Jose Angel Martin Gago | CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council) (original) (raw)
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Papers by Jose Angel Martin Gago
Icarus, 2009
Two different simulation experiments of prebiotic synthesis were carried out in a CH4/N2/H2 atmos... more Two different simulation experiments of prebiotic synthesis were carried out in a CH4/N2/H2 atmosphere with spark discharge activation of aqueous aerosols and liquid water. In both cases, a hydrophilic tholin and a hydrophobic tholin were obtained. The methodology developed by our group for the characterisation of hydrophilic tholins [Ruiz-Bermejo, M., Menor-Salván, C., Mateo-Martí, E., Osuna-Esteban, S., Martín-Gago, J.A., Veintemillas-Verdaguer, S.,
The Interstellar Astrochemistry Chamber (ISAC) is mainly designed for the study of solids (ice ma... more The Interstellar Astrochemistry Chamber (ISAC) is mainly designed for the study of solids (ice mantles, organics, and silicates) in interstellar and circumstellar environments: characterization of their physico-chemical properties and their evolution due to vacuum-UV and/or cosmic ray irradiation, and thermal processing.
Vacuum, 2011
Synchrotron radiation ultra-violet photoemission at different photon energies (17.1, 19.3, and 21... more Synchrotron radiation ultra-violet photoemission at different photon energies (17.1, 19.3, and 21.5 eV) has been used to study the interaction of O 2 with the TiO 2 (110)e(1 Â 2) surface reconstruction at temperatures between 77 and 320 K. At 77 K the results show a weak molecular chemisorption of the O 2 molecule on the surface. By analysing the thermal behaviour of the O 2 /TiO 2 system in a temperature range from 77 to 320 K, it has been found that between 120 and 200 K the O 2 molecule is dissociated.
2009 Second International Conference in Visualisation, 2009
The arrangement of atoms at the surface of a solid accounts for many of its properties: hardness,... more The arrangement of atoms at the surface of a solid accounts for many of its properties: hardness, chemical activity, corrosion, etc. are dictated by the precise surface structure. Hence, finding it, has a broad range of technical and industrial applications. The ability to solve this problem opens the possibility of designing by computer materials with properties tailored to specific applications. Since the search space grows exponentially with the number of atoms, its solution cannot be achieved for arbitrarily large structures. Presently, a trial and error procedure is used: an expert proposes an structure as a candidate solution and tries a local optimization procedure on it. The solution relaxes to the local minimum in the attractor basin corresponding to the initial point, that might be the one corresponding to the global minimum or not. This procedure is very time consuming and, for reasonably sized surfaces, can take many iterations and much effort from the expert. Here we report on a visualization environment designed to steer this process in an attempt to solve bigger structures and reduce the time needed. The idea is to use an immersive environment to interact with the computation. It has immediate feedback to assess the quality of the proposed structure in order to let the expert explore the space of candidate solutions. The visualization environment is also able to communicate with the de facto local solver used for this problem. The user is then able to send trial structures to the local minimizer and track its progress as they approach the minimum. This allows for simultaneous testing of candidate structures. The system has also proved very useful as an educational tool for the field.
Surface Science, 2000
High-resolution synchrotron radiation photoemission has been used to investigate the formation of... more High-resolution synchrotron radiation photoemission has been used to investigate the formation of the Cu(110)+c(2×2)-Si surface alloy. The complex spectra of the Si 2p core-level are analyzed as multiple component spectra for different Si coverages and annealing temperatures of the surface alloy. The results show that c(2×2) islands are formed from the very beginning of the growth and that Si has a high diffusion length on Cu. The thermal stability of the surface alloy has been studied by measuring real-time photoemission spectra at different temperatures. The surface alloy is stable up to 180°C. Above this temperature disruption of the surface alloy and clustering of the Si atoms can be observed.
Surface Science, 2013
The electronic structure of the TiO 2 (110)-(1 × 2) surface has been studied by means of angular ... more The electronic structure of the TiO 2 (110)-(1 × 2) surface has been studied by means of angular resolved ultraviolet photoemission spectroscopy (ARUPS). The valence band dispersion along the high symmetry surface directions, [001] and [1-10], has been recorded. The experimental data show no dispersion of the band-gap Ti 3d states. However, the existence of dispersive bands along the [001] direction located at about 7 eV below the Fermi level is reported. The existence of two different contributions in the emission from the defects-related state located in the gap of the surface is univocally shown for the first time.
Nanotechnology, 2010
We present a combination of experimental STM images and DFT calculations to understand the atomic... more We present a combination of experimental STM images and DFT calculations to understand the atomic scale contrast of features found in high-resolution STM images. Simulating different plausible structural models for the tip, we have been able to reproduce various characteristics previously reported in experimental images on TiO 2 (110)-(1 × 1) under controlled UHV conditions. Our results allow us to determine the influence of different chemical and morphological tip terminations on the atomic-resolution STM images of the TiO 2 (110)-(1 × 1) surface. The commonest images have been properly explained using standard models for a W tip, either clean or with a single O atom located at the apex. Furthermore, a double transfer of oxygen atoms can account for different types of bizarre atomic-resolution features occasionally seen, and not conclusively interpreted before. Importantly, we discuss how typical point-defects are imaged on this surface by different tips, namely bridging O vacancies and adsorbed OH groups.
Journal of Physics: Condensed Matter, 2006
In the last two decades surface science techniques have decisively contributed to our present kno... more In the last two decades surface science techniques have decisively contributed to our present knowledge of alkanethiol self-assembled monolayers (SAMs) on solid surfaces. These organic layers have been a challenge for surface scientists, in particular because of the soft nature of the organic material (which can be easily damaged by irradiation), the large number of atoms present in the molecules, and the complex physical chemistry involved in the self-assembly process. This challenge has been motivated by the appealing technological applications of SAMs that cover many fields of the emerging area of nanotechnology. Sulfur (S) is closely related to alkanethiols and can be used to understand basic aspects of the surface structure of SAMs. In this review we focus on the atomic/molecular structures of S-containing SAMs on Au(111). Particular emphasis is given to the substrate, adsorption sites, chemical state of the S-metal bond and also to the experimental and theoretical tools used to study these structures at the atomic or molecular levels.
IEEE Transactions on Magnetics, 1998
... It is particularly interesting for that purpose to grow nanoparticulate thin films having lar... more ... It is particularly interesting for that purpose to grow nanoparticulate thin films having large magnetization and coercivity, since optimized values of both parameters allow us to take advantage of the reduced sue of the magnetic entities in order to ... [I]. JL Dormann, D. Fiorani and ...
Icarus, 2008
Please cite this article in press as: Ruiz-Bermejo, M., et al CH 4 /N 2 /H 2 spark hydrophilic th... more Please cite this article in press as: Ruiz-Bermejo, M., et al CH 4 /N 2 /H 2 spark hydrophilic tholins: A systematic approach to the characterization of tholins.
Current Nanoscience, 2006
ABSTRACT Nucleic acids are natural biopolymers that store the genetic information of organisms. T... more ABSTRACT Nucleic acids are natural biopolymers that store the genetic information of organisms. This makes the detection and characterization of DNA and RNA a relevant task in biotechnology, with applications ranging from medicine to environmental control. During the last decades, a large effort has been focused on the development of biosensors, among them those devoted to the detection of nucleic acids in natural samples and those that include nucleic acids as nanosized capture probes for different biomolecules. DNA microarray technology has been successfully used in biotechnological applications including genotyping and gene expression studies. Nevertheless, the performance of DNA microarrays has a limitation imposed by the need of a previous fluorescent labeling of the target molecule to be analyzed. This encouraged the use of alternative detection methods, such as optical and electrochemical ones, and recently others based on surface characterization techniques. New trends in nanotechnology point towards new tools for manipulating molecules and macromolecules that could be developed as high performance biosensors. This interdisciplinary approach towards the integration of novel biosensors can benefit from the capability of certain polymers to form self-assembled monolayers (SAMs) on different surfaces. Thiol-modified DNA can form SAMs on gold surfaces with reduced efficiency, and the biological activity of the probe is decreased upon adsorption. Therefore, thiolated DNA has a very limited use in biosensor development. These constraints have been successfully by-passed using uncharged, artificial analogs of natural nucleic acids, such as peptide nucleic acids (PNAs), as molecular probes. This contribution reviews the state of the art in the use of nucleic acids and their analogs as biosensor nanomaterials, and summarizes the novel approach towards the development of biosensors based on SAMs of PNAs. Finally, we present the current trends in this promising aspect of nanobiotechnology.
Applied Physics Letters, 1990
Icarus, 2009
Two different simulation experiments of prebiotic synthesis were carried out in a CH4/N2/H2 atmos... more Two different simulation experiments of prebiotic synthesis were carried out in a CH4/N2/H2 atmosphere with spark discharge activation of aqueous aerosols and liquid water. In both cases, a hydrophilic tholin and a hydrophobic tholin were obtained. The methodology developed by our group for the characterisation of hydrophilic tholins [Ruiz-Bermejo, M., Menor-Salván, C., Mateo-Martí, E., Osuna-Esteban, S., Martín-Gago, J.A., Veintemillas-Verdaguer, S.,
The Interstellar Astrochemistry Chamber (ISAC) is mainly designed for the study of solids (ice ma... more The Interstellar Astrochemistry Chamber (ISAC) is mainly designed for the study of solids (ice mantles, organics, and silicates) in interstellar and circumstellar environments: characterization of their physico-chemical properties and their evolution due to vacuum-UV and/or cosmic ray irradiation, and thermal processing.
Vacuum, 2011
Synchrotron radiation ultra-violet photoemission at different photon energies (17.1, 19.3, and 21... more Synchrotron radiation ultra-violet photoemission at different photon energies (17.1, 19.3, and 21.5 eV) has been used to study the interaction of O 2 with the TiO 2 (110)e(1 Â 2) surface reconstruction at temperatures between 77 and 320 K. At 77 K the results show a weak molecular chemisorption of the O 2 molecule on the surface. By analysing the thermal behaviour of the O 2 /TiO 2 system in a temperature range from 77 to 320 K, it has been found that between 120 and 200 K the O 2 molecule is dissociated.
2009 Second International Conference in Visualisation, 2009
The arrangement of atoms at the surface of a solid accounts for many of its properties: hardness,... more The arrangement of atoms at the surface of a solid accounts for many of its properties: hardness, chemical activity, corrosion, etc. are dictated by the precise surface structure. Hence, finding it, has a broad range of technical and industrial applications. The ability to solve this problem opens the possibility of designing by computer materials with properties tailored to specific applications. Since the search space grows exponentially with the number of atoms, its solution cannot be achieved for arbitrarily large structures. Presently, a trial and error procedure is used: an expert proposes an structure as a candidate solution and tries a local optimization procedure on it. The solution relaxes to the local minimum in the attractor basin corresponding to the initial point, that might be the one corresponding to the global minimum or not. This procedure is very time consuming and, for reasonably sized surfaces, can take many iterations and much effort from the expert. Here we report on a visualization environment designed to steer this process in an attempt to solve bigger structures and reduce the time needed. The idea is to use an immersive environment to interact with the computation. It has immediate feedback to assess the quality of the proposed structure in order to let the expert explore the space of candidate solutions. The visualization environment is also able to communicate with the de facto local solver used for this problem. The user is then able to send trial structures to the local minimizer and track its progress as they approach the minimum. This allows for simultaneous testing of candidate structures. The system has also proved very useful as an educational tool for the field.
Surface Science, 2000
High-resolution synchrotron radiation photoemission has been used to investigate the formation of... more High-resolution synchrotron radiation photoemission has been used to investigate the formation of the Cu(110)+c(2×2)-Si surface alloy. The complex spectra of the Si 2p core-level are analyzed as multiple component spectra for different Si coverages and annealing temperatures of the surface alloy. The results show that c(2×2) islands are formed from the very beginning of the growth and that Si has a high diffusion length on Cu. The thermal stability of the surface alloy has been studied by measuring real-time photoemission spectra at different temperatures. The surface alloy is stable up to 180°C. Above this temperature disruption of the surface alloy and clustering of the Si atoms can be observed.
Surface Science, 2013
The electronic structure of the TiO 2 (110)-(1 × 2) surface has been studied by means of angular ... more The electronic structure of the TiO 2 (110)-(1 × 2) surface has been studied by means of angular resolved ultraviolet photoemission spectroscopy (ARUPS). The valence band dispersion along the high symmetry surface directions, [001] and [1-10], has been recorded. The experimental data show no dispersion of the band-gap Ti 3d states. However, the existence of dispersive bands along the [001] direction located at about 7 eV below the Fermi level is reported. The existence of two different contributions in the emission from the defects-related state located in the gap of the surface is univocally shown for the first time.
Nanotechnology, 2010
We present a combination of experimental STM images and DFT calculations to understand the atomic... more We present a combination of experimental STM images and DFT calculations to understand the atomic scale contrast of features found in high-resolution STM images. Simulating different plausible structural models for the tip, we have been able to reproduce various characteristics previously reported in experimental images on TiO 2 (110)-(1 × 1) under controlled UHV conditions. Our results allow us to determine the influence of different chemical and morphological tip terminations on the atomic-resolution STM images of the TiO 2 (110)-(1 × 1) surface. The commonest images have been properly explained using standard models for a W tip, either clean or with a single O atom located at the apex. Furthermore, a double transfer of oxygen atoms can account for different types of bizarre atomic-resolution features occasionally seen, and not conclusively interpreted before. Importantly, we discuss how typical point-defects are imaged on this surface by different tips, namely bridging O vacancies and adsorbed OH groups.
Journal of Physics: Condensed Matter, 2006
In the last two decades surface science techniques have decisively contributed to our present kno... more In the last two decades surface science techniques have decisively contributed to our present knowledge of alkanethiol self-assembled monolayers (SAMs) on solid surfaces. These organic layers have been a challenge for surface scientists, in particular because of the soft nature of the organic material (which can be easily damaged by irradiation), the large number of atoms present in the molecules, and the complex physical chemistry involved in the self-assembly process. This challenge has been motivated by the appealing technological applications of SAMs that cover many fields of the emerging area of nanotechnology. Sulfur (S) is closely related to alkanethiols and can be used to understand basic aspects of the surface structure of SAMs. In this review we focus on the atomic/molecular structures of S-containing SAMs on Au(111). Particular emphasis is given to the substrate, adsorption sites, chemical state of the S-metal bond and also to the experimental and theoretical tools used to study these structures at the atomic or molecular levels.
IEEE Transactions on Magnetics, 1998
... It is particularly interesting for that purpose to grow nanoparticulate thin films having lar... more ... It is particularly interesting for that purpose to grow nanoparticulate thin films having large magnetization and coercivity, since optimized values of both parameters allow us to take advantage of the reduced sue of the magnetic entities in order to ... [I]. JL Dormann, D. Fiorani and ...
Icarus, 2008
Please cite this article in press as: Ruiz-Bermejo, M., et al CH 4 /N 2 /H 2 spark hydrophilic th... more Please cite this article in press as: Ruiz-Bermejo, M., et al CH 4 /N 2 /H 2 spark hydrophilic tholins: A systematic approach to the characterization of tholins.
Current Nanoscience, 2006
ABSTRACT Nucleic acids are natural biopolymers that store the genetic information of organisms. T... more ABSTRACT Nucleic acids are natural biopolymers that store the genetic information of organisms. This makes the detection and characterization of DNA and RNA a relevant task in biotechnology, with applications ranging from medicine to environmental control. During the last decades, a large effort has been focused on the development of biosensors, among them those devoted to the detection of nucleic acids in natural samples and those that include nucleic acids as nanosized capture probes for different biomolecules. DNA microarray technology has been successfully used in biotechnological applications including genotyping and gene expression studies. Nevertheless, the performance of DNA microarrays has a limitation imposed by the need of a previous fluorescent labeling of the target molecule to be analyzed. This encouraged the use of alternative detection methods, such as optical and electrochemical ones, and recently others based on surface characterization techniques. New trends in nanotechnology point towards new tools for manipulating molecules and macromolecules that could be developed as high performance biosensors. This interdisciplinary approach towards the integration of novel biosensors can benefit from the capability of certain polymers to form self-assembled monolayers (SAMs) on different surfaces. Thiol-modified DNA can form SAMs on gold surfaces with reduced efficiency, and the biological activity of the probe is decreased upon adsorption. Therefore, thiolated DNA has a very limited use in biosensor development. These constraints have been successfully by-passed using uncharged, artificial analogs of natural nucleic acids, such as peptide nucleic acids (PNAs), as molecular probes. This contribution reviews the state of the art in the use of nucleic acids and their analogs as biosensor nanomaterials, and summarizes the novel approach towards the development of biosensors based on SAMs of PNAs. Finally, we present the current trends in this promising aspect of nanobiotechnology.
Applied Physics Letters, 1990