A cyanide-functionalized gold nanoparticle. A method of making cyanide-functionalized gold nanoparticles includes forming an aqueous reaction mixture comprising a gold precursor and glycine, keeping the reaction mixture at about 18° C. to about 50° C. for at least 6 days to provide formation of the cyanide-functionalized gold nanoparticles, and isolating the cyanide-functionalized gold nanoparticles from the reaction mixture. A method of analyzing a sample, comprising contacting cyanide-functionalized gold nanoparticles with the sample and performing an analytical method on the sample. A sensor comprises cyanide-functionalized gold nanoparticles.