SPECTROSCOPIC STUDIES ON COPPER SULFIDE SOLS

Abstract

The conversion of a “golden-brown” copper sulfide sol (particle diameter ~ 80–120 Å) to a “green” form has been studied by use of optical spectroscopy, scanning tunneling microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results indicate that the golden-brown sol is a poorly crystalline form of covellite, which converts to crystalline covellite (the “green” form) at a rate that depends upon the temperature and oxygen concentration of the sol. The valency of copper in the poorly crystalline golden-brown sol is found to be exclusively copper (I), while the green sol has a component of copper(II), which accounts for an absorption band observed in the visibl..