Synthesis and investigation of the structure of nanocomposites based on nickel nanoparticles dispersed in a phthalocyanine matrix

Abstract

A method based on doping of pure nickel phthalocyanine (NiPc) with a polycrystalline potassium powder at relatively low temperatures (300°C) has been proposed for the synthesis of a magnetic nanocomposite containing nickel nanoparticles stabilized in the NiPc matrix. The structural analysis of the synthesized nanoparticles and changes in the NiPc initial matrix has been performed using X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy. It has been found that, at the doping level used in this study, the synthesized samples of the K x NiPc nanocomposites contain from 9 to 18% Ni in the form of metallic magnetic nanoparticles with an average size of more than 40 nm. It has been shown that the formation of nanoparticles is accompanied by a relative misorientation of persistent NiPc molecules with the unchanged structure of each of these molecules. The stabilization of nickel nanoparticles by the phthalocyanine matrix leads to the fact that the synthesized nanocomposites acquire time-conserving magnetic properties.

Formation of nickel nanoparticles and magnetic matrix in nickel phthalocyanine by doping with potassium

“…The distance between molecular layers in NiPc structure is about 3.5 Å (Figure 3 a) and, therefore, in the FT analysis of Ni K-EXAFS the structural model for the term χ NiPc (k) in ( 4) included only one NiPc molecule. For pristine NiPc it was revealed [21] that to obtain agreement of theoretical F(R) with the experimental one in the extended R-range (up to ~ 5.5 Å) using k min ~ 2.5 Å for FT of Ni K-EXAFS one needs to account for single-scattering (SS) paths on the three nearest shells of the absorbing Ni added with three approximately linear multiple scattering (MS) paths schematically illustrated in Figure 3b. Therefore, to retain the verification of the used structural models in the extended R-range and simultaneously, to simplify these models by reducing the effect of photoelectron MS processes on the determined values of first shell's structural parameters, the fit by IFEFFIT code [22] was performed for F(R) obtained using FT of…”

Formation of nickel magnetic nanoparticles and modification of nickel phthalocyanine matrix by sodium doping

“…To mitigate the influence of photoelectron multiple scattering on the parameters of the first coordination sphere, fitting in the R space was carried out in the interval 0.35 < R < 1 nm -1 using the IFEFFIT program package [17] for the function F(R) obtained by applying the Fourier transformation to function k 2 χ(k) in the interval 1.15 ≤ k ≤ 4.5 nm -1 . The accuracy of the structural parameters determined from the Ni K-EXAFS spectra was checked in [10] based on the example of undoped NiPc and Ni foil spectra.…”

“…3 (curve a)) and Ni foil (Fig. 3 (curve e)) was made in [10]. The corresponding structural parameters for a number of spheres near an absorbing Ni atom in a Ni nanoparticle and NiPc molecule that were obtained from the EXAFS spectra are presented in Table 2.…”

“…The magnetic properties of alkali-doped metal phthalocyanines were studied in [7][8][9], where it was found that metal nanoparticles arise in the MePc matrix under certain doping conditions. In [10], nickel nanoparticles were prepared by vapor-phase doping of the NiPc matrix by potassium at 300°C and high doping levels. The resulting materials K x NiPc (x = 1.8, 2.5, and 3.2) demonstrated persistent magnetic properties, which were attributed to nickel nanoparticles.…”