CE09 - Nanomatériaux et nanotechnologies pour les produits du futur

Self-assembly of nanoparticles: from periodic superlattices to quasicrystalline phases – SoftQC

Submission summary

Self-assembly is the process by which elementary building blocks spontaneously form organized structures of a higher level of complexity. Being able to master these emerging structures and their properties is of great fundamental and applied importance in research worldwide. Soft matter is playing a key role in this revolution, driven forward by the capability to synthesize nanoparticles with ever increasing complexity. Unfortunately, predicting and then controlling the emerging structure is not a trivial task. Complex superlattices of spherical nanoparticles (NPs) are promising candidates to produce new smart materials including, for example, photovoltaic cells, catalytic devices, biosensors and semiconductors.
In this project we will investigate two classes of complex superlattices, Frank and Kasper phases (FKPs) and quasi-crystalline phases (QCPs), which emerge in NPs self-assembly as a consequence of a competition between two length-scales in the interaction. The conditions to obtain stable structures will be carefully determined, like the deformability of the soft corona, the strength of the interactions and the size distribution of the NPs. Key questions are whether a single population with suitable polydispersity in size can promote superlattice formation, or whether the use of binary mixtures with two appropriate sizes of NPs is a necessary route. In this project, we propose an integrated approach in which experiments, theory and simulations will be used to understand the stability and the properties of FKPs and QCPs.
The team members will combine their skills and experience to develop this project in all its aspects. First, two types of NPs, semi-conducting (CdSe) and metallic (Au) (task 1), will be synthesized, and their self-assembly will be explored using Small-Angle Scattering (SAS), both separately and in binary mixtures. Key control parameters (core size, ligand nature, softness of the corona) will be varied to tune the interaction potential between NPs and will be determined using form factor and structure factor measurements (task 2). Self-assembled phases will be experimentally achieved in 3D and 2D (task 3) and the most promising assemblies for their optical and transport properties will be selected. 3D numerical simulations of the same systems (task 4) will be done using model interaction potentials based on both 2-body and many-body interactions. Microscopic theoretical models will be developed along with calculation of predictive phase diagrams for finding the stability criteria for FKPs and QCPs. Ultimately, this project should open the way to new metamaterials based on aperiodic order.
A strong asset of the project is to gather people with close scientific interests and who already work together. Two different laboratories are involved: the Laboratoire de Physique des Solides (LPS, Orsay) and the Laboratoire de Chimie of ENS Lyon. At LPS, two research groups are involved: MATRIX (experimental part) and THEO (theory).
The budget for this 4-year collaborative research program is of 397 k€ (429 k€ with 8 % of charges -32 k€-). Three non-permanent people will be recruited with strongly coupled research projects. A PhD student (three years, 98 k€) at ENS Lyon will synthesize by nanochemistry the NPs (task 1) and investigate their self-assembly (task 3). A postdoc researcher (18 months, 86 k€) at LPS-exp will work on the same NPs and investigate their interactions in solution using SAS -structure factor determination- (task 2) and their self-assembly in 3D (task 3). In parallel, a PhD student (three years, 98 k€) at the LPS-theo will work on all the theoretical aspects using numerical simulations (task 4). In addition, 78 k€ (including 57 k€ for equipment) at LPS (exp and theo) and 36 k€ at ENS-Lyon will be used for chemicals, new X-ray lab equipment, access to electron microscopy platforms, computational resources, travel expenses (synchrotron runs, conferences) and internships for Master students.

Project coordination

Marianne Impéror (Laboratoire de Physique des Solides)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LPS Laboratoire de Physique des Solides
LCH - CNRS LABORATOIRE DE CHIMIE

Help of the ANR 380,931 euros
Beginning and duration of the scientific project: January 2019 - 48 Months

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