IMBB - WebCalendar

Time:

16:10

Location:

Computer Science Department, room A115-A117 (ground floor), Voutes

Description:

MST colloquium

Monday, March 27, 2017
Speaker: Dr. Constantinos Stoumpos

Affiliation: Department of Chemistry, Northwestern University, US

Title: “Halide Perovskites: Exploring the Materials Chemistry of High Performance Semiconductors”

Location: Computer Science Department, room A115-A117 (ground floor), Voutes
Time: 16:15 (sharp)
Language: English
Abstract:
Halide perovskites is an emerging class of high performance semiconductors which operate in the visible and infrared energy range (1.1-3.0 eV). The materials have seen a resurgence in the last 5 years owing to the development of efficient photovoltaic devices, spearheaded by CH3NH3PbI3. Starting from the modest 3% in 2009, halide perovskites currently hold a record power-conversion-efficiency of PCE = 22.1%, thus representing the fastest developing solar cell technology known to date. The remarkable physical properties of the halide perovskites stem from their unique electronic structure, which lends the semiconductors high absorption coefficients and charge-carrier mobilities (comparable to III-V semiconductors).
In this talk I will outline the compositional space of the halide perovskites, AMX3, (A+ = Cs, CH3NH3, HC(NH2)2); (M2+ = Ge, Sn, Pb); (X- = Cl, Br, I) and explain the structural chemistry of the materials. I will discuss how small changes in the crystal structure can significantly alter the optical, electrical and electronic properties of the perovskites and I will elaborate on how these can be controlled by subtle modifications in their chemical synthesis. I will further describe how these materials can be applied in functional devices, tackling the problems of i) toxicity -by substituting the toxic Pb metal- and of ii) environmental stability -by employing the layered Ruddlesden-Popper perovskites.

Time:

16:10

Location:

Computer Science Department, room 115-A117 (ground floor), Voutes

Description:

Monday, April 3, 2017
Speaker: Dr. Emmanuel Logakis

Affiliation: ABB Switzerland Ltd

Title: Polymer-based nanocomposites with tailored electrical properties: Applications in aerospace and electrical power technologies

Location: Computer Science Department, room 115-A117 (ground floor), Voutes
Time: 16:15 (sharp)
Language: English

Abstract:
Polymer nanocomposites based on carbon nanotubes (CNTs) and, more recently, on graphene and graphene oxide (GO) have attracted considerable attention over the last two decades. An in-depth understanding, and predictive capability of the key structure-property relationships governing the electrical/dielectric properties, has been established allowing the application of these novel materials in various technological areas. Two characteristic examples would be discussed in this presentation.
In the first part, an end application of CNTs incorporation in an aerospace grade epoxy resin is presented. The increased use of carbon fibre composites in aerospace components brings to the surface issues related to their poor lightning strike performance. Lightning strikes can induce severe damages due to the dielectric nature of the host matrix even in the case where the reinforcement is highly conductive e.g. carbon fibres. Metallic meshes or foils, co-cured within the outer layer of laminates, are currently used for protection. This solution comes at a cost in terms of weight and manufacturing complexity, presents difficulties in repair and most importantly does not provide full protection. The influence of CNTs on the lightning strike performance of carbon fibre composites is demonstrated.
In the second part, a method for the production of insulating materials with predetermined electrical/dielectric properties is discussed. The concept is applied on weak locations (typically interfaces) that are prone to failures due to electric field concentration in various medium and high voltage products. It is based on the controlled reduction (restoration of the graphitic lattice) of graphene oxide in GO-based composites, accompanied by a smooth transition from insulating to conducting behaviour. GO, produced by the oxidation of graphite, consists of a hexagonal ring-based carbon network bearing hydroxyl and epoxide functional groups on either side of the sheet, whereas the sheet edges are mostly decorated by carboxyl and carbonyl groups. These functional groups disrupt the sp² hybridization in the lattice leading to a significantly higher resistance compared to graphene, depending on degree of oxidation. Restoration of the lattice can be achieved by several chemical and electrochemical methods as well as by thermal treatment or even irradiation (laser, X-ray, UV, flash, e-beam). Depending on method and conditions, different level of restoration of the electronic structure of carbon plane is achieved leading to a broad band of conductivity values of the reduced graphene oxide (rGO). Two approaches were adopted to demonstrate the concept: I. A temperature gradient applied on a composite rod leading to a gradient in the conductivity along its length, and II. Surface treatment by a pulsed or a continuous laser on composite plates leading to a selective reduction at the targeted locations. The GO-based materials showed a very high bandwidth in their conductivity/permittivity upon the thermal or laser treatment (ranging from values the pure insulating matrix exhibits up to about 0.1 S/m), indicating that under optimal processing conditions conductivity can be tailored and graded irreversibly within these ranges.

Time:

12:00 - 14:00

Location:

Αίθουσα 7Α-01 Πτέρυγα Μεταπτυχιακών Σπουδών Ιατρική Σχο

Description:

ΣΕΜΙΝΑΡΙΟ

“Neurotrophic factor signaling in cerebellar development”

Carlos F. Ibáñez
Professor of Molecular Neurobiology, Dept. of Neuroscience, Karolinska Institute & Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore

Παρασκευή 7 Απριλίου 2017
12.00-14.00
Αίθουσα 7Α-01 Πτέρυγα Μεταπτυχιακών Σπουδών Ιατρική Σχολή

Host: Γιάννης Χαραλαμπόπουλος, Τηλ. 2810394531

Time:

12:10

Location:

Chemistry Seminar Room

Description:

CHEMISTRY COLLOQUIUM

SPEAKER: Dr. Nikos S. Hatzakis

Associate Professor

Department of Chemistry & Nanoscience center University of Copenhagen

TITLE: How do proteins recognize and interact with each other ?
Single molecule insights on the role of conformational sampling to biomolecular recognition

DATE: Friday, 7th April 2017

TIME: 12:00

ROOM: Chemistry Seminar Room

Time:

14:00

Location:

“Seminar Room 1”, FORTH’s bldg

Description:

IMBB COLLOQUIUM

Michalis AIVALIOTIS
Proteomics Facility

Title:

Time:

14:20

Location:

3rd Floor Seminar Room (Physics building)

Description:

MST colloquium
Friday, April 7, 2017
Speaker: Dr. K. Tsakmakidis

Affiliation: École polytechnique fédérale de Lausanne, Switzerland

Title: Χωρο-Εντοπισμός Κυμάτων: Από το Σταμάτημα του Φωτός στην Κβαντική Αυτοοργανούμενη Κρισιμότητα και την Υπέρβαση του Θεμελιώδους Ορίου Χρόνου – Εύρους Ζώνης

Location: 3rd Floor Seminar Room (Physics building)
Time: 14:15 (sharp)
Language:English

Abstract:
Μία από τις πιο εvδιαφέρουσες πρόσφατες εξελίξεις στον τομέα της νανοτεχνολογίας και της φυσικής συμπυκνωμένης ύλης θεωρείται η σύλληψη και η κατασκευή φωτονικών μεταϋλικών (photonic metamaterials), που φιλοδοξούν σε ένα βάθος χρόνου να αντικαταστήσουν τα συνήθη νανοηλεκτρονικά υλικά. H σχεδίαση, βελτιστοποίηση και κατασκευή τέτοιων τρισδιάστατων νανοφωτονικών υλικών - ειδικά όταν εμπεριέχουν μηχανισμούς οπτικού κέρδους, κβαντικά στοιχεία ή μη γραμμικότητες - αποτελεί μία ιδιαίτερα απαιτητική αλλά απαραίτητη άσκηση. Οι εφαρμογές των υλικών αυτών κυμαίνονται από τη δημιουργία φακών που υπερβαίνουν το όριο περίθλασης μέχρι 'μανδύες αορατότητας' και κυματοδηγούς σταματήματος (εκμηδενισμού της ταχύτητας) του φωτός. Στην παρούσα ομιλία θα εξετάσουμε συγκεκριμένα πώς τα υλικά αυτά μπορούν να χρησιμοποιηθούν για να επιλύσουν ένα από τα πιο επίμονα προβλήματα στον τομέα της φυσικής συμπυκνωμένης ύλης, δηλ. το πώς να επιτευχθεί χωρικός εντοπισμός (localization) ενός κύματος σε ένα μέσο με διακυμένουσες παραμέτρους εν τη παρουσία απωλειών. Θα δούμε ότι η επίλυση του προβλήματος αυτού οδηγεί σε μία θεμελιωδώς νέα κατηγορία μεταβάσεων φάσης (phase transitions) η οποία διεγείρεται από κβαντικές διαταραχές και χαρακτηρίζεται από την ικανότητά της να αυτοοργανώνεται ('κβαντική αυτοοργανούμενη κρισιμότητα'), χωρίς δηλ. να απαιτεί ακριβή προσδιορισμό εξωγενών παραμέτρων (fine-tuning). Τέλος, θα διαπιστώσουμε ότι τα ίδια υλικά επιτρέπουν την επίλυση ενός επιπλέον, επίσης πολυδεκαετούς, προβλήματος – το πώς, υπερβαίνοντας την αμοιβαιότητα Lorentz, να κατασκευάσουμε ευρυζωνικές κοιλότητες (broadband cavities) ικανές να αποθηκεύουν κυματική ενέργεια για μεγάλα χρονικά διαστήματα, στις οποίες ο χρόνος αποθήκευσης του κύματος και το εύρος ζώνης της κοιλότητας (αμοιβαιότητα Fourier) να είναι εντελώς αποσυνδεμένες παράμετροι.

For forthcoming colloquia, please visit:
http://www.materials.uoc.gr/en/colloquia

Time:

16:10

Description:

Speaker: Dr. Emmanouil Dimakis

Affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Germany

Title: Extremely strained III-V semiconductor nanostructures

Location: Computer Science Department, room A115 (ground floor), Voutes

Time: 16:15 (sharp)

Language: English

Abstract:

Semiconductor materials have fuelled many technological breakthroughs over the last half century (wireless communication, computing, solid-state lighting, solar powering, etc.), leaving a monumental impact on our society. Switching, amplification and light-electricity (electricity-light) conversion are the most important functions they perform. The family of III-V compound semiconductors, in particular, is known for its high electron mobilities and direct band gaps. Most importantly, they are versatile materials due to the possibility to tailor their (opto)electronic properties by selecting their composition appropriately. When grown heteroepitaxially, though, this possibility is constrained by the lattice mismatch with the substrate.

The situation is significantly different in epitaxial nanostructures, where more possibilities for strain engineering are offered at the nanoscale and new physical phenomena with potential device applications can be explored. On the other hand, the growth of such nanostructures is very demanding and necessitates good understanding and precise control of the growth mechanisms. Two examples of extremely strained nanostructures will be presented in this talk. The first example concerns InN/GaN multiple quantum wells with a thickness of one monolayer each. The role of the “self-regulation mechanism” and the high lattice mismatch (11 %) in the successful growth will be highlighted, and the signatures of two-dimensional electron conductivity and its topological nature will be presented. The second example concerns vertical GaAs/InxGa1-xAs core/shell nanowires on Si substrates. This system consists of three lattice-mismatched materials, but the unique geometry of nanowires allows for growing them defect-free. The self-catalyzed vapor-liquid-solid growth mode, the peculiar accommodation of misfit strain, and the application of this type of nanowires in light emitting diodes and modulation-doped heterostructures will be discussed. The monolithic integration of GaAs/InxGa1-xAs core/shell nanowires in Si-CMOS platforms would have an enormous technological impact as high electron mobilities would boost the performance of transistors and composition-tunable direct bandgaps would add efficient optoelectronic functionalities (more-than-Moore).

Time:

16:10

Description:

Speaker: Dr. A. Papagiannopoulos

Affiliation: Institutes of Physical Chemistry, National Hellenic Research Foundation

Title: Nanostructured functional soft materials by self-organization of complexes between biological/synthetic macromolecules and bioactive compounds

Location: 3rd Floor Seminar Room (Physics Building)

Time: 16:15 (sharp)

Language: English

Abstract:

In the next decade the interactions between macromolecular components with proteins, drug molecules and genetic material will be exploited for the creation of novel functional nano-structures with advanced properties. Control of the organization of matter at the nano-scale is the key issue in modern applications of nano-medicine (drug-loaded nanoparticles), food science (enriched food matrices), tissue engineering (nanocomposite hydrogels) and biotechnology (protein separation). Macromolecular components offer versatile templates for creation of functional, stimuli-responsive and often bioactive systems via self-assembly. Modifications by physical self-assembly and temperature treatment is in cases preferred against chemical modification e.g. when the introduction of a chemically modified substance is a time consuming process. In a broader sense exploitation of physical interactions between natural components is a route to acceptable novel products. Small angle scattering methods and spatially sensitive measurements of viscoelasticity (i.e. microrheological techniques) are going to play central role in the imminent developments as they provide information at the relevant length scales. In this talk previous work on self-organization of synthetic and biological macromolecules, their interactions with proteins and the response of such systems to external stimuli will be presented. In more detail the role of electrostatic and hydrophobic interactions, the effect of thermal response and the hierarchical organization in synthetic, biological and hybrid aqueous solutions will be explored. The open questions in polymer/protein interactions will be illustrated and the potential of producing novel soft-materials by controlling these interactions will be presented.

Time:

12:00

Location:

“Seminar Room 1”, FORTH’s bldg

Description:

IMBB COLLOQUIUM

Konstantina KATSAROU
Kalantidis' Lab
Title: "Viroids: Infectious long non-coding RNAs"

Friday, April 287th 2017 @ 12:00
“Seminar Room 1”, FORTH’s bldg

Time:

14:10

Location:

3rd Floor Seminar Room (Physics building)

Description:

Tuesday, May 2, 2017
Speaker: Dr. N. Koumakis

Affiliation: Institutes of Physical Chemistry, National Hellenic Research Foundation

Title:Studies on Active Matter

Location:3rd Floor Seminar Room (Physics Building)

Time:14:15 (sharp)
Language: English

Abstract:
Active matter, matter with self-propelling constituents, has recently sparked the interest of the soft matter scientific community. Active components may be biological i.e. bacteria, or even chemically driven particles. The ability of active matter to provide energy through motion at a microscopic level, produces interesting phenomena, such as effective interactions, swarming, internally generated flows and activity induced phase transitions. Here, we examine various aspects of model active matter systems, ranging from hydrodynamically induced synchronization, active transport effects and complex interactions between active and non-active components.

Time:

16:10

Location:

3rd Floor Seminar Room (Physics building)

Description:

Wednesday, May 3, 2017
Speaker: Dr. E. Glynos

Affiliation: FORTH/IESL

Title: Designing Materials at the Macromolecular Level: From Controlling the Polymer Behavior at
Surfaces and Interfaces to High Performance Solid Polymer Electrolytes for Energy Storage

Location: 3rd Floor Seminar Room (Physics Building)

Time: 16:15 (sharp)
Language: English

Abstract:
The macroscopic properties of a polymer material are intimately related and are encrypted to its macromolecular structure. By adjusting the chemical structures of the constituent monomers, the molecular weight, and the linear or non-linear/branched architecture of the polymers, it is possible to formulate materials with an amazing variety of physical properties. To this end, advances in polymer chemistry have led to the synthesis of a wide range of well-defined non-linear polymers with controlled architectures (stars-shaped, H-shaped, pom-pom, ring, comb), compositions, and degree of polymerization, have provided material scientists the ability to design materials with desired/on-demand properties that meet the requirements of specific applications.

In the first part, I will provide evidence that several macroscopic properties of polymeric material, where polymer-interface interactions play a significant role, may be readily controlled simply by changing the macromolecular architecture and without changing the monomer or the interface chemistry. In particular, I will show that the equilibrium contact angles of macroscopic droplets of star-shaped polystyrene (SPS) molecules on oxidized silicon substrates, may be as much as one order of magnitude smaller than that of their linear analogues (linear polystyrene, LPS) on the same substrates. I will show how the aforementioned enhanced interfacial properties of star-shaped polymer are manifested on the vitrification behavior of supported polymer films and on the mechanical properties of polymer nanocomposite materials.

In the second part, I will introduce the use of polymer nanostructured nanoparticles of asymmetric mikto-arm copolymers, in which stiff insulating arms complement ion-conducting arms, as additives to liquid electrolytes for the synthesis of solid polymer electrolytes that exhibit an unprecedented combination of high modulus (G' ~ 0.1 GPa) and ionic-conductivity at room temperature (σ ~ 10-4 S/cm), necessary for practical applications. I will demonstrate that the final/desired morphology and phase dimension of the nanostructured solid-polymer electrolytes may be precisely controlled as the final morphology is encrypted within the macromolecular characteristics and the chemical composition of the "nanoparticles". Our strategy offers tremendous potential for the design of all-polymer nanostructured materials with optimized mechanical properties and ionic conductivity over a wide temperature window for advanced lithium battery technology.

For forthcoming colloquia, please visit:
http://www.materials.uoc.gr/en/colloquia

Time:

12:00

Location:

“Seminar Room 1”, FORTH’s bldg

Description:

IMBB JOINT COLLOQUIA

Speaker 1: Emmanouela KALLERGI (Nikoletopoulou's Lab)

Title: "Regulation of Neuronal Autophagy by Neurotrophin SIgnaling"

Speaker 2: Alexios MOLFETAS (Kokkinidis' Lab)

Title: "Insights from the resurrection of a dead enzyme".

Friday, May 5th, 2017 @ 12:00
“Seminar Room 1”, FORTH’s bldg