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Fabrication and Characterization of Monodisperse Magnetic Porous Nickel Microspheres as Novel Catalysts.

Teng C, He J, Zhu L, Ren L, Chen J, Hong M, Wang Y - Nanoscale Res Lett (2015)

Bottom Line: The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction.The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol.The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

View Article: PubMed Central - PubMed

Affiliation: Guangdong Provincial Key Laboratory of Nano-Micro Materials Research, School of Chemical Biology & Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.

ABSTRACT
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

No MeSH data available.


SEM images of (a–c) polymer microspheres, (d–f) NiO microspheres, and (g–i) Ni microspheres under different magnification
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Fig1: SEM images of (a–c) polymer microspheres, (d–f) NiO microspheres, and (g–i) Ni microspheres under different magnification

Mentions: SEM images displayed in Fig. 1 demonstrate that the structured three-dimensional network of the parent polymer microspheres was well preserved in the synthesized porous NiO microspheres and porous Ni microspheres. Therefore, Ni precursors entered into the pores and interacted closely with the polymer skeleton. After reduction, the obtained porous Ni microspheres kept excellent monodispersity and well-defined spherical morphology. Due to the crystallite transformation at high temperature during reduction, the nanoparticles in Ni microspheres are larger than that of the NiO microspheres. As seen from the particle size of the polymer template and the synthesized microspheres in Table 1, the composite microspheres show similar size and monodispersity to the original polymer microspheres indicating that Ni precursor penetration did not cause structure deformation. Compared with the template microspheres (Fig. 1a–c), the porous NiO microspheres (Fig. 1d–f) were smaller probably due to shrinkage of the skeleton, high density of NiO, and growth of NiO crystallite size during calcination. High-temperature reduction further reduced the size of the formed Ni metal microspheres (Fig. 1g–i). All these as-prepared microspheres are in excellent independent spherical morphology. Agglomeration for the Ni microspheres, typically observed for molecular self-assembled ones (Zhu et al., solid state sciences 2011;12:438–43), was not observed in our study. This demonstrated the strong templating power of our hard polymer microspheres, which counteract the surface chain-forming force caused by the magneto-static energy of ferromagnetic particles. The size distribution analyzed by the size analyzer confirmed the SEM observations (Table 1). The size of the original polymer microspheres and the polymer composite was very close, of 4.44 and 4.49 μm, respectively. Burning out the polymer template decreased the NiO microspheres to an average size of 1.83 μm, and further reductive process reduced the Ni microspheres to 0.91 μm. All microspheres were exceptionally uniform, and the coefficient of variation for particle size of NiO and Ni metal microspheres was 4.9 and 7.7 %, respectively.Fig. 1


Fabrication and Characterization of Monodisperse Magnetic Porous Nickel Microspheres as Novel Catalysts.

Teng C, He J, Zhu L, Ren L, Chen J, Hong M, Wang Y - Nanoscale Res Lett (2015)

SEM images of (a–c) polymer microspheres, (d–f) NiO microspheres, and (g–i) Ni microspheres under different magnification
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593984&req=5

Fig1: SEM images of (a–c) polymer microspheres, (d–f) NiO microspheres, and (g–i) Ni microspheres under different magnification
Mentions: SEM images displayed in Fig. 1 demonstrate that the structured three-dimensional network of the parent polymer microspheres was well preserved in the synthesized porous NiO microspheres and porous Ni microspheres. Therefore, Ni precursors entered into the pores and interacted closely with the polymer skeleton. After reduction, the obtained porous Ni microspheres kept excellent monodispersity and well-defined spherical morphology. Due to the crystallite transformation at high temperature during reduction, the nanoparticles in Ni microspheres are larger than that of the NiO microspheres. As seen from the particle size of the polymer template and the synthesized microspheres in Table 1, the composite microspheres show similar size and monodispersity to the original polymer microspheres indicating that Ni precursor penetration did not cause structure deformation. Compared with the template microspheres (Fig. 1a–c), the porous NiO microspheres (Fig. 1d–f) were smaller probably due to shrinkage of the skeleton, high density of NiO, and growth of NiO crystallite size during calcination. High-temperature reduction further reduced the size of the formed Ni metal microspheres (Fig. 1g–i). All these as-prepared microspheres are in excellent independent spherical morphology. Agglomeration for the Ni microspheres, typically observed for molecular self-assembled ones (Zhu et al., solid state sciences 2011;12:438–43), was not observed in our study. This demonstrated the strong templating power of our hard polymer microspheres, which counteract the surface chain-forming force caused by the magneto-static energy of ferromagnetic particles. The size distribution analyzed by the size analyzer confirmed the SEM observations (Table 1). The size of the original polymer microspheres and the polymer composite was very close, of 4.44 and 4.49 μm, respectively. Burning out the polymer template decreased the NiO microspheres to an average size of 1.83 μm, and further reductive process reduced the Ni microspheres to 0.91 μm. All microspheres were exceptionally uniform, and the coefficient of variation for particle size of NiO and Ni metal microspheres was 4.9 and 7.7 %, respectively.Fig. 1

Bottom Line: The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction.The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol.The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

View Article: PubMed Central - PubMed

Affiliation: Guangdong Provincial Key Laboratory of Nano-Micro Materials Research, School of Chemical Biology & Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.

ABSTRACT
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

No MeSH data available.