A pH-responsive aromatic nanocapsule, its preparation method and application

Abstract

This invention relates to a pH-responsive aromatic nanocapsule, its preparation method, and its application. By mass percentage, it comprises the following components: 0.4-10% modified SiO2, 0.2-30% core material, 10.2-16% quaternized chitosan / polydopamine wall material, and the balance being water. The specific preparation steps are as follows: a modified SiO2 suspension is prepared, and the core material is added. The suspension is then homogenized and emulsified under a high-speed shear mill to prepare a Pickering emulsion. A quaternized chitosan / polydopamine wall material solution is prepared. Finally, the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution are mixed in equal volumes (by grafting quaternized chitosan / polydopamine wall material onto modified SiO2) and stirred to obtain the aromatic nanocapsule. Compared with existing technologies, this invention uses lavender essential oil as the core material, quaternized chitosan / polydopamine as the wall material, and a modified SiO2-stabilized Pickering emulsion as a template to prepare a pH-responsive catechol-based self-adhesive nanocapsule. This invention prepares nanocapsules via an emulsion template method, which is mild and produces green and safe nanocapsules with excellent adhesion and antibacterial properties.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and in particular to a pH-responsive aromatic nanocapsule, its preparation method, and its application. Background Technology

[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, excessive sweat easily induces bacterial growth, resulting in unpleasant odors and potentially triggering skin diseases. To address the problems of sweat-induced bacterial proliferation and unpleasant odors, quaternary ammonium salts, chitosan, and plant essential oils with natural antibacterial, health-promoting, and aromatic properties have been widely used in research on the antibacterial function of textiles. Due to their volatility and rapid release, aromatic essential oils typically require microencapsulation.

[0003] Microcapsules with hollow core domains and polymer shells can encapsulate volatile aroma substances through interactions with fragrances (mainly including electrostatic interactions, hydrophilic and hydrophobic interactions, covalent interactions, coordination interactions, and interfacial interactions), preventing them from contacting the external environment, effectively preventing the rapid decomposition and evaporation of aroma components, and extending their shelf life. This has become a hot topic in the fragrance industry. Furthermore, stimulus-responsive microcapsules, due to their ability to precisely respond to various stimuli (such as changes in pH, humidity, enzymes, temperature, and light) to achieve controlled and sustained release of the core substance, and their good stability, have gained wider application. In the textile industry, crosslinking agents and adhesives are often used to bind microcapsules to fabrics. This typically leads to problems such as considerable toxicity, low adhesion, and adhesive-induced film formation that hinders the release of the core material, as well as deteriorating fabric hand feel, yellowing, and poor breathability. Summary of the Invention

[0004] The purpose of this invention is to provide a pH-responsive aromatic nanocapsule, its preparation method, and its application. The aromatic nanocapsule can control the release of essential oils in response to pH changes, has good adhesion properties and antibacterial properties, and the materials used are non-toxic.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a pH-responsive aromatic nanocapsule, comprising, 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 oils, which include one or more of lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, and violet essential oil.

[0008] Secondly, the present invention also 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: Add core material to the modified SiO2 suspension obtained in step S1 and homogenize and emulsify it under a high-speed shear machine to prepare Pickering emulsion;

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

[0012] S4: The Pickering emulsion obtained in steps S2 and S3 is mixed with an equal volume of quaternized chitosan / polydopamine wall material solution 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] More preferably, in step S1, the concentration of the modified SiO2 suspension is 1-10 wt%, and the particle size of the modified SiO2 is 60-150 nm.

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

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

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

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

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

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

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

[0022] More 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 shearing rate of the high-speed shearing machine is 10000-22000 r / min, the temperature is 15-30℃, 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 in the following mass percentages: 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%, with the balance being water.

[0025] More preferably, in step S3, the pH of the MES buffer solution is 4-8, and even more preferably 6.

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

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

[0028] S3.1: Dissolve quaternized chitosan in water, add dopamine and mix and stir to obtain a quaternized chitosan / dopamine mixed solution;

[0029] S3.2: At a stirring speed of 700-900 rpm, add citric acid solution at 45-55℃ dropwise to the mixed solution obtained in step S3.1, and then react at 0-4℃ for 20-30 min. After the reaction is completed, a quaternized chitosan / dopamine / citric acid mixed solution is obtained.

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

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

[0032] More preferably, during the preparation processes of steps S3.3 and S3.4, vigorous stirring and shaking of the sample should be avoided as much as possible to reduce the formation of hydrogel.

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

[0034] Preferably, in step S4, the stirring rate for mixing the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution in equal volumes is 300-1200 r / min, the stirring temperature is 15-40℃, and the stirring time is 30-180 min.

[0035] Thirdly, the present invention also provides the application of the above-mentioned pH-responsive aromatic nanocapsules in the preparation of cotton fabric finishing agents.

[0036] This invention uses essential oils as the core material and quaternized chitosan (QCS) / polydopamine (PDA) as the wall material, and utilizes solid small-particle SiO2 as a pickering stabilizer to stabilize the essential oils, thereby improving the stability of aromatic nanocapsules. Firstly, this invention synthesizes a QCS / PDA polymer by mixing QCS and dopamine (DA) solutions together. Then, it utilizes the amide reaction between the carboxyl groups of the natural tribasic acid citric acid and the amino groups on DA and QCS to graft DA onto QCS, avoiding the use of toxic crosslinking agents. Furthermore, under alkaline conditions, the phenolic hydroxyl groups in DA are attacked by hydroxide ions to form DA anions, which can undergo Michael addition reactions or Schiff base reactions with the amino groups in QCS, further promoting the grafting of QCS and DA and improving capsule stability. Secondly, SiO2 can form a large number of hydroxyl groups in aqueous solution. These hydroxyl groups can form hydrogen bonds and have good interaction with water molecules. When partially modified by organosilane (MTES), it also has good interaction with the oil phase, forming an amphiphilic property. This allows it to effectively encapsulate the essential oil as the core material inside, while also facilitating the further deposition of QCS / PDA polymers on its surface.

[0037] The aromatic nanocapsules of this invention exhibit significant pH-responsive release characteristics, primarily due to the acid sensitivity of the wall material. In acidic environments, Schiff base bonds break, and groups protonate, leading to swelling and the release of essential oils. Conversely, in neutral to alkaline environments, the oxidation degree of DA increases, resulting in increased adhesion strength and preventing the release of essential oils.

[0038] This invention utilizes 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, subsequently undergoing a cross-linking reaction with other groups, resulting in adhesion. This cross-linking allows the nanocapsules to adhere tightly to the surface of cotton fabric. Furthermore, this invention eliminates the need for additional cross-linking agents and adhesives because the polydopamine in the wall material forms hydrogen bonds with the cotton fabric. These hydrogen bonds provide the necessary mechanical strength for a strong bond between the aromatic nanocapsules 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 control the 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 nanocapsule provided by the present invention uses essential oil as core material, quaternized chitosan / polydopamine polymer as wall material, and modified silica as 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) In this invention, SiO2 spheres are first prepared by sol-gel method and modified. The modified SiO2 stabilized Pickering emulsion is used as a template, and quaternized chitosan / polydopamine polymer wall material is further deposited on SiO2, so that the prepared aromatic nanocapsules have high thermal stability and mechanical stability, and improve the sustained-release properties of essential oils.

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

[0044] (5) This invention does not use additional crosslinking agents and adhesives. Through the hydrogen bonds formed between polydopamine in the wall material and cotton fabric, the aromatic nanocapsules and cotton fabric form a strong bond.

[0045] (6) The preparation method of the present invention is mild and the process is relatively simple and easy to control. The nanocapsules prepared are made of non-toxic and biodegradable materials, which is in line with the trend of green development. Attached Figure Description

[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 the pH-responsive aromatic nanocapsules in Example 1 of the present invention;

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

[0049] Figure 4 A is an optical microscope image of the Pickering emulsion with LEO 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 with LEO added at an oil-water ratio of 5:5 in Example 1 of the present invention;

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

[0052] Figure 6 The following is a diagram illustrating the sustained-release effect of the aromatic nanocapsules in Example 1 of this invention: (A) Schematic diagram of LEO release from the nanocapsules under pH control; (B) Working curve of LEO-PBS / ethanol standard solution; (C) Release of lavender essential oil from the nanocapsules under different pH conditions; The release kinetics fitting results of the nanocapsules at pH = 2.4, 5.7, and 7.5 are as follows: (D) Zero-order (M) t / M ∞ =kt), (E) Level 1 (M) t / M ∞ =1-e -kt () and (E) Peppas model (M) t / M ∞ =kt n );

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

[0054] Figure 8 The inhibition zones of the aromatic nanocapsules against Escherichia coli and Staphylococcus aureus in Example 1 of this invention are shown in the diagrams: (A) perforation method; (B) filter paper method. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

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

[0057] Example 1:

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

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

[0060] (1) SiO2 spheres were prepared and modified by the sol-gel method. 15.0 mL of deionized water and 70.0 mL of anhydrous ethanol were mixed in a magnetic stirrer at 600 rpm for 5 min; 2.2 mL of ammonia water was added and stirred for 10 min; finally, 3.0 mL of TEOS was added. The mixture was stirred at 600 rpm for 45 min at room temperature. After the reaction was completed, the modifier MTES was added and the mixture was stirred at 600 rpm for 19 h to modify the SiO2 spheres. After the reaction was completed, the modified SiO2 was centrifuged, washed 3-4 times with anhydrous ethanol and deionized water, and dried to a fixed weight.

[0061] (2) Modified SiO2 nanoparticle powder and deionized water were added to a beaker, and a modified SiO2 suspension with a mass fraction of 5% was prepared by ultrasonic dissolution. LEO (lavender essential oil) was added at an oil-to-water ratio (volume ratio of lavender essential oil to modified SiO2 suspension) of 5:5, and the mixture was sheared and homogenized 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, stir at 400rpm for 30min. Then, under vigorous stirring at 800rpm, slowly add 0.2% citric acid solution preheated at 50℃, then rapidly 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 and react overnight. Finally, adjust the pH to 8.5 for further oxidation. During the preparation process, avoid vigorous stirring and shaking of the sample as much as possible to reduce the formation of hydrogel. Dialyze with 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 onto 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 its preparation method are described, following the steps of Example 1, but without the addition of lavender essential oil.

[0068] Example 2:

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

[0070] (1) SiO2 spheres were prepared and modified by the sol-gel method. 15.0 mL of deionized water and 70.0 mL of anhydrous ethanol were mixed in a magnetic stirrer at 600 rpm for 5 min; 2.2 mL of ammonia water was added and stirred for 10 min; finally, 3.0 mL of TEOS was added. The mixture was stirred at 600 rpm for 45 min at room temperature. After the reaction was completed, the modifier MTES was added and the mixture was stirred at 600 rpm for 19 h to modify the SiO2 spheres. After the reaction was completed, the modified SiO2 was centrifuged, washed 3-4 times with anhydrous ethanol and deionized water, and dried to a fixed weight.

[0071] (2) Modified SiO2 nanoparticle powder and deionized water were added to a beaker, and a modified SiO2 suspension with a mass fraction of 5% was prepared by ultrasonic dissolution. LEO was added at an oil-water ratio of 3:7, and the mixture was sheared and homogenized 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, stir at 400rpm for 30min. Then, under vigorous stirring at 800rpm, slowly add 0.2% citric acid solution preheated at 50℃, then rapidly 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 and react overnight. Finally, adjust the pH to 8.5 for further oxidation. During the preparation process, avoid vigorous stirring and shaking of the sample as much as possible to reduce the formation of hydrogel. Dialyze with 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] I. Structural Characterization

[0075] like Figure 1 The image shown is a scanning electron microscope image of the aromatic nanocapsules prepared in Example 1. As can be seen from the image, the nanocapsules have a spherical structure.

[0076] like Figure 2 The figure shows the 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 The image shown is a scanning electron microscope image of modified silica. As can be seen from the image, after MTES grafting, the modified SiO2 still maintains a regular spherical structure with a particle size of about 90 nm.

[0078] II. Performance Characterization

[0079] 1. For example Figure 4 The image shows optical microscope images of the aromatic nanocapsules prepared in Examples 1 and 2. The oil-water volume ratio affects the droplet size and stability of the Pickering emulsion by adjusting the relative concentration of solid particles and the viscosity of the emulsion. As can be seen from the figures, the Pickering emulsion in Example 1 has a more uniform particle size distribution. After one week of storage, some oil precipitated in Example 2, while Example 1 remained relatively stable.

[0080] 2. For example Figure 5 The figures show the thermogravimetric analysis (TGA) curves for Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the figures, the TGA curve of Comparative Example 1 resembles a parabola, with only a small mass loss (10%) before 100°C, likely due to the evaporation of residual moisture. Most of the essential oil evaporates before 190°C (98%). The thermal stability of Example 1 and Comparative Example 2 is significantly improved. Example 1 exhibits two distinct stages of weight loss: the first stage occurs between 50-190°C, with a weight loss rate of approximately 6.8%, primarily caused by the evaporation of unencapsulated essential oil and moisture from the capsule surface; the second stage occurs within the 190-650°C range, with a mass loss of approximately 40.27%, mainly due to the decomposition of the wall material and encapsulated essential oil under high temperatures.

[0081] 3. The release characteristics of the aromatic nanocapsules prepared in Example 1 under different pH conditions were determined using a microplate reader (Multiskan SkyHigh, USA). A mixture of PBS buffer and ethanol (v:v = 3:2) was used as the solvent, and the absorbance of a series of LEO standard solutions was measured at the maximum absorption wavelength. A LEO standard curve was plotted and fitted with concentration on the x-axis and absorbance on the y-axis.

[0082] Three 2ml aliquots of the microcapsule solution were placed in separate dialysis bags (MWCO = 3500). The dialysis bags were then placed in beakers, each containing 200mL of a mixture of PBS buffer and ethanol at different pH values ​​(v:v = 3:2) (pH 2.4, 5.7, and 7.5). The beakers were shaken at 150 rpm (25℃). At regular intervals, 1mL of the released solution was taken from each beaker to measure the absorbance of LEO, and the same volume of PBS-ethanol buffer was added afterward. The cumulative release of LEO was calculated using the standard curve and the cumulative release rate formula, yielding the release behavior curve. Three parallel experiments were performed, and the average value was taken. Adsorption curves were then established, and quasi-zero-order, first-order, and Peppas models were used to investigate the adsorption kinetics.

[0083] like Figure 6 As shown, under three acid-base gradients, the release of LEO from the aromatic nanocapsules followed a trend of initially increasing rapidly and then stabilizing, possibly due to the concentrated release of the initially unencapsulated LEO. Furthermore, with increasing environmental acidity, a significant acceleration in the LEO release rate was observed, reaching the release plateau more quickly. Particularly at pH 2.4, 45% of the LEO was released and reached the plateau in just 3 hours, with a cumulative release of 52% over 24 hours. As environmental acidity decreased, the LEO release rate gradually slowed down. Notably, at pH 7.5, only 37% of the LEO was released within 24 hours, and the release plateau was not yet reached. Therefore, it can be confirmed that the catechol-based nanocapsules exhibit significant pH-responsive release characteristics.

[0084] 4. The wash fastness of aromatic cotton fabrics treated with lavender essential oil and aromatic nanocapsules was evaluated using a wash fastness meter (SHK-T133, Shanghai). The treatment process involved immersing the cotton fabrics in aromatic nanocapsules and lavender essential oil, respectively, and placing them on a shaker for 24 hours. The evaluation method followed AATCC 61-2003, "Household and Commercial Wash Fastness – Accelerated Method". Water was added to the wash fastness meter until it reached the centerline, and the water bath temperature was set to 40℃ for preheating. One sample, 200 mL of water, and 0.37% detergent were placed in each stainless steel container, symmetrically placed on the clips of the wash fastness meter. The running time (45 min) was set, and the instrument was started. One wash was equivalent to 5 hand washes, household washes, or commercial washes. Washing cycles were set to 1, 2, 3, 4, and 5. After each washing cycle, the fabric was removed and dried at room temperature. The dried aromatic fabric was cut into small pieces, and LEO was extracted from the aromatic fabric using anhydrous ethanol. The absorbance of the extract was measured using a microplate reader. The amount of nanocapsule residue on the fabric was defined as the ratio of the amount of residual essential oil after washing to the amount of residual essential oil before washing. Three parallel experiments were conducted.

[0085] like Figure 7As shown, for fragrance fabrics treated directly with LEO, the essential oil residue rate was less than 10% after 5 washes, and only 1% after 25 washes. However, for the group of fragrance fabrics treated with fragrance nanocapsules, the residue rate was still 68% after 5 washes, 7.2 times that of the directly LEO-treated group. After 25 washes, the residue rate of the fragrance nanocapsule-treated group remained at 13%. This indicates that nanocapsules adsorb onto the fabric surface better than LEO and retain LEO on cotton fabrics.

[0086] 5. The antibacterial activity of the aromatic nanocapsules prepared in Example 1 was determined by the inhibition zone method. Inhibition zone determination experiments were conducted using both the perforation method and the filter paper method. Perforation method: 100 μL of bacterial suspension diluted to 10⁶ CFU / mL was added to a prepared nutrient agar plate and spread evenly. A 6 mm diameter perforator was used to punch holes in the plate. Approximately 150 μL of aromatic nanocapsule solution was then added to each hole, filling it completely without overflowing. Three replicates were set up for each type of bacteria, with physiological saline nanocapsule solution used as a blank control. The plates were placed in a biochemical incubator and incubated at 37°C for 24 h. The diameter of the inhibition zone was measured using calipers, and the average value was calculated. Filter paper method: Filter paper soaked in the aromatic nanocapsule solution was placed on the spread plate instead of perforation, and the same experiment was performed.

[0087] like Figure 8 As shown, both methods demonstrate that nanocapsules have an inhibitory effect on Staphylococcus aureus and Escherichia coli. The diameter of the inhibition zone obtained by the perforation method is much larger than that obtained by the filter paper method. This is because the amount of nanocapsules added by the perforation method is much higher than that adsorbed by the filter paper method. Furthermore, the results of the perforation method show 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 composition. In contrast, the inhibitory effects on the two bacteria are similar in the filter paper method. The antibacterial effect of nanocapsules mainly comes from quaternary ammonium chitosan and lavender essential oil. The cationic nature of the quaternary ammonium chitosan leads to the destruction of bacterial cell walls and outer membrane structures, as well as the inhibition of biofilm activity. In addition, lavender essential oil contains various volatile small molecules that can penetrate into cells, leading to microbial death.

[0088] In summary, the aromatic nanocapsules prepared by this invention can achieve controlled release of essential oils in response to pH changes, have good adhesion properties without the use of crosslinking agents and adhesives, and also have certain antibacterial properties.

[0089] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A method for preparing pH-responsive aromatic nanocapsules, characterized in that, The aromatic nanocapsules, by weight percentage, comprise the following components: modified SiO2 0.4-10%; core material 0.2-30%; quaternized chitosan / polydopamine wall material 10.2-16%; the balance being water. The preparation method includes the following steps: S1: Preparation of modified SiO2 suspension; S2: Add core material to the modified SiO2 suspension obtained in step S1 and homogenize and emulsify it under a high-speed shear machine to prepare Pickering emulsion; S3: Preparation of quaternized chitosan / polydopamine wall material solution; S4: The Pickering emulsion obtained in steps S2 and S3 is mixed with an equal volume of quaternized chitosan / polydopamine wall material solution and stirred to obtain the aromatic nanocapsules; 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 with a modifier, wherein the modifier includes methyltriethoxysilane. The SiO2 nanoparticles are prepared by the sol-gel method. In step S3, the quaternized chitosan / polydopamine wall material solution is prepared by the following raw materials in the following mass percentages: 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%, with the balance being water; In step S3, the quaternized chitosan / polydopamine wall material solution is prepared through the following steps: S3.1: Dissolve quaternized chitosan in water, add dopamine and mix and stir to obtain a quaternized chitosan / dopamine mixed solution; S3.2: Under stirring conditions, add citric acid solution at 45-55 °C dropwise to the mixed solution obtained in step S3.1, and then react at 0-4 °C for 20-30 min. After the reaction is completed, a quaternized chitosan / dopamine / citric acid mixed solution is obtained. S3.3: Mix the MES buffer containing carbodiimide and N-hydroxysuccinimide with the quaternized chitosan / dopamine / citric acid mixed solution prepared in step S3.2, and let it stand to react; S3.4: After the reaction is complete, adjust the pH to 7-10, let the reaction stand, and dialyze after the reaction is complete.

2. The method for preparing a pH-responsive aromatic nanocapsule according to claim 1, characterized in that, The core material includes essential oils, which include one or more of lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, and violet essential oil.

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

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

5. The method for preparing a pH-responsive aromatic nanocapsule according to claim 1, characterized in that, In step S4, the stirring rate for mixing the Pickering emulsion and the quaternized chitosan / polydopamine wall material solution in equal volumes is 300-1200 r / min, the stirring temperature is 15-40 ℃, and the stirring time is 30-180 min.

6. The application of a pH-responsive aromatic nanocapsule prepared by the preparation method according to any one of claims 1-5 in the preparation of a cotton fabric finishing agent.

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