β-In 2 S 3 and β-In 2 S 3 :Co 2+ single crystals were grown by the chemical transport reaction method using In 2 S 3 , S, and ZnS as starting materials and (ZnCl 2 + I 2 ) as a transport agent. The single crystals crystallized into a tetragonal structure. The indirect optical energy band gaps of the single crystals at 298 K were found to be 2.240 eV and 1.814 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. The direct optical energy band gaps were found to be 2.639 eV and 2.175 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. Impurity optical absorption peaks were observed for the β-In 2 S 3 :Co 2+ single crystal. These impurity absorption peaks were assigned, based on the crystal field theory, to the electron transitions between the energy levels of the Co 2+ ion sited in T d symmetry.

-Hexagonal boron nitride (BN) films were prepared. The process involved, spraying BN powder-dispersed H 3 BO 4 -BCl 3 -ethyl alcohol solution on quartz plates, and the drying off quartz plates before, and annealing at 1070 °C in a nitrogen atmosphere. The optical energy band gap of the BN films was 5.28 eV. Photoluminescence peaks with energies of 3.44, 3.16, 2.97, and 2.35 eV at 10 K were observed and analyzed. Accordingly, these have resulted from donor-acceptor pair recombinations.

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