Adsorption Geometry of Alizarin on Silver Nanoparticles: A Computational and Spectroscopic Study

Abstract

The knowledge of the adsorption geometry of an analyte on a metal substrate employed in surface enhanced Raman scattering (SERS) spectroscopy is important information for the correct interpretation of experimental data. The adsorption geometry of alizarin on silver nanoparticles was studied through ab initio calculations in the framework of density functional theory (DFT) by modeling alizarin taking into account all the different charged species present in solution as a function of pH. The calculations allowed a faithful reproduction of the measured SERS spectra and to elucidate the adsorption geometry of this dye on the silver substrate.

Is There an International Klein Pink?

“…Colorants 2023, 2, FOR PEER REVIEW et al determined that the pKs of alizarin are 5.25 and 11.5, which give rise to the mon ionic and dianionic species, respectively [22]. Considering that SERS analysis was under acidic pH with the introduction of HNO3 for hydrolysis, the resulting SERS s trum indicates the bonding of negatively charged, monoanionic anthraquinone to the itively charged silver nanoparticle clusters (Ag3) + [22,23]. This species was observed f the SERS spectra obtained with alizarin in this study.…”

“…However, in addition to deliberate layering, artists, including Klein, rework their paintings. Stitch notes instances of Klein repainting a pink work to make it yellow, a red Analysis of the lower pink layer with SERS (Figure 4) revealed the presence of two lake pigments, rhodamine 6G (C 28 H 31 N 2 O 3 Cl; Pigment Red 81) and a synthetic alizarin [23]. The reason for the addition of rhodamine 6G to synthetic alizarin is unknown, although lake pigments were often adulterated with additional synthetic pigments [24].…”