A method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand and its application

Abstract

This application discloses a method for synthesizing CdS quantum dots with β-mercaptoethanol as a ligand and its applications, relating to the field of chemical synthesis technology. The CdS quantum dots have a particle size of 5-7 nm, a hexagonal wurtzite structure, and their surface is modified with β-mercaptoethanol via ligand exchange. The preparation method involves first preparing CdS quantum dots with oleic acid ligands via a hot-injection method, and then performing ligand exchange with β-mercaptoethanol under alkaline conditions. These quantum dots can efficiently catalyze the breaking of carbon-oxygen bonds in lignin β-O-4 model compounds under visible light irradiation, achieving a conversion rate of up to 100% and exhibiting good cycle stability. This invention provides a new approach for the design of CdS-based photocatalysts and has green and sustainable application prospects in the fields of lignin resource utilization and wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand and its application. Background Technology

[0002] With increasing global emphasis on green and sustainable development strategies, the chemical synthesis industry is facing an urgent need to transform towards environmentally friendly and atom-economical approaches. Photocatalysis, hailed as a green technology of "artificial photosynthesis," offers a highly promising green pathway for synthesizing high-value fine chemicals by directly driving the breaking and recombination of chemical bonds using inexhaustible solar energy. Cadmium sulfide quantum dots (CdS quantum dots, or CdS QDs) demonstrate great potential in the field of photo-driven organic conversion due to their suitable visible light absorption range and unique quantum size effect. However, the catalytic performance of quantum dots is highly dependent on their surface chemistry, making "surface ligand engineering" a crucial core technology determining the success or failure of their practical applications.

[0003] However, traditional ligand selection still faces many limitations. For example, long-chain alkyl thiols, due to their dense hydrocarbon chain structure, form a dense insulating layer on the quantum dot surface, resulting in a significant "charge insulation" effect that severely hinders the interfacial transport of photogenerated carriers. Common short-chain carboxylic acid ligands (such as 3-mercaptopropionic acid) can improve hydrophilicity, but these ligands are prone to detachment in complex reaction systems and have weak coordination strength, leading to catalyst deactivation. Summary of the Invention

[0004] This application provides a method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand and its application, which solves the problem of easy catalyst deactivation in the prior art.

[0005] This application provides a method for synthesizing CdS quantum dots with β-mercaptoethanol as a ligand. The CdS quantum dots have β-mercaptoethanol as the surface ligand, a particle size of 5-7 nm, and a hexagonal wurtzite crystal structure.

[0006] Furthermore, this includes the following steps: (1) Preparation of CdS quantum dots with oleic acid ligands: Under an inert atmosphere, cadmium source and oleic acid were dissolved in 1-octadecene and heated to 280 °C to form a clear solution. Sulfur source solution was injected and reacted at 220 °C for 1 h. After cooling, CdS-OA was obtained by washing, centrifugation and dispersion. (2) Ligand exchange: β-mercaptoethanol was dissolved in ethanol, and the pH was adjusted to 14 with tetramethylammonium hydroxide solution. CdS-OA obtained in step (1) was added, and the mixture was stirred for 4 h in the dark under nitrogen protection at 55 °C. After the reaction was completed, CdS quantum dots with β-mercaptoethanol as ligand were obtained by rotary evaporation, washing and dispersion.

[0007] Furthermore, the cadmium source is cadmium oxide, the sulfur source is elemental sulfur, and the molar ratio of cadmium to sulfur is 1:2.

[0008] Furthermore, in step (2), the amount of β-mercaptoethanol used is 1.40 mL of β-mercaptoethanol per 2 mL of CdS-OA.

[0009] The above-mentioned application of CdS quantum dots with β-mercaptoethanol as a ligand in visible light photocatalysis is applied to the breaking of lignin model compounds (2-phenoxy-1-phenylethanol, i.e., PP-ol) C β Photocatalytic reactions of -O bonds.

[0010] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: Existing CdS quantum dot photocatalyst technology suffers from a fundamental flaw: the molecular design of its surface ligands results in a mutually exclusive and incompatible relationship between the two core properties of "stability" and "efficiency." This inherent contradiction determines its poor performance in real-world applications.

[0011] This deficiency is exposed in the typical scenario of visible light-driven organic synthesis in aqueous phases or polar solvents. This scenario requires catalysts to not only efficiently complete a single reaction cycle under ambient temperature and pressure, visible light irradiation, and an inert atmosphere, but also to withstand multiple cycles of use. Under these harsh conditions, traditional ligands have two shortcomings: long-chain ligands, while stable, severely hinder charge and reactant transport; short-chain ligands, while improving initial efficiency, are rapidly deactivated due to weak bonding.

[0012] This contradiction directly results in the inability to meet the core demands of different application subjects. The pursuit of high performance (>90% conversion rate) often comes at the cost of sacrificing the cyclic stability of the catalyst, making the data difficult to reproduce; while the stability and reliability (cycle decay <20%) required by process engineers are not achieved due to the rapid deactivation of the catalyst, increasing the cost of use and the complexity of operation.

[0013] Ultimately, all of the above problems manifest as quantifiable, significant performance deviations. Long-chain ligands reduce the interfacial charge transfer rate by 1-2 orders of magnitude; while short-chain ligands cause the catalyst activity to decline by more than 50% after several cycles, far below the threshold for industrial applications.

[0014] Choosing β-mercaptoethanol as the ligand offers unique advantages in its molecular structure: Strong anchoring groups (-SH): Thiol groups (-SH) and Cd on the CdS surface 2+ It forms a strong Cd-S covalent bond with a bond energy much higher than that of the coordinate bond of the carboxylate group, providing high binding stability similar to long-chain thiols, ensuring that the ligand is not easily detached during catalytic cycling.

[0015] Ultrashort carbon chain (C2): The ultrashort chain structure with only two carbon atoms greatly reduces the steric hindrance and insulation effect of the ligand layer, enabling photogenerated electrons / holes to migrate to the quantum dot surface more quickly to participate in the reaction, thus ensuring the high efficiency of charge transport.

[0016] Hydrophilic ends (-OH): The hydroxyl groups at the ends make the quantum dot surface hydrophilic, which significantly improves its dispersibility in aqueous phases or polar solvents, making reactants more accessible to catalytic active sites. At the same time, the -OH group may also participate in surface state regulation, further promoting charge separation.

[0017] β-Mercaptoethanol combines strong bonding stability, ultra-short chain conductivity, and surface hydrophilicity, breaking through the performance limitations of traditional ligands from the source of molecular design.

[0018] In the model reaction, the catalyst showed no significant decrease in catalytic activity after three consecutive cycles, and the crystal structure remained intact.

[0019] Regarding the issue that "long-chain ligands reduce the interfacial charge transfer rate by 1-2 orders of magnitude": ultrashort-chain β-mercaptoethanol greatly reduces the energy barrier, enabling the charge transfer rate to recover to or even exceed the level of conventional short-chain ligands. This is indirectly proven by the extremely high photocatalytic conversion efficiency.

[0020] Regarding the issue that "short-chain ligands often cause catalyst activity to decline by more than 50% after several cycles": strong Cd-S bonding ensures structural stability, maintains stable performance after three cycles, and has an activity decline of far less than 20%, meeting the stability threshold requirements for industrial applications.

[0021] The underlying logic of this technical solution lies in using β-mercaptoethanol, which possesses a unique three-in-one characteristic of "strong anchoring group - ultra-short chain structure - hydrophilic end," as a ligand to achieve precise control over the surface properties of CdS quantum dots at the molecular level. It overcomes the stability limitations of short-chain ligands through strong covalent bonding and circumvents the charge transport barriers of long-chain ligands through its minimalist carbon chain structure. This achieves a balance between high catalytic activity and high cycling stability in both experimental and practical applications, successfully addressing the fundamental deficiency of traditional CdS quantum dot photocatalysts in poor performance in real-world applications. Attached Figure Description

[0022] Figure 1 The XRD patterns of CdS-OA and CdS-BME of this invention; Figure 2 The FT-IR spectra of CdS-OA and CdS-BME of this invention; Figure 3 These are TEM images and HRTEM images of CdS-BME according to the present invention; Figure 4 The UV-Vis DRS spectra of CdS-OA and CdS-BME of this invention; Figure 5 XPS spectra of CdS-OA and CdS-BME in the Cd 3d region and XPS spectra of CdS-OA and CdS-BME in the S 2p region of this invention; Figure 6 This is a diagram of the catalytic reaction of the catalyst in this invention; Figure 7 The stability test of CdS-BME for PP-ol by visible light driving according to the present invention and the XRD spectra of CdS-BME before and after reaction are shown.

[0023] Figure 3 (a) TEM image of CdS-BME; (b) HRTEM image of CdS-BME (c inside is a magnified HRTEM image). Figure 5 (a) XPS spectra of CdS-OA and CdS-BME in the Cd 3d region; (b) XPS spectra of CdS-OA and CdS-BME in the S 2p region; Figure 7 (a) Stability test of CdS-BME driven by visible light to achieve PP-ol; (b) XRD patterns of CdS-BME before and after the reaction. Detailed Implementation

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] Example 1: A method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand, comprising the following steps: Preparation of CdS-OA: A mixture of 1-octadecene (36 mL), CdO (0.3852 g, 3 mmol) and oleic acid (5 mL) was placed in a three-necked flask and heated to 120 °C under a nitrogen atmosphere and held for 20 min. Then the mixture was heated to 280 °C and held until the solution became clear (10 min) to obtain solution A.

[0026] Immediately afterwards, a mixture of 1-octadecene (2 mL) containing sulfur (0.192 g, 6 mmol) was rapidly injected into solution A and heated at 220 °C for 1 h.

[0027] After the reaction was complete, the system was cooled to room temperature in an ice bath. The reaction product was transferred to a centrifuge tube, and a mixture of anhydrous ethanol and chloroform was added. After thorough dispersion, the tube was centrifuged, and the supernatant was discarded. The precipitate was redissolved in a small amount of chloroform, and a large amount of acetone was added to redefine the quantum dots. The mixture was centrifuged again, and this process was repeated three times. The resulting sample was dispersed in chloroform (6 mL) and stored, named CdS-OA, with a concentration of 64.2 mg / mL.

[0028] Preparation of CdS-BME: β-mercaptoethanol (1.40 mL, 19.96 mmol) was dispersed in ethanol (25 mL). Tetramethylammonium hydroxide ethanol solution (TMAOH, 0.5 M) was slowly added dropwise under stirring to precisely adjust the pH of the mixed solution to 14 ± 0.2, obtaining solution B. Subsequently, 2 mL of CdS-OA was injected into solution B, and the mixture was stirred in the dark at 55 °C under N2 atmosphere for 4 h. After the reaction was complete, the resulting product was rotary evaporated, washed with ethanol, dispersed in deionized water (0.2 mL), and stored in the dark. This product was named CdS-BME with a concentration of 50 mg / mL.

[0029] The crystal structure of the sample was analyzed by XRD. The target material of the instrument was Cu Kα, the incident wavelength was 0.154 nm, and the operating current and voltage were 40 mA and 40 kV, respectively. Before the test, the powder sample to be tested was placed in the groove of the matching XRD powder diffraction plate and pressed firmly with a glass plate. Then, the plate was horizontally inserted into the sample slot of the instrument. After setting the scanning range (20-70° (2θ)), scanning rate (2° / min), and scanning step size (0.02°), the test was carried out. The results show that CdS-OA has characteristic diffraction peaks at 2θ of 24.8°, 26.5°, 28.1°, 36.6°, 43.6°, 47.8° and 51.8°, respectively, which correspond one-to-one with the (100), (002), (101), (102), (110), (102) and (112) crystal planes of hexagonal wurtzite CdS (JCPDS No. 41-1049); Figure 1As shown, the XRD pattern of the obtained CdS-BME is similar to that of CdS-OA, indicating that the ligand exchange process did not change the crystal structure of CdS.

[0030] The sample was analyzed using an IS10 infrared spectrometer. Before conducting the formal testing, the instrument needed to be calibrated using potassium bromide (KBr) to effectively eliminate background interference and ensure the accuracy of the test data. The specific operating procedure is as follows: (1) Background calibration: High-purity KBr was used to carry out background scanning. After the background signal stabilized, an accurate reference standard was obtained to lay the foundation for subsequent sample measurement.

[0031] (2) Sample preparation: Mix the test material and KBr powder thoroughly at a mass ratio of 1:50, and grind them to achieve a homogeneous state. To avoid the sample from getting damp in the air, the mixture after grinding can be temporarily stored under an infrared lamp.

[0032] (3) Tableting operation: Put the well mixed sample into the tablet press and press it under a pressure of 10 MPa to obtain a uniform thin film suitable for testing.

[0033] (4) Data acquisition: In the actual test, the number of instrument scans was set to 64 to collect sufficient data points and ensure that the experimental results have high reliability and accuracy.

[0034] The results are as follows Figure 2 As shown, CdS-OA at 2921 cm⁻¹ -1 and 2848 cm -1 The absorption peak at 1558 cm⁻¹ corresponds to the asymmetric stretching vibration of the methylene group on the oleic acid ligand and the symmetric stretching vibration of the methylene group. -1 and 1417 cm -1 The absorption peaks at these locations correspond to the asymmetric stretching vibration and symmetric vibration of the carboxylate group, respectively, with a difference of 141 cm⁻¹. -1 This indicates that the carboxylate ion coordinates with the Cd ion in a bridging manner; after ligand exchange, the absorption peak attributable to the carboxylate ion on CdS-BME disappears, while the absorption peak at 1403 cm⁻¹ disappears. -1 Location, 1046 cm -1 and 1001 cm -1 A new absorption peak appeared at 1403 cm⁻¹. -1 The absorption peak at 1046 cm⁻¹ corresponds to the in-plane bending vibration of the OH group of the BME ligand attached to the CdS surface. -1 and 1001 cm -1 The absorption peak at that point corresponds to the C-OH stretching vibration.

[0035] The morphology, particle size and other microstructure of the sample were characterized using a Jem-2100F transmission electron microscope (TEM), with the instrument's accelerating voltage set to 200 kV. At the same time, a high-resolution transmission electron microscope (HRTEM) was used to analyze the lattice fringe structure of each crystal plane in the sample in a detailed manner.

[0036] like Figure 3 TEM results show that the synthesized CdS-BME quantum dots are uniformly dispersed with a diameter of approximately 6 nm. HRTEM analysis of CdS-BME further revealed lattice fringes with a spacing of 0.36 nm, corresponding to the (100) crystal plane of hexagonal wurtzite CdS, further confirming the successful synthesis of CdS-BME.

[0037] The light absorption range of the samples was determined using a Varian Cary 5000 UV-Vis-NIR spectrometer. The scanning wavelength range was 200 to 800 nanometers. Figure 4 Compared with CdS-OA, CdS-BME showed a significant increase in light absorption intensity between 473 nm and 800 nm, which may be due to the ligand β-mercaptoethanol.

[0038] The sample was analyzed using X-ray powder diffraction, and the results are as follows: Figure 5 The XPS spectra of CdS-OA showed Cd 3d at 405.00 eV and 411.74 eV. 5 / 2 and Cd 3d 3 / 2 The characteristic peaks, and the S2p peaks at 161.50 eV and 162.68 eV, indicate the presence of S2p. 3 / 2 and S 2p 1 / 2 Characteristic peaks. It is worth noting that, in comparison, the XPS spectrum of CdS-BME on S 2p, except for the S 2p peaks attributed to CdS... 3 / 2 and S 2p 1 / 2 In addition to the characteristic peaks (161.35 eV and 162.53 eV), another set of S 2p peaks was observed at 162.48 eV and 163.66 eV. 3 / 2 and S 2p 1 / 2 The characteristic peaks may be attributed to the β-mercaptoethanol ligand on the CdS surface. In addition, the XPS spectra of CdS-BME show Cd 3d... 5 / 2 and Cd 3d 3 / 2 The characteristic peaks are shown above. The results clearly demonstrate that CdS quantum dots with β-mercaptoethanol as ligands were successfully synthesized by a combination of hot-injection and ligand exchange methods.

[0039] Example 2: Using the CdS-BME prepared above as a catalyst, the effect of its C-cleavage mechanism on the lignin β-O-4 model compound PP-ol was studied under visible light. β -O bond performance.

[0040] The visible light cleavage of the β-O-4 model compound C was performed. β For the -O bond reaction, PP-ol was used as a model, and a Schlenk tube was used as a closed reaction vessel. The specific procedure was as follows (using CdS-BME as an example): CdS-BME catalyst (200 µL, i.e., 10 mg), PP-ol (0.0214 mg, 0.1 mmol), and acetonitrile (2 mL) were placed in a 10 mL Schlenk tube and sealed. Nitrogen gas was then bubbled into the reaction tube to remove dissolved oxygen from the solvent. After 7 min of bubbling, the Schlenk tube was sealed and placed under a blue LED lamp for 3 h of reaction. The magnetic stirring speed was 800 rpm / min during the reaction. After the reaction, the reaction mixture was filtered through a 0.22 μm nylon filter membrane and the products were qualitatively and quantitatively analyzed by HPLC.

[0041] The conversion rate of PP-ol and the yields of phenol, acetophenone, and 2-phenoxy-1-phenylethanone (PP-one) are calculated as follows: PP-ol conversion rate (%) = [(C0-C...] PP-ol ) / C0] × 100%; Yield of phenol (%) = C 苯酚 / C0× 100%; Yield of acetophenone (%) = C 苯乙酮 / C0 × 100%; Yield of PP-one (%) = C PP-one / C0 × 100%; Where C0 is the initial concentration of PP-ol, C PP-ol C 苯酚 C 苯乙酮 and C PP-one The concentrations of reactant PP-ol and products phenol, acetophenone, and PP-one after the reaction are respectively. The experimental results are shown in Table 1, and the reaction principle is as follows: Figure 6 After 3 hours of visible light irradiation, the CdS-BME system achieved 100% conversion of PP-ol, producing 94.56% and 93.77% of the bond-breaking products acetophenone (b) and phenol (c), respectively. A small amount of oxidation product PP-one (c) of 5.02% was also detected in this system. No product formation was observed under either dark or catalyst-free conditions, indicating that the conversion of PP-ol was indeed induced by visible light-driven CdS-BME.

[0042] Table 1 Experimental Results of Example 2

[0043] To evaluate the stability of the catalyst, the cyclic performance of the CdS-BME catalytic system was tested, such as... Figure 7 As shown in (a), the system maintains good catalytic performance after three cycles. XRD patterns before and after cycling (e.g.) Figure 7 (b) indicates that the integrity and crystallinity of CdS-BME remain basically unchanged during the cycling process. All of the above results show that the prepared CdS-BME has good photocatalytic activity stability.

[0044] Example 3: Catalytic experiments were conducted in a real, complex environment.

[0045] The experiment focused on the degradation of black liquor in papermaking and the extraction of aromatic monomers; Inlet water (black liquor) characteristic parameters: Source: Black liquor produced during the sulfate pulping process (kraft paper process).

[0046] Processing stage: The medium-concentration black liquor that enters the resource utilization treatment unit after multi-effect evaporation and concentration.

[0047] Key physical parameters: Lignin concentration: 51.9 g / L (on dry solids).

[0048] Chemical oxygen demand (COD): 115305 mg / L, high organic load.

[0049] pH value: 13.4, strongly alkaline, derived from NaOH and Na2S used in the pulping process.

[0050] Solid content: 19%, viscous, containing a large amount of inorganic salts (mainly Na2SO4 and Na2CO3) and organic matter.

[0051] Color: Extremely dark, blackish-brown.

[0052] Blackwater volume: 9000L; Because black water is dark in color, has a certain viscosity, and low light transmittance, it has a significant impact on the catalytic effect. Therefore, improvements are needed when applying this catalyst.

[0053] Preparation of catalytically active membrane slurry: Raw materials: CdS-BME (solution, 50 mg / mL), film-forming binder (alkali-resistant silica sol, aluminum modified), leveling agent (polyether modified siloxane), dispersion medium (50% ethanol solution).

[0054] Formulation and preparation: Mix CdS-BME and film-forming binder at a mass ratio of 7:1, add a small amount of leveling agent (0.3% of the total mass), and slowly add the dispersion medium using a high shear disperser at a speed of 2000-5000 rpm to finally prepare a uniform slurry with a solid content of 15%. Black liquor pretreatment: Pump the black liquor into the reactor, control the temperature at 80±1℃, and turn on the low-speed stirring at the bottom (100rpm) to make the temperature and composition of the black liquor uniform. Catalytically active film: Under low-speed stirring, the "catalytically active film slurry" is uniformly sprayed onto the surface of the black liquor in an atomized form through a spraying system; the spraying should be carried out in 3 times, with a 1-minute interval between each spraying, to allow the liquid surface tension to level the film and allow part of the dispersion medium to evaporate or integrate into the surface of the black liquor, ultimately forming a continuous and uniform catalytically active film with a thickness of about 0.5-2 mm on the liquid surface. The catalyst loading is calculated based on the total amount of black liquor and is 1.5 g / L (based on the mass of CdS-BME). Illumination system startup: A high-power visible light LED surface light source array (main wavelength 420-450nm) is arranged at the top of the reactor, uniformly covering the entire liquid surface with a surface light intensity ≥150 mW / cm². 2 Turn on the light source; Start stirring and adjust the speed to 300 rpm to continuously "pump" the unreacted black liquor at the bottom to the surface, where it comes into contact with the catalytic membrane. At the same time, the material after the surface reaction is carried into the main body to achieve the circulation and renewal of the material in the whole reactor, with the assistance of a trace amount of nitrogen gas (0.1 vvm) blown in from the bottom of the reactor. Reaction proceeded as follows: Under the synergistic effect of light irradiation and forced surface renewal, the catalytic membrane continued to function. The reaction temperature was maintained at 80°C, and the reaction time was 5 hours. After the reaction was completed, the light source and stirring were turned off.

[0055] The control group directly added the calculated amount of CdS-BME into 9000L of black liquor and attempted to disperse it by stirring (300 rpm); After the reaction, the lignin concentration decreased by 48.2%, the COD removal rate was 19.6%, and the color became significantly lighter; in the control group, the lignin concentration decreased by 5.8%, the COD removal rate was 1.3%, and the color did not change significantly.

[0056] CdS-BME quantum dots with β-mercaptoethanol as a novel ligand were successfully synthesized via a hot-injection method and a ligand exchange method in an alkaline solution containing β-mercaptoethanol. Experimental results show that this catalyst can efficiently drive the realization of lignin β-O-4 model compound C under visible light. βThe catalyst exhibits excellent photocatalytic activity and stability, breaking the -O bond. This research provides new insights for developing efficient and stable CdS-based photocatalysts and offers a green and sustainable conversion pathway for the high-value utilization of lignin.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand, characterized in that, The CdS quantum dots have β-mercaptoethanol as their surface ligand, with a particle size of 5-7 nm and a hexagonal wurtzite crystal structure.

2. The method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of CdS quantum dots with oleic acid ligands: Under an inert atmosphere, cadmium source and oleic acid were dissolved in 1-octadecene and heated to 280 °C to form a clear solution. Sulfur source solution was injected and reacted at 220 °C for 1 h. After cooling, CdS-OA was obtained by washing, centrifugation and dispersion. (2) Ligand exchange: β-mercaptoethanol was dissolved in ethanol, and the pH was adjusted to 14 with tetramethylammonium hydroxide solution. CdS-OA obtained in step (1) was added, and the mixture was stirred for 4 h in the dark under nitrogen protection at 55 °C. After the reaction was completed, CdS quantum dots with β-mercaptoethanol as ligand were obtained by rotary evaporation, washing and dispersion.

3. The method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand as described in claim 1, characterized in that, The cadmium source is cadmium oxide, the sulfur source is elemental sulfur, and the molar ratio of cadmium to sulfur is 1:

2.

4. The method for synthesizing CdS quantum dots using β-mercaptoethanol as a ligand as described in claim 1, characterized in that, In step (2), the amount of β-mercaptoethanol used is 1.40 mL of β-mercaptoethanol per 2 mL of CdS-OA.

5. The application of CdS quantum dots with β-mercaptoethanol as a ligand as described in claim 1 in visible light photocatalytic reactions, characterized in that, It is applied to the catalytic reaction of lignin.

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