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2D materials have attracted signi cant interest due to their unique physical, electronic and optical properties. Among them, some 2D materials present strong electron-hole con nement, extreme bendability, and high transparency. In particular, thin transition metal dichalcogendides (TMDs) represent a nearly ideal class of 2D materials for fundamental research at the limit of single-atom thickness, and have the potential to open up new technological opportunities beyond the reach of existing materials. TMDs single layers exhibit emergent characteristics different than those of their bulk counterparts, many of which show tunable electronic structure that can undergo for example transition from an indirect electronic band gap in crystals to a direct band gap in the monolayer regime. The hybridization of 2D TMDs with other layered materials or even other TMDs to build TMD-based heterostructures is a very effective way to boost their overall properties and thus expand their applications. One of the most appealing advantages offered by heterostructures is the design of new arti cial materials with tailored properties that are not exactly the ones of their original components, but new ones. For instance, the alignment of band structure at the interface of the heterostructure plays a critical role in optimizing the carrier transfer path in photodetectors. Although complex heterostructures have been fabricated via the van der Waals vertical stacking of different 2D materials, the in-situ fabrication of high-quality lateral heterostructures remains a challenge. The aim of this work is to explore the growth of novel TMD lateral heterostructures with Molecular Beam Epitaxy (MBE). We have grown metal-semiconductor and metal-superconductor TMD junctions in ultra-high vacuum conditions and characterized by Re ection high-energy electron diffraction (RHEED) and Atomic Force Microscopy (AFM). We have explored at first the suitability of PtSe2 and MoSe2 as semiconductors for a metal-s

Over the past decades, polymer mechanochemistry has focused on the development and application of advanced force application methods to better understand the mechanochemical response of mechanophores. In this regard, techniques such as ultrasonication and single-molecule force spectroscopy (SMFS) are used to activate and detect up to thousands of chemical events within a polymer single chain, allowing the researchers to probe the mechanochemical reactivity of these stress-responsive motifs. Here, the most recent contributions of the single-molecule force spectroscopy technique to this field are presented, putting emphasis on the fundamental parameters of the technique for triggering specific force responses and on the description of force–extension curves measured for single- and multi-mechanophore polymers. Moreover, new contributions of microscopy-based techniques in the field of polymer mechanochemistry, as well as the potential application of single-chain nanoparticles as mechanoresponsive materials, are highlighted.

[ES]: Esta tesis expone un estudio detallado sobre la síntesis en superficie de nanotiras de grafeno (en inglés 'Graphene Nanoribbons', GNRs) y la posterior caracterización de su estructura electrónica, principalmente empleando como técnica analítica, microscopía y espectroscopía de barrido de efecto túnel de baja temperatura (en inglés 'Low temperature-Scanning Tunnneling Microscopy/Spectrosocopy', LT-STM/STS) en condiciones de ultra alto vacío (en inglés 'Ultra High Vacuum', UHV). Para la obtención de los resultados detallados en esta tesis, se han empleado dos equipos de microscopía independientes, ambos ubicados en San Sebastián (Guipúzcoa). En primer lugar, 'Milano', un microscopio ensamblado a partir de elementos de distintios equipos y ubicado en el centro de investigación cooperativo 'CIC nanoGUNE'. En segundo lugar, 'Apollo', un equipo comercial Sigma-Omicron y situado en el instituto de investigación 'Centro de Física de Materiales' (CFM). Paralelamente al uso de estos microscopios, distintas técnicas de análisis de superficies, en concreto, espectroscopía de fotoemisión de rayos x (en ingles 'X-ray Photoemission Spectroscopy', XPS) y de ángulo resuelto (en inglés 'Angle-Resolved Photoemission Spectroscopy'), han complementado el estudio de las distintas reacciones de química de superficie que dan pie a la formación de las nanotiras de grafeno, así como el posterior estudio de sus propiedades electrónicas. El trabajo realizado durante esta tesis se enmarca dentro del campo científico conocido como 'nanociencia', definiendose esta como la rama de la ciencia centrada en el estudio de los fenómenos físico-químicos que se suceden en sistemas cuyas propiedades están gobernadas por las dimensiones que las definen, comprendiendose estas entre 1 y 100 nanometros., [EN]: This thesis presents a comprenhensive study on the on-surface synthesis and characterization of the electronic structure of di erent types of graphene nanoribbons (GNRs) formed on coinage metallic surfaces, being gold the most present substrate. Graphene nanoribbons (GNRs) are a new emergent material which is gaining considerable attention within the scientific community due to its wide-range potential applications derived from its exotic physical and chemical properties. Since GNRs derive from graphene, they preserve many of its interesting properties, such as the highest electron conductivity. In adittion, the reduced dimensionality of GNRs provide them with a tunable non-zero electrical band gap, no present in graphene, and required for its implementation into electronic devices. Moreover, and again in contrast with graphene, the presence of edges in GNRs brings the emergence of magnetic edge states with promising applications in spintronics. We employ on-surface chemistry startegies based on the use of aromatic molecular precursors for synthesizing the different GNRs studied here. By thermal annealing, we induce a controlled two-step reaction pathway to form these nanostructures onto different coinage metallic substrates, since their catalytic activity is needed for the product formation. The two chemical reaction accounted involves firstly, the merging of the molecular precursors into commonly linear polymric chains thorugh the well-known and controlled Ullmann coupling. In a second stage, higher temperatures induce the ciclodehydrogenation of the former polymers, giving rise to the formation of planar graphene nanoribbons.

Cyclotides are small cyclic polypeptides found in a variety of organisms, ranging from bacteria to plants. Their ring structure endows those polypeptides with specific properties, such as improved stability against enzymatic degradation. Optimal cyclotide activity is often observed only in the presence of intra-ring disulfide bonds. Synthesis of soft nano-objects mimicking the conformation of natural cyclotides remains challenging. Here, a new class of natural cyclotide mimics synthesized by a stepwise folding-activation-collapse process at high dilution starting from simple synthetic precursor polymers is established. The initial folding step is carried out by a photoactivated hetero Diels-Alder (HDA) ring-closing reaction, which is accompanied by chain compaction of the individual precursor polymer chains as determined by size exclusion chromatography (SEC). The subsequent activation step comprises a simple azidation procedure, whereas the final collapse step is driven by CuAAC in the presence of an external cross-linker, providing additional compaction to the final single-ring nanoparticles (SRNPs). The unique structure and compaction degree of the SRNPs is established via a detailed comparison with conventional single-chain nanoparticles (SCNPs) prepared exclusively by chain collapse from the exact same precursor polymer (without the prefolding step). The stepwise folding-activation-collapse approach opens new avenues for the preparation of artificial cyclotide mimetics.

[EN]: In the Nanotechnology era, many methods for synthesis of materials with welldefined nanoscale dimensions (1 nm = 10−9 m) have been developed. As a remarkable example, excellent size and shape control has been achieved for the synthesis of hard nanoparticles, such as quantum dots, gold nanoclusters or metal oxide nanoparticles. Similar control to produce soft nanoparticles based on polymers with dimensions below 10 nm has not been possible until just the beginning of the 21st Century. Advances in the synthesis of well-defined functional polymers through living radical polymerization processes, postfunctionalization techniques, as well as development of highly-efficient intrachain coupling reactions have paved the way to reliable production of singlechain polymer nanoparticles. The field of single-chain nanoparticles strives to create innovative nanostructures while also attempting to mimic biological nanomaterials. Natural macromolecules display primary structures with exact monomer sequence control allowing for the precise folding into three-dimensional shapes containing specific arrangements of functional groups on the surface and exterior. Obtaining synthetic nanostructures with the level of complexity seen in nature presents a significant challenge, with current systems unable to match the precision. Many areas of research including polymers are beginning to bridge the gap between synthetic and natural materials. The manipulation of single polymer chains, specifically intra-molecular folding into well-defined nanoparticles termed single-chain nanoparticles, or in brief SCNPs, is one particular avenue continually gaining interest. This area of research is simple conceptually, yet has results in many systems with complex behaviors. In “Single-chain nanoparticles: exploring novel synthesis routes, basic properties and potential applications” we try to made progress in this evolving field by exploring novel synthesis routes towards the development of functional, [ES]: En la era de la Nanotecnología, se han desarrollado muchos métodos para la síntesis de materiales con dimensiones bien definidas en la nanoescala (1 nm = 10−9 m). Un ejemplo notable es el excelente control sobre el tamaño y forma que se ha logrado en la síntesis de nanopartículas duras, tales como puntos cuánticos, nanopartículas de oro o nanopartículas de óxido metálico. Por el contrario, hasta principios del siglo XXI no ha sido posible obtener un control similar para producir nanopartículas blandas basadas en polímeros con dimensiones inferiores a 10 nm. Los avances en la síntesis de polímeros funcionales bien definidos a través de procesos de polimerización viva por radicales, técnicas de post-funcionalización, así como el desarrollo de reacciones de acoplamiento intra-cadena altamente eficientes, han allanado el camino hacia la producción fiable de nanopartículas poliméricas unimoleculares. El campo de las nanopartículas unimoleculares se esfuerza por crear nanoestructuras innovadoras a la vez que intentan imitar a los nanomateriales biológicos. Las macromoléculas naturales poseen un control exacto sobre la secuencia monomérica presente en sus estructuras primarias, lo que permite el plegado muy preciso en formas tridimensionales que contienen disposiciones específicas de grupos funcionales en la superficie y el exterior. Uno de los desafíos más significativos es la obtención de nanoestructuras sintéticas con el mismo nivel de complejidad que el que se halla en la naturaleza, ya que los sistemas desarrollados hasta el momento no son del todo capaces de igualar dicha precisión. Muchas áreas de investigación, incluida la ciencia de polímeros, están empezando a cerrar la brecha entre los materiales sintéticos y naturales. La manipulación de cadenas de polímeros individuales, específicamente el plegamiento intra-molecular para dar lugar a nanopartículas bien definidas denominadas “nanopartículas unimoleculares”, es una vía de particular interés que está en co

El desarrollo de este proyecto de tesis está basado en el estudio de las propiedades ópticas de nano-estructuras de interés físico por medio de teorías ab initio. Las teorías ab initio nos permiten estudiar una amplia gama de sistemas cambiando solamente unos parámetros que dependen del sistema sin tener que reconsiderar la metodología de trabajo de la teoría. En particular, se ha usado la Teoría del Funcional de la Densidad (DFT) para obtener información sobre la estructura electrónica de los materiales estudiados. Mientras que la Teoría del Funcional de la Densidad Tiempo-Dependiente (TDDFT) nos ha permitido estudiar en detalle como los electrones de dichos materiales se comportan cuando son sometidos a un campo eléctrico. Las dos teorías ab initio, DFT y TDDFT han crecido en popularidad debido a la mayor potencia de los ordenadores y su favorable complejidad computacional, es decir, a que el coste computacional aumenta siguiendo potencias de exponentes relativamente bajos del número de átomo en el sistema. En este proyecto hemos empleado el método y código DFT SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms). SIESTA es un método y código DFT de licencia GPL que se empezó a desarrollar en los años noventa y que todavía tiene una comunidad de desarrolladores que siguen ampliando y mejorando el código. Con SIESTA hemos calculado las propiedades electrónicas de estado del estado de base de los sistemas. Estas propiedades incluyen las curvas de dispersión energía-momento, las energías de los niveles electrónicos, la energía total, la densidad electrónica, la geometría de equilibrio, etc. La propiedades ópticas que han sido el objeto principal de esta investigación han sido calculadas y estudiadas por medio del código MBPT-LCAO (Many Body Perturbation Theory with Linear Combination Atomic Orbitals), un código que todavía no se distribuye al público en general y que está en desarrollo, siendo su principal desarrollador el Dr. Peter Koval. A

In this work, we show the possibility of tailoring the molecular arrangement, as well as chemical and structural modifications, of porphyrins at monolayer saturation coverage on TiO(110) by synchrotron photoemission spectroscopy, electron diffraction, STM topography, and DFT calculations. Free-base tetraphenylporphyrins (2H-TPP) adsorb on the oxygen rows, where they can spontaneously capture two additional hydrogen atoms at their iminic nitrogens (4H-TPP). Both 2H-TPP and 4H-TPP molecules aggregate into a commensurate phase at the saturation coverage of 1 ML. Upon sample heating, a self-metalation reaction sets in at 100 °C, yielding full metalation of the saturated monolayer at ∼200 °C. The Ti atoms are extracted from the substrate and, by simultaneous dehydrogenation of the pyrrolic nitrogen atoms, incorporated into the porphyrin macrocycle, where they remain coordinated to two underlying oxygen atoms. Neither the adsorption geometry (on-bridge, atop the oxygen rows) nor the molecular arrangement changes across the self-metalation transition up to 300 °C. On one hand, the robustness of this saturation phase makes it a promising system for implementation in applications for photocatalysis and photovoltaic devices. On the other hand, the possible manifestation of metal exchange with the very reactive Ti atoms must be taken into account when designing porphyrin-sensitized solar cells because the critical temperature for the onset of self-metalation is very close to the normal operating temperature of photovoltaic devices.

Enzymes are the most efficient catalysts known for working in an aqueous environment near room temperature. The folding of individual polymer chains to functional single-chain nanoparticles (SCNPs) offers many opportunities for the development of artificial enzyme-mimic catalysts showing both high catalytic activity and specificity. In this review, we highlight recent results obtained in the use of SCNPs as bioinspired, highly-efficient nanoreactors (3–30 nm) for the synthesis of a variety of nanomaterials (inorganic nanoparticles, quantum dots, carbon nanodots), polymers, and chemical compounds, as well as nanocontainers for CO capture and release.

[EN]: In this thesis we apply time-dependent density functional theory (TDDFT) to study nonadiabatic phenomena in the interaction of charged particles, atoms, and molecules with spherical metallic clusters. These phenomena include the screening processes of projectiles in matter as well as the energy loss processes in a broad range of projectile velocities. In this thesis we focus on two related topics. The first part, described in Chapter 4, is devoted to the study of the coupled dynamic screening of a localized hole and a photoelectron emitted from a metal cluster or from an adsorbate on the surface of the cluster using a semi-classical model. The motion of the photoelectron is represented classically, while the electronic density dynamics in the cluster is calculated with TDDFT.We calculate the energy loss of the photoemitted electron moving away from the cluster with different velocities. As a result we see that the dynamic screening of the hole by the cluster electrons affects the motion of the photoemitted electron, namely it gives rise to a significant reduction of the energy lost by the photoelectron. In the second part we present the study of energy loss processes in the interaction of antiprotons and protons, as well as hydrogen dimers, with spherical clusters., [ES]: La estructura electrónica y las propiedades de los sólidos, superficies y nanoestructuras se pueden estudiar experimentalmente mediante diferentes técnicas espectroscópicas. En estos experimentos, el material se estudia mediante la interacción con partículas incidentes tales como electrones (espectroscopía electrónica de perdida de energía, EELS), fotones (espectroscopía de fotoemisión, PES), o iones (dispersión de iones, IS). Los proyectiles que penetran en el sólido o en la superficie crean excitaciones electrónicas en el material estudiado. La descripción cuantitativa de la dinámica de dichas partículas en las superficies y en los sólidos, así como la dinámica electrónica asociada, es esencial para la correcta interpretación de los resultados de los experimentos. Esta tesis está dedicada al estudio de las excitaciones electrónicas creadas durante la interacción de partículas cargadas y neutras con agregados metálicos. Las excitaciones electrónicas están asociadas con la disipación de la energía, lo que en nuestro caso significa la transferencia de energía cinética de un proyectil en movimiento a los electrónes de un agregado metálico o viceversa. En concreto, estudiamos los procesos de disipación en fenómenos físicos tales como el apantallamiento electrónico y el frenado de electrónes durante la fotoemisión, el apantallamiento electrónico y el frenado de iones y moléculas que atraviesan agregados metálicos y la fricción electrónica en superficies metálicas. La investigación de estos procesos nos permite obtener información sobre las propiedades de ambos, el material estudiado y el proyectil. La complejidad de estos procesos dinámicos en sólidos es un reto para los métodos teóricos. En esta tesis estudiamos la interacción de los agregados metálicos con partículas en movimiento utilizando una metodología eficiente basada en la teoría del funcional de la densidad dependiente del tiempo (TDDFT), un método ab initio basado en la mecánica cuántica que nos permite

Uno de los aspectos más apasionantes de la predicción y caracterización de estructuras cristalinas bajo condiciones extremas es el reto interdisciplinar que representa. La física de materiales y la química inorgánica coexisten para caracterizar nuevos materiales, que bajo condiciones de alta presión originan estructuras cristalinas con comportamientos y propiedades singulares. En las páginas de esta tesis se presenta el estudio teórico de la predicción de estructuras cristalinas de tres grupos de compuestos a altas presiones. Concretamente, la predicción de las estructuras cristalinas a distintas presiones ha sido realizada mediante los algoritmos evolutivos implementados en el código de CALYPSO, combinada con optimizaciones, utilizando cálculos ab-initio basados en la Teoría del Funcional de la Densidad (DFT por sus siglas en inglés) implementadas en VASP. Los grupos de compuestos que se han estudiado son los hidruros de boro, boruros de litio y el telururo de arsénico.

[ES]: El estudiar "la relajación dieléctrica y la estructura de materiales complejos: en entidades supra-moleculares y materiales híbridos", se refiere a la interpretación de resultados obtenidos por medio del análisis cuantitativo de los fenómenos de relajación dieléctrica y su relación con los resultados de su caracterización estructural, en particular, para dos diferentes familias de materiales poliméricos. Este tipo de materiales presentan una dinámica compleja, y en muchos casos exhiben relajaciones jerárquicas, que se extienden en un amplio rango de tamaños y escalas de tiempo. En esta tesis, y como primer sistema considerado, investigamos la relajación dieléctrica de un oligómero funcionalizado. Su unidad molecular esta compuesta por dos partes de distinta composición; un primer "bloque" esta compuesto por unidades de dimetilsiloxano y el segundo esta compuesto por una cadena alifática cuya terminación es un grupo funcional carboxilo. Centraremos la atención en la interpretación molecular y el rol que juegan las interacciones específicas en la relación entre la estructura y dinámica del material. Para ello, ha sido necesario una investigación comparativa entre dos sistemas similares pero cuyas interacciones específicas son distintas, en particular el grupo funcional terminal fue modificado reemplazando el grupo hidroxilo por el grupo metilo con el objetivo de bloquear las interacciones tipo puente de hidrógeno. Por otro lado hemos estudiado materiales complejos con relevancia en el desarrollo de nuevas aplicaciones industriales. En particular hemos estudiado materiales adhesivos híbridos sintetizados mediante mini emulsion. Específicamente, investigamos la relación entre las condiciones de síntesis, el análisis de la relajación dieléctrica y la caracterización estructural de los componentes solubles e insolubles de un material adhesivo híbrido compuesto por grupos acrílicos y poliuretanos. Una vez determinado el origen molecular de los procesos de relajación, [EN]: Dielectric relaxation and structure of complex materials: supramolecular ensembles and hybrid materials, refers to the interpretation of the results obtained by the dielectric relaxation analysis and the relation with the structural characterization of two different families of polymeric materials investigated, at different molecular levels. As the first system under study and due to practical reasons (well defined molecular-constituents materials) we studied the dielectric relaxation of small length carboxyl terminated dimethylsiloxane block-copolymers, centring the attention into understanding which was the role of specific interactions and their relation with the structure and dynamics. For this purpose, a comparative investigation of polymers with different specific interactions was necessary. A simple scenario of this problem was handled by the study of two different ODMS co-oligomer samples, which were expected to have distinct specific interactions. On the other hand and we have studied materials that are closer to technological applications. Particularly we investigate the relation of the synthetic conditions, dielectric relaxation analysis and structural characterization of different hybrid Acrylic-Polyurethane latex materials. The experimental techniques employed in both investigations were mostly dielectric spectroscopies in a broad range of frequencies have been combined to determine polymer dynamics. X-ray diffraction experiments have also been performed to study the structural properties of the materials. In addition, thermal calorimetric characterization has been used in the analysis.

This thesis concerns with theoretical modelling from first principles of dynamics of two gas-surface systems (oxygen on silver and carbon monoxide on ruthenium) that are relevant to the heterogeneous catalysis. An accurate potential energy surface is constructed for the interaction of molecular oxygen with the Ag(110) surface based on density functional theory calculations. Using this potential energy surface, the dissociative and molecular adsorption dynamics is studied by performing trajectory calculations. Accuracy of different approximations to exchange-correlation functional in density functional theory for the modelling of the oxygen-silver system is tested. Furthermore, laser induced desorption of oxygen from Ag(110) is studied. Dynamics of carbon monoxide adsorption and scattering on Ru(0001) is also studied by performing trajectory calculations on top of a density functional based potential energy surface. These simulations can explain the results of molecular beam experiments.

At present the prediction and characterization of the emission output of a diffusive random laser remains a challenge, despite the variety of investigated materials and theoretical interpretations given up to now. Here, a new mode selection method, based on spatial filtering and ultrafast detection, which allows to separate individual lasing modes and follow their temporal evolution is presented. In particular, the work explores the random laser behavior of a ground powder of an organic-inorganic hybrid compound based on Rhodamine B incorporated into a di-ureasil host. The experimental approach gives direct access to the mode structure and dynamics, shows clear modal relaxation oscillations, and illustrates the lasing modes stochastic behavior of this diffusive scattering system. The effect of the excitation energy on its modal density is also investigated. Finally, imaging measurements reveal the dominant role of diffusion over amplification processes in this kind of unconventional lasers.

We have performed gas-phase absorption spectroscopy in the Soret-band region of chlorophyll (Chl) a and b tagged by quaternary ammonium ions together with time-dependent density functional theory (TD-DFT) calculations. This band is the strongest in the visible region of metalloporphyrins and an important reporter on the microenvironment. The cationic charge tags were tetramethylammonium, tetrabutylammonium, and acetylcholine, and the dominant dissociation channel in all cases was breakage of the complex to give neutral Chl and the charge tag as determined by photoinduced dissociation mass spectroscopy. Two photons were required to induce fragmentation on the time scale of the experiment (microseconds). Action spectra were recorded where the yield of the tag as a function of excitation wavelength was sampled. These spectra are taken to represent the corresponding absorption spectra. In the case of Chl a we find that the tag hardly influences the band maximum which for all three tags is at 403 ± 5 nm. A smaller band with maximum at 365 ± 10 nm was also measured for all three complexes. The spectral quality is worse in the case of Chl b due to lower ion beam currents; however, there is clear evidence for the absorption being to the red of that of Chl a (most intense peak at 409 ± 5 nm) and also a more split band. Our results demonstrate that the change in the Soret-band spectrum when one peripheral substituent (CH3) is replaced by another (CHO) is an intrinsic effect. First principles TD-DFT calculations agree with our experiments, supporting the intrinsic nature of the difference between Chl a and b and also displaying minimal spectral changes when different charge tags are employed. The deviations between theory and experiment have allowed us to estimate that the Soret-band absorption maxima in vacuo for the neutral Chl a and Chl b should occur at 405 nm and 413 nm, respectively. Importantly, the Soret bands of the isolated species are significantly blueshifted compa

Los avances tecnológicos ocurridos a partir del siglo XVI han permitido explorar tanto el mundo microscópico como el macroscópico, gracias al desarrollo de dispositivos basados en lentes y espejos, desconocidos hasta entonces. El telescopio, inventado por Hans Lippershey y utilizado por Galileo Galilei y sus contemporáneos para realizar sus observaciones astronómicas, ha permitido revelar los misterios del cosmos. En la escala opuesta, el uso del microscopio por Zacharias Janssen, Robert Hooke y Antonie van Leeuwenhoek inauguró el estudio del mundo de los microorganismos y de lo diminuto. En el siglo XVII se produjo un considerable avance en el estudio la naturaleza de la luz, con dos teorías que años más tarde se revelarían como complementarias: la teoría corpuscular de Isaac Newton y la teor´ıa ondulatoria de Christiaan Huygens. Posteriormente, James Clerk Maxwell postuló la teoría electromagnética, mediante la cual estableció la naturaleza ondulatoria de la luz compuesta de oscilaciones de campos eléctricos y magnéticos y sentó las bases para la posterior aparición de la óptica física y de la fotónica. Unas décadas más tarde, el desarrollo de la óptica cuántica y de la dualidad onda-partícula de la luz permitieron una comprensión más profunda de la naturaleza de la luz. Los microscopios modernos, apoyados por potentes ordenadores y tecnologías de alta precisión, permiten observar microorganismos y otros objetos muy pequeños a escala nanométrica, así como también estudiar procesos ultrarápidos en volúmenes reducidos. Sin embargo, el efecto de la difracción impone a menudo una barrera a nuestra capacidad de estudiar el mundo microscópico. Debido a su naturaleza ondulatoria, la óptica convencional no permite enfocar la luz por debajo de un área menor que aproximadamente la mitad su longitud de onda, es decir, en dimensiones inferiores a unos pocos cientos de nanómetros. Por tanto, objetos menores de unos 200 nanómetros no pueden ser distinguidos mediante microscopio, Las transiciones entre estos niveles energéticos corresponden a menudo a frecuencias ópticas, y se manifiestan en forma de líneas espectrales muy estrechas de absorción y emisión, que pueden ser sintonizadas si se cambian las propiedades estructurales o el tamaño del sistema. Los metales nobles tales como la plata y el oro presentan gran interés en aplicaciones plasmónicas y nanofotónicas porque exhiben claras resonancias electromagnéticas en la región visible e infrarroja del espectro. Las resonancias en estructuras métalicas permiten localizar los campos electromagnéticos en regiones muy inferiores a lo permitido por el límite de difracción. En la actualidad se buscan materiales alternativos a los anteriormente apuntados, que presenten propiedades ópticas novedosas y útiles para mejorar el control sobre los campos eléctricos y magnéticos, en regiones de dimensiones nanométricas y en un espectro lo más amplio posible. Dentro de este esfuerzo se encuadran diversos trabajos que han comenzado a investigar metales plasmónicos no convencionales, partículas pequeñas de materiales dieléctricos, cristales fonónicos y sistemas electrónicos bidimensiones, entre otros. De manera más específica, algunos metales plásmonicos no convencionales tales como el paladio, el platino y el cobalto pueden presentar pérdidas de energía superiores a las del oro o la plata pero, como contrapartida, pueden resultar útiles en aplicaciones tales como catálisis, sensórica de gases o magneto-óptica, por ejemplo. Por otra parte, las partículas dieléctricas de tamaño submicrométrico permiten excitar una fuerte respuesta eléctrica y magnética en el rango espectral del infrarrojo cercano. Los materiales polares como el carburo de silicio también presentan resonancias ópticas claras en frecuencias que corresponden al infrarrojo medio, debidas a las vibraciones fonónicas de la estructura cristalina. Finalmente, el grafeno, los aislantes topológicos y otros materiales constituidos por gases electrónicos

Hydrated cements have pore sizes that range from a few nanometers to microns. The physical and chemical properties of cements (creep, strength, chemical reactivity and shrinkage) are significantly influenced by water molecules in this pore network. Hence, a main task to the cement science is to understand the behavior of water in the pore network to control the physical and chemical properties of cement-based materials. It is known that the structural and physical properties of water near surfaces or confined in small cavities, can be different than those of bulk water. Solid surfaces affect the behavior of water mainly reducing the tetrahedral network of bulk water. However after decades of study, the structure, dynamics and physical properties of this near-surface water remains poorly understood. In this thesis, we focus on the problem of the dynamics of water confined in the nanopores of different sizes of cement-like materials by means of broadband dielectric spectroscopy. This technique has proven to be powerful when studying the reorientation dynamics of polar molecules such as water. In addition, thermal analysis and other spectroscopic techniques have been used to characterize the structure of these materials. This thesis contains four main topics: 1) Dynamics of water in C-S-H gel, the main binding phase of cement materials. From a scientific perspective, the C-S-H gel offers an attractive confinement system where chemical and geometrical effects of the confinement of water can be investigated. In C-S-H gel, the water molecules are trapped mainly in the interlayer space between the highly disordered calcium silicate layers forming the interlayer water. 2) Dynamics of water confined in C-S-H synthesized with the addition of both silica- and amino propyl functionalized nano-particles, before the hydration reaction. 3) Dynamics water confined in tobermorite (natural and synthetic). Structurally Tobermorite is considered an analogue of C-S-H gel. 4) Dynamics of, The results of this thesis showed that the nature of water in all these systems split into different relaxations (normally three different dynamics) depending on the different chemical environment and/or physical environment where water molecules are situated. Some relaxations were unequivocally related with water molecules relaxing in small gel pores (< 1 nm) whereas other water molecules were structurally linked to the structure of the different materials analyzed. The main relaxation of water confined in C-S-H, C-S-H with the addition of nanoparticles and tobermorite were faster than the so-called universal beta-relaxation of water. By contrast, water in Portland cement was similar to the universal beta-relaxation of water. The water dynamics in Portland cements showed similar characteristics to that observed in other well-defined confinement systems such as molecular sieves or MCM-41. In this thesis, we will discuss the implications of these observations.

First-principles calculations within the framework of real-space time-dependent density functional theory have been performed for the complete chlorophyll (Chl) network of the light-harvesting complex from green plants, LHC-II. A local-dipole analysis method developed for this work has made possible the studies of the optical response of individual Chl molecules subjected to the influence of the remainder of the chromophore network. The spectra calculated using our real-space TDDFT method agree with previous suggestions that weak interaction with the protein microenvironment should produce only minor changes in the absorption spectrum of Chl chromophores in LHC-II. In addition, relative shifting of Chl absorption energies leads the stromal and lumenal sides of LHC-II to absorb in slightly different parts of the visible spectrum providing greater coverage of the available light frequencies. The site-specific alterations in Chl excitation energies support the existence of intrinsic energy transfer pathways within the LHC-II complex.

The exact color of light absorbed by chlorophyll (Chl) pigments, the light-harvesters in photosynthesis, is tuned by the protein microenvironment, but without knowledge of the intrinsic color of Chl it remains unclear how large this effect is. Experimental first absorption energies of Chl a and b isolated in vacuo and tagged with quaternary ammonium cations are reported. The energies are largely insensitive to details of the tag structure, a finding supported by first-principles calculations using time-dependent density functional theory. Absorption is significantly blue-shifted compared to that of Chl-containing proteins (by 30–70 nm). A single red-shifting perturbation, such as axial ligation or the protein medium, is insufficient to account even for the smallest shift; the largest requires pigment–pigment interactions.

We simulate the scattering of O2 from Ag(111) with classical dynamics simulations performed on a six-dimensional potential energy surface calculated within semilocal density-functional theory. The enigmatic experimental trends that originally required the conjecture of two types of repulsive walls, arising from a physisorption and chemisorption part of the interaction potential, are fully reproduced. Given the inadequate description of the physisorption properties in semilocal density-functional theory, our work casts severe doubts on the prevalent notion to use molecular scattering data as indirect evidence for the existence of such states. © 2014 American Physical Society.

The random laser features around threshold in a ground powder of a silica gel containing Rhodamine 6G-doped silica nanoparticles under one- and two-photon excitation are analyzed. The lasing threshold following two-photon pumping is fifty times higher than after one-photon excitation. Theoretical calculations by using a light diffusive propagation model are in agreement with the experimental results.

Centro de Física de Materiales (CFM) is a research center focused in Materials Science. Born in 1999 as a joint initiative between Consejo Superior de Investigaciones Científicas (CSIC) and Universidad del Pais Vasco – Euskal Herriko Unibertsitatea (UPV-EHU), the long term goal of CFM is to push forward the frontiers of knowledge in our areas of expertise, by putting together stable teams with a record of excellence in scientific research. CFM is distinguished as a “Basque Excellence Research Center” by the Basque Government (BERC Program).

Laser slope and threshold properties have been investigated in Nd stoichiometric crystal powders as a function of pump wavelength and pump beam size. Above a given pumped area, the laser slope and the threshold pump energy per unit area are invariant and the known theoretical expressions are well fulfilled. Likewise, the size of the stimulated emission zone as a function of the pump beam area has been measured, also showing a different behavior above or below a given pumped area value which coincides with the one mentioned above. In conclusion, two different operating regimes with different performances are clearly observed as a function of the pump beam area.

[ES]: En esta tesis doctoral se presentan los resultados finales de los desarrollos y cálculos de las propiedades ópticas de diferentes sistemas finitos basados en la Teoría del Funcional de la Densidad Dependiente del Tiempo (TDDFT). La primera parte trata con la extensión de la metodología en espacio real y tiempo real de la absorción óptica a otras espectroscopias diferenciales: Dicroísmo Circular y Dicroísmo Circular Magnético, aquí se demuestra y discute los problemas generales de la implementación relacionados con la invarianza de gauge en los operadores cuando potenciales no locales acoplados a campos magnéticos son incluidos en la solución del Hamiltoniano electrónico. La segunda parte contiene los resultados de nuestras investigaciones acerca de los estados excitados en tres tipos de estructuras moleculares con interés tecnológico en diferentes áreas de la nanotecnología, mostramos las ventajas, limitaciones y de la TDDFT mostrando nuestros resultados comparados con los experimentos.

Materials Physics Center / Materialen Fisika Zentrua / Centro de Física de Materiales (CFM) is a joint center between the Spanish Scientific Research Council (CSIC) and the University of the Basque Country (UPV/EHU). CFM was created in 1999 and holds its headquarters in Donostia – San Sebastián. Since 2010, CFM occupies its own building in the Ibaeta Campus of UPV/EHU. CFM is distinguished as a “Basque Excellence Research Center” by the Basque Government (BERC Program).

In thesis we analyse and implement first-principle reduced density matrix (RDM) theories as one promising framework for ab-inito calculations, both for equilibrium and nonequilibrium situations. We spend the first part of the thesis concentrating on the basic properties of density matrix theories at equilibrium. We will exploit simple systems made of two particles which are harmonically confined, as a ground to illustrate usefulness of density matrices. For such systems, we use the one-body RDM to calculate some quantities of interest, such as momentum density, from the one-body RDM. Next, we obtain natural orbitals and their occupation numbers for some of the models, and for one model we express exactly the two-body RDM in terms of the one-body RDM. Moreover, we utilise the differential virial theorem to establish a unified description of the entire family of these model systems in terms of density. In the second part we will deal with nonequilibrium cases where we need to calculate the time evolution of RDMs. We analyse the Born, Bogoliubov, Green, Kirkwood and Yvon (BBGKY) hierarchy of equations for describing the full time-evolution of a many-body fermionic system in terms of its reduced density matrices (at all orders). We provide an exhaustive study of the challenges and open problems linked to the truncation of such hierarchy of equations to make them practically applicable. We restrict our analysis to the coupled evolution of the one- and two-body reduced density matrices, where higher order correlation effects are embodied into the approximation used to close the equations. We prove that within this approach, the number of electrons and total energy are conserved, regardless of the employed approximation. Further, we demonstrate that although most of the truncation schemes available in the literature give acceptable ground state energy, when applied to describe driven electron dynamics exhibit undesirable and unphysical behaviour, e.g., violation and even d

Protection of acetylenic monomers is a common practice to avoid parasitic side reactions during polymerization. Herein, we report that redox-initiated RAFT polymerization allows the direct, room temperature synthesis of a variety of single-chain nanoparticle precursors (displaying narrow molecular weight dispersity, M̄ wM̄ n = 1.12 -1.37 up to M̄ w = 100 kDa) containing well-defined amounts of naked, unprotected acetylenic functional groups available for rapid and quantitative intrachain cross-linking via metal-catalyzed carbon-carbon coupling (i.e., C-C click chemistry). To illustrate the useful self-clickable character of the new unprotected acetylenic precursors, single-chain nanoparticles have been prepared for the first time in a facile and highly efficient manner by copper-catalyzed alkyne homocoupling (i.e., Glaser-Hay coupling) at room temperature under normal air atmosphere.

The Materials Physics Center (“Centro de Física de Materiales”, CFM) is a joint center of the Spanish National Research Council (CSIC) and the University of the Basque Country (UPV/EHU). The CFM is part of a network of Materials Science Institutes of the CSIC and its research activity is focused on the physical aspects of basic materials science in general.