Antibacterial and deodorizing agent containing platinum nanoparticle

Abstract

The purpose of the present invention is to provide an antibacterial and deodorizing agent which does not impair food additive grade safety even when added to hypochlorous acid water, does not reduce residual chlorine concentration during a storage period, and can further maintain antibacterial and deodorizing effects even after use. Provided is an antibacterial and deodorizing agent which has a pH of 5-6.5 and contains hypochlorous acid water at an effective concentration of 35-500 ppm and platinum nanoparticles having an average particle diameter of 1-100 nm. The antibacterial and deodorizing agent according to the present invention has antibacterial and deodorizing efficacy in applications such as automobiles, refrigerators, indoor environments, toilets, kitchens, trash cans, building entrances, shoe boxes, tobacco odors, pet odors, and, on floors, machinery, equipment, and tools in food factories, poultry houses, swine houses, cattle barns, and the like.

Description

Antibacterial and deodorizing agent containing platinum nanoparticles 【0001】 The present invention relates to an antibacterial and deodorizing agent used for antibacterial and deodorizing purposes in homes, facilities, stores, factories, etc., and more particularly to an antibacterial and deodorizing agent that provides sustained antibacterial and deodorizing effects. 【0002】 The global pandemic of COVID-19 has impacted every aspect of society and has strongly boosted the popularity of antibacterial and deodorizing agents. First and foremost, thorough handwashing and disinfection were recommended to prevent infection of hands and surfaces. This led to increased attention on antibacterial and deodorizing agents as a convenient and immediate means of use, and demand surged. Not only did this contribute to preventing personal infection, but infection prevention measures were also strengthened in public places, workplaces, and public transportation, providing an opportunity for the widespread adoption of antibacterial and deodorizing agents. 【0003】 Furthermore, businesses and service industries affected by the spread of infection proactively introduced antibacterial and deodorizing agents to ensure the safety of customers and employees. Disinfectants and antibacterial sprays became a common sight in stores, offices, and public facilities. As a result, antibacterial and deodorizing agents became an established part of daily life and a social standard. 【0004】 Furthermore, the COVID-19 pandemic heightened individual awareness of infection prevention and reinforced the importance of preventive medicine. This boosted demand for antibacterial and deodorizing agents, which began to be used regularly in ordinary households as part of infection prevention measures. Among these, hypochlorous acid water became widely popular because it is instantly effective against viruses and other pathogens that cannot be disinfected by alcohol or sodium hypochlorite (chlorine bleach). 【0005】 For example, Japanese Patent Publication No. 2022-26914 discloses a virus disinfectant that has a disinfecting effect against viruses and bacteria such as the novel coronavirus, comprising hypochlorous acid water with an effective chlorine concentration of a certain level or higher and a surfactant such as polyoxyethylene alkyl ether in a certain level or higher content (Patent Document 1). 【0006】Furthermore, Japanese Patent Publication No. 2024-25307 discloses an antimicrobial disinfectant solution that is highly safe for humans, can be used for air disinfection, and exhibits a long-lasting bacteriostatic effect, containing hypochlorous acid (HClO) at an effective concentration of 35 to 500 ppm and polylysine at an effective concentration of 5 to 500 ppm (Patent Document 2). 【0007】 Japanese Patent Publication No. 2022-26914 Japanese Patent Publication No. 2024-25307 【0008】 Hypochlorous acid (HClO), the active ingredient in hypochlorous acid water, is a weakly acidic to neutral chemical substance produced by the reaction of chlorine (Cl2) and water (H2O). Therefore, its pH is similar to that of human skin and tap water, making it highly safe even if it comes into contact with skin or is ingested. On the other hand, as a powerful oxidizing agent, it is known to inactivate, inhibit, and deodorize bacteria, viruses, and odors by oxidizing them. 【0009】 However, hypochlorous acid (HClO) is converted into hypochlorite ions (OCl) by light, heat, metal ions, organic matter, etc. － ) and chloride ions (Cl － It changes into ) and as the change progresses further, chloric acid (ClO3 － It has the property of gradually increasing. This chloric acid does not have antibacterial properties, so there was a problem that its commercial value as an antibacterial and deodorizing agent deteriorated. In addition, it is said that if it enters the human body it may cause symptoms such as methemoglobinemia, so the storage stability of hypochlorous acid water According to Japan's "Drinking Water Quality Standards Items", the amount of chloric acid contained in tap water is set at 0.6 mg / L (= 0.6 ppm) or less. 【0010】 Furthermore, when hypochlorous acid comes into contact with viruses and bacteria, it exerts its antibacterial and deodorizing effects, and instantaneously releases electrons (2e) from the target object such as bacteria. － It has the property of decomposing and breaking down substances, and then chemically changing almost entirely into water. Therefore, if hypochlorous acid water is not wiped away quickly after use, bacteria can adhere to the water droplets, which can actually make it easier for bacteria to multiply. 【0011】Furthermore, the antibacterial effect of conventional hypochlorous acid water ends the moment it comes into contact with organic matter, so if a sustained effect is required, it must be used frequently, which is a problem. Also, when hypochlorous acid water is sprayed onto the object to be coated, electrons (2e) are released from the target object such as bacteria. － After removing and breaking down the bacteria, most of it returns to water, so wiping is necessary to prevent the re-proliferation of bacteria that adhere to the water. For example, when customers change tables in a restaurant, it becomes necessary to disinfect and deodorize again, which increases the workload for employees. Also, in environments such as hospitals, where people are constantly exposed to viral and bacterial infections, the antibacterial and deodorizing effect wears off instantly, so antibacterial and deodorizing work must be done frequently, exacerbating the already busy workload and manpower shortage. 【0012】 The invention described in Patent Document 1 provides persistence by adding surfactants such as polyoxyethylene alkyl ethers. However, surfactants such as polyoxyethylene alkyl ethers are harmful when ingested orally, and skin irritation and serious eye damage have been reported, which presents a problem as they cannot be used around the kitchen or on tableware. 【0013】 Furthermore, while the invention described in Patent Document 2 includes polylysine to prolong the antibacterial and deodorizing effect, mixing sodium hypochlorite and polylysine causes a chemical reaction, resulting in a cloudy liquid, the formation of precipitates, and a decrease in residual chlorine concentration. 【0014】 Therefore, the present invention aims to provide an antibacterial and deodorizing agent that, when added to hypochlorous acid water, does not impair the safety of food additive grade, does not cause a decrease in residual chlorine concentration during storage, and maintains antibacterial and deodorizing effects even after use. 【0015】 To solve the above problems, the inventors investigated various additives that would not compromise the safety of food additive grade when added to hypochlorous acid water, and additives that would not reduce the residual chlorine concentration even when bacteriostatic additives were added. By chance, they discovered that adding platinum nanoparticles could solve the above problems. 【0016】This invention is based on such findings and provides an antibacterial and deodorizing agent containing hypochlorous acid water and platinum nanoparticles, with a pH of 5 to 6.5. 【0017】 According to the present invention, it is possible to provide an antibacterial and deodorizing agent that does not compromise the safety of food additive grade when added to hypochlorous acid water, suppresses the deterioration of hypochlorous acid over time during storage, and further enhances the antibacterial and deodorizing effect compared to hypochlorous acid water alone. Furthermore, since platinum nanoparticles are non-volatile substances, they remain in the place where the antibacterial and deodorizing agent of this embodiment is used. As a result, platinum nanoparticles accumulate with each use of the antibacterial and deodorizing agent, it becomes possible to further enhance the bacteriostatic effect of the application site. 【0018】 This figure shows the results of the antibacterial test. It is a magnified view of a portion of Figure 1 at the time when the growth inhibition zone (inhibition zone) was formed. 【0019】 Embodiments of the present invention will be described in detail below. Hypochlorous acid water can be produced by electrolyzing hydrochloric acid or sodium chloride (saline solution), by diluting and mixing sodium hypochlorite with a pH adjusting agent such as dilute hydrochloric acid, or by using carbon dioxide instead of acid, but hypochlorous acid water produced by any of these methods is acceptable. 【0020】 Hypochlorous acid, the main antibacterial component in hypochlorous acid water, exhibits high antibacterial activity even at low effective chlorine concentrations. For example, it is known that E. coli bacteria are killed at residual chlorine concentrations of 0.1 mg / L or higher (= 0.1 ppm). This hypochlorous acid water exhibits high antibacterial effects against various bacteria and viruses, and shows higher antibacterial activity compared to sodium hypochlorite. Furthermore, because hypochlorous acid water has a broad antibacterial range and is fast-acting, it is expected to be very useful for preventing the spread of the novel coronavirus. 【0021】In addition, hypochlorous acid water is far safer than sodium hypochlorite and is approved as a food additive. In particular, because the chlorine component in hypochlorous acid water has low persistence, it can also be used for washing food. For this reason, hypochlorous acid water is highly safe for the human body and does not cause skin irritation to hands when sprayed like alcohol, so it is widely used as an antibacterial and antiviral agent. The hypochlorous acid contained in this hypochlorous acid water exhibits a bactericidal effect the moment it reacts with organic matter, and then most of it returns to harmless water. 【0022】 If the effective concentration of hypochlorous acid (HClO) in the antibacterial and deodorizing agent is less than 2 ppm, the antibacterial effect of hypochlorous acid is too weak to suppress bacterial growth. On the other hand, if the effective concentration of hypochlorous acid (HClO) exceeds 500 ppm, not only does the antibacterial effect become saturated, but the hypochlorous acid itself also volatilizes. For this reason, it is preferable that the effective concentration of hypochlorous acid (HClO) is between 2 and 500 ppm. 【0023】 Platinum nanoparticles are materials made by miniaturizing platinum (Pt) into particles with a size in the nanometer range (1 to 100 nm). Because their physical and chemical properties differ significantly from bulk platinum (a mass of metallic platinum), including high specific surface area, excellent catalytic activity, high chemical stability, and electron acceptance and donation characteristics, research into the use of platinum nanoparticles as nanomaterials is progressing in fields such as catalysts, medicine, sensors, and environmental remediation. 【0024】 In this embodiment, from a safety standpoint, it is preferable to use food-grade platinum nanoparticles. Platinum nanoparticles are inherently safe substances as they do not rust or undergo chemical changes even when in contact with metals, but by using food-grade platinum nanoparticles, the disinfectant and deodorizer according to this embodiment can be used around the kitchen and on tableware. 【0025】In this embodiment, from the viewpoint of exhibiting a bacteriostatic effect, the concentration of platinum nanoparticles relative to the total antibacterial and deodorant agent is preferably 1.0 to 1000 ppm. However, the desired effect cannot be obtained if the concentration of platinum nanoparticles is less than 1.0 ppm. On the other hand, while the desired effect can be observed at concentrations of 100 ppm or higher, the effect plateaus, and the dispersibility in hypochlorous acid water decreases; therefore, the upper limit was set to 100 ppm. 【0026】 Furthermore, from the viewpoint of dispersing platinum nanoparticles in hypochlorous acid water and exhibiting a greater bacteriostatic effect, it is preferable that the average particle size of the platinum nanoparticles is 1 to 100 nm. By using platinum nanoparticles of this particle size, the platinum nanoparticles can be dispersed by Brownian motion without settling in the hypochlorous acid water. In addition, the platinum nanoparticles can be accumulated in small gaps, grooves, or uneven areas in the area where the antibacterial and deodorizing agent of this embodiment is used. 【0027】 Although hypochlorous acid water is a highly reactive aqueous solution, platinum nanoparticles have a low ionization tendency. Therefore, when added to hypochlorous acid water, they do not react and can be dispersed without reducing the effective chlorine concentration. While there are platinum nanoparticles that have been surface-modified with water-soluble ligands such as citric acid, PVP, PEG, and amino acids to ensure dispersibility in aqueous solutions, in this embodiment, platinum nanoparticles without these surface modifications are used because they would react with hypochlorous acid and be consumed. 【0028】 Platinum nanoparticles are partially oxidized in hypochlorous acid water, forming an oxide film such as PtO / PtO2. However, this film allows for reversible electron transfer, thus maintaining catalytic function while preventing excessive platinum elution. 【0029】 In this embodiment, the antibacterial and deodorizing agent suppresses the deterioration of hypochlorous acid (HClO) over time during storage because platinum nanoparticles suppress the decrease in the effective chlorine concentration of hypochlorous acid. The mechanism by which platinum nanoparticles suppress the decrease in the effective chlorine concentration of hypochlorous acid is as follows. 【0030】 When hypochlorous acid (HClO) decomposes, hypochlorite ions (OCl) are produced.－ ), chloride ions (Cl － ), and hydrogen ions (H ＋ ) are generated. When platinum nanoparticles (PtNP) are present there, an electron transfer reaction proceeds on the surface of the platinum nanoparticles, and hypochlorite ions (OCl － ) are regenerated into hypochlorous acid (HClO). Note that the platinum nanoparticles themselves are not consumed by this reactivation reaction and continue to function as a catalyst. 【0031】 【0032】 That is, since platinum nanoparticles catalyze the supply of hydrogen ions (H ＋ ), as a result, the cycle of HClO → H ＋ + ClO － → HClO reactivation is repeated. Thus, even if the reaction in which hypochlorous acid (HClO) changes to hypochlorite ions (OCl － ) proceeds during the storage period, the presence of platinum nanoparticles reactivates hypochlorous acid (HClO), so that a decrease in the available chlorine concentration can be suppressed. 【0033】 Note that none of the metals other than platinum can form a stable catalyst cycle in hypochlorous acid water. For example, silver and copper easily dissolve in the presence of hypochlorous acid (HClO) and cause an irreversible oxidation reaction, so they do not circulate as a catalyst and deteriorate the solution. Gold has high chemical stability but low electron transfer ability on the surface and cannot catalyze the redox reaction between hypochlorous acid (HClO) and hypochlorite ions (OCl － ). Palladium tends to induce overoxidation and rapidly consume hypochlorous acid (HClO). Also, transition metals such as iron and manganese cause precipitation and overreactions, impairing the long-term stability of the solution. Thus, metals other than platinum cannot maintain the reactivation cycle and are unsuitable as a catalyst. 【0034】 In this embodiment, also, in the process in which platinum nanoparticles (PtNP) catalyze hypochlorite ions (OCl － ) and regenerate them into hypochlorous acid (HOCl), hydroxyl radicals (HO·) are generated as a side route. Specifically, platinum nanoparticles are hypochlorite ions (OCl) in hypochlorous acid water.－ It has high surface activity that allows it to selectively adsorb (OCl). － When ) adsorbs onto the surface of platinum nanoparticles, the oxidation-reduction capacity of platinum causes the hypochlorite ions (OCl) to be released. － ) has electrons removed, and hypochlorite ions (OCl) are extracted. － ) is converted to a radical species, hypochlorite radical (OCl•) (Step 1). 【0035】 【0036】 Next, the generated hypochlorite radical (OCl•) is highly reactive with water molecules and reacts with surrounding water molecules to produce a hydroxyl radical (HO•), as well as chloride ions (Cl － ) and hydrogen ions (H ＋ ) is generated (Step 2). 【0037】 【0038】 In other words, on the surface of platinum nanoparticles, OCl － The radicalization reaction to OCl• and the radical conversion reaction from OCl• to HO• proceed in succession, generating a hydroxyl radical (HO•). 【0039】 Hydroxyl radicals (HO•) are extremely strong oxidizing agents (oxidation-reduction potential 2.58V to 2.80V), and can destroy bacteria, viruses, and biofilms in a short time, thus increasing the instantaneous bactericidal power of hypochlorous acid water. 【0040】 As described above, the antibacterial and deodorizing agent in this embodiment is activated by the catalytic action of platinum nanoparticles in hypochlorous acid water, producing hypochlorite ions (OCl). － Two pathways proceed in parallel: a main pathway that regenerates ) into hypochlorous acid (HOCl), and a secondary pathway that generates hydroxyl radicals (HO•) as a by-product. This mechanism of action occurs not only during the storage period of the antibacterial and deodorizing agent according to this embodiment, but also when the antibacterial and deodorizing agent according to this embodiment is applied to an object to be coated by spraying, etc., and comes into contact with organic matter, hypochlorous acid (HOCl) is converted into hypochlorite ions (OCl). － This can be expected even immediately after the change occurs. 【0041】 The antibacterial and deodorizing agent according to this embodiment has a pH of 5 to 6.5. Generally, hypochlorous acid (HOCl) changes its existence form depending on the pH in an aqueous solution; in the low pH range, it tends to exist as chlorine gas (Cl2), and in the high pH range, it exists as hypochlorite ions (OCl). － It exists as [a certain substance]. On the other hand, it is known that hypochlorous acid (HOCl), the main component responsible for disinfection, is present in the highest proportion in the slightly acidic range (pH 5 to 6.5). Therefore, by maintaining hypochlorous acid water in the aforementioned slightly acidic range, the disinfection performance can be maximized. 【0042】 Furthermore, in the slightly acidic range, compared to the strongly acidic range, irritation and corrosiveness are reduced, and the advantages of superior safety and handling can also be obtained. For this reason, the antibacterial and deodorizing agent according to this embodiment is particularly advantageous when its pH is adjusted to 5 to 6.5, from the viewpoint of achieving both antibacterial performance and safety. 【0043】 Furthermore, platinum nanoparticles exhibit a stable colloidal dispersion state in the weakly acidic to neutral pH range of 5 to 6.5. This is because the surface of the platinum nanoparticles in aqueous solution is modified by hydroxyl groups, leading to the equilibrium reaction shown in the following equation. 【0044】 【0045】 This is thought to be due to a change in the charge state via a specific mechanism. Specifically, under acidic conditions with a pH of less than 4.5, protonation of the surface progresses, reducing the surface charge of the particles and weakening the interparticle repulsive force, making aggregation more likely. On the other hand, under conditions with a pH of more than 7, deprotonation becomes dominant, generating excessive negative charge and making surface oxidation reactions more likely, which can lead to particle aggregation or dissolution. 【0046】In contrast, at a pH of 4.8 to 7, more preferably around pH 5 to 6.5, the balance between protonation and deprotonation on the surface of platinum nanoparticles is optimized, forming a hydroxyl base layer with a gentle negative charge. This maintains a constant zeta potential on the particle surface, and electrostatic repulsion acts between the particles, ensuring stable colloidal dispersion over a long period. Furthermore, within this pH range, the oxide film (PtO or PtO2) formed on the platinum surface does not become excessive, preserving the surface properties of the platinum nanoparticles and suppressing the progression of particle aggregation and dissolution. 【0047】 Therefore, in the antibacterial and deodorizing agent according to the present invention, by adjusting the pH to 5 to 6.5, it becomes possible to maintain colloidal dispersion based on the stabilization of the zeta potential, thereby improving storage stability and suitability for various applications. 【0048】 The antibacterial and deodorizing agent of this embodiment can be used for automobiles, refrigerators, rooms, toilets, kitchens, trash cans, entrances, shoe cabinets, cigarette odors, and pet odors. It is also effective for antibacterial and deodorizing floors, machinery, tools, and equipment in food factories, chicken coops, pig barns, cattle barns, etc. 【0049】 Product forms (dosage types) include impregnated bodies (solid objects impregnated with liquid), liquids (such as suction-type and film-permeable types), and spray types such as aerosols and pump sprays. 【0050】 Conventional hypochlorous acid water, when sprayed onto an object to be coated, releases electrons (2e) from the target object such as bacteria. － After removing and decomposing the bacteria, most of it returns to water, so wiping was necessary to prevent the re-proliferation of bacteria that adhere to the water. In contrast, the antibacterial and deodorizing agent of this embodiment does not require wiping after use, unlike conventional hypochlorous acid water. This is because the platinum nanoparticles remain on the uneven surface of the coated object and continuously exert a bacteriostatic effect. Furthermore, platinum nanoparticles accumulate each time the antibacterial and deodorizing agent is used, making it possible to exert a sustained bacteriostatic effect. 【0051】Table 1 summarizes the characteristics of the antibacterial and deodorizing agent of this embodiment, conventional hypochlorous acid water, and conventional disinfectant ethanol. Conventional hypochlorous acid water is superior to disinfectant ethanol in that it has a superior disinfecting effect against most bacteria and viruses, but it has a problem with storage because the hypochlorous acid deteriorates over time, due to temperature, ultraviolet light, etc. In contrast, the antibacterial and deodorizing agent of this embodiment contains OCl, which is produced by the deterioration of hypochlorous acid (HClO). － The re-oxidation of hypochlorite ions by the catalytic action of platinum reactivates hypochlorous acid (HClO), significantly improving the storage stability of hypochlorous acid water. Furthermore, the generation of hydroxyl radicals (HO•) during the reactivation cycle enhances the effects of hypochlorous acid. 【0052】 【0053】 1. To 20 L of antibacterial and deodorizing water and 33.3 ml of sodium hypochlorite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "Sodium Hypochlorite", component concentration 12%), platinum nanoparticles (Pt 99.9%, particle size 1-100 nm) and dilute hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hydrochloric acid concentration 8.5%) were added as a pH adjuster, and the pH was adjusted to the neutral range (6.2) to prepare the desired platinum nanoparticle-containing hypochlorous acid water (Examples 1 and 2). In addition, hypochlorous acid water without the addition of platinum nanoparticles (Comparative Example 1, pH 6.0) was also prepared. 【0054】 【0055】 2. Antimicrobial Testing The antimicrobial test was conducted as follows: Escherichia coli (ATCC 25922) was spread onto Mueller-Hinton agar using a sterile cotton swab. Once sufficient E. coli had grown, 50 μL of the sample solution was dropped into the center of the medium. The medium was then incubated at 37°C for 24 hours to identify areas of inhibition (zones of inhibition). Next, 50 μL of 1 M sodium thiosulfate was dropped into the areas of inhibition to inactivate the hypochlorite. The medium was then incubated at 37°C for 24 hours, 48 ​​hours, and 72 hours, and the erosion of E. coli into the areas of inhibition at each time point was visually observed. 【0056】The results are shown in Figure 1. In the sample of Comparative Example 1, the hypochlorous acid was deactivated after neutralization treatment, and erosion by E. coli was observed in the areas where growth was inhibited (zone of inhibition). In contrast, it was found that the areas where growth was inhibited (zone of inhibition) were not eroded in the samples of Examples 1 and 2 even after neutralization treatment. This suggests that the platinum nanoparticles suppressed bacterial erosion. Furthermore, it was found that the degree of the inhibitory effect increased with the amount of platinum nanoparticles contained. 【0057】 Furthermore, an antibacterial test was conducted using a sample of hypochlorous acid water containing 0.75 ppm platinum nanoparticles in the same manner as described above, but no effect in suppressing bacterial erosion was observed. 【0058】 Figure 2 is a magnified view of a portion of Figure 1 at the time of the formation of the growth inhibition zone (inhibition zone). The only difference between the example and the comparative example is the presence or absence of platinum nanoparticles, but the growth inhibition zone (inhibition zone) was more clearly formed in the example than in the comparative example. This indicates that the sample in the example was catalyzed by the action of platinum nanoparticles in hypochlorous acid water, causing hypochlorite ions (OCl) to form. － This strongly suggests that the enhancement of antibacterial activity is due to the parallel operation of two pathways: a main pathway that regenerates ) into hypochlorous acid (HOCl), and a secondary pathway that produces hydroxyl radicals (HO•) as a by-product.

Claims

1. An antibacterial and deodorizing agent containing hypochlorous acid water and platinum nanoparticles, with a pH of 5 to 6.

5.

2. The antibacterial and deodorizing agent according to claim 1, wherein the average particle size of the platinum nanoparticles is 1 to 100 nm.

3. The antibacterial and deodorizing agent according to claim 1 or 2, wherein the concentration of the platinum nanoparticles is 1.0 to 1000 ppm.

4. The antibacterial and deodorizing agent according to claim 1 or 2, wherein the hypochlorous acid component of the hypochlorous acid water is at an effective concentration of 2 to 500 ppm.

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