Jonathan C. Luque-Ceballos,a Alvaro Posada-Borbón,b María E. Trujillo-Camacho,c Ronaldo Herrera-Urbina,c R. Aceves,a Alvaro Posada-Amarillasa
aDepartamento de Investigación en Física, Universidad de Sonora
bMSc in Applied Physics Program, Chalmers University of Technology
cDepartamento de Ingeniería Química y Metalurgia, Universidad de Sonora
Copper sulfide semiconducting nanoparticles have attracted considerable attention because of their outstanding photochemical properties. Absorbance and transmittance of these nanoparticles have been measured and utilized to estimate the energy band gap which is about 2.29 eV. Their structural characterization by means of TEM and XRD measurements has shown an hexagonal structure characteristic of covellite phase, and a main Raman peak has been observed at about 474 cm-1. Utilizing the static and dynamical approaches of Density Functional Theory and a simple ground-state structural model which resembles the covellite arrangement of atoms, the theoretical Raman activity was obtained at 489 cm-1, corresponding to a symmetrical stretching mode of a three-membered fragment of sulfur atoms, of a C2v symmetry pentamer cluster structure. The experimental UV-vis absorbance spectrum is explained in terms of calculated excited state transitions in the observed energy range. The absorption peaks are assigned mainly to σ→σ*, π→π*, and σ→π* type transitions. The photocatalytic activity of CuS nanocrystals is examined in the UV and visible regions.
