CN115110127B - Hydrophobic bright silver film for inhibiting microbial dirt adhesion growth and preparation method thereof - Google Patents

Abstract

The present invention relates to the technical field of inhibiting the adhesion and growth of microbial dirt, and specifically provides a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt and a preparation method thereof. The film is a super-hydrophobic and bright silver film obtained by electroplating silver. Since silver has the ability to kill bacteria, the total amount of extracellular secretions of microbial dirt is reduced, the structure is hollowed out, and the protein is denatured, so that the overall growth of dirt is slow, thereby inhibiting the initial adhesion and growth of microorganisms on the surface of the silver film, forming a scale inhibition effect. On the surface of the bright silver film, the adhesion of microbial dirt on the surface decreases, thereby reducing the adhesion of microbial dirt. As the hydrophobicity of the surface of the silver film increases, the adhesion of microorganisms is further reduced. Based on these synergistic effects, the super-hydrophobic bright silver film prepared by the present invention can effectively inhibit the growth of microbial dirt and the adhesion on its surface.

Description

Hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt and its preparation method

Technical Field

The present invention belongs to the technical field of inhibiting the attachment and growth of microbial dirt, and is used to prevent the attachment of microorganisms to flow restrictors and heat exchangers, which may cause the flow restrictors and heat exchangers to lose control, and to prevent the microbial corrosion of metals in other applications such as seawater and urban water pipe networks. Specifically, a hydrophobic bright silver film for inhibiting the attachment and growth of microbial dirt and a preparation method thereof are provided.

Background technique

There are a large number of microorganisms in the natural water environment. In long-term use, the attachment of microorganisms will cause pollution in the water circulation network and loss of control of the flow controller on the water network; attachment on the circulating condenser will cause the failure of the heat exchanger. Similarly, attachment on the metal wall will also cause the decline of water environment quality in the urban pipe network and metal corrosion. Especially at the moment when my country is vigorously developing marine resources, it is necessary to inhibit the attachment of microbial dirt and prevent microbial metal corrosion in the marine environment.

In water bodies, the formation of microbial fouling is divided into several stages. It is crucial to clarify the formation of microbial fouling to inhibit the attachment and growth of microbial fouling. The early stage of microbial fouling formation is the stage of microbial attachment and biofilm formation. The microbial attachment process in water environments includes four stages: bacterial initial adhesion, biofilm adhesion period, growth period, maturity and peeling period. First, organic molecules and a small amount of bacteria adhere to the surface of the substrate, and adhere under chemical bonding, electrostatic action, mechanical linkage or diffusion. They will also fall off from the surface of the substrate under the action of peeling, plane shearing, non-plane shearing, etc. Therefore, this is the reversible attachment stage. At this time, microorganisms use the polymers they secrete to firmly adhere to the surface and enter the irreversible attachment stage. After irreversible attachment, the biofilm continues to grow and reaches the maturity and peeling period after several days or weeks. The attachment and fixation of microorganisms on the surface of the material is a very complex dynamic process, which is affected by many factors. Studies have shown that the amount of microbial attachment is related to the nature of the material (the toxicity of the material to microorganisms); and as the surface roughness of the material increases, the amount of microbial fouling increases; at the same time, it is positively correlated with the hydrophobicity of the material surface.

So far, many studies have used silver or cuprous oxide as materials to inhibit the attachment and growth of microorganisms, such as silver film or nano cuprous oxide. The principle is to use its ability to kill bacteria, reduce the total amount of extracellular secretions of microbial dirt, hollow out the structure, and denature the protein, causing the overall growth of dirt to slow down. This can inhibit the initial adhesion and growth of microorganisms on the surface, forming a scale inhibition effect. There are also methods that modify the metal surface with silane coupling agents to form a hydrophobic structure on the surface to achieve the purpose of inhibiting the attachment and growth of microbial dirt. Judging from the effects currently used, no matter which method is used, the effect of inhibiting the attachment and growth of microorganisms is not very ideal.

Summary of the invention

In order to solve the problems such as blockage of flow controller, insulation of heat exchanger and metal corrosion caused by microorganisms caused by the attachment of microbial dirt in water system, the present invention combines the bactericidal effect of silver film with the bright surface silver film on which microorganisms are difficult to attach, and provides a hydrophobic bright silver film for inhibiting the attachment and growth of microbial dirt and a preparation method thereof.

In order to evaluate the ability of super-hydrophobic bright silver film to inhibit the attachment and growth of microbial pollutants, we selected 304 stainless steel as the substrate (of course, in addition to 304 stainless steel substrate, it can also be other substrates with metal surfaces), and electro-deposited super-hydrophobic bright silver film on its surface. In order to obtain a silver film with good adhesion strength, the substrate was pre-treated with electroplating copper before the electro-deposited silver film. The preparation method of super-hydrophobic bright silver film is to adopt the method of electrodeposition. The basic solution of silver electrodeposition is composed of silver nitrate as the main salt, succinimide as the complexing agent, and potassium pyrophosphate as the conductive salt. The concentration range of silver nitrate is 10-100g/L. When the concentration is lower than 10g/L, the quality of the electro-deposited silver film decreases due to the low concentration. When the concentration is greater than 100g/L, the obtained silver film becomes loose due to the high concentration. The optimal concentration range of silver nitrate is 30-60g/L. The optimal concentration range of the complexing agent succinimide is 50-100 g/L, and the concentration range of the conductive salt potassium pyrophosphate is 50-120 g/L. Undoubtedly, for the conductive salt and the complexing agent, other commonly used reagents in the field of electrodeposition can also be selected, but for the brightener of the present invention, potassium pyrophosphate and succinimide are the best combination.

In order to obtain a stable silver electrodeposition solution, the pH of the silver electrodeposition solution is controlled between 8 and 11. For example, KOH or NaOH may be used to adjust the pH of the silver electrodeposition solution.

The operating temperature range of the silver electrodeposition solution is relatively wide and can be set between 10 and 50° C., and the current density range is 0.1 to 2 A/dm ² .

In order to obtain a bright silver film, a brightener of 5-methylhydantoin or its derivatives is added to the silver electrodeposition solution. The concentration of the brightener ranges from 5 to 30 g/L, and the optimal concentration range is 10 to 20 g/L. Not only 5-methylhydantoin can be used as a brightener for silver electrodeposition, but some of its derivatives also have good brightener effects. The structural formula of its derivatives is wherein R ₁ ＝H or CH ₃ ; R ₂ ＝H, CH ₃ , Cl or Br; R ₃ ＝H, CH ₃ , Cl or Br.

In order to be more conducive to inhibiting the attachment and growth of microbial pollutants, silver particles with a particle size of about 20-800nm are added to the above-mentioned silver electrodeposition solution to obtain a super-hydrophobic and bright silver film. Undoubtedly, within a certain range, the smaller the particle size of the silver particles, the better, but the silver particles with very small particles bring about a sharp increase in cost. When the silver particles are larger, ultrasonic vibration is used to uniformly composite-electrodeposit the silver particles into the silver film. The present invention combines the bactericidal effect of the silver film with the bright and hydrophobic surface silver film to which microorganisms are difficult to attach, and obtains a silver film with both the necessary bright characteristics and the super-hydrophobic effect, thereby being able to better inhibit the attachment and growth of microbial dirt.

Compared with the prior art, the present invention has achieved the following beneficial effects: the present invention combines the bactericidal effect of the silver film with the bright surface silver film on which microorganisms are difficult to adhere, and provides a super hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt. The film is a hydrophobic and bright silver film obtained by electroplating silver. Since silver has the ability to kill bacteria, the total amount of extracellular secretions of microbial dirt is reduced, the structure is hollowed out, and the protein is denatured, so that the overall growth of dirt is slow, thereby inhibiting the initial adhesion and growth of microorganisms on the surface of the silver film, forming a scale inhibition effect. On the surface of the bright silver film, the adhesion of microbial dirt on the surface is reduced, thereby reducing the adhesion of microbial dirt. As the hydrophobicity of the silver film surface increases, the adhesion of microorganisms is further reduced. Based on these synergistic effects, the hydrophobic bright silver film prepared by the present invention can effectively inhibit the growth of microbial dirt and the attachment on its surface. During the 108h adsorption cycle, the inhibition effect of microbial attachment and growth can be increased by about 31% compared with not adding a brightener.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of the electrodeposited silver film, wherein A is without 5-methylhydantoin; and B is 15 g/L 5-methylhydantoin.

Figure 2 is a SEM image after adding 500nm silver particles.

Fig. 3 Contact angle of electrodeposited silver films under different conditions.

Detailed ways

The present invention is further described below in conjunction with the following examples. The examples provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

In order to effectively illustrate the effect of the present invention, a 304 stainless steel sheet of 1.5x4cm (thickness 0.5mm) was first prepared, and after alkali washing and degreasing, a copper plating treatment was performed on the surface, and then the sheet was placed in a silver-based plating solution (silver nitrate, succinimide, potassium pyrophosphate, and the pH of the solution was adjusted with KOH) for electrodeposition. The electrodeposition condition was 30°C. If a bright silver film is required, 5-methylhydantoin or its derivatives can be added to the above solution. All can obtain the performance equivalent to 5-methylhydantoin, and the following specific examples will not be proved one by one. Further, if a super-hydrophobic bright silver film is needed, nano silver particles can be added to the above silver solution. If nano silver particles are added without adding a brightener, the surface of the obtained substrate will show the defects of roughness and poor hydrophobicity, and microbial attachment and growth cannot be well inhibited.

In order to evaluate the ability of super-hydrophobic bright silver film to inhibit the attachment and growth of microbial pollutants, the cultured iron bacteria were prepared into a diluted bacterial suspension at a ratio of 1:100 and placed in different beakers. The test pieces were vertically suspended in beakers containing the cultured iron bacteria solution, and the beakers were placed in a 30°C simulated heating environment. The microbial fouling experiment cycle was 108h. The mass of the sample before and after the experiment was weighed using an electronic analytical balance to measure the amount of microbial pollutants attached to the sample. In order to evaluate the ability of super-hydrophobic bright silver film to inhibit the attachment and growth of microbial pollutants, experimental iron bacteria were cultured. First, the prepared culture medium was sterilized in a high-pressure steam autoclave at 0.1Mp and 120°C for 20min. After the culture medium was cooled in a clean bench, it was sterilized with a UV lamp for 15min. Take 10ml of the strain with an inoculation gun, the inoculation amount is 1%, inoculate to 1 000ml of the culture medium, and culture at 30°C in a constant temperature incubator for 72h.

The following are specific examples. The claims of the present invention are not limited to the reaction conditions and raw material concentrations listed in the following examples.

Example 1

A 304 stainless steel sheet of 1.5x4cm (0.5mm thick) after degreasing and pre-copper plating was placed in an electroplating solution of 10g/L silver nitrate, 50g/L succinimide and 60g/L potassium pyrophosphate. The pH of the solution was adjusted to 8 with KOH. At 25°C, a current density of 0.3A/dm ² was applied for an electroplating time of 30min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution. The experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 1 in Table 1.

Example 2

A 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating was placed in an electroplating solution of 45g/L silver nitrate, 50g/L succinimide, 60g/L potassium pyrophosphate and 15g/L 5-methylhydantoin. The pH of the solution was adjusted to 10 with KOH. At 25°C, a current density of 0.3A/dm ² was applied for an electroplating time of 30min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution. The experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 2 in Table 1.

Example 3

A 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating was placed in an electroplating solution of 45g/L silver nitrate, 50g/L succinimide, 60g/L potassium pyrophosphate, 15g/L 5-methylhydantoin and 3g/L 500nm silver powder. The pH of the solution was adjusted to 10 with KOH. Under ultrasonic irradiation and 25°C, a current density of 0.3A/dm ² was applied for an electroplating time of 30min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution. The experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 3 in Table 1. It can be seen that there is almost no iron bacteria microbial contaminant attached to the test piece.

Example 4

A 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating was placed in an electroplating solution of 60g/L silver nitrate, 70g/L succinimide, 100g/L potassium pyrophosphate, 15g/L 5,5-dimethylhydantoin and 3g/L 500nm silver powder. The pH of the solution was adjusted to 10 with KOH. Under ultrasonic irradiation and 25°C, a current density of 0.3A/dm ² was applied for an electroplating time of 30min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution, and the experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 4 in Table 1. It can be seen that there is almost no iron bacteria microbial contaminant attached to the test piece.

Example 5

A 304 stainless steel sheet of 1.5x4cm (0.5mm thick) after degreasing and pre-copper plating was placed in an electroplating solution of 100g/L silver nitrate, 100g/L succinimide, 120g/L potassium pyrophosphate, 5g/L 3-bromo-1-chloro-5,5-dimethylhydantoin and 2g/L 300nm silver powder. The pH of the solution was adjusted to 10 with KOH. Under ultrasonic irradiation and 25°C, a current density of 0.6A/dm ² was applied for an electroplating time of 15min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution, and the experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 5 in Table 1. It can be seen that there is almost no iron bacteria microbial contaminant attached to the test piece.

Example 6

A 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating was placed in an electroplating solution of 45g/L silver nitrate, 50g/L succinimide, 60g/L potassium pyrophosphate, 20g/L 1,3-dichloro-5-methylhydantoin and 2g/L 800nm silver powder. The pH of the solution was adjusted to 10 with KOH. Under ultrasonic irradiation and 25°C, a current density of 1A/dm ² was applied for an electroplating time of 10min to obtain an electroplated silver film test piece. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution, and the experimental period was 108h. The mass of the test piece before and after the experiment was weighed using an electronic analytical balance. Other experimental conditions and results are shown in Example 6 in Table 1. It can be seen that there is almost no iron bacteria microbial contaminant attached to the test piece.

Table 1 Changes in the mass of test pieces inhibiting iron bacteria adsorption under different electrodeposition examples

Comparative Example 1

The 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating weighed 2.0683g. The sheet was vertically hung in a beaker containing a cultured iron bacteria solution at 30°C. After the experimental period of 108h, the weight was 2.1964g. It can be seen that a large number of iron bacteria microorganisms are attached to the surface of the 304 stainless steel sheet without electrodeposited silver film.

Comparative Example 2

A 1.5x4cm (0.5mm thick) 304 stainless steel sheet after degreasing and pre-copper plating was placed in an electroplating solution of 45g/L silver nitrate, 50g/L sodium citrate, 60g/L sodium nitrate and 15g/L 5-methylhydantoin. The pH of the solution was adjusted to 10 with KOH. At 25°C, a current density of 0.3A/dm ² was applied for an electroplating time of 30min to obtain an electroplated silver film test piece. The obtained test piece was not bright and weighed a mass of 2.9123g. At 30°C, the test piece was vertically hung in a beaker containing a cultured iron bacteria solution. After an experimental period of 108h, the weighed mass was 2.9754. The mass change before and after the adsorption of microbial pollutants was 0.0631g.

As can be seen from the results of Comparative Example 1, due to the absence of a film of electrodeposited silver, a large amount of iron bacteria microbial contaminants have occurred on 304 stainless steel. As can be seen from the results of Example 1 in Table 1, when there is a silver film on 304 stainless steel, iron bacteria microbial contaminants are fully suppressed, and then when the silver surface becomes a hydrophobic and bright film, the presence of iron bacteria microbial contaminants is hardly seen on the silver film surface of 304 stainless steel substrates, as shown in Table 3, and its mass change is only 0.0038g. As can be seen from Comparative Example 2, although silver has an inhibitory effect on the growth of microbial dirt, the bright silver layer can further inhibit the attachment of microorganisms, and then compared with the results of the embodiment, the bright and hydrophobic silver layer has played a significant inhibitory effect on the attachment and growth of microbial dirt. As can be seen from this result, the attachment and growth of microbial contaminants on the substrate surface can be effectively suppressed by constructing a super-hydrophobic bright silver film.

Figure 1 is an electron microscope image of a silver film obtained in an electroplating solution of 45 g/L silver nitrate, 50 g/L succinimide, and 60 g/L potassium pyrophosphate, with the pH of the solution adjusted to 10 with KOH, at 25°C, with a current density of 0.3 A/dm ² and an electroplating time of 30 min. A in Figure 1 is without the addition of brightener 5-methylhydantoin, and B in Figure 1 is with the addition of 15 g/L 5-methylhydantoin. It can be seen from the electron microscope image of Figure 1 that after adding 5-methylhydantoin to the silver electroplating solution, the obtained electroplated film is very flat and has a very bright appearance.

FIG. 2 is an electron microscope image obtained by adding 3 g/L of 500 nm silver particles to the electrodeposition solution corresponding to B in FIG. 1 .

Figure 3 shows the contact angle of the electrodeposited silver film under different conditions. A in Figure 3 is the contact angle measured by the silver film without the brightener 5-methylhydantoin, which is 110.2°. When 15g/L 5-methylhydantoin is added, the obtained silver film becomes bright, and the contact angle increases to 129.6°, and the hydrophobicity of the surface of the silver film is enhanced. When 0.5g/L of 500nm silver particles are added, the obtained silver film becomes rougher than before, but the surface of the silver film is still bright, and its contact angle continues to increase to 141.4°. The contact angle continues to increase with the increase of the concentration of silver particles. When the concentration of silver particles is 3g/L, the contact angle of the obtained silver film reaches a maximum value of 152.2°. If silver nanoparticles are added, the contact angle of the obtained silver film will decrease.

Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims (5)

1. A method for preparing a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt, characterized in that: the silver film is prepared on the surface of a metal substrate by electrodeposition, and the electrodeposition solution includes a soluble silver salt and a brightener; the brightener is 5-methylhydantoin or its derivatives , before electrodeposition, a copper electroplating pretreatment step is also included; The concentration range of the soluble silver salt in the electrodeposition solution is 10-100 g/L, the concentration range of the complexing agent succinimide is 50-100 g/L, and the concentration range of the conductive salt potassium pyrophosphate is 50-120 g/L; Nano silver particles of 20-800 nm are also dispersed in the electroplating solution, and ultrasonic irradiation is used during the electroplating process; the amount of silver nano particles added to the electroplating solution is 0.3-5 g/L; The pH value of the electrodeposition solution is 8 to 11; In the structure of the 5-methylhydantoin derivative, R ₁ = H or CH ₃ ; R ₂ = H, CH ₃ , Cl or Br; R ₃ = H, CH ₃ , Cl or Br. 2. The method for preparing a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt according to claim 1, characterized in that the pH value of the electrodeposition solution is adjusted using potassium hydroxide and/or sodium hydroxide. 3. The method for preparing a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt according to claim 1, characterized in that: the electrodeposition temperature is 10-50°C, and the current density ranges from 0.1 to 2A/ ^dm2 ; The concentration range of 5-methylhydantoin or its derivatives in the electrodeposition solution is 5 to 30 g/L. 4. The method for preparing a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt according to claim 1, characterized in that: the soluble silver salt is silver nitrate, and the concentration of silver nitrate in the electrodeposition solution is in the range of 30 to 60 g/L; And/or, the concentration range of 5-methylhydantoin or its derivatives is 10-20 g/L. 5. A hydrophobic bright silver film prepared by the method for preparing a hydrophobic bright silver film for inhibiting the adhesion and growth of microbial dirt according to any one of claims 1 to 4.