Photonic sensors are being applied to a wide variety of sensing application. Such sensors can be based on fluorescence spectroscopy , infrared spectroscopy , plasmonic based sensors , or Raman spectroscopy based. Of these, Surface Enhanced Raman Scattering (SERS) is an emerging optical based technique that has shown tremendous potential for trace analysis of contaminants relevant to the food or environmental sectors . In SERS, the Raman signal is significantly enhanced at the surface of metallic nanostructures. Enhancement is generally divided into chemical and electromagnetic enhancements . Chemical enhancement relates to the increased hyperpolarizability of the target molecule upon adsorption onto the SERS surface while electromagnetic enhancement occurs due to the plasmonic nanogaps or "hotspots" located in between the metallic nanostructures. In the last couple of decades, a number of approaches have been investigated for fabrication of SERS substrates . Typically, fabrication techniques employed include UV photolithography , electron beam lithography , nanoimprint lithography , and templating . The morphology of the nanostructures includes particles , triangles or sphere .