Surface anchoring mode‐dependent hydrolysis reactions of hydrazone groups on gold examined by pH‐dependent Raman spectroscopy

Abstract

We conducted a comparative study of the pH‐dependent anchoring behaviors of 3‐methyl‐2‐benzothiazolinone hydrazone (3M2BH) and benzophenone hydrazone (BPH) on gold nanoparticles (AuNPs) by means of interfacial Raman spectroscopy. We found that several bands of 3M2BH in the highly alkaline pH region disappeared as the colloidal conditions became more neutral and acidic. The vibrational band at 919, 1174, and 1222 cm−1 at pH 10.0 disappeared below pH 9.2, which may be because of the hydrolysis reactions that cleave the labile N―NH2 group of 3M2BH, indicating a rather perpendicular orientation via the sulfur atom at the surfaces. A fairly high transition pH value was assumed to be because of the interaction of the N―NH2 group in the vicinity of the surfaces. Several characteristic bands, including 1584 and 1617 cm−1, also exhibited different intensities, suggesting that the adsorbates on Au surfaces underwent structural transformations of the N―NH2 group after the pH value became neutral or acidic. These changes were not observed for BPH, presumably because of the direct and robust binding of the hydrazone onto Au surfaces. Our results revealed that the pH‐dependent cleavage reactions may vary depending on the surface anchoring modes of the adsorbates. Copyright © 2015 John Wiley & Sons, Ltd.

Detection of Copper(II) Ions Using Glycine on Hydrazine-Adsorbed Gold Nanoparticles via Raman Spectroscopy

“…The SERS spectrum of GLY appeared to be relatively weak with its amino group interacting with Au surfaces. In the SERS spectrum of hydrazine on AuNPs, we could not observe a strong hydrazone linkage-related N-N stretching mode at 919 cm − 1 or N-H bending modes at 1174 and 1222 cm − 1 [34]. …”

The SERS effect in coordination chemistry

“…By investigating the SERS spectra of such species in aggregated gold nanoparticles, Gadogbe et al [232] concluded that the molecules are Ly and Joo [235] reported the SERS behavior of 3-methyl-2-benzothiazolinone hydrazone, and benzophenone hydrazone anchored on gold nanoparticles, showing the occurrence of hydrolysis of the =N-NH 2 group below pH 9.2.…”

Surface‐enhanced Raman scattering properties of Lewis acid–base complexes ofp‐hydroxybenzoic andp‐mercaptobenzoic acids with CO2in the presence of silver

“…Adsorption of organic thiols and carboxylic acids on metal colloids is an issue of great interest in surface science, which have been recently investigated by employing surface‐enhanced Raman scattering (SERS) . The high sensitivity of this technique yields a detailed information on the mechanism of the molecular adsorption, allowing, for example, to know which functional groups bind the metal surface .…”

“…Adsorption of organic thiols and carboxylic acids on metal colloids is an issue of great interest in surface science, which have been recently investigated by employing surface-enhanced Raman scattering (SERS). [1][2][3][4][5][6][7][8][9][10] The high sensitivity of this technique yields a detailed information on the mechanism of the molecular adsorption, allowing, for example, to know which functional groups bind the metal surface. [4] In this context, p-hydroxybenzoic acid (PHBA) and p-mercaptobenzoic acid (PMBA) are molecular probes of interest for the detection of surface plasmons, [5,10] mainly because of their applicability to attain large SERS intensities involving silver and gold nanoparticles.…”