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Construction of Organic Magnetic Metals and Magnetic Composits using Spin-Polarized Donors

使用自旋极化供体构建有机磁性金属和磁性复合材料

基本信息

批准号：
13440206
负责人：
IZUOKA Akira
金额：
$ 8.51万
依托单位：
Ibaraki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

The research project was carried out syntheses of the cross-conjugated and hyper-conjugated spin-polarized donor molecules and preparation of their adsorbed gold nanoparticles in order to construct the magnetic organic-inorganic nano-composites.Several Nano-composites consisted of gold nanoparticle were prepared by the chemical adsorption of some nitroxide radicals on the surface of ca. 4 nm gold nanoparticles which were synthesized by reduction of HAuCl_4 at the presence of tetraocyl ammonium bromide. The obtained solid samples of the nanoparticles showed singlet ESR signals that the line widths were within 1.5 〜 30 mT. Among them, the nanoparticles functionallized by the spin polarized donor typed nitronyl nitroxide exhibits extraordinarily broad signal. Molecular orbital calculation of this radical indicated a large spin polarization at the site of sulfur atom that is the attaching site to the gold surface. As the concentration of the spin polarized donor radical on the surface of nanoparticles was reducing by mixing a diamagnetic ligand, the line width became small. These results indicated that the line broadening of ESR signal rationalized by considering of the assistant of the conduction electrons of gold nanoparticle for the spin relaxation, although the line width of ESR signals generally correlates with the spin-spin relaxation among the localized spins of radicals.While the interaction of the conduction electrons with localized spins was recognized for the nano-composite samples, it was found by the measurement of magnetic susceptibility that the magnetic interaction between radicals on gold nanoparticles was paramagnetic. The researches for the construction of the magnetic nano-composite are in progress.

本课题以构建磁性有机-无机纳米复合材料为目的，开展了交叉共轭和超共轭自旋极化给体分子的合成及其吸附金纳米粒子的制备研究，通过氮氧自由基化学吸附法制备了几种由金纳米粒子组成的磁性有机-无机纳米复合材料。在溴化四辛基铵存在下，用HAuCl_4还原法合成了4 nm的金纳米粒子。所获得的纳米颗粒的固体样品显示单重态ESR信号，其线宽在1.5 ~ 30 mT内。其中，由自旋极化供体型硝酰基氮氧化物功能化的纳米颗粒表现出非常宽的信号。该自由基的分子轨道计算表明，大的自旋极化的硫原子的网站，这是连接到金表面的网站。当纳米颗粒表面的自旋极化的给体自由基的浓度通过混合抗磁性配体而降低时，线宽变小。这些结果表明，尽管ESR信号的线宽一般与自由基局域自旋之间的自旋-自旋弛豫有关，但考虑到金纳米粒子的导电电子对自旋弛豫的辅助作用，ESR信号的线宽变宽是合理的。通过磁化率的测量发现，金纳米颗粒上的自由基之间的磁相互作用是顺磁性的。磁性纳米复合材料的构建研究正在进行中。