A toner composite material includes toner particles that include a sulfonated polyester and a wax and metal nanoparticles disposed on the surface of the toner particles. A method includes providing such toner composite materials, fusing the material to a substrate and covalently linking a ligand to the surface of the silver nanoparticles via a thiol, carboxylate, or amine functional group. Detection strips include a substrate and such toner composite materials fused on the substrate.