Surface‐enhanced Raman scattering (SERS) of 4‐mercaptobenzoic acid on silver and gold substrates

Abstract

Surface-enhanced Raman scattering (SERS) spectra were recorded for p-mercaptobenzoic acid (PMBA) monolayers on Ag and Au surfaces. As evidenced by the relative intensities of the bands corresponding to the symmetric stretching COO − vibration and to the out-of-plane vibration of the phenyl ring, the molecules are at least tilted with respect to the surface and simultaneously bonded through the sulfur atom and COO − groups. This situation takes place when modification is carried out from aqueous solutions at natural or alkaline pH and at low concentrations of monomer. At higher concentration of the monomer (>10 −3 ) and/or at acidic pH, carboxylic groups are protonated and PMBA molecules adopt a more vertical configuration. It was also found that rough Ag and Au surfaces that are applied in SERS experiments promote partial decarboxylation of PMBA.

Effect of Ring Substitution Position on the Structural Conformation of Mercaptobenzoic Acid Self-Assembled Monolayers on Au(111)

“…The averaged tilt angles calculated for 3-and 4-MBA are within experimental error of one another and are in the range of [25][26][27][28][29][30] • from the surface normal. As such, the 3-and 4-substituted monomers have an upright, but not entirely vertical, configuration (figures 2(b) and (c)).…”

Effect of Foreign Molecules on the SERS of Probe Molecules Trapped in Gaps between Planar Ag and Nano-sized Ag Particles

“…However, the 4-MBA peaks were identifiable from the beginning when the thickness of P4VP was 2.2 nm (corresponding to the 0.05 wt % spin-cast solution); the SERS spectrum of 4-MBA is dominated by the strong bands at about 1587 cm −1 (8a, ring vibration) and 1077 cm −1 (12, ring vibration). 31 This can be seen more clearly in Figure 4(b), in which the Raman intensity of 4-MBA at 1587 cm −1 (denoted by an asterisk (*) in Figure 4(a)) is shown as a function of the flow time of 4-MBA. When the P4VP thickness was 2.2 nm, the Raman peaks of 4-MBA were saturated within 10 min.…”

Synthesis of magnetic core-branched Au shell nanostructures and their application in cancer-related miRNA detection via SERS

“…The experimental results indicate that the branched Au shell can be obtained by using the shape induction agent AgNO3, while smooth gold shells are prepared without AgNO3 despite feeding more gold precursor HAuCl4. teristic peaks of 4-MBA at 1080 and 1589 cm -1 which are assigned to ν8a and ν12 aromatic ring vibrations can be clearly observed from the three spectra [43]. By characterizing the SERS intensity of 4-MBA at 1080 cm -1 , the SERS enhancement generating from the B-GMNPs is approximated to 2.89 and 1.80 times relative to the signal from the S-GMNPs synthesized by ×1 and ×2 growth solution respectively (Fig.…”