Methods of forming plasmonic diamond films are provided. In an embodiment, such a method comprises forming a first layer of diamond on a substrate; depositing a layer of a metal on a surface of the first layer of diamond to form an as-deposited layer of metal; exposing the as-deposited layer of metal to a plasma treatment to convert the as-deposited layer of metal to a plurality of discrete regions of the metal on the surface of the first layer of diamond; and forming a second layer of diamond on the plurality of discrete regions of metal to form the plasmonic diamond film comprising a plurality of plasmonic nanoparticles.