Enhanced Raman spectroscopic study of the adsorption of thiocarbohydrazide on silver and copper electrode surfaces

Loo, B. H.; Leahey, J.; Lee, Y.G.

doi:10.1016/0009-2614(90)87212-a

Cited by 6 publications

(5 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, under low-coverage conditions, adsorption with the molecular plane parallel to the surface is the most stable configuration in vacuum, whereas adsorption via the sulfur atom has the lowest binding energy. These results seem to contradict the spectroscopic data of TU adsorption in solution, − which indicate that TU adsorbs via the sulfur atom. Clearly, the solvent and the electric field at the interphase must play an important role in determining the adsorption geometry of thiourea.…”

Section: Resultsmentioning

confidence: 79%

“…Therefore, under lowcoverage conditions, adsorption with the molecular plane parallel to the surface is the most stable configuration in vacuum, whereas adsorption via the sulfur atom has the lowest binding energy. These results seem to contradict the spectroscopic data of TU adsorption in solution, [17][18][19][20][21][22][23][24][25][26][27][28][29][30] which indicate that TU 42,44 The inset shows only the first layer of metal atoms. MP2/DZP(adsorbate)+DZ-Huzinaga ECP (metal) calculations.…”

Section: Resultsmentioning

confidence: 95%

“…The increase of nearly 0.2 Å in the C-S bond length upon adsorption explains the substantial downshift in the frequencies of vibrational modes having a predominant contribution from C-S stretching reported in the literature. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] However, as pointed out in the previous section, for molecularly adsorbed TU either with an upright (Figure 3a) or a flat configuration (Figure 4b), the S-C bond length increased only 0.02 Å, indicating that the interaction with the surface has virtually no influence on the bond strength. Therefore, we conclude that the considerable downshift of the C-S stretching modes is the consequence of chemical bonding of TU in its canonical form.…”

Section: Resultsmentioning

confidence: 99%

“…Several conclusions may be drawn from the results of previous sections concerning the nature of the adsorbed species: (1) of all of the species considered, the strongest bonding to the surface occurs for the canonical TU radical suggesting that this should be most stable adsorbate; (2) the surface bonding of this radical has no major differences with that of the methanethiol radical supporting the XPS experimental evidence in this direction; 31 and (3) the enlargement of the SC bond upon adsorption for molecular TU is negligible, whereas for the canonical TU radical, this bond considerably increases, indicating a weakening of the bond strength compatible with the SC frequency downshift observed experimentally. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] Therefore, the general conclusion is that TU interconverts upon adsorption into a canonical TU radical that bears a negative charge, giving rise to a thioureate anion, which has the same surface bonding as that of alkanethiols.…”

Section: Microsolvation Of Thioureamentioning

confidence: 99%

“…Surface-enhanced Raman spectroscopy has been extensively used to study the adsorption of thiourea and several isostructural compounds such as thioamide, thiohydrazide, and thiocarbohydrazide on silver and copper surfaces. − In most cases, it was found that these molecules are bonded via the sulfur atom to Ag and Cu surfaces. The substantial downshift in the frequencies of vibrational modes having a predominant contribution from CS stretching suggested considerable electronic interactions between these molecules and metal surfaces.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Quantum Mechanical Investigation of Thiourea Adsorption on Ag(111) Considering Electric Field and Solvent Effects

2004

View full text Add to dashboard Cite

The adsorption of different thiourea species was investigated on the 111 surface of silver considering electric field and solvent effects with the objective of (a) elucidating the nature of the adsorbed species, mainly in an electrochemical environment, and (b) understanding the energetics and mechanisms of the surface reactions, particularly the oxidative adsorption of thiourea. We first considered the adsorption in vacuum of molecular species such as thiourea (TU), canonical thiourea, and formamidine disulfide as well as the adsorption of the canonical thiourea radical resulting from the cleavage of the S−H bond. The molecular adsorption of TU in vacuum has the highest binding energy (−33.2 kcal/mol) when the molecular plane is parallel to the surface. However, the strongest surface bond was observed for the canonical thiourea radical (−42.2 kcal/mol) whose nature is the same as that of the methanethiol radical. Externally applied electric fields perpendicular to the surface have an important effect on the orientation and surface bonding of thiourea, leading to an upright configuration of the molecule and to a strengthening of the sulfur−surface bond. Solvent effects were first considered to investigate the equilibria of thiourea in solution with the purpose of elucidating the nature of the predominant species which, in turn, constitutes the initial adsorbate on the surface. In neutral and basic pHs, the thiourea molecule is the predominant species, whereas in acidic electrolytes, the thiouronium ion readily forms. The microsolvation of thiourea with up to 16 water molecules was investigated to determine the structure of the hydration shell and the interaction energy between TU and water molecules. Water molecules form a compact cage around thiourea characterized by linked tetramer and pentamer structures. The NH2 groups form hydrogen bonds with water molecules, whereas the sulfur atom is poorly hydrated. The implications of the structure of water around thiourea on the adsorption geometry of the molecule are discussed. The oxidative adsorption mechanism of thiourea resulting in chemisorbed canonical thiourea was investigated considering charge-transfer processes, solvent effects, and the presence of a counterion.

show abstract

Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Microsolvation Of Thioureamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Quantum Mechanical Investigation of Thiourea Adsorption on Ag(111) Considering Electric Field and Solvent Effects

2004

View full text Add to dashboard Cite

show abstract

Ft‐SERS studies on 1,3‐thiazolidine‐2‐thione, 2,5‐dimercapto‐1,3,4‐thiadiazole and 2‐thiouracil adsorbed on chemically deposited silver films

Joy

Srinivasan

2001

J Raman Spectroscopy

View full text Add to dashboard Cite

Adsorption of 1,3-thiazolidine-2-thione (ttz), 2,5-dimercapto-1,3,4-thiadiazole (dmtd) and 2-thiouracil on a silver surface was studied by the FT-SERS technique. The FT-SERS spectra of all these molecules indicate dissociative adsorption on the silver surface to the corresponding thiolate ion. For ttz and 2-thiouracil, the corresponding thiolate ions are found to adsorb to the surface through their sulfur atoms and have a perpendicular orientation on the silver surface. For dmtd, the results suggest that the dithiolate ion has two kinds of adsorption geometries depending on the concentration of the dmtd in solution. At low concentration the diothiolate ion probably adsorbs through the nitrogen atom whereas at high concentration the ion probably adsorbs through its p-system

show abstract

The bonding of acrylonitrile molecules to copper surfaces

Loo

Kato

1993

Surface Science

View full text Add to dashboard Cite

Enhanced Raman spectroscopic study of the adsorption of thiocarbohydrazide on silver and copper electrode surfaces

Cited by 6 publications

References 28 publications

Quantum Mechanical Investigation of Thiourea Adsorption on Ag(111) Considering Electric Field and Solvent Effects

Quantum Mechanical Investigation of Thiourea Adsorption on Ag(111) Considering Electric Field and Solvent Effects

Ft‐SERS studies on 1,3‐thiazolidine‐2‐thione, 2,5‐dimercapto‐1,3,4‐thiadiazole and 2‐thiouracil adsorbed on chemically deposited silver films

The bonding of acrylonitrile molecules to copper surfaces

Contact Info

Product

Resources

About