Manufacturing method for nanoparticles including cobalt oxide nanosheets and nanoparticle manufactured thereby

Abstract

The present invention relates to nanoparticles comprising cobalt oxide nanosheets that are easy to manufacture, environmentally friendly, and capable of efficiently removing or converting nitro group-containing aromatic compounds, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing nanoparticles comprising cobalt oxide nanosheets and nanoparticles manufactured thereby. Background Technology

[0003] With the rapid development of the pharmaceutical, chemical, and related industries, hazardous organic chemical waste is becoming a significant cause of environmental pollution. 4-nitrophenol (4-NP), one of these hazardous organic chemical wastes, is commonly used in various industries such as textiles, dyeing, and plastics; it is highly toxic and associated with health problems including vascular disorders, nervous system damage, eye inflammation, skin allergies, and respiratory issues. The U.S. Environmental Protection Agency (EPA) recommends an acceptable limit of up to 0.43 μM or 60 μg / L for 4-nitrophenol and classifies it as a priority pollutant. Due to the harmful effects of 4-nitrophenol, technological research is being conducted to convert it into less harmful substances, such as 4-aminophenol (4-AP), which can be applied in the pharmaceutical, medical, and photographic industries. Conventionally, catalysts containing precious metals such as platinum, ruthenium, palladium, and gold have been used to reduce 4-nitrophenol. However, catalysts containing precious metals have a problem in that their use is limited due to high costs and complex synthesis processes.

[0004] Therefore, there is a need to develop technology that can effectively and environmentally remove or convert harmful chemicals such as 4-nitrophenol. The problem to be solved

[0006] The present invention provides nanoparticles capable of removing or converting nitro group-containing aromatic compounds in an easy, environmentally friendly, and efficient manner, and a method for manufacturing the same.

[0007] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0009] One embodiment of the present invention provides a method for producing nanoparticles comprising: a step of preparing a mixture comprising a cobalt precursor and polyacrylonitrile; and a step of heat-treating the mixture to produce nanoparticles comprising cobalt oxide nanosheets.

[0010] According to one embodiment of the present invention, the cobalt precursor may include a cobalt hydrate.

[0011] According to one embodiment of the present invention, the weight-average molecular weight of the polyacrylonitrile may be 50,000 g / mol or more and 300,000 g / mol or less.

[0012] According to one embodiment of the present invention, the content of the cobalt precursor in the mixture may be 0.01 parts by weight or more and 1.0 parts by weight or less with respect to 100 parts by weight of the polyacrylonitrile.

[0013] According to one embodiment of the present invention, the heat treatment step may be performed at a heating rate of 1 ℃ / min or more and 20 ℃ / min or less, at a temperature of 200 ℃ or more and 800 ℃ or less.

[0014] According to one embodiment of the present invention, the heat treatment step may be performed for a period of time of 10 minutes or more and 10 hours or less.

[0015] One embodiment of the present invention provides nanoparticles produced by the method for producing nanoparticles.

[0016] According to one embodiment of the present invention, the nanoparticles are Co calculated through XPS spectrum results 3+ / Co 2+The atomic concentration ratio of can be 0.3 or higher and 0.5 or lower.

[0017] According to one embodiment of the present invention, the nanoparticles may have an average size of 10 nm or more and 150 nm or less.

[0018] According to one embodiment of the present invention, the nanoparticles have an average pore volume of 0.05 cm² 3 / g or more than 1.0 cm 3 It can be / g.

[0019] According to one embodiment of the present invention, the nanoparticles may be a catalyst that converts a nitro group-containing aromatic compound into an amine group-containing aromatic compound. Effects of the invention

[0021] A method for manufacturing nanoparticles according to one embodiment of the present invention comprises the ratio of the (311) plane and the (440) plane of cobalt oxide and Co 3+ Wa Co 2+ Nanoparticles can be easily manufactured by efficiently controlling the atomic ratio of.

[0022] Nanoparticles according to one embodiment of the present invention can efficiently convert nitro group-containing aromatic compounds.

[0023] The effects of the present invention are not limited to those described above, and unmentioned effects will be clearly understood by those skilled in the art from the present specification and the accompanying drawings. Brief explanation of the drawing

[0025] Figure 1 is an FE-SEM image of each nanoparticle prepared in Examples 1 to 3 of the present invention. Figure 2 is an XRD graph of each nanoparticle prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 3 is a graph of the Co 2p spectrum of each nanoparticle prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 4 is an N2 adsorption-desorption isotherm graph and BJH plot of each nanoparticle prepared in Examples 1 to 3 and Comparative Example 1 of the present invention. FIG. 5 is a graph of the UV-visible spectrum as each nanoparticle of Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention is introduced into a 4-nitrophenol solution. FIG. 6 shows the apparent velocity constants in Reference Examples 1 to 3, Reference Comparative Example 1 and Reference Comparative Example 2 of the present invention ( k app This is a graph representing ). Figure 7 is a graph of the UV-visible spectrum and reduction efficiency according to the concentration of NaBH4 included in the mixed solution of Reference Example 2 of the present invention. FIG. 8 shows the UV-visible spectrum and apparent rate constant according to the nanoparticle content of Example 2 of the present invention ( k app It is a graph. Figure 9 is a graph of the UV-visible spectrum according to the cycle in which the nanoparticles of Example 2 of the present invention are introduced into a 4-nitrophenol solution. FIG. 10 is a graph of reduction efficiency and apparent rate constant according to the cycle in which the nanoparticles of Example 2 of the present invention are introduced into a 4-nitrophenol solution ( k app It is a graph. Figure 11 is an FE-SEM image and XRD graph after the 6th cycle following the introduction of the nanoparticles of Example 2 of the present invention into a 4-nitrophenol solution. Figure 12 is a UV-visible spectrum graph according to the type of nitro group-containing aromatic compound into which the nanoparticles of Example 2 of the present invention are introduced. Figure 13 is a UV-visible spectrum of each nanoparticle of Example 4 and Comparative Example 6 of the present invention introduced into a 4-nitrophenol solution. FIG. 14 is a graph of the hydrogen generation rate after each nanoparticle of Example 2, Example 4, Comparative Example 1, and Comparative Example 6 of the present invention is introduced into a 4-nitrophenol solution. FIG. 15 is a graph of the hydrogen generation rate and 4-nitrophenol reduction efficiency after each nanoparticle of Example 2, Example 4, Comparative Example 1, and Comparative Example 6 of the present invention is introduced into a 4-nitrophenol solution. Specific details for implementing the invention

[0026] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0027] Throughout this specification, when a component is described as being located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0028] Throughout the entire specification, the unit "parts by weight" may refer to the ratio of weight between each component.

[0029] Throughout the entire specification, "at least one of a, b and c" may include a, b, or c alone, or two or more combinations selected from the group consisting of a, b, and c.

[0030] Throughout this specification, the “weight-average molecular weight” and “number-average molecular weight” of a compound can be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, a sample with a compound concentration of 1 wt% is prepared by placing tetrahydrofuran (THF) and the compound in a 1 ml glass vial. After filtering the standard sample (polystyrene) and the sample through a filter (pore size 0.45 μm), the sample is injected into a GPC injector, and the molecular weight and molecular weight distribution of the compound can be obtained by comparing the elution time of the sample with the calibration curve of the standard sample. At this time, an Infinity II 1260 (Agilient) can be used as the measuring instrument, and the flow rate can be set to 1.00 mL / min and the column temperature to 40.0 ℃.

[0031] Throughout this specification, the “size” of nanoparticles may mean “particle diameter.”

[0033] The present specification will be described in more detail below.

[0034] One embodiment of the present invention provides a method for producing nanoparticles comprising: a step of preparing a mixture comprising a cobalt precursor and polyacrylonitrile; and a step of heat-treating the mixture to produce nanoparticles comprising cobalt oxide nanosheets.

[0035] A method for manufacturing nanoparticles according to one embodiment of the present invention comprises the ratio of the (311) plane and the (440) plane of cobalt oxide and Co 3+ Wa Co 2+ Nanoparticles can be easily manufactured by efficiently controlling the atomic ratio of.

[0036] A mixture according to one embodiment of the present invention comprises a cobalt precursor. As described above, by including a cobalt precursor in the mixture, nanoparticles capable of easily reducing nitro group-containing aromatic compounds can be effectively produced.

[0037] According to one embodiment of the present invention, the cobalt precursor may include a cobalt hydrate. Specifically, the cobalt precursor may include a hydrate of a cobalt-containing organic compound. More specifically, the cobalt precursor may include a cobalt acetate tetrahydrate. The cobalt precursor in the form of a hydrate may be stably present in the mixture and may be mixed more homogeneously with polyacrylonitrile. As described above, by including a cobalt hydrate in the cobalt precursor, cobalt oxide nanosheets can be stably formed. In addition, by using a cobalt hydrate as the cobalt precursor, the (440) plane of the cobalt oxide can be efficiently exposed in the nanosheets produced.

[0038] A mixture according to one embodiment of the present invention comprises polyacrylonitrile. As described above, by including polyacrylonitrile in the mixture, a nanosheet structure of the cobalt oxide being manufactured can be easily formed and the (440) plane of the cobalt oxide can be efficiently exposed.

[0039] According to one embodiment of the present invention, the weight-average molecular weight of the polyacrylonitrile may be 50,000 g / mol or more and 300,000 g / mol or less. Specifically, the weight-average molecular weight of the polyacrylonitrile is 50,000 g / mol or more and 250,000 g / mol or less, 50,000 g / mol or more and 200,000 g / mol or less, 50,000 g / mol or more and 100,000 g / mol or less, 70,000 g / mol or more and 300,000 g / mol or less, 70,000 g / mol or more and 250,000 g / mol or less, 70,000 g / mol or more and 200,000 g / mol or less, 70,000 g / mol or more and 100,000 g / mol or less, 100,000 g / mol or more and 300,000 g / mol or less, 100,000 g / mol or more and 250,000 g / mol or less, or 100,000 g / mol It may be greater than or equal to 200,000 g / mol. By controlling the weight-average molecular weight of polyacrylonitrile to the aforementioned range, the pore diameter, pore volume, and pore concentration of the nanoparticles produced can be controlled.

[0040] According to one embodiment of the present invention, the content of the cobalt precursor in the mixture may be 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the polyacrylonitrile. Specifically, the content of the cobalt precursor with respect to 100 parts by weight of the polyacrylonitrile may be 1 part by weight or more and 180 parts by weight or less, 1 part by weight or more and 150 parts by weight or less, 1 part by weight or more and 125 parts by weight or less, 5 parts by weight or more and 200 parts by weight or less, 5 parts by weight or more and 180 parts by weight or less, 5 parts by weight or more and 150 parts by weight or less, 5 parts by weight or more and 125 parts by weight or less. When the content of the polyacrylonitrile and the cobalt precursor included in the above mixture is within the aforementioned range, the pore diameter of the nanoparticles can be controlled and the (440) plane of the cobalt oxide can be efficiently exposed.

[0041] According to one embodiment of the present invention, the heat treatment step may be performed at a heating rate of 1 ℃ / min or more and 20 ℃ / min or less, at a temperature of 200 ℃ or more and 800 ℃ or less. Specifically, the heating rate of the heat treatment step may be 1 ℃ / min or more and 15 ℃ / min or less, 1 ℃ / min or more and 10 ℃ / min or less, 1 ℃ / min or more and 5 ℃ / min or less, 2 ℃ / min or more and 20 ℃ / min or less, 2 ℃ / min or more and 15 ℃ / min or less, 2 ℃ / min or more and 10 ℃ / min or less, 2 ℃ / min or more and 5 ℃ / min or less, 5 ℃ / min or more and 20 ℃ / min or less, 5 ℃ / min or more and 15 ℃ / min or less, or 5 ℃ / min or more and 10 ℃ / min or less. In addition, the temperature of the heat treatment step may be 200 ℃ or higher and 700 ℃ or lower, 200 ℃ or higher and 600 ℃ or lower, 200 ℃ or higher and 500 ℃ or lower, 300 ℃ or higher and 800 ℃ or lower, 300 ℃ or higher and 700 ℃ or lower, 300 ℃ or higher and 600 ℃ or lower, 300 ℃ or higher and 500 ℃ or lower, 400 ℃ or higher and 800 ℃ or lower, 400 ℃ or higher and 700 ℃ or lower, 400 ℃ or higher and 600 ℃ or lower, 400 ℃ or higher and 500 ℃ or lower, 500 ℃ or higher and 800 ℃ or lower, 500 ℃ or higher and 700 ℃ or lower, or 500 ℃ or higher and 600 ℃ or lower. By controlling the heating rate and temperature of the above heat treatment step to the aforementioned range, cobalt oxide nanosheets can be easily manufactured.

[0042] According to one embodiment of the present invention, the heat treatment step may be performed for a period of time from 10 minutes to 10 hours. Specifically, the time of the heat treatment step may be from 10 minutes to 8 hours, from 10 minutes to 5 hours, from 10 minutes to 3 hours, from 30 minutes to 10 hours, from 30 minutes to 8 hours, from 30 minutes to 5 hours, from 30 minutes to 3 hours, from 1 hour to 10 hours, from 1 hour to 8 hours, from 1 hour to 5 hours, from 1 hour to 3 hours, from 3 hours to 10 hours, from 3 hours to 8 hours, or from 3 hours to 5 hours. By adjusting the time of the heat treatment step to the aforementioned range, cobalt oxide nanosheets can be stably formed.

[0043] According to one embodiment of the present invention, the method for manufacturing the nanoparticles may further include a step of performing a second heat treatment on the nanoparticles. At this time, the second heat treatment may be performed under the same conditions as the heat treatment of the mixture. By performing the second heat treatment on the nanoparticles, hydrogen generation can be reduced and hydrogen protons can be retained, thereby achieving higher efficiency in the reduction reaction.

[0044] According to one embodiment of the present invention, the cobalt oxide nanosheet may include Co3O4, Co2O3, and CoO. By selecting the type of cobalt oxide nanosheet as described above, the nanoparticles can easily reduce nitro group-containing aromatic compounds.

[0046] One embodiment of the present invention provides nanoparticles produced by the method for producing nanoparticles.

[0047] Nanoparticles according to one embodiment of the present invention can efficiently convert nitro group-containing aromatic compounds.

[0048] The above nitro group-containing aromatic compounds may include 4-nitrophenol (4-nitrophenol, 4-NP), 2-nitrophenol (2-nitrophenol, 2-NP), 3-nitrobenzaldehyde (3-nitrobenzaldehyde, 3-NBA), and 4-nitroaniline (4-nitroaniline, 4-NA).

[0049] According to one embodiment of the present invention, the nanoparticles may have a ratio of (311) / (440) of 1.0 or higher and 1.3 or lower in the XRD analysis results. Nanoparticles in which the ratio of (311) / (440) in the XRD analysis results satisfies the aforementioned range can achieve excellent reducing properties.

[0050] According to one embodiment of the present invention, the nanoparticles are Co 3+ The surface atomic concentration of can be between 10% and 35%. As described below, through the analysis of the Co 2p peak area of ​​the XPS spectrum, the Co of the nanoparticles 3+ The surface atomic concentration of can be calculated. That is, in the XPS analysis results, the above nanoparticles Co through the Co 2p peak area 3+ The surface atomic concentration of may be 10% or more and 35% or less. Specifically, the Co of the nanoparticles 3+ The surface atomic concentration of may be 10% or more and 33% or less, 10% or more and 31% or less, 15% or more and 35% or less, 15% or more and 33% or less, 15% or more and 31% or less, 20% or more and 35% or less, 20% or more and 33% or less, 20% or more and 31% or less, 25% or more and 35% or less, 25% or more and 33% or less, or 25% or more and 31% or less. In the XPS analysis results, Co through the Co 2p peak area 3+ Nanoparticles whose surface atomic concentration satisfies the aforementioned range can achieve excellent reducing properties.

[0051] According to one embodiment of the present invention, the nanoparticles are Co 2+ The surface atomic concentration of can be between 65% and 90%. That is, in the XPS analysis results, the above nanoparticles Co through the Co 2p peak area 2+ The surface atomic concentration of may be 65% or more and 90% or less. Specifically, the Co of the nanoparticles 3+ The surface atomic concentration of may be 67% or more and 90% or less, 69% or more and 90% or less, 65% or more and 85% or less, 67% or more and 85% or less, 69% or more and 85% or less, 65% or more and 80% or less, 67% or more and 80% or less, 69% or more and 80% or less, 65% or more and 75% or less, or 69% or more and 75% or less. In the XPS analysis results, Co through the Co 2p peak area 2+ Nanoparticles whose surface atomic concentration satisfies the aforementioned range can achieve excellent reducing properties.

[0052] According to one embodiment of the present invention, the nanoparticles are Co calculated through XPS spectrum results 3+ / Co 2+ The atomic concentration ratio of can be between 0.3 and 0.5. In the spectral curve of nanoparticles analyzed using XPS, the Co calculated through the Co 2p peak area 3+ The surface atomic concentration of and Co 2+ The ratio of surface atomic concentration (Co 3+ / Co 2+ ) may be 0.3 or more and 0.5 or less. Specifically, the Co of the above nanoparticles 3+ / Co 2+The ratio may be 0.3 or more and 0.47 or less, 0.3 or more and 0.45 or less, 0.35 or more and 0.5 or less, 0.35 or more and 0.47 or less, 0.35 or more and 0.45 or less, 0.4 or more and 0.5 or less, 0.4 or more and 0.47 or less, or 0.4 or more and 0.45 or less. In the above XPS analysis results, Co through the Co 2p peak area 3+ / Co 2+ Nanoparticles satisfying the aforementioned range in terms of ratio can achieve excellent reducing properties.

[0053] According to one embodiment of the present invention, the nanoparticles may have an average size of 10 nm or more and 150 nm or less. Specifically, the average size of the nanoparticles may be 10 nm or more and 140 nm or less, 10 nm or more and 120 nm or less, 10 nm or more and 100 nm or less, 20 nm or more and 150 nm or less, 20 nm or more and 140 nm or less, 20 nm or more and 120 nm or less, 20 nm or more and 100 nm or less, 40 nm or more and 150 nm or less, 40 nm or more and 140 nm or less, 40 nm or more and 120 nm or less, or 40 nm or more and 100 nm or less. Nanoparticles with an average size satisfying the aforementioned range may have excellent structural stability and reduction efficiency.

[0054] According to one embodiment of the present invention, the nanoparticle may have an average pore diameter of 100 nm or more and 3,000 nm or less. Specifically, the average pore diameter of the nanoparticle may be 100 nm or more and 2,700 nm or less, 100 nm or more and 2,500 nm or less, 100 nm or more and 2,300 nm or less, 120 nm or more and 3,000 nm or less, 120 nm or more and 2,700 nm or less, 120 nm or more and 2,500 nm or less, 120 nm or more and 2,300 nm or less, 140 nm or more and 3,000 nm or less, 140 nm or more and 2,700 nm or less, 140 nm or more and 2,500 nm or less, or 140 nm or more and 2,300 nm or less. Nanoparticles with an average pore diameter satisfying the aforementioned range may have excellent structural stability and reduction efficiency.

[0055] According to one embodiment of the present invention, the nanoparticles have an average pore volume of 0.05 cm² 3 / g or more than 1.0 cm 3 It may be / g. Specifically, the average pore volume of the nanoparticles is 0.05 cm³ 3 / g or more 0.8 cm 3 / g or less, 0.05 cm 3 / g or more 0.6 cm 3 / g or less, 0.05 cm 3 / g or more 0.5 cm 3 / g or less, 0.1 cm 3 / g or more than 1.0 cm 3 / g or less, 0.1 cm 3 / g or more 0.8 cm 3 / g or less, 0.1 cm 3 / g or more 0.6 cm 3 / g or less, 0.1 cm 3 / g or more 0.5 cm 3 / g or less, 0.15 cm 3 / g or more than 1.0 cm 3 / g or less, 0.15 cm 3 / g or more 0.8 cm3 / g or less, 0.15 cm 3 / g or more 0.6 cm 3 / g or less or 0.15 cm 3 / g or more 0.5 cm 3 It may be less than / g. Nanoparticles with an average pore volume satisfying the aforementioned range may have excellent structural stability and reduction efficiency.

[0056] According to one embodiment of the present invention, the nanoparticles may be a catalyst that converts a nitro group-containing aromatic compound into an amine group-containing aromatic compound.

[0058] One embodiment of the present invention may provide a system for converting a nitro group-containing aromatic compound into an amine group-containing aromatic compound using the nanoparticles. As described above, the nanoparticles can effectively reduce nitro groups to amine groups by satisfying specific physical properties.

[0059] According to one embodiment of the present invention, a reducing agent may be included in a reaction system for converting the nitro group-containing aromatic compound into an amine group-containing aromatic compound. The reducing agent may include NaBH4, H2, Na2S2O4, Zn / HCl, Fe / H2O, and L-ascorbic acid. By using a reducing agent of the aforementioned type, the nitro group-containing aromatic compound can be efficiently reduced.

[0060] According to one embodiment of the present invention, the system may have a nanoparticle content of 0.05 mg / mL or more and 0.5 mg / mL or less, 0.06 mg / mL or more and 0.3 mg / mL or less, 0.1 mg / mL or more and 0.2 mg / mL or less, 0.05 mg / mL or more and 0.2 mg / mL or less, or 0.15 mg / mL or more and 0.3 mg / mL or less. Specifically, the content of the nanoparticles contained in a reaction solution comprising a substance to be reduced, a reducing agent, and the nanoparticles may be 0.05 mg / mL or more and 0.5 mg / mL or less. When the content of the nanoparticles is within the aforementioned range, the system can effectively convert a nitro group-containing aromatic compound into an amine group-containing aromatic compound.

[0061] According to one embodiment of the present invention, the efficiency of reducing a nitro group-containing aromatic compound of the nanoparticles to an amine group-containing aromatic compound may be 80% or more and 100% or less. Specifically, the efficiency of reducing a nitro group-containing aromatic compound of the nanoparticles to an amine group-containing aromatic compound may be 80% or more and 99% or less, 85% or more and 100% or less, 85% or more and 99% or less, 90% or more and 100% or less, or 90% or more and 99% or less.

[0063] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0065] ingredient

[0066] Cobalt (II) acetate tetrahydrate (Co(CH3CO2)2·4H2O, 98%; Sigma-Aldrich), polyacrylonitrile (PAN, Mw: 150,000 g / mol; Sigma-Aldrich), sodium borohydride (NaBH4, 99%; ACROS ORGANICS), 4-nitrophenol (4-NP, ≥99%; Sigma-Aldrich), and commercial cobalt (III) oxide (Co3O4, 99.7%; Alfa Aesar) were prepared.

[0068] Preparation of nanoparticles containing cobalt oxide nanosheets

[0069] Example 1

[0070] 0.05 g of cobalt(II) acetate tetrahydrate and 0.4 g of polyacrylonitrile were mixed and ground with a mortar and pestle to prepare a homogeneous mixture.

[0071] Subsequently, the mixture was annealed in an atmospheric environment at a temperature of 500 ℃ at a heating rate of 5 ℃ / min for 3 hours to obtain nanoparticles.

[0073] Example 2

[0074] Nanoparticles were obtained in the same manner as in Example 1, except that the amount of cobalt(II) acetate tetrahydrate was adjusted to 0.25 g.

[0076] Example 3

[0077] Nanoparticles were obtained in the same manner as in Example 1, except that the amount of cobalt(II) acetate tetrahydrate was adjusted to 0.5 g and the amount of polyacrylonitrile to 0.8 g in Example 1.

[0079] Comparative Example 1

[0080] 1.3 g of cobalt(II) acetate tetrahydrate-polyacrylonitrile nanofibers were annealed at 500°C in air using electrospinning with a rotational voltage of 18 kV to obtain nanoparticles characterized by having (220) planes exposed.

[0082] Comparative Example 2

[0083] 1 g of commercial cobalt(III) oxide (Co3O4, 99.7%; Alfa Aesar) was prepared.

[0085] Comparative Example 3

[0086] Nanoparticles were obtained in the same manner as in Example 1, except that 0.5 g of polyvinyl alcohol was mixed instead of polyacrylonitrile in Example 1.

[0088] Comparative Example 4

[0089] Nanoparticles were obtained in the same manner as in Example 1, except that 0.75 g of polyethylene glycol was mixed instead of polyacrylonitrile in Example 1.

[0091] Comparative Example 5

[0092] Nanoparticles were obtained in the same manner as in Example 1, except that 1.1 g of polyvinylpyrrolidone was mixed instead of polyacrylonitrile in Example 1.

[0094] Experimental Example

[0095] 1. Analysis of nanoparticle shape and size

[0096] Images of nanoparticles were obtained using a field emission scanning electron microscope (FE-SEM, S-2400, Hitachi), and data on the morphology and size of the nanoparticles were obtained through the acquired images.

[0097] Figure 1 is an FE-SEM image of each nanoparticle prepared in Examples 1 to 3 of the present invention. Specifically, Figure 1 (A-1) and (A-2) show the nanoparticle prepared in Example 1 magnified 50,000 times and 100,000 times, respectively, confirming that the average particle size of the nanoparticle in Example 1 is 72 nm. Figure 1 (B-1) and (B-2) show the nanoparticle prepared in Example 2 magnified 10,000 times and 100,000 times, respectively. As shown in (B-1), nanosheets were formed, and it was observed that the spacing between each nanosheet was narrower. As shown in (B-2), it was confirmed that the average particle size of the nanoparticle in Example 2 is 50 nm. Figures (C-1) and (C-2) of Fig. 1 show the nanoparticles prepared in Example 3 magnified 10,000 times and 100,000 times, respectively. As seen in (C-1), nanosheets were formed, and it was observed that the spacing between each nanosheet was wider. As seen in (C-2), it was confirmed that the average particle size of the nanoparticles in Example 3 was 96 nm.

[0099] 2. Analysis of Nanoparticle Crystallinity

[0100] The crystal structure of the nanoparticles was analyzed using a D8 ADVANCE X-ray diffraction (XRD) equipped with a diffractometer using a Cu Kα radiation (1.54 Å) source operating at 40 kV and 40 mA with a 2θ range of (10 - 90)°.

[0101] FIG. 2 is an XRD graph of each nanoparticle prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention. Specifically, FIG. 2 is an XRD graph of nanoparticles prepared in Example 1 (P-0.05-500), Example 2 (P-0.25-500), Example 3 (P-0.5-500), Comparative Example 1 (Es-18-500), and Comparative Example 2 (Comm.Co3O4).

[0102] As shown in Fig. 2, 2θ values ​​of 19.00°, 31.27°, 36.872°, 44.81°, 59.36°, and 65.24° were observed as diffraction peaks designated by Miller indices (hkl) as (111), (220), (311), (400), (511), and (440).

[0103] Table 1 below shows the intensity of the main peaks in Figure 2 above and their ratio values.

[0105] Peak intensity Peak intensity ratio (311) (220) (440) (311) / (220) (311) / (440) Example 1 8799.34 7039.47 6984.41 1.25 1.26 Example 2 9098.36 7314.57 8123.53 1.25 1.12 Example 3 9133.77 7249.02 7191.68 1.26 1.27 Comparative Example 1 13,896.27 11,206.67 10,527.47 1.24 1.32 Comparative Example 2 13,349.82 9548.39 9649.71 1.41 1.38

[0107] As shown in Table 1, Examples 1 to 3 showed a peak intensity ratio of (311) / (440) of 1.0 or higher and 1.3 or lower, confirming that the (311) plane and (440) plane were uniformly distributed. On the other hand, Comparative Examples 1 and 2 showed a peak intensity ratio of (311) / (440) of 1.32 or higher, confirming that the (311) plane was more dominant than in Examples 1 to 3.

[0109] 3. Analysis of the surface chemical state of nanoparticles

[0110] Co 2p data of nanoparticles measured using X-ray photoelectron spectroscopy (XPS; VG Scientific ESCALAB 250) equipped with monochromatic Al-Ka radiation of 1486.6 eV were analyzed by presenting them as core spectra.

[0111] FIG. 3 is a graph of the Co 2p spectrum of each nanoparticle prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention. Specifically, FIG. 3 is a graph of the Co 2p spectrum of nanoparticles prepared in Example 1 (P-0.05-500), Example 2 (P-0.25-500), Example 3 (P-0.5-500), Comparative Example 1 (Es-18-500), and Comparative Example 2 (Comm.Co3O4).

[0112] As shown in FIG. 3, in Examples 1 to 3, Comparative Example 1, and Comparative Example 2, Co 2p 3 / 2 and Co 2p 1 / 2Two distinct peaks and two spin-orbit doublets were identified at approximately 778.89 eV and 793.54 eV, corresponding to . From the difference of approximately 14.65 eV between the peaks, Co in the nanoparticles 2+ and Co 3+ It can be seen that all of them are included.

[0113] Table 2 below shows Co from the XPS peak spectrum fitting region of Fig. 3. 2+ and Co 3+ This represents the calculated value of the surface atomic concentration ratio.

[0115] Co 3+ (%) Co 2+ (%) What 3+ / What 2+ Example 1 29.55 70.45 0.41 Example 2 30.08 69.92 0.43 Example 3 28.02 71.98 0.39 Comparative Example 2 38 62 0.61

[0117] As shown in FIG. 3 and Table 2 above, Examples 1 to 3 are Co 3+ The surface atomic concentration of is 35% or less and Co 2+ The surface atomic concentration of is over 65%, and Co 3+ / Co 2+ It can be confirmed that the ratio is 0.60 or less. On the other hand, Comparative Example 2 is Co 3+ The surface atomic concentration of is 38% and Co 2+ The surface atomic concentration of is 62%, and Co 3+ / Co 2+ It was confirmed that the ratio was 0.61. That is, Examples 1 to 3 are Co 3+ / Co 2+ It was confirmed that the ratio satisfies the range of 0.3 or more and 0.5 or less, but Comparative Example 2 falls outside the above range.

[0119] 4. Analysis of the microstructure of nanoparticles

[0120] The microstructure of the nanoparticles was analyzed using the Brunauer-Emmett-Teller (BET) method based on N2 adsorption-desorption isotherms obtained using the BELSORP-Max (BELL Japan Inc.) instrument.

[0121] FIG. 4 is an N2 adsorption-desorption isotherm graph and BJH plot of each nanoparticle prepared in Examples 1 to 3 and Comparative Example 1 of the present invention. Specifically, (a1), (b1), (c1), and (d1) of FIG. 4 are N2 adsorption-desorption isotherm graphs of nanoparticles prepared in Example 1 (P-0.05-500), Example 2 (P-0.25-500), Example 3 (P-0.5-500), and Comparative Example 1 (Es-18-500), respectively, and (a2), (b2), (c2), and (d2) of FIG. 4 are BJH (Barett-Joyner-Halenda) plots calculated based on the data of each isotherm graph.

[0122] As shown in (a1), (b1), (c1), and (d1) of FIG. 4, it can be seen that Examples 1 to 3 and Comparative Example 1 exhibit a Type III pattern with H3 hysteresis loops. In particular, in the case of Example 2 in FIG. 4 (b1), it was confirmed that the hysteresis loop was higher in the p / po range of 0.4 to 0.9 compared to Examples 2, 3, and Comparative Example 1. This implies multiple adsorption and may mean that the concentrations of intermediate pores and macropores are higher. Additionally, by referring to (a2), (b2), (c2), and (d2) of FIG. 4, the average pore diameters of Examples 1 to 3 and Comparative Example 1 can be determined and are shown in Table 3 below.

[0124] Average pore diameter (nm) Pore ​​volume (cm²) 3 / g) Example 1 556.23 0.1987 Example 2 2178.1 0.469 Example 3 145.63 0.1875 Comparative Example 2 60.81 0.0858

[0126] As shown in FIG. 4 and Table 3 above, the average pore diameter of Examples 1 to 3 is 100 nm or more, and the pore volume is 0.1 cm³. 3 While / g or greater, the average diameter of Comparative Example 2 is 60.81 nm and the pore volume is 0.0858 cm³ 3 It was calculated to be / g.

[0128] Reference Example 1

[0129] A mixed solution was prepared by adding 0.1 mg of the nanoparticles prepared in Example 1, 1.5 mL of 0.1 M NaBH4, and 1.5 mL of 0.1 mM 4-nitrophenol (4-NP) solution to a cuvette.

[0131] Reference Example 2, Reference Example 3, Reference Comparative Example 1, Reference Comparative Example 2, Reference Example 1 and Reference Example 2

[0132] As shown in Table 4 below, a mixed solution was prepared by adjusting the volume of 4-nitrophenol, the volume of NaBH4, the type of nanoparticles, and the content of nanoparticles.

[0134] Volume of 0.1 mM 4-NP Volume of 0.1 M NaBH4 Types of nanoparticles nanoparticle content Reference Example 1 1.5 mL - - - Reference Example 2 1.5 mL 1.5 mL - - Reference Example 1 1.5 mL 1.5 mL Example 1 0.1 mg Reference Example 2 1.5 mL 1.5 mL Example 2 0.1 mg Reference Example 3 1.5 mL 1.5 mL Example 3 0.1 mg Reference Comparison Example 1 1.5 mL 1.5 mL Comparative Example 1 0.1 mg Reference Comparison Example 2 1.5 mL 1.5 mL Comparative Example 2 0.1 mg

[0136] 5. Nanoparticle Reducing Power Test

[0137] Absorbance data of 4-nitrophenol and 4-aminophenol (4-AP) contained in the mixed solutions prepared in Reference Example 1, Reference Example 2, Reference Examples 1 to 3, Reference Comparative Example 1, and Reference Comparative Example 2 were obtained in the UV-visible spectrum using a Thermo Scientific spectrophotometer (Evolution 220).

[0138] FIG. 5 is a graph of the UV-visible spectrum as each nanoparticle of Examples 1 to 3, Comparative Example 1, and Comparative Example 2 of the present invention is introduced into a 4-nitrophenol solution.

[0139] Specifically, FIG. 5(a) is a graph of the absorbance in the UV-visible spectra of Reference Example 1 (4-NP) and Reference Example 2 (4-NP + NaBH4). As shown in FIG. 5(a), it was confirmed that the absorbance peak shifted significantly from 316 nm to 400 nm upon the addition of NaBH4, and visually, the color of the mixed solution also changed from light yellow to dark yellow. That is, 4-NP is a 4-NPate anion (C6H4NO3 - It can be seen that it has been deprotonated.

[0140] Figure 5(b) is an absorbance graph in the absorbance spectrum after the mixed solution of Reference Example 2 was left for 60 minutes. As shown in Figure 5(b), it was confirmed that the absorbance peak at 400 nm of the mixed solution of Reference Example 2 remained constant for 60 minutes.

[0141] Figure 5(c) is a graph of absorbance in the UV-visible spectrum of Reference Example 1. As shown in Figure 5(c), as the nanoparticles prepared in Example 1 are introduced, the intensity of the 4-NPate peak at 400 nm disappears in about 9 minutes, and the reduction efficiency over 3 minutes is calculated to be 74.93%.

[0142] Figure 5(d) is a graph of absorbance in the UV-visible spectrum of Reference Example 2. As shown in Figure 5(d), as the nanoparticles prepared in Example 2 are introduced, the intensity of the 4-NPate peak at 400 nm disappears in about 3 minutes, and the reduction efficiency over 3 minutes is calculated to be 99.29%.

[0143] Figure 5(e) is a graph of the absorbance in the UV-visible spectrum of Reference Example 3. As shown in Figure 5(e), as the nanoparticles prepared in Example 3 were introduced, the intensity of the 4-NPate peak at 400 nm disappeared in 12 minutes, and the reduction efficiency over 3 minutes was calculated to be 63.24%.

[0144] Figure 5(f) is a graph of the absorbance in the UV-visible spectrum of Reference Comparative Example 1. As shown in Figure 5(f), as the nanoparticles prepared in Comparative Example 1 were introduced, the intensity of the 4-NPate peak at 400 nm disappeared in 15 minutes, and the reduction efficiency over 3 minutes was calculated to be 42.6%. In other words, it was confirmed that Reference Comparative Example 1 had a lower reduction efficiency than Reference Examples 1 to 3.

[0145] Figure 5(g) is a graph of the absorbance in the UV-visible spectrum of Reference Comparative Example 2. As shown in Figure 5(g), with the introduction of the nanoparticles of Comparative Example 2, the intensity of the 4-NPate peak at 400 nm did not disappear even after 30 minutes, and the reduction efficiency for 3 minutes was calculated to be 26.16%. In other words, it was confirmed that Reference Comparative Example 2 had a much lower reduction efficiency than Reference Examples 1 to 3.

[0146] Figure 5(h) is a graph of the reduction efficiency during a reaction time of 3 minutes for Figures 5(c) to (g). As shown in Figure 5(h), it was confirmed that Reference Examples 1 to 3 had higher reduction efficiency than Reference Comparative Example 1 and Reference Comparative Example 2.

[0148] The apparent velocity constants in each Reference Example 1 to Reference Example 3, Reference Comparative Example 1, and Reference Comparative Example 2 (with reference to FIG. 5 through the following equations (1) and (2)) k app ) calculated.

[0150] [Equation (1)]

[0151] R = -d [ C 4-NP ] / dt = k app × [ C 4-NP ]

[0152] Above [ C 4-NP ] refers to the concentration of 4-nitrophenol.

[0154] [Equation (2)]

[0155] ln( C t / C o ) = ln( A t / A o ) = -k app × t

[0156] The above C o is the initial concentration of 4-nitrophenol, C t is the final concentration of 4-nitrophenol, A o is the initial absorbance, A t represents the final absorbance.

[0158] Using the above equations (1) and (2), the apparent velocity constants in Reference Examples 1 to 3, Reference Comparative Example 1 and Reference Comparative Example 2 ( k app ) are 9.16 × 10⁻⁶ respectively -3 s -1 , 2.84 × 10 -2 s -1 , 7.81 × 10 -3 s -1 , 7.06 × 10 -3 s -1 , 6.64 × 10 -5 s -1 It was calculated as.

[0160] FIG. 6 shows the apparent velocity constants in Reference Examples 1 to 3, Reference Comparative Example 1 and Reference Comparative Example 2 of the present invention ( k app Figure 6 is a graph showing the apparent rate constants in Reference Example 1 (P-0.05-500), Reference Example 2 (P-0.25-500), Reference Example 3 (P-0.5-500), Reference Comparative Example 1 (Es-18-500), and Reference Comparative Example 2 (Comm.Co3O4) of the present invention.

[0161] As shown in Fig. 6, it was confirmed that 4-nitrophenol was rapidly reduced in Reference Examples 1 to 3 because they had higher apparent rate constants than in Reference Comparative Examples 1 and 2.

[0163] 5.1. NaBH4 Reducing power test according to changes in concentration

[0164] Figure 7 is a graph of the UV-visible spectrum and reduction efficiency according to the concentration of NaBH4 included in the mixed solution of Reference Example 2 of the present invention.

[0165] Specifically, FIG. 7(a) is a graph of absorbance in the UV-visible spectrum as the concentration of NaBH4 contained in the mixed solution of Reference Example 2 is adjusted to 0.0001 M. As shown in FIG. 7(a), as the concentration of NaBH4 is adjusted to 0.0001 M, the reduction efficiency for 3 minutes is calculated to be 48.22%, and the reduction efficiency for 20 minutes is calculated to be 61.41%.

[0166] Figure 7(b) is a graph of absorbance in the UV-visible spectrum as the concentration of NaBH4 contained in the mixed solution of Reference Example 2 is adjusted to 0.001 M. As shown in Figure 7(b), as the concentration of NaBH4 is adjusted to 0.001 M, the reduction efficiency for 3 minutes was calculated to be 59.32%, and the reduction efficiency for 20 minutes was calculated to be 82.54%.

[0167] Figure 7(c) is a graph of absorbance in the UV-visible spectrum as the concentration of NaBH4 contained in the mixed solution of Reference Example 2 is adjusted to 0.01 M. As shown in Figure 7(c), as the concentration of NaBH4 is adjusted to 0.01 M, the reduction efficiency for 3 minutes was calculated to be 72.23%, and the reduction efficiency for 15 minutes was calculated to be 91.47%.

[0168] Figure 7(d) is a graph of absorbance in the UV-visible spectrum as the concentration of NaBH4 contained in the mixed solution of Reference Example 2 is adjusted to 0.1 M. As shown in Figure 7(d), the reduction efficiency for 3 minutes was calculated to be 99.29% as the concentration of NaBH4 was adjusted to 0.1 M.

[0169] Figure 7(e) is a graph of reduction efficiency according to reaction time of Figures 7(a) to (d). As shown in Figure 7(e), it was found that the reduction efficiency was superior at 99.29% when the concentration of NaBH4 was adjusted to 0.1 M.

[0171] 5.2. Reducing power test according to nanoparticle content

[0172] FIG. 8 shows the UV-visible spectrum and apparent rate constant according to the nanoparticle content of Example 2 of the present invention ( k app ) is a graph. Specifically, FIG. 8(a) is a graph of absorbance measured in the UV-visible spectrum by preparing a mixed solution in the same way as Reference Example 2, except that the content of the nanoparticles prepared in Example 2 was adjusted to 0.06 mg / mL, FIG. 8(b) is a graph of the nanoparticles prepared in Example 2 with the content adjusted to 0.15 mg / mL, FIG. 8(c) is a graph of the nanoparticles prepared in Example 2 with the content adjusted to 0.1 mg / mL, and FIG. 8(d) is a graph of the nanoparticles prepared in Example 2 with the content adjusted to 0.2 mg / mL.

[0173] As shown in Fig. 8(a), when the content of the nanoparticles in Example 2 was adjusted to 0.06 mg / mL, the reduction efficiency for 3 minutes was calculated to be 66.31%, and the reduction efficiency for 15 minutes was calculated to be 93.17%. As shown in Fig. 8(b), when the content of the nanoparticles in Example 2 was adjusted to 0.1 mg / mL, the reduction efficiency for 3 minutes was calculated to be 99.29%. As shown in Fig. 8(c), when the content of the nanoparticles in Example 2 was adjusted to 0.15 mg / mL, the reduction efficiency for 2.5 minutes was calculated to be 99.56%. As shown in Fig. 8(d), when the content of the nanoparticles in Example 2 was adjusted to 0.2 mg / mL, the reduction efficiency for 1.5 minutes was calculated to be 99.75%.

[0174] FIG. 8(e) is a graph showing the apparent rate constants in FIG. 8(a) to (d). The apparent rate constants were calculated using Equation (1) and Equation (2). With reference to FIG. 8(e), the apparent rate constants according to the introduction content of the nanoparticles prepared in Example 2 are shown in Table 5.

[0176] Nanoparticle content of Example 2 Apparent velocity constant ( k app ) 0.06 mg / mL 2.12 × 10 -3 s -1 0.1 mg / mL 2.84 × 10 -2 s -1 0.15 mg / mL 2.92 × 10 -2 s -1 0.2 mg / mL 3.38 × 10 -2 s -1

[0178] Referring to Table 5 above, it was confirmed that 4-nitrophenol is rapidly reduced as the content of the introduced nanoparticles increases, as it has a higher apparent rate constant.

[0179] In addition, it was confirmed that increasing the content of the nanoparticles of Example 2 from 0.06 mg / mL to 0.1 mg / mL increased the reduction efficiency by 6.1 ± 2%, and increasing it from 0.1 mg / mL to 0.2 mg / mL increased the reduction efficiency by 4.6%. Through this, the apparent rate constant for the content of the nanoparticles of Example 2 introduced ( k app / m cat The normalized ratio of ) (k n ) is shown in Table 6.

[0181] Nanoparticle content of Example 2 ratio( k n ) 0.06 mg / mL 3.53 × 10 -2 s -1 ·mg -1 0.1 mg / mL 2.84 × 10 -1 s -1 ·mg -1 0.15 mg / mL 1.95 × 10 -1 s -1 ·mg -1 0.2 mg / mL 1.69 × 10 -1 s -1 ·mg -1

[0183] Referring to Table 6 above, when the nanoparticles of Example 2 are introduced at 0.1 mg / mL, the apparent rate constant for the content of the nanoparticles ( k app / m cat The normalized ratio of ) (k n It was possible to confirm that ) was the highest.

[0185] 6. Nanoparticle Recycling Test

[0186] A nanoparticle solution was prepared by dissolving 1 mg of the nanoparticles prepared in Example 2 in 10 mL of deionized water (DI).

[0187] Subsequently, 1.5 mL of 0.1 M NaBH4 solution and 1.5 mL of 0.1 mM 4-nitrophenol solution were added to the above nanoparticle solution, and this was done continuously for a total of 6 times, with 1 cycle comprising the addition of each solution.

[0188] Absorbance data in the UV-visible spectrum was obtained for each cycle using a Thermo Scientific spectrophotometer (Evolution 220).

[0189] Figure 9 is a graph of the UV-visible spectrum according to the cycle in which the nanoparticles of Example 2 of the present invention are introduced into a 4-nitrophenol solution.

[0190] FIG. 10 is a graph of reduction efficiency and apparent rate constant according to the cycle in which the nanoparticles of Example 2 of the present invention are introduced into a 4-nitrophenol solution ( k app It is a graph.

[0191] Referring to FIGS. 9 and 10, the reduction efficiency after the first cycle is 99.29% and the apparent rate constant ( k app ) is 2.82 × 10⁻⁶ -2 s -1 and even after the 6th cycle, the reduction efficiency is 88.84% and the apparent rate constant ( k app ) is 8.4 × 10 -3 s -1 It was possible to confirm that it appeared as.

[0192] Figure 11 is an FE-SEM image and XRD graph after the 6th cycle following the introduction of the nanoparticles of Example 2 of the present invention into a 4-nitrophenol solution.

[0193] The above FE-SEM image is an image of nanoparticles obtained using a field emission scanning electron microscope (FE-SEM, S-2400, Hitachi), and the above XRD graph is the crystal structure of nanoparticles analyzed using a D8 ADVANCE X-ray diffraction (XRD) equipped with a diffractometer using a Cu Kα radiation (1.54 Å) source operating at 40 kV and 40 mA with a 2θ range of (10 - 90)°.

[0194] As shown in Figures 11 (a) and (b), it was confirmed that the nanoparticles of Example 2 had a layered structure and a porous structure even after the 6th cycle was performed. In other words, it was confirmed that the physical structure of the nanoparticles was maintained even after introducing and using the nanoparticles of Example 2 multiple times.

[0195] As shown in FIG. 11(c), the peak intensity ratio of (311) / (411) immediately after the nanoparticles of Example 2 were introduced into the 4-nitrophenol solution (Pristine P-0.25-500) was 1.12, whereas after the 6th cycle was performed (6 th It was confirmed that the peak intensity ratio of (311) / (411) of round recycled P-0.25-500) increased to 1.24.

[0197] 7. Comparative test of the reducing power of nanoparticles

[0198] Apparent rate constants were compared by reducing 4-nitrophenol in the same manner as in Reference Example 1, except that the process conditions were adjusted as follows in Reference Example 1. In addition, Table 7 below shows the apparent rate constants for the reduction of 4-nitrophenol using currently commercialized materials.

[0200] 4-NP and substances introduced into NaBH4 solution Content of the introduced substance (mg) [4-NP] (mM) [NaBH4] (M) Reduction time (minutes) k app (s -1 ) Example 1 0.1 0.1 0.1 3 9.16 × 10 -3 Example 2 0.1 0.1 0.1 3 2.84 × 10 -2 Example 3 0.1 0.1 0.1 3 7.81 × 10 -3 s -1 , Comparative Example 1 0.1 0.1 0.1 3 7.06 × 10 -3 Comparative Example 2 0.1 0.1 0.1 3 6.64 × 10 -5 CuO@C 50 0.25 0.43 18 6.0 × 10 -3 Co2P nanowires 0.2 1 1 - 1.5 × 10 -3 Co3O4 / HNTs 1 0.12 0.048 11 4.0 × 10 -3 Co-CC 0.27 0.168 0.25 2.17 7.0 × 10 -3 Meso-Co3O4 2 0.35 0.1 70 - Fe3O4@COF-Au 3 1.8 0.99 20 3.0 × 10 -3

[0202] As shown in Table 7 above, when 4-nitrophenol is reduced by introducing the nanoparticles of Examples 1 to 3, k app It was possible to confirm that it was excellent.

[0204] 8. Comparative test of the reducing power of nanoparticles against nitro group-containing aromatic compounds

[0205] Figure 12 is a UV-visible spectrum graph according to the type of nitro group-containing aromatic compound into which the nanoparticles of Example 2 of the present invention are introduced. Specifically, FIG. 12(a) is a graph showing the absorbance in the UV-visible spectrum measured by preparing a mixed solution in the same manner as Reference Example 2, except that 1.5 mL of 0.1 mM 2-nitrophenol (2-NP) was used as the nitro group-containing aromatic compound; FIG. 12(b) uses 1.5 mL of 0.1 mM 3-nitrobenzaldehyde (3-NBA) as the nitro group-containing aromatic compound; FIG. 12(c) uses 1.5 mL of 0.1 mM 4-nitroaniline (4-NA) as the nitro group-containing aromatic compound; and FIG. 12(d) uses 0.1 mM 2-nitrophenol (2-NP), 0.1 mM 3-nitrobenzaldehyde (3-NBA), 0.1 mM 4-nitroaniline (4-NA), and 0.1 mM as the nitro group-containing aromatic compounds. Absorbance data was obtained using 1.5 mL of a solution mixed with 4-nitrophenol (4-NP).

[0206] As shown in Fig. 12(a), the reduction efficiency for 4 minutes was calculated to be 97.12% when using 2-nitrophenol (2-NP) as the nitro group-containing aromatic compound. As shown in Fig. 12(b), the reduction efficiency for 6 minutes was calculated to be 95.55% when using 3-nitrobenzaldehyde (3-NBA) as the nitro group-containing aromatic compound. As shown in Fig. 12(c), the reduction efficiency for 2 minutes was calculated to be 99.47% when using 4-nitroaniline (4-NA) as the nitro group-containing aromatic compound. As shown in Fig. 12(d), the reduction efficiency for 4 minutes was calculated to be 99.23% even when using 2-nitrophenol (2-NP), 3-nitrobenzaldehyde (3-NBA), 4-nitroaniline (4-NA), and 4-nitrophenol (4-NP) as nitro group-containing aromatic compounds. In other words, it was confirmed that the nanoparticles of the present invention can efficiently reduce nitro group-containing aromatic compounds to amino group-containing aromatic compounds.

[0208] 9. Testing the reducing power of nanoparticles manufactured by including an additional heat treatment step

[0209] Example 4

[0210] The nanoparticles obtained in Example 2 above were further annealed in an atmospheric environment at a temperature of 500 ℃ for 3 hours at a heating rate of 5 ℃ / min to obtain nanoparticles.

[0212] Comparative Example 6

[0213] In addition, the nanoparticles obtained in Comparative Example 1 were further annealed in an atmospheric environment at a temperature of 500 ℃ at a heating rate of 5 ℃ / min for 3 hours to obtain nanoparticles.

[0215] Four mixed solutions were prepared by adding 0.1 mg each of the nanoparticles of Example 2, Comparative Example 1, Example 4, and Comparative Example 6 to 1.5 mL of a solution mixed with 1.5 mL of 0.1 M NaBH4 and 0.1 mM 4-nitrophenol (4-NP), respectively, into cuvettes.

[0216] Figure 13 is a UV-visible spectrum of each nanoparticle of Example 4 and Comparative Example 6 of the present invention introduced into a 4-nitrophenol solution.

[0217] Specifically, FIG. 13(a) is a UV-visible spectrum graph following the introduction of the nanoparticles (Es-18-500-500) of Comparative Example 6 into a 4-nitrophenol mixed solution. As shown in FIG. 13(a), the reduction efficiency for 7 minutes following the introduction of the nanoparticles of Comparative Example 6 was calculated to be 77.64%.

[0218] Figure 13(b) is a UV-visible spectrum graph following the introduction of the nanoparticles (Es-18-500-500) of Example 4 into a 4-nitrophenol mixed solution. As shown in Figure 13(b), the reduction efficiency for 3 minutes following the introduction of the nanoparticles of Example 4 was calculated to be 99.55%.

[0219] Figure 14 is a graph of the hydrogen generation rates after each nanoparticle of Example 2, Example 4, Comparative Example 1, and Comparative Example 6 of the present invention was introduced into a 4-nitrophenol solution. As shown in Figure 14, the hydrogen generation rate of the nanoparticles of Comparative Example 1 was calculated to be 3.394 L / gm.min, the hydrogen generation rate of the nanoparticles of Comparative Example 6 was 1.62 L / gm.min, the hydrogen generation rate of the nanoparticles of Example 2 was 1.17 L / gm.min, and the hydrogen generation rate of the nanoparticles of Example 4 was 1.06 L / gm.min.

[0220] Figure 15 is a graph showing the hydrogen generation rate and 4-nitrophenol reduction efficiency after each nanoparticle of Example 2, Example 4, Comparative Example 1, and Comparative Example 6 of the present invention was introduced into a 4-nitrophenol solution. As shown in Figure 15, the 4-nitrophenol reduction efficiency of the nanoparticles of Comparative Example 1 was 42.6%, whereas the 4-nitrophenol reduction efficiency of the nanoparticles of Comparative Example 6, which were additionally heat-treated with the nanoparticles of Comparative Example 1, was calculated to be 77.64%. In addition, the 4-nitrophenol reduction efficiency of the nanoparticles of Example 2 was 99.29%, whereas the 4-nitrophenol reduction efficiency of the nanoparticles of Example 4, which were additionally heat-treated with the nanoparticles of Example 2, was calculated to be 99.55%.

[0221] Referring to Figures 13 to 15, it can be seen that as the nanoparticles undergo additional heat treatment, hydrogen generation is reduced and hydrogen protons are retained, resulting in higher efficiency in the reduction reaction.

Claims

Claim 1 A method for manufacturing nanoparticles comprising: a step of preparing a mixture containing a cobalt precursor and polyacrylonitrile; and a step of heat-treating the mixture under a temperature condition of 500°C or higher and 800°C or lower to produce nanoparticles containing cobalt oxide nanosheets; wherein the nanoparticles are catalysts that convert a nitro group-containing aromatic compound into an amine group-containing aromatic compound. Claim 2 A method for manufacturing nanoparticles according to claim 1, wherein the cobalt precursor comprises cobalt hydrate. Claim 3 A method for manufacturing nanoparticles according to claim 1, wherein the weight-average molecular weight of the polyacrylonitrile is 50,000 g / mol or more and 300,000 g / mol or less. Claim 4 A method for manufacturing nanoparticles according to claim 1, wherein the mixture contains 1 part by weight or more and 200 parts by weight or less of the cobalt precursor per 100 parts by weight of the polyacrylonitrile. Claim 5 A method for manufacturing nanoparticles according to claim 1, wherein the heat treatment step is performed at a heating rate of 1 ℃ / min or more and 20 ℃ / min or less. Claim 6 A method for manufacturing nanoparticles according to claim 1, wherein the heat treatment step is performed for a time of 10 minutes or more and 10 hours or less. Claim 7 Co, manufactured by the manufacturing method according to claim 1 and calculated through XPS spectrum results 3+ / Co 2+ A nanoparticle having an atomic concentration ratio of 0.3 or more and 0.5 or less, wherein the nanoparticle is a catalyst that converts a nitro group-containing aromatic compound into an amine group-containing aromatic compound. Claim 8 delete Claim 9 In claim 7, the nanoparticles are nanoparticles having an average size of 10 nm or more and 150 nm or less. Claim 10 In claim 7, the nanoparticles have an average pore volume of 0.05 cm² 3 / g or more than 1.0 cm 3 nanoparticles in g. Claim 11 delete

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