Fundamental SERS Investigation of Pyridine and Its Derivates as a Function of Functional Groups, Their Substitution Position, and Their Interaction with Silver Nanoparticles

Abstract

The Raman and surface-enhanced Raman spectroscopy (SERS) spectra of pyridine, 2-, 3-, and 4pyridinemethanol and 2-, 3-, and 4-picolylamine were comprehensively studied using two different types of silver nanoparticles as SERS substrates, namely citrate-reduced and hydroxylamine-reduced silver nanoparticles, which are the most commonly used silver colloids. For a robust band assignment, Raman spectra of the investigated molecules were simulated, applying Møller−Plesset perturbation theory in conjunction with the 6 311++G(d, p) basis set. Subsequently, the observed changes in the spectra were interpreted and discussed in detail, taking into account the simulated Raman spectra. Furthermore, differences in the spectral information resulting from the two different analyzed functional groups, the altering of the substitution position and the molecular orientation relative to the metal surface were discussed, and general conclusions for an application of those molecules as Raman reporters were derived.

Molecular Specific and Sensitive Detection of Pyrazinamide and Its Metabolite Pyrazinoic Acid by Means of Surface Enhanced Raman Spectroscopy Employing In Situ Prepared Colloids

“…However, exploiting the plasmon-based surface enhancement effect, the presence of plasmonic NPs can significantly change the spectral profile of the SERS spectra as compared to the Raman spectra. This is associated with surface dependency effects, e.g., orientation to the surface (surface selection rules), gradient field effect and charge-transfer events, which results in variations of the spectral position and/or intensity of certain peaks [51,52]. In the SERS spectrum of PZA and POA (aqueous solution, concentration 10 −3 M, h-AgNP) measured with hydroxyl amine hydrochloride reduced batch silver nanoparticles h-AgNPs ( (Figure 1a,b) top panel) the three Raman modes characteristic for the fundamental vibrations of the pyrazine ring (1021 cm −1 , 1055 cm −1 and 1528 cm −1 ) are still clearly visible and unaffected by the proximity of the silver surface.…”

First Principles Calculations Toward Understanding SERS of 2,2′‐Bipyridyl Adsorbed on Au, Ag, and Au–Ag Nanoalloy

“…The 22BPY molecules can be in crevices and nano‐gaps of the rough surface. Recent study suggests that molecules in such sites can exhibit spectral shifts of Raman peaks . Since the surface of nanodiscs are not atomically flat and can have some nano‐features, we consider in the model a surface with some roughness.…”

SERS spectrum of imazalil. Experimental and quantum‐chemical vibrational analysis

“…The presence of SERS bands corresponding to both the in‐plane and out‐of‐plane vibration modes of the imidazole and benzene aromatic rings suggests that imidazol adopts a tilted orientation with respect to the metal surface . However, the possibility that the molecule is also adsorbed on the metallic surface with a flat orientation of the imidazole ring is not ruled out.…”

“…The presence of SERS bands corresponding to both the in-plane and out-of-plane vibration modes of the imidazole and benzene aromatic rings suggests that imidazol adopts a tilted orientation with respect to the metal surface. [41,42] However, the possibility that the molecule is also adsorbed on the metallic surface with a flat orientation of the imidazole ring is not ruled out. Figure 6 compares the SERS spectra, in the region of 1,700 to 600 cm −1 , of the aqueous solutions of imazalil (10 −5 M) as product for agricultural use and as pure substance.…”