparticles with a narrow size distribution and low agglomeration. Figure 3 As shown in (c), in Example 3, excessive DMEDA leads to increased dielectric viscosity and excessive passivation of the crystal surface, resulting in the formation of large polyhedral aggregates. Figure 3 As shown in (d), in Example 4, at 140°C, uniform but relatively small primary particles were formed, which assembled into loose spherical clusters. Figure 3 As shown in (e), in Example 5, irregular blocky aggregates formed due to excessively rapid kinetics and uncontrollable agglomeration at excessively high temperatures at 180°C. Figure 3As shown in (f), in Comparative Example 1, without the addition of DMEDA, the reaction produced irregular and agglomerated particles, which was due to the rapid and uncontrolled nucleation process. Figure 3 As shown in (g) and (h), en (without methyl) or TMEDA (with excess methyl) disrupts the equilibrium, resulting in irregularly aggregated particles in the product. These results indicate that under mild conditions, DMEDA can effectively guide the morphology regulation and crystallization process of wurtzite zinc sulfide, promoting the formation of uniform nanoparticles.

[0048] Test Example 4 Using BaSO4 as a reference, the light absorption characteristics of the samples were studied in the wavelength range of 200–700 nm using a UV-2600i ultraviolet-visible spectrophotometer equipped with an integrating sphere. Furthermore, the Tauc equation ( αhν ) 2 =B( hν - E g ) Calculate the direct bandgap of ZnS ( E g ).

[0049] The zinc sulfide samples prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to optical performance tests according to the above method, and the direct band gap of each sample was calculated. E g ), see Table 1 for specific data.

[0050] Table 1 Direct band gap of zinc sulfide prepared in Examples 1-5 and Comparative Examples 1-3 ( E g )

[0051] As shown in Table 1, compared with the comparative example, the wurtzite zinc sulfide prepared by this invention has a higher band gap value, especially the product obtained in Example 2. The above data indicate that DMEDA plays more than just a simple solvent or ligand role in the reaction system; the band gap variation is attributed to differences in particle size, crystallinity, and defect density, all of which collectively affect the electronic structure.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing zinc sulfide from wurtzite, characterized in that, Includes the following steps: N,N'-dimethylethylenediamine and water were mixed to obtain a mixed solvent; The mixed solvent, zinc salt and thiourea are mixed, and the resulting mixture is subjected to a solvothermal reaction to obtain the zinc sulfide of wurtzite.

2. The preparation method according to claim 1, characterized in that, The volume ratio of N,N'-dimethylethylenediamine to water is 3:17 to 13:

7.

3. The preparation method according to claim 1, characterized in that, The molar ratio of zinc in the zinc salt to sulfur in the thiourea is 1:2.5~3.

5.

4. The preparation method according to claim 1 or 3, characterized in that, The concentration of zinc salt in the mixture is 0.2~0.3 mol / L.

5. The preparation method according to claim 1, characterized in that, The zinc salt is zinc sulfate.

6. The preparation method according to claim 1, characterized in that, The mixing of the mixed solvent, zinc salt, and thiourea includes the following steps: mixing the mixed solvent and zinc salt, first stirring to obtain a zinc precursor solution; mixing the zinc precursor solution and thiourea, second stirring to obtain the mixed solution.

7. The preparation method according to claim 6, characterized in that, The first and second stirring speeds are independently 200~300 rpm, and the time is independently 20~40 min.

8. The preparation method according to claim 1, characterized in that, The solvothermal reaction is carried out at a temperature of 140~180℃ for a time of 14~18h.

9. The preparation method according to claim 1, characterized in that, After the solvothermal reaction, the process further includes: performing solid-liquid separation on the obtained reaction liquid and collecting the precipitate; washing and drying the precipitate in sequence to obtain the zinc sulfide from wurtzite.

10. The preparation method according to claim 9, characterized in that, The solid-liquid separation method is vacuum filtration; the washing reagent is water; the drying temperature is 50~70℃ and the time is 4~6h.

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