Microfluidic devices with three-dimensional gold nanostructure for surface enhanced Raman scattering

Rapid and sensitive chemical sensing using microfluidic device equipped with sterically-bulky three-dimensional gold nanostructure (Au3D) was demonstrated. Au3D was expected as surface enhanced Raman scattering (SERS) active structure. Au3D was fabricated by convective selfassembly known as “coffee-ring” of the mixed solution of gold colloidal nanoparticle and polystyrene latex particle. SERS measurements of a trace amount of 4,4'-bipyridine (4bpy) in aqueous solution were performed using Au3D in batch and flow format, and typical spectrum of 4bpy with enhanced peaks were immediately observed after dropping (batch) or injecting (flow). While detection limit was about 10 nM 4bpy in batch measurement, detection of further enhanced spectrum of 1 nM 4bpy was accomplished in flow measurement. We confirmed that Au3D was available for convenient SERS optofluidic measurement.