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CNRS 
Superlattices of metallic nanoparticles with complex symmetries
Université Paris-Sud, Orsay
Laboratoire de Physique des Solides
Physics (Other) Inorganic Chemistry Physical Chemistry 
Full Description:

 

Profile of the candidate:

The subject is at the interface between chemistry and physics. The candidate will have the opportunity to acquire a wide spectrum in the field of nano-materials.
The initial training the candidate can be either in chemistry or physics.
The key is that the candidate is someone motivated and open, ready to get involved in all aspects of the project.
Candidates from France or abroad are welcomed to apply.

 

 

PhD project:

Complex ordered states in condensed matter, such as quasicrystals, are a fascinating subject in science. In the early 80’s, it was discovered that metallic alloys can organize in a new state of matter called quasiperiodic crystals or quasicrystals. A new concept was born: order in crystals is not restricted to periodic lattices only. This important discovery gave rise to many developments in crystallography, condensed matter physics and mathematics. Since 2004, this field of research was given a new impetus when it was discovered that this concept could be extended to the nanoscale in soft matter systems like soft nanoparticles. A new area in the field of aperiodic order is now open by the use of soft nanoparticles, and great progress is expected during the next years. Beyond a deeper understanding of ordering phenomena, direct benefits for Nanoscience are in view, such as the emergence of metamaterials based on aperiodic order.

During the past decade, progress in the design of nanoparticles has been made world-wide, allowing extended control of their morphology. This development of Nanochemistry opens huge possibilities in terms of size, shape and chemical nature of the nanoparticles. To go towards applications, one of the major challenges today in Nanoscience is to control their assembly into superlattices. Indeed, applications in many fields will involve much less properties of individual nanoparticles than properties of a whole assembly. Controlling the type of order between the nanoparticles in these assemblies would then be a matter of tuning the shape of the nanoparticles and the interactions between them.

Very recently, a new Frank and Kasper phase built by self-assembly of gold nanoparticles have been discovered at the LPS (Figure 1 and reference 1).  This phase has been observed in suspensions of metallic nanoparticles made of a gold core -diameter of 2.4 nm- covered with hexanethiol ligands. Frank and Kasper phase are complex periodic phases, with large unit cells, and are closely related to quasi-crystalline phases. They are tetrahedral close packed structures (tcp phases) in which local order is related to icosahedral coordination. This result opens the way towards building more and more complex superlattices including quasicrystalline order.

The PhD’s project will be to explore the self-assembly of metallic nanoparticles into complex superlattices. A key point is that these nanoparticles have a ‘soft’ component, the soft organic shell located around the metallic core. The core and shell dimensions of the nanoparticles will be tuned by adjusting the synthesis conditions. In this way, different sizes for the metallic core and for the organic ligand layer will be obtained. The interaction potential between the nanoparticles will depend on these two parts (hard core and soft shell) and it will control the type of superlattices formed during self-assembly. The interaction potential and the self-assembly into superlattices will be investigated mainly using Small Angle X-ray Scattering, with instruments available at the LPS. Depending on the results, modelisation of the different superlattices, based on the interactions between the nanoparticles, will be performed. Lastly, the optical properties (plasmon resonance) of the superlattices will also be studied.

Reference:

 

 

[1] Hajiw, S.; Pansu, B.; Sadoc, J. F., Acs Nano 2015, 9, 8116-8121[1] Hajiw, S.; Pansu, B.; Sadoc, J. F., Acs Nano 2015, 9, 8116-8121

Context:

The LPS (Laboratoire de Physique des Solides) offers a unique place to perform such interdisciplinary research.

Many experiments are available directly in the laboratory: X-ray scattering and diffraction, dynamic light scattering -DLS-, electron microscopy -SEM, TEM and cryo-TEM, chemistry laboratory, optical microscopy, UV-vis spectrometer, NMR, etc ...  

Moreover, the French synchrotron SOLEIL is located only a few kilometers away in the same area.



Posted on: 27 January 2016Deadline to apply: 10 April 2016Start Date: 01 October 2016 Duration: 36 months
The Fund category is Public Funding - University and the salary is 20-25k€ annual gross
Doctoral School is Physics of Ile-de-France in the Ile-de-France Region.

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