Exploring the Effect of Intermolecular H-Bonding: A Study on Charge-Transfer Contribution to Surface-Enhanced Raman Scattering of p-Mercaptobenzoic Acid

Abstract

We report the significant effect of intermolecular hydrogen bonding (H-bonding) on surface-enhanced Raman scattering (SERS) spectra in which the vibrational frequencies and intensities of some characteristic peaks of p-mercaptobenzoic acid (MBA) change with varying concentrations of aniline. These changes can be attributed to modifications in the electronic structure of the MBA molecule and the conjugation of the system under the influence of H-bonding. Of remarkable note is that the nontotally symmetric (b 2 ) mode of MBA is dramatically enhanced, which can be considered as a manifestation of the charge-transfer (CT) transition process in the system. By comparing SERS spectra obtained under normal and basic conditions, the effect caused by H-bonding can be further understood. These results manifest that the CT resonance between MBA and Ag NPs through Herzberg−Teller contributions can be promoted by H-bonding. The current work may, therefore, be instructive for studying the influence of H-bonding on the electronic structure of molecules in a system via SERS technique.

Charge-Transfer Effect on Surface-Enhanced Raman Scattering (SERS) in an Ordered Ag NPs/4-Mercaptobenzoic Acid/TiO2 System

“…Bands at 1000, 1023, and 1575 cm −1 , which are assigned to nontotally symmetric ν (CC), display a large increase in the intensity of the SERS spectrum. 33,34 It is worth noting that the intensity of the peak at 1365 cm −1 , ascribed to the COO − stretching mode, decreases after the introduction of TiO 2 , which is because the original COO − stretching mode is inhibited after the introduction of TiO 2 . Meanwhile, the band at 1706 cm −1 , ascribed to the CO stretching mode, increases after the introduction of TiO 2 .…”

“…These results agree with previous reports of the SERS spectra of MBA. 34 CT Mechanism of MBA in Charge Transfer Systems. When metal, organic molecules, and semiconductor contact each other, there will be charge redistribution around the interface within a reasonably short time.…”

Surface‐enhanced Raman scattering properties of Lewis acid–base complexes of p‐hydroxybenzoic and p‐mercaptobenzoic acids with CO2 in the presence of silver

“…Because these types of complex are able to form well‐organized interfacial intermolecular systems, Raman light‐scattering properties were also calculated for important Raman‐active bands of the complexes. The differential cross sections of depolarized Raman scattering observed at right angles to the incident beam are determined by the activities, whereas the depolarization ratios for both natural and plane‐polarized light are, respectively, given by where and Δα ' are the derivatives of the average and anisotropic dipole polarizabilities.…”

“…In this context, p ‐hydroxybenzoic acid (PHBA) and p ‐mercaptobenzoic acid (PMBA) are molecular probes of interest for the detection of surface plasmons, mainly because of their applicability to attain large SERS intensities involving silver and gold nanoparticles. Interestingly, the effect of intermolecular H‐bonding of PMBA in specific solutions has revealed charge‐transfer contributions to SERS. These interactions can be monitored due to changes in the vibrational frequencies and intensities of some characteristic peaks of the H‐bonded PMBA.…”

Surface enhanced hyper Raman scattering (SEHRS) and its applications

“…The flat orientation at neutral and basic pH was also evidenced by a higher intensity of bands from out-of-plane vibrations of the phenyl ring at 684 cm À1 and 710 cm À1 in both the SEHRS and SERS spectra. [106][107][108] Using SERS spectra of pMBA excited with 1064 nm by the same laser, quasisimultaneous one-photon and two-photon excited measurements of pH were demonstrated in one microspectroscopic setup that were more sensitive than one-photon SERS sensing with excitation in the visible range alone. 22 The possibility of sensitive pH measurements in the acidic and neutral pH ranges in small focal volumes enables a variety of applications for sensing in complex microstructured environments.…”