A surface grafted conjugated polyelectrolyte (CPE) is formed by coupling a CPE by a coupling moiety to the surface of a substrate. The substrate can be of any shape and size, and for many uses of the surface grafted CPE, it is advantageous that the substrate is a nanoparticle or microparticle. Surface grafted CPEs are presented that use silica particles as the substrate, where a modified silane coupling agent connects the surface to the CPE by a series of covalent bonds. Two methods of preparing the surface grafted CPEs are presented. One method involves the inclusion of the surface being modified by the coupling agent and condensed with monomers that form the CPE in a grafted state to the substrate. A second method involves the formation of a CPE with terminal groups that are complimentary to functionality that has been placed on the surface of the substrate by reaction with a coupling agent. The surface grafted CPEs are also described for use as biosensors and biocides.