Sumalin Phokha

Publications (3)4.29 Total impact

• Article: Synthesis, characterization, and magnetic properties of monodisperse CeO2 nanospheres prepared by PVP-assisted hydrothermal method.

  Sumalin Phokha, Supree Pinitsoontorn, Prae Chirawatkul, Yingyot Poo-Arporn, Santi Maensiri
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  ABSTRACT: Ferromagnetism was observed at room temperature in monodisperse CeO2 nanospheres synthesized by hydrothermal treatment of Ce(NO3)3·6H2O using polyvinylpyrrolidone as a surfactant. The structure and morphology of the products were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy (FE-SEM). The optical properties of the nanospheres were determined using UV and visible spectroscopy and photoluminescence (PL). The valence states of Ce ions were also determined using X-ray absorption near edge spectroscopy. The XRD results indicated that the synthesized samples had a cubic structure with a crystallite size in the range of approximately 9 to 19 nm. FE-SEM micrographs showed that the samples had a spherical morphology with a particle size in the range of approximately 100 to 250 nm. The samples also showed a strong UV absorption and room temperature PL. The emission might be due to charge transfer transitions from the 4f band to the valence band of the oxide. The magnetic properties of the samples were studied using a vibrating sample magnetometer. The samples exhibited room temperature ferromagnetism with a small magnetization of approximately 0.0026 to 0.016 emu/g at 10 kOe. Our results indicate that oxygen vacancies could be involved in the ferromagnetic exchange, and the possible mechanism of formation was discussed based on the experimental results.
  Nanoscale Research Letters 07/2012; 7(1):425. · 2.73 Impact Factor
• Article: Room temperature ferromagnetism in Fe-doped CeO2 nanoparticles.

  Santi Maensiri, Sumalin Phokha, Paveena Laokul, Supapan Seraphin
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  ABSTRACT: RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.
  Journal of Nanoscience and Nanotechnology 11/2009; 9(11):6415-20. · 1.56 Impact Factor
• Article: A simple synthesis and magnetic behavior of nanocrystalline Zn0.9Co0.1O powders by using Zn and Co acetates and polyvinyl pyrrolidone as precursors

  Santi Maensiri, Paveena Laokul, Sumalin Phokha
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  ABSTRACT: This paper reports the synthesis of nanocrystalline powders of Co-doped ZnO (i.e. Zn0.9Co0.1O (ZCO)) diluted magnetic semiconductor by a simple method using acetate salts of Zn and Co, and polyvinyl pyrrolidone as precursors. The morphology and crystalline size of the synthesized powders were evaluated by scanning electron microscopy and transmission electron microscopy (TEM). The ZCO powders consist of both nanoparticles with particle sizes of ∼50–100 nm and nanorods with diameters of ∼100–200 and ∼200–500 nm in length. The X-ray diffraction and TEM results indicated that the synthesized ZCO powders had the pure wurtzite structure without any significant change in the structure affected by Co substitution. Optical absorption measurements showed absorption bands indicating the presence of Co ions in substitution of Zn ions. Room-temperature magnetization results revealed a paramagnetic behavior for the ZCO precursor (as grown sample) and a ferromagnetic behavior for the ZCO powders calcined in air at 873 K for 1 h.
  Journal of Magnetism and Magnetic Materials.