pH-triggered SERS via modulated plasmonic coupling in individual bimetallic nanocobs.

DOI: 10.1002/smll.201002169 Hybrid organic–inorganic nanostructures are a critical platform for a wide range of chemical and biological sensing applications. [ 1– 3 ] Optical responses, such as Raman scattering and absorbance, serve as a signature for specifi c chemical groups and can be used for identifi cation and quantifi cation of analyte molecules. [ 4 ] Raman scattering, which is the quantized vibration signature of a molecule, can be enhanced when the molecule is subjected to the enhanced electromagnetic fi eld caused by plasmon resonance in the vicinity of plasmonic nanostructures. [ 5– 7 ] It is well known that the plasmon absorption (resonance condition) and electromagnetic coupling between metal nanoparticles can be tuned by external ambient, shape, dimensions, interparticle distance, and orientation. [ 8– 10 ] Of special interest is the coupling of surface plasmon resonances (SPR) in adjacent metal nanostructures separated by nanoscale gaps, which can modulate the optical absorption through coupling of plasmonic resonances. [ 11 ]