Graphite phase carbon nitride / vacancy bismuth oxide nanosheet composite material, preparation method and application

Abstract

The present invention discloses a graphite phase carbon nitride / vacancy bismuth oxide nanosheet composite material, a preparation method and an application thereof. The method first prepares g-C3N4 nanosheets and BiO 2‑x Nanosheets, and then g‑C3N4 nanosheets and BiO 2‑x The nanosheets were added to methanol and ultrasonically stirred to obtain g‑C3N4 / BiO 2‑x Nanocomposite material. g-C3N4 / BiO prepared by the present invention 2‑x The nanosheet composite material has both photoresponsiveness and thermal responsiveness, exhibiting good photothermal sterilization performance and making full use of visible light and near-infrared light.

Description

Technical Field

[0001] The present invention belongs to the field of bactericidal materials and relates to a graphite phase carbon nitride nanosheet / vacancy bismuth oxide nanosheet composite material (gC 3 N 4 / BiO 2-x ) and its preparation method, and its application in photothermal sterilization. Background Art

[0002] Semiconductor-assisted photocatalytic sterilization is a new sterilization method that uses solar energy to disinfect microorganisms without producing undesirable byproducts. However, most existing photocatalysts can only use ultraviolet light and visible light, which account for 4% and 46% of the solar spectrum respectively, and cannot use near-infrared (NIR) light, which constitutes the largest part of the solar spectrum. Therefore, photocatalysts that can efficiently use near-infrared light have broad application prospects.

[0003] Vacant bismuth oxide (BiO 2-x ) nanosheets have simple preparation process, two-dimensional layered structure and mixed valence (Bi 3+ 、Bi 5+ ) and other characteristics. At the same time, BiO 2-x The band gap of the nanosheets is relatively narrow (generally less than 2 eV), which can show satisfactory light absorption in the UV-Visible-NIR range. More importantly, BiO 2-x The nanosheets occupy a large number of oxygen vacancies, which can serve as active centers and capture electrons, thereby enhancing the key steps in the photocatalytic process. These properties make BiO 2-x Nanosheets are widely used in hydrogen production, degradation of organic pollutants and activation of O 2 However, BiO 2-x The photocatalytic activity of nanosheets is still limited by the high recombination of photoexcited charge transfer. For this problem, constructing heterojunctions is considered to be an effective modification strategy.

[0004] Graphitic carbon nitride (gC 3 N 4 ) nanosheets have attracted extensive attention in photocatalytic sterilization. He et al. constructed an oxidized Sb / gC by a one-step liquid phase exfoliation method using concentrated sulfuric acid. 3 N 4Nanosheet heterojunction improves its photocatalytic disinfection activity against Escherichia coli K-12 (E. coli K-12) under visible light irradiation (Journal of Colloid and Interface Science, 2022, 606: 1284-1298). Its special two-dimensional layered structure enables a high contact area between the supported catalyst and the substrate catalyst, promoting the transfer of electrons from the layer to the surface active center. Recent studies have shown that Bi 2 O 3 With gC 3 N 4 Four combinations of nanosheets, using one-step calcination method (Separation & Purification Technology, 2018, 203: 301-309), calcination-photoreduction method (Separation & Purification Technology, 2018, 193: 232-241), in-situ deposition method (Chemical Engineering Journal, 2019, 392: 123686) and ultrasonic mixing method (Ceramics International, 2020, 46: 24873-24881), all showed strong carrier separation efficiency, which provides a basis for the construction of gC 3 N 4 / BiO 2-x Heterojunction provides positive ideas and guiding directions. Summary of the invention

[0005] One of the purposes of the present invention is to provide a gC 3 N 4 / BiO 2-x The preparation method of the nanosheet composite material comprises the following specific steps:

[0006] Step 1: gC 3 N 4 Dispersed in concentrated sulfuric acid (H 2 SO 4 ), and then washed with water to obtain gC 3 N 4 Nanosheets (CNS);

[0007] Step 2: Sodium bismuthate (NaBiO 3 ) is added to a sodium hydroxide (NaOH) solution, stirred thoroughly, and then subjected to a solvent thermal reaction at 160-200°C. After the reaction is completed, the mixture is washed with water and dried to obtain BiO 2-x Nanosheets (Bov);

[0008] Step 3, under stirring, gC 3N 4 Nanosheets and BiO 2-x The nanosheets were added to methanol, ultrasonically stirred, washed with water, and dried to obtain gC 3 N 4 / BiO 2-x Nanocomposites (CNS / Bov).

[0009] Preferably, in step 1, gC 3 N 4 The ratio with concentrated sulfuric acid is 0.2:25, g:mL.

[0010] Preferably, in step 1, the concentration of concentrated sulfuric acid is 98%.

[0011] Preferably, in step 2, the solvent thermal reaction temperature is 180° C. and the reaction time is 12 h.

[0012] Preferably, in step 2, the concentration of the NaOH solution is 1M.

[0013] Preferably, in step 3, gC 3 N 4 Nanosheets and BiO 2-x The mass ratio of the nanosheets is 1 to 3:20, more preferably 1:10.

[0014] The second object of the present invention is to provide gC obtained by the above preparation method 3 N 4 / BiO 2-x Nanosheet composites.

[0015] The third object of the present invention is to provide the above-mentioned gC 3 N 4 / BiO 2-x Application of nanosheet composites for photothermal sterilization under visible and / or near-infrared light.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The gC prepared by the present invention 3 N 4 / BiO 2-x Under visible light irradiation, 10-CNS / Bov nanosheet composite material can completely kill Escherichia coli K-12 within 2 hours. 3 N 4 / BiO 2-x The nanosheet composite material showed responsiveness to near-infrared light, and under near-infrared light irradiation, the bactericidal effect of 10-CNS / Bov could reach 100% in 3 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD and FT-IR spectra of CN, CNS, Bov and different CNS / Bov doping ratios.

[0019] Figure 2 The photothermal sterilization effects of CN, CNS, Bov and different CNS / Bov ratios under visible light and near-infrared light. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0021] Example 1: Preparation of 10-CNS / Bov

[0022] (1) Weigh 0.2 g gC 3 N 4 The powder was dispersed in 25 mL of concentrated sulfuric acid and magnetically stirred for 4 h to obtain BCN. The treated BCN was dispersed in 500 mL of distilled water. Subsequently, the suspension was washed several times with deionized water to obtain CNS.

[0023] (2) Weigh 1.120 g NaBiO 3 ·2H 2 O was slowly added to 10 mL of 1 mol / L NaOH solution, and after sufficient stirring, it was transferred to a solvent thermal reactor and kept at 180°C for 12 hours. After the reaction was completed, the product was washed with water and dried under vacuum conditions to obtain Bov.

[0024] (3) Weigh 0.02 g CNS and 0.2 g Bov, place in 50 mL methanol, ultrasonicate for 30 min, and magnetically stir for 24 h. After stirring, wash with water and dry. The obtained product is recorded as 10-CNS / Bov.

[0025] Figure 1 (a) is the XRD spectrum of the material. It can be seen that after loading CNS, the XRD diffraction pattern of the 10-CNS / Bov sample is not significantly different from that of the pure Bov sample. At the same time, in the 10-CNS / Bov composite material, the (002) plane of CNS and the (111) plane of Bov are close in position, and the two peaks overlap. In addition, no other impurity peaks were detected in 10-CNS / Bov, indicating that the catalyst crystallization is good.

[0026] Figure 1 (b) is the FT-IR spectrum of the material. It can be seen that the prepared 10-CNS / Bov composite material has the typical characteristic peaks of both CNS and Bov. At the same time, the peak at 1570 cm-1 can be observed in both CNS and 10-CNS / Bov catalysts. -1This indicates that the carboxyl group of CNS and the hydroxyl group of Bov play a key role in enhancing the synergistic effect.

[0027] Example 2: Preparation of 5-CNS / Bov

[0028] This example is basically the same as Example 1, except that the amount of CNS added is changed to 0.01 g. 0.01 g CNS and 0.2 g Bov are weighed and placed in 50 mL methanol, ultrasonicated for 30 min, and magnetically stirred for 24 h. After the stirring is completed, it is washed with water and dried, and the obtained product is recorded as 5-CNS / Bov.

[0029] The XRD spectra of 5-CNS / Bov and 10-CNS / Bov prepared in this example are almost the same, and only the diffraction peak increases due to the reduction of the amount of CNS added. There is no significant difference in the FT-IR spectra of 5-CNS / Bov and 10-CNS / Bov.

[0030] Example 3: Preparation of 15-CNS / Bov

[0031] This example is basically the same as Example 1, except that the amount of CNS added is changed to 0.03 g. 0.03 g CNS and 0.2 g Bov are weighed and placed in 50 mL methanol, ultrasonicated for 30 min, and magnetically stirred for 24 h. After the stirring is completed, it is washed with water and dried, and the obtained product is recorded as 15-CNS / Bov.

[0032] The XRD spectra of 15-CNS / Bov and 10-CNS / Bov prepared in this example are almost the same, and the diffraction peaks thereof decrease due to the increase in the amount of CNS added. There is no significant difference in the FT-IR spectra of 15-CNS / Bov and 10-CNS / Bov.

[0033] Example 4: Application of CNS / Bov composite material for sterilization under visible light.

[0034] 20 mg of the sample was dispersed and inoculated into the bacterial culture, placed in a quartz reactor, and the photocatalytic disinfection experiment was carried out using a 500W xenon lamp equipped with a UV cutoff filter (λ≥420nm). Before irradiation, the mixture was stirred continuously for 0.5h in the dark to ensure that the solution was in a uniformly dispersed state. Aliquots of the samples were collected at regular intervals, diluted continuously with PBS, and then 100μl of the diluted samples were evenly dispersed on LB broth plates. Afterwards, all plates were incubated at 37°C for 24 hours to determine the number of viable cells.

[0035] Figure 2(a) is the photocatalytic bactericidal effect of the material under visible light. It can be seen that enhanced photocatalytic bactericidal activity of E. coli K-12 was observed in all CNS / Bov composite materials. Among them, 10-CNS / Bov has the best photocatalytic effect. Under visible light irradiation, 5.3 log 10 (cfu·mL -1 ) of Escherichia coli K-12, while for 5-CNS / Bov and 15-CNS / Bov, the bactericidal efficiencies at 2 h were 49% and 62%, respectively.

[0036] Comparative Example 1: Application of visible light sterilization of CNS

[0037] For comparative example 1, only the CNS synthesized in Example 1 was used as a catalyst for photocatalytic sterilization. Under the same conditions as in Example 4, the sterilization rate of CNS was only 13% at 2 h. It can be seen that under the same conditions, all CNS / Bov had better sterilization effects than CNS.

[0038] Figure 1 As can be seen in (a), compared with CN, the intensity of the (002) diffraction peak in the XRD of CNS is reduced, and the (100) peak completely disappears, indicating that CN is successfully exfoliated after acid treatment. Figure 1 As can be seen in (b), the stretching vibration mode of the CNS sample is weakened compared with that of CN, which also indicates that CN is successfully exfoliated.

[0039] Comparative Example 2: Application of Bov sterilization under visible light

[0040] For comparative example 2, only the Bov synthesized in example 1 was used as a catalyst for photocatalytic sterilization. Under the same conditions as in example 2, the sterilization rate of Bov was only 37% at 2h, which shows that under the same conditions, all CNS / Bov had better sterilization effects than Bov.

[0041] Figure 1 As can be seen in (a), all diffraction peaks in the XRD of the prepared Bov are well indexed with the cubic phase of Bov (PDF#47-1057), and no impurity peaks are found, indicating that the obtained product has high purity.

[0042] For Bov, FT-IR see Figure 1 (b) at 528 cm -1 and 588cm -1 There are two absorption bands nearby, corresponding to the vibration of Bi-O bonds. -1 The peak observed at is unique to the stretching vibration of the hydroxyl group.

[0043] Experimental Example 5: Application of CNS / Bov composite materials in photothermal sterilization under near-infrared light

[0044] Same as Example 4, only the ultraviolet cut-off filter is changed from λ≥420nm to λ≥700nm.

[0045] Figure 2 (b) is the photothermal sterilization effect of the material under near-infrared light. It can be seen that enhanced photocatalytic E. coli K-12 sterilization activity was observed in all CNS / Bov composite materials. Under near-infrared light irradiation, 4.2 log 10 (cfu·mL -1 ) of E. coli K-12, while for 5-CNS / Bov and 15-CNS / Bov, the sterilization efficiency at 3h was 60% and 65%, respectively. Unlike visible light, under near-infrared light, the surface temperature of the material will rise, and the temperature of 10-CNS / Bov material rises to 67.1℃, showing the thermal sterilization performance of the material, while under visible light irradiation, the temperature of 10-CNS / Bov material only remains at 25℃ and does not rise.

[0046] Comparative Example 3: Application of photothermal sterilization of CNS under near-infrared light

[0047] For comparative example 3, only the CNS synthesized in Example 1 was used as a catalyst for photothermal sterilization. Under the same conditions as in Example 5, the sterilization rate of CNS was only 23% at 2h. It can be seen that under the same conditions, all CNS / Bov had better sterilization effects than CNS.

[0048] Comparative Example 4: Application of Bov’s photothermal sterilization under near-infrared light

[0049] For comparative example 6, only Bov synthesized in example 1 was used as a catalyst for photothermal sterilization. Under the same conditions as in example 5, the sterilization rate of Bov was only 46% at 2h. It can be seen that under the same conditions, all CNS / Bov had better sterilization effects than Bov.

Claims

1. g-C3N4 / BiO 2-x The method for preparing a nanosheet composite material is characterized in that: The specific steps are as follows: Step 1, dispersing g-C3N4 in concentrated sulfuric acid, and washing with water after stirring to obtain g-C3N4 nanosheets; Step 2: adding sodium bismuthate to a sodium hydroxide solution, stirring thoroughly, and then performing a solvent thermal reaction at 160-200°C. After the reaction is completed, washing with water and drying are performed to obtain BiO 2-x Nanosheets; Step 3: Stirring the g-C3N4 nanosheets and BiO 2-x Nanosheets were added to methanol, and g-C3N4 nanosheets and BiO 2-x The mass ratio of nanosheets was 1-3:20, ultrasonic stirring, water washing, and drying to obtain g-C3N4 / BiO 2-x Nanocomposite materials.

2. The preparation method according to claim 1, characterized in that: In step 1, the ratio of g-C3N4 to concentrated sulfuric acid is 0.2:25, g:mL.

3. The preparation method according to claim 1, characterized in that: In step 1, the concentration of concentrated sulfuric acid is 98%.

4. The preparation method according to claim 1, characterized in that: In step 2, the solvent thermal reaction temperature is 180° C. and the reaction time is 12 h.

5. The preparation method according to claim 1, characterized in that In step 2, the concentration of the NaOH solution is 1M.

6. The preparation method according to claim 1, characterized in that: In step 3, g-C3N4 nanosheets and BiO 2-x The mass ratio of the nanosheets was 1:

10.

7. g-C3N4 / BiO prepared by the preparation method according to any one of claims 1 to 6. 2-x Nanosheet composites.

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