CN111937902A

CN111937902A - Zinc oxide nano antibacterial compound and preparation method thereof

Info

Publication number: CN111937902A
Application number: CN202010812918.1A
Authority: CN
Inventors: 张咚咚; 胡思; 张敏; 周显青
Original assignee: Henan University of Technology
Current assignee: Henan University of Technology
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2020-11-17
Anticipated expiration: 2040-08-13
Also published as: CN111937902B

Abstract

The invention relates to a zinc oxide nano antibacterial compound and a preparation method thereof. The preparation method comprises the steps of preparing the zinc oxide nano particles, modifying mesoporous silicon dioxide on the surfaces of the zinc oxide nano particles and modifying surface amphoteric groups. Specifically, through the mesoporous silicon dioxide modified on the surface of the zinc oxide nanoparticles, the zinc oxide nanoparticles can play a bacteriostatic role, pollution caused by direct contact of a bacteriostatic core of the zinc oxide nanoparticles and grains is avoided, more importantly, the designed amphiprotic group C16CA can enable the zinc oxide nanocomposite to have the characteristic of acid precipitation and alkali dissolution, and can be removed through rinsing, so that potential food safety hazards possibly caused by the zinc oxide nanocomposite are thoroughly eliminated.

Description

Zinc oxide nano antibacterial compound and preparation method thereof

Technical Field

The invention belongs to the field of materials, and particularly relates to a zinc oxide nano antibacterial compound and a preparation method thereof.

Background

The food safety problem is the most fundamental and bottom line of concern for the nation's democratics. The grains are used as raw materials of a plurality of downstream food industries, have rich nutrient substances, are easy to rot, mildew and biotoxin and other food safety problems once being stored poorly, have a profound influence on the whole industrial chain, are difficult to remove, are one of key sources of food safety process control, and are also one of key points of influencing food safety.

In the traditional research process of preventing the heating and the mildew of the grains, the grain storage environment is generally changed by adopting methods of cooling and dehumidifying, such as ventilation, drying and the like, so that the aim of inhibiting the growth of microorganisms is fulfilled. Particularly, the grain storage technology commonly adopted in various domestic grain storage warehouses is a four-in-one grain storage technology of mechanical ventilation, circulation fumigation, grain condition measurement and control and grain cooling, and the application of the four-in-one grain storage technology has remarkable effects on reducing grain moisture, grain pile micro-ecological oxygen content and grain temperature, and can effectively inhibit large-scale microbial growth and mycotoxin metabolism in the grain storage process. With the continuous improvement of the requirements of 'green health', 'quality improvement and synergy' and the like in the grain storage process, a grain storage technology for filling nitrogen and carbon dioxide gas in controlled atmosphere storage is developed, and the grain storage technology has a certain function of mildew prevention, but has inevitable function dead angles, so that the local heating and mildew of grains are caused. Therefore, the traditional method cannot completely kill the microorganisms carried by the grains, cannot fundamentally solve the phenomenon of spoilage and mildewing of the grains and cannot fundamentally inhibit the metabolism generation of harmful microbial toxins in the grains.

However, with the continuous development of nanotechnology, people find more and more effective bacteriostasis modes. Some nano antibacterial materials can inhibit the growth and metabolic activity of microorganisms and can kill the microorganisms. Currently, the most widely used nano antibacterial material is silver nano particles. Silver has been widely used in ancient times for antisepsis and disinfection, and for inhibiting the growth of microorganisms. The silver nano-particles have more stable physical, chemical and biological characteristics and more excellent antibacterial effect. The silver nanoparticles realize the bacteriostatic function through the photocatalytic effect and the contact effect, have the characteristics of wide bactericidal spectrum and no drug resistance, are widely applied to the fields of textiles, medicines, sanitation, packaging and the like, can obviously inhibit the growth of microorganisms, and greatly improve the food sanitation condition. However, if the nano silver particles are directly applied to the inhibition of microorganisms on the surface of the grain, if the nano silver particles are not properly treated, the problem that heavy metals in the food exceed the standard may occur, and the safety of the food is also harmed.

Therefore, the technical scheme of the invention is provided.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a zinc oxide nano antibacterial compound, and a preparation method and application thereof. The zinc oxide nano antibacterial compound can effectively inhibit fungus breeding in the process of grain storage, can avoid direct contact of zinc oxide nano particles and grains, and meanwhile, as the amphoteric group C16CA is modified, the zinc oxide nano antibacterial compound can be removed and recovered by the aid of the acid-precipitation alkali-dissolution effect in the later period, so that safety of grain food is fundamentally guaranteed.

The invention provides a preparation method of a zinc oxide nano antibacterial compound, which comprises the following steps:

(I) preparing zinc oxide nano particles:

(1) adding zinc acetate dihydrate into ultrapure water, uniformly stirring, adding hexadecyl trimethyl ammonium bromide, and uniformly stirring to obtain a mixed solution a;

(2) adding a sodium hydroxide solution into the mixed solution a, stirring at room temperature for reaction, dispersing, performing hydrothermal reaction, centrifuging, washing and vacuum drying the obtained precipitate to obtain zinc oxide nanoparticles;

(II) modifying the mesoporous silica on the surface of the zinc oxide nano particles:

(a) uniformly dispersing zinc oxide nanoparticles in an aqueous solution, adding hexadecyl trimethyl ammonium bromide, and uniformly stirring at constant temperature to obtain a mixed solution b;

(b) dropwise adding a methanol solution of tetraethyl orthosilicate into the mixed solution b, maintaining the constant temperature and continuously stirring, and repeatedly dropwise adding once after the stirring is finished to obtain a mixed solution c;

(c) carrying out hydrothermal reaction on the mixed solution c, and washing cetyl trimethyl ammonium bromide by using a methanol solution of sodium chloride after the hydrothermal reaction is finished to obtain zinc oxide nanoparticles with the surfaces modified with mesoporous silica;

(III) surface amphiprotic group modification:

(i) continuously stirring methyl acrylate and hexadecyl ammonium in a methanol solution for reaction, and removing methanol and redundant methyl acrylate after the reaction is finished to obtain a compound C16 ME;

(ii) stirring C16ME and sodium hydroxide solution in methanol at room temperature for reaction, evaporating to obtain white solid, and washing with hexane and methanol to obtain amphoteric compound C16 CA;

(iii) adding C16CA and the zinc oxide nanoparticles with the surface modified with mesoporous silica into water, adjusting the pH to be alkaline by using a sodium hydroxide solution, and stirring to uniformly disperse the system to obtain a mixed solution d;

(iv) and (4) adding a hydrogen chloride solution into the mixed solution d to adjust the pH value to acidity so as to obtain a suspension, and drying to obtain the zinc oxide nano-composite.

The research idea of the scheme of the invention is as follows:

the antibacterial mechanism of the zinc oxide nanoparticles is due to the surface effect and the contact effect of the nanoparticles, and verification tests designed by the invention find that the zinc oxide nanoparticles can be applied to the inhibition of microorganisms in the storage process of grains without changing the characteristics of the grains, the good stability of the zinc oxide nanoparticles enables the zinc oxide nanoparticles to exert the antibacterial characteristics for a super long time, and the growth of the microorganisms can be effectively inhibited without replacing new antibacterial materials in the whole storage period of the grains, so that the mildewing of the grains and the generation of biotoxins are avoided.

When the zinc oxide nanoparticles are used for inhibiting microorganisms in the grain storage process, in order to not influence the subsequent wheat processing and eating and ensure the absolute safety of the subsequent wheat processing process, the research specially designs a removal procedure of the zinc oxide nanoparticles, namely, a layer of mesoporous silica containing amphoteric groups is modified on the surface of the zinc oxide nanoparticles to prepare a zinc oxide-mesoporous silica-amphoteric group modified nano compound, so that the characteristics of acid precipitation and alkali dissolution can be utilized, most of residues of grains mixed with the nano antibacterial material are removed through wheat washing or wheat wetting operation, and the food safety risk cannot be caused even if trace residues exist.

For the convenience of understanding, the meaning of "acid precipitation and alkali dissolution" is explained below:

in the last step of the preparation method, after hydrogen chloride solution is added into the mixed solution d to adjust the pH value to acidity, C16CA amphoteric groups can be deposited on the surfaces of the zinc oxide nano particles with the mesoporous silica modified surfaces and can be attached all the time, so that self-aggregation precipitation occurs, and the precipitation is the zinc oxide nano antibacterial compound. The zinc oxide nano antibacterial compound can be precipitated in an acidic solution environment and dissolved in an alkaline solution environment.

In addition, the mesoporous silica nanoparticles have larger specific surface area and larger pore volume, so that more zinc oxide nanoparticles can be wrapped to improve the sterilization efficiency, and the diffusion of sterilization factors released by the zinc oxide nanoparticles to the surrounding environment can be promoted to inhibit and kill microorganisms; the better biocompatibility and the lower toxicity do not affect the safety of the food.

Preferably, in the step (1), the weight ratio of the zinc acetate dihydrate, the ultrapure water and the hexadecyl trimethyl ammonium bromide is 3: 83-87: 0.25-0.35.

Preferably, in the step (2), the concentration of the sodium hydroxide solution is 0.7-0.9 mol/L.

Preferably, in the step (a), the concentration of the aqueous solution of the zinc oxide nano particles is 1-1.2 mg/mL; the weight ratio of the zinc oxide nano particles to the cetyl trimethyl ammonium bromide is 1: 3.8-4.2; the constant temperature is 43-47 ℃.

Preferably, in the step (b), the concentration of the methanol solution of tetraethyl orthosilicate is 10-12%.

Preferably, in the step (c), the concentration of the methanol solution of sodium chloride is 1-1.2%.

Preferably, in the step (iii), the weight ratio of the C16CA to the zinc oxide nanoparticles with surface modified mesoporous silica is 95-105: 1; the pH was adjusted to 8.

Preferably, in step (iv), the pH is adjusted to 4.

Based on the same technical concept, the invention further provides the zinc oxide nano antibacterial compound prepared by the method.

Preferably, the zinc oxide nano antibacterial compound is of a core-shell structure, the core layer is zinc oxide nano particles, and the shell layer is mesoporous silica and a C16CA group.

The invention has the beneficial effects that:

according to the preparation method of the zinc oxide nano antibacterial compound, mesoporous silicon dioxide is modified on the surface of the zinc oxide nano particles, so that the zinc oxide nano particles can play a bacteriostatic action, pollution caused by direct contact of the bacteriostatic core of the zinc oxide nano particles and grains is avoided, and more importantly, the designed amphiprotic group C16CA can enable the zinc oxide nano compound to have the characteristic of acid precipitation and alkali dissolution, and can be removed through rinsing, so that potential food safety hazards caused by the zinc oxide nano antibacterial compound are thoroughly eliminated.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is the chemical structural formula of C16ME according to the present invention.

FIG. 2 is the chemical structural formula of C16CA according to the present invention.

FIG. 3 is a graph showing the particle size distribution of the zinc oxide nanoparticles of the present invention.

Fig. 4 is a transmission electron microscope photograph of the zinc oxide nanocomposite according to the present invention.

Fig. 5 shows the state of the zinc oxide nanocomposite of the present invention at different pH values (a: pH 8; B: pH 4).

FIG. 6 is a graph showing the change in the total number of bacterial colonies on the surface of maize.

FIG. 7 is a graph of the change in the total number of fungal colonies on the surface of maize.

FIG. 8 is a graph of moisture content change during corn storage.

FIG. 9 is a graph showing the change in fatty acid values during storage of corn.

FIG. 10 is a graph of the change in germination vigor during corn storage.

FIG. 11 is a graph showing the change in germination rate during storage of corn.

FIG. 12 is a graph showing the change in the number of bacterial colonies on the surface of wheat.

FIG. 13 is a graph showing the change in the total number of fungal colonies on the surface of wheat.

FIG. 14 is a graph showing the change in moisture content during storage of wheat.

FIG. 15 is a graph showing the change in water absorption of wheat gluten.

FIG. 16 is a graph showing the variation of wheat drop.

FIG. 17 is a graph showing the change in the number of bacterial colonies on the surface of rice.

FIG. 18 is a graph showing the change in the total number of fungal colonies on the surface of rice.

FIG. 19 is a graph showing changes in moisture content during storage of rice.

FIG. 20 is a graph showing the change in roughness during the storage of rice.

FIG. 21 is a graph showing changes in fatty acid value during storage of rice.

FIG. 22 is a graph showing the change in the viability of rice during storage.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Example 1

(I) preparing zinc oxide nano particles:

(1) adding 3g of zinc acetate dihydrate into 85mL of ultrapure water, magnetically stirring for 15min, adding 0.3g of Cetyl Trimethyl Ammonium Bromide (CTAB), and magnetically stirring for 15min to obtain a mixed solution a;

(2) adding 75mL of 0.8mol/L sodium hydroxide solution into the mixed solution a, stirring at room temperature for reaction for 1h to obtain a white gelatinous solution, carrying out ultrasonic treatment for 15min, transferring the solution into a reaction kettle, standing at the constant temperature of 120 ℃ for 5h, centrifuging, washing and drying in vacuum the obtained precipitate to obtain zinc oxide nanoparticles;

(a) taking 100mg zinc oxide nanoparticles to be uniformly dispersed in 100mL aqueous solution by ultrasonic, adding 0.4g hexadecyl trimethyl ammonium bromide (CTAB) serving as a pore-foaming agent, and uniformly stirring at constant temperature of 45 ℃ to obtain a mixed solution b;

(b) dropwise adding 1.5mL of methanol solution of tetraethyl orthosilicate (TEOS) with the concentration of 10% into the mixed solution b, maintaining the constant temperature, continuously stirring for 90min, and repeating the dropwise adding operation once after the constant temperature is maintained to obtain mixed solution c;

(c) carrying out hydrothermal reaction on the mixed solution c at 120 ℃ for 24h, and washing out a pore-forming agent of hexadecyl trimethyl ammonium bromide by using a methanol solution of sodium chloride with the concentration of 1% after the hydrothermal reaction is finished, thus obtaining zinc oxide nanoparticles (ZnO-mMSNs) with mesoporous silica modified on the surface;

(III) surface amphiprotic group modification:

(i) continuously stirring 14.3g methyl acrylate and 2g hexadecyl ammonium in methanol solution at 40 deg.C for reacting for 72h, and removing methanol solvent and excessive methyl acrylate by rotary evaporation to obtainCompound (I)C16ME；

(ii) Stirring 3g of C16ME and 18ml of 1mol/L sodium hydroxide solution in methanol at room temperature for 24 hours for reaction, carrying out rotary evaporation to obtain a white solid, and washing with hexane and methanol to obtain an amphoteric compound C16 CA;

(iii) suspending C16CA and zinc oxide nanoparticles with mesoporous silica modified on the surface in an aqueous solution according to the concentration of 100:1, adjusting the pH to 8 by using 1mol/L sodium hydroxide solution, and stirring for 3 hours to uniformly disperse the system to obtain a mixed solution d;

(iv) and adding 1mol/L hydrogen chloride solution into the mixed solution d to adjust the pH to 4 to obtain suspension, and drying to obtain the zinc oxide nano compound.

For ease of understanding, the chemical structural formulas of compounds C16ME and C16CA are provided as shown in fig. 1 and fig. 2, respectively.

The particle size distribution of the zinc oxide nanoparticles obtained in step (I) is shown in fig. 3.

The transmission electron micrograph of the obtained zinc oxide nanocomposite is shown in fig. 4.

In order to verify the "acid precipitation and alkali dissolution" effect of the zinc oxide nanocomposite, the zinc oxide nanocomposite was placed in different pH environments, and the state thereof was observed, as shown in fig. 5.

Example 2 and example 3

Examples 2 and 3 are different from example 1 in the amount of part of raw materials used and the process of part of operations in the production process, and are specifically shown in table 1.

Table 1 amount of raw materials and operation process of example 2 and example 3

In order to verify the bacteriostatic effect of the zinc oxide nano-composite in the grain storage process, the following test is carried out.

(1) Bacteriostatic testing of the nanocomposites in corn storage.

The test method comprises the following steps: corn with water content of 12.03% and nano-composites (NPs) with different concentrations are mixed and stored, a control group sample without the addition of the nano-composites, an experimental group 1 with the addition of 100mg/kg (NPs-100mg/kg) and an experimental group 2 with the addition of 200mg/kg (NPs-200mg/kg) are prepared, 3 groups of corn samples are placed in a constant temperature and humidity incubator with the temperature of 35 ℃ and the relative humidity of 80% for storage, and sampling detection is carried out every 5 days during the storage period. The influence of the nanoparticles on the bacterial and fungal carrying capacity of the corn in the storage process and the change conditions of moisture, fatty acid value, germination potential and germination rate mainly related to the storage quality of the corn are mainly detected, and the results are as follows:

(1.1) Effect on bacterial load during storage

Referring to fig. 6, under the storage condition of 35 ℃ and 80% relative humidity, the total number of bacterial colonies on the surface of corn significantly increases (P <0.01) with the storage time after 30d of storage, and the total number of bacterial colonies of the control group is more significantly increased than that of the experimental group, and is more significantly inhibited with the increase of the addition concentration of the nano-composite. The result shows that the nano-composite has a certain inhibition effect on the growth of bacteria in the storage process of the corn, and the inhibition effect on the bacteria is more and more obvious along with the increase of the adding concentration and the prolonging of the storage time.

(1.2) influence on the amount of fungi carried in storage

Referring to fig. 7, under the storage condition of 35 ℃ and 80% relative humidity, the total number of the fungus colonies on the surface of the corn after 30 days of storage is relatively stable overall, the total number of the fungus colonies in the control group increases with the extension of the storage time, the total number of the fungus colonies on the surface of the corn after the addition of the nanocomposites with different concentrations in the experimental group is significantly lower than that in the control group (P <0.05), and the total number of the fungus colonies decreases with the increase of the addition concentration, which indicates that the nanocomposites also have a certain inhibitory effect on the fungus on the surface of the corn, and the bacteriostatic effect of the nanocomposites becomes more and more obvious with the extension of the storage time.

(1.3) influence on major quality index of corn

Referring to fig. 8, in this preliminary test, the initial corn moisture was 12.03%, and the corn moisture content in both the test group and the control group did not change significantly after 30 days of storage at a temperature of 35 ℃ and a relative humidity of 80%.

Referring to FIG. 9, under these storage conditions, the fatty acid number of corn increased somewhat from the initial 32.17(KOH)/(g/100g) to about 50(KOH)/(g/100g) with extended storage time, but still within the range of storage safety. The fatty acid values of the test group and the control group are in the same increasing trend, and the difference is not obvious.

Referring to fig. 10 and 11, from the results of the germination potential and germination rate index tests reflecting the viability of the corn seeds, the viability of the corn under the storage condition is relatively stable, the germination potential is about 35%, and the germination rate is about 80%. After the nano-composite is added, the vitality of the corn of the experimental group is increased compared with that of the control group, which is probably because the growth of microorganisms in the storage process of the corn is inhibited by the zinc oxide nano-composite, thereby protecting the integrity of the corn embryo and promoting the improvement of the germination rate.

The results are combined to show that the nano-composite can effectively inhibit the propagation of bacteria and fungi in the storage process of the corn, not only does not damage the related quality of the corn, but also improves certain quality indexes to a certain extent.

(2) Bacteriostatic test of the nano-composite in wheat storage.

The test method comprises the following steps: wheat with a water content of 10.41% and Nanocomposites (NPs) with different concentrations were mixed and stored to prepare a control sample without nanocomposite, an experimental group 1(NPs-100mg/kg) with an addition of 100mg/kg, and an experimental group 2(NPs-200mg/kg) with an addition of 200mg/kg, and 3 wheat samples were stored in a constant temperature and humidity incubator with a temperature of 35 ℃ and a relative humidity of 80% while sampling and detecting every 7 days. The influence on the total number of bacteria and fungus colonies on the surface of the wheat in the storage process and the change conditions of moisture, gluten water absorption and falling values influencing the quality index of the wheat are mainly detected, and the results are as follows:

(2.1) Effect on bacterial load during storage

Referring to fig. 12, the test results of 49 days of mixed storage of the nanocomposite and the wheat show that, in the early storage period (the sampling period of the first 21 days), the nanocomposite has little influence on the total number of bacteria on the surface of the wheat, and the total number of bacterial colonies in the experimental group and the control group are in a lower range, but the sampling result from the 28 th day shows that, compared with the experimental group, the total number of bacterial colonies on the surface of the wheat in the control group is obviously increased and obviously increased with the increase of the storage time, while the bacterial load on the surface of the wheat in the experimental group is not obviously increased and is always at a lower level, and the total number of bacterial colonies is also reduced with the increase of the storage time, because the total number of bacterial colonies in the experimental group is always at a lower level, even if the nanocomposite with a higher concentration is added, the difference of different concentrations is not large, indicating that the nanocomposite has an obvious bacteriostatic effect on the bacteria during the long-term storage of, and when the nano-composite is added at the concentration of 100mg/kg, the effect of obviously inhibiting the propagation of bacteria on the surface of the wheat is achieved.

(2.2) influence on the amount of fungi carried in storage

Referring to fig. 13, it was shown by monitoring the change of the total number of fungal colonies during storage that the nanocomposite had no significant effect on the total number of fungal colonies on the surface of wheat at the early stage of storage (during the first 21 days of the sampling period), but the results from the 28 th day of sampling showed that the total number of fungal colonies in the control group and the experimental group were significantly different, the total number of fungal colonies in the experimental group was significantly decreased, and the decreasing effect was more significant as the concentration of the added nanocomposite was increased, indicating that the nanocomposite had significant inhibitory effect on fungi during storage of wheat.

(2.3) influence on Main quality index of wheat

Referring to fig. 14, 15 and 16, three main indexes affecting wheat quality, namely moisture, gluten water absorption and a falling value, were continuously detected during a mixed storage period of 49 days of the nanocomposite and wheat. The results show that the difference between the experimental group and the control group in the three indexes is not obvious, which indicates that the addition of the nano-composite has no obvious difference influence on the main quality of the wheat in the storage process.

In conclusion, the nano-composite added in the storage process of wheat can effectively inhibit the growth of bacteria and fungi on the surface of wheat, and simultaneously cannot accelerate the deterioration of the quality of wheat.

(3) And (3) performing a bacteriostatic test on the nano-composite in rice storage.

The test method comprises the steps of mixing and storing paddy with the water content of 11.30% and Nanocomposites (NPs) with different concentrations, preparing a control group sample without the addition of the nanocomposites, an experimental group 1 with the addition of 100mg/kg (NPs-100mg/kg) and an experimental group 2 with the addition of 200mg/kg (NPs-200mg/kg), placing 3 groups of paddy samples in a constant-temperature and constant-humidity incubator with the temperature of 35 ℃ and the relative humidity of 80% for storage, and sampling and detecting every 6 days. The change of the total number of bacterial colonies and fungal colonies on the surface of the rice, which affect the main quality indexes of the rice, such as moisture, roughness, fatty acid value and viability, is mainly detected, and the results are as follows:

(3.1) Effect on bacterial load during storage

Referring to fig. 17, the rice was uniformly mixed with the nanocomposites of different concentrations, and simulated storage was performed for 40 days in an incubator at a temperature of 35 ℃ and a humidity of 85%. During storage, the total number of colonies in the control group increased significantly with the increase of storage time, and the total number of colonies in the test group was overall smooth and did not change much, wherein the increase of the total number of bacterial colonies was less significant with the increase of the concentration of the added nanocomposite. The addition of the nano-composite can obviously inhibit the growth of bacteria on the surface of the rice.

(3.2) influence on the amount of fungi carried in storage

Referring to FIG. 18, under the storage conditions, the total number of fungal colonies on the surface of the rice in the control group showed explosive growth from day 12, whereas the total number of colonies in the corresponding test group was relatively stable with substantially no significant change. The results show that the nano-composite can obviously inhibit the growth of fungi on the surface of the rice.

(3.3) influence on Main quality index of Rice

Referring to fig. 19, since the rice is stored in an environment of 85 ℃ temperature and 80% humidity, the initial moisture of the rice is low but slightly increased as the storage time increases. After 18 days, the moisture content of the rice tends to be stable because the rice is saturated with moisture and no longer absorbs external moisture. The paddy of the test group and the paddy of the control group have no significant difference in the moisture content in the same storage time, which indicates that the moisture content of the paddy is not affected by the addition of the nano-composite.

Referring to fig. 20, the high and low roughness of the rice reflects the excellent processing quality of the rice. The rice with high roughness yield has plump grains, less mildew and insect damage, high rice yield and high eating quality. Is one of the important indicators for evaluating the quality of rice. The roughness of the paddy rice in the test group and the control group is not obviously changed within 40 days of the storage under the storage condition, and the roughness of the paddy rice in the test group and the control group is not obviously different. The result shows that the roughness of the paddy can not be influenced after the nano compound is added, namely the edible value can not be influenced by changing the processing quality of the paddy.

Fat is one of the important components of rice, and unsaturated fatty acid in the fat is easy to be oxidized and hydrolyzed when the external environment is changed, so that the rice is rancid and the quality of the rice is reduced. The higher the fatty acid value of the rice, the less easy the rice is to be stored, and is one of the important measurement indexes for the storage quality of the rice.

Referring to fig. 21, as the fatty acid value of the rice in the control group increases with the increase of the storage time, the fatty acid value of the test group changes more smoothly, and the fatty acid value of the rice in the test group is significantly different from that of the control group, and the increase of the fatty acid value in the rice can be delayed as the addition concentration of the nanocomposite increases. The nano-composite is added, so that the fatty acid value of the rice can be improved to a certain degree, rancidity is slowed down, and the storage time of the rice is prolonged.

Viability refers to the potential ability of a seed to germinate and the vitality possessed by the seed embryo. By adopting the red tetrazole dyeing method, the vitality of the seeds is judged according to the color change quantity of the rice embryo parts, and the damage degree of rice germination can be reflected laterally.

Referring to fig. 22, the viability generally showed a tendency of increasing first and then decreasing, wherein the decrease of the viability of the rice in the control group was large, and the decrease of the viability of the test group was relatively most gradual. The rice viability of the test group and the control group is obviously different at the 24 th day, which shows that the addition of the nano-composite can protect the rice viability to a certain extent and reduce the damage of germination.

In summary, in the process of storing the rice, the added nano-composite can effectively inhibit the growth of bacteria and fungi, does not cause deterioration on main quality indexes of the rice, and has better influence on certain indexes.

The test results show that the prepared nano composite can obviously inhibit the growth of bacteria and fungi on the grain surface in the storage process of corn, wheat and rice, and the inhibition effect is more and more obvious along with the increase of the addition concentration of the nano particles. Meanwhile, compared with the control group, the main grain quality indexes of the test group are not reduced, and certain indexes are increased. The prepared nano-composite can be used in the storage process of grains and is used for inhibiting the propagation of microorganisms.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A preparation method of a zinc oxide nano antibacterial compound is characterized by comprising the following steps:

(I) preparing zinc oxide nano particles:

(III) surface amphiprotic group modification:

2. The preparation method of the zinc oxide nano antibacterial compound according to claim 1, wherein in the step (1), the weight ratio of the zinc acetate dihydrate, the ultrapure water and the hexadecyl trimethyl ammonium bromide is 3: 83-87: 0.25-0.35.

3. The method for preparing the zinc oxide nano bacteriostatic composite according to claim 1, wherein in the step (2), the concentration of the sodium hydroxide solution is 0.7-0.9 mol/L.

4. The preparation method of the zinc oxide nano bacteriostatic composite according to claim 1, wherein in the step (a), the concentration of the aqueous solution of the zinc oxide nano particles is 1-1.2 mg/mL; the weight ratio of the zinc oxide nano particles to the cetyl trimethyl ammonium bromide is 1: 3.8-4.2; the constant temperature is 43-47 ℃.

5. The method for preparing the zinc oxide nano bacteriostatic compound according to claim 1, wherein in the step (b), the concentration of the methanol solution of tetraethyl orthosilicate is 10-12%.

6. The method for preparing the zinc oxide nano bacteriostatic complex according to claim 1, wherein in the step (c), the concentration of the methanol solution of sodium chloride is 1-1.2%.

7. The preparation method of the zinc oxide nano antibacterial compound according to claim 1, wherein in the step (iii), the weight ratio of the C16CA to the zinc oxide nano particles with the surface modified with the mesoporous silica is 95-105: 1; the pH was adjusted to 8.

8. The method for preparing a zinc oxide nano bacteriostatic complex according to claim 1, wherein in step (iv), the pH is adjusted to 4.

9. The zinc oxide nano bacteriostatic complex prepared by the method of any one of claims 1 to 8.

10. The zinc oxide nano bacteriostatic composite of claim 9, which has a core-shell structure, wherein the core layer is zinc oxide nano particles, and the shell layer is mesoporous silica and a C16CA group.