Metal nanoparticle catalyzed charge rearrangement in selenourea probed by surface-enhanced Raman scattering

Abstract

The adsorption behavior of selenourea (SeU) on Ag and Au nanoparticles was investigated using the surface-enhanced Raman scattering technique in combination with X-ray photoelectron spectroscopy and density functional theoretical calculations.

Colloidal and Deposited Products of the Interaction of Tetrachloroauric Acid with Hydrogen Selenide and Hydrogen Sulfide in Aqueous Solutions

“…The lines widened and slightly shifted if the mixture of H 2 Se and H 2 S was used, suggesting further disordering of gold chalcogenide phase. The Se-Se stretching that is expected to be around 290-330 cm −1 [59] was not detected. The spectrum from the products of the reaction HAuCl 4 + 3H 2 S showed a broad band near 490 nm that is due to S-S stretching frequencies, probably from S adsorbed at Au NPs, while Au-S stretches near 270 cm −1 [55,59] are absent.…”

“…The Se-Se stretching that is expected to be around 290-330 cm −1 [59] was not detected. The spectrum from the products of the reaction HAuCl 4 + 3H 2 S showed a broad band near 490 nm that is due to S-S stretching frequencies, probably from S adsorbed at Au NPs, while Au-S stretches near 270 cm −1 [55,59] are absent. This agrees with previous findings of a range of Au-S and S-S vibrations at lower concentrations of sulfide when metallic nanogold formed, and disappearance of the bands at the molar ratio 1-to-3 [55].…”

“…These values should be higher in AuSe and AuSe1−xSx compounds where silver is absent, so we assign the component at 85.4 eV and the Se 3d The Se 3d spectra, which are partially overlapped with Au 5p 3/2 bands, can be fitted using two doublets at 54.9 eV (more intense) and 54.1 ± 0.1 eV, with the relative intensity of the weaker low-energy component decreased and its position slightly shifted to lower BEs with increasing share of H 2 S in the reaction media. For comparison, the Se 3d spectrum of a commercial powder of elemental Se was fitted using two doublets with the Se 3d 5/2 peaks at 54.7 eV and 55.3 eV and 55.3 eV, which may be assigned to mono-and polymeric Se 0 species [59].…”

“…The assignment of the Au 4f components is not straightforward, particularly, since AuSe contains two sorts of Au atoms, the oxidation state of which is a matter of dispute [35][36][37][38][39][40][41][42][43][44][45]. The Au 4f 7/2 peaks at 84.0-84.4 eV reported for gold-gold selenide [39][40][41], gold-CdSe [44,45]), adlayers of Se or alkyl selenides at Au [45][46][47][48][49]59], etc., originate from Au 0 surfaces but not AuSe phases. In nanostructured AuSe with admixture of Au [42], the values of 83.7 eV and 84.9 eV have been found, along with Se 3d 5/2 line at 54.5 eV, and ascribed to Au 0 and Au + , respectively; nevertheless, the authors assert the mixed valence state of gold (Au + Au 3+ Se 2 ).…”

Surface selective binding of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on silver and gold nanoparticles: a Raman and DFT study

“…the binding sites and the orientation of the adsorbates on the metal surfaces. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] SERS has also been exploited recently for studying surface-catalyzed oxidation 23,24 and charge rearrangement reactions 25 . Noble-metal NPs are ideal candidates for studying such interactions.…”