Seminarios y Conferencias

João Carlos Mesquita Coelho

21.10.2022

The road to flexible and sustainable nanomaterials-based energy storage devices
CENIMAT|i3N – NOVA School of Science and Technology (FCT-NOVA), Costa da Caparica, Portugal
Lugar: Salón de Grados del cicCartujaII

In the last few years, a lot of interest has been shown in nanomaterials, which can exhibit enhanced or totally new properties when compared to their bulk counterparts.1–4 For instance, the confinement of charge and heat in two dimensional (2D) graphene results in outstanding electrical, optical and mechanical properties. Not surprisingly, a wide range of nanomaterials has been suggested for several industrial applications.5–7 Special attention has been given to the role of nanomaterials in the energy sector due to the ongoing climate change and transition to greener energy sources. In addition, the advent of digital manufacturing technologies, such as 3D, inkjet printing and laser process/patterning demonstrated a huge potential to disrupt and create technologies such as wearable electronics and flexible, stretchable portable devices. A key technical constraint for the large-scale utilization of these devices is energy autonomy, which requires the development of flexible energy sources/storage systems, such as micro-supercapacitors and thin-film Li/Na-ion batteries. Inks based on conductive nanomaterials are promising material platforms for these flexible devices. For instance, due to their superior mechanical and electrical properties, carbon nanotubes (CNTs) and graphene, can be implemented as efficient current collectors, thus removing the need for bulky/heavy metallic components, while nanomaterials are responsible for the energy storage process.8,9 In order to maximize the exploitation of these material properties, optimized inks, formulations and depositions methodologies must be designed and characterized. Considering the wider societal awareness towards environmental issues and on-going legislations, energy storage devices of the future will have to be based in efficient, eco-friendly, and sustainable manufacturing processes.

In this talk, I will exhibit the advantages of 2D based energy storage devices along with approaches for their sustainable fabrication. A special attention will be given to green solvents, such as cyrene, and biodegradable substrates such as paper and cork. The combination of nanomaterials and efficient eco-friendly manufacturing technologies will open the avenue for the large-scale production of ultra-light and thin flexible energy storage devices. Additionally, by defining a smart integration approach based on hybrid electronics the pro-posed methodology will further close the gap between conventional and flexible electronics.

1. Chhowalla, M. et al. The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nat. Chem. 5, 263–275 (2013).
2. Coleman, J. N. Liquid Exfoliation of Defect-Free Graphene. Acc. Chem. Res. 46, 14–22 (2013).
3. Coleman, J. N. et al. Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials. Science (80-. ). 331, 568–571 (2011).
4. Nicolosi, V., Chhowalla, M., Kanatzidis, M. G., Strano, M. S. & Coleman, J. N. Liquid Exfoliation of Layered Materials. Science (80-. ). 340, 1226419 (2013).
5. McAteer, D. et al. Liquid Exfoliated Co(OH) 2 Nanosheets as Low-Cost, Yet High-Performance, Catalysts for the Oxygen Evolution Reaction. Adv. Energy Mater. 8, 1702965 (2018).
6. Coelho, J. et al. Manganese oxide nanosheets and a 2D hybrid of graphene-manganese oxide nanosheets synthesized by liquid-phase exfoliation. 2D Mater. 2, 025005 (2015).
7. Jaśkaniec, S. et al. Low-temperature synthesis and investigation into the formation mechanism of high quality Ni-Fe layered double hydroxides hexagonal platelets. Sci. Rep. 8, 4179 (2018).
8. Coelho, J., Kremer, M. P., Pinilla, S. & Nicolosi, V. An outlook on printed microsupercapacitors: Technology status, remaining challenges, and opportunities. Current Opinion in Electrochemistry vol. 21 69–75 (2020).
9. Zhang, C. J. et al. Stamping of Flexible, Coplanar Micro-Supercapacitors Using MXene Inks. Adv. Funct. Mater. 28, 1705506 (2018).
10. Kelly, A. G. et al. All-printed thin-film transistors from networks of liquid-exfoliated nanosheets. Science (80-. ). 356, 69–73 (2017).
11. Lin, Y., Gao, Y., Fang, F. & Fan, Z. Recent progress on printable power supply devices and systems with nanomaterials. Nano Res. 11, 3065–3087 (2018).

Dr. Ibraheem Yousef

02.12.2019

Applications of infrared microspectroscopy using the synchrotron radiation of Alba light source
MIRAS Beamline Responsible - Experiments Division in ALBA Synchrotron
Lugar: Salón de Grados CICCARTUJA2

Conferencia dentro del PROGRAMA DE DOCTORADO «CIENCIA Y TECNOLOGÍA DE NUEVOS MATERIALES”

Dr. Andries Meijerink

24.10.2019

Multi Photon Phosphors
Utrecht University
Lugar: Salón de Grados cicCartuja2

Lanthanides have transformed the world of lighting in the past 40 years. Presently, almost all artificial light sources rely on emission of light by lanthanide ions. In many luminescent materials, also known as phosphors, one-to-one photon conversion downshifts one high energy photon to one lower energy photon in the desired spectral region. However, recently, there is a significant increase of attention for multi-photon phosphors relying on multi-photon conversion processes, either upconversion or downconversion. Insight in the multi-photon processes is not trivial but is needed to understand the mechanism and improve the efficiency of spectral conversion processes in multi-photon phosphors which is crucial for applications, including solar cells to reduce spectral mismatch losses.

In this presentation a short historical introduction to single- and multi-photon conversion phosphors will be followed by an overview of recent developments of efficient up- and downconversion materials. Next it will be discussed how insight can be obtained in the mechanism and efficiency of up- and downconversion processes. An important aspect involves modelling of energy transfer and ligand quenching. For both up- and downconversion examples will be given on how modelling of luminescence decay curves can provide quantitative insight. A new ligand-quenching model will be presented and applied to understand multi-phonon vibrational quenching in NaYF₄:Er,Yb upconversion nanocrystals. Finally a new method will be presented that provides direct proof for downconversion. Correlated emission of photons in photon cutting materials can serve as a fingerprint for the occurrence of downconversion and can even be used to quantify the downconversion efficiency.

Figure 1 – Illustration correlated photon counting to demonstrate two-photon emission using NaLaF₄:Pr³⁺ as model system. (a) Two-photon emission on Pr³⁺. (b) Schematic set-up for correlated photon counting (c, d) Emission of Pr³⁺ in blue and red spectral region detected by separate detectors. (e) Correlated photon-counting signal.

Dr. Javier García Martínez

04.04.2019

Descubrimiento y Comercialización de una Nueva Familia de Catalizadores
Catedrático de Química Inorgánica de la Universidad de Alicante y Director del Laboratorio de Nanotecnología Molecular (NANOMOL)
Lugar: Seminario cicCartuja2

El pequeño tamaño de los microporos de las zeolitas dificulta la entrada y salida de las moléculas voluminosas al interior de su estructura; lo que afecta negativamente a la actividad y a la selectividad de un buen número de catalizadores industriales que contienen zeolitas, como por ejemplo, los catalizadores de craqueo catalítico (FCC). Para solucionar esta limitación, hemos desarrollado una nueva estrategia que involucra el tratamiento de zeolitas en disoluciones de surfactantes catiónicos en la presencia de una base. Este proceso post-sintético permite introducir, de forma sencilla y controlable, la mesoporosidad en una gran variedad de zeolitas, a la vez que éstas mantienen sus propiedades más sobresalientes, tales como cristalinidad, estabilidad hidrotermal y actividad catalítica. Este método permite solventar las limitaciones de otros materiales mesoporosos preparados con surfactantes, tales como MCM-41 y otros similares, que carecen precisamente de las propiedades que acabamos de señalar. La presencia de mesoporosidad dentro de la estructura de la zeolita se ha confirmado mediante un amplio conjunto de técnicas de caracterización avanzadas.

Tras el estudio de la actividad y selectividad catalítica de estas zeolitas mesoporosas a escala laboratorio, se procedió a escalar la tecnología produciendo varios kilos de catalizador FCC en una planta piloto. Durante la presentación se mostrarán los resultados catalíticos del craqueo de gasóleo de vacío obtenidos en una unidad de ACE (Advanced Catalytic Evaluation). Las zeolitas mesoporosas que aquí se presentan son una realidad comercial gracias al acuerdo entre la empresa Rive Technology y Grace. Hoy en día estos catalizadores se están utilizando con éxito en varias refinerías de EEUU. En la parte final de la presentación se mostrarán algunos resultados obtenidos en la refinería Alon Big Spring de Texas, EEUU, en el que se confirman los resultados obtenidos a escala piloto. Como era de esperar, la presencia de mesoporosidad en la zeolita incrementa el número de barriles procesados y la producción de gasolina y diésel, a la vez que se reduce notablemente la generación de CO2 y de gases.

Dr. P. Brault

08.11.2018

Plasma sputtering synthesis of nanocatalyst for fuel cells: Experiments and molecular dynamics simulations
CNRS-Université d’Orléans
Lugar: Salón de Grados cicCartuja2

Hydrogen powered fuel cells are expected be a relevant solution for green and sustainable energy delivery. Major breakthroughs remain to be achieved. One of them is to lower the noble metal content used as catalysts in the fuel cell electrodes for electrochemical conversion of H2 and O2 from air into electricity, heat and water.

Plasma sputtering deposition of supported nanocatalysts has been demonstrated to improve electrode efficiency of low temperature proton exchange membrane fuel cells. Indeed, sputtering can act as an atom source with a controlled energy distribution, which, in turn, enables to control the nanocatalyst growth on the porous carbon electrode with a controlled in-depth profile. This allow to drastically reduce the noble metal content up to a factor 100. Another way is to alloy the noble metal catalyst (here Pt) with a common metal (Fe, Ni, Mo, …) and also with gold. The latter being not a catalyst but is expected to prevent nanocatalyst sintering during fuel cell operation. Very recently, direct growth of Pt alloy nanocatalyst in the plasma phase have been carried out using gas condensation source leading to well defined and narrow nanocluster size distributions.

As the nanoparticle growth by sputtering methods is atomic by nature, simulations at the molecular level are expected to be relevant for understanding basic mechanisms of this deposition method. Indeed, molecular dynamics (MD) as being able to exactly calculating the trajectory of atomic systems is a suitable method for addressing this topic, especially in the context of plasma sputtering. Very recently, it has been shown that MD simulations allowed confirming and predicting the morphology and structure of Pt nanocatalysts as well as for PtxPdyAuz and PtxNiyAuz. Direct growth in the plasma phase mimicking the gas condensation source is also studied. Initial conditions of MD simulations are selected for matching experimental chemical and physical methods. Radial distribution functions and X-Ray Diffraction pattern are systematically computed for enabling direct comparison with experiments.

Dr. A. West

24.05.2018

Solid state chemistry of oxides: some properties and applications
University of Sheffield, Reino Unido
Lugar: Salón de Grados cicCartuja2

The talk will focus on the common occurrence of a variable metal-oxygen ratio in many inorganic oxides and its consequences for a diverse range of electrical properties and applications. Comparisons will be made between the occurrence of non–stoichiometry in many oxides and the exact stoichiometry of molecular compounds. In some cases, oxygen in oxides is more than just an inert O2- packing ion in a crystal structure, but can take part in redox processes similar to transition metal cations. Topics covered in the talk should include: lithium battery cathodes, black rutile, p-n transitions in oxide ceramics and memristive switching phenomena, to illustrate the underlying physical processes responsible for the diverse range of properties. 

Dr. Raúl A. Rica Alarcón

25.04.2018

Levitación de nanopartículas en alto vacío mediante trampas ópticas y de iones
Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada
Lugar: Seminario cicCartuja2

La levitación de nanopartículas en alto vacío ha emergido como un sistema singular que permite explorar distintas fronteras de la física, en particular en física estadística y la aplicabilidad de la mecánica cuántica en la mesoescala [1-4]. En este seminario, daré una introducción a la rica fenomenología observada en este tipo de sistemas, y describiré nuestros progresos en la implementación de distintos tipos de levitación, tales como la levitación óptica y mediante el uso de trampas de iones. Primero presentaré algunos resultados que demuestran un control muy preciso sobre la dinámica no lineal de una nanopartícula atrapada ópticamente, así como de la dinámica estocástica bi-estable que presenta el sistema [5]; a continuación introduciré el uso de trampas de iones como alternativa a las ópticas, permitiendo el atrapamiento estable de nanopartículas con grados internos de libertad tales como nanodiamantes con defectos nitrógeno-vacante [6,7]. Finalmente, veremos cómo es posible controlar la carga de la nanopartícula creando un plasma cerca de la trampa, y discutiremos algunas de las posibilidades que ofrece esta nueva configuración.

 

Fig.1 Imagen de una única nanopartícula atrapada mediante una trampa de Paul y situada en el foco de un haz láser focalizado mediante un objetivo.
La visualización es posible gracias al scattering emitido por la partícula tras su interacción con el haz.

[1] J. Gieseler et al. Phys. Rev. Lett. 109, 103603 (2012)
[2] J. Gieseler et al. Nature Nano. 9, 358-364 (2014)
[3] V. Jain et al. Phys. Rev. Lett. 116, 243601 (2016)
[4] N. Kiesel et al. PNAS 110, 14180-14185 (2013)
[5] F. Ricci et al. Nature Comms. 8, 15141 (2017)
[6] I. Alda et al. Appl. Phys. Lett. 109, 163105 (2016)
[7] G.P. Conangla et al. preprint arXiv:1803.05527 (2018)

Dr. Markus Antonietti

15.03.2018

Nanostructured N-doped Carbon and Carbon nitride materials: Enzyme-like Heterogeneous Catalysts?
Max Planck Institute of Colloids and Interfaces, Research Campus Golm, D-14424 Potsdam, Alemania
Lugar: Salón de Grados cicCartuja2

Carbon nanoparticles and nanostructures which are doped with the element nitrogen (“N-doped”) have special properties, among them high oxidation resistance and high electronic conductivity. These carbon materials can be made by thermal condensation

Of special monomers, among them for instance nucleobases

About 10 years ago, it was found that such carbons are very powerful electrocatalysts, even when metal-free, an can catalyse a number of “world reactions”, such as the reduction of oxygen or the conversion of soda water into formic acid. In addition, the materials are also very favourable supports for metallic nanocatalysts, which is attributed to a bulk heterojunction effect.

When going to even high nitrogen contents, Carbon nitrides or polyheptazinimides are obtained, and the resulting semiconductors can promote artificial photosynthesis, including water splitting and CO2 conversion. I will present a number of completely new chemical reactions only possible with such colloids which indicate how such clusters could have contributed to the existence of chemical diversity, potentially also on a prebiotic earth-like planet.

References:

1) Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry; Wang, Yong; Wang, Xinchen; Antonietti, Markus ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 68-89 (2012)
2) Efficient Metal-Free Oxygen Reduction in Alkaline Medium on High-Surface-Area Mesoporous Nitrogen-Doped Carbons Made from Ionic Liquids and Nucleobases: Yang, Wen; Fellinger, Tim-Patrick; Antonietti, Markus, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 206-209 (2011)

Prof. Derek C. Sinclair

16.06.2017

The influence of non-stoichiometry and chemical doping on the electrical properties of Na1/2Bi1/2TiO3 ceramics
Departamento de Ciencia de Materiales e Ingeniería University of Sheffield, UK
Lugar: Salón de grados cicCartuja2

ABO3-type perovskite oxides exhibit a diverse range of useful functional properties from ferroelectric BaTiO3 materials for dielectric applications in multilayer ceramic capacitors to solid electrolytes and mixed oxide-ion, electronic conducting electrodes for solid oxide fuel cells. The ferroelectric perovskite Na1/2Bi1/2TiO3 (NBT) is known to exhibit interesting and diverse structure-composition-property relationships. A combination of A-site (Na, Bi) disorder, Bi- and Ti- displacements and in-phase and out-of-phase octahedral tilting ensures the crystal chemistry and polymorphism of NBT remain a challenging subject, especially below ca. 520 oC where distortions from the ideal ‘cubic’ cell are reported to occur. Furthermore, the electrical conductivity of undoped NBT materials are known to be critically dependent on low levels of A-site non-stoichiometry.

Here we review the structure-composition-property relationships of NBT materials based on a combination of A-site non-stoichiometry and chemical doping. We use results to show nominally Na-rich or Bi-deficient NBT ceramics to be excellent oxide-ion conductors whereas nominally Na-deficient or Bi-excess NBT ceramics are electrically insulating but retain. This shows undoped NBT ceramics to be mixed ion-electron conducting materials.

Finally, we discuss the differences in the defect chemistry of NBT compared to conventional titanate perovskites, such as (Ba,Sr)TiO3.

 

References

[1] E. Aksel, J.S. Forrester, J.L. Jones, P.A. Thomas, K. Page, and M.R. Suchomel, Appl. Phys. Lett., 98, 152901 (2011);
[2] I. Levin and I.M. Reaney, Adv. Funct. Mater., 22, 3445–3452 (2012);
[3] Y. Hiruma, H. Nagata, and T. Takenaka, J. Appl. Phys., 105, 084112 (2009);
[4] M. Li, M.J. Pietrowski, R.A. De Souza, H. Zhang, I.M. Reaney, S.N. Cook, J.A. Kilner, and D.C. Sinclair, Nat. Mater., 13, 31–35 (2014);
[5] M. Li, H. Zhang, S.N. Cook, L. Li, J.A. Kilner, I.M. Reaney, and D.C. Sinclair, Chem. Mater., 27, 629–634 (2015);
[6] M. Li, L. Li, J. Zang, and D.C. Sinclair, Appl. Phys. Lett., 106, 102904 (2015).

Kostya (Ken) Ostrikov

20.04.2017

Plasma-synergistic effects: catalysing cross-disciplinary collaborations
Queensland University of Technology (QUT) and CSIRO, QUT-CSIRO Joint Sustainable Processes and Devices Laboratory. Australia
Lugar: Salón de Grados cicCartuja2

This presentation will introduce the key features of low-temperature plasmas that make them a versatile tool in materials science and engineering and other areas such as chemical engineering and health sciences. Particular attention will be paid on synergistic effects of plasmas with common materials and processing methods and what difference it makes in diverse applications, with particular focus where nanoscale features of materials play a role. These localized interactions have opened opportunities for fundamental research and applications in the plasma nanoscience field.

The focused “what can plasma do for you” examples will be used to stimulate collaborative efforts even between researchers normally working in completely disparate fields.

Prof. Dr. Bettina V. Lotsch

13.09.2016

2D or not 2D? Two-dimensional nanostructures for sensing and energy conversion
Max Planck Institute for Solid State Research, Stuttgart, Germany
Lugar: Salón de Grados del CicCartuja2

A central paradigm of nanochemistry is the rational synthesis, manipulation and assembly of nanoscale building blocks into hierarchical structures with tailor-made properties. Owing to their chemical diversity and wide scope of physical properties, 2D nanostructures lend themselves particularly well as versatile building blocks in miniaturized devices and for the directed self-assembly of hybrid superlattices with engineered functionalities. Our recent progress in the synthesis and integration of novel 2D bulk and nanosheet materials will be reviewed and their emerging applications in photonic sensing, solar energy conversion and as solid electrolytes will be discussed. 

Dr. Peter Strasser

24.09.2015

Sunlight, free electrons and molecular bonds: Design of catalysts and reactive interfaces for energy storage and conversion
The Electrochemical Energy, Catalysis, and Materials Science Laboratory. Departament of Chemistry, Chemical Engineering Division. Technical University Berlin. Alemania
Lugar: Salón de Actos del CicCartuja | 12.00 h

Catalytic materials are key components of (photo)electrochemical devices and technologies for storing and converting renewable electricity. Their successful development and optimization requires insight into the relation between the atomic-scale chemical structure of the electrified interface and its catalytic activity, selectivity, and stability.
In this talk, we will highlight some of our recent work on the fundamental understanding of electrocatalytic nanomaterials and their liquid-solid interface at the atomic-scale. We will outline the preparation, characterization, and catalytic performance of a number of different nanomaterials and solar fuel reactions and discuss relations between structure, activity, selectivity, and stability. Topics will touch upon the acid and alkaline oxygen electrode(1-17) and the electroreduction of CO2(18-21).

1. P. Strasser, Science, 2015, 349, 379-380.
2. B. H. Han, C. E. Carlton, A. Kongkanand, R. S. Kukreja, B. R. Theobald, L. Gan, R. O'Malley, P. Strasser, F. T. Wagner and Y. Shao-Horn, Energy Environ. Sci., 2015, 8, 258-266.
3. N. R. Sahraie, J. P. Paraknowitsch, C. Göbel, A. Thomas and P. Strasser, J. Am. Chem. Soc., 2014, 136, 14486-14497.
4. L. Gan, C. Cui, M. Heggen, F. Dionigi, S. Rudi and P. Strasser, Science, 2014, 346, 1502-1506.
5. L. Gan, M. Heggen, R. O’Malley, B. Theobald and P. Strasser, Nano Lett., 2013, 13, 1131-1138.
6. C. Cui, L. Gan, M. Heggen, S. Rudi and P. Strasser, Nature Mat., 2013, 12, 765.
7. P. Strasser, S. Koh, T. Anniyev, J. Greeley, K. More, C. F. Yu, Z. C. Liu, S. Kaya, D. Nordlund, H. Ogasawara, M. F. Toney and A. Nilsson, Nature Chem., 2010, 2, 454-460.
8. P. Strasser, Rev. Chem. Eng., 2009, 25, 255-295.
9. R. Srivastava, P. Mani, N. Hahn and P. Strasser, Angewandte Chemie International Edition, 2007, 46, 8988-8991.
10. S. Koh and P. Strasser, J. Am. Chem. Soc., 2007, 129, 12624-12625.
11. H.-S. Oh, H. N. Nong and P. Strasser, Adv. Funct. Mater., 2015, 25, 1074-1081.
12. H. S. Oh, H. N. Nong, T. Reier, M. Gliech and P. Strasser, Chem. Sci., 2015, 6, 3321-3328.
13. H. N. Nong, H. S. Oh, T. Reier, E. Willinger, M. G. Willinger, V. Petkov, D. Teschner and P. Strasser, Angew. Chem., 2015, 54, 2975-2979.
14. T. Reier, D. Teschner, T. Lunkenbein, A. Bergmann, S. Selve, R. Kraehnert, R. Schlögl and P. Strasser, J. Electrochem. Soc., 2014, 161, F876-F882.
15. H. N. Nong, L. Gan, E. Willinger, D. Teschner and P. Strasser, Chem. Sci., 2014, 5, 2955-2963.
16. A. Bergmann, I. Zaharieva, H. Dau and P. Strasser, Energy Environ. Sci., 2013, 6, 2745-2755.
17. H. Dau, C. Limberg, T. Reier, M. Risch, S. Roggan and P. Strasser, Chemcatchem, 2010, 2, 724-761.
18. A. S. Varela, N. Ranjbar, J. Steinberg, W. Ju, H.-S. Oh and P. Strasser, Angewandte Chemie - International Edition, 2015, online DOI: 10.1002/anie.201502099.
19. R. Reske, H. Mistry, F. Behafarid, B. Roldan Cuenya and P. Strasser, J. Am. Chem. Soc., 2014, 136, 6978-6986.
20. H. Mistry, R. Reske, Z. Zeng, Z.-J. Zhao, J. Greeley, P. Strasser and B. Roldan Cuenya, J. Am. Chem. Soc., 2014, 136, 16473-16476.
21. Ana Sofia Varela, Matthias Kroschel, Tobias Reier and P. Strasser, Catal. Today, 2015, doi:10.1016/j.cattod.2015.1006.1009.

Prof. Lorenzo Pavesi

28.05.2015

Silicon nanocrystals as enabler for silicon photonics
Universidad de Trento (Italia)
Lugar: Salón de Actos del CicCartuja | 12.00 h

Low dimensional silicon nanocrystals (Si-nc) have interesting optical properties which enables different applications. On one side quantum confinement effects turn silicon into a luminescent material where luminescence can be also excited by electrical injection. On the other side, small sizes, large surfaces and dielectric mismatch between the core and the surrounding matrix increase dramatically the nonlinear optical coefficients.

In this talk I will review our recent work on Si-Nc and their applications:

- The growth and physics of Si-nc [Silicon Nanocrystals; Fundamentals, Synthesis and Applications (Wiley-VCH 2010)]

- The development of high efficiency solar cells with Si-nc downshifting layer [Solar Energy Materials and Solar Cells 132, 267 (2015)]

-The development of bipolar light emitting diodes [Journal of Applied Physics 111, 063102 (2012) Applied Physics Letters (2015);]

- The use of silicon nanocrystals light emitting diode as entropy source for quantum random number generation, the key device for cryptography [Journal of Ligthwave Technology (2015)];

- The use of silicon nanocrystals as nonlinear material in bistable optical cavities, in waveguide optical mode monitors which are based on two photon excited luminescence detection, in wavelength shifter by sum-frequency generation [Optics Letters 38, 3562 (2013); Applied Physics Letters 106, 071109 (2015).].

Dr. Luis M. Liz-Marzán

07.05.2015

Prospects for Plasmonic Nanomaterials
Bionanoplasmonics Laboratory, CIC biomaGUNE
Lugar: Salón de Actos del CicCartuja | 11.00 h

Metal nanoparticles display very interesting optical properties, related to localized surface plasmon resonances (LSPR), which give rise to well-defined absorption and scattering peaks in the visible and near-IR spectral range. Such resonances can be tuned through the size and shape of the nanoparticles, but are also extremely sensitive towards dielectric changes in the near proximity of the particles surface. Therefore, metal nanoparticles have been proposed as ideal candidates for biosensing applications. Additionally, surface plasmon resonances are characterized by large electric fields at the surface, which are responsible for the so-called surface enhanced Raman scattering (SERS) effect, which has rendered Raman spectroscopy a powerful analytical technique that allows ultrasensitive chemical or biochemical analysis, since the Raman scattering cross sections can be enhanced up to 10 orders of magnitude, so that very small amounts of analyte can be detected. This seminar will focus on recent developments and future prospects within the various areas involved in the development and application of plasmonic nanomaterials, from nanoparticle synthesis and assembly, through optical modeling, to the design of engineered substrates for sensing and diagnostics.  

Dr. Timmy Ramírez-Cuesta

02.05.2013

Espectroscopía de Neutrones, aplicaciones en Química, Ciencia de Materiales y Catálisis
ISIS Facility, STFC, Rutherford Appleton Laboratories, UK
Lugar: Sala Rotonda CicCartuja | 12.00 h

Las técnicas de neutrones son muy útiles en el estudio de la dinámica de los átomos y moléculas de hidrogeno. La naturaleza de la interacción entre el neutrón y átomo es responsable de la gran sección eficaz del núcleo del átomo de hidrogeno. En particular, el neutrón inspecciona simultáneamente la estructura y dinámica de los átomos del solido, en ambos casos la conexión entre los cálculos dinámicos utilizando métodos de DFT se corresponden rigurosamente con los espectros inelásticos dado que el neutrón interactúa directamente con el núcleo atómico, a diferencia del caso de las espectroscopias ópticas donde la dinámica del núcleo es determinada indirectamente a través de la interacción del fotón con la nube electrónica.
Otra característica muy importante de la interacción del neutrón es que es una prueba muy penetrante, por ejemplo, casi todos los metales poseen secciones eficaces muy pequeñas. Esto permite hacer experimentos utilizando contenedores de muestras de acero, aluminio etc., sin necesidad de tener ventanas ópticas, en consecuencia el uso de gases para dosificar solidos porosos, catalizadores y otros es trivial.
En esta charla se presentaran los aspectos básicos de la espectroscopia inelástica de neutrones y el uso de DFT para interpretar los experimentos como así también algunos ejemplos de aplicaciones al estudio de materiales solidos, gases adsorbidos en matrices porosas ( hidrogeno, captura de CO2, separación de etileno y acetileno entre otros)

Prof. Dr. Anton Lerf

19.03.2012

Intercalation of Hydrated Fe2+ and Fe3+ in the Vermiculites from Santa Olalla and Ojén. A Mössbauer spectroscopic investigation
Walther-Meißner-Institut der Bayerischen Akademie der Wissenschaften Walther-Meißner-Straße 8 85748 Garching
Lugar: Seminario de la primera planta del CicCartuja | 12.30 h

Intercalation of hydrated Fe²⁺ and Fe³⁺ ions in phyllosilicates is of interest for different fields of research, e.g. soil science, nutrition of plants, catalysis. However, the nature of intercalated species is not really clear up to now. We carried out Mössbauer investigation of Fe-intercalated vermiculites from Santa Olalla and Ojén. In case of the Fe^3* intercalated vermiculites it is not possible to get intercalation without simultaneous deposition of iron oxyhydroxides on the external surface of the vermiculites. The intercalation of Fe²⁺ is much easier. This intercalated iron is highly mobile at room temperature. In addition, the Mössbauer data can be explained only if one assumes internal redox processes between intercalated and structural iron ions. Even in case of the Fe³⁺ intercalated vermiculites one can observe internal redox reactions.

José Ángel Martín Gago

31.03.2011

Reacciones de Moleculas Orgánicas y Biomoleculas sobre Superficies de Monocristales
Instituto de Ciencia de Materiales de Madrid (CSIC)
Lugar: Seminario de la primera planta del CicCartuja | 12.00 h

Los procesos de auto-ensamblado y auto-organización de moléculas orgánicas sobre superficies son algunas de las principales estrategias que han permitido a la vida desarrollarse a partir de sus componentes moleculares (building blocks) y que han inspirado las nuevas tendencias de fabricación de dispositivos en lo que se ha llamado aproximación bottom-up. La estructura que adquieren las capas moleculares sobre superficies es fundamental para determinar muchas de sus posibles aplicaciones. Por tanto, técnicas de caracterización de superficies como XPS, LEED o DFT, y en especial STM que presentan una alta sensibilidad, nos proporcionan información sobre interacción química, estructura y propiedades electrónicas de las capas moleculares ensambladas. En esta presentación se describirán varios tipos de sistemas moleculares y se clasificarán por el grado de interacción que mantienen sobre el substrato, describiendo cuales son los mecanismos responsables de la estructura final. Las capas de PTCDA sobre Au(111) son un ejemplo de sistema muy poco interaccionante, que puede modificarse por la inclusión de átomos de Fe en la estructura. En el otro extremo, veremos sistemas basados en la interacción S-metal, como los alcanotioles, que presentan numerosas aplicaciones tecnológicas si se modifica el grupo funcional. Así veremos la estructura de capas de DNA, PNA o cisteina sobre diferentes substratos. Con respecto al DNA o PNA podremos relacionar la estructura molecular con parámetros tecnológicos como la eficiencia del biosensor.
Por último nos centraremos en describir como estos substratos pueden además ser utilizados para catalizar reacciones y formar nuevas moléculas, como fullerenos a partir de sus precursores moleculares, abriendo las puertas a un campo nuevo que permite la obtención de nuevas moléculas.