The Fabrication And Properties Of The Triazole-based Iron(â…¡) Nanocomposites

Spin-corssover(SCO) complexes, as the frontier filed of molecular magnetic materials, exhibit promising applications in sensors, display materials, information storage, and molecular switch and so on due to the controllable bistable properties. Thus, SCO materials have attracted extensive attention of scientists. As the magnetic materials with spin-crossover properties, though the triazole-based iron(II) polymers can retain their magnetic and cooperative behavior at the nano-size, the fragility of SCO behavior and poor processabiltiy of the triazole-based iron(II) nanomaterials limit the applications in actual devices. In addition, multifunctional SCO nanomaterials are the demands of development of nanotechnology. Consequently, the synthesis and design of different newfashioned SCO nanocomposites have important theoretical and realistic significance. The work in our paper is focused on the synthesis and design of triazole-based iron(II) nanocomposites, where the strategies are proposed from basal composite, the decoration of gold nanoparticles and multistage spin-crossover behaviors. The interaction between composites is investigated, especially the spin-crossover property of triazole-based iron(II) nanoparticles.1. To investigate the influence of different substrates on the morphologies and spin-crossover properties of the triazole-based iron(II) nanomaterials, the corresponding SCO nanocomposites have been obtained through different elaborated methods, using graphene, anodic aluminum oxide(AAO) membrane and cation-exchangeable resin as substrates, respectively. The nanocompsoites as following: i) the triazole-based iron(II) nanocomposites were obtained using graphene as substrate, where the [Fe(Htrz)2(trz)](BF4) nanoparticles synthesized through microemulsion and graphene with different quality ratios were reacted in the ethanol. Electron microscope displayed that [Fe(Htrz)2(trz)](BF4) nanoparticles(ca. 50 nm) distributed uniformly onto the surface of the graphene. And magnetism test showed the spin transition temperatures of the [Fe(Htrz)2(trz)](BF4) nanoparticles in nanocomposites shifted to the higher temperature. ii) the growth situation of [Fe(Htrz)2(trz)](Cl O4) and [Fe(NH2-trz)2(NH-trz)](Cl O4) nanaomaterials in the channel and on the surface of AAO membrane were studied by immersing the AAO membranes into different precursor solutions. The results suggested that the spatial confinement of AAO membrane had a great influence on the morphology of the triazole-based iron(II) nanocomposites. The significant two-step spin transitions are measured in the magnetism. iii) the [Fe(Htrz)2(trz)](BF4) nanomaterials were successfully fabricated through immersing resins into the precursor solutions, which displayed as nanorod arrays on the surface of resin beads. SEM intuitively showed the growth situation of SCO nanorods on the surface of resins with different immersing time, and magnetism test demonstrated that the spin-crossover phenomenon was well preserved in the particular nanostructred materials.2. To investigate the influence of photo-thermal plasmonic effect of gold nanoparticles on the laser-induced spin transition of triazole-based iron(II) nanomaterials, the multifunctional nanocomposites with spin-crossover and photo-thermal heating properties were fabricated using two different dimensions of the surface functionalized [Fe(Htrz)2(trz)](BF4)@Si O2 as supports to gold nanoparticles. The Raman spectrum indicated that the plasmonic gold nanopartilces made an efficient photo-thermal heating in the SCO@Si O2@Au nanocomposites, leading to a ~100 times reduction of laser energy needed for spin state switching compared with SCO@Si O2. The magnetic study demonstrated that the embedded Au nanopartilces improved the spin transition temperatures decreased the widths of hysteresis loops of [Fe(Htrz)2(trz)](BF4)@Si O2@Au nanoparticles, which was attributed to the good thermal conductivity of gold nanoparticles.3. On the basis of few studies in the multistep spin-crossover behaviors of SCO nanocomposites induced by the different organic ligands, the [Fe(Htrz)2(trz)](BF4)@ [Fe(NH2-trz)2(NH-trz)](BF4) core-shell nanocomposite was synthesized using facile continuous microemulsion method. SEM was used to monitor the growth situation of [Fe(Htrz)2(trz)](BF4), [Fe(NH2-trz)2(NH-trz)](BF4) and [Fe(Htrz)2(trz)](BF4)@ [Fe(NH2-trz)2(NH-trz)](BF4) in microemultion with different time. The expected step like spin transition behavior of the core-shell nanocomposite was obtained.