Chalcocite, Cu2S, and djurleite, Cu1.94-1.96 S, copper sulfide nanoparticles have been synthesized. They have been characterized using a multitude of methods. Using x-ray photoelectron spectroscopy (XPS), the binding energies of the core electrons have been measured for each type of nanoparticle. Using powder x-ray diffraction and ultraviolet-visible spectroscopy, the crystal structures have been determined and it has been found that the chalcocite nanoparticles have indirect band gap transitions, whereas the djurleite nanoparticles have direct band gap transitions. Using electron microscopy it has been found that the nanoparticles are both single crystalline with size distributions that vary between 8 and 20 nm for the djurleite nanoparticles, and between 10 and 200 nm for the chalcocite nanoparticles. The djurleite nanoparticles have been incorporated into a solar cell device in combination with C60 and using ultraviolet photoelectron spectroscopy (UPS), the band structure of the nanoparticles has been evaluated.