Preparation method and application of a double-z type ternary heterojunction photocatalyst

Abstract

The application discloses a preparation method of a double-Z type ternary heterojunction photocatalyst and application thereof, and belongs to the technical field of photocatalytic antibacterial technology.The BiVO4 precursor is prepared by using a natural traditional Chinese medicine honeysuckle water extract assisted hydrothermal method, and a BiVO4 / g-C3N4 / Ag3PO4 ternary heterojunction structure is further synthesized by using a co-precipitation method.The chemical composition and microstructure are characterized and analyzed, and the photocatalytic bacteriostatic mechanism is studied by taking E.coli and S.aureus as models.The application has important reference value for research and development of a novel photocatalytic disinfection material, and plays an important role in environmental protection.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic antibacterial technology, and more specifically to a method for preparing a double Z-type ternary heterojunction photocatalyst and its application. Background Technology

[0002] The principle behind photocatalysis is as follows: A semiconductor consists of a low-energy valence band (VB) and a high-energy conduction band (CB), separated by a band gap. When a photon with energy greater than the band gap irradiates the photocatalytic material, electrons in the valence band are excited and transition to the conduction band, thereby creating photogenerated holes (h) in both the valence and conduction bands. + ) and photogenerated electrons (e - Excited-state photogenerated electrons and holes can recombine, generating heat. When a suitable trapping agent, surface defects, or other factors are present in the semiconductor, electrons and holes no longer recombine but migrate to the semiconductor surface under the influence of an electric field. Holes then react with H₂O / OH adsorbed on the semiconductor surface. - The reaction generates hydroxyl radicals (·OH), while electrons react with O2 to generate superoxide radicals (·O2). - ), ·OH and ·OOH free radicals, etc. These free radicals, electrons and holes can undergo redox reactions with viruses, bacteria, inorganic and organic compounds adsorbed on the semiconductor surface.

[0003] In short, photocatalytic reactions on semiconductors involve five main steps: (1) light absorption by the semiconductor; (2) formation of photogenerated electron-hole pairs; (3) migration and recombination of photogenerated electron-hole pairs; (4) adsorption of reactants and desorption of products; and (5) redox reactions occurring on the semiconductor surface. Therefore, photocatalytic activity largely depends on the synergistic effect of the following three factors: light absorption, the number of active sites, and the separation of photogenerated electron-hole pairs.

[0004] Photocatalytic antibacterial activity has been applied in many fields due to its advantages. The mechanism of photocatalytic antibacterial activity mainly involves the destruction of bacterial cell walls by reactive oxygen species (ROS), leading to bacterial inactivation and ultimately death. When a photocatalyst is irradiated with visible light, photogenerated electrons (electrons) are generated. - The electron will acquire energy and be excited to jump from the valence band (VB) of the semiconductor to the conduction band (CB), leaving positively charged holes (h) on the VB. + e - It can come into contact with oxygen molecules to form superoxide radicals (·O2), which have strong oxidizing power. - ), and h + It can form hydroxyl radicals (·OH) with water molecules. ·O2 -Both hydroxyl radicals (·OH) and reactive oxygen species (ROS) can react with organic matter within microorganisms, disrupting their internal structure and inhibiting reproduction. Semiconductor conduction bands and valence electrons react with reactive oxygen species (ROS), which typically include hydroxyl radicals, superoxide radicals, and hydrogen peroxide. These reactive species damage bacterial DNA and proteins, leading to bacterial death and thus exerting an antibacterial effect. Photocatalysis is a promising green technology for antibacterial applications.

[0005] In summary, how to provide a photocatalyst with antibacterial properties is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing a dual-Z type ternary heterojunction photocatalyst and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a dual-Z-type ternary heterojunction photocatalyst includes the following steps:

[0009] (1) Preparation of honeysuckle water extract

[0010] (2) Biosynthesis of BiVO4

[0011] Bi(NO3)3·5H2O and NH4VO3 were dissolved in honeysuckle water extract, respectively. After mixing, the mixture was magnetically stirred and heated. The precipitate was collected by centrifugation, dried, and then annealed in a muffle furnace at 500℃ for 4 hours.

[0012] (3) Preparation of g-C3N4

[0013] Melamine is deaminated in a muffle furnace, then added to ethanol for ultrasonic peeling, and finally dried.

[0014] (4) Preparation of BiVO4 / g-C3N4

[0015] BiVO4 and g-C3N4 were placed in an ethanol solution and subjected to ultrasonic and magnetic stirring in sequence. After drying, they were heat-treated in a muffle furnace at 400℃ for 4 hours to obtain BiVO4 / g-C3N4, wherein the mass ratio of BiVO4 to g-C3N4 was (6~9):(1~4).

[0016] (5) Preparation of BiVO4 / g-C3N4 / Ag3PO4

[0017] BiVO4 / g-C3N4 was dispersed in ethanol, and then AgNO3 solution and Na2HPO4 solution were added sequentially. After mixing, the mixture was subjected to ultrasonic treatment and magnetic stirring, and then dried.

[0018] Beneficial effects achieved: Bismuth vanadate (BiVO4), as an environmentally friendly, stable, and non-toxic inorganic yellow pigment, has unique physicochemical properties and is often used in fields such as photocatalytic degradation of organic matter, photocatalytic water splitting to produce hydrogen, and photoantibacterial agents.

[0019] Furthermore, in step (1), the honeysuckle water extract is prepared by ultrasonic extraction.

[0020] Furthermore, the specific operation of step (2) is as follows:

[0021] (21) Dissolve Bi(NO3)3·5H2O and NH4VO3 in honeysuckle water extract respectively;

[0022] (22) After mixing the two solutions, heat them on a magnetic stirrer and then cool them.

[0023] (23) Centrifuge, collect the precipitate, and wash with ethanol and deionized water;

[0024] (24) After drying, the product was annealed in a muffle furnace at 500°C for 4 hours to obtain a yellow powder, which was named BiVO4.

[0025] Furthermore,

[0026] In step (21), the molar ratio of Bi(NO3)3·5H2O and NH4VO3 is 1:1;

[0027] In step (22), the heating is performed at 100°C for 1 hour;

[0028] In step (23), the drying process involves drying under vacuum at 60°C for 8 hours.

[0029] Furthermore, the specific operation of step (3) is as follows:

[0030] (31) Melamine was heated in a muffle furnace at 550℃ at a rate of 3℃·min -1 The heating rate was directly applied for 4 hours, followed by cooling. Under the same conditions, a second heat treatment was performed for further ammonia removal for 4 hours, followed by cooling.

[0031] (32) Collect the product and grind it into powder;

[0032] (33) Add the powder to the ethanol solution, sonicate the solution for 8 hours, centrifuge and filter the product, wash with deionized water and anhydrous ethanol, and vacuum filter.

[0033] (34) The collected sample was dried to obtain a light yellow solid sample, which was named g-C3N4.

[0034] Furthermore,

[0035] In step (33), the centrifugal filtration is performed at 10000 r·min. -1 Centrifuge and filter for 5 minutes;

[0036] In step (34), the drying process involves drying at 60°C for 8 hours.

[0037] Furthermore, the specific operation of step (5) is as follows:

[0038] (51) BiVO4 / g-C3N4 was dispersed in ethanol, and then AgNO3 solution was added and stirred continuously to dissolve it; wherein, the mass-volume ratio of BiVO4 / g-C3N4 to AgNO3 solution was 9:1 g / ml;

[0039] (52) Add Na2HPO4 solution dropwise, wherein the volume ratio of Na2HPO4 solution to AgNO3 solution is 1:1;

[0040] (53) Sonicate the mixed solution in the dark for 2 hours;

[0041] (54) Stir magnetically for 8 hours;

[0042] (55) The product was centrifuged and filtered, washed with deionized water and anhydrous ethanol, and dried to finally obtain the BiVO4 / g-C3N4 / Ag3PO4 catalyst.

[0043] Furthermore,

[0044] In step (41), the mass concentration of the AgNO3 solution is 0.45 mol·L⁻¹. -1 ;

[0045] In step (42), the mass concentration of the Na2HPO4 solution is 0.15 mol·L⁻¹. -1 ;

[0046] In step (45), the centrifugal filtration is performed at 10000 r·min. -1 Centrifuge and filter for 5 minutes;

[0047] In step (45), drying is performed at 60°C for 12 hours.

[0048] The application of the photocatalyst prepared by the above method in the preparation of photocatalytic disinfection materials.

[0049] Furthermore, the photocatalyst can inhibit Escherichia coli and Staphylococcus aureus.

[0050] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by this invention are as follows: This invention utilizes the aqueous extract of the natural Chinese herb honeysuckle to assist in the hydrothermal method to prepare the BiVO4 precursor, and further employs a co-precipitation method to synthesize the BiVO4 / g-C3N4 / Ag3PO4 ternary heterostructure. Its chemical composition and microstructure were characterized and analyzed, and its photocatalytic antibacterial mechanism was studied using Escherichia coli and Staphylococcus aureus as models. This invention has important reference value for the development of novel photocatalytic disinfection materials and also plays an important role in environmental protection. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0052] Figure 1 The XRD diffraction patterns of BiVO4 and BiVO4 / g-C3N4 and BiVO4 / g-C3N4 / Ag3PO4 samples with different doping ratios in Experiment 1 of this invention are shown below.

[0053] Figure 2 The following are the FT-IR spectra of different BiVO4 / g-C3N4 / Ag3PO4 samples in Experiment 2 of this invention;

[0054] Figure 3 The UV-Vis diffuse reflectance absorption spectra (A) and band gap diagram (B) of different BiVO4 / g-C3N4 / Ag3PO4 samples in Experiment 3 of this invention are shown.

[0055] Figure 4 The above are XPS spectra of the BiVO4 / g-C3N4 / Ag3PO4 sample in Experiment 4 of this invention; where A is the full XPS spectrum; B is Bi4f; C is V 2p; D is O1s; E is C1s; F is N1s; G is P 2p; and H is Ag 3d.

[0056] Figure 5 The results show the antibacterial performance of the photocatalyst on E. coli (A) and S. aureus (B) in Experiment 5 of this invention;

[0057] Figure 6 The image shows the antibacterial activity of the BiVO4 / g-C3N4 / Ag3PO4 sample against E. coli and S. aureus after different light exposure times in Experiment 6 of this invention.

[0058] Figure 7The results of the photocatalytic antibacterial cycle experiment of the BiVO4 / g-C3N4 / Ag3PO4 (10%-BGA) sample in Experiment 8 of this invention are shown in (A) and the XRD patterns before and after antibacterial inhibition are shown in (B).

[0059] Figure 8 The results of the photocatalytic antibacterial activity group capture experiment of the BiVO4 / g-C3N4 / Ag3PO4 sample in Experiment 9 of this invention;

[0060] Figure 9 This describes the photocatalytic antibacterial mechanism of the BiVO4 / g-C3N4 / Ag3PO4 nanocomposite material under visible light in Experiment 9 of this invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] The materials required for this invention are conventional experimental materials, purchased from commercially available channels; the experimental methods not mentioned are conventional experimental methods, and will not be described in detail here.

[0063] Example 1

[0064] (1) Preparation of honeysuckle water extract

[0065] Rinse the honeysuckle with distilled water to remove particulate matter or impurities. Then, soak 20g of honeysuckle in 1000mL of deionized water for 3 hours and extract ultrasonically for 1.5 hours (60℃). Cool the extract to 25℃ and filter three times with qualitative filter paper (medium speed) to obtain the honeysuckle water extract. Store at 4℃ for later use.

[0066] (2) Biosynthesis of BiVO4

[0067] 1 mmol (0.485 g) of Bi(NO3)3·5H2O and 1 mmol (0.117 g) of NH4VO3 were added separately to 50 mL of honeysuckle aqueous extract. The mixture was heated on a magnetic stirrer (40 rpm, 100 °C, 1 h) to ensure homogeneity, and then allowed to cool naturally to 25 °C. The precipitate was collected by centrifugation, washed several times with ethanol and deionized water, and dried under vacuum at 60 °C for 8 h. Annealing was then performed in a muffle furnace at 500 °C for 4 h to obtain a yellow powder, named BiVO4.

[0068] (3) Preparation of g-C3N4

[0069] Melamine was heated in a muffle furnace at 550°C at a rate of 3°C / min. -1 The product was directly heated at a rising rate of 4 hours, cooled to 25°C, and then subjected to a second heat treatment under the same conditions for further deamination for 4 hours. After cooling to 25°C, the product was collected and ground into a yellow powder. 1 g of the powder was added to 10 ml of 75% ethanol solution, and the solution was ultrasonically exfoliated for 8 hours. The product was then centrifuged and filtered for 5 minutes (10000 r·min). -1 The sample was washed several times with deionized water and anhydrous ethanol, followed by vacuum filtration. Finally, the collected sample was placed in a drying oven at 60°C for 8 hours to dry, yielding a light yellow solid sample, which was named g-C3N4.

[0070] (4) Preparation of BiVO4 / g-C3N4 photocatalyst

[0071] Different amounts of BiVO4 and g-C3N4 were placed in an ethanol solution. The mixture was sonicated for 2 hours, magnetically stirred for 8 hours, and the product was collected and dried at 60°C for 12 hours. The resulting product was then ground into a fine solid powder using a mortar and anvil. The fine solid powder was then heat-treated in a muffle furnace at 400°C for 4 hours to obtain BiVO4 / g-C3N4. The materials were designated as BG-10% (9 g BiVO4, 1 g g-C3N4), BG-20% (8 g BiVO4, 2 g g-C3N4), and BG-40% (6 g BiVO4, 4 g g-C3N4).

[0072] (5) Preparation of BiVO4 / g-C3N4 / Ag3PO4

[0073] 0.9 g of BG-20% was dispersed in 50 ml of ethanol, and 0.1 ml of 0.45 mol·L⁻¹ solution was added. -1 Dissolve the AgNO3 solution by stirring constantly. Then, add 0.1 mL of 0.15 mol·L⁻¹ solution dropwise. -1 The Na₂HPO₄ solution was mixed and sonicated in the dark for 2 hours. The mixture was then magnetically stirred for 8 hours, and the product was centrifuged and filtered for 5 minutes (10000 rpm). -1 The catalyst was washed several times with deionized water and anhydrous ethanol, and then dried in air at 60°C for 12 hours to finally obtain the BiVO4 / g-C3N4 / Ag3PO4 catalyst 10%-BGA.

[0074] Based on the mass ratio of Ag3PO4 to BiVO4 / g-C3N4, they were labeled as 5%-BGA (0.95 g BG-20%, 0.05 mL AgNO3 solution, 0.05 mL Na2HPO4 solution), 10%-BGA, and 15%-BGA (0.85 g BG-20%, 0.15 mL AgNO3 solution, 0.15 mL Na2HPO4 solution).

[0075] Experiment 1

[0076] The XRD diffraction patterns of BiVO4 and BiVO4 / g-C3N4 and BiVO4 / g-C3N4 / Ag3PO4 samples with different doping ratios are shown below. Figure 1 As shown.

[0077] The XRD patterns of samples BiVO4, g-C3N4, Ag3PO4 and their corresponding heterojunctions are shown below. Figure 1 As shown, multiple diffraction peaks at 18.6, 18.9, 28.5, 28.8, 28.9, 30.5, 34.4, 35.2, 39.7, 40, 42.4, 46.7, 53.2, 53.3, and 58.2° of the BiVO4 sample correspond to the {110}, {011}, {-130}, {-121}, {121}, {040}, {200}, {002}, {211}, {-112}, {051}, {240}, {042}, {-161}, {161}, {-321}, and {321} planes, respectively, which are basically consistent with the BiVO4 standard diffraction card (JCPDS No. 14-0688). However, the intensity of each diffraction peak of the BiVO4 sample is lower than that of the standard spectrum. According to the Scherrer formula (1), the crystal size of the BiVO4 sample is about 117.6 nm, which is larger than the 29.7 nm of the BiVO4 standard diffraction card.

[0078]

[0079] Where D is the crystal size, λ is 0.15418 nm, K = 0.89, β = (FWHM / 180°) × 3.14, 2θ = 28.622, and FWHM is the width of the (121) half-peak diffraction peak.

[0080] Furthermore, the {121} interplanar spacing of BiVO4 increased, and diffuse peaks of carbon microcrystals were observed in the range of 20°–30°, indicating that some carbon was doped into BiVO4. Larger carbon atoms (0.077 nm) replaced smaller oxygen atoms (0.074 nm), thus inhibiting BiVO4 grain growth and reducing the crystallinity of the sample. For the g-C3N4 sample, the diffraction peaks at 12.9° and 27.6° pointed to the {100} and {002} planes of g-C3N4, indicating that the prepared BiVO4 / g-C3N4 composite material could effectively detect both g-C3N4 and BiVO4 phases. With increasing g-C3N4 doping ratio, the intensity of the diffraction peaks belonging to g-C3N4 increased. The characteristic peaks at 20.8, 29.6, 33.2, 36.5, 47.7, 52.6, 55.0, and 57.2 ppm of the Ag3PO4 sample correspond to the {110}, {200}, {210}, {211}, {220}, {222}, {320}, and {321} crystal planes, respectively, which are basically consistent with the Ag3PO4 standard diffraction card (JCPDS No. 06-0505). For the BiVO4 / g-C3N4 / Ag3PO4 composite material, when the Ag3PO4 doping rate is greater than 5%, the three phases of BiVO4, g-C3N4, and Ag3PO4 can be detected well, and the intensity of the diffraction peaks belonging to Ag3PO4 increases with the increase of the Ag3PO4 doping ratio.

[0081] Experiment 2

[0082] FT-IR spectra of different BiVO4 / g-C3N4 / Ag3PO4 samples are shown below Figure 2 As shown.

[0083] Depend on Figure 2 It can be seen that the BiVO4 sample at 750 cm -1 There is an absorption peak at 810 cm⁻¹, which is due to the asymmetric stretching vibration of VO₄. The intensity of this absorption peak decreases with different doping ratios of g-C₃N₄ and Ag₃PO₄. For the g-C₃N₄ sample, the absorption peak intensity is 810 cm⁻¹. -1 The peak at [location] is attributed to the characteristic peaks of the triazine structure. Additionally, the peaks at 1200–1700 cm⁻¹... -1 The peak values ​​within the range are attributed to the stretching vibrations of the CN heterocycle, at 3000 cm⁻¹. -1 and 3600cm -1 The broadband bands between them are attributed to secondary and primary amines, respectively. After successful recombination with g-C3N4, these two characteristic peaks are very significant in the BiVO4 / g-C3N4 heterojunction. Ag3PO4 at 3357 cm⁻¹... -1 and 1653cm -1The broad absorption peaks at 541 and 951 cm⁻¹ correspond to the OH stretching vibration of water. -1 The two characteristic peaks at that location correspond to PO4. 3- Stretching vibrations of PO and P=O in the functional groups. After Ag3PO4 composite, the characteristic peaks of BiVO4 and g-C3N4 in the BiVO4 / g-C3N4 / Ag3PO4 heterojunction are retained, but both are weakened, while the characteristic peak of Ag3PO4 is strengthened.

[0084] Experiment 3

[0085] UV-Vis diffuse reflectance absorption spectra and band gaps of different BiVO4 / g-C3N4 / Ag3PO4 samples are shown in the figure. Figure 3 As shown.

[0086] Depend on Figure 3 As can be seen, the optical absorption properties of the sample were studied using ultraviolet-visible spectroscopy. For example... Figure 3 As shown in Figure A, the UV-Vis diffuse reflectance spectra (UV-Vis DRS) of all samples exhibit significant absorption. The light absorption thresholds of g-C3N4 and Ag3PO4 in the ultraviolet region are between 300 and 400 nm, with band gaps between 2.41 eV and 2.75 eV. When combined with BiVO4 at different ratios, the light absorption of the samples exhibits a redshift, with the threshold shifting to 500 nm, while the band gap decreases to 2.42 eV, showing a correlation with the doping ratio. These results indicate that the combination of BiVO4 with g-C3N4 and Ag3PO4 significantly improves photoadsorption performance and narrows the band gap, which is key to enhancing catalytic activity.

[0087] according to Figure 3 B calculated the band gaps Eg of BiVO4, g-C3N4, and Ag3PO4 using extrapolation to be 2.42 eV, 2.75 eV, and 2.43 eV, respectively. From the literature, the electronegativity of BiVO4, g-C3N4, and Ag3PO4 are known to be 6.04 eV, 4.72 eV, and 5.96 eV, respectively. Then, according to the formula E... VB =X - Ee + 0.5Eg and E CB =E VB -Eg calculations yielded the E of BiVO4 CB and E VB The ECB and EVB values ​​for g-C3N4 were 0.33 eV and 2.75 eV, respectively, while those for Ag3PO4 were -1.16 eV and 1.59 eV. The ECB and EVB values ​​for Ag3PO4 were 0.24 eV and 2.67 eV, respectively.

[0088] Experiment 4

[0089] XPS spectra of the BiVO4 / g-C3N4 / Ag3PO4 sample (10%-BGA) are as follows: Figure 4 As shown.

[0090] Depend on Figure 4 The chemical composition of the BiVO4 / g-C3N4 / Ag3PO4 nanocomposite was investigated using XPS. The measured spectra of BiVO4 / g-C3N4 / Ag3PO4 revealed the presence of Bi, V, O, C, N, P, and Ag elements in the composite material, confirming its uniform distribution. Furthermore, high-resolution XPS spectra were obtained to further understand the chemical states of the elements in the composite material. (High-resolution Bi 4f XPS spectrum) Figure 4 The four fitting peaks in B) are located at 159.1 eV, 160.2 eV, 163.8 eV, and 165.1 eV, respectively, and are attributed to Bi 4f. 7 / 2 and Bi 4f 5 / 2 The horizontal binding energy indicates that Bi is present in the BiVO4 / g-C3N4 / Ag3PO4 composite material as Bi. 3+ The state exists. Two characteristic peaks are observed at 514.4 eV and 521.9 eV ( Figure 4 C) belong to V 2p respectively 1 / 2 and V 2p 2 / 3 The signal indicates that V is present in the composite material as V2. 5+ The state exists. Figure 4 The O1s asymmetric photoelectron peak observed in D is caused by lattice oxygen from surface-adsorbed oxygen (532.9 eV), VO (532.9 eV), and PO (529.9 eV). Additionally, the peak at 284.8 eV... Figure 4 The E peak belongs to the CV and CC bonds of the external carbon source, while the peaks at 286.3 eV and 284.8 eV are attributed to the CO group and the NC=N group in g-C3N4. (High-resolution N1s XPS spectrum) Figure 4 The three fitted peaks of F), centered around 398.2 eV, 399.2 eV, and 400.9 eV, can be attributed to the triazine ring (CN=C), tertiary nitrogen group (N-(C)3), and hydrogen-containing amino functional group (NH) in g-C3N4, respectively. The characteristic peak at 133.3 eV (…) Figure 4 G) belongs to P 2p The characteristic signal indicates that P element is present in the composite material as P. 5+ It exists in the form of Ag. The high-resolution XPS spectrum of Ag can be separated into two peaks at 367.9 and 373.9 eV, which is attributed to the Ag 3d of metallic silver. 5 / 2 and Ag 3d 3 / 2 The characteristic peaks indicate that Ag is present in the composite material. + It exists in the form of.

[0091] Experiment 5

[0092] The antibacterial properties of photocatalysts against E. coli and S. aureus were as follows: Figure 5 As shown.

[0093] Survival curves of BiVO4 / g-C3N4 / Ag3PO4 against E. coli and S. aureus are as follows: Figure 5 As shown, the antibacterial rate of each prepared sample decreased significantly with prolonged exposure time. In the blank control experiment (no light), cell inactivation was less than 0.2 log within 50 min, indicating that the antibacterial effect of the samples was relatively small under light-protected conditions. The figure shows that pure BiVO4 and g-C3N4 have low bactericidal activity against E. coli and S. aureus. The bactericidal activity is improved after they are combined to form a heterostructure, and the antibacterial effect is only superior to that of pure Ag3PO4 when the combination rate is greater than 10%. This depends on the Ag content in the Ag3PO4 sample. + It exhibits good antibacterial ability. However, excessive complexation with g-C3N4 is detrimental to photocatalytic sterilization because g-C3N4 has an Eg value of 2.75, and its utilization efficiency for visible light is lower than that of BiVO4. When a ternary heterojunction BiVO4 / g-C3N4 / Ag3PO4 is formed, the antibacterial effect of the sample is further significantly enhanced, but excessive Ag3PO4 doping will cause photochemical corrosion, which will reduce the catalytic effect. 10%-BGA has the best photocatalytic antibacterial effect, and can kill almost all E. coli (6.9 log inactivation) after 50 min of visible light irradiation. Figure 5 A). Meanwhile, 10%-BGA also showed the highest inactivation efficiency against *S. aureus*, inactivating approximately 4.6 log(A) within a 50-minute reaction time. Figure 5 B), but the inactivation efficiency of 10%-BGA on S. aureus was lower than that on E. coli, which may be due to the relatively thick cell wall of S. aureus, which prevents the active free radicals generated by photocatalysis from damaging it.

[0094] Experiment 6

[0095] The antibacterial effect of the BiVO4 / g-C3N4 / Ag3PO4 (10%-BGA) composite photocatalyst on E. coli and S. aureus was determined using the plate count method. The results are as follows: Figure 6 As shown.

[0096] Figure 6 The results were consistent with those of the photocatalytic quantitative antibacterial experiment (Experiment 5).

[0097] Experiment 7

[0098] The MIC and MBC values ​​of the 10%-BGA sample with the best antibacterial effect were determined, and the results are shown in Tables 1 and 2.

[0099] Table 1 MIC Results

[0100]

[0101] Note: + indicates bacterial growth, - indicates sterile growth.

[0102] Table 2 MBC Results

[0103]

[0104] Note: + indicates bacterial growth, - indicates sterile growth.

[0105] The MICs of 10%-BGA against E. coli and S. aureus were 0.6 mg / mL, respectively. -1 and 0.8 mg·mL -1 The MBC results for E. coli and S. aureus were 0.8 mg·mL, respectively. -1 and 1 mg·mL -1 In conclusion, under light conditions, 10%-BGA exhibits antibacterial activity against both types of bacteria.

[0106] Experiment 8

[0107] The photocatalytic antibacterial cycle stability of the 10%-BGA sample was verified using E. coli (the material was exposed to light conditions 5 times).

[0108] The XRD patterns of 10%-BGA showed no significant changes before and after inhibition. Figure 7 B) indicates that the 10%-BGA material still maintains high purity and crystal form after the reaction, indicating that the 10%-BGA material has high resistance to photocorrosion.

[0109] After four cycles of experiments, the antibacterial activity against E. coli remained at 6.1 log inactivation ( Figure 7 A) The data shows that 10%-BGA has good cycle stability, which is of great significance for the practical application of 10%-BGA.

[0110] Experiment 9

[0111] To investigate the active components of photocatalysis, this experiment conducted a free radical scavenging experiment on the antibacterial activity of E. coli (the following substances were added to the material to capture the active groups of this reaction). Isopropanol (IPA), p-benzoquinone (BQ), and disodium ethylenediaminetetraacetate (EDTA-2Na) were used as ·OH and ·O2, respectively. - h+ A scavenger of active groups. Results are as follows: Figure 8 As shown.

[0112] Depend on Figure 8 It can be seen that the addition of EDTA-2Na has the greatest inhibitory effect on catalysis (3.5 log inhibiting bacteria), indicating that h + It is the main active substance in catalysis. Meanwhile, the catalytic performance also decreased significantly after the addition of BQ (3.2 log of antibacterial activity), indicating that ·O2 - It is also a major free radical involved in the catalytic reaction. IPA has a relatively small effect on the reaction (1.85 log inhibiting bacteria), indicating that ·OH plays a secondary catalytic role.

[0113] In summary, the photocatalytic mechanism of the BiVO4 / g-C3N4 / Ag3PO4 (10%-BGA) sample can be inferred, such as... Figure 9 As shown, the strong electrostatic interaction between BiVO4, Ag3PO4, and layered g-C3N4 extends, forming an internal electric field at the contact interface. Under visible light irradiation, both BiVO4 and Ag3PO4 can be excited, generating electrons on CB and VB, respectively. - and h + Subsequently, e- produced from Ag3PO4 and BiVO4 - It can be transferred to the VB of g-C3N4 and recombine with the holes there to form an interfacial Z-shaped heterostructure. This allows e - The CB is retained in g-C3N4, thanks to the CB potential of g-C3N4 (-1.16 eV relative to NHE, which is more negative than E0) (O2 / O2 - ·=-0.33eV NHE), therefore g-C3N4 reacts with O2 to generate more O2. - This effectively suppressed e. - and h + The reduction of recombination enhances the photocatalytic performance of the material. However, the CB potentials of BiVO4 and Ag3PO4 (0.33 and 0.24 eV relative to NHE, respectively) are more positive than E0 (O2 / O2). - Since the oxygen content is -0.33 eV (NHE), no O2 was produced. - However, in the VB of BiVO4 and Ag3PO4, the positively charged h + It can directly oxidize bacteria or react with H2O to produce ·OH and O2. - It also promotes further oxidation. It is easy to see that the formation of the Z-shaped heterostructure effectively improves the photocatalytic performance of the material.

[0114] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a double-Z-type ternary heterojunction photocatalyst, characterized in that, Includes the following steps: (1) Preparation of honeysuckle water extract (2) Biosynthesis of BiVO4 Bi(NO3)3•5H2O and NH4VO3 were dissolved in honeysuckle water extract, respectively. After mixing, the mixture was magnetically stirred and heated. The precipitate was collected by centrifugation, dried, and then annealed in a muffle furnace at 500 ℃ for 4 h. (3) Preparation of g-C3N4 Melamine is deaminated in a muffle furnace, then added to ethanol for ultrasonic peeling, and finally dried. (4) Preparation of BiVO4 / g-C3N4 BiVO4 and g-C3N4 were placed in an ethanol solution, and then subjected to ultrasonic and magnetic stirring in sequence. After drying, they were heat-treated in a muffle furnace at 400℃ for 4 hours to obtain BiVO4 / g-C3N4, wherein the mass ratio of BiVO4 to g-C3N4 was (6~9):(1~4). (5) Preparation of BiVO4 / g-C3N4 / Ag3PO4 BiVO4 / g-C3N4 was dispersed in ethanol, and then AgNO3 solution and Na2HPO4 solution were added sequentially. After mixing, the mixture was subjected to ultrasonic treatment and magnetic stirring, and then dried.

2. The preparation method according to claim 1, characterized in that, In step (1), the honeysuckle water extract is prepared by ultrasonic extraction.

3. The preparation method according to claim 1, characterized in that, The specific operation of step (2) is as follows: (21) Dissolve Bi(NO3)3•5H2O and NH4VO3 in honeysuckle water extract respectively; (22) After mixing the two solutions, heat them on a magnetic stirrer and then cool them. (23) Centrifuge, collect the precipitate, and wash with ethanol and deionized water; (24) After drying, the product was annealed in a muffle furnace at 500 °C for 4 h to obtain a yellow powder, which was named BiVO4.

4. The preparation method according to claim 3, characterized in that, In step (21), the molar ratio of Bi(NO3)3•5H2O and NH4VO3 is 1:1; In step (22), the heating is performed at 100 °C for 1 hour; In step (24), the drying process involves drying under vacuum at 60 °C for 8 h.

5. The preparation method according to claim 1, characterized in that, The specific operation of step (3) is as follows: (31) Melamine was heated in a muffle furnace at 550 °C at a rate of 3 °C·min. -1 The heating rate was directly applied for 4 hours, followed by cooling. Under the same conditions, a second heat treatment was applied for further ammonia removal for 4 hours, followed by cooling. (32) Collect the product and grind it into powder; (33) Add the powder to the ethanol solution, sonicate the solution for 8 h, centrifuge and filter the product, wash with deionized water and anhydrous ethanol, and vacuum filter. (34) After drying the collected sample, a light yellow solid sample was obtained and named g-C3N4.

6. The preparation method according to claim 5, characterized in that, In step (33), the centrifugal filtration is performed at 10000 r·min. -1 Centrifuge and filter for 5 min; In step (34), the drying process is carried out at 60 °C for 8 h.

7. The preparation method according to claim 1, characterized in that, The specific operation of step (5) is as follows: (51) BiVO4 / g-C3N4 was dispersed in ethanol, and then AgNO3 solution was added and stirred continuously to dissolve it; wherein, the mass-volume ratio of BiVO4 / g-C3N4 to AgNO3 solution was 9:1 g / mL; (52) Add Na2HPO4 solution dropwise, wherein the volume ratio of Na2HPO4 solution to AgNO3 solution is 1:1; (53) The mixed solution was sonicated in the dark for 2 h; (54) Magnetic stirring for 8 h; (55) The product was centrifuged and filtered, washed with deionized water and anhydrous ethanol, dried, and finally the BiVO4 / g-C3N4 / Ag3PO4 catalyst was obtained.

8. The preparation method according to claim 7, characterized in that, In step (51), the mass concentration of the AgNO3 solution is 0.45 mol·L⁻¹. -1 ; In step (52), the mass concentration of the Na2HPO4 solution is 0.15 mol·L⁻¹. -1 ; In step (55), the centrifugal filtration is performed at 10000 r·min. -1 Centrifuge and filter for 5 min; In step (55), drying is performed at 60 °C for 12 h.

9. The application of the photocatalyst prepared by any one of claims 1 to 8 in the preparation of photocatalytic disinfection materials.

10. The application as described in claim 9, characterized in that, The photocatalyst is used to inhibit Escherichia coli and Staphylococcus aureus.

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