Nanocrescent SERS probes

Techniques for single molecular level detection and recognition of biomolecules are important in medical, defense, and environmental sensing applications. In this field, optical methods based on spectroscopy have been predominant owing to their non-destructive nature. Especially promising methods are label-free schemes such as Raman or extinction spectroscopy. Recently these spectroscopic techniques gain reinforced interests due to technical advances in metallic nanostructures. Under optical excitations of proper frequency, a metallic nanostructure sustains a plasmon resonance that result in highly enhanced local electromagnetic fields and distinct spectral extinction characteristics. For sensing applications, the field enhancement is utilized for surface-enhanced Raman spectroscopy (SERS) and the spectral extinction characteristics are used to detect the changes in local refractive index. The plasmon resonance characteristic depends strongly on the topology of each nanostructure. The shape of the nanostructures; however, has been limited to be symmetric and/or particulate due to fabrication constraints. We develop the nanofabrication techniques and spectroscopic applications of nanostructures with unconventional shapes for ultrasensitive nanobiophotonic applications.

A nanoparticle in a wild world: A schematic view of a reduced symmetry nanoparticle interacting with external radiation and molecules