CuS / Cu9S8 heterojunction photocatalyst and preparation method and application thereof

Abstract

The application relates to a CuS / Cu9S8 heterojunction photocatalyst and a preparation method and application thereof, and belongs to the technical field of photocatalytic materials. The preparation method of the CuS / Cu9S8 heterojunction photocatalyst comprises the following steps: dissolving Cu(CH3COO)2.H2O and a surfactant polyvinylpyrrolidone in a solvent, stirring and mixing, adding a sulfur source to continue stirring and reaction, washing, drying, and preparing the CuS / Cu9S8 heterojunction photocatalyst. The CuS / Cu9S8 heterojunction photocatalyst improves photocatalytic sterilization effect, and can realize almost 100% killing rate of escherichia coli and bacillus subtilis in 10 minutes. The heterojunction structure constructed in the application adjusts the energy band structure of single copper sulfide, promotes the generation of free radicals under near-infrared light, and improves the photo-thermal performance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photocatalytic materials, in particular to a CuS / Cu9S8 heterojunction photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] In recent years, photothermal antibacterial means based on near-infrared light irradiation has attracted the attention of researchers. Photothermal agents can convert near-infrared radiation into a large amount of heat, thereby weakening bacterial protein activity and energy synthesis, and ultimately leading to bacterial death. However, single photothermal action cannot achieve high-efficiency sterilization. Photocatalytic technology is considered as a promising and sustainable method for solving bacterial pollution problems due to its environmental friendliness and low cost. However, most photocatalysts have poor light absorption capacity, fast recombination rate of photo-generated electron-hole pairs, and low photocatalytic efficiency.

[0003] CuS is not only a multifunctional synthetic material with good chemical stability, but also a newly discovered new material with high-efficiency visible light catalytic activity which can be regulated. However, the recombination rate of photo-generated electron-hole pairs of single copper sulfide is high, the photocatalytic activity is low, and the photothermal efficiency is low. Therefore, it is urgent to construct an efficient antibacterial agent.

[0004] The application improves the photocatalytic activity by constructing a heterojunction structure of two single copper sulfide materials. Compared with single copper sulfide, the prepared CuS / Cu9S8 heterojunction photocatalyst has high-efficiency sterilization performance. SUMMARY

[0005] To solve the above technical problems, the application provides a CuS / Cu9S8 heterojunction photocatalyst, a preparation method and application thereof, and aims to construct different copper sulfide crystal forms, form a copper sulfide heterojunction, and finally obtain high-efficiency photocatalytic performance and photothermal performance, so that 100% sterilization effect can be achieved.

[0006] The application is achieved by the following technical scheme:

[0007] The first object of the application is to provide a preparation method of a CuS / Cu9S8 heterojunction photocatalyst, characterized by comprising the following steps:

[0008] Cu(CH3COO)2.H2O and a surfactant are dissolved in a solvent, mixed by stirring, a sulfur source is added for continuous stirring reaction, washing, and drying, so that the CuS / Cu9S8 heterojunction photocatalyst is prepared.

[0009] In an embodiment of the application, the surfactant is polyvinylpyrrolidone; and the molecular weight of the polyvinylpyrrolidone is 40000-50000.

[0010] In one embodiment of the present application, the mass ratio of Cu(CH3COO)2·H2O to surfactant is 3:4-4:5.

[0011] In one embodiment of the present application, the solvent is polyethylene glycol; the molecular weight of the polyethylene glycol is 400; and the sulfur source is selected from thiourea.

[0012] In one embodiment of the present application, the reaction temperature is 170-190℃.

[0013] In one embodiment of the present application, the reaction time is 20-22h.

[0014] A second object of the present application is to provide a CuS / Cu9S8 heterojunction photocatalyst prepared by the preparation method.

[0015] A third object of the present application is to provide an application of the CuS / Cu9S8 heterojunction photocatalyst in sterilization.

[0016] In one embodiment of the present application, the concentration of the CuS / Cu9S8 heterojunction photocatalyst is ≥50μg / mL.

[0017] In one embodiment of the present application, the sterilization is performed under light with a wavelength of 808nm; and the sterilization time is ≤10min.

[0018] The mechanism of the present application is that, compared with single CuS and Cu9S8, the formation of CuS / Cu9S8 heterojunction improves the separation efficiency of photo-generated electron-hole pairs, more photo-generated charge carriers participate in redox reactions to produce reactive oxygen, and the photocatalytic sterilization performance is improved. In addition, the excessive heat generated by CuS / Cu9S8 accelerates the death of bacteria.

[0019] The above technical solution of the present application has the following advantages compared with the prior art:

[0020] 1. The CuS / Cu9S8 heterojunction photocatalyst of the present application improves the photocatalytic sterilization effect, and can achieve almost 100% killing rate of E. coli and B. subtilis in 10min.

[0021] 2. The CuS / Cu9S8 nano photocatalyst of the present application can effectively kill Gram-negative bacteria and Gram-positive bacteria, such as E. coli and B. subtilis.

[0022] 3. The heterojunction structure constructed in the present application adjusts the energy band structure of single copper sulfide, promotes the generation of free radicals under near-infrared light, and improves the photo-thermal performance. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to make the content of the present application more easily understood, the present application is further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings, in which

[0024] Figure 1 is a scanning electron microscope image of CuS (a), Cu9S8 (b) and CuS / Cu9S8 (c) in the test example of the present application;

[0025] Figure 2 is an XRD spectrum of CuS / Cu9S8 (a), CuS (a) and Cu9S8 (c) in the test example of the present application;

[0026] Figure 3 is a bactericidal effect diagram of the photocatalyst in the test example of the present application; wherein a is the antibacterial activity of CuS, Cu9S8 and CuS / Cu9S8 on E. coli under darkness and light; b is the bactericidal efficiency of CuS, Cu9S8 and CuS / Cu9S8 on E. coli under darkness and light; c is the antibacterial activity of CuS, Cu9S8 and CuS / Cu9S8 on B. subtili under darkness and light; d is the bactericidal efficiency of CuS, Cu9S8 and CuS / Cu9S8 on B. subtili under darkness and light;

[0027] Figure 4 is a photo-thermal performance diagram of the photocatalyst in the test example of the present application; wherein a is the temperature of CuS / Cu9S8 aqueous solution after light irradiation at different concentrations; b is the temperature change of different catalysts under near-infrared light irradiation;

[0028] Figure 5 is an electrochemical impedance diagram (a) and a photoelectric current response diagram (b) of the photocatalyst in the test example of the present application. DETAILED DESCRIPTION

[0029] The present application is further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting the present application.

[0030] Example 1

[0031] The present embodiment provides a preparation method of a CuS / Cu9S8 heterojunction photocatalyst, comprising the following steps:

[0032] 0.3 g Cu(CH3COO)2·H2O and 0.4 g polyvinylpyrrolidone (PVP 40000) were dissolved in 40 mL polyethylene glycol (PEG 400) and stirred continuously for 30 minutes. Then, 0.4 g thiourea was added to the above solution, and stirring was continued for 20 minutes. The mixture was then transferred to a 50 mL high-temperature reactor and reacted at 180 °C for 20 hours. After the reaction was completed, the product was washed several times with ultrapure water and anhydrous ethanol and dried in a 60 °C oven to finally obtain the CuS / Cu9S8 heterojunction photocatalyst.

[0033] Comparative Example 1

[0034] This comparative example provides a method for preparing a Cu9S8 photocatalyst, including the following steps:

[0035] 0.6 g of Cu(CH3COO)2·H2O was dissolved in 35 mL of anhydrous ethanol. Then, 0.228 g of thiourea was added to the solution while stirring continuously until it was uniformly dispersed. Subsequently, the resulting solution was transferred to a 50 mL high-temperature reactor and reacted at 150 °C for 10 hours. After naturally cooling to room temperature, the product was washed several times with ultrapure water and anhydrous ethanol and dried at 60 °C.

[0036] Comparative Example 2

[0037] This comparative example provides a method for preparing a CuS photocatalyst, including the following steps:

[0038] Add 1 mmol Cu(NO3)2·3H2O to 40 mL of ultrapure water and stir until homogeneous. Then add 2 mmol thioacetamide, stir for 30 minutes, transfer the solution to a 50 mL high-temperature reactor, and react at 180 °C for 6 hours. After naturally cooling to room temperature, wash the product several times with ultrapure water and anhydrous ethanol, and dry at 60 °C.

[0039] Test case

[0040] (1) Scanning electron microscope images of CuS, Cu9S8, and CuS / Cu9S8 prepared in the comparative examples and embodiments are shown below. Figure 1 As shown. By Figure 1 It can be seen that the photocatalysts all exhibit a plate-like morphology.

[0041] (2) X-ray diffraction (XRD) patterns of CuS, Cu9S8, and CuS / Cu9S8 prepared in the comparative examples and embodiments are shown below. Figure 2 As shown. By Figure 2It can be seen that the diffraction peaks of CuS alone match the standard data of hexagonal phase CuS (JCPDS 06-0464), and the diffraction peaks of Cu9S8 all match the standard spectrum of hexagonal phase Cu9S8 (JCPDS 36-0379), indicating that the prepared CuS and Cu9S8 are pure phases. At the same time, the XRD diffraction pattern of the CuS / Cu9S8 composite only has the diffraction peaks of CuS and Cu9S8, without other impurity peaks, indicating that the pure phase CuS / Cu9S8 heterojunction is successfully synthesized.

[0042] (3) Bactericidal effect: The classic plate counting method was used to evaluate the bactericidal effect of the photocatalyst.

[0043] E. coli and B. subtili were cultured in Luria-Bertani medium to the mid-log phase (OD ≈ 0.8), and then washed with normal saline for 3 times for standby. Take the bacterial liquid (2 × 10 6 CFU / mL) and mix evenly with the prepared photocatalyst (50 μg / mL), and incubate in a shaking incubator in the dark for 30 min. Then irradiate 1 mL of the co-cultured bacterial liquid with near-infrared light (NIR, 808 nm 1.5 W / cm 2 ) for 10 min. Gradient dilute the bacterial liquid and take 100 μL and drop on the agar plate, evenly spread with a spreader, and take out after 24 hours of incubation in a 37°C incubator for colony counting. Finally, calculate the bactericidal efficiency.

[0044] As shown in Figure 3 , the antibacterial activity of CuS, Cu9S8 and CuS / Cu9S8 in the dark can be ignored, and there is no difference in the number of colonies compared with the blank control group. At the same time, it is observed that near-infrared light itself does not cause bacterial activity in the control group. After 10 minutes of irradiation, the bactericidal efficiency of CuS / Cu9S8 heterojunction on E. coli and B. subtilis is more than 99%. The antibacterial efficiency of pure CuS and Cu9S8 on E. coli (B. subtilis) is 77.02% (79.54%) and 68.55% (73.91%), respectively, and cannot completely kill bacteria.

[0045] (4) Photothermal performance

[0046] In order to compare and investigate the photothermal performance of CuS, Cu9S8 and CuS / Cu9S8, the temperature change of the three materials under near-infrared light was detected by an infrared thermometer. As shown in Figure 4As shown, the temperature of pure water increased from 25℃ to 33.2℃, while the temperature of CuS, Cu9S8 and CuS / Cu9S8 solution increased from 25.0℃ to 51.2℃, 49.7℃ and 54.1℃, respectively, which indicated that the CuS / Cu9S8 heterojunction produced the most heat, which helped to kill bacteria. At the same time, the results showed that the temperature of CuS / Cu9S8 aqueous solution after light irradiation was positively correlated with the concentration of the material.

[0047] (5) Photoelectric performance measurement

[0048] In order to further analyze the excellent photocatalytic activity of CuS / Cu9S8 heterojunction, the inventors measured the photoelectrochemical performance of the catalyst. The results are shown in Figure 5 As shown in a of the figure, the radius of the arc of CuS / Cu9S8 is the smallest, indicating that the impedance of CuS / Cu9S8 is the lowest, indicating that the migration of photo-induced charge carriers inside is easier. Figure 5 As shown in b of the figure, the photocurrent response of CuS / Cu9S8 is enhanced compared with CuS and Cu9S8, which proves that the separation efficiency of photo-induced electron-hole pairs of CuS / Cu9S8 is the highest, and the separated holes and electrons can more efficiently react with oxygen or water molecules, thereby generating a large amount of active oxygen, improving the photocatalytic bactericidal efficiency.

[0049] Obviously, the above examples are only examples for clarity, and are not limited to the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a CuS / Cu9S8 heterojunction photocatalyst, characterized in that, Includes the following steps: Cu(CH3COO)2·H2O and a surfactant were dissolved in a solvent, stirred and mixed, a sulfur source was added and the reaction was continued with stirring, washed and dried to prepare the CuS / Cu9S8 heterojunction photocatalyst. The surfactant is polyvinylpyrrolidone; The mass ratio of Cu(CH3COO)2·H2O to surfactant is 3:4~4:5; The solvent is polyethylene glycol; the sulfur source is selected from thiourea. The reaction temperature is 170℃~190℃; The reaction time is 20 h to 22 h.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the polyvinylpyrrolidone is 40,000 to 50,000.

3. The CuS / Cu9S8 heterojunction photocatalyst prepared by the preparation method according to any one of claims 1-2.

4. The application of the CuS / Cu9S8 heterojunction photocatalyst according to claim 3 in sterilization.

5. The application according to claim 4, characterized in that, The concentration of the CuS / Cu9S8 heterojunction photocatalyst is ≥50 μg / mL.

6. The application according to claim 4, characterized in that, The sterilization is carried out under light with a wavelength of 808 nm; the sterilization time is ≤10 min.

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