Cuprous oxide is light sensitive and can be made into a B&W paper that is about the same speed as Kodabromide. I have several publications on that but no patent. They are in Kodak Research Disclosures. Copper salts at this level adversely affect AgX emulsions and probably cannot be used. I may have to use Calcium, Magnesium, or something stronger like Barium! The last one is probably not a good idea.