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

Abstract

Mn 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 4,4′-bipyridine (C 10 H 8 N 2) solution was carried out by 632.8 nm wavelength laser. The analysis of the Raman spectra showed enhancement for the 4,4′-bipyridine main bands (1592 and 1297 cm −1) belonging to the C=C stretching mode, aromatic ring stretching ring and in-plane ring mode of 4,4′-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.

Observation of High-Order Overtones and Combinations in Surface-Enhanced Raman Scattering: The Essential Role in Elucidation of the Chemical Mechanism

“…The demand for contemporary SERS measurements in the range of higher wavenumbers is conditioned by the limit of recent observations of overtones for the second order. 13,14 The overtones of higher orders have been recorded only for inorganic species consisting of heavy elements. 15−17 For these compounds, they are affected by localized surface plasmon resonance due to small Raman shifts 18 and cannot be considered as true signs of the chemical contribution.…”

“…The demand for contemporary SERS measurements in the range of higher wavenumbers is conditioned by the limit of recent observations of overtones for the second order. , The overtones of higher orders have been recorded only for inorganic species consisting of heavy elements. − For these compounds, they are affected by localized surface plasmon resonance due to small Raman shifts and cannot be considered as true signs of the chemical contribution. A coordinated theoretical and experimental study of intensive high-order modes may be helpful to validate the necessity of including the higher-order Albrecht terms and can give an insight into the anharmonicity and the excited-state dynamics.…”

Microfluidic SERS devices: brightening the future of bioanalysis

“…Between the RR and the recognition biomolecule, a biocompatible shell can be inserted to keep the RR near the NP, to maximise SERS signal enhancement and stabilise the NPs. Each one of the components can be chosen from a large number of options, depending on the desired application: (i) the type of NP, (normally Au and Ag but other examples report the use of Cu/Mn [ 71 ], ZnO [ 72 ], W 18 O 49 nanocrystals [ 73 ], MoO 2 [ 74 ] , graphene/MoS 2 nanohybrids [ 75 ] etc.) as well as its size and shape (nanorods and nanostars being preferred to spheres [ 34 ]); (ii) number of NPs: single versus clusters (assembly of NPs offers gaps which are a source of hotspots for increased signal); (iii) the type of RR ( e.g.…”