Copper-doped nanorod-like polyaniline as well as synthesis method and antifouling application thereof

Abstract

The invention discloses copper-doped nanorod-like polyaniline as well as a synthesis method and antifouling application thereof, and belongs to the technical field of functional polymer composite materials. The synthesis method comprises the following steps: by taking ammonium persulfate (APS) as a main initiator and copper chloride as a secondary initiator, carrying out oxidative polymerization on aniline under an acidic condition to obtain acid-doped nanorod-like polyaniline (ES-PANI); sufficiently treating the ES-PANI by using an alkaline solution, and washing to obtain eigenstate polyaniline (EB-PANI); and further doping EB-PANI by adopting a solution of a protic-free solvent of copper salt to obtain the copper-doped nanorod-shaped polyaniline (Cu (at) PANI). The Cu-coated PANI prepared by the invention has excellent antibacterial property and can inhibit the growth of algae and marine pollutants such as barnacles, and the mechanism of the Cu-coated PANI is nano-knife effect, static electricity, oxidative stress and active chlorine synergistic antifouling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional polymer composites, in particular to a copper-doped nanorod-like polyaniline and a synthesis method and antifouling application thereof. BACKGROUND

[0002] Marine biofouling is caused by the attachment and growth of algae, shellfish and other organisms on the surface of underwater facilities such as ships, drilling platforms and aquaculture net cages, which can cause serious engineering problems and economic losses. The widely used antifouling technologies mainly include electrolytic seawater method, conductive coating method and antifouling coating, among which antifouling coating dominates due to its simple operation and cost-effectiveness.

[0003] Although traditional organotin antifouling agents have been widely used, they have been completely banned by international conventions due to their persistent accumulation in the marine environment, which can cause serious pollution to the marine ecological environment. Instead, copper-based antifouling agents (such as cuprous oxide) have become the market mainstream due to their broad-spectrum antibacterial properties and low cost. However, such materials have the problem of "burst release" of copper ions (Cu + ) at the initial stage of coating use, which can cause heavy metal pollution to harbors and aquaculture areas in the long run, and has poor biocompatibility. Therefore, the development of new antifouling materials with high efficiency and low toxicity to minimize environmental impact while ensuring antifouling effect has become a core challenge in the field of marine engineering materials.

[0004] As an intrinsic conductive polymer, polyaniline (PANI) has great potential in the field of antifouling due to its unique molecular structure and controllable redox properties, such as adjusting the microenvironment of metal surfaces through redox reactions to delay biofilm formation. The present application unexpectedly found that the antifouling performance of PANI can be further enhanced when its microstructure is designed as a nanorod structure. This is mainly based on its high specific surface area and interface effect, and the nanorod surface is rich in amine / imine groups, which is easy to be doped with metal ions (such as Cu 2+ ), to achieve long-term biological interference through oxidative stress antifouling mechanism. The copper-doped nanorod-like polyaniline (Cu@PANI) provided by the present application not only has high antibacterial effect on negative bacteria (such as Escherichia coli) and positive bacteria (such as Staphylococcus aureus), but also has very excellent growth inhibition effect on algae and barnacles and other typical marine fouling organisms. It has a wide application prospect, such as developing alternative cuprous oxide ship antifouling coatings, underwater facility protection (such as sensors) and aquaculture facility coatings, promoting the development of marine antifouling technology towards high efficiency and low environmental impact, and meeting the requirements of green marine economy. SUMMARY

[0005] The technical problem solved by the present application is: in view of the problem of how to develop a new type of efficient and low-toxicity antifouling material in the prior art, while ensuring the antibacterial, algal and antifouling effects, and minimizing the environmental load, the present application provides a copper-doped nanorod-shaped polyaniline and a synthesis method and antifouling application thereof, which has a nanoknife effect, static electricity, oxidative stress and active chlorine generation synergistic mechanism for antibacterial and antifouling, and provides a new material for replacing environmentally unfriendly antibacterial and antifouling agents.

[0006] Technical scheme: The first object of the present application is to provide a synthesis method of copper-doped nanorod-shaped polyaniline, characterized by the following steps:

[0007] Step one: ammonium persulfate and copper chloride are used as initiators to cause the oxidation polymerization of aniline under acidic conditions to obtain acid-doped nanorod-shaped polyaniline (ES-PANI);

[0008] Step two: the acid-doped polyaniline in step one is de-acid-doped with an alkali solution to obtain intrinsic-state polyaniline (EB-PANI);

[0009] Step three: the intrinsic-state polyaniline in step two is placed in a copper salt solution using an aprotic solvent, centrifuged, filtered and dried to obtain copper-doped nanorod-shaped polyaniline (Cu@PANI).

[0010] The present application uses two initiators, copper chloride and ammonium persulfate, to adjust the polyaniline into a nanorod shape, polymerizes aniline through the two initiators to generate nanorod-shaped acid-doped polyaniline, and then reacts in an alkaline solution until it is neutral to obtain intrinsic-state polyaniline. Finally, the intrinsic-state polyaniline is placed in a copper salt aprotic solvent solution to react to obtain nanorod-shaped copper-doped polyaniline. The product not only has a high antibacterial effect on negative bacteria (such as E. coli) and positive bacteria (such as Staphylococcus aureus), but also has a very excellent growth inhibition effect on algae and typical marine fouling organisms such as barnacles. It has a nanoknife effect, static electricity, oxidative stress and active chlorine generation synergistic mechanism for antibacterial and antifouling, and can promote the development of environmentally friendly marine antifouling technology.

[0011] As a preferred embodiment, the total amount of initiator in step one is equal to the amount of aniline, and the amount of copper chloride accounts for 5% to 10% of the amount of aniline. When the amount of initiator copper chloride exceeds 10% of the amount of aniline, such as 20%, the obtained polyaniline morphology is nanospheres; and when it is less than 5% of the amount of aniline, irregular morphology is obtained.

[0012] As preferred, the aniline is oxidized and polymerized in step one under acidic condition with ammonium persulfate and copper chloride as initiators, and the specific conditions are as follows: the aniline is taken in a dry beaker, and an inorganic acid aqueous solution is added thereto, and after stirring to form aniline salt solution, the solution is transferred to a three-necked flask equipped with a stirrer and a dropping funnel; the initiators are dissolved in distilled water; the three-necked flask is placed in an ice water bath, and when the temperature is lower than 5℃, the initiator solution is added through a constant pressure funnel within 30 minutes, and after maintaining the reaction temperature for 8-12 hours, centrifugation is performed, and the product is washed with distilled water and ethanol alternately for three times, and dried in a vacuum oven at 80℃ for 24 hours to obtain acid-doped nanorod-like polyaniline.

[0013] As preferred, the inorganic acid is at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0014] As preferred, the base solution in step two is sodium hydroxide or aqueous ammonia solution.

[0015] As preferred, the copper salt solution in step three is at least one of copper chloride, copper nitrate and copper sulfate solution, and the aprotic solvent is at least one of acetone and acetonitrile. If a protic solvent (such as water or ethanol) is used, the final prepared copper-doped nanorod-like polyaniline cannot achieve the complete reduction of divalent copper to monovalent copper combined with polyaniline, thereby weakening its antibacterial and antifouling effect.

[0016] As preferred, the doping amount of copper salt in step three is 15-22% of the mass fraction of Cu relative to the intrinsic polyaniline.

[0017] The second object of the present application is to provide a copper-doped nanorod-like polyaniline synthesized based on the above method.

[0018] The third object of the present application is to provide the use of the above copper-doped nanorod-like polyaniline as an antibacterial, algal inhibiting and marine antifouling material.

[0019] As preferred, the antibacterial, algal inhibiting and marine antifouling material is a copper-doped nanorod-like polyaniline suspension or a copper-doped nanorod-like polyaniline coating.

[0020] Advantages:

[0021] (1) High loading amount of copper. The doping amount of the copper-doped nanorod-like polyaniline (Cu@PANI) prepared in the present application is as high as 21.8 wt%. This is due to the fact that EB-PANI can be combined with copper ions through charge transfer and coordination mechanism in organic solvents. The Cu@PANI prepared in the present application mainly exists in the form of Cu + which is stable. This structure endows the Cu@PANI with the ability to directly oxidize and stress the microorganisms such as bacteria, and the electrostatic interaction antibacterial mechanism, thereby achieving excellent antifouling effect.

[0022] (2) Compared with the template effect of the surfactant and the addition of the solvent to regulate the morphology of polyaniline, the concentration of anhydrous copper chloride is changed to regulate the morphology of polyaniline, which has the characteristics of simple operation and easy purification; the obtained nanorod-like polyaniline has a nanoknife effect for antibacterial and antifouling.

[0023] (3) The copper-doped nanorod-like polyaniline has active chlorine generation activity in a simulated marine environment. This is due to the ROS activity of Cu@PANI, which can effectively oxidize chloride ions into active chlorine (such as hypochlorous acid chlorine), and excellent antibacterial and antifouling effects are obtained.

[0024] (4) Cu@PANI has a four-fold synergistic antibacterial and antifouling mechanism of nanoknife effect, electrostatic effect, oxidative stress and active chlorine generation.

[0025] (5) The Cu@PANI material provided by the present application can be used as a suspension and can also be used as a copper-doped nanorod-like polyaniline coating, which has a significant effect as an antibacterial, algal inhibiting and marine antifouling material. Through experiments, the Cu@PANI material prepared by the present application not only has a high antibacterial effect on negative bacteria (such as Escherichia coli) and positive bacteria (such as Staphylococcus aureus), but also can completely inhibit the growth of Escherichia coli and Staphylococcus aureus at a concentration of 2 µg / mL and 4 µg / mL, respectively. Similarly, a polybutylal (PVB) coating containing 0.5wt% Cu@PANI can also achieve a 100% inhibition effect on the growth of Escherichia coli. It also has excellent algal growth inhibition effect, and the coating layer reduces the content of chlorophyll by at least 92.5% compared with the PVB coating without adding the coating layer, showing very excellent algal growth inhibition effect. The coating layer coated on the carbon steel plate does not have any algae adhesion after being soaked in an algae-containing fish tank for 21 days, and the concentration of algae in the fish tank is significantly reduced, which again proves the anti-algal growth activity of Cu@PANI in the coating layer. At the same time, through 6 months of marine hanging plate test, the PBV coating sample containing 1.0 wt% Cu@PANI does not have any marine fouling adhesion on the surface of the sample plate, showing very excellent anti-marine fouling adhesion activity. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0027] Figure 1FT-IR spectra of ES-PANI, EB-PANI, Cu@PANI in Example 1;

[0028] Figure 2 TEM morphology of acid-doped nanorod-like polyaniline in Example 1 and Example 2, (a) is ES-PANI-5, (b) is ES-PANI-10;

[0029] Figure 3 Antibacterial effect of the suspension, (a) against E. coli, (b) against S. aureus;

[0030] Figure 4 Antibacterial effect of PVB coating with 0.5wt% Cu@PANI;

[0031] Figure 5 Algae growth test results of PVB coating with 0.5wt% Cu@PANI, (a) is Cu@PANI-5, (b) is Cu@PANI-10;

[0032] Figure 6 Photos of marine hanging plate before and after adding 1wt% Cu@PANI PVB coating. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0034] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0035] Unless otherwise specified, the raw materials used in the embodiments of the present application are all from ordinary commercially available products.

[0036] Example 1

[0037] A solution of aniline salt was prepared by stirring 1.86 g of aniline (0.02 mol) and 70 mL of 1 M sulfuric acid solution in a 100 mL beaker and then transferring to a three-necked flask equipped with a stirrer and a dropping funnel. An initiator of ammonium persulfate (0.018 mol) and anhydrous copper chloride (0.002 mol) were dissolved in 30 mL of distilled water. When the temperature of the three-necked flask was reduced to below 5°C in an ice-water bath, the initiator solution was added through a constant pressure funnel in 30 minutes, and the polymerization was continued for 8 h at this reaction temperature. The product was centrifuged, washed three times with distilled water and ethanol alternately, and dried in a vacuum oven at 80°C for 24 h to obtain acid-doped nanorod-like polyaniline ES-PANI (named as ES-PANI-10 in this example). The ES-PANI-10 (0.93 g) was placed in 30 mL of 0.1 mol / L sodium hydroxide solution and reacted under magnetic stirring for 2 h until the pH of the system reached 7 to completely remove the protons in the ES-PANI. The product was washed with deionized water and dried in a vacuum drying oven at 80°C for 24 h to obtain the intrinsic state polyaniline EB-PANI (named as EB-PANI-10 in this example).

[0038] A solution of aniline salt was prepared by stirring 1.86 g of aniline (0.02 mol) and 70 mL of 1 M sulfuric acid solution in a 100 mL beaker and then transferring to a three-necked flask equipped with a stirrer and a dropping funnel. An initiator of ammonium persulfate (0.018 mol) and anhydrous copper chloride (0.002 mol) were dissolved in 30 mL of distilled water. When the temperature of the three-necked flask was reduced to below 5°C in an ice-water bath, the initiator solution was added through a constant pressure funnel in 30 minutes, and the polymerization was continued for 8 h at this reaction temperature. The product was centrifuged, washed three times with distilled water and ethanol alternately, and dried in a vacuum oven at 80°C for 24 h to obtain acid-doped nanorod-like polyaniline ES-PANI (named as ES-PANI-10 in this example). The ES-PANI-10 (0.93 g) was placed in 30 mL of 0.1 mol / L sodium hydroxide solution and reacted under magnetic stirring for 2 h until the pH of the system reached 7 to completely remove the protons in the ES-PANI. The product was washed with deionized water and dried in a vacuum drying oven at 80°C for 24 h to obtain the intrinsic state polyaniline EB-PANI (named as EB-PANI-10 in this example).

[0039] The structures of ES-PANI, EB-PANI and Cu@PANI were characterized by FT-IR, the morphology of ES-PANI sample was observed by transmission electron microscopy (TEM), and the conductivity of Cu@PANI was tested by four-probe method.

[0040] Figure 1 The FT-IR spectra of ES-PANI, EB-PANI and Cu@PANI are shown. Compared with EB-PANI, the C=C stretching vibration absorption peak of benzene ring structure in Cu@PANI is obviously weakened, which indicates that the ratio of quinone / benzene changes during copper doping. This is because the copper chloride with oxidation activity oxidizes part of the benzene structure to quinone structure, and the Cu 2+ is reduced to Cu + . Similar to ES-PANI, the C=C stretching vibration absorption peak of benzene ring structure in EB-PANI is about 795 cm -1The characteristic peaks correspond to the out-of-plane C-H bending vibration of benzene ring, which proves the successful synthesis of Cu-doped PANI.

[0041] Example 2

[0042] Compared with Example 1, the amount of initiator ammonium persulfate was adjusted to 0.019 mol, and the amount of anhydrous copper chloride was adjusted to 0.001 mol. The prepared copper-doped nanorod-like polyaniline was named Cu@PANI-5.

[0043] Figure 2 It can be seen that the copper-doped polyaniline synthesized by the application is nanorod-like, and the nanorods of Cu@PANI-10 are longer than those of Cu@PANI-5, which is mainly because the increase of the concentration of anhydrous copper chloride relatively reduces the generation rate of PANI, which is beneficial to the generation of rod-like morphology with larger length-diameter ratio.

[0044] Example 3

[0045] Compared with Example 1, after the synthesis of EB-PANI, acetonitrile was used as the solvent when preparing the copper salt solution, and 0.2208 g of anhydrous copper nitrate was added.

[0046] Application Example

[0047] 1. Antibacterial performance of Cu@PANI suspension

[0048] LB broth liquid medium (500 mL) was prepared and autoclaved for 20 min. Solid medium was additionally added with 7.5 g of agar and stored at 4℃ after sterilization. The frozen E. coli was inoculated in the medium and cultured at 37℃ for 14 h, and the concentration of the bacterial solution was adjusted to 10 5 CFU / mL. In the 96-well plate, Cu@PANI aqueous dispersion (initial concentration 64 μg / mL) was gradiently diluted to 1 μg / mL by using double dilution method, 100 μL of bacterial solution (10 5 CFU / mL) was added to each well, and the control group only contained the same amount of bacterial solution. The 96-well plate was placed in a constant temperature incubator for 24 h, 50 μL of the above bacterial solution was taken to LB solid culture plate, and the plate was cultured in a constant temperature incubator at 37℃ for 24 h. According to the number of bacteria, the minimum antibacterial concentration of Cu@PANI suspension on E. coli was obtained, and the minimum antibacterial concentration of Cu@PANI on Staphylococcus aureus was tested in the same way, wherein the concentration of Cu@PANI suspension added to the first well of the 96-well plate was 8 μg / mL. The Staphylococcus aureus and E. coli samples used in the experiment were provided by the College of Veterinary Medicine of Yangzhou University.

[0049] Figure 3The antibacterial effect of Cu@PANI suspension concentration on bacterial growth was shown, and the complete inhibition concentration of Cu@PANI-5 and Cu@PANI-10 on E. coli and S. aureus was 2 μg / mL and 4 μg / mL, respectively. Compared with acid-doped polyaniline (ES-PANI-10), the antibacterial activity of Cu@PANI-10 on S. aureus was significantly enhanced.

[0050] 2. Antibacterial performance of Cu@PANI coating

[0051] Preparation of Cu@PANI / PVB coating sample: First, prepare an ethanol suspension of Cu@PANI with a mass concentration of 10%; then prepare a polyvinyl butyral (PVB) anhydrous ethanol solution with a mass concentration of 20%; then prepare a Cu@PANI / PVB coating with a Cu@PANI solid mass concentration of 0.5%. The above Cu@PANI / PVB coating is coated on a non-woven fabric, and a wet film with a thickness of 50 μm is prepared by a doctor blade coating method, and is naturally air-dried for 6 h to obtain a Cu@PANI / PVB non-woven fabric coating sample with a coating thickness of ~10 μm.

[0052] The antibacterial test was carried out according to the method of GB / T 31402-2015.

[0053] Figure 4 The antibacterial effect of the coating was shown. Compared with the blank sample, the nanocomposite coating containing only 0.5 wt% Cu@PANI-5 or Cu@PANI-10 showed 100% inhibition effect on E. coli. It showed that Cu@PANI was a highly efficient antibacterial nanomaterial.

[0054] 3. Algae killing test of Cu@PANI coating

[0055] The copper-doped nanorod polyaniline prepared in Example 1 and Example 2 was added to the PVB coating at a mass concentration of 0.5% (preparation method as above) to obtain a nanocomposite coating@non-woven fabric. The non-woven fabric coated with the coating was cut into a size of 2×2 cm 2 , immersed in 5 mL of Chlorella culture solution with a concentration of 10 7 CFU / mL, cultured in an incubator for 24 h, and the chlorophyll in the Chlorella in the non-woven fabric was extracted by 95% ethanol solution, and the content of chlorophyll was detected by spectrophotometry to determine the inhibition effect of the coating on the growth of algae.

[0056] Table 1. Test results of 0.5 wt% Cu@PANI coating@non-woven fabric on inhibition of algae growth

[0057]

[0058] The results are shown in Table 1, the chlorophyll content of the prepared Cu@PANI-5, Cu@PANI-10 nanocomposite coating is reduced by 95.0%, 92.5% respectively compared with the PVB coating without adding Cu@PANI, showing very excellent effect of inhibiting the growth of algae. This is related to the oxidative stress mechanism of Cu@PANI.

[0059] 4. Anti-algal growth of Cu@PANI coating

[0060] Figure 5 is the photo of the carbon steel plate coated with PVB nanocomposite coating added with 0.5 wt% Cu@PANI (the coating method is the same as above, except that the non-woven fabric is replaced by a carbon steel plate) after being immersed in the algae-containing fish tank for 21 days. The results show that the surfaces of the PVB nanocomposite coatings of Cu@PANI-5 and Cu@PANI-10 are free of algae adhesion, and the concentration of algae in the fish tank is significantly reduced (the color of the algae-containing liquid in the fish tank is significantly lighter than that when just immersed), which again proves the anti-algal growth activity of Cu@PANI in the coating.

[0061] 5. Marine hanging plate test:

[0062] Figure 6 is the comparison photo of the carbon steel plate coated with PVB nanocomposite coating added with 1.0 wt% Cu@PANI (the coating method is the same as above) before and after being hung in the sea area of Fujian for 6 months (May-October). The results show that after 6 months of marine environment hanging plate test, no marine fouling organisms adhere to the surface of the coating, showing very excellent anti-marine fouling adhesion activity.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions described in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for synthesizing copper-doped nanorod-like polyaniline, characterized in that, The steps are as follows: Step one, ammonium persulfate and copper chloride are used as initiators to make aniline undergo oxidative polymerization under acidic conditions to obtain acid-doped nanorod-like polyaniline; Step two, the acid-doped polyaniline in step one is de-acid-doped with an alkali solution to obtain intrinsic state polyaniline; Step three, the intrinsic state polyaniline in step two is placed in a copper salt solution using an aprotic solvent, centrifuged, filtered, and dried to obtain copper-doped nanorod-like polyaniline.

2. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 1, characterized in that, In step one, the total amount of initiator is equal to that of aniline, and the amount of copper chloride accounts for 5-10% of the amount of aniline.

3. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 1, characterized in that, In step one, ammonium persulfate and copper chloride are used as initiators to make aniline undergo oxidative polymerization under acidic conditions, and the specific conditions are as follows: aniline is taken in a dry beaker, inorganic acid aqueous solution is added, and after stirring to form aniline salt solution, it is transferred to a three-necked flask equipped with a stirrer and a dropping funnel; the initiator is dissolved in distilled water; the three-necked flask is placed in an ice water bath, and when the temperature is lower than 5℃, the initiator solution is added through a constant pressure funnel within 30 minutes, the reaction temperature is maintained, and the polymerization is continued for 8-12 hours; then, centrifugation is performed, and the product is washed with distilled water and ethanol alternately for three times, and dried in a vacuum oven at 80℃ for 24 hours to obtain acid-doped nanorod-like polyaniline.

4. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 3, characterized in that, The inorganic acid is at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

5. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 1, characterized in that, The alkali solution in step two is sodium hydroxide or ammonia solution.

6. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 1, characterized in that, The copper salt solution in step three is at least one of copper chloride, copper nitrate, and copper sulfate solution, and the aprotic solvent is at least one of acetone and acetonitrile.

7. The method for synthesizing copper-doped nanorod-shaped polyaniline according to claim 1, characterized in that, The doping amount of copper salt in step three is 15-22% of the mass fraction of Cu relative to the intrinsic state polyaniline.

8. A copper-doped nanorod-like polyaniline synthesized based on the method of any one of claims 1-7.

9. The use of the copper-doped nanorod-like polyaniline of claim 8 as an antibacterial, algal inhibiting, and marine antifouling material.

10. Use according to claim 9, characterized in that, The antibacterial, algal inhibiting, and marine antifouling material is a suspension containing copper-doped nanorod-like polyaniline or a coating containing copper-doped nanorod-like polyaniline.

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