Hydrothermal synthesis of Co-doped In₂S₃ micropompons and their physical properties

In_2−xCo_xS₃ (x = 0 to 0.1) micropompons (diameters ∼3–4 μm) consisting of ∼10–15-nm-thick randomly self-assembled nanoflakes were synthesized hydrothermally. X-ray study indicated a steady variation of lattice parameter ratio up to 5% Co. Detailed investigations of the Co incorporation in In₂S₃ were carried out by optical absorbance, room temperature photoluminescence (PL), and electron paramagnetic resonance (EPR) studies. Significant blue shift in the absorbance spectra was noticed due to the crystal-field splitting of Co²⁺ ions in the host lattice structure. Unlike the visible emission found in undoped In₂S₃, PL spectra of the Co-doped samples were recognized by a strong ultraviolet emission peak at ∼335 nm, introduced by the t_2g level of Co²⁺ ions, with maximum intensity for 5% Co. Room-temperature and low-temperature EPR spectra revealed octet paramagnetic bands up to 5% Co beyond which a single resonance band appeared.