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Self-arrangement of nanoparticles toward crystalline metal oxides with high surface areas and tunable 3D mesopores.

Lee HI, Lee YY, Kang DU, Lee K, Kwon YU, Kim JM - Sci Rep (2016)

Bottom Line: We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity.At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework.Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Sungkyunkwan University, Suwon, 440-746, Republic of Korea.

ABSTRACT
We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity. At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework. Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes. A simple control of the Si/Ti ratio verified the versatility of the present method through the successful control of mean pore diameter in the range of 2-35 nm and specific surface area in the ranges of 180-250 m(2) g(-1). The present synthesis method is successfully extended to other metal oxides, their mixed oxides and analogues with different particle sizes, regarding as a general method for mesoporous metal (or mixed metal) oxides.

No MeSH data available.


Related in: MedlinePlus

Variations of the properties of MT-100 with heat-treatments at various temperatures (A) Surface area (0), pore diameter (▄) and crystallite size (▲), and (B) total pore volume (0), and micropore volume (< 2 nm) (▄). The curves for the total surface area and the micropore volume are almost identical except for the scales, indicating that the increase of the crystallite size is due to the coalescence of titania particles around micropores, which does not affect the mesopores. In fact, the coalescence of the titania nanoparticles thins the walls and widens the pores, which is reflected in the slightly increased pore diameter and mesopore volume with the temperature up to 700 °C.
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f5: Variations of the properties of MT-100 with heat-treatments at various temperatures (A) Surface area (0), pore diameter (▄) and crystallite size (▲), and (B) total pore volume (0), and micropore volume (< 2 nm) (▄). The curves for the total surface area and the micropore volume are almost identical except for the scales, indicating that the increase of the crystallite size is due to the coalescence of titania particles around micropores, which does not affect the mesopores. In fact, the coalescence of the titania nanoparticles thins the walls and widens the pores, which is reflected in the slightly increased pore diameter and mesopore volume with the temperature up to 700 °C.

Mentions: Because the walls are composed of highly crystalline anatase, the MT-x materials are expected to have enhanced thermal stability. XRD patterns of MT-100 material depending on the thermal-treatment temperatures are shown in Figure S2. All the peaks in the XRD pattern can be indexed to the anatase phase, which is stable up to 700 °C. At higher temperature, rutile and brookite phases are observed and the anatase phase disappears completely at 900 °C. Crystallite sizes, calculated by using the Scherrer equation, gradually increase with increasing the heating temperatures and are shown in Fig. 5. The changes in surface areas, pore diameters, total pore volumes and micropore volumes of the MT-100 material depending on the heating temperatures are also plotted in Fig. 5. We found that the MT-100 material exhibited excellent thermal stability up to 700 °C, although the crystallite size increases and, hence, the surface area is reduced (Fig. 5).


Self-arrangement of nanoparticles toward crystalline metal oxides with high surface areas and tunable 3D mesopores.

Lee HI, Lee YY, Kang DU, Lee K, Kwon YU, Kim JM - Sci Rep (2016)

Variations of the properties of MT-100 with heat-treatments at various temperatures (A) Surface area (0), pore diameter (▄) and crystallite size (▲), and (B) total pore volume (0), and micropore volume (< 2 nm) (▄). The curves for the total surface area and the micropore volume are almost identical except for the scales, indicating that the increase of the crystallite size is due to the coalescence of titania particles around micropores, which does not affect the mesopores. In fact, the coalescence of the titania nanoparticles thins the walls and widens the pores, which is reflected in the slightly increased pore diameter and mesopore volume with the temperature up to 700 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759599&req=5

f5: Variations of the properties of MT-100 with heat-treatments at various temperatures (A) Surface area (0), pore diameter (▄) and crystallite size (▲), and (B) total pore volume (0), and micropore volume (< 2 nm) (▄). The curves for the total surface area and the micropore volume are almost identical except for the scales, indicating that the increase of the crystallite size is due to the coalescence of titania particles around micropores, which does not affect the mesopores. In fact, the coalescence of the titania nanoparticles thins the walls and widens the pores, which is reflected in the slightly increased pore diameter and mesopore volume with the temperature up to 700 °C.
Mentions: Because the walls are composed of highly crystalline anatase, the MT-x materials are expected to have enhanced thermal stability. XRD patterns of MT-100 material depending on the thermal-treatment temperatures are shown in Figure S2. All the peaks in the XRD pattern can be indexed to the anatase phase, which is stable up to 700 °C. At higher temperature, rutile and brookite phases are observed and the anatase phase disappears completely at 900 °C. Crystallite sizes, calculated by using the Scherrer equation, gradually increase with increasing the heating temperatures and are shown in Fig. 5. The changes in surface areas, pore diameters, total pore volumes and micropore volumes of the MT-100 material depending on the heating temperatures are also plotted in Fig. 5. We found that the MT-100 material exhibited excellent thermal stability up to 700 °C, although the crystallite size increases and, hence, the surface area is reduced (Fig. 5).

Bottom Line: We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity.At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework.Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Sungkyunkwan University, Suwon, 440-746, Republic of Korea.

ABSTRACT
We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity. At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework. Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes. A simple control of the Si/Ti ratio verified the versatility of the present method through the successful control of mean pore diameter in the range of 2-35 nm and specific surface area in the ranges of 180-250 m(2) g(-1). The present synthesis method is successfully extended to other metal oxides, their mixed oxides and analogues with different particle sizes, regarding as a general method for mesoporous metal (or mixed metal) oxides.

No MeSH data available.


Related in: MedlinePlus