KR20070083259A - Titanium-silver photocatalytic alloy - Google Patents

Abstract

A technology which can improve a photocatalytic effect of a titanium oxide coating film in a manner that is different from conventional techniques is provided. A titanium-silver photocatalytic alloy contains more than 0 to 5 at.% of silver(Ag), and the balance of Ti and inevitable impurities, and comprises a titanium oxide coating film that is formed on its surface and functions as a photocatalyst by photo excitation. The titanium oxide coating film has the crystal structure of anatase.

Description

Titanium-Silver Photocatalyst Alloy {TITANIUM-SILVER PHOTOCATALYTIC ALLOY}

1 is a schematic diagram for a photocatalyst experiment according to an embodiment of the present invention.

2 is a scanning electron microscope (SEM) image of each specimen according to an embodiment of the present invention, Figure 2a is a surface shape of the thermally oxidized Ti for 1 hour at 400 ℃, Figure 2b is 250V anode for 3 minutes It is the surface shape of oxidized Ti, FIG. 2C is the surface shape of the TiAg alloy thermally oxidized at 400 degreeC for 1 hour, and FIG. 2B is the surface shape of the TiAg alloy anodized for 3 minutes at 250V.

3A and 3B are X-ray diffraction patterns for Ti and TiAg alloys, respectively, indicating that TO and AO were thermally oxidized at 400 ° C. for 1 hour and anodized at 250 V for 3 minutes, respectively, where T is Ti (substrate). , A points to Anatase.

4A and 4B show 4.8 × 10 ⁶ in Ti, Ti (TO), Ti (AO) and TiAg, TiAg (TO), TiAg (AO) specimens. S. mutans were dropped from each specimen of CFU / ml and irradiated with UV-A for 60 minutes to show viable bacterial count (oxidation method was as described above, and Controls were covered with black cloth. Means with the same letters are not significantly different. (α = 0.05))

Figures 5a and 5b shows the number of cells survived by dropping 4.8 × 10 ⁷ CFU / ml of L. acidophilus on each specimen and irradiating ultraviolet A for 60 minutes as in FIGS. 4a and 4b (the oxidation method is as described above, Controls were covered with black cloth.)

6A and 6B show that S. mutans were dropped and UV A irradiation on Ti, Ti (TO), Ti (AO) and TiAg, TiAg (TO) and TiAg (AO) specimens from each specimen at 4.8 × 10 ⁶ CFU / ml. After 20 minutes, 40 minutes, 60 minutes, 80 minutes, and 100 minutes, the bacterial solution is collected and the number of viable bacteria is shown (the oxidation method is the same as described above).

Figures 7a and 7b as shown in Figures 6a and 6b drop 4.8 × 10 ⁷ CFU / ml of L. acidophilus to each specimen, and after 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes of irradiation with ultraviolet A The number of viable bacteria is shown (oxidation method is the same as described above).

8 schematically shows the principle of the photocatalyst.

The present invention relates to a titanium-silver photocatalyst alloy.

Photocatalyst is a technology that promotes the reaction by absorbing light, and is recently used in various fields such as self-cleaning, antibacterial, deodorization, toxin decomposition, and cancer treatment.

As a result of the previous research, Anatase type titanium oxide (TiO ₂ ) was known as the material which exhibits the best photocatalytic effect, and researches on the application field and improvement of the effect are ongoing. In general, the use of titanium oxide is made in the form of powder to increase the surface area and improve the photocatalytic effect, and in the form of sol or secondary processed product in actual application. This technique is also an application for imparting photocatalytic properties to a base material having no photocatalytic properties, and a secondary technology is also required to prevent photocatalytic performance of titanium oxide from being degraded by reaction with the base material.

The present technology aims to express a photocatalytic effect by forming titanium oxide directly on the surface of a base material using a titanium alloy having a photocatalytic effect as a base material.

The technique of expressing the photocatalytic effect of the titanium alloy is made possible by forming an oxide film on the surface layer of the base material. By increasing it.

However, there is a limit to the improvement of the photocatalytic effect on such an oxide film, and there is a need for a method capable of bringing the photocatalyst to another aspect.

An object of the present invention is to provide a technique that can improve the photocatalytic effect of the titanium oxide film in a form different from the prior art.

Accordingly, the present invention provides a titanium-silver photocatalyst alloy composed of 0 <Ag ≤ 5 at%, the remaining Ti and inevitable impurities, and the titanium oxide film formed on the surface acts as a photocatalyst by photoexcitation.

Here, the titanium oxide film preferably has an anatase crystal structure.

When Ag is added to the Ti-Ag alloy in excess of 5 at%, Ti ₂ Ag intermetallic compounds are precipitated, which adversely affects the corrosion resistance. Moreover, even when a large amount of Ag is added, a large improvement in physical properties due to the increase in the amount of Ag cannot be expected. In addition, it is an expensive alloy element, so increasing the amount of addition decreases the economic efficiency. Therefore, the upper limit is limited to 5 at%. In addition, when the structure of the Ti-Ag alloy according to the present invention is the α-β double phase, it can be expected to increase the strength due to solid solution strengthening and phase transition (α → β) of Ag element. In addition, when the Ag content is 1.5 to 4.0 at% in the Ti-Ag alloy according to the present invention, since the β phase is more stably present, the corrosion resistance is improved while obtaining the strength increase effect due to the solid solution strengthening and phase transition of the Ag element described above. At the same time, the effect of precipitates is small and corrosion resistance can be prevented.

In addition, the Ti-Ag alloy according to the present invention is preferably carried out in a vacuum state to maintain the purity of Ti-Ag at 99.8 wt% or more. This is because the incorporation of impurities increases the strength of the alloy but greatly reduces the corrosion resistance. The incorporation of oxygen in the impurities is actively suppressed and limited to 0.15 wt% or less.

The photocatalytic reactors known to date are as follows (see Figure 8).

^{_{① TiO 2 + hν → e -}} + h +

_{^{② e - + O 2 → ·}} O 2 -

_{^{③ · O 2 - + H +}} → H 2 O ·

④ h ⁺ + H ₂ O → · OH + H ⁺

⑤ H ⁺ → H _trap ⁺

As shown in the above reactor, the photocatalytic effect consists of electrons and holes generated in the surface layer by absorbing light. The hydroxy radicals (.OH) produced by the secondary reaction of the holes thus formed are known as the main active species of the photocatalytic oxidative decomposition reaction. Therefore, in order for the photocatalytic effect to occur better, the electrons and holes generated at this time may participate in different secondary reactions without recombination. Since the electrons and holes generated by the absorption of light recombine again instantaneously, it is necessary to prevent such recombination in order to induce electrons and holes into the secondary reaction.

The inventors prepared a Ti-Ag alloy to form a series of Anatase type oxide films (TiO ₂ ), and after studying the photocatalytic effect, Ag added as an alloying element quickly moved electrons generated by absorption of light. The present invention has been completed by finding that preventing recombination with holes results in an improved probability of secondary reaction between electrons and holes.

Hereinafter, the present invention will be described in more detail with reference to Examples and the accompanying drawings. However, the scope of the present invention is not limited by the following description, and the scope of the present invention will be limited only by the following claims.

Description of Examples and Comparative Examples

Preparation of the Psalms

Pure Ti (Grade III, ASTM F67, Supra Alloys, Inc. California, USA) and TiAg based alloys (Ti-2.0at% Ag, Biomaterialskorea, Seoul, Korea) were used. The specimen was used by cutting a plate having a thickness of 1 mm to 5 × 5 mm ² size.

Sponge Ti and Ag were used as the raw material for dissolving TiAg alloy. Ag content was 2.0 at%. After metering, 30 g was dissolved using an arc melting furnace and repeated three times. Castings obtained by dissolution were heat treated for 72 hours in a vacuum furnace maintained at a temperature of 950 ° C. to remove composition segregation for composition homogenization. It is hot rolled at 950 ° C. to a uniform thickness of about 1 mm and the resulting oxide scale is removed by acid washing (ratio of hydrofluoric acid: nitric acid: distilled water, 1: 3: 7). It was. The solution was further annealed in a vacuum furnace at 950 ° C. for 1 hour to remove precipitates generated during hot rolling and then cooled in water at room temperature. This was cut into 5 × 5 mm ² size, polished with emery paper No. 600 and ultrasonically washed with acetone and ethyl alcohol.

The Ti and TiAg specimens were surface treated with thermal oxidation (TO) and anodization (AO), respectively. In the case of TO, the furnace was heat-treated at 400 ° C. for 1 hour in a muffle furnace and then cooled. In the case of AO, a 250 V potential was applied for 3 minutes between the anode and the Pt plates in a 0.04 M β-glycerophsphate disodium salt pentahydrate and 0.4 M calcium acetate mixture solution.

Scanning electron microscope and X-ray diffraction  analysis

In order to observe the oxide layer formation on the surface of the specimen, it was observed at 15000 magnification using a scanning electron microscope (S-2700, S-4200, Hitachi, Japan).

The surface topography of the alloy specimens treated with TO and AO is shown in FIG. 2 by scanning electron microscopy (SEM).

The TO had a thickness of about 100 and the AO had a thickness of 1-2 μm. The surface of Ti and TiAg specimens treated with TO had a smoother and thinner oxide layer than the AO treated specimens. It remained (FIGS. 2A and 2C).

Ti and TiAg specimen surfaces treated with AO are shown in FIGS. 2B and 2D, respectively. In the specimens treated with AO, both Ti and TiAg formed “craters” with an inner diameter of 2 μm and an outer diameter of 5 μm on the surface, and showed higher surface roughness than the TO specimen. Fig. 2B shows the result of photographing this by tilting 45 degrees.

An X-ray diffractometer (D-Max Rint 2400, Rigaku, Japan) was used to qualitatively analyze the type of specimen surface oxide. Cu Kα ₁ was used as a target, and the scan range and rate were 20-80 ° and 1 ° / min, respectively.

3 shows the results of X-ray diffraction analysis on the surface of the specimen according to the oxidation treatment method of Ti and TiAg together with the results of the control specimen without oxidation treatment. The surface analysis results of Ti are shown in FIG. 3A, and the results of TiAg are shown in FIG. 3B. In the case of heat treatment with TO, neither Ti nor TiAg showed a significant difference compared to the control. However, when treated with AO, it can be seen that both of Ti and TiAg formed anatase on the surface relatively stably without post-treatment.

Analysis of Antimicrobial Effects According to Photocatalyst Coating

S. mutans (KCTC 3298) was in 20 mL of BHI (brain heart infusion) medium and L. acidophilus (KCCM 32820) was incubated in 20 mL of Lactobicilli MRS medium for 12 hours at 37 ° C and shaken at 4000 rpm. Bacterial concentrations were diluted in phosphate-buffered saline (PBS) solution to make S. mutans 4.8 × 10 ⁶ colony forming units (CFU) and L. acidophilus to 4.4 × 10 ⁷ CFU.

An analysis of variance test was performed to verify the significance of each specimen in the antimicrobial effect experiments by the photocatalyst coating method. .

-Measurement of antimicrobial effect by photocatalyst coating method

Ultraviolet A was irradiated to Ti, Ti (TO), Ti (AO), TiAg, TiAg (TO), and TiAg (AO) specimens as experimental groups, and each specimen was coated with a black cloth to verify the stability of the bacteria during the experiment. It was used as a control group.

Pipette 100 μL of PBS solution containing 4.8 × 10 ⁶ S. mutans and 4.4 × 10 ⁷ L. acidophilus onto the test and control specimens, respectively, and pipet them into UV A (Philips, 2 × 15W, black light 356 nm peak). emission) was irradiated for 60 minutes at an intensity of 1.0 mW / cm ² (UVmeter, Matts, USA). The specimen was placed on a petri dish filled with ice water to prevent drying due to temperature rise during light irradiation, and the distance between the specimen and the UVA lamp was 7 cm (FIG. 1). After irradiation, each reaction solution was placed in 900 uL of PBS at pH 7.2, diluted to 10 ^{-5 in} 10-fold increments, shaken for 10 minutes (Vortex 200 rpm), and 100 μL of each sample was added to S. mutans using a triangular plater. Were coated on BHI agar medium and L. acidophilus on Lactobicilli MRS agar medium. A pair of plates was plated for each reaction solution. Plates were incubated at 37 ° C. for 36 hours to count bacteria and calculate CFU. The experiment was repeated four times and the sterilization effect was obtained using the following terms.

Survival rate (%) = Number of bacteria after light irradiation / Number of bacteria before light irradiation × 100

4.8 × 10 ⁶ S. mutans were dropped on Ti, Ti (TO), Ti (AO), TiAg, TiAg (TO), and TiAg (AO) specimens, and the number of viable cells survived by irradiating UVA for 60 minutes. Indicated. As a control, the untreated specimens showed a survival rate of 85% Ti, 73.5% Ti (TO), and 73.5% Ti (AO), but there was no significant difference (p> 0.05). Ti (TO) showed 6.7% and Ti (AO) showed 0% survival rate, showing a significant difference in order of Ti> Ti (TO)> Ti (AO) (p <0.05) (FIG. 4A). In the TiAg alloy, the control group showed 99.6% TiAg, 93.3% TiAgTO, and 69.6% TiAg (AO), showing no significant difference (p> 0.05) .The experimental group showed 14.2% TiAg, 3.1% TiAgTO, 3.1% TiAg ( AO) showed 0% survival rate, showing a significant difference in order of TiAg>TiAgTO> TiAg (AO) (p <0.05) (FIG. 4B).

L. acidophilus (4.4 × 10 ⁷⁾ was added to each specimen, and the number of viable cells survived by irradiation with ultraviolet A for 60 minutes is shown in FIG. 5. The control group showed 68% Ti, 80.7% Ti (TO), and 85.9% Ti (AO), showing no significant difference (p> 0.05). %, Ti (TO) was 35.2%, and Ti (AO) was 27.0%. There was no significant difference between the samples (p> 0.05) (Fig. 5a). In the TiAg alloy, the control group showed 88.4% of TiAg, 83.0% of TiAgTO, and 99.8% of TiAg (AO), showing no significant difference (p> 0.05). %, TiAg (TO) showed 38.8%, TiAg (AO) showed 29.8% survival rate, showing no significant difference between specimens (p> 0.05) (FIG. 5B).

-Measurement of antimicrobial effect over time of photocatalytic reaction

 Ti, Ti (TO), Ti (AO), TiAg, TiAg (TO), TiAg (AO) 20 minutes (1 step), 40 minutes (2 steps), 60 minutes (3 steps) after UV A irradiation ), Take 100 μL of reaction solution every 20 minutes until 80 minutes (4 steps), 100 minutes (5 steps) and smear the bacterial solution in the same way as the previous method to measure the degree of bacterial death according to the photocatalytic reaction time. It was. The antimicrobial effect was expressed as a graph of survival curve over time and the bactericidal effect was expressed in the following terms.

Sterilization Rate Constant = (Previous Stage Survival-Current Stage Survival Rate) / 20 (minutes)

20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes of UV A irradiation with 4.8 × 10 ⁶ S. mutans on a Ti, Ti (TO), Ti (AO), TiAg, TiAgTO, TiAg (AO) specimen After that, the bacterial counts were collected and shown in FIG. 6. In the case of Ti, the survival rate decreased as the irradiation time elapsed in all specimens, but the survival rate of the steep slope decreased with the steep slope of Ti (AO) compared to 100% sterilization when Ti and Ti (TO) became 100 minutes. The bacteria were killed (FIG. 6A). Bacterial survival curves were in the form of linear function and Ti and Ti (TO) showed low sterilization rate constants up to stage 1, but began to decrease rapidly from stage 2 with sterilization rate constants of 1.8 and 1.6, respectively. In comparison, Ti (AO) showed a high sterilization rate constant of 2.3 from the first stage, and the survival rate rapidly decreased. In the case of TiAg, the survival rate decreased according to the irradiation time in all specimens. Unlike Ti, survival rate decreased rapidly from the first stage in all specimens. Especially, TiAg (AO) has the highest one-step sterilization rate constant of 4.8, which is almost the most. The bacteria were killed at 20 minutes and 100% of TiAg (TO) was killed at 80 minutes and TiAg at 100 minutes (Fig. 6b).

Ti was significantly smaller in the order of Ti> Ti (TO)> Ti (AO) for each step, and TiAg alloys were also smaller in order of TiAg> TiAg (TO)> TiAg (AO) (Table 1). ).

Table 1.Duncan's grouping of CFU of S. mutans as a function of irradiation time after photocatalytic reaction using TiO₂ film formed by different oxidation methods in each specimen

20 minutes 40 minutes 60 minutes 80 minutes 100 minutes Mean Group Mean Group Mean Group Mean Group Mean Group Ti

4.63 ×

a * 2.86 ×

ab + 2.19 ×

c # 1.3 ×

b ^ 0 a † Ti (TO) 4.22 ×

a * 2.64 ×

ab + 1.9 ×

b # 1.88 ×

a ^ 0 a † Ti (AO) 2.59 ×

b * 1.91 ×

c + 0 d # 0 c ^ 0 a † TiAg 3.4 ×

ab * 2.43 ×

a + 1.27 ×

a # 6.2 ×

b ^ 0 a † TiAg (TO) 2.69 ×

b * 2.33 ×

bc + 8 ×

c # 0 c ^ 0 a † TiAg (AO) 1.4 ×

c * 0 d + 0 d # 0 c ^ 0 a †

The initial cell concentration was 4.8 × 10 ⁶ CFU / mL. Means with the same letters are not significantly different. (α = 0.05)

The number of cells survived after dropping 4.4 × 10 ⁷ L. acidophilus in each specimen and 20, 40, 60, 80, and 100 minutes of light irradiation was shown in FIG. 7. Survival rate decreased slowly compared to S. mutans with the irradiation time in both Ti and TiAg specimens. The sterilization rates between the specimens did not show any significant difference (Table 2), and most of Ti and TiAg were sterilized at 100 minutes, while Ti (TO), Ti (AO), TiAg (TO), and TiAg (AO) were 100 100% killed in minutes.

Table 2. Duncan's grouping of CFU of L. acidophilus as a function of irradiation time after photocatalytic reaction using TiO₂ film formed by different oxidation methods in each specimen

20 minutes 40 minutes 60 minutes 80 minutes 100 minutes Mean Group Mean Group Mean Group Mean Group Mean Group Ti

3.6 ×

a * 2.36 ×

b + 1.24 ×

CD# 1 ×

d ^ 2 ×

b † Ti (TO) 2.8 ×

ab * 2.43 ×

b + 2.31 ×

a # 5.1 ×

cd ^ 1 ×

b † Ti (AO) 2.36 ×

b * 2.1 ×

b + 1.47 ×

bc # 1.14 ×

b ^ 0 b † TiAg 3.12 ×

ab * 2.96 ×

a + 1.14 ×

d # 9.1 ×

bc ^ 5.4 ×

a † TiAg (TO) 2.32 ×

b * 2.19 ×

b + 2.05 ×

a # 1.75 ×

a ^ 0 b † TiAg (AO) 3.47 ×

a * 3.36 ×

a + 1.56 ×

b # 1.03 ×

b ^ 0 b †

The initial cell concentration was 4.4 × 10 ⁷ CFU / mL. Means with the same letters are not significantly different. (α = 0.05)

Since the main part of the light constituting the sun light is visible light, it is considered that it is desirable to use the effect of preventing the recombination of electron-holes in order to increase the efficiency of the photocatalytic reaction without a light lamp. In the present invention, the e-Ag - In the case of Ti for S. mutans in the photocatalytic effect test by S. mutans with the passage of time were to validate the prevention of hole recombination effect is reduced at a lower rate in the step 1 while sharply in the step 2, In the case of TiAg alloys, Ag was thought to have contributed to shortening the process of cell wall destruction due to the rapid decrease in the number of cells from the first stage.

The antimicrobial effect of TiAg in comparison with Ti in the present invention is thought to be due to the effect of preventing the recombination of electron-holes of Ag. The effect of permanent Ag is expected to be expected.

Cytotoxicity experiment

In order to measure the cytotoxicity, the specimens were processed to agar and the contact area was 5 × 5 mm ² , and all surfaces were polished up to # 4000 times with SiC abrasive paper, washed with sterile distilled water, and sterilized with ethylene oxide gas. The positive control group was Gutta percha (metabiomed, Korea) and the negative control group was Glass. Suspension was made by culturing rat fibroblast L-929 cells (fibroblast connective tissue of 100-day old male mouse) in RPMI (Gibco, USA) medium containing 10% fetal bovine serum (FBS, Gibco, USA). 10 mL of the cell suspension was added to the petri dish, followed by incubation for 24 hours. RPMI medium was removed, Eagle's agar medium and RPMI medium at 45-50 ° C. were mixed 1: 1, and 10 mL was added to each petri dish and left at room temperature for 30 minutes. After the medium was solidified, 6 mL of neutral red vital stain solution was slowly added to the center to allow the dye to spread to the front, and then left for 1 hour. Immediately after removal of the dye, the specimen was placed on the agar, and the cells were incubated for 24 hours in a CO ₂ incubator (VS-9108MS, Vision Scientific Co., Korea) maintaining 37 ° C., 5% CO ₂ , and 100% humidity. . Place Petri dish on white paper and observe the size of the discoloration range to get the zone index, and calculate the rate of cell death with an inverted phase contrast microscope (CK2, Olympus, Japan) to calculate the Lysis index. Obtained. Response index (Response index, ISO 7405: 1997 (E)) was obtained by averaging the Zone index and Lysis index of four specimens.

To evaluate the effect of TiO₂ on fibroblast toxicity, the cytotoxicity of fibroblast L-929 was evaluated by agar overlay test. The TiO₂ oxide films of Ti and TiAg alloys were not toxic to fibroblasts (Table 3).

Table 3. Cytotoxicity of Ti and TiAg

Sample Zone Index Lysis Index Response Index Cytotoxicity Ti 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none Ti (TO) 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none Ti (AO) 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none TiAg 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none TiAg (TO) 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none TiAg (AO) 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none Positive (Gutta Percha) 3 3 3/3 toxic 3 3 3/3 toxic Negative (glass) 0 0 0/0, 0/0 none 0 0 0/0, 0/0 none

  TO and AO means thermally oxidized at 400 ° C for 1 hour and anodic oxidation-treated at 250 V for 3 min. respectively.

According to the present invention, by minimizing the recombination of electrons and holes generated by the photoexcitation in the titanium oxide film, the result is further improved the probability of the secondary reaction that the electrons and holes cause a photocatalytic effect.

Accordingly, the present invention can be effectively used in various fields such as self-cleaning, antibacterial, deodorization, toxin decomposition, cancer treatment, and the like.

Claims (2)

A titanium-silver photocatalyst alloy comprising 0 <Ag ≤ 5 at%, remaining Ti and inevitable impurities, and a titanium oxide film formed on its surface acts as a photocatalyst by photoexcitation. The method of claim 1, The titanium oxide film is titanium-silver photocatalyst alloy, characterized in that it has an anatase crystal structure.

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