Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-ray Absorption, Emission, and Photoelectron Spectroscopies

Abstract

Electronic structure of nickel nanoparticles encapsulated in carbon was characterized by photoelectron, X-ray absorption, and X-ray emission spectroscopies. Experimental spectra are compared with the density of states calculated in the frame of the density functional theory.The carbon shell of Ni nanoparticles has been found to be multilayer graphene with significant (about 6%) amount of Stone-Wales defects. Results of the experiments evidence protection of the metallic nanoparticles from the environmental degradation by providing a barrier against oxidation at least for two years. Exposure in air for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles with coverage of functional groups.

Role of carbon in the formation of the structure and magnetic properties of Ni@CNx nanoclusters under reactive magnetron deposition

“…• C, at C/Ni = 60/40T cr ≈ 160 • C. We see that as the carbon concentration in the series B and C films increases, the magnetization decreases, in full accordance with the model [12][13][14], suggesting the formation of an increasingly saturated solid solution of carbon in nickel. Subsequently, as the substrate temperature rises, the nickel phase in the nanoclusters crystallizes FIG.…”

“…The supersaturated solid solution decomposes into nickel and pure carbon with the displacement of C atoms to the surface of the nickel crystallite, forming a nickel nanocluster with a carbon shell Ni@C [12][13][14].…”

Atomic, electronic and magnetic structure of graphene/iron and nickel interfaces: theory and experiment

“…For the experimental survey, we used Fe@C and Ni@C nanoparticles, the composition of which is a metallic core covered by almost planar few-layer graphene with a small amount of defects (for the details of synthesis and characterization of these nanoparticles see Res. [42,49]). …”

Electronic Structure of Hollow Graphitic Carbon Nanoparticles Fabricated from Acetylene Carbon Black

“…Therefore, it is important to study the electronic structure of the EK aemission bands of hollow carbon nanoparticles in order to understand the energy distribution of Ep electrons. X-ray emission spectroscopy provides some information concerning the distribution of occupied valence states below the Fermi level, and it has been used to study a variety of carbon materials (13)(14)(15)(16)(17)(18)(19)(20). It is, thus, a useful method for investigating the electronic structure of HGCNs (particularly for the characterization of peculiarities of chemical bonding of atoms in carbon materials), whereas common methods (e.g., X-ray diffraction) have limitations when studying nanoparticles and nanoparticles with low crystallinity.…”