We report on a high-resolution X-ray photoemission spectroscopy study on molecular-thick layers of L-cysteine deposited under ultrahigh vacuum conditions on Au(110). The analysis of core level shifts allowed us to distinguish unambiguously the states of the first-layer molecules from those of molecules belonging to the second layer. The first-layer molecules strongly interact with the metal through their sulfur headgroup. The multipeaked structure of the N 1s, O 1s, and C 1s core levels is interpreted in terms of different molecular moieties. The neutral acidic fraction (HSCH2CH(NH2)COOH) is abundant at low coverage likely associated with isolated molecules or dimers. The zwitterionic phase (HSCH2CH(NH3+)COO-) is largely dominant as the coverage approaches the monolayer limit and is related to the formation of ordered self-assembled molecular structures indicated by electron diffraction patterns. The occurrence of a small amount of cationic molecules (HSCH2CH(NH3+)COOH) is also discussed. The second-layer molecules mainly display zwitterionic character and are weakly adsorbed. Mild annealing up to 100 degrees C leads to the desorption of the second-layer molecules leaving electronic states of the first layer unaltered.

Small aluminum nanoparticles have the potential to exhibit localized surface plasmon resonances in the deep ultraviolet region of the electromagnetic spectrum, however technical and scientific challenges make it difficult to attain this limit. We report the fabrication of arrays of Al/Al2O3 core/shell nanoparticles with a metallic-core diameter between 12 and 25 nm that display sharp plasmonic resonances at very high energies, up to 5.8 eV (down to λ = 215 nm). The arrays were fabricated by means of a straightforward self-organization approach. The experimental spectra were compared with theoretical calculations that allow the correlation of each feature to the corresponding plasmon modes.

We have investigated the optical response of thiolate self-assembled monolayers (SAMs) deposited from the liquid phase on well characterized, (111)-textured gold films based on the use of in situ and ex situ optical spectroscopic ellipsometry. We considered SAMs formed by several molecules with thiol functionality, focusing on the octadecanethiol (C 18 ) SAM model system. We were able to show the tiny spectroscopic variations induced by the monolayer thick films with great reproducibility and high signal-to-noise ratio. We identified spectral features related to the alkyl chain and to the S-Au interface, providing a reliable spectral "fingerprint" of the formation of densely packed thiolate layers. By comparing data with simulations based on several effective models developed within the framework of Fresnel approach, we identified the main optical features related to the thiolate interface and in particular an absorption band whose spectral weight increases regularly from 500 nm toward the IR limit. We also obtained reliable estimations of the SAM thickness. The interface absorption properties have been tentatively assigned to a modification of the nearly free electron behavior, related to nanoscale morphological modifications following the formation of Au-thiolate moieties.

We have investigated the vibrational spectrum of hydrogen and deuterium atoms adsorbed on the (0001) surface of a graphite single crystal by means of atomic beam scattering in UHV conditions. Bound state resonances, which appear as minima in the specularly reflected beam have been detected over a wide range of incidence and azimuthal angles. Energy levels at 31.6±0.2 and 15.3±0.3 meV for 1H and at 35.4 ±2; 21.35±0.1; 12.0±0.1, and 5.9±0.3 meV for 2H have been determined. By fitting the experimental energy levels to those calculated with the potential the following values of the parameters are obtained: D=43.3±0.5 meV; λ=1.36±0.03 Å−1; p=4.4±0.6. The hypothesis that the interaction potential is the sum over all crystal layers of an atom–single layer potential V*(z) is used. V*(z) has a well depth D*=39.2±0.5 meV and a long range behavior given by C*4/z4 with C*4=5.2±0.3 eV Å4.