Co (III) ions high-spin configuration in nonstoichiometric Co3O4 films

Near-Infrared Spectroscopy—Its Versatility in Analytical Chemistry

“…The above bands of Co3O4 are assigned to d-d transitions, 4 A2 → 4 T1, of Co(II) at a tetrahedral cite. 64,65 A NIR DR spectrum of α-Fe2O3 shows a long tail feature in the region of 12000 -10000 cm -1 due to a charge-transfer (CT) transition that has maxima at 17000 and 14000 cm -1 . 66 HRGB shows characteristic peaks of Co(II) in spinel structure, but it is noted that HRGB does not yield a tail, due to Fe(III).…”

<b>SYNTHESIS AND CHARACTERIZATION OF Ni_0.4Co_2.6O₄ SPINEL MIXED OXIDES POWDER: STUDY OF ITS SURFACE PROPERTIES BY VOLTAMMETRY, X-RAY, FTIR, UV-VIS-NIR SPECTROSCOPY AND SCANNING ELECTRON MICROSCOPY</b>

“…This is probably due to the total substitution of Ni 2+ in octahedral sites for Co 2+ while in our case we have a partial replacing of Co 2+ in octahedral sites by Ni 2+ . Belova et al [12] reported that this transfer charges is due to the stabilization of Co 3+ in high spin configuration in the octahedral sub-lattice of the spinel structure although Miedzinska et al [10] considered that this is based upon the mechanisms of charge transfer between Co 2+ and Co 3+ and between oxygen and cobalt ions. So from our experimental value of the cell lattice and results already given in literature [13,14]…”

Third- and fifth-order susceptibilities of cobalt oxide nanoparticles dispersed in n-heptane

“…With basis on the previous works [7][8][9]19,20,25], we attribute the origin of the NPs nonlinearity to transitions associated to single-ion localized states, charge-transfer transitions, and free-carriers absorption. Possibly, the large value of the NL susceptibility is due to the laser frequency used that is near one-photon resonance with the absorption bands associated to the Co 2 and Co 3 centers and the two-photon resonance with the absorption band centered at 234 nm.…”

“…The measurements performed with colloids having f 1.35 × 10 −4 allowed the observation of an absorption band centered at ≈234 nm, shown in Fig. 2(b), which is also attributed to ligand-to-metal charge transfer [24,25].…”