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Abstract In this study, the structure and transport properties of two polymorphs, nanoparticles and nanorods, of the iron(II) triazole [Fe(Htrz)₂(trz)](BF₄) spin crossover complex were compared. Conductive atomic force microscopy was used to map the electrical conductivity of individual nanoparticles and nanorods. The [Fe(Htrz)₂(trz)](BF₄) nanorods showed significantly higher conductivity compared to nanoparticles. This difference in electrical conductivity is partially associated to the different Fe–N bond lengths in each of the polymorphs, with an inverse relationship between Fe–N bond length and conductivity. Transport measurements were done on the nanorods for both high spin (at 380 K) and low spin (at 320 K) states under dark and illuminated conditions. The conductance is highest for the low spin state under dark conditions. In illumination, the conductance change is much diminished. 

Abstract In an effort to reconcile the various interpretations for the cation components of the 2p_3/2observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p_3/2core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p_3/2core levels of NiFe₂O₄thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles Ni_xCo_1−xFe₂O₄(x= 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe₂O₄thin film. Surface-to-bulk core level shifts are also observed in CoFe₂O₄and NiCo₂O₄thin films but not as significantly as in NiFe₂O₄thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles. 

Bismuth ferrite (BiFeO3) nanocomposites were synthesized using a novel nano-agitator bead milling method followed by calcination. Bismuth oxide and iron oxide nanoparticles were mixed in a stoichiometric ratio and milled for 3 h and calcined at 650 °C in air. X-ray diffraction with Rietveld refinement, scanning electron microscopy, and transmission electron microscopy techniques were used to elucidate the structure of BiFeO3. The particle diameter was found to be ∼17 nm. Magnetic and electrical measurements were performed, and these results were compared with those of similar methods. Mostly, BiFeO3 was obtained with minor secondary phase formation. The resulting powder was weakly ferromagnetic with a remnant magnetization of 0.078 emu/g. This can be attributed to residual strain and defects introduced during the milling process. Electrical testing revealed a high leakage current density that is typical of undoped bismuth ferrite. 

This paper describes the 3D printing of a ternary composite of polydimethylsiloxane (PDMS) and nanoparticles of iron oxide and barium titanate. The composite was printed using a commercially available 3D printer. Thermal curing of the composite during printing allowed for overall low process times of a few minutes. Scanning electron microscopy indicated uniform composite layers. The resulting composite films showed ferromagnetic behaviour, and applicability in magnetic actuation and piezoelectric energy harvesting. 

Abstract Flexible nanocomposite films, with cobalt ferrite nanoparticles (CFN) as the ferromagnetic component and polyvinylidene fluoride–trifluoroethylene (PVDF-TrFE) copolymer as the ferroelectric matrix, were fabricated using a blade coating technique. Nanocomposite films were prepared using a two-step process; the first process involves the synthesis of cobalt ferrite (CoFe₂O₄) nanoparticles using a sonochemical method, and then incorporation of various weight percentages (0, 2.5, 5, and 10%) of cobalt ferrite nanoparticles into the PVDF-TrFE to form nanocomposites. The ferroelectric polarβphase of PVDF-TrFE was confirmed by x-ray diffraction (XRD). Thermal studies of films showed notable improvement in the thermal properties of the nanocomposite films with the incorporation of nanoparticles. The ferroelectric properties of the pure polymer/composite films were studied, showing a significant improvement of maximum polarization upon 5wt% CFN loading in PVDF-TrFE composite films compared to the PVDF-TrFE film. The magnetic properties of as-synthesized CFN and the polymer nanocomposites were studied, showing a magnetic saturation of 53.7 emu g⁻¹at room temperature, while 10% cobalt ferrite-(PVDF-TrFE) nanocomposite shows 27.6 emu/g. We also describe a process for fabricating high optical quality pure PVDF-TrFE and pinhole-free nanocomposite films. Finally, the mechanical studies revealed that the mechanical strength of the films increases up to 5 wt% loading of the nanoparticles in the copolymer matrix and then decreases. This signifies that the obtained films could be suited for flexible electronics.