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Seminarios y Eventos

Seminars and Events

Jornadas Jvenes Investigadores

Coordinadores: Iigo Bretos y Lidia Martnez

09 March 2020, 12:00 h. Saln de Actos

High-Speed Bimodal AFM nanomechanical mapping of collagen self-assembly

Vctor Garca Gisbert

Collagen is the most abundant structural protein of the extracellular matrix. The assembly of collagen fibrils play relevant roles in a variety biological processes. The formation fibrils during the self-assembly process of collagen I have been studied by AFM [1,2]. Those studies lacked the time and mechanical properties resolution to clarify the mechanism of the earlier stages of collagen assembly and fibril structure formation. We have developed a high-speed bimodal AFM that combines the ms time resolution of high-speed AFM [3] with the nanomechanical force sensitivity of bimodal AFM [4,5]. High-speed bimodal AFM characterizes the earliest stages of the self-assembly of the collagen fibrils by proving time-resolved and high-spatial resolution maps of the evolution of the elasticity of the fibrils during the growth.

[1] F. Jiang, H. Hrber, J. Howard, D.J. Mller., J. Struct. Biol. 148, 268278 (2004).
[2] D.R. Stamov, E. Stock, C.M. Franz, T. Jhnke, H. Haschke, Ultramicroscopy 149, 8694 (2015).
[3] T. Ando. Nanotechnology 23, 062001 ( 2012)
[4] S. Benaglia, V.G. Gisbert, A.P. Perrino, C.A. Amo, R. Garcia, Nat. Protoc. 13, 2890 (2018)
[5] E.T. Herruzo, A.P. Perrino, R. Garcia, Nat. Commun. 5, 3126 (2014).

24 February 2020, 12:00 h. Saln de Actos

2D-based materials for bio-sensing and optolectronics

Sandra Cortijo Campos

Different approaches for 2D-based specific-sensors are being developed towards applications for detection of ultra-thin materials and health relevant molecules such as biomarkers. One approach is based on the covalent functionalization of graphene by adding carboxylic acid groups which allow successive binding with biologically active molecules for specific antigen sensing. We present a new method for in-situ specific functionalization of graphene that provides highly conductive cm-sized single-layer COOH-graphene. Anchoring of the biomolecules is demonstrated through fluorescence images of the marked antibody. We have also designed a new amplification platform based on silica membranes where graphene is the support of the molecules to be detected by interference enhanced Raman scattering (IERS). We present another selective bio-sensor based on the modifications in the photoluminescence characteristics of MoS2 single-layers grown by CVD that occurs when a mRNA probe, anchored to the MoS2 flakes, is bonded to its complementary mRNA. On the other hand, the synthesis of large area single-layer transition metal dichalcogenides (TMDC) by CVD is very relevant for the implementations in real devices of these extremely promising materials. Our main objective in this area is the controlled doping of 2D-TMDC with magnetic transition metals and with rare earths for applications in spintronics and optolectronics, for example for single photon emission and detection. In this context, we have designed and installed a low pressure CVD system that allows different approaches for 2D MoS2 growth as well as its doping.

24 February 2020, 12:30 h. Saln de Actos

Optoelectronics devices based on
two-dimensional materials

Dr. Riccardo Frisenda

Two-dimensional (2D) materials, which are based on layered van der Waals crystals, provide a unique opportunity for electronic and optoelectronic devices. In particular, semiconducting 2D materials, such as molybdenite or indium selenide, possess interesting properties that are related to their reduced dimensions. For example, the presence of sizeable and thickness-dependent bandgap and the strong light-matter interaction can be exploited for light‐emitting and light‐sensing purposes in nanoscale devices. Moreover, different 2D materials can be easily combined into van der Waals heterostructures, without the typical interfacial lattice-matching constraints encountered in epitaxial growth of conventional heterostructures. In this presentation I will discuss the fabrication and the properties of different devices based on 2D materials and their heterostructures.

14 January 2020, 12:00 h. Saln de Actos

Time-resolved measurements of domain wall velocity in amorphous magnetic microwires

Esther Calle Ramrez
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

The dynamic process of nucleation, propagation and braking of a single domain wall (DW) has been systematically determined in a Fe-based magnetostrictive microwire under the action of an axial magnetic field. While in previous reports the Sixtus-Tonks experiments have provided partial information on the process (i.e., the average velocity), in the present study we report on the instantaneous processes involved in the propagation of the DW, as well as the transient process during the DW depinning. The experimental measurements were carried out using the spontaneous Matteucci effect induced during DW propagation due to the small helical magnetization component created during the fabrication process.

14 January 2020, 12:30 h. Saln de Actos

Magnetic materials with perpendicular magnetic anisotropy (PMA): Different easy ways to control them

Dr. David Navas Otero
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

Since the middle of the 1970s, when Iwasaki et al. proposed perpendicular magnetic recording (PMR) as an alternative to conventional longitudinal magnetic recording [1], thin films with perpendicular magnetic anisotropy (PMA) have been widely studied for recording media applications as well as for patterned magnetic media [2]. Magnetic films with PMA patterned into stripes and lines [3] have been also proposed for nanoscale spintronic devices such as those based on current-driven domain wall motion. Recently, the possibility to use ultrathin films with PMA has opened the path towards the development of skyrmionic devices [4]. Moreover, synthetic antiferromagnets, based on materials with PMA, have been also suggested for biologimedical applications [5].
In this seminar, we will discuss different alternatives to prepare and control nanostructured material with PMA, such as CoCrPt and CoFeB alloys, as well as the study of their related magnetic behaviours.

1. S. Iwasaki, and Y. Nakamura, IEEE Trans. Magn. 14, 436 (1978).
2. S.N. Piramanayagam and K. Srinivasan, J. Magn. Magn. Mater. 321, 485 (2009).
3. S. Emori et al., Nature Materials 12, 611 (2013).
4. A. Fert et al., Nanotechnology 8, 152 (2013).
5. T. Vemulkar et al., Applied Physics Letters 107, 012403 (2015).

18 December 2019, 12:00 h. Saln de Actos

Spin-orbital interplay in iron superconductors

Raquel Fernndez Martn
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

Superconductivity was discovered more than 100 years ago and today still being one of
the most important mysteries in condensed matter physics. Since its discovery a lot of
new type of superconductors appeared. Many of them can not be understood with the
standard BCS theory of superconductivity. There are many families of these
superconductors, for example the cuprates, the iron, the heavy fermions and now even
the twisted bilayer graphene. The mechanism of superconductivity in the two families
with highest critical temperature at room pressure, the cuprates and iron
superconductors, is one of the most important question in condensed matter physics.

In our group we focus on iron-superconductors. There are two main candidates to
explain the superconducting mechanism in these material: the spin fluctuations or the
orbital fluctuations. We have developed a low energy continuum model for the ironbased
superconductors. In this model we propose an Orbital Selective Spin Fluctuation
(OSSF) as the mechanism for the superconducting pairing. We are also able to calculate
in an easy way response functions and fluctuations that let to explore the whole phase
diagram. This is an important issue due to the rich phase diagram they have which
include antiferromagnetic, nematic, superconducting and unknown phases.
In this talk I will tell you about our model and the techniques we use, with which we can
reproduce some different phases of the iron-based superconductors such that the
nematic and superconducting phase.

18 December 2019, 12:30 h. Saln de Actos

Driving quantum many-body systems
out of equilibrium

Dr. lvaro Gmez Len
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

An increasing interest in the out-of-equilibrium physics of quantum systems is arising. Initially, the dynamics has been mostly considered as a tool to perform measurements in a target system. This is clear from the wide use of spectroscopic techniques to analyze materials, transport measurements to uncover electronic structures, etc. However, this is just one application, and the appearance of new technological challenges have required to develop new approaches to tackle them. An interesting one consists in going beyond the weak coupling regime with the driving force. In this case, one is not simply probing the initial system, but is also tuning it towards new phases which can be radically different to the ones of the static system.

The so called "Floquet engineering" has been one of the standard methods to study this, however it focuses on the high frequency regime and the non-interacting limit. Interestingly, at lower frequencies the appearance of topological phases without a static analog has been observed, and in the presence of interactions, interesting features such as time-crystaline order and anomalous thermalization can be observed. For this reasons, it is important to find ways to study the physics beyond the high frequency and non-interacting limit. In my talk I will discuss some results in these regimes, and try to motivate a further study of certain models.

04 November 2019, 12:30 h. Saln de Actos

Cantilever dynamics in high-speed AFM single-molecule force spectroscopy

Manuel Ralph Uhlig

AFM Force spectroscopy is enhancing our understanding of single-molecule, single-cell, and nanoscale biophysical and mechanical properties [1-3]. The well-known Hookes law postulates the proportionality between the interaction force and the instantaneous probe deflection. By studying the probe dynamics through numerical simulations [4], we demonstrated that the total force has two additional contributions: the hydrodynamic one (tip speed dependent) and the inertial one (acceleration dependent). The amplitudes of these Newton dynamics contributions depend on the ratio between the pulling speed at which the interaction is measured and the resonance frequency of the cantilever. Neglecting these additional forces requires the use of low frequency ratios χ, imposing a high-speed limit up to which forces can be accurately quantified.
In this talk, we will show AFM single-molecule force spectroscopy measurements (SMFS) performed on the well-characterized Avidin-Biotin system. At high frequency ratios (χ above 10), we demonstrate the underestimation of the unbinding forces in comparison with the Bell-Evans prediction. We develop an equation to incorporate the Newton dynamics effects into the Bell-Evans theory. We provide a correction factor for the measured forces. This allows to perform faithful AFM SMFS at every rate and, hence, to extract the kinetic parameters of the dissociation process.

[1] E. L. Florin, V. T. Moy, H. E. Gaub, Science 264, 415−417 (1994)
[2] P. Hinterdorfer et al., PNAS 93, 3477−3481 (1996)
[3] D. Alsteens et al., Nat. Nanotech.12, 177-183 (2017)
[4] C. A. Amo, R. Garcia, ACS Nano 10, 7117−7124 (2016)

04 November 2019, 12:00 h. Saln de Actos

Mapping nanomechanical properties of proteins and polymers with bimodal AFM

Simone Benaglia

Fast, high-resolution mapping of the viscoelastic properties of soft matters, represents a major goal of atomic force microscopy (AFM) [1]. Bimodal AM-FM AFM is a suitable method for this purpose, since it allows the simultaneous acquisition of nanomechanical properties without losing in resolution and acquisition speed. This multifrequency configuration combines the robustness and simplicity of an amplitude modulation (AM) feedback in the first mode, with the sensitivity and a high signal-to-noise ratio of a frequency modulation (FM) feedback in the second mode. Finally, through the use of the appropriate contact mechanics model, it is possible to determine elastic and viscous properties of the analyzed sample [2].
Here we show how bimodal AM-FM is applied to extract the elastic properties of soft samples, such as proteins and polymers. Specifically, we characterize the elastic properties of a single protein in liquid, the 20S proteasome which in living organism plays a proteolytic role [3], and the viscoelastic properties of a polymeric assembly, a poly(styrene-block-methylmethacrylate) (PS-b-PMMA) copolymer sample [4].

[1] C. A. Amo, A. P. Perrino, A. F. Payam, and R. Garcia, ACS Nano 11, 8650 (2017).
[2] E. T. Herruzo, A. P. Perrino, and R. Garcia, Nat. Commun. 5, 3126 (2014).
[3] S. Benaglia, V. G. Gisbert, A.P. Perrino, C. A. Amo R. Garcia, Nat. Protoc. 13, 2890 (2018).
[4] S. Benaglia, C. A. Amo, R. Garcia, Nanoscale 11, 1528915297 (2019).

14 October 2019, 12:00 h. Saln de Actos

Biomimetic engineering of nanofibers for tissue regeneration

Andr Giro
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

Biomimetics has recently emerged as a pivotal concept in regenerative medicine, particularly in tissue engineering (TE) applications, since it is consistently boosting the development of advanced healthcare platforms - scaffolds - able to recreate specific natural biological processes towards the regeneration of damaged tissues. As the repair of each cellular microenvironment presents different challenges after injury, it is indispensable that the scaffold could provide an architecture and chemical composition similar to the healthy tissue. In fact, such resemblance with the endogenous extracellular matrix (ECM) should lead to the generation of cell-material interactions capable of accurately inducing a cell behaviour proficient to enhance anatomical and functional recovery. Following this trend, biocompatible systems composed by nanofibers are continuously being explored as candidates for mimicking the arrangement and fibrillar configuration of the ECM components, even though there is a current scarcity of design and fabrication methodologies appropriate to construct complex 3D fibrous architectures. Therefore, this talk will briefly cover promising scaffolding strategies that not only suggest possible routes to build hierarchical organized nanofibrous networks, but also explore the potential of graphene-based materials to induce complementary biochemical and biomechanical cues suitable to upgrade the bioactivity of such TE scaffolds.

14 October 2019, 12:30 h. Saln de Actos

Nanopartculas magneto-plasmnicas como plataformas de deteccin y tratamiento de clulas cancergenas

Dr. Jess Garca Ovejero
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

La combinacin de propiedades pticas como los plasmones de superficie con propiedades magnticas ha abierto un nuevo campo de exploracin en la ciencia de materiales. La posibilidad de crear nanoestructuras biocompatibles que combinen estas dos respuestas permite desarrollar nanoagentes multifuncionales para aplicaciones como la deteccin y el tratamiento de clulas cancergenas.
Las nanoestructuras desarrolladas en este estudio, combinan nanocilindros de Au y nanoesferas de xido de Fe embebidas en una matriz de silice que acta como espaciador entre fases. El ajuste de la geometra de los cilindros de oro as como el tpo de ferrita escogido ofrecen una gran versatilidad en el diseo de las propiedades plasmnicas y magneticas de sus componentes. Sin embargo, resulta crucial analizar los efectos de interaccin entre las fases tras su hibridacin, ya que la respuesta magneto-plasmnica global pueden verse significativamente modificada. En este aspecto, la matriz de slice juega un papel fundamental como atenuador de posibles interferencias.
Para poder hacer uso de estas nanoestructuras en el ambito biomdico existe adems un nmero de condiciones que deben cumplir: una alta estabilidad coloidal, una baja interaccin con proteinas sricas, un tamao hidrodinmico de <200 nm, etc. Por este motivo, las nanoestructuras desarrolladas fueron funcionalizadas con un glicopolmero de baja electronegatividad que favorce su estabilidad coloidal tanto en medio acuoso como en serum de proteinas bovinas.
Las estructuras desarolladas demostraron su potencial como agentes de acumulacin magntica para la deteccin fotoacustica de clulas tumorales circulantes y como agentes de hipertermia ptica y magntica.


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