PH-responsive aromatic nanocapsule as well as preparation method and application thereof

Abstract

The invention relates to a pH-responsive aromatic nanocapsule as well as a preparation method and application thereof, and the pH-responsive aromatic nanocapsule comprises the following components in percentage by mass: 0.4-10% of modified SiO2, 0.2-30% of a core material, 10.2-16% of a quaternized chitosan / polydopamine wall material and the balance of water. The preparation method comprises the following specific preparation steps: preparing a modified SiO2 suspension, adding a core material, and carrying out homogeneous emulsification under a high-speed shearing machine to prepare a Pickering emulsion; preparing a quaternized chitosan / polydopamine wall material solution; and finally, carrying out isovolumetric blending on the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution (grafting the quaternized chitosan / polydopamine wall material through the modified SiO2), and stirring to obtain the aromatic nanocapsule. Compared with the prior art, the preparation method has the advantages that the lavender essential oil is taken as a core material, the quaternized chitosan / polydopamine is taken as a wall material, and the modified SiO2 stable Pickering emulsion is taken as a template, so that the catechol-based self-adhesive nanocapsule with pH responsiveness is prepared. The nanocapsule is prepared by an emulsion template method, the preparation method is mild in condition, and the prepared nanocapsule is green and safe and has excellent adhesion and antibacterial properties.

Description

Technical Field

[0001] The invention relates to the technical field of microcapsules, and in particular to a pH-responsive aromatic nanocapsule and a preparation method and application thereof. Background Art

[0002] The textile industry is an indispensable and important part of the national economy, and the comfort of fabrics is a key indicator for evaluating functional textiles. In the hot and humid summer, a large amount of sweat can easily induce bacterial growth, accompanied by the generation of unpleasant odors and skin diseases. In response to the problems of sweat-induced bacterial proliferation and bad odors, quaternary ammonium salts, chitosan, and plant essential oils with natural antibacterial, health-care effects and fragrant odors have been widely used in the study of the antibacterial function of textiles. Aromatic essential oils usually need to be microencapsulated due to their volatility and sudden release.

[0003] This type of microcapsule with an empty core domain and a polymer shell can wrap up volatile aroma substances through interactions with fragrances (mainly including electrostatic interactions, hydrophilic and hydrophobic interactions, covalent interactions, coordination interactions, and interfacial interactions), avoiding their contact with the external environment, effectively preventing the rapid decomposition and evaporation of aroma components, and extending their storage time. It has become a hot topic in the field of fragrances. In addition, since stimuli-responsive microcapsules can accurately respond to various stimuli (such as changes in pH, humidity, enzymes, temperature, and light) to achieve controlled and sustained release of core substances, and have good stability, they have been more widely used. In the textile field, crosslinkers and adhesives are often used to bind microcapsules to fabrics. This usually leads to considerable toxicity, low adhesion, and adhesive-induced film formation that hinders the release of the core material. It also makes the fabric feel worse, prone to yellowing, and poor air permeability. Summary of the invention

[0004] The purpose of the present invention is to provide a pH-responsive aromatic nanocapsule and a preparation method and application thereof. The aromatic nanocapsule can respond to pH changes to achieve controlled release of essential oils, has good adhesion properties and antibacterial properties, and the materials used are non-toxic.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a pH-responsive aromatic nanocapsule, comprising the following components by mass percentage: 0.4-10% modified SiO2; 0.2-30% core material; 10.2-16% quaternized chitosan / polydopamine wall material; and the balance being water.

[0007] Preferably, the core material comprises essential oil, and the essential oil comprises one or more of lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, and violet essential oil.

[0008] In a second aspect, the present invention further provides a method for preparing the above-mentioned pH-responsive aromatic nanocapsules, comprising the following steps:

[0009] S1: Preparation of modified SiO2 suspension;

[0010] S2: adding the core material to the modified SiO2 suspension obtained in step S1, and homogenizing and emulsifying it under a high-speed shearing machine to prepare a Pickering emulsion;

[0011] S3: preparing quaternized chitosan / polydopamine wall material solution;

[0012] S4: the Pickering emulsion obtained in steps S2 and S3 and the quaternized chitosan / polydopamine wall material solution are mixed in equal volumes and stirred to obtain the aromatic nanocapsules.

[0013] Preferably, in step S1, the modified SiO2 suspension is prepared by dissolving modified SiO2 nanoparticles in water.

[0014] Further preferably, in step S1, the concentration of the modified SiO2 suspension is 1-10wt%, and the particle size of the modified SiO2 is 60-150nm.

[0015] Further preferably, in step S1, the modified SiO2 nanoparticles are prepared by mixing and stirring SiO2 nanoparticles and a modifier.

[0016] Further preferably, in step S1, the modifier includes methyltriethoxysilane (MTES).

[0017] Further preferably, in step S1, after the modified SiO2 nanoparticles are prepared, they are washed with anhydrous ethanol and deionized water for 1-10 times and dried to a fixed weight.

[0018] Further preferably, in step S1, the SiO2 nanoparticles are prepared by a sol-gel method.

[0019] Further preferably, in step S1, the SiO2 nanoparticles are prepared from the following raw materials, by mass percentage: 70-80% anhydrous ethanol, 2-4% tetraethyl orthosilicate, 1.5-3% ammonia water, and the balance is water.

[0020] More preferably, in step S1, the SiO2 nanoparticles are prepared from the following raw materials, by mass percentage: 76.9% anhydrous ethanol, 3.3% tetraethyl orthosilicate, 2.4% ammonia water, and the remainder is water.

[0021] Preferably, in step S2, the volume ratio of the core material to the modified SiO2 suspension is (2-5): (5-8).

[0022] Further preferably, the volume ratio of the core material to the modified SiO2 suspension includes 2:8, 3:7, 4:6, and 5:5.

[0023] Preferably, in step S2, the shear rate of the high-speed shearing machine is 10000-22000 r / min, the temperature is 15-30° C., and the time is 1-10 min.

[0024] Preferably, in step S3, the quaternized chitosan / polydopamine wall material solution is prepared by the following raw materials, measured by mass percentage: quaternized chitosan 0.2-16%; dopamine 0.2-16%; citric acid aqueous solution 0.05-2%; carbodiimide 0.0001%-0.000413%; N-hydroxysuccinimide 0.000038%-0.000292%; MES buffer 0.016%-0.16%, and the balance is water.

[0025] Further preferably, in step S3, the pH of the MES buffer is 4-8, and further preferably 6.

[0026] Further preferably, in step S3, the concentration of the citric acid aqueous solution is 0.1wt%-0.5wt%.

[0027] Further preferably, in step S3, the quaternized chitosan / polydopamine wall material solution is prepared by the following steps:

[0028] S3.1: dissolving quaternary ammonium chitosan in water, adding dopamine and stirring to obtain a quaternary ammonium chitosan / dopamine mixed solution;

[0029] S3.2: adding a 45-55° C. citric acid solution to the mixed solution obtained in step S3.1 at a stirring speed of 700-900 rpm, and then reacting at 0-4° C. for 20-30 min to obtain a quaternized chitosan / dopamine / citric acid mixed solution after the reaction is completed;

[0030] S3.3: Mix the MES buffer solution containing carbodiimide and N-hydroxysuccinimide with the quaternized chitosan / dopamine / citric acid mixed solution prepared in step S3.2, and allow to react for 8-14 hours;

[0031] S3.4: After the reaction is completed, adjust the pH to 7-10, let the reaction stand for 2-6 hours, and dialyze after the reaction is completed.

[0032] Further preferably, during the preparation process of steps S3.3 and S3.4, avoid vigorous stirring and shaking of the sample to reduce the formation of hydrogel.

[0033] Further preferably, in step S3.4, the dialysis is performed in deionized water for 2-5 days, and after the dialysis, a quaternized chitosan / polydopamine wall material solution is obtained.

[0034] Preferably, in step S4, the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution are mixed in equal volumes at a stirring rate of 300-1200 r / min, a stirring temperature of 15-40° C., and a stirring time of 30-180 min.

[0035] In a third aspect, the present invention further provides a use of the pH-responsive aromatic nanocapsules in preparing a cotton fabric finishing agent.

[0036] The present invention uses essential oil as a core material, quaternized chitosan (QCS) / polydopamine (PDA) as a wall material, and utilizes solid small particles of SiO2 as a Pickering stabilizer to stabilize the essential oil, thereby improving the stability of aromatic nanocapsules. First, the present invention synthesizes a QCS / PDA polymer by mixing QCS and dopamine (DA) solutions together, and utilizes an amide reaction between the carboxyl group of natural tribasic acid citric acid and the amino groups on DA and QCS to graft DA onto QCS, thereby avoiding the use of toxic cross-linking agents. In addition, in an alkaline environment, the phenolic hydroxyl group in DA is attacked by hydroxide to form DA anions, which can undergo a Michael addition reaction or a Schiff base reaction with the amino groups in QCS, further promoting the grafting of QCS and DA, thereby improving the stability of the capsule. Secondly, SiO2 can form a large number of hydroxyl groups in aqueous solution. These hydroxyl groups can form hydrogen bonds and have good interactions with water molecules. When partially modified by organic silane (MTES), they have better interactions with the oil phase, forming amphiphilicity, which can well encapsulate the essential oil as the core material inside it and also facilitate the further deposition of QCS / PDA polymer on its surface.

[0037] The aromatic nanocapsules of the present invention have obvious pH-responsive release characteristics, which is mainly due to the acid sensitivity of the wall material. In an acidic environment, the Schiff base bond breaks and the group is protonated, resulting in swelling and the release of essential oils. In a neutral to alkaline environment, the oxidation degree of DA increases, the adhesion strength increases, and the release of essential oils is prevented.

[0038] The present invention adopts polydopamine (PDA) and chitosan (QCS) as wall materials to prepare a novel aromatic nanocapsule. In this process, the abundant catechol groups in PDA are oxidized to quinones under alkaline conditions, and then undergo cross-linking reactions with other groups to produce adhesion. This cross-linking reaction enables the nanocapsule to be tightly attached to the surface of cotton fabric. In addition, the present invention does not need to use additional cross-linking agents and adhesives, because the polydopamine in the wall material can form hydrogen bonds with the cotton fabric, and these hydrogen bonds provide the necessary mechanical strength for the firm combination between the aromatic nanocapsule and the cotton fabric.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The aromatic nanocapsules provided by the present invention can achieve controlled release of essential oils in response to pH changes, have good adhesion properties and antibacterial properties, and the materials involved are non-toxic.

[0041] (2) The aromatic nanocapsules provided by the present invention use essential oil as the core material, quaternized chitosan / polydopamine polymer as the wall material, and modified silica as the Pickering stabilizer. A pH-responsive aromatic nanocapsule is constructed by the Pickering emulsion template method, which can isolate the core material from the outside world and improve the stability of the core material.

[0042] (3) The present invention first prepares SiO2 spheres by a sol-gel method and modifies them, uses the modified SiO2-stabilized Pickering emulsion as a template, and further deposits quaternized chitosan / polydopamine polymer wall materials on the SiO2, thereby making the prepared aromatic nanocapsules have higher thermal stability and mechanical stability, thereby improving the sustained-release properties of essential oils.

[0043] (4) The present invention can achieve controlled release of essential oils in response to pH changes, and the essential oils will be released faster under acidic conditions.

[0044] (5) The present invention does not use additional cross-linking agents and adhesives, and forms a strong bond between the aromatic nanocapsules and the cotton fabric through the hydrogen bonds formed between the polydopamine in the wall material and the cotton fabric.

[0045] (6) The preparation method of the present invention has mild conditions and a relatively simple and easy-to-control process. The prepared nanocapsules are made of non-toxic and biodegradable materials, which conforms to the green development trend. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a scanning electron microscope image of the pH-responsive aromatic nanocapsules in Example 1 of the present invention;

[0047] Figure 2This is a particle size distribution diagram of pH-responsive aromatic nanocapsules in Example 1 of the present invention;

[0048] Figure 3 is a SEM image of the modified silicon dioxide in Example 1 of the present invention;

[0049] Figure 4 A is an optical microscope image of the Pickering emulsion to which LEO is added at an oil-water ratio of 3:7 in Example 2 of the present invention;

[0050] Figure 4 B is an optical microscope image of the Pickering emulsion to which LEO is added at an oil-water ratio of 5:5 in Example 1 of the present invention;

[0051] Figure 5 Thermogravimetric analysis diagrams of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0052] Figure 6 The sustained release diagram of the aromatic nanocapsule of Example 1 of the present invention is as follows: (A) Schematic diagram of the release process of LEO from the nanocapsule under pH control; (B) Working curve of LEO-PBS / ethanol standard solution; (C) Release of lavender essential oil from the nanocapsule under different pH conditions; Under pH = 2.4, 5.7 and 7.5, the release kinetics fitting results of the nanocapsule are (D) zero order (M t / M ∞ =kt), (E) first level (M t / M ∞ =1-e -kt ) and (E) Peppas model (M t / M ∞ =kt n );

[0053] Figure 7 This is a graph showing the variation of the residual rate of cotton fabric treated with lavender essential oil and the aromatic nanocapsules in Example 1 after different washing cycles;

[0054] Figure 8 The antibacterial zone diagrams of the aromatic nanocapsules in Example 1 of the present invention against Escherichia coli and Staphylococcus aureus are as follows: (A) punching method; (B) filter paper method. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0056] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0057] Embodiment 1:

[0058] A pH-responsive aromatic nanocapsule comprises the following components in percentage by mass: 5% of modified SiO2; 25% of lavender essential oil; 15% of QCS / PDA polymer; and the balance of water.

[0059] A method for preparing pH-responsive aromatic nanocapsules, the specific steps are as follows:

[0060] (1) Prepare SiO2 balls by sol-gel method and modify them. Mix 15.0mL of deionized water and 70.0mL of anhydrous ethanol in a magnetic stirrer at 600rpm for 5min; add 2.2mL of ammonia water and stir for 10min; finally add 3.0mL of TEOS. Stir at 600rpm for 45min at room temperature. After the reaction is complete, add the modifier MTES and stir at 600rpm for 19h to modify the SiO2 balls. After the reaction is complete, centrifuge the modified SiO2, wash with anhydrous ethanol and deionized water 3-4 times, and dry to a constant weight;

[0061] (2) Add modified SiO2 nanoparticle powder and deionized water into a beaker, and prepare a modified SiO2 suspension with a mass fraction of 5% by ultrasonic dissolution. Add LEO (lavender essential oil) according to the oil-water ratio (volume ratio of lavender essential oil to modified SiO2 suspension) of 5:5, and shear homogenize at 16000 rpm for 4 minutes to obtain a modified SiO2 stabilized Pickering emulsion;

[0062] (3) Weigh 1.5g QCS, add 50ml deionized water, stir to dissolve, then add 1.5g DA, and stir at 400rpm for 30min. Then slowly add 0.2% citric acid solution preheated at 50℃ under vigorous stirring at 800rpm, then quickly cool at 4℃ and react for 30min. Then mix EDC (0.4mmol) and NHS (0.2mmol) in 5ml MES buffer solution (0.01M, pH=6), then add to the prepared mixed solution to react overnight, and finally adjust the pH to 8.5 for further oxidation. Try to avoid vigorous stirring and shaking of the sample during the preparation process to reduce the formation of hydrogel. Dialyze in deionized water for 3 days;

[0063] (4) Nanocapsules were prepared by mixing equal volumes of Pickering emulsion and QCS / PDA solution (by grafting QCS / PDA with modified SiO2) and stirring at 300 rpm for 2 h.

[0064] Comparative Example 1:

[0065] Lavender essential oil.

[0066] Comparative Example 2:

[0067] A blank capsule and a preparation method thereof, comprising carrying out the steps of Example 1, but without adding lavender essential oil.

[0068] Embodiment 2:

[0069] A pH-responsive aromatic nanocapsule and a preparation method thereof, the preparation method and raw materials are the same as those of Example 1, except that in step (2), LEO is added at an oil-water ratio of 3:7.

[0070] (1) Prepare SiO2 balls by sol-gel method and modify them. Mix 15.0mL of deionized water and 70.0mL of anhydrous ethanol in a magnetic stirrer at 600rpm for 5min; add 2.2mL of ammonia water and stir for 10min; finally add 3.0mL of TEOS. Stir at 600rpm for 45min at room temperature. After the reaction is complete, add the modifier MTES and stir at 600rpm for 19h to modify the SiO2 balls. After the reaction is complete, centrifuge the modified SiO2, wash with anhydrous ethanol and deionized water 3-4 times, and dry to a constant weight;

[0071] (2) Add modified SiO2 nanoparticle powder and deionized water into a beaker, prepare a modified SiO2 suspension with a mass fraction of 5% by ultrasonic dissolution, add LEO according to an oil-water ratio of 3:7, and shear homogenize at 16000 rpm for 4 minutes to obtain a modified SiO2 stabilized Pickering emulsion;

[0072] (3) Weigh 1.5g QCS, add 50ml deionized water, stir to dissolve, then add 1.5g DA, and stir at 400rpm for 30min. Then slowly add 0.2% citric acid solution preheated at 50℃ under vigorous stirring at 800rpm, then quickly cool at 4℃ and react for 30min. Then mix EDC (0.4mmol) and NHS (0.2mmol) in 5ml MES buffer solution (0.01M, pH=6), then add to the prepared mixed solution to react overnight, and finally adjust the pH to 8.5 for further oxidation. Try to avoid vigorous stirring and shaking of the sample during the preparation process to reduce the formation of hydrogel. Dialyze in deionized water for 3 days;

[0073] (4) Aromatic nanocapsules were prepared by mixing equal volumes of Pickering emulsion and QCS / PDA solution (by grafting QCS / PDA with modified SiO2) and stirring at 300 rpm for 2 h.

[0074] 1. Structural Characterization

[0075] like Figure 1 , which is a scanning electron microscope image of the aromatic nanocapsules prepared in Example 1. It can be seen from the image that the nanocapsules are spherical structures.

[0076] like Figure 2 , which is a dispersion particle size diagram of the aromatic nanocapsules prepared in Example 1, the average particle size of the nanocapsules is 219 nm, and the dispersion coefficient is 0.07.

[0077] like Figure 3 As shown, it is a scanning electron microscope image of the modified silica. It can be seen from the figure that after MTES grafting, the modified SiO2 still maintains a regular spherical structure with a particle size of about 90nm.

[0078] 2. Performance Characterization

[0079] 1. As Figure 4 As shown, it is an optical microscope image of the aromatic nanocapsules prepared in Examples 1 and 2. The oil-water phase volume ratio affects the droplet size and stability of the Pickering emulsion by adjusting the relative concentration of solid particles in the Pickering emulsion system and the viscosity of the emulsion. It can be seen from the figure that the particle size distribution of the Pickering emulsion in Example 1 is more uniform. After being placed for one week, some oil is precipitated in Example 2, while Example 1 is relatively stable.

[0080] 2. If Figure 5 As shown, it is the thermogravimetric analysis diagram of Example 1, Comparative Example 1 and Comparative Example 2. It can be seen from the figure that the thermogravimetric curve of Comparative Example 1 is similar to a parabola, with only a small amount of mass loss (10%) before 100°C, which may be caused by the volatilization of residual water. Most of the essential oil volatilizes before 190°C (98%). The thermal stability of Example 1 and Comparative Example 2 is significantly improved. Example 1 has obvious two stages of weight loss: the first stage occurs between 50-190°C, with a weight loss rate of about 6.8%. The mass loss in this stage is mainly caused by the volatilization of essential oil and water not embedded on the capsule surface. The second stage is within the range of 190-650°C, with a mass loss of about 40.27%. The weight loss in this stage is mainly caused by the decomposition of the wall material and the embedded essential oil under the action of high temperature.

[0081] 3. The release characteristics of the aromatic nanocapsules prepared in Example 1 under different pH environments were measured by an ELISA instrument (Multiskan SkyHigh, USA). A mixture of PBS buffer and ethanol (v:v=3:2) was used as a solvent to measure the absorbance of a series of LEO standard solutions at the maximum absorption wavelength. The LEO standard curve was drawn and fitted with concentration as the horizontal axis and absorbance as the vertical axis.

[0082] Take three portions of 2 ml microcapsule solution and place them in dialysis bags (MWCO = 3500) respectively. Then put the dialysis bags in beakers and fill them with 200 mL of PBS buffer and ethanol mixtures of different pH values ​​(v:v = 3:2) (pH 2.4, 5.7, 7.5 respectively), and place them on a shaker at 150 rpm (25°C). Take 1 mL of the release solution in the beaker at regular intervals to measure the absorbance of LEO, and then add the same volume of PBS-ethanol buffer. Calculate the cumulative release amount of LEO according to the standard curve and the cumulative release rate calculation formula to obtain its release behavior curve. Perform three sets of parallel experiments and take the average value. Then establish the adsorption curve, and use the quasi-zero-order, first-order and Peppas models to explore the adsorption kinetics.

[0083] like Figure 6 As shown in the figure, under the three acid-base gradients, the release of LEO from the aromatic nanocapsules follows a trend of first rapidly increasing and then stabilizing, which may be due to the concentrated release of the initially partially unencapsulated LEO. In addition, with the increase in environmental acidity, it can be significantly observed that the release rate of LEO is accelerated, and the release platform is reached faster, especially in an environment of pH 2.4, where 45% of LEO is released in only 3 hours and reaches the release platform, and the cumulative release in 24 hours reaches 52%. As the acidity of the environment weakens, the release rate of LEO gradually slows down. It is worth noting that in an environment of pH 7.5, only 37% of LEO is released within 24 hours and has not yet reached the release platform. Therefore, it can be determined that catechol-based nanocapsules have obvious pH-responsive release characteristics.

[0084] 4. The washing resistance of the aromatic cotton fabric treated with lavender essential oil and aromatic nanocapsules was evaluated by a washing color fastness tester (SHK-T133, Shanghai). The treatment process is to soak the cotton fabric in aromatic nanocapsules and lavender essential oil respectively, and place it on a shaker for 24 hours. The evaluation method refers to AATCC61-2003 "Home and Commercial Washing Fastness-Accelerated Method". Add water to the washing color fastness tester until it covers the central axis, set the water bath temperature to 40°C for preheating, put a sample, 200mL of water and 0.37% detergent in each stainless steel tank, and put them symmetrically on the buckle of the washing color fastness tester. Start the instrument after setting the running time (45min). One wash is equivalent to 5 hand washes or home washes or commercial washes. Set the washing cycle to 1, 2, 3, 4 and 5 times. After the washing cycle, take out the fabric and dry it at room temperature. Cut the dried aromatic fabric into pieces, and use anhydrous ethanol to extract LEO in the aromatic fabric, and measure the absorbance of the extract by an enzyme marker. The residual amount of nanocapsules on the fabric was defined as the ratio of the residual essential oil after washing to the residual essential oil without washing. Three parallel experiments were performed.

[0085] like Figure 7As shown in the figure, for the aromatic fabrics directly treated with LEO, after 5 washes, the residual rate of essential oil on the aromatic fabrics was less than 10%, and after 25 washes, the residual rate was only 1%. For the group of aromatic fabrics treated with aromatic nanocapsules, after 5 washes, the residual rate was 68%, which was 7.2 times that of the group directly treated with LEO. After 25 washes, the residual rate of the group treated with aromatic nanocapsules was still maintained at 13%. This shows that nanocapsules are better than LEO in adsorbing on the fabric surface and retaining LEO on cotton fabrics.

[0086] 5. The antibacterial property of the aromatic nanocapsules prepared in Example 1 was determined by the inhibition zone method. The inhibition zone determination experiment was carried out by the punching method and the filter paper method respectively. Punching method: Take 100 μL of the bacterial suspension diluted to 106 CFU / mL, add it to the prepared nutrient agar medium plate and spread it evenly. Use a puncher with a diameter of 6 mm to punch holes on the coated plate. Then add about 150 μL of aromatic nanocapsule solution to each hole, filling it up without overflowing. Three groups of parallels were set for each bacteria, and physiological saline nanocapsule solution was used as a blank control. The plate was placed in a biochemical incubator and cultured at 37°C for 24 hours. The diameter of the inhibition zone was measured by a vernier caliper, and the average value was calculated. Filter paper method: Place a filter paper soaked in the aromatic nanocapsule solution on the coated plate, replace the punching, and carry out the same experiment.

[0087] like Figure 8 As shown in the figure, the results of both methods indicate that nanocapsules have an inhibitory effect on Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli). The diameter of the inhibition zone obtained by the punching method is much larger than that of the filter paper method, because the amount of nanocapsules added by the punching method is much higher than the amount of nanocapsules adsorbed by the filter paper. In addition, it can be seen from the results of the punching method that the inhibitory effect of nanocapsules on Staphylococcus aureus is not as good as that on Escherichia coli, which may be related to the cell wall components. In the results obtained by the filter paper method, the inhibitory effects of the two bacteria are similar. The antibacterial effect of nanocapsules mainly comes from quaternary ammonium chitosan and lavender essential oil. The cationicity of chitosan quaternary ammonium salt can lead to the destruction of bacterial cell walls and outer membrane structures and the inhibition of biofilm activity. In addition, lavender essential oil contains a variety of volatile small molecules that can penetrate into cells and cause microbial death.

[0088] In summary, the aromatic nanocapsules prepared by the present invention can achieve controlled release of essential oils in response to pH changes, have good adhesion properties without using cross-linking agents and adhesives, and have certain antibacterial properties.

[0089] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A pH-responsive aromatic nanocapsule, characterized in that: Calculated by mass percentage, the invention comprises the following components: 0.4-10% of modified SiO2; 0.2-30% of core material; 10.2-16% of quaternized chitosan / polydopamine wall material; and the balance is water.

2. The pH-responsive aromatic nanocapsule according to claim 1, characterized in that: The core material includes essential oil, and the essential oil includes one or more of lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, and violet essential oil.

3. A method for preparing pH-responsive aromatic nanocapsules according to any one of claims 1 to 2, characterized in that: The steps include: S1: Preparation of modified SiO2 suspension; S2: adding the core material to the modified SiO2 suspension obtained in step S1, and homogenizing and emulsifying it under a high-speed shearing machine to prepare a Pickering emulsion; S3: preparing quaternized chitosan / polydopamine wall material solution; S4: the Pickering emulsion obtained in steps S2 and S3 and the quaternized chitosan / polydopamine wall material solution are mixed in equal volumes and stirred to obtain the aromatic nanocapsules.

4. The method for preparing a pH-responsive aromatic nanocapsule according to claim 3, characterized in that: In step S1, the modified SiO2 suspension is prepared by dissolving modified SiO2 nanoparticles in water, the modified SiO2 nanoparticles are prepared by mixing and stirring SiO2 nanoparticles and a modifier, the modifier includes methyltriethoxysilane, and the SiO2 nanoparticles are prepared by a sol-gel method.

5. The method for preparing a pH-responsive aromatic nanocapsule according to claim 3, characterized in that: The concentration of the modified SiO2 suspension is 1-10wt%, and the particle size of the modified SiO2 is 60-150nm.

6. The method for preparing a pH-responsive aromatic nanocapsule according to claim 3, characterized in that: In step S2, the volume ratio of the core material to the modified SiO2 suspension is (2-5): (5-8), the shear rate of the high-speed shearing machine is 10000-22000 r / min, the temperature is 15-30°C, and the time is 1-10 min.

7. The method for preparing a pH-responsive aromatic nanocapsule according to claim 3, characterized in that: In step S3, the quaternized chitosan / polydopamine wall material solution is prepared by the following raw materials, measured by mass percentage: 0.2-16% quaternized chitosan; 0.2-16% dopamine; 0.05-2% citric acid aqueous solution; 0.0001%-0.000413% carbodiimide; 0.000038%-0.000292% N-hydroxysuccinimide; 0.016%-0.16% MES buffer, and the balance is water.

8. The method for preparing a pH-responsive aromatic nanocapsule according to claim 7, characterized in that: In step S3, the quaternized chitosan / polydopamine wall material solution is prepared by the following steps: S3.1: dissolving quaternary ammonium chitosan in water, adding dopamine and stirring to obtain a quaternary ammonium chitosan / dopamine mixed solution; S3.2: adding a 45-55° C. citric acid solution to the mixed solution obtained in step S3.1 at a stirring speed of 700-900 rpm, and then reacting at 0-4° C. for 20-30 min to obtain a quaternized chitosan / dopamine / citric acid mixed solution after the reaction is completed; S3.3: Mix the MES buffer solution containing carbodiimide and N-hydroxysuccinimide with the quaternized chitosan / dopamine / citric acid mixed solution prepared in step S3.2, and allow to react for 8-14 hours; S3.4: After the reaction is completed, adjust the pH to 7-10, let the reaction stand for 2-6 hours, and dialyze after the reaction is completed.

9. The method for preparing a pH-responsive aromatic nanocapsule according to claim 3, characterized in that: In step S4, the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution are mixed in equal volumes at a stirring rate of 300-1200 r / min, a stirring temperature of 15-40° C., and a stirring time of 30-180 min.

10. Use of the pH-responsive aromatic nanocapsule according to any one of claims 1 to 2 in preparing a cotton fabric finishing agent.

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