The Use of Aligned Silver Nanorod Arrays Prepared by Oblique Angle Deposition as Surface Enhanced Raman Scattering Substrates

Abstract

Aligned Ag nanorod arrays have been fabricated on glass substrates using an oblique angle vapor deposition (OAD) method. The surface morphology and structure of the Ag rods were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Individual nanorods were found to be primarily cylindrical, albeit with irregularly shaped surface protrusions of the rods. The surface enhanced Raman scattering (SERS) response as a function of nanorod length was investigated using trans-1,2-bis(4-pyridyl)ethene as a probe molecule at an excitation wavelength of 785 nm. The enhancement factors reached a maximum of ∼5 × 108 as the nanorod length approached 868 nm and then decreased to ∼3 × 106 as the nanorod length increased further to 1900 nm. For the 868 nm nanorod array, signals collected over multiple spots within the same substrate resulted in a relative standard deviation (RSD) of 10%, while an RSD of 15% was measured in signals collected from different substrates. When stored in a food vacuum bag, the substrates are stable with respect to SERS intensity for greater than 2 months. This study demonstrates that the OAD Ag nanorod arrays are highly sensitive, uniform, and stable SERS substrates that are suitable for a variety of surface chemical analysis applications.