Posts

Séminaire : Innovative Colloidal Nanostructures: Nanoplatelets and III-V Quantum Dots

tessier_mickaelDr Mickaël Tessier
Ghent university, Belgium

Mercredi 17 avril 2018 à 14h00
IEMN Salle du conseil – Villeneuve d’Ascq

Abstract :

Innovative Colloidal Nanostructures: Nanoplatelets and III-V Quantum Dots
Colloidal Quantum Dots (QDs) are semiconductor nanocrystals in the 1 to 10 nm size range synthesized by wet chemistry process. Because of these small sizes, QDs are subject to quantum-size effect. This effect leads to discrete transitions, much like in an atom or a molecule, with energies higher than the bulk and that are strongly dependent of the QDs sizes. This property has allowed QDs to emerge as a novel class of optoelectronic materials over the last 25 years. The most advanced application of colloidal QDs, at least from a research valorization perspective, is their commercial use in liquid crystal displays (LCDs). First launched in 2013, sales of QDs-enhanced LCDs are expected to achieve 18 million units in 2018.
a. Vials containing QDs of different sizes under UV light. The emitted color depends of the QDs sizes. b. Commercial QDs display (http://www.samsung.com/global/tv/).
Significant advances have been made in the synthesis of QDs since the beginning of the 1990s. The shape of the nanoparticles can now be finely controlled, and nanoparticles with various shapes have been synthesized. In particular, colloidal nanoplatelets are atomically flat nanostructures that present only one dimension of quantum confinement.1In this lecture, I first present how the nanoplateletssizeand composition can be perfectly controlled via inventive synthesis protocols and how theseparameters affects the nanoplatelets optical properties.(2–4)
To facilitate the use of nanocrystals in the industry, interest is shifting from the well-characterized cadmium-based QDs to cadmium-free alternatives such as indium phosphide. We recently proposed protocols based onaminophosphine-type precursors that allow for a cost efficient, up-scaled syntheses of indium phosphide(InP) QDs of different sizes.(5) A detailed understanding of the reaction chemistry is a key in the development of colloidal QDs synthesis. I present an investigation of chemical reactions leading to the formation of InP starting from aminophosphine-type precursors.(6) This mechanism is innovative in the sense that it points out a double role of the phosphorus precursor in the reaction as both a reducing agent and the source of the phosphorus needed to form InP. Its understanding furthers the general use of aminopnictogens for the
synthesis of III-V QDs.(7) Finally, I show that InP QDs can be processed in polymer layer and that their structure can be optimized in order to obtain more efficient and cheaper lighting devices.(8)

References
(1) Ithurria, S.; Tessier, M. D.; Mahler, B.; Lobo, R. P. S. M.; Dubertret, B.; Efros, A. L. Nat. Mater.2011, 10, 936–941.
(2) Tessier, M. D.; Mahler, B.; Nadal, B.; Heuclin, H.; Pedetti, S.; Dubertret, B. Nano Lett.2013, 13, 3321–3328.
(3) Tessier, M. D.; Spinicelli, P.; Dupont, D.; Patriarche, G.; Ithurria, S.; Dubertret, B. Nano Lett.2014, 14, 207–213.
(4) Tessier, M. D.; Javaux, C.; Maksimovic, I.; Loriette, V.; Dubertret, B. ACS Nano2012, 6, 6751–6758.
(5) Tessier, M. D.; Dupont, D.; De Nolf, K.; De Roo, J.; Hens, Z. Chem. Mater.2015, 27, 4893–4898.
(6) Tessier, M. D.; De Nolf, K.; Dupont, D.; Sinnaeve, D.; De Roo, J.; Hens, Z. J. Am. Chem. Soc.2016, 138, 5923–5929.
(7) Grigel, V.; Dupont, D.; De Nolf, K.; Hens, Z.; Tessier, M. D. J. Am. Chem. Soc.2016, 138, 13485–13488.
(8) Dupont, D.; Tessier, M. D.; Smet, P. F.; Hens, Z. Adv. Mater.2017, 29, 1700686.

Séminaire : RF-Sensors in Advanced Applications

Dr.-Ing. Christoph BAER & Ing. Birk HATTENHORST
Institute of Electronic Circuits
Ruhr-Universität Bochum, Universitätsstr. 150, ID 03/324
44780 Bochum – GERMANY

Lundi 23 April 2018 à 14h00
IEMN Salle du conseil – Villeneuve d’Ascq

Abstract :

RF-sensors and Radar systems found their way into civil and industrial applications decades ago. Since then, they reliably measure distances, velocities, and filling levels etc. contact free and with great accuracy. Lately, current trends and technological achievements pushed operating frequencies up to the millimeter wave range, which allows for the determination of various additional physical quantities. Consequently, these novel sensors can be utilized in numerous areas of process industry, civil protection, and daily life. Therefore, their main purpose will be the determination and investigation of environmental parameters that allow for the supervision of crucial system parameters and the interpretation of complex processes. The talk will give an overview on diverse RF‐sensors for different applications, which were explored at the Ruhr‐University Bochum within recent years. The presented sensor applications include: humanitarian demining, mmWave imaging, contact‐free gas sensing, as well as dust and particle determination for process industry and natural hazard protection. Next to the introduction of the numerous areas of application, the different sensor designs will be explained and their field applicability verified. Moreover, opportunities regarding student exchanges between Ruhr-University and Lille University will be introduced and discussed.

About the lecturers:
Christoph Baer received his diploma and doctor degree in electrical engineering at Ruhr-University Bochum in 2009 and 2015, respectively. From 2006 to 2015 he worked as a research engineer on radar systems and radar applications with the Krohne Group in Duisburg, Germany. Currently, Dr. Baer is postdoctoral researcher and academic counselor with the Institute of Electronic Circuits at Ruhr-University Bochum. He is author or co-author of more than 60 international publications and holds 8 international patents. His research interests include ground penetrating radar systems and concepts, methods for humanitarian demining, RF-material characterization and synthesis, sensors for avalanche science, and industrial microwave sensors. Dr. Baer is chairman of the IEEE SIGHT Germany Section.

 

 

Birk Hattenhorst was born in Lübbecke, Germany, in 1989. He received the M.Sc. degree in electrical engineering from the Ruhr-University Bochum, Bochum, Germany, in 2014. He has been a Research Assistant with the Institute of Electronic Circuits, Ruhr-University Bochum, since 2014. His current research interests include microwave measurement techniques, radar technology, antenna design, meta-materials and material characterization.