Detection of overtone and combined peaks using Mn/Cu helical star-shaped (pine-tree-like) sculptured thin films in surface-enhanced Raman spectroscopy

AbstractMn helical star-shaped (pine-tree-like) nano-sculptured thin films with three-, four-and fivefold symmetry on copper substrates were produced using oblique angle deposition method in conjunction with rotation of sample holder at certain angles. Raman spectroscopy of the samples which were subjected to impregnation by ۴,۴′-bipyridine (C۱۰H۸N۲) solution was carried out by ۶۳۲.۸ nm wavelength laser. The analysis of the Raman spectra showed enhancement for the ۴,۴′-bipyridine main bands (۱۵۹۲ and ۱۲۹۷ cm−۱) belonging to the C=C stretching mode, aromatic ring stretching ring and in-plane ring mode of ۴,۴′-bipyridine, same as results obtained for Ag nano-structures. In addition, overtone and combined peaks are detected that may be related to the particular sculptured structure of the thin films fabricated in this work and the laser wavelength used for Raman spectroscopy. UV–Vis (absorption mode) spectra showed consistent observations with the SERS results leading to important role of surface electromagnetic selection rule in intensification of SERS, in addition pointing out the importance of the effect of the size of hot spots on the frequency of the localized surface plasmonic oscillations.

Keywords:

Mn helical star shape (pine , Tree , like) , Sculptured thin films , Surface , enhanced Raman spectroscopy , ۴ , ۴′ , Bipyridine , Surface plasmonic oscillations