Gold nanoparticles and nanostructures in optical biosensors

Noble metals in their 'nano' dimensions show unique electromagnetic phenomena, localised surface plasmon resonance, in response to optical excitation. This phenomenon was reported long ago by Michael Faraday in 1850, but applications of these towards sensors and biosensors have occurred only after efforts towards functionalising these nanoparticles with receptor molecules have been successful. The use of nanoparticles and structures has been further invigorated with the increasing interest in surface enhanced Raman scattering. To optimally exploit these electromagnetic effects for optical biosensing, various morphologies of gold, namely rods, stars, core shell, have been tried. This short review traces the recent developments in this area, highlighting a small section of significant reports in this vibrant field of research.