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RISS 인기검색어
- 검색키워드
- 저자 : Knyazev Yuriy V. (검색결과 2 건)
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Tuning of the Interparticle interactions in ultrafine ferrihydrite nanoparticles
Knyazev, Yuriy V.,Balaev, Dmitry A.,Yaroslavtsev, Roman N.,Krasikov, Aleksandr A.,Velikanov, Dmitry A.,Mikhlin, Yuriy L.,Volochaev, Mikhail N.,Bayukov, Oleg A.,Stolyar, Sergei V.,Iskhakov, Rauf S. Techno-Press 2022 Advances in nano research Vol.12 No.6
We prepared two samples of ultrafine ferrihydrite (FH) nanoparticle ensembles of quite a different origin. First is the biosynthesized sample (as a product of the vital activity of bacteria Klebsiella oxytoca (hereinafter marked as FH-bact) with a natural organic coating and negligible magnetic interparticle interactions. And the second one is the chemically synthesized ferrihydrite (hereinafter FH-chem) without any coating and high level of the interparticle interactions. The interparticle magnetic interactions have been tuned by modifying the nanoparticle surface in both samples. The coating of the FH-bact sample has been partially removed by annealing at 150℃ for 24 h (hereinafter FH-annealed). The FH-chem sample, vice versa, has been coated (1.0 g) with biocompatible polysaccharide (arabinogalactan) in an ultrasonic bath for 10 min (hereinafter FH-coated). The changes in the surface properties of nanoparticles have been controlled by XPS. According to the electron microscopy data, the modification of the nanoparticle surface does not drastically change the particle shape and size. A change in the average nanoparticle size in sample FH-annealed to 3.3 nm relative to the value in the other samples (2.6 nm) has only been observed. The estimated particle coating thickness is about 0.2-0.3 nm for samples FH-bact and FH-coated and 0.1 nm for sample FH-annealed. Mössbauer and magnetization measurements are definitely shown that the drastic change in the blocking temperature is caused by the interparticle interactions. The experimental temperature dependences of the hyperfine field <H<sub>hf</sub>>(T) for samples FH-bact and FH-coated have not revealed the effect of interparticle interactions. Otherwise, the interparticle interaction energy E<sub>int</sub> estimated from the <H<sub>hf</sub>>(T) for samples FH-chem and FH-annealed has been found to be 121k<sub>B</sub> and 259k<sub>B</sub>, respectively.
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Ivantsov Ruslan D.,Lin Chun-Rong,Ivanova Oxana S.,Altunin Roman R.,Knyazev Yuriy V.,Molokeev Maxim S.,Zharkov Sergey M.,Chen Ying-Zhen,Lin En-Szu,Chen Bing-Yi,Shestakov Nikolai P.,Edelman Irina S. 한국물리학회 2021 Current Applied Physics Vol.25 No.-
Greigite (Fe3S4) nanoparticles (NPs) were fabricated by the thermal decomposition method using two different surfactants: oleylamine (OLA) and 1-hexadecylamine (HDA). In both cases, the synthesized NPs were characterized as the Fe3S4 nanocrystals with minor inclusions of Fe9S11 phase. FT-IR spectroscopy and thermogravimetric analysis allow concluding about OLA or HDA shells covering magnetic core of NPs. M¨ossbauer spectra has revealed deviations of iron ions distribution among crystal positions from that presented in literature for pure greigite. In accordance with these deviations, the pronounce changes are observed in the magnetic circular dichroism (MCD) spectra which manifest themselves as the spectrum shift to higher energies of electromagnetic waves and redistribution of the MCD maximum intensities. These effects are associated with a change in the density of electronic states in the samples due to the redistribution of iron ions between octahedral and tetrahedral positions in nanocrystals under the influence of surfactants.
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