Proceedings Article | 10 May 2012
Proc. SPIE. 8401, Independent Component Analyses, Compressive Sampling, Wavelets, Neural Net, Biosystems, and Nanoengineering X
KEYWORDS: Biosensing, Principal component analysis, Atrial fibrillation, Nanoparticles, Silver, Diagnostics, Surface enhanced Raman spectroscopy, Raman spectroscopy, Bacteria, Nanorods
Since its discovery more than 30 years ago, surface-enhanced Raman scattering (SERS) has been recognized as a highly
sensitive detection technique for chemical and biological sensing and medical diagnostics. However, the practical
application of this remarkably sensitive technique has not been widely accepted as a viable diagnostic method due to the
difficulty in preparing robust and reproducible substrates that provide maximum SERS enhancement. Here, we
demonstrate that the aligned silver nanorod (AgNR) array substrates engineered by the oblique angle deposition method
are capable of providing extremely high SERS enhancement factors (>10<sup>8</sup>). The substrates are large area, uniform,
reproducible, and compatible with general microfabrication process. The enhancement factor depends strongly on the
length and shape of the Ag nanorods and the underlying substrate coating. By optimizing AgNR SERS substrates, we
show that SERS is able to detect trace amount of toxins, virus, bacteria, or other chemical and biological molecules, and
distinguish different viruses/bacteria and virus/bacteria strains. The substrate can be tailored into a multi-well chip for
high throughput screening, integrated into fiber tip for portable sensing, incorporated into fluid/microfluidic devices for
in situ real-time monitoring, fabricated onto a flexible substrate for tracking and identification, or used as on-chip
separation device for ultra-thin layer chromatography and diagnostics. By combining the unique SERS substrates with a
handheld Raman system, it can become a practical and portable sensor system for field applications. All these
developments have demonstrated that AgNR SERS substrates could play an important role in the future for practical
clinical, industrial, defense, and security sensing applications.
