Effect of Synthesis Method of La1 − xSr x MnO3 Manganite Nanoparticles on Their Properties

Nanoscale Research Letters, Jan 2018

Nanoparticles of lanthanum-strontium manganite were synthesized via different methods, namely, sol-gel method, precipitation from non-aqueous solution, and precipitation from reversal microemulsions. It was shown that the use of organic compounds and non-aqueous media allowed significantly decreasing of the crystallization temperature of nanoparticles, and the single-phased crystalline product was formed in one stage. Morphology and properties of nanoparticles depended on the method and conditions of the synthesis. The heating efficiency directly depended on the change in the magnetic parameters of nanoparticles, especially on the magnetization. Performed studies showed that each of these methods of synthesis can be used to obtain weakly agglomerated manganite nanoparticles; however, particles synthesized via sol-gel method are more promising for use as hyperthermia inducers. PACS: 61.46.Df 75.75.Cd 81.20. Fw

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Effect of Synthesis Method of La1 − xSr x MnO3 Manganite Nanoparticles on Their Properties

Shlapa et al. Nanoscale Research Letters Effect of Synthesis Method of La1 − xSrxMnO3 Manganite Nanoparticles on Their Properties Yulia Shlapa 0 Sergii Solopan 0 Anatolii Belous 0 Alexandr Tovstolytkin 0 V. I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine , 142, Palladina ave., 32/34, Kiev 03680 , Ukraine Nanoparticles of lanthanum-strontium manganite were synthesized via different methods, namely, sol-gel method, precipitation from non-aqueous solution, and precipitation from reversal microemulsions. It was shown that the use of organic compounds and non-aqueous media allowed significantly decreasing of the crystallization temperature of nanoparticles, and the single-phased crystalline product was formed in one stage. Morphology and properties of nanoparticles depended on the method and conditions of the synthesis. The heating efficiency directly depended on the change in the magnetic parameters of nanoparticles, especially on the magnetization. Performed studies showed that each of these methods of synthesis can be used to obtain weakly agglomerated manganite nanoparticles; however, particles synthesized via sol-gel method are more promising for use as hyperthermia inducers. PACS: 61.46.Df 75.75.Cd 81.20. Fw Manganite nanoparticles; Sol-gel; Non-aqueous solution; Microemulsion; Magnetization; Specific loss power Background Structure and properties of magnetic materials differ from those of bulk materials in the transition to the nanoscale [ 1 ]. In addition to possible practical application in various magnetic sensors, magnetic recording systems [ 2 ], magnetic nanoparticles are of particular interest in the possibilities of practical use in medicine. Researchers study many possible medical directions of their application: delivery of drugs and biological objects [ 3, 4 ], biomarkers [5], magnetic resonance imaging (MRI) [ 6, 7 ], etc. One of the promising directions for medical application of magnetic nanoparticles is hyperthermia—locally heating the oncological tumors under the action of an alternating magnetic field to 43–45 °C, at which the tumor cells die [ 8 ]. Application of an external alternating magnetic field is accompanied by a number of problems: uneven and uncontrolled heating tumor, risk of overheating and destruction of healthy tissues, and impossibility of heating the deep-seated tumors. Therefore, in 1993, Prof. Jordan suggested the idea of magnetic hyperthermia, which consisted in the use of the magnetic nanoparticles and an alternating magnetic field [ 9 ]. In this case, the magnetic nanoparticles must be previously injected into the tumor, and such tumor must be affected by an alternating magnetic field. Particle temperature will increase by the absorption of magnetic energy and provide the local heating. However, such nanoparticles must satisfy a number of requirements: small sizes and weak agglomeration of nanoparticles; such particles must be single domain and superparamagnetic (to prevent interactions between individual nanoparticles in the absence of magnetic field), and they must effectively heat up in the alternating magnetic field to the required temperatures (43–45 °C) and demonstrate high specific loss power (SLP) values. At present, magnetic nanoparticles of the magnetite Fe3O4 with a spinel structure are actively investigated as possible mediators of hyperthermia treatment [ 7, 10, 11 ]. Magnetite is characterized by a high value of Curie temperature (TC ≈ 580 °C) [ 12 ]—the transition temperature from magnetic to paramagnetic state. Since magnetic nanoparticles heat up in an alternating magnetic field only when they are in a magnetic state (up to TC point), in the case of magnetite, the heating is uncontrollable up to high temperatures. It may result in overheating and destroying the healthy tissues. To prevent this problem, it is important to search for the alternative materials, in which the Curie point will be in the temperature range that is necessary for hyperthermia. In this case, heterosubstituted manganites of lanthanum-strontium La1 − xSrxMnO3 (LSMO) with the distorted perovskite structure are of particular interest. They have the phase transition temperature near 45 °C that provides the controlled heating temperature without any additional thermoregulative devices. Crystallization energy of materials with the perovskite structure is much higher than that for spinel structure [ 13 ]. Due to this reason, an amorphous phase is always formed in the first stage regardless of the method of synthesis of nanoparticles with the perovskite structure from solutions. Preparation of the crystalline product requires additional temperature treatment that leads to the agglomeration of the nanoparticles. Investigations described in [ 14 ] showed that formation of the crystalline structure after precipitation from aqueous solutions and further heating the powder is a multi-stage process; single-phased crystalline produ (...truncated)


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Yulia Shlapa, Sergii Solopan, Anatolii Belous, Alexandr Tovstolytkin. Effect of Synthesis Method of La1 − xSr x MnO3 Manganite Nanoparticles on Their Properties, Nanoscale Research Letters, 2018, pp. 13, Volume 13, Issue 1, DOI: 10.1186/s11671-017-2431-z