Abstract: A method for the synthesis of a semiconductor nanoparticle within a protein template. The semiconductor is selected from cadmium selenide, cadmium telluride, zinc selenide, zinc sulfide and zinc telluride. The process comprises forming a reaction mixture by combining in a liquid medium a cation source selected from cadmium or zinc ions and an anion source selected from sulfur, selenium or tellurium ions in the presence of a source of a protein which is capable of acting as a template for the formation of nanoparticles and maintaining said liquid medium at a temperature of at least 24° C. for a time sufficient to permit nanoparticle formation within the protein template, with the proviso that when the cation source is cadmium, the anion source is not sulfur.