Experimental Soft Matter Physics
post-docs

New paper on organic functionalized nanoparticles in nematic LCs


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(click the above image to access the article online)


Congratulations to Martin on the publication in J. Mater. Chem. C of his dielectric spectroscopy study “Why organically functionalized nanoparticles increase the electrical conductivity of nematic liquid crystal dispersions”!

This paper gives a first systematic study of how and why nanoparticle doping raises the electrical conductivity of thermotropic liquid crystals like the commonly studied 5CB. By a careful analysis of the dielectric spectra, he shows that the hydrodynamic radius of the ionic charge carrier is much smaller than the nanoparticles, ruling out the particles themselves as the source of conductivity. The ligand molecules are also not the reason, as is demonstrated by strong sonication of the dispersions, such that the ligands detached from the nanoparticles. While this causes nanoparticle aggregation and the loss of suspension stability, the effect on conductivity is negligible. The ligand shell is, however, partially responsible, because the ions giving rise to the conductivity increase are most likely remnants from the ligand-functionalized nanoparticle synthesis process. We propose that these ions are brought in with the ligand shell when the particles are dispersed in the 5CB. Interestingly, the ions appear not to be released in an isotropic and aromatic solvent such as toluene, which is often the host for commercial gold nanoparticle suspensions, but 5CB is an ideal host for their dissolution. The aliphatic ligand shell has a higher compatibility with 5CB than with toluene, thanks to the alkyl tail of 5CB, and at the same time the high polarity of the 5CB (due to the cyano group) allows better ion dissolution than in regular hexane. Finally, the nematic order of the 5CB solvent provides an anisotropic environment in which the ligands are stretched out preferentially along the director, making release of ligand-bound ions to the solvent more likely. 



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New Post-Doc! Manos Anyfantakis joins the team

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We're happy to welcome our new post-doc: Manos Anyfantakis! He officially joined the ESMP team at the start of July, and will mainly be working on advancing projects related to hydrodynamic flows, kinetic arrest, LC structure formation in the CNC work we have happening. He received his masters applied molecular spectroscopy in 2007, earned a phd in chemistry in Greece in 2010, and has since travelled to Germany and France for postdocs on the wetting of surfactant solutions and optofluidics phenomena before finally joining us in Luxembourg. You can contact Manos via e-mail here.





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Christina Schütz joins the team

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We're happy to welcome our new post-doc: Christina Schütz! She officially joined the ESMP team at the start of February, and will mainly be working with Camila on advancing projects related to CNC work. She received her master's from Martin-Luther-University Halle-Wittenberg in Germany (the same place where Jan did his habilitation thesis!), and then her PhD in materials chemistry from Stockholm University. Christina joins us for her 2nd post-doc, after spending a year at Wim Thielemans' lab in KU Leuven, Belgium. Happy to have another chemist joining us!

You can contact Christina via e-mail here.






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Hakam Agha joins the team

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We have the great pleasure of welcoming Dr. Hakam Agha into the ESMP team. He will be working as a post-doc with us and with the LC Nano group of Giusy Scalia for at least six months, hopefully more. He got his Ph.D. in physics from the University of Strasbourg and was most recently working as post-doc with Christian Bahr and Stefan Herminghaus at the Max Planck Institute for Dynamics and Self-Organization in Göttingen. You can contact Hakam via e-mail here.

Welcome!!


Rao and Larry join the group

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On the 14th of October 2015 we had the unusual pleasure to welcome two new group members on the same day, Venkatasubbarao (we call him just 'Rao') Jampani (left) and Larry Honaker (right). Rao is a post-doc working within the INTERACT project, focusing primarily on soft robotics based on liquid crystal elastomers with non-standard morphologies and topologies, and Larry is a Ph.D. candidate, working within his own AFR project LIMEFLOW, which deals with flow of liquid metals, in particular the possibility of achieving liquid metal jets co-flowing within polymer solutions.

Johanna Bruckner joins as post-doc

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We have the fortune to welcome Dr. Johanna Bruckner in our team. Johanna recently defended her Ph.D., carried out under the supervision of Frank Gießelmann, at the University of Stuttgart, and she secured a fellowship from the Dr. Leni Schöninger Stiftung for doing a six-month post-doc with us in Luxembourg. She will be working on liquid crystalline suspensions of cellulose nanocrystals (CNC) in various solvents. In doing so, she will be working closely with our other CNC researchers, in particular Camila, who is the Ph.D. candidate in the MISONANCE project.

Yong Geng joins as post-doc

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It is our great pleasure to welcome Yong Geng to our group as a post-doc. After obtaining his Ph.D. with Prof. Maria Helena Godinho in Lisbon he worked as a post-doc with Prof. Ralf Stannarius and Dr. Alexey Eremin in Magdeburg, before he came to Luxembourg. He will be working on colloidal crystals of cholesteric shells, produced in a microfluidic set-up, focusing on the optical properties and the pattern formation of these systems. This research is the core of the interdisciplinary dual-PI project UNIQUE, funded by University of Luxembourg. The second partner of the project is the team around Gabriele Lenzini and Peter Ryan at the UL's Interdisciplinary Center for Security and Trust, which will analyze the patterns generated by the colloids from an information content point of view. Young will thus interact closely with Samir Ouchani, a post-doc in computer science working under the guidance of Gabriele.

Martin Urbanski joins the group

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We have the pleasure of welcoming Dr. Martin Urbanski to the Experimental Soft Matter Physics group as a post-doc. He comes from the University of Paderborn, Germany, where he worked with Prof. Heinz Kitzerow. Martin secured a personal post-doc grant from the Fonds National de la Recherche Luxembourg (FNR) for a two-year project entitled DISGONA. He will be studying nematic liquid crystals functionalized with gold nanoparticles by means of dielectric spectroscopy.