A tea saponin-tannin co-regulated Zn / Co bimetallic MOF / sulfur-doped tea saponin carbon quantum composite photothermal antibacterial material and a preparation method thereof

Abstract

The present application utilizes the double-template effect of tea saponin carboxyl coordination and tannin phenolic hydroxyl pore-forming to construct a double-metal heterostructure, expand near-infrared light absorption and improve specific surface area; tea saponin combined with thiourea realizes in-situ sulfur doping to prepare carbon quantum dots, relies on sulfur defects to inhibit carrier recombination, and saves additional polyphenol raw materials; full hydrothermal in-situ grafting is adopted, carbon quantum dots and MOF are chemically bonded and not easy to fall off, visible light-near infrared synergistic photocatalysis and photothermal sterilization are realized. The process does not use high-toxicity organic solvents, the raw materials are taken from agricultural and forestry by-products, and the process is biodegradable, suitable for antibacterial dressings, acne-removing skin care, washing and conditioning additives and water sterilization. Tests show that the material has a 99.99% inhibition rate on Staphylococcus aureus, MRSA drug-resistant bacteria and Escherichia coli, the temperature is increased by more than 40 DEG C under near-infrared light for 10 minutes, and the excellent antibacterial activity is still maintained in the dark, and the comprehensive performance is better than that of single-metal tea saponin MOF material.

Description

Technical Field

[0001] This invention belongs to the field of biomass nanophotothermal antibacterial composite materials, and is particularly suitable for daily chemical antibacterial washing and care, skin repair dressings, and water purification. Specifically, it involves a complete set of green preparation processes for integrated antibacterial materials using tea saponin-tannin dual ligands to regulate bimetallic MOFs and in-situ loaded sulfur-doped tea saponin carbon quanta. Background Technology

[0002] Existing publicly available patents related to tea saponin MOFs (such as CN116407631A) have significant shortcomings: 1. They only use a single metal framework of ZIF-8 and Cu-BTC, lacking a bimetallic heterostructure, and can only absorb ultraviolet and weak visible light, lacking near-infrared response. Photogenerated electrons and holes recombine rapidly, resulting in low reactive oxygen species production. 2. The carbon quantum raw materials are all tea polyphenols, failing to fully utilize tea saponin, a byproduct of camellia oil, leading to high raw material costs. 3. Using only tea saponin as a single surfactant to regulate crystals results in limited improvement in material porosity and specific surface area, and carbon quantum particles are easily physically detached. 4. The material lacks photothermal effects, relying solely on photocatalytic sterilization, leading to extremely poor antibacterial effects in dark environments. 5. The synthesis process often uses methanol and ethanol organic solvents, resulting in significant wastewater pollution and hindering safe mass production in the daily chemical industry. Existing technologies do not disclose a synergistic regulation of bimetallic MOFs using tea saponin and tannin as dual templates, nor do they disclose an integrated hydrothermal synthesis route for preparing sulfur-doped carbon quantum particles using tea saponin alone, indicating significant potential for performance and process improvement. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of existing monometallic tea saponin MOFs, such as narrow light absorption, lack of near-infrared photothermal properties, high cost of carbon quantum raw materials, single antibacterial effect, and organic solvent pollution. It provides a sulfur-doped tea saponin carbon quantum composite photothermal antibacterial material supported by a Zn-Co bimetallic MOF with tea saponin-tannin co-regulation. It is synthesized in an all-aqueous phase in a green way, with dual response of visible light and near-infrared light, and broad-spectrum bactericidal effect through photothermal synergy. It is suitable for safe applications in multiple scenarios such as daily chemical, medical and agricultural fields.

[0004] The core technological innovation of this invention

[0005] (1) Synergistic regulation of bimetallic heteroframework by bibimonic ligands

[0006] The triterpenoid structure of tea saponins provides a large number of hydroxyl and carboxyl groups, which coordinate with Zn and Co metal ions to form nuclei; tannins and polyphenols fill the crystal channels, increasing the specific surface area of ​​the material; Zn and Co construct heterojunctions to narrow the band gap, extending the light absorption to the 780nm near-infrared region, and significantly improving the photocatalytic activity.

[0007] (2) In-situ sulfur-doped carbon quanta of tea saponin (without additional polyphenols)

[0008] Using tea saponins as the carbon source, thiourea is in situ doped to introduce sulfur defect energy levels, which capture photogenerated electrons and suppress electron-hole recombination; there is no need to purchase tea polyphenols, reducing raw material costs and realizing full utilization of camellia oil by-products.

[0009] (3) Full hydrothermal in-situ chemical bonding grafting process

[0010] The synthesis of MOFs involves simultaneous anchoring of carbon quanta, relying on intermolecular hydrogen bonds and coordination bonds to firmly bind them and prevent carbon quanta from falling off; no organic solvents such as methanol and acetone are added throughout the process, and there is no organic waste liquid in the aqueous phase reaction, so there is no risk of solvent residue when used in daily chemical products.

[0011] (4) Photothermal + photocatalytic dual synergistic sterilization mechanism

[0012] Under near-infrared light, the material rapidly heats up and destroys bacterial cell membranes; visible light excites the generation of reactive oxygen species to oxidize the bacteria; in the dark, the material's inherent antibacterial activity continuously inhibits the bacterial population, and it also has a high kill rate against drug-resistant bacteria.

[0013] Preferred process parameters of the present invention

[0014] The mass ratio of tea saponin to tannin was 1:0.4; the molar ratio of zinc acetate to cobalt acetate was 2:1; the amount of S-TS-CQDs added was 6% of the total mass of the metal salt; the carbon quantum hydrothermal temperature was 190℃ and the pressure was 1.5 MPa; the composite hydrothermal temperature was 130℃ and the reaction time was 16 h.

[0015] Beneficial effects of the present invention

[0016] (1) All raw materials are camellia oil and natural forestry biomass, which are completely biodegradable, free of chemical additives, and safe and non-irritating for medical and daily chemical use;

[0017] (2) It has both visible light and near-infrared dual response, and has photothermal heating and sterilization capabilities. It also has excellent dark antibacterial performance and a 99.99% inhibition rate against MRSA multidrug-resistant bacteria.

[0018] (3) The synergistic effect of bimetallic heterojunction and sulfur doping improves the photocatalytic activity by 42% compared with the existing single-metal tea saponin ZIF material;

[0019] (4) The whole hydrothermal synthesis process has no organic solvent emissions, the equipment is simple, and it is suitable for the industrial mass production of daily chemical powders and dressings.

[0020] (5) It has a wide range of applications and can be added to acne treatment essence, antibacterial masks, shower gel, wound dressing, aquatic water purification, and fruit and vegetable preservatives. Specific Implementation

[0021] Example 1 (Optimal Standard Process Group)

[0022] Step 1: Preparation of sulfur-doped tea saponin carbon quantum dots (S-TS-CQDs)

[0023] Take 1 g of high-purity tea saponin and 0.25 g of thiourea and dissolve them in 50 mL of deionized water. Transfer the solution to a high-pressure reactor and hydrothermally heat at 190℃ and 1.5 MPa for 9 h. Cool to room temperature, centrifuge at 8500 r / min for 10 min, filter the supernatant through a 0.22 μm filter membrane, and freeze-dry the filtrate to obtain sulfur-doped tea saponin carbon quantum powder.

[0024] Step 2: Preparation of tea saponin-tannin composite template solution

[0025] 1 g of tea saponin and 0.4 g of tannin were added to 80 mL of deionized water and stirred at room temperature until completely dissolved to obtain a dual-ligand template solution.

[0026] Step 3: MOF precursor mixture

[0027] Metal solution: 1 g zinc acetate and 0.5 g cobalt acetate were dissolved in 40 mL of pure water; imidazole solution: 10 g 2-methylimidazole was dissolved in 60 mL of pure water; the metal solution was slowly added dropwise to the template solution and stirred for 20 min, then the imidazole solution was slowly added dropwise and stirred for 30 min to obtain the precursor suspension.

[0028] Step 4: In-situ composite grafting

[0029] Prepare 60 mL of 1 mg / mL S-TS-CQDs aqueous dispersion, add all of it to the precursor suspension, and sonicate at 300 W for 40 min. Transfer the mixture to a hydrothermal reactor and react in a sealed container at 130℃ for 16 h. After cooling and centrifugation, wash three times each with deionized water and anhydrous ethanol, and vacuum dry at 60℃ for 18 h to obtain the target composite antibacterial powder.

[0030] Example 2 (Low Tannin Addition Group)

[0031] The amount of tannin added was 0.2 parts, and the proportions of other raw materials, hydrothermal temperature, reaction time, etc. were all kept the same as in Example 1.

[0032] Example 3 (High Tannin Addition Group)

[0033] The amount of tannin added was 0.6 parts, and the other process parameters were the same as in Example 1.

[0034] Example 4: Bimetallic Low Cobalt Ratio Group

[0035] 0.4 parts of cobalt acetate, and the remaining raw materials and preparation process are the same as in Example 1.

[0036] Example 5: Thiourea Low-Doped Group

[0037] The amount of thiourea used was 0.15 parts, and the rest were all processed according to the process in Example 1.

[0038] Comparative examples (3 control samples)

[0039] Comparative Example 1: ZIF-8 was prepared using only tea saponin as a single template, without tannins, and with only zinc acetate. The carbon quantum was replaced with tea polyphenol CQDs, and the remaining process conditions were the same as in Example 1.

[0040] Comparative Example 2: TS-ZIF single-metal materials were prepared without adding thiourea or sulfur-doped tea saponin carbon quantum;

[0041] Comparative Example 3: No in-situ hydrothermal grafting was used; MOF and S-TS-CQDs powders were physically mixed in the later stage.

[0042] Performance Comparison Data Table

[0043] Table 1. Overall performance test results of various embodiments and comparative examples of the present invention.

[0044] Material bandgap (eV) 3.32 3.41 3.24 3.38 3.44 5.22 3.56 3.33 Temperature rise (°C) of 808 nm near-infrared wavelength over 10 min 41 32.5 44.3 35.1 30.6 7.2 11.5 40.5 Antibacterial rate of MRSA under visible light (%) 99.99 96.35 99.99 97.12 94.88 76.4 83.21 88.74 Antibacterial rate (%) after standing in the dark for 24 hours 92.6 87.1 93.8 89.4 85.7 41.2 52.6 60.3 Material specific surface area (m² / g) 896 712 945 768 683 425 567 889 Carbon quantum shedding rate (after 5 washes) % 0.3 0.7 0.2 0.6 0.9 18.6 12.3 29.5 Solvent residue in daily chemical systems (mg / kg) 0 0 0 0 0 128 96 0

[0045] Data Results Analysis

[0046] (1) Light absorption and photothermal properties

[0047] Comparative Example 1 shows that the single-metal ZIF has a large bandgap and no near-infrared photothermal heating effect; all embodiments of the present invention, due to the Zn-Co bimetallic heterojunction, can be significantly heated by near-infrared light irradiation. The higher the amount of tannin added, the more significant the heating effect, which can achieve photothermal assisted sterilization.

[0048] (2) Comparison of antibacterial abilities

[0049] Examples 1 and 3 show that the optimal combination of dual ligands, bimetals, and sulfur doping achieves a 99.99% inhibition rate of drug-resistant bacteria under visible light and over 90% inhibition rate in the dark. The antibacterial effects of the three comparative groups are significantly reduced, demonstrating that dual ligands, bimetals, and sulfur doping synergistically enhance antibacterial activity.

[0050] (3) Structural stability

[0051] Comparative Example 3, which only physically mixes carbon quanta, has a shedding rate as high as 29.5% after washing; the in-situ hydrothermal grafting process of this invention firmly binds carbon quanta, with a shedding rate of less than 1%, and it does not precipitate or become ineffective when added to washing and care products for long-term use.

[0052] (4) Raw material and safety advantages

[0053] Comparative Example 1 uses tea polyphenol carbon quantum and methanol for synthesis, resulting in solvent residue; the present invention uses an all-aqueous process without organic solvents, making it suitable for the safety standards of daily chemical products such as face masks and skin care essences.

[0054] Innovative Distinction Description of the Invention

[0055] (1) The dual-ligand co-regulation of bimetallic MOF is a novel synthetic route: Existing patents only use tea saponin as a single template to prepare monometallic ZIF-8 / Cu-BTC. This invention introduces tannin to synergistically create pores and coordinate, constructs a Zn-Co heteroframe, and broadens the light absorption range. No similar patents have been published for this composite template system.

[0056] (2) Innovation of carbon quantum raw materials: Existing CQDs are all prepared with tea polyphenols. This invention directly uses tea saponin as a carbon source and thiourea is doped in situ to realize the resource utilization of camellia oil by-products and reduce raw material costs.

[0057] (3) In-situ hydrothermal chemical bonding process: Unlike the simple physical mixing powders on the market, carbon quanta are simultaneously anchored during the MOF growth stage, resulting in a strong bond that is not easily detached during water washing, making it suitable for daily chemical long-lasting antibacterial products.

[0058] (4) Photothermal synergistic innovation: Existing tea saponin MOF has no photothermal effect. This material can heat up and destroy bacteria in the near-infrared range, and also has antibacterial activity in the dark, thus broadening the application scenarios of daily chemical and medical use.

[0059] (5) Green solvent-free process: The entire process is carried out with pure water reaction, without organic solvents such as methanol and ethanol. There is no solvent residue in the daily chemical products, which meets the safety requirements for washing and care of mothers and babies and sensitive skin.

Claims

1. A tea saponin-tannin co-regulated Zn / Co bimetallic MOF / sulfur-doped tea saponin carbon quantum composite photothermal antibacterial material, characterized in that: The Zn-Co bimetallic organic framework TS-TA-ZnCo was synthesized using tea saponin and tannin dual ligands as a co-template, and the loading component was sulfur-doped tea saponin carbon quantum S-TS-CQDs. The composite material has a band gap of 3.20~3.45 eV and simultaneously possesses visible light and near-infrared dual-response photocatalytic performance and photothermal heating synergistic antibacterial effect. All raw materials are natural agricultural and forestry biomass, with no chemical surfactants added.

2. The composite photothermal antibacterial material according to claim 1, characterized in that... The proportions of each raw material are as follows: 1 part tea saponin, 0.2-0.6 parts tannin, 0.8-1.2 parts zinc acetate, 0.4-0.8 parts cobalt acetate, 8-12 parts 2-methylimidazole, and 0.15-0.4 parts thiourea.

3. The method for preparing sulfur-doped tea saponin carbon quanta according to claim 1, characterized in that... The steps are as follows: dissolve tea saponin and thiourea in deionized water, place them in a sealed high-pressure reactor, and hydrothermally react at 180~200℃ and 1.2~2.0 MPa for 8~10 h; cool to room temperature, centrifuge at 6000~8500 r / min for 5~10 min, and filter the supernatant through a 0.22 μm or 0.45 μm aqueous filter membrane; freeze-dry the filtrate to obtain sulfur-doped tea saponin carbon quantum S-TS-CQDs powder.

4. The method for preparing the composite photothermal antibacterial material according to any one of claims 1 to 2, characterized in that... It includes a three-step hydrothermal synthesis process: (1) Preparation of dual-ligand template solution: tea saponin and tannin are dissolved together in deionized water and stirred until completely dissolved to obtain composite template solution; (2) Bimetallic MOF precursor suspension: Prepare aqueous solutions of zinc acetate and cobalt acetate mixed metal salts and 2-methylimidazole aqueous solution respectively. Slowly add the metal salt solution to the template solution and stir for 10-20 min, then slowly add the imidazole solution and continue stirring for 15-30 min. (3) In-situ grafting composite: Add S-TS-CQDs aqueous dispersion to MOF precursor suspension, sonicate at 200~300 W for 20~40 min, and hydrothermally heat at 100~130℃ for 10~16 h; cool and centrifuge, wash the precipitate alternately with deionized water and anhydrous ethanol, and vacuum dry at 40~60℃ for 10~18 h to obtain the target composite antibacterial material.

5. The composite photothermal antibacterial material according to claim 1, characterized in that... It is used in daily chemical acne-removing essences, antibacterial mask base materials, antibacterial additives for washing and care products, disposable antibacterial dressings for medical use, sterilization of aquaculture water, and antibacterial agents for preserving fruits and vegetables.