KR20110050213A - Fabrication of uniform silica/nitrogen-doped titania core/shell nanoparticles by interfacial sol-gel method and application to visible light photocatalyst - Google Patents

Abstract

PURPOSE: A method for fabricating uniform titania core/shell nano particles doped with silica/nitrogen and the application of the nano particles are provided to obtain the nano particles without the additional introduction of dopant. CONSTITUTION: A method for fabricating uniform titania core/shell nano particles doped with silica/nitrogen includes the following: Silica nano particles are dispersed in the mixed solution of ethanol, acetonitrile, and ammonia solution. Titanium dioxide precursor and nitrogen dopant are added to the dispersed solution. An interfacial sol-gel reaction is occurred on the surface of the silica nano particles on which ammonium ions are introduced. The dispersed solution is dried and is thermally processed. The nitrogen is efficiently doped with titanium dioxide crystalline.

Description

Fabrication method of uniform silica / nitrogen doped titanium dioxide core / cell nanoparticles using interfacial sol-gel reaction and application as photocatalyst reacting to visible light {Fabrication of uniform silica / nitrogen-doped titania core / shell nanoparticles by interfacial sol -gel method and application to visible light photocatalyst}

The present invention relates to a method for producing uniform silica / nitrogen-doped titanium dioxide core / cell nanoparticles using an interfacial sol-gel method and its application to photocatalysts reacting with visible light. By coating nitrogen-doped titanium dioxide on silica nanoparticles using an interfacial sol-gel reaction that occurs only on the surface of silica nanoparticles via surface charges introduced in addition to silica colloidal nanoparticles, A method of preparing silica / nitrogen doped titanium dioxide core / cell nanoparticles is provided to provide a photocatalyst having high efficiency under visible light.

Nanomaterial generally refers to a material having a size between 1 and 100 nanometers, and has a superior physical properties compared to conventional bulk materials due to the large surface area. Among them, titanium dioxide nanoparticles have been applied to application fields as photocatalysts due to high efficiency of photoactivity, low cost, non-toxicity, and chemical stability. In particular, nitrogen-doped titanium dioxide nanoparticles produce OH radicals and superoxide ions when exposed to UV or visible light, which are organic pollutants by decomposing organic matter into carbon dioxide and water with strong oxidizing power. You can also get rid of microorganisms.

In the preparation of nitrogen-doped titanium dioxide nanoparticles having these characteristics, it is made through the doping process of magnetron sputtering, ion implantation, and heat treatment process in ammonia and oxygen chamber. There is a method, and a method of making without doping process through a heat treatment after the sol-gel reaction of a titanium dioxide precursor containing nitrogen or a nitrogen dopant and a titanium dioxide precursor. In general, the most widely used method is to make nitrogen-doped titanium dioxide nanoparticles by heat treatment after a sol-gel reaction between a nitrogen dopant and a titanium dioxide precursor.

However, in the production of nitrogen doped titanium dioxide nanoparticles, the high reactivity of the titanium dioxide precursor is not easy to prepare nanoparticles, the prepared nitrogen-doped titanium dioxide nanoparticles do not have a uniform size, individual Rather than having the shape of nanoparticles, entanglement occurs between the nanoparticles to form an aggregate, and finally due to high heat treatment of more than 500 ℃ to promote the entanglement between nanoparticles to form a larger aggregate. Non-uniform nitrogen-doped titanium dioxide nanoparticles are introduced as a coating to form a thin film or as a filler into the polymer to form a thin film or polymer composite, which acts as a factor that inhibits the uniformity of the thin film surface and the polymer composite . In addition, the nitrogen-doped titanium dioxide, which is not present as individual nanoparticles and forms an aggregate, has a surface area smaller than the surface area that nanoparticles can actually have, so that the nitrogen-doped titanium dioxide nanoparticles may inherently have. It is important to produce uniform, nitrogen-doped titanium dioxide nanoparticles because they will exhibit lower efficiency than good photocatalytic efficiency from surface area. As a method for improving this, many methods for producing uniform nitrogen-doped titanium dioxide nanoparticles using a sol-gel reaction using a polymer template have been studied. In the case of producing nitrogen-doped titanium dioxide using a polymer template, since the size of the polymer template is generally 100 nanometers or more, a large amount of nanoparticles of 100 nanometers or less is required. You will have difficulty. In the preparation of polymer thin films or composites having nitrogen-doped titanium dioxide, photocatalytic characteristics of organic contaminant removal, microbial removal, and self-purification, nanoparticles having a uniform size and smaller than 100 nanometers are suitable. Therefore, in the case of nitrogen-doped titanium dioxide particles having a size of 100 nanometers or more manufactured using a polymer template, the photocatalytic efficiency is related to the preparation of polymer thin films or composites characterized by contaminant removal, microbial removal, and self-purifying photocatalyst. It is a big problem.

Therefore, in order to prepare nitrogen-doped titanium dioxide nanoparticles for use as a filler of polymer thin films or composites having high efficiency photocatalyst characteristics, they have a uniform size of less than 100 nanometers and have a simple and economical method. There is a strong demand for production methods.

The purpose of the present invention is to solve the problems of the prior art by adding ammonium ions to nitrogen nanoparticles doped with nitrogen doped titanium dioxide using an interfacial sol-gel reaction that occurs only on the surface of the silica nanoparticles. By coating to provide a method for producing uniform silica / nitrogen doped titanium dioxide core / cell nanoparticles.

In addition, another technical problem of the present invention is that the silica-nitrogen-doped titanium dioxide nanoparticles have a higher processability than the photocatalyst particles according to the prior art and have a nitrogen-doped core-cell structure having excellent photocatalytic efficiency under visible light. To provide a silica / titanium dioxide composite.

After numerous experiments and in-depth studies, the inventors have limited nitrogen dopant and dioxide only on the surface of silica nanoparticles by using an interfacial sol-gel reaction on the silica nanoparticles in which ammonium ions have been introduced to the surface, unlike conventional methods. After allowing the titanium precursor to react, it was confirmed that silica / nitrogen-doped titanium dioxide core / cell nanoparticles can be prepared through a relatively low temperature heat treatment process, and the prepared silica / nitrogen-doped titanium dioxide core / cell nanoparticles were produced. It has been found that the particles have significantly improved photocatalytic efficiency under visible light as compared to the photocatalytic particles used in the prior art, and have led to the present invention.

The present invention utilizes triethylamine, ammonium chloride, ammonia solution using an interfacial sol-gel reaction that is limited to the surface of silica nanoparticles having a size of 1 nanometer to several micrometers. Nitrogen dopants of ammonium solution, urea, thiourea, hydrazine hydrate, titanium tetraisopropoxide, titanium butoxide, titanium ethoxide Silica particles are coated with nitrogen-doped titanium dioxide through the sol-gel reaction of titanium dioxide precursors of ethoxide), titanium oxysulfate, and titanium chloride.

Nitrogen-doped titanium dioxide nanoparticles coated on the silica nanoparticles according to the present invention

(A) dispersing the silica nanoparticles in ethanol, acetonitrile, ammonia solution mixed solution;

(B) adding a nitrogen dopant and a titanium dioxide precursor to the dispersion solution so that the interfacial sol-gel reaction occurs only on the surface of the silica nanoparticles into which ammonium ions are introduced;

(C) drying the dispersion solution, followed by heat treatment, so that nitrogen is efficiently doped into the titanium dioxide crystals.

A method for preparing uniform silica / nitrogen-doped titanium dioxide core / cell nanoparticles using the interfacial sol-gel method which introduces additional ions according to the present invention and reacts restrictively on the surface of silica nanoparticles has been reported. It is a completely new method, which significantly reduces the problem of non-uniform particles caused by the conventional method, and by easily changing the size of the silica particles, it is possible to control the size of the particles in the range of several nanometers, and doped with titanium dioxide The amount of nitrogen can be easily adjusted according to the amount of nitrogen dopant and the change of the heat treatment temperature. In addition, a simple manufacturing method has the advantage of mass production of uniform silica / nitrogen doped titanium dioxide core / cell nanoparticles. The uniform silica / nitrogen-doped titanium dioxide core / cell nanoparticles produced better performance than commercially available titanium dioxide particles in the photocatalytic action under visible light, and the uniform silica / nitrogen-doped titanium dioxide core / Cell nanoparticles can be used as a next-generation high-efficiency photocatalyst used in the future industry.

In the mixed solution of ethanol and acetonitrile used in step (A), the amount of acetonitrile added is preferably 10 to 100 based on 100 parts by volume of ethanol. If the amount of acetonitrile added is 10 or less, the sol-gel reaction may proceed in the titanium dioxide precursor outside the surface of the silica nanoparticles, and if it is 100 parts by volume or more, a problem occurs in the dispersion of the silica nanoparticles.

When dispersing the silica nanoparticles on the solution, it is preferably 1 to 15 parts by weight based on 100 parts by weight of ethanol. If the amount of the silica particles used is 1 part by weight or less, a problem arises in that the manufacturing cost increases due to excessive use of the solution, and when the amount of the silica particles is 15 parts by weight or more, the core / cell nano that is finally manufactured is not completely dispersed in the ethanol solution. Particles get stuck together.

An ammonia solution is added to introduce ammonium ions onto the surface of the silica nanoparticles, and the amount of the ammonia solution may be added in an amount of 1 to 100 parts by weight based on 100 parts by weight of the silica particles, and is not limited to these ranges. Or less.

The diameter of the silica nanoparticles is not particularly limited, and is preferably 5 to 300 nanometers, and is applicable to particles of micrometer size. The shape is not limited to a specific shape, but spherical particles are preferred. In the case of silica nanoparticles, commercially available colloidal silica may be used, and silica particles of various sizes and shapes manufactured using a commonly known Stober method may be used.

The temperature at the time of dispersing the silica nanoparticles on the solution is not particularly limited, but proceeds at a temperature of 1 to 30 ° C., and the dispersion time is preferably 10 to 60 minutes.

The type of nitrogen dopant in step (B) is not limited to a specific type, triethylamine, ammonium chloride, ammonium solution, urea, thiourea, Hydrazine hydrate may be used as the dopant, and the types of titanium dioxide precursors are not limited to specific precursors, but also include titanium tetraisopropoxide, titanium butoxide, and titanium ethoxide ( Titanium ethoxide, titanium sulphate and titanium chloride may be used as precursors.

The addition amount of the titanium dioxide precursor is preferably a weight ratio of one fifth to five times that of the silica particles, but is not limited to these ranges and may be more or less than the above ranges. The addition amount of the nitrogen dopant may be added in a volume ratio of 1/10 to 5 times the titanium dioxide precursor, but is not limited to these ranges and may be more or less than the above range.

The reaction time required for the interfacial sol-gel reaction between the nitrogen dopant and the titanium dioxide precursor is preferably 3 to 24 hours, like the general sol-gel reaction, but is not limited thereto, and may be longer or shorter than the above range depending on the type of the dopant and the precursor. Can lose. The temperature required for the interfacial sol-gel reaction is preferably 3 to 50 ° C., but may be higher or lower than the above range depending on the type of dopant or precursor.

The drying temperature of the silica / nitrogen doped titanium dioxide core / cell nanoparticles in step (C) is preferably 50 to 100 ° C., but is not limited thereto, and may be higher or lower than the above range depending on the diameter or shape of the nanoparticles. Can be. The drying time is not particularly limited but is carried out for 24 to 48 hours.

Heat treatment of silica / nitrogen doped titanium dioxide core / cell nanoparticles to produce anatase-type nanocrystals to provide photoactivity, and the heat treatment temperature of the silica / nitrogen doped titanium dioxide core / cell nanoparticles is 150 to 650 ° C. is preferred, but is not limited to these ranges, and may be higher or lower than this range. The heat treatment time is not particularly limited but proceeds for 2 to 4 hours.

[Example]

Hereinafter, specific examples of the present invention will be described with reference to Examples, but the scope of the present invention is not limited thereto.

Example 1

Into 100 ml of ethanol and 30 ml of acetonitrile, 1.0 g of silica nanoparticles having a diameter of 17 nanometers and 5 ml of ammonia solution are added and dispersed for 1 hour while dispersing the silica nanoparticles and allowing the ammonium ions to adsorb onto the surface of the silica nanoparticles. . 1 ml of titanium tetraisoproxide, 2 ml of triethylamine, and 20 ml of ethanol were added to the solution, followed by stirring at room temperature for 12 hours, thereby limiting only the surface of the silica nanoparticles. Allow the interfacial sol-gel reaction to occur. The solution is dried at 100 ° C. for 48 hours and then subjected to a heat treatment at 250 ° C. for 2 hours. As a result of analyzing the prepared silica / nitrogen-doped titanium dioxide core / cell nanoparticles using a transmission electron microscope, a layer of titanium dioxide having a thickness of about 1.5 nanometers was formed on the surface of the silica nanoparticles, It was confirmed that the increase to 20 nanometers. (FIG. 1) X-ray photoelectron spectroscopy analysis also showed that the titanium dioxide layer was doped with nitrogen. As shown in FIG. 1, it was confirmed that the silica / nitrogen-doped titanium dioxide core / cell nanoparticles had a uniform size.

[Example 2]

Using the same method as in Example 1, 4 ml of titanium tetraisopropoxide and 8 ml of triethylamine were introduced to restrict the interfacial sol-gel reaction only on the surface of the silica nanoparticles. As a result of the analysis, a titanium dioxide layer of about 5 nanometers was formed, and the size of the particles was increased to 28 nanometers, and the X-ray photoelectron spectroscopy analysis confirmed that the titanium dioxide layer was doped with nitrogen. .

It can be seen that the thickness of the titanium-doped titanium dioxide layer formed on the surface of the silica nanoparticles is related to the addition amount of the titanium dioxide precursor, and that the thickness of the titanium dioxide layer becomes thicker as the amount of the titanium dioxide precursor increases. Able to know.

Example 3

Using the same method as in Example 1, using 1.0 g of 30 nanometer silica nanoparticles and introducing 4 ml of titanium tetraisopropoxide and 8 ml of triethylamine, the interface sol was limited only on the surface of the silica nanoparticles. The gel reaction occurred, and the analysis using a transmission electron microscope revealed that about 10 nanometers of titanium dioxide layer was formed, resulting in the production of 50 nanometers of silica / titanium dioxide core / cell nanoparticles. X-ray photoelectron spectroscopy analysis showed that the titanium dioxide doped with nitrogen.

Example 4

Using the same method as in Example 1, using 1.0 g of 75 nanometer silica nanoparticles and introducing 4 ml of titanium tetraisopropoxide and 8 ml of triethylamine, the interface sol was limited only on the surface of the silica nanoparticles. The gel reaction occurred, and the analysis using a transmission electron microscope revealed that a 12.5 nanometer titanium dioxide layer was formed, resulting in the production of 100 nanometer silica / titanium dioxide core / cell nanoparticles. Photoelectron spectroscopy analysis confirmed that the nitrogen doped with titanium dioxide.

Example 5

Using the same method as in Example 1, 1 ml of triethylamine was introduced, and the interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. Titanium dioxide layer was formed, it was confirmed that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and the nitrogen dioxide doped less nitrogen than the product of Example 1 through the X-ray photoelectron spectroscopy analysis I could confirm that.

It can be seen that the amount of nitrogen doped in titanium dioxide is related to the addition amount of nitrogen dopant, and as the amount of nitrogen dopant increases, the amount of nitrogen doped in titanium dioxide increases.

Example 6

The silica / titanium dioxide core / cell nanoparticles prepared by the same method as in Example 1 were heat-treated at 550 ° C., and analyzed using a transmission electron microscope to form a 1.5 nanometer titanium dioxide layer. It could be confirmed that the silica / titanium dioxide core / cell nanoparticles of the meter were generated, and nitrogen was doped into the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 7

In the same manner as in Example 1, 2 ml of ammonium chloride was introduced and a limited interfacial sol-gel reaction occurred on the surface of the silica nanoparticles. As a result of analysis using a transmission electron microscope, about 1.5 nanometers of dioxide was obtained. Titanium layer was formed, it was confirmed that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, the nitrogen doped to the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 8

Using the same method as in Example 1, 2 ml of ammonia solution was introduced and the interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. Titanium layer was formed, it was confirmed that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, the nitrogen doped to the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 9

Using the same method as in Example 1, 2 ml of urea was introduced and limited interfacial sol-gel reaction occurred on the surface of silica nanoparticles. As a result of analysis using a transmission electron microscope, about 1.5 nanometers of titanium dioxide A layer was formed to confirm that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and it was confirmed that nitrogen was doped with titanium dioxide through X-ray photoelectron spectroscopy analysis.

Example 10

Using the same method as in Example 1, 2 ml of thiourea was introduced and a limited interface sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. Titanium dioxide layer was formed, it was confirmed that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and the nitrogen doped to the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 11

Using the same method as in Example 1, 2 ml of hydrazine hydrate was introduced and a limited interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. Titanium layer was formed, it was confirmed that 20 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, the nitrogen doped to the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 12

Using the same method as in Example 1, 1 ml of titanium butoxide was introduced, and a limited interfacial sol-gel reaction occurred on the surface of silica nanoparticles, and analyzed using a transmission electron microscope. Titanium dioxide layer was formed, it was confirmed that the 22 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and the nitrogen doped to the titanium dioxide through the X-ray photoelectron spectroscopy analysis.

Example 13

Using the same method as in Example 1, 1 ml of titanium oxysulfate was introduced and a limited interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. The titanium dioxide layer was formed to confirm that 27 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and it was confirmed that nitrogen was doped with titanium dioxide through X-ray photoelectron spectroscopy analysis.

Example 14

1 ml of titanium ethoxysite was introduced using the same method as in Example 1, and the interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. The titanium dioxide layer was formed to confirm that 30 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and it was confirmed that nitrogen was doped with titanium dioxide through X-ray photoelectron spectroscopy analysis.

Example 15

1 ml of titanium chloride was introduced using the same method as in Example 1, and the interfacial sol-gel reaction occurred on the surface of the silica nanoparticles, and analyzed using a transmission electron microscope. Titanium layer was formed to confirm that the 25 nanometers of silica / titanium dioxide core / cell nanoparticles were produced, and through the X-ray photoelectron spectroscopy analysis it was confirmed that the nitrogen doped with titanium dioxide.

Example 16

When 20 ml of 15 ppm methylene blue solution was decomposed under visible light using the uniform silica / nitrogen doped titanium dioxide nanoparticles prepared in Example 1 at a concentration of 0.5 g / L, 7 After hours, the concentration of methylene blue solution was confirmed to be 1 ppm. (Fig. 3)

1 is a transmission electron micrograph of the uniform silica / nitrogen doped titanium oxide core / cell nanoparticles prepared in Example 1 of the present invention;

FIG. 2 is an X-ray photoelectron spectroscopy analysis of the uniform silica / nitrogen doped titanium oxide core / cell nanoparticles prepared in Example 2 of the present invention; FIG.

Figure 3 is the methylene blue decomposition results with time under visible light of the uniform silica / nitrogen doped titanium oxide core / cell nanoparticles prepared in Example 1 of the present invention.

Claims (9)

(A) dispersing the silica nanoparticles in ethanol, acetonitrile, ammonia solution mixed solution; (B) adding a nitrogen dopant and a titanium dioxide precursor to the dispersion solution so that the interfacial sol-gel reaction occurs only on the surface of the silica nanoparticles into which ammonium ions are introduced; (C) a method for producing uniform silica / nitrogen-doped titanium dioxide core / cell nanoparticles, comprising: drying the dispersion solution and subjecting it to heat so that nitrogen is efficiently doped into titanium dioxide crystals. . The method of claim 1, wherein the size of the silica nanoparticles are several nanometers to several micrometers in size. The method according to claim 1, wherein the titanium dioxide precursor is titanium tetraisopropoxide, titanium butoxide, titanium ethoxide, titanium oxysulfate, titanium chloride. The process according to claim 1, wherein the nitrogen dopant is triethylamine, ammonium chloride, ammonia solution, urea, thiourea, hydrazine hydrate. The method according to claim 1, wherein the added amount of the titanium dioxide precursor is a weight ratio of one fifth to five times the silica nanoparticles. The method according to claim 1, wherein the addition amount of the nitrogen dopant is 1 to 5 times the weight ratio of the titanium dioxide precursor. The method according to claim 1, wherein the interfacial sol-gel reaction temperature is from 3 ° C to 60 ° C. The process according to claim 1, wherein the interfacial sol-gel reaction time is from 1 hour to 24 hours. The method according to claim 1, wherein the heat treatment temperature is 150 ° C to 650 ° C.

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