Surface enhanced raman spectra of methionine on a silver electrode

A290 Talat S. RAHMAN

*

Institut fur Grenzfltichenforschung und Vakuumphysik, D-5170 Jiilich, Fed. Rep. of Germany Received

21 July 1988; accepted

for publication

Kernforschungsanlage

30 November

Jiilich, Postfach 1913,

1988

This paper presents lattice dynamical calculations for the clean Ag(ll0) surface. Based on nearest neighbor interactions, central forces, and harmonic potentials, the dispersion of the --surface phonons and resonances along the T-X and r-Y directions in the two-dimensional Brillouin zone are calculated. The results are in good agreement with helium atom scattering data when surface stress terms are included and surface force constants are changed from their values in the bulk.

158

Surface

SURFACE ENHANCED RAMAN SPECTRA ON A SILVER ELECTRODE L. ABELLO,

F. GENET,

J.M. NIGRETTO

LIES Grenoble, URA 01213, Domaine Universitaire, 38402 Saint Martin d’H&es Cedex, France Received

26 May 1988; accepted

for publication

Science 215 (1989) 158-170 North-Holland, Amsterdam

OF METHIONINI

* and G. LUCAZEAU

BP 75,

19 December

1988

Surface enhanced Raman spectra (SERS) of L-methionine on a silver electrode and on a photochemically formed silver surface are presented. The molecule seems to be chemisorbed via S-Ag and likely N-Ag bonds, its spectrum being strongly modified in comparison with the free solution. The enhancement is maximum when using the 647.1 nm exiting line, with laser illumination during the oxidation/reduction cycle (ORC) and for a single ORC. In addition, SERS of amorphous surface carbon is observed when using the 488.0 nm line. Considering the concentration dependence of the Raman intensity, the adsorption free enthalpy has been estiMoreover from independent electrochemical and mated to be equal to about -4.75 kcal/mol. SERS measurements it is found that the surface density of reduced silver atoms and of methionine molecules is of the order of 1 A-*.

171

Surface Science 215 (1989) 171-189 North-Holland, Amsterdam

STM-SEM COMBINATION STUDY ON THE ELECTROCHEMICAL GROWTH MECHANISM AND STRUCTURE OF GOLD OVERLAYERS A quantitative approach to electrochemical metal surface roughening L. VAZQUEZ,

A. BARTOLOME,

Departamento de Fisica de la Materia 28049 Madrid Spain

Condensada,

C. ALONSO, R.C. SALVAREZZA Departamento

and

A.M. BAR0 Universidad Autonoma

de Madrid,

*

de Quimica, Universidad Autonoma

de Madrid

28049 Madrid

Spain