Optofluidic Devices with Surface-Enhanced Raman Scattering Active Three-Dimensional Gold Nanostructure

Rapid and sensitive chemical sensing using a microfluidic device equipped with a sterically bulky three-dimensional gold nanostructure (Au3D) was demonstrated. Au3D was expected as a surface-enhanced Raman scattering (SERS) active structure. Au3D was fabricated by convective self-assembly, known as a "coffee-ring", of the mixed solution of gold colloidal nanoparticles and polystyrene latex particles. 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 spectra of 4bpy with enhanced peaks were immediately observed after dropping (batch) or injecting (flow). While the detection limit was about the 10 nM 4bpy in batch measurement, the detection of a further enhanced spectrum of 1 nM 4bpy was accomplished in flow measurement. We confirmed that Au3D was available for convenient SERS optofluidic measurement.