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Seminarios y Conferencias

Prof. Derek C. Sinclair

16 Junio

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).



Prof. Luisa De Cola

18 Mayo

Luminescent assemblies, imaging and cellular lasing
Institute de Science et d'Ingénierie Supramoléculaires (I.S.I.S.), Université de Strasbourg and KIT, Germany
Lugar: Salón de grados cicCartuja2

Luminescent molecules that can undergo self-assembly are of great interest for the development of new materials, sensors, biolabels…. The talk will illustrate some of the recent results on soft structures based on metal complexes able to aggregate in fibers, gels and soft mechanochromic materials [1].  The use of platinum complexes as building block for luminescent reversible piezochromic and mechanochromic materials, down to the nanoscale, will be illustrated [2]. The emission of the compounds can be tuned by an appropriate choice of the coordinated ligands as well as of their aggregation in different structures. The formation of soft assemblies allows the tuning of the emission color, by pressure and temperature leading to a new class of materials possessing reversible properties. We demonstrate how even small changes in molecular design can completely inhibit or enhance the formation of organized supramolecular architectures, leading to a deep understanding of the key factor affecting the whole self-assembly process.

The monitoring of the different emission properties, used as fingerprint for each of the assembled species, allowed an unprecedented real-time visualization of the evolving self-assemblies [3].

In the final part of the talk a new concept, mirrorless cellular lasing, i.e. to generation of strong laser action from stained biological cells and, importantly, in absence of any external resonators is described. Interestingly, such phenomenon is connected to the biological components that constitute the structure of the cells involved in laser generation [4].

 

References

[1] C. A. Strassert, L. De Cola et al. Angew. Chem. Int. Ed., 2011, 50, 946; M. Mauro, L. De Cola et al. Chem. Commun. 2014, 50, 7269
[2] D. Genovese, L. De Cola et al. Adv. Funct. Mater., 2016, 26, 5271–5278
[3] A. Aliprandi, M. Mauro, L. De Cola Nature Chemistry , 2016, 8, 10-15
[4] D. Genovese, V. Barna, L. De Cola submitted



Kostya (Ken) Ostrikov

20 Abril

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.



Dr. Cuong Pham-Huu

16 Marzo

Materials for catalysis: challenges and opportunities
Institute of Chemistry and Processes for Energy, Environment and Health (ICPEES, UMR 7515) CNRS and University of Strasbourg, France
Lugar: Salón de Grados CicCartuja2

New catalytic materials have been extensively developed since the last decades for application in several research fields including sensors, drug delivery, light-weight high mechanical strength composites and catalysis. In this presentation, we will discuss about last developments on the use of (i) confinement effect in 1D carbon channel, (ii) nanostructuration of 2D carbon via catalytic patterning along with the uncovering of the patterning mechanism by operand transmission electron microscopy, and (iii) development of new bio-sourced mesoporous carbon doped with nitrogen as an active and selective metal-free catalyst for oxidation process. The first example reports on the use of confinement effect to modify and selectively cast, metal oxides, inside 1D carbon material for applications in the field of drug delivery, biological imaging and catalysis. In the second example, catalysis has been used to perform nanopatterning of few-layer graphene, leading to the generation of higher reactive edge sites, for the subsequence anchorage of metal oxide nanoparticles with improved sintering resistance for application in the field of sensor and liquid-phase reactions. The direct analysis of the process by operando TEM at ambient conditions allows one to uncover the different mechanisms operated during the patterning process for future optimization step. The last example focus on the synthesis of nitrogen-doped mesoporous carbon, issued from bio-sourced raw materials, decorated silicon carbide as metal-free catalyst for the selective oxidation of trace amount of H2S into elemental sulfur with improved activity and stability. The presentation will end-up with some future perspectives about the use of carbon-based metal-free catalysts in some relevant catalytic processes as well as the role of operando TEM investigation for unraveling catalytic mechanisms.



Prof. Dr. Anders Hagfeld

16 Febrero

The Versatility of Mesoscopic Solar Cells
Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015, Lausanne, Switzerland
Lugar: Salón de Grados CicCartuja2

In our work on solid-state dye-sensitized solar cells (ssDSSC) we have recently [1] shown that copper phenanthroline complexes can act as an efficient hole transporting material. We prepared ssDSCs with the organic dye LEG4 and copper(I/II)-phenantroline as redox system and achieved power conversion efficiencies of more than 11%. Our follow up work on electron transfer studies and device optimization will be presented at the meeting.

In our work on perovskite solar cells (PSC) we have achieved efficiencies above 20% with a mixed composition of iodide/bromide and methyl ammonium/formamidinium [2]. For cells larger than 1 cm2 we recently certified a record efficiency of 19.6% [3], replacing the anti-solvent step in the perovskite film formation with a vacuum flash treatment. With the use of SnO2 compact underlayers as electron acceptor contacts we have constructed planar perovskite solar cells with a hysteresis free efficiency above 20% [4]. Recently, we have taken the cation mixing of the perovskite film further by including the Cs+ in a so-called ‘triple cation’ composition, i.e. Cs/FA/Ma. Larger grains grown in a monolithic manner are observed and for example reproducibility and device stability are improved [5]. At the meeting we will discuss our follow up works [6] and present our champion data; up to 22% efficiency with an external electroluminescence of 4%, and an outstanding open-circuit voltage of 1.24 V at a band gap of 1.63 eV entailing one of the smallest loss-in-potential of 0.39 V ever measured for any solar cell material. Furthermore, we will report a breakthrough in stability at 85 oC for 500 h under full solar illumination and maximum power point tracking (during which 95% of the initial performance was retained).

 

References

[1]   Freitag et al., Energy & Envir. Sci., DOI: 10.1039/C5EE1204J
[2]   Bi et al., Science Advance, DOI: 10.1126/sciadv.1501170
[3]   X. Li et al., Science, DOI:10.1126/science.aaf8060
[4]   Correa et al., Energy & Envir. Sci., DOI:10.1039/C5EE02608C
[5]   M. Saliba et al., Energy & Envir. Sci., 2016, DOI: 10.1039/C5EE03874J
[6]   M. Saliba et al., Science 10.1126/science.aah5557 (2016)



Prof. Dr. Oliver Gröning

18 Noviembre

On-surface synthesis and properties characterization of novel low-dimensional materials
Empa, Swiss Federal Laboratories for Materials Testing and Research
Lugar: Salón de Grados CicCartuja2

In recent years on-surface chemical synthesis routes have succeeded in producing atomically precise nanostructures, whose synthesis cannot be achieved by standard wet chemical processes. This circumstance is due to a great extend to the usually insoluble nature of the products. In this respect, particular attention has been devoted to graphene derived carbon nanostructures such as graphene nanoribbons (GNR) and regular 2D carbon networks[1,2]. In our presentation we will review the recent developments in the field of on-surface chemical synthesis with a particular emphasis on the importance UHV-analytical and computational tools in understanding the physicochemical processes involved in the synthesis and in assessing the electronic properties of the produced nanostructures. The first part of the presentation will mainly touch the role of specific molecular precursors for the synthesis of graphene derived 2D and 1D nanostructures. We will discuss the electronic properties of these novel nanomaterials and their prospects to be used in future electronic devices.

In the second part the question, how the chemical synthesis can be guided by specific atomic surface structures will be addressed. In this context, we will turn our attention to the PdGa compound, which has been found to combine high selectivity and activity in acetylene semi-hydrogenation [3]. We will discuss the non-trivial atomic structure of the (111) and (-1-1-1) PdGa surface, which differ significantly in the local structure of the top most Pd atoms and therefore are model surfaces to study active site isolation and ensemble effects on catalyst selectivity [4]. We will then explore the possibilities of chiral selective adsorption and synthesis on these surfaces made possible by the intrinsic chiral nature of the P213 space group PdGa belongs to [5]. We show that the intrinsically chiral surfaces of PdGa can induce 99% chiral adsorption selectivity of prochiral 9-Ethynylphenantrene (9-EP) at room temperature. Similarly high chiral selectivity can be achieved in producing prochiral 9-EP trimers, which shows the potential of achieving highly asymmetric chemical synthesis on a high temperature stable metallic catalyst.       

[1] J. Cai, et al.,Nature 466, 470 (2010)
[2] M. Bieri, et al., JACS 132 16669, (2010)
[3] M. Armbrüster, M. Kovnir, M. Behrens, D. Teschner, Y Grin, and R. Schlögl, JACS 132, 14745 (2010)



Prof. Dr. Bettina V. Lotsch

13 Septiembre

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. 



Prof. Dr. Claes-Göran Granqvist

21 Abril

Electrochromics and thermochromics: Towards a new paradigm for energy efficient buildings
Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweden
Lugar: Salón de Actos del CicCartuja | 12.00 h

About forty per cent of the World’s primary energy is used for heating, cooling, lighting and ventilating buildings. New nanotechnologies are able to decrease the use of energy significantly at the same time as the comfort and amenities of the building are improved. This talk surveys a number of options, mostly based on work in the speaker’s laboratory. Foci lie on windows and glass facades with electrochromic and thermochromic properties. Functional principles, thin film preparation and properties, new plasmonic nanomaterials, and technological prospects are discussed. 



Prof. Dr. Markus Niederberger

18 Febrero

Nanoparticles as Building Blocks for Multicomponent Materials and Films
Laboratory for Multifunctional Materials, ETH Zurich, Switzerland
Lugar: Salón de Actos del CicCartuja | 11.00 h

Nanostructures including nanoparticles, nanowires and nanosheets are the ideal building blocks for the bottom-up fabrication of functional materials. They offer an immense variety of interesting properties, which not only depend on the composition, but also on the crystal structure, the particle size and shape and on the surface chemistry. Accordingly, potential synthesis routes have to provide full control over all these parameters. In addition, for most applications the nanoparticles have to be assembled and processed into useful geometries, including 2-dimensional arrangements like films or 3-dimensional bodies like composites, foams or aerogels. The talk will give a short introduction to the synthesis of metal oxide nanoparticles by nonaqueous sol-gel chemistry, and it will briefly discuss the underlying chemical mechanisms leading to nanoparticle formation. Moreover, several examples will be shown, how the nanoparticles can be processed into films and nanostructured bulk materials for specific applications in gas sensing, dye adsorption, or energy storage and conversion. 



Prof. Javier Pérez-Ramírez

12 Noviembre

Design of Hierarchically Organized Zeolite Catalysts
Institute of Chemical and Bioengineering ETH Zurich, Switzerland
Lugar: Salón de Actos del CABIMER | 12.00 h

This lecture overviews recent progress towards the design of hierarchically-structured zeolites for application in catalysis. I will illustrate the benefits attained due to the improved access and molecular transport in zeolite crystals with auxiliary pore networks, emphasizing recent advances that contribute to the integral design of these materials for established and new catalytic processes. This includes preparative aspects by strategic post-synthetic modifications, the development of advanced characterization tools to assess descriptors, and the transition from laboratory practices with powders to the multi-ton scale up and structuring of the hierarchical zeolites into technical form. Current needs and future directions will be discussed.

1. J. Pérez-Ramírez, Nature Chem. 2012, 4, 250.
2. S. Mitchell, N.-L. Michels, K. Kunze, J. Pérez-Ramírez, Nat. Chem. 2012, 4, 825.
3. S. Mitchell, N.-L. Michels, J. Pérez-Ramírez, Chem. Soc. Rev. 2013, 42, 6094.
4. M. Milina, S. Mitchell, N.-L. Michels, J. Kenvin, J. Pérez-Ramírez, J. Catal. 2013, 308, 398.
5. L. Gueudré, M. Milina, S. Mitchell, J. Pérez-Ramírez, Adv. Funct. Mater. 2014, 24, 209.
6. T. C. Keller, S. Isabettini, D. Verboekend, E. G. Rodrigues, J. Pérez-Ramírez, Chem. Sci. 2014, 5, 677.
7. M. Milina, S. Mitchell, P. Crivelli, D. Cooke, J. Pérez-Ramírez, Nat. Commun. 2014, 5:3922, DOI: 10.1038/ncomms4922
8. N.-L. Michels, S. Mitchell, J. Pérez-Ramírez, ACS Catal. 2014, 4, 2409.
9. M. Milina, S. Mitchell, P. Crivelli, D. Cooke, J. Pérez-Ramírez, Angew. Chem. Int. Ed. 2015, 54, 1591.
10. M. Morales, P.Y. Dapsens, I. Giovinazzo, J. Witte, C. Mondelli, S. Papadokonstantakis, K. Hungerbühler, J. Pérez-Ramírez, Energy Environ. Sci. 2015, 8, 558



Dr. Peter Strasser

24 Septiembre

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. Dr. Rony Snyders

15 Julio

Plasma polymerization (diagnostic + growth mechanism)
Head of the research laboratory ChIPS (Chimie des Interactions Plasma-Surface)
Lugar: Sala de Reuniones del CicCartuja2 | 15.00 h

In the framework of our activities in the field of plasma polymerization, we are interested in contributing towards a better understanding of the growth mechanism of the plasma polymer films which is of tremendous importance for a better control of the material properties. To reach this goal, our systematic strategy is based on a multidisciplinary approach combining plasma diagnostic and thin film characterization. The latter is mainly achieved through XPS measurements most of the time combined with chemical derivatization methods as well as ToF-SIMS measurements. On the other hand, the plasma chemistry is investigated by using Mass Spectrometry and FTIR spectroscopy. For both methods, the data are evaluated using an original approach using DFT calculations. We have recently shown that this approach allows to significantly improve the understanding of the different reactions pathways encountered by the precursor. In the future, based on our recent achievements in clarifying the growth mechanism of several families of plasma polymers, our objective is to go one step further by investigating the chemical reactivity of film-forming species towards the growing film. In addition, in order to get a more complete picture of the mechanisms, strong efforts will be devoted to characterize the electrons as well as the ions by dedicated diagnostic methods.



Prof. Lorenzo Pavesi

28 Mayo

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 Mayo

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. George Palasantzas

12 Junio

Casimir force between real materials for device applications
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, The Netherlands
Lugar: Seminario del CicCartuja | 11.00 h

Using the measured optical response and surface roughness topography as inputs, we perform realistic calculations of the influence of Casimir forces on the actuation dynamics of micro/nanoelectromechanical systems (MEMS/NEMS). Amorphous to crystalline phase transitions in phase change materials can have strong influence on the actuation of microelectromechanical systems under the influence of Casimir forces. Indeed, the phase portraits of the actuation dynamics show strong sensitivity to changes of the Casimir force as the stiffness of the actuating component decreases and/or the effective interaction area of the Casimir force increases, which can also lead to stiction. Introduction, however, of intrinsic energy dissipation (associated with a finite quality factor of the actuating system) can prevent stiction by driving the system to attenuated motion towards stable equilibrium. It is also found that even though surface roughness appears to have a detrimental effect on the availability of stable equilibria, it ensures that those equilibria can be reached more easily than in the case of flat surfaces. Hence our findings play a principal role for the stability of micro/nanodevices and architectures operating at distances below 200 nm. Finally, new investigations for the Casimir force from conductive SiC and their implications for MEMS/NEMS will also be discussed.



Prof. Richard Partch

26 Septiembre

Enhancing Particle Applications by Surface Modification
Chemistry Center for Advanced Materials Processing Clarkson University
Lugar: Salón de Actos del CicCartuja

Gas, aerosol and liquid dispersion methods for particle synthesis and surface modification carried out by the speaker´s research group at Clarkson University will be presented. Briefly discussed will be colloids having a wide variety compositions, shapes and sizes useful for : 1) metal matrix and rubber composites, 2) protecting cores from acidic and humid environments, 3) improving print toner charging and reducing energy use by copy machines and fluorescent lights, 4) reducing polishing defects in microelectronic processing, 5) medical imaging, treatment of chemical overdoses and cancer and artificial organs and 6) security.



Dr. Timmy Ramírez-Cuesta

02 Mayo

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)



Dra. Sol Carretero-Palacios

29 Enero

Plasmons in metallic hole arrays and nanoparticles in an optical trap
Photonics and Optoelectronics Group. Faculty of Physics and Center for Nanoscience (CeNS). Ludwing-Maximilians-Universität München
Lugar: Seminario de la primera planta del CicCartuja | 12.00 h

Subwavelength apertures periodically arranged in a metal film may transmit electromagnetic waves beyond the cutoff wavelength of the holes, with a much higher intensity than if they were isolated. It has been established that resonant excitation of surface plasmons creates huge electric fields at the metallic surface, forcing light through the holes and giving very high transmission coefficients. This is the so-called Extraordinary Optical Transmission.
I will present a detailed theoretical study of the physical mechanisms controlling the transmission process in a Bull’s Eye Geometry (a single subwavelength circular hole surrounded by concentric annular grooves).
I will also show final results for other systems containing annular holes, such us arrays of annular dimples (of finite thickness) designed for detection in the terahertz regime, and a description for resonances appearing at unusual wavelengths beyond the cutoff of the holes. Also the nonlinear optical response in arrays of subwavelength slits in combination with nonlinear Kerr-type dielectrics will be shown.
Finally, I will describe the Dark Field Microscopy technique and present some of its applications for manipulating micro- and nano-particles (metallic, dielectric, and hybrid ones).



Dr. Xavier Le Guebel

08 Noviembre

Fluorescent noble metal nanoclusters for biomedical applications
Centro Andaluz de Nanomedicina y Biotecnología
Lugar: Seminario de la primera planta del CicCartuja | 12.30 h

Noble metal nanoclusters(NCs) received much attention in the last five years due to their photophysical properties and their applications in nanomedicine. Several groups have studied the origin of the fluorescence of NCs and their structure–property inside different cavities such as polymers [2], dendrimer [3] and proteins [4]. Few-atom nanoclusters differ from gold or silver nanoparticles in that they can be highly fluorescent, do not support a surface plasmon, and do not have the metallic and bulk-like properties of nanoparticles/nanocomposites [5]. This fluorescence is likely due to the transition of molecule-like electronic levels when subnanometer sizes are smaller than the Fermi wavelength (i.e. < 1 nm). Noble metal (Ag, Au, Pt) NCs were prepared in wet chemistry in biological templates: proteins (Bovine Serum Albumin, human Transferrin), peptide (Glutathione) and DNA, which act as reducing agent and stabilizer. Structural investigations indicate a covalent binding between the metal cluster to the template and confirm the role of the nature of the ligand to the optical properties of the metal nanoclusters. Photophysical studies suggest a relative high quantum yield, strong photostability, long lifetime with a fluorescence emission tunable in the visible range. Moreover, cytotoxicity and life experiments in cells and with mice highlight the potential of this new type of “non-toxic” fluorescent labels for imaging and targeting. 

[1] C. D. Geddes, J. R. Lakowicz1, Journal of Fluorescence 12 (2002) : 121.
[2] H. W. Duan, S. M. Nie, Journal of the American Chemical Society 129 (2007) : 2412.
[3] J. Zheng, J. T. Petty, R. M. Dickson, Journal of the American Chemical Society 125 (2003) : 7780.
[4] X. Le Guevel, N. Daum,M. Schneider, Nanotechnology 22 (2011) 275103 (7pp).
[5] J. Zheng, P. R. Nicovich, R. M. Dickson, Annual Review of Physical Chemistry 58 (2007) : 409.



Prof. Dr. Anton Lerf

19 Marzo

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 Fe3* 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.



Prof. Jiří Málek

13 Julio

Structural Relaxation in Glasses and Supercooled Liquids
Department of Physical Chemistry, University of Pardubice, Czech republic
Lugar: Seminario de la primera planta del CicCartuja | 12.00 h

Structural relaxation strongly affects physical properties of non-crystalline materials. Different types of structural relaxation and measurement techniques are described. The link between relaxation behavior, viscous flow and crystal growth in highly supercooled liquids is discussed. Volume and enthalpy relaxation is interpreted within a phenomenological model that allows quantitative description and thermal treatment tailoring for effective and long term use of non-crystalline materials. Some general features of structural relaxation common to many different and chemically dissimilar glass-forming systems ranging from polymers to oxides, chalcogenides and metallic glasses are discussed.



José Ángel Martín Gago

31 Marzo

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.



Prof. Josef Breu

27 Marzo

Novel Materials Based on Modified and Synthetic Clays
Lehrstuhl für Anorganische Chemie I, Universität Bayreuth
Lugar: Seminario de la primera planta del CicCartuja | 12.00 h

The combination of platy morphology and high intracrystalline reactivity paves the way for a broad range of possible applications for layered silicates that extends far beyond the well established adsorptive and rheological materials. In particular, synthetic layered silicates are well suited to fabricate for instance microporous hybrid materials and polymer layered silicate nanocomposites with superior gas barrier, flame retardancy, and mechanical properties.



Dr. Lluís Marçal

24 Marzo

Template-assisted fabrication and characterization of polymer nanopillar arrays for optoelectronic applications
Catedrático de la Universidad Rovira i Virgili, Tarragona Departamento de Ingeniería Electrónica, Eléctrica y Automática
Lugar: Seminario de la primera planta del CicCartuja | 12.00 h

Recently, photoluminescent conducting polymeric micro- and nanostructures have received a considerable attention because of their interesting optoelectronic properties and potential applications such as sensors, polymer light-emitting diodes, polymer solar cells, etc. Different synthesis methods have been proposed for the fabrication of polymer nanostructures: template-assisted, nanoimprinting, nanolithography and electro-spinning. Among them, template-assisted is an easy, low cost, and highly versatile method to fabricate nanostructures for a variety of materials: polymers, metals, inorganics, semiconductors and their multi-functional composites. This method entails microporous or nanoporous materials used as templates. The synthesized nanostructure is achieved by infiltration of the material within the pores of the template. After deposition, the template can be selectively removed either partially or completely to produce a nanostructure array or freestanding nanostructures. In addition, template-assisted techniques possess the advantage of being able to readily create large-area, ordered nanostructures and, in some cases, vertically aligned structures having high aspect ratios.
Anodized aluminium oxide (AAO) has become one of the most common nano-templates for the preparation of different nanometer-sized structures attractive because of its simple and highly controllable fabrication method. Dimensions as well as geometry of the nanostructures such as pore diameter and interpore distance can be controlled by selecting appropriate anodization conditions.
We present the fabrication and characterization of photoluminescent conducting polymer nanopillar arrays via template-assisted method. Different type of polymer nanopillar arrays were fabricated. The resulting polymer nanostructures are analyzed in detail by ESEM (environmental scanning electron microscopy) and AFM (atomic force microscopy) images. The effect of the nano-confinement on the electrical and optical properties is analyzed by current sensing atomic force microscopy (CS-AFM), photoluminescence and UV-Visible spectroscopy. In addition, the orientation of the polymer chains inside the nanopillar is also characterized by Raman spectroscopy and X-ray diffraction (µXRD). The results are discussed and compared with polymer thin films.