The present invention is directed to an adsorbent for removing arsenic species from ground water andor surface water systems. The film includes a polymeric layer, and a metallic nanoparticle having a cross-section, the metallic nanoparticle being embedded in the polymeric layer. The methods include the use of electrophoretic tag probes or e-tag probes, comprising a detection region and a mobility-defining region called the mobility modifier, both linked to a target-binding moiety.