A. Climent-Font

Bonding and hardness in nonhydrogenated carbon films with moderate sp3 content

Amorphous carbon films with an sp3 content up to 25% and a negligible amount of hydrogen have been grown by evaporation of graphite with concurrent Ar+ ion bombardment. The sp3 content is maximized for Ar+ energies between 200 and 300 eV following a subplantation mechanism. Higher ion energies deteriorate the film due to sputtering and heating processes. The hardness of the films increases in the optimal assisting range from 8 to 18 GPa, and is explained by crosslinking of graphitic planes through sp3 connecting sites.

RBS characterization of porous silicon multilayer interference filters

Porous silicon (PS) has great potential in optical applications due to its tunable refractive index. In particular, multilayer structures consisting of alternating PS layers with different refractive indexes can be used as interference filters for applications in optoelectronics. In the present work, Rutherford backscattering spectroscopy (RBS) measurements and optical characterization have been carried out on PS multilayer stacks consisting of alternate low-porosity/high-porosity layers to determine their compositional profile, homogeneity, and overall optical behavior. In addition, RBS has been used for the first time to determine the porosity profile of this kind of structures. The experimental results show a constant indepth composition among alternate layers, revealing the good homogeneity of the multilayer structures. Neither porosity nor oxidation degree gradient were observed.

Composition, nanostructure, and optical properties of silver and silver-copper lusters

Lusters are composite thin layers of coinage metal nanoparticles in glass displaying peculiar optical properties and obtained by a process involving ionic exchange, diffusion, and crystallization. In particular, the origin of the high reflectance (golden-shine) shown by those layers has been subject of some discussion. It has been attributed to either the presence of larger particles, thinner multiple layers or higher volume fraction of nanoparticles. The object of this paper is to clarify this for which a set of laboratory designed lusters are analysed by Rutherford backscattering spectroscopy, transmission electron microscopy, x-ray diffraction, and ultraviolet-visible spectroscopy. Model calculations and numerical simulations using the finite difference time domain method were also performed to evaluate the optical properties. Finally, the correlation between synthesis conditions, nanostructure, and optical properties is obtained for these materials.

Characterization of metal threads using differential PIXE analysis

Abstract The external differential-PIXE technique is presented in this work as an efficient and non-destructive tool for the characterization of the structure of ancient metal threads. A PIXE analysis for different proton energies has been performed in a selection of gold and silver threads belonging to the Collection of Textiles of La Alhambra (19th century) and to the Medieval Collection of Textiles of the National Archaeological Museum of Spain. The threads are made of metal strips, wound around a silk or cotton core. The use of differential PIXE allows to distinguish strips made of homogeneous alloys from those made of a silver and copper alloy, coated with a thin gold layer. In the same analysis it is also possible to detect the presence or absence of some trace elements of archaeological interest, such as Pb or Hg.

Engineering of silicon surfaces at the micro- and nanoscales for cell adhesion and migration control

The engineering of surface patterns is a powerful tool for analyzing cellular communication factors involved in the processes of adhesion, migration, and expansion, which can have a notable impact on therapeutic applications including tissue engineering. In this regard, the main objective of this research was to fabricate patterned and textured surfaces at micron- and nanoscale levels, respectively, with very different chemical and topographic characteristics to control cell–substrate interactions. For this task, one-dimensional (1-D) and two-dimensional (2-D) patterns combining silicon and nanostructured porous silicon were engineered by ion beam irradiation and subsequent electrochemical etch. The experimental results show that under the influence of chemical and morphological stimuli, human mesenchymal stem cells polarize and move directionally toward or away from the particular stimulus. Furthermore, a computational model was developed aiming at understanding cell behavior by reproducing the surface distribution and migration of human mesenchymal stem cells observed experimentally.

Long Term Atmospheric Pollution Study at Madrid City (Spain)

Gases and suspended particulate matter are sampled and measured in situ at different sites within the city of Madrid to determinethe air pollution in the city. Lead concentrations in air are also determined. The information needed to assess levels of contaminants is obtained combining several analytical techniques,which provide real time concentration data of particles andgases. Particulate matter (PM), SO2, CO, O3, NOx,NO2, CH4, total hydrocarbons and Pb were measured. Concentrations of pollutants are averaged over periods of hours,days, months and years. Variations of contaminant concentrationsin the last years are presented. Spatial and temporal distribution follows that of the traffic, the main source of pollution in Madrid City. Some specific measurements were carriedout to understand the influence of traffic emissions at themeasured site. Further, all measured concentrations never exceeded the European Union Directives.

Characterisation of archaeological bronzes using PIXE, PIGE, RBS and AES spectrometries

Abstract A reliable knowledge of the composition of archaeological bronzes for major and trace elements is of primary interest for the archaeologist. The composition of the metal artefacts gives information on the ancient technological knowledge and may help to distinguish between prehistoric cultural traditions. Pieces of bronzes from two pre-roman sites in Spain with different cultural traits have been analysed by ion beam analytical techniques (PIXE, PIGE and RBS) and Auger electron spectroscopy (AES). Joint use of these techniques has been found to be useful as they give complementary information on elemental composition and chemical state. The possible disturbance of the patina as a mask for the determination of the original underlying bronze composition has also been studied.

Nanostructured porous silicon micropatterns as a tool for substrate-conditioned cell research

The localized irradiation of Si allows a precise patterning at the microscale of nanostructured materials such as porous silicon (PS). PS patterns with precisely defined geometries can be fabricated using ion stopping masks. The nanoscale textured micropatterns were used to explore their influence as microenvironments for human mesenchymal stem cells (hMSCs). In fact, the change of photoluminescence emission from PS upon aging in physiological solution suggests the intense formation of silanol surface groups, which may play a relevant role in ulterior cell adhesion. The experimental results show that hMSCs are sensitive to the surface micropatterns. In this regard, preliminary β-catenin labeling studies reveal the formation of cell to cell interaction structures, while microtubule orientation is strongly influenced by the selective adhesion conditions. Relevantly, Ki-67 assays support a proliferative state of hMSCs on such nanostructured micropatterns comparable to that of standard cell culture platforms, which reinforce the candidature of porous silicon micropatterns to become a conditioning structure for in vitro culture of HMSCs.

Metallic and nonmetallic shine in luster: An elastic ion backscattering study

Luster is a metal glass nanocomposite layer first produced in the Middle East in early Islamic times (9th AD) made of metal copper or silver nanoparticles embedded in a silica-based glassy matrix. These nanoparticles are produced by ion exchange between Cu+ and Ag+ and alkaline ions from the glassy matrix and further growth in a reducing atmosphere. The most striking property of luster is its capability of reflecting light like a continuous metal layer and it was unexpectedly found to be linked to one single production parameter: the presence of lead in the glassy matrix composition. The purpose of this article is to describe the characteristics and differences of the nanoparticle layers developed on lead rich and lead free glasses. Copper luster layers obtained using the ancient recipes and methods are analyzed by means of elastic ion backscattering spectroscopy associated with other analytical techniques. The depth profile of the different elements is determined, showing that the luster layer formed in ...

Optical and In-Depth RBS Characterization of Porous Silicon Interference Filters

In the present work, Rutherford backscattering spectroscopy (RBS) measurements, scanning electron microscopy, and optical characterization are carried out on porous silicon (PS) multilayer interference filters in order todetermine their compositional profile, homogeneity, and overall optical behavior. In addition, RBS measurements allow determination of the porosity profile of multilayer structures. Thus, both porosity and oxidation degree are determined for each individual layer forming the stack, giving a straightforward measure of the in-depth homogeneity of these structures. Finally, the aging effects on the optical behavior and compositional profile of the PS stacks are studied by comparing as-prepared and aged multilayers. The results reveal good in-depth homogeneity of the PS multilayers and an oxygen enrichment with ambient air exposure, which results in a lowering of the effective refractive index and a blueshift of the reflectance spectra of the filters.