Forestier Thibaut, Kaiba Abdellah, Pechev Stanislav, Denux Dominique, Guionneau Philippe, Etrillard Céline, Daro Nathalie, Freysz Eric, Létard Jean-François
CNRS, Université de Bordeaux, ICMCB, 87 Av. Doc. A. Schweitzer, 33608 Pessac, France.
Chemistry. 2009 Jun 15;15(25):6122-30. doi: 10.1002/chem.200900297.
This paper describes the synthesis of iron(II) spin-crossover nanoparticles prepared by the reverse micelle technique by using the non-ionic surfactant Lauropal (Ifralan D0205) from the polyoxyethylenic family. By changing the surfactant/water ratio, the size of the particles of [Fe(NH2-trz)3]Br2.3H2O (with NH2trz=4-amino-1,2,4-triazole) can be controlled. On the macroscopic scale this complex exhibits cooperative thermal spin crossovers at 305 and 320 K. We find that when the size is reduced down to 50 nm, the spin transition becomes gradual and no hysteresis can be detected. For our data it seems that the critical size, for which the existence of a thermal hysteresis can be detected, is around 50 nm. Interestingly, the change of the particle size induces almost no change in the temperature of the thermal spin transition. A systematic determination of coherent domain size carried out on the nanoparticles by powder X-ray diffraction indicates that at approximately 30 nm individual particles consist of one coherent domain.
本文描述了通过反胶束技术，使用来自聚氧乙烯家族的非离子表面活性剂月桂醇聚醚（Ifralan D0205）制备铁（II）自旋交叉纳米颗粒的方法。通过改变表面活性剂/水的比例，可以控制[Fe(NH2-trz)3]Br2·3H2O（其中NH2trz = 4-氨基-1,2,4-三唑）颗粒的大小。在宏观尺度上，这种配合物在305 K和320 K时表现出协同热自旋交叉现象。我们发现，当尺寸减小到50 nm时，自旋转变变得逐渐变化，并且检测不到滞后现象。根据我们的数据，似乎能够检测到热滞后现象的临界尺寸约为50 nm。有趣的是，颗粒尺寸的变化几乎不会引起热自旋转变温度的变化。通过粉末X射线衍射对纳米颗粒进行的相干畴尺寸的系统测定表明，在大约30 nm时，单个颗粒由一个相干畴组成。
