is to be functionalized the desired density of the coating 114 for a given application the desired melting point for the coating 114 the identity of any other materials which constitute the coating 114 and the technique by which the raman active particle 110 is to be prepared in one embodiment the element in the elemental oxide of the coating 114 includes at least about 50 mole silicon in another embodiment the element in the elemental oxide of the coating 114 includes at least about 30 mole silicon yet in another embodiment the element in the elemental oxide of the coating 114 comprises substantially silicon in yet another embodiment the coating 114 includes a composite coating a composite coating comprises oxides of one or more elements selected from a group consisting of si b al ga in sc y la ti zr hf v nb ta cr mn fe co ni li na k rb cs be mg ca sr ba zn cd ge sn and pb furthermore the coating 114 may include multilayer coatings 114 each of the coating layers 114 in the multilayer coating 114 individually may include different coating compositions such as 50 mole silicon oxide in one coating layer and a composite coating in another coating layer the raman active particle 110 includes one or more raman active analytes 116 the raman active analyte 116 is a molecule which exhibits raman scattering when in the vicinity of a metallic.