Spin Crossover–Few-Layer Graphene Nanocomposites: Synthesis and Magnetic Properties of Fe(NH2trz)3A2@FLG (A = Cl–, Br–)

Abstract

Stable nanoparticles capable of experiencing spin crossover with hysteresis on curves of the µ_eff(T) dependence near ambient temperature have been synthesized. The earlier synthesized complexes [Fe(NH₂trz)₃]Cl₂·H₂O and [Fe(NH₂trz)₃]Br₂·H₂O exhibiting sharp spin crossover with hysteresis are used for the preparation of the nanocomposites. Few-layer graphene (FLG) formed by the microwave heating of the intercalated polydicarbonfluoride compound with acetone served as the basis. Nanoparticles Fe(NH₂trz)₃Cl₂@FLG (SCO1-n) and Fe(NH₂trz)₃Br₂@FLG (SCO2-n) (n = 1–3) have been prepared (n indicates time (h) of the treatment of the initial particles with ultrasound). The effective hydrodynamic diameter of particles of the complexes in ethanol is determined by photon correlation spectroscopy. The structures and microstructures of the samples are studied by high resolution transmission electron microscopy. The study of the µ_eff(T) dependence shows that all synthesized composites exhibit crossover with hysteresis on the µ_eff(T) curves. The temperature and character of the transition depend substantially on the particle size. The variation of the ultrasonication time during the preparation of the composites makes it possible to purposefully modify their magnetic properties.