  Surface-enhanced Raman spectroscopy (SERS) is a sensitive vibrational
spectroscopy technique that can enable fast and non-destructive detection of
trace molecules. SERS substrates are critical for the advancement of the SERS
application. By incorporating SERS substrates into microfluidic devices, the
function of microfluidic devices can be extended, and an efficient on-site
trace analysis platform with powerful sensing capabilities can be realized. In
this paper, we report the fabrication of a rapid and sensitive optofluidic SERS
device using a unique Au nanorod array (AuNRA) with a plasmon resonance
frequency in the near IR region. The highly stable and reproducible AuNRA were
fabricated by a facile dynamic oblique angle deposition technique. A typical
spectrum of 4,4-bipyridine (BPY) with enhanced peaks was observed within a few
seconds after the injection of an aqueous solution BPY. Time-course
measurements revealed an outstandingly quick response of SERS in this system.
Using the AuNR microfluidic device, approximately 2x10-12 mole molecules were
enough to produce detectable SERS signals. This work demonstrates rapid and
sensitive chemical sensing using an optofluidic device equipped with a unique
noble metal nanorod array.
