Temperature and compositional studies of photoluminescence and optical absorption edge spectra of γ 1 -(Ga x In 1-x ) 2 Se 3 mixed crystals with x = 0.1 -0.4 are performed. Exciton and impurity-related photoluminescence bands are revealed at low temperatures and Urbach shape of the absorption edge is observed in the temperature range 77 -300 K. Temperature and compositional dependences of the photoluminescence band spectral positions and halfwidths as well as optical pseudogap and absorption edge energy width are investigated. Mechanisms of radiative recombination and optical absorption as well as crystal lattice disordering processes in γ 1 -(Ga x In 1-x ) 2 Se 3 solid solutions are studied.

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Colloidal AgInS2 quantum dots (QDs) with intense broadband photoluminescence (PL) were synthesized in aqueous solutions in the presence of glutathione at mild conditions. Size-selective fractioning of QDs was performed by repeated centrifugation of the colloidal solution with the addition of 2-propanol. Based on the optical absorption and PL data, the dependences of the band gap and the PL maximum position on the QD size are analyzed. The Raman spectra of AgInS2 QDs exhibit only a slight variation with decreasing QD size explained by phonon confinement. Changes in the Raman spectra with increasing laser power density are most likely related to photoinduced oxidation of the AgInS2 QD surface with the formation of S-O bonds.