In the mid-1970s, surface-enhanced Raman scattering (SERS) was discovered which impacted on surface science and spectroscopy because of its extremely high surface sensitivity. However, SERS had not developed as many people had hoped to be a powerful surface diagnostic technique that can be widely used because of some obstacles. For example, only three noble metals Au, Ag, and Cu could provide large enhancement, severely limiting the widespread applications involving other metallic materials of both fundamental and practical importance. In this article, emphasis is put on the recent work of our group to directly generate SERS on net transition metals (e.g., Pt, Ru, Rh, Pd, Fe, Co, Ni, and their alloys) by developing various roughening procedures and optimizing the performance of the confocal Raman microscope. An approach of replacing the randomly roughened surface with ordered nanorod arrays of transition metals is introduced as a promising class of highly SERS-active substrates. The surface enhancement fa...

Surface-Enhanced Raman Scattering: From Noble to Transition Metals and from Rough Surfaces to Ordered Nanostructures

Interaction of hydrogen with solid surfaces

http://w0.rz-berlin.mpg.de/hjfdb/pdf/260e.pdf

Metal deposits on well-ordered oxide films

Surface infrared spectroscopy

/pdf/surface-chemistry-of-catalysis-by-gold-37hj5cal3q.pdf

Surface chemistry of catalysis by gold

Vibrational spectroscopy has indicated that the ordered overlayers formed by CO on metal surfaces at high coverage are not “compression” structures, or “floating” phases, but rather coincident site lattices in which the molecules remain adsorbed on high symmetry sites. In an equivalent description such layers may be regarded as a mixture of phase and anti-phase domains of a lower coverage structure separated by regularly spaced domain walls (solitons), at which the local CO density is higher. Due to the flat potential energy surface the molecules at the domain walls can adjust to the repulsive CO-CO interaction by moving off the high symmetry sites. The soliton model has the advantage of providing a convenient description of the formation of such phases and of the transitions from one phase to another. In the present paper low energy electron diffraction (LEED) and infrared spectroscopy are used to illustrate these phenomena in the adsorption systems Pt{111}-CO and Pd{111}-CO.

Understanding the structure of high coverage CO adlayers

The adsorption of hydrogen and deuterium has been studied with high resolution electron energy loss spectroscopy (HREELS). At maximum coverage at 105 K the H adlayer exhibits two dominant loss features at 102 (ν1) and 141 (ν2) meV which show pronounced intensity variations as a function of the primary electron energy (maximum between 5 and 6 eV). The hydrogen is assigned to the threefold coordinated site of the Ru (001) surface leading to a C3v symmetry of the adsorption complex. The angular dependence of both loss peaks shows only a smooth intensity decrease in off‐specular directions thus preventing the separation of dipole and impact scattering contributions. Three additional loss peaks with considerably lower intensities are identified with overtone and combination excitations. The anharmonicity coefficients derived from the respective energies are used to fit a two‐dimensional potential function for the hydrogen atom located in a plane perpendicular to the surface with first order perturbation theory...

Adsorption of hydrogen and deuterium on Ru(001)

The oxidation states formed during low-temperature oxidation (T < 500 K) of a Ru(0001) surface are identified with photoelectron spectromicroscopy and thermal desorption (TD) spectroscopy. Adsorption and consecutive incorporation of oxygen are studied following the distinct chemical shifts of the Ru 3d5/2 core levels of the two topmost Ru layers. The evolution of the Ru 3d5/2 spectra with oxygen exposure at 475 K and the corresponding O2 desorption spectra reveal that about 2 ML of oxygen incorporate into the subsurface region, residing between the first and second Ru layer. Our results suggest that the subsurface oxygen binds to the first and second layer Ru atoms, yielding a metastable surface “oxide”, which represents the oxidation state of an atomically well ordered Ru(0001) surface under low-temperature oxidation conditions. Accumulation of more than 3 ML of oxygen is possible via defect-promoted penetration below the second layer when the initial Ru(0001) surface is disordered. Despite its higher ca...

Horst Conrad

Papers

Understanding the structure of high coverage CO adlayers

Adsorption of hydrogen and deuterium on Ru(001)

Identification of Subsurface Oxygen Species Created during Oxidation of Ru(0001)

A comparison of single-, double-, triple-bonded and aromatic CN compounds on Pd(111) and (100) I. Hreels of NCCN, ethylenediamine and s-triazine

High resolution electron energy loss investigations of the adsorption of NO on the clean and oxygen precovered Ru(001) surface