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Nanoparticles of [Fe(NH 2 ‐trz) 3 ]Br 2 ⋅3 H 2 O (NH 2 ‐trz=2‐Amino‐1,2,4‐triazole) Prepared by the Reverse Micelle Technique: Influence of Particle and Coherent Domain Sizes on Spin‐Crossover Properties
Author(s) -
Forestier Thibaut,
Kaiba Abdellah,
Pechev Stanislav,
Denux Dominique,
Guionneau Philippe,
Etrillard Céline,
Daro Nathalie,
Freysz Eric,
Létard JeanFrançois
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900297
Subject(s) - spin crossover , nanoparticle , particle size , hysteresis , pulmonary surfactant , materials science , spin transition , crystallography , transition metal , analytical chemistry (journal) , transition temperature , diffraction , nanotechnology , chemistry , condensed matter physics , physics , superconductivity , thermodynamics , organic chemistry , optics , catalysis
By changing the surfactant/water ratio , nanoparticles of the iron(II) spin crossover material, [Fe(NH 2 ‐trz) 3 ]Br 2 ⋅ 3 H 2 O (with NH 2 ‐trz=4‐amino‐1,2,4‐triazole), have been synthesised from 1 μm down to 30 nm (see figure). Magnetic and reflectivity experiments indicate that the critical size for observing a thermal hysteresis in this 1D polymer family is around 50 nm, and powder X‐ray diffraction shows that particles of about 30 nm are constituted by about one coherent domain.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(NH 2 ‐trz) 3 ]Br 2 ⋅3H 2 O (with NH 2 trz=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.