No need to hit the iron while it’s... small!

14/01/2025 Scientists from CNRS have studied the shape evolution of gold nano-tetrapods and revealed a two-step kinetics process: the four arms—initially sharp—quickly blunt, followed by a slow retraction towards an almost spherical final shape. Deforming macroscopic metallic objects requires considerable force. At the nanoscale, however, things are quite different: surface forces alone are often sufficient to reshape nanoparticles, guiding them towards the most energetically favorable form. Understanding this "nano-metallurgy" is crucial not only for advancing fundamental knowledge but also for driving progress in nanotechnology. Yet, the processes involved are challenging to monitor in real-time. A team of researchers from several French and European laboratories [1] recently published a detailed study in Nano Letters on the transformation pathway of metastable gold particles, initially featuring four sharp arms, into nearly spherical particles. Thanks to their well-defined geometry, these "nano-tetrapods" are easier to study than "nanostars," which have similar characteristics but more varied morphologies. By combining electron microscopy, X-ray scattering, optical spectroscopy techniques, and advanced data processing, the researchers uncovered a complex kinetic process. This begins with a rapid flattening of the tips towards a {110} facet of gold’s crystalline lattice, followed by a slower reshaping phase into an isometric form. Beyond the conceptual understanding of their evolution, this study will enable the use of these nano-objects in nonlinear optical applications [2], thanks to their unique shape, which lacks a center of inversion. [1] Damien Alloyeau at Laboratoire Matériaux et Phénomènes Quantiques, (Université Paris Cité/CNRS), le Laboratoire de physique des solides (CNRS/Université de Paris-Saclay), Doru Constantin at l'Institut Charles Sadron (CNRS/Université de Strasbourg) and the European synchrotron ESRF (Grenoble). [2] Jieli Lyu et al., Shape-Controlled Second-Harmonic Scattering from Gold Nanotetrapods, J. Phys. Chem. C 126, 9831-9835 (2022). Reference : Jieli Lyu et al., Two-step reshaping of acicular gold nanoparticles, Nano Letters (2025). DOI: 10.1021/acs.nanolett.4c05601

Depletion-Induced Tunable Assembly of Complementary Platonic Solids

13/12/2024 Multicomponent self-assembly has been explored to create novel metamaterials from nanoparticles of different sizes and compositions, but the assembly of nanoparticles with complementary shapes remains rare. Recent binary assemblies were mediated by DNA base pairing or induced by solvent evaporation. Here, we introduce depletion-induced self-assembly (DISA) as a novel approach for constructing tunable binary lattices. In situ structural analysis in the real and the reciprocal spaces demonstrates DISA of a binary mixture of octahedra and tetrahedra into extended supercrystals with Fm m symmetry. The inter-particle distance, adjustable by depletant concentration, offers a versatile method for assembling nanoparticles into ordered structures while they remain dispersed in a liquid phase. We show that DISA can control the packing fraction of such binary supercrystals between φ=0.37 and φ=0.66, much lower than dense packing in the dry state. These findings highlight DISA’s potential for creating complex and highly ordered metamaterials with tailored properties. Long term collaboration with ICS (Strasbourg) and MPQ (Paris) laboratories https://doi.org/10.1021/acs.nanolett.4c04923

Anisotropic Thermal Transport in Tunable Self-Assembled Nanocrystal Supercrystals

01/12/2024 Realizing tunable functional materials with built-in nanoscale heat flow directionality represents a significant challenge that could advance thermal management strategies. Here we use spatiotemporally resolved thermoreflectance to visualize lateral thermal transport anisotropy in self-assembled supercrystals of anisotropic Au nanocrystals. Correlative electron and thermoreflectance microscopy reveal that nano- to mesoscale heat predominantly flows along the long-axis of the anisotropic nanocrystals, and does so across grain boundaries and curved assemblies while voids disrupt heat flow. We finely control the anisotropy via the aspect ratio of constituent nanorods, and it exceeds the aspect ratio for nanobipyramid supercrystals and certain nanorod arrangements. Finite element simulations and effective medium modeling rationalize the emergent anisotropic behavior in terms of a simple series resistance model, further providing a framework for estimating thermal anisotropy as a function of material and structural parameters. Self-assembly of colloidal nanocrystals promises an interesting route to direct heat flow in a wide range of applications that utilize this important class of materials. Nice collaboration with James Utterback (Sorbonne University) and coworkers from other labs. https://doi.org/10.1021/acsnano.4c12991

Elucidating Supercrystal Mechanics and Nanoparticle Size and Shape Effects under High Pressure

01/10/2024 Supercrystals, extended lattices of closely packed nanoparticles (NPs), present exciting possibilities for various applications. Under high pressures, typically in the gigapascal (GPa) range, supercrystals undergo significant structural changes, including adjustable inter-particle distances, phase transformations, and the formation of new nanostructures through coalescence. While prior research has focused on ligand engineering's impact on supercrystal mechanical response, the influence of NP shape remains unexplored, especially for NPs larger than 10 nm coated with hydrosoluble ligands. This study examines the effects of NP shape on the mechanical properties of supercrystals using high-pressure small-angle X-ray scattering (HP-SAXS) and focused ion beam-scanning electron microscopy (FIB-SEM) tomography. Notably, supercrystals exhibit higher hardness levels compared to previously reported values for gold supercrystals, attributed to the use of larger nanoparticles. Spherical and tetrahedral NPs rearrange before collapsing under pressure, whereas rods and octahedra coalesce without prior structural rearrangement, likely due to their higher packing fraction. Additionally, anisotropic deformation of NP lattices and sintering does not always correlate with deviatoric stresses. These findings refine the understanding of complex processes governing supercrystal structure under high pressure, opening new avenues for NP engineering and advancing plasmonic applications under extreme conditions. Nice collaborative work! DOI: 10.1002/sstr.202400303

First results on the use of accoustic levitation published

17/10/2024. See article in open access here: https://onlinelibrary.wiley.com/doi/full/10.1002/admi.202400323 Highlight on the LPS website: https://equipes2.lps.u-psud.fr/matrix/droplet-levitation-for-self-assembly-of-liquid-crystals/ Highlight on SOLEIL website: https://www.synchrotron-soleil.fr/fr/actualites/levitation-de-gouttes-pour-lauto-assemblage-de-cristaux-liquides Evaporation-induced self-assembly (EISA) is a versatile method for generating organized superstructures from colloidal particles, offering diverse design possibilities through the manipulation of colloid size, shape, substrate nature, and environmental conditions. While some work highlighted the potential of EISA to investigate phase transitions of inorganic liquid crystals, the influence of sample environment to determine their phase diagrams is often overlooked. In this work, we compare the self-assembly of lyotropic liquid crystals by EISA on hydrophilic or hydrophobic substrates, and by acoustic levitation (absence of substrate). We focus on imogolite nanotubes, a model colloidal system of 1D charged objects, due to their tunable morphology and rich liquid-crystalline phase behavior. We demonstrate the feasibility to obtain phase transitions in levitating droplets and on hydrophobic substrate, whereas self-assembly was limited on hydrophilic supports. Moreover, the aspect ratio of the nanotubes proves to be a pivotal factor, influencing both transitions and the resulting materials shape and surface. Besides material shaping, acoustic levitation emerges as a promising method for studying phase transitions by EISA, toward the rapid establishment of phase diagrams from diluted to highly concentrated states using a limited volume of sample.

Jaime won ECIS-Enzo Ferroni Award for Best Oral Presentation in the young researchers category

1-6 spetember 2024  Jaime won ECIS-Enzo Ferroni Award for Best Oral Presentation in the young researchers category at ECIS 2024 in Copenhagen. Congratz!

Telluride 2024

01-05/07/2024 I recently had the pleasure to attend to Telluride 2024 in Biarritz about solution-based nanoparticle synthesis and their application in devices.

Young Distinguished Scholar Nanophotonic

The 25th of may, we were invited to join an online event organized by colleagues in China. The event was broadcasted on a streaming platform with more than 10000 simultaneous viewers! Cyrille received an award at this occasion. Thanks again for the invitation and the organization.

Recruitment of material scientists for CNRS position in 2024

From the 14th of may to the 26th of may, we have listened to 60 presentations from researchers to recruit and promote CNRS scientists in 2024 (section 15). The auditions were in the 5th district at the headquarter of "Société Chimique de France". Thanks to SCF for hosting us during two weeks. The results for these sessions can be consulted there: https://sncs.fr/2024/03/05/concours-cnrs-2024/#S15

First barbecue of the year with the MATRIX team!

25/04/2024

Our latest paper was promoted by CNRS chimie

Our latest paper (DOI : 10.1021/acsnano.3c12799) on prismatic confinement was promoted by CNRS Chimie and LPS: 

CNRS Chimie: https://www.inc.cnrs.fr/fr/cnrsinfo/controler-le-desordre-dans-lauto-assemblage-de-nanoparticules-pour-ameliorer-leurs

LPS: https://equipes2.lps.u-psud.fr/matrix/guiding-nanoparticle-assembly-into-complex-structures/

16/04/2024

Prismatic Confinement Induces Tunable Orientation in Plasmonic Supercrystals

21/03/2024 Throughout history, scientists have looked to Nature for inspiration and attempted to replicate the intricate complex structures formed by self-assembly. In the context of synthetic supercrystals, achieving such complexity remains a challenge due to the highly symmetric nature of most nanoparticles (NPs). Previous works have shown intricate coupling between the self-assembly of NPs and confinement in templates such as emulsion droplets (spherical confinement) or tubes (cylindrical confinement). This study focuses on the interplay between anisotropic NP shape and tunable “prismatic confinement” leading to the self-assembly of supercrystals in cavities featuring polygonal cross-sections. A multiscale characterization strategy is employed to investigate the orientation and structure of the supercrystals, locally and at the ensemble level. Our findings highlight the role of the mold interface in guiding the growth of distinct crystal domains: each side of the mold directs the formation of a monodomain that extends until it encounters another, leading to the creation of grain boundaries. Computer simulations in smaller prismatic cavities were conducted to predict the effect of increased confinement. Comparison between prismatic confinement and cylindrical confinement shows that flat interfaces are key to orient the growth of supercrystals. This work shows a method of inducing orientation in plasmonic supercrystals and controlling their textural defects, thus offering insight into the design of functional metasurfaces and hierarchical structured devices. See article @ ACS Nano: DOI: 10.1021/acsnano.3c12799

Welcome Nika!

01/02/2024 I started thinking about chemistry when I participated in international chemistry Olympiad, (ICHO) 48 where I became fascinated about science. Therefore, I studied chemistry at San Diego State University Georgia and obtained bachelor’s degree there. Then, I decided to divert study direction towards physical chemistry and materials science that is why I applied to SERP master program at Université Paris-Saclay. Currently, I am involved in M2 internship in LPS where I work for the project “Templated Colloidal Crystals with Collective Optical or Magnetic Properties” which is supervised by Dr.Cyrille Hamon and Dr.Marianne Imperor-Clerc.   Currently, I am particularly interested in self-assembly of nanoparticles and how to utilize the properties of nanoparticles in the field of plasmonics/photonics and imaging.

Happy 2024

image credit: https://doi.org/10.1073/pnas.2311957120

Cyrille defended his HDR

07/09/2023 Cyrille succesfully defended his accredidation to supervize research (HDR). Thanks to jury (from left to right): Stéphane Parola (ENS Lyon) Fabienne Testard (CEA Saclay) Hynd Remita (ICP) David Portehault (LCMCP) Mona Tréguer-Delapierre (ICMCB) Emmanuelle Lacaze (INSP)

Plasmonic NPs Synthesis by colloidal chemistry

Selection of TEM images of Au or Au@Ag NPs with various morphology obtained in the team. The colors distinct series of nanocrystal: gold bipyramids of different size (purple), Au@Ag nanorods of varying shell thickness (red), Au@Ag bipyramids of varying shell length (green).

Shaping nanomaterials

Construction of nanoscale devices is a crucial step toward the sucess of nanotechnologies in a variety of fields. Although construction by addition of individual building blocks might appear impossible without using nanomachines, it can actually be carried out by simply exploiting the different magnitude of attractive and repulsive interaction forces at the nanoscale. For example, gravity is negligible for nanoparticles, but other forces become dominant and require the nanoparticles to be coated with selected molecules. Thus, one can simply let the solvent evaporate and wait the nanoparticles to organize into ordered structures without any intervention. Such strategy is one of the core of the concept of self-assembly.

Gold and silver nanoparticles

Plasmonic nanoparticles (Au and Ag) have been object of fascination since ancient time for the preparation of stained glass. Such elementary building block are extremly robust and their use in monuments stand the test of time. A not too far example from the laboratory is the "Sainte-Chapelle du Palais" at "l'île de la cité" in Paris (see image, wikipédia). This phenomenon, commonly witnessed by everyone, originates from the plasmonic properties of metallic nanoparticles. 

Optical properties of nanoparticles

The strong optical properties of nanoparticles (e.g. plasmonic or semiconducting) can be tuned across the visible to the mid infra-red range by modifying their size and shape. When such nanoparticles are organized in ensembles, collective properties are obtained that differ from those of individual particles and the resulting optical properties can be further tuned and even amplified. In particular, plasmon coupling in small gaps (1–10 nm) between plasmonic nanoparticles results in intense electric fields (i.e.,hot-spots) that can be exploited for many purposes, such as sensing, biomaterials, metamaterials design, switching devices, and so forth.

Use of light to study nanoparticles self assembly

We use UV/Vis spectrometry and X-ray scattering tecniques (SAXS) to study nanoparticles super-structures. The structural study of the material is the first step before understanding its overall properties and considering applications. SAXS is an experimental technique used to study the structural properties of materials and gives information on the size and orientation of the nanoparticles, their arrangement, the characteristic interdistances and the possible long-range organization. In a scattering experiment, ordered phases give diffraction signals that are called Bragg peaks. Analysis of such signals requires adapting standard methods of crystallography to the nanoscale, as the relevant length scale is much larger than the atomic scale. UV/Vis spectrometry is used complementary to measure the collective optical properties. Both techniques can be used in situ to study self assembly's pathways. 

Mesoporous materials

A mesoporous material is a material containing pores with diameters between 2 and 50 nm. We are devising materials containing a mesoporous architecture to enhance size and shape selectivity for guest molecules or to template nanoparticles synthesis. 

Alumni

Rahul Nag (post-doc) - 2023-2024

Rahul Nag obtained his PhD from IIT Bombay under the supervision of Chebrolu Pulla Rao in Bio-Inorganic Chemistry Laboratory. He worked on the surface functionalization of nanostructures by organic conjugates specially calixarenes which involved applications in sensing, cancer cell killing, catalysis. He did a one-year post-doctoral research in CBMN/University of Bordeaux under the supervision of Emilie Pouget in the Chiral Molecular Assemblies Group led by Reiko Oda. He is joined the Laboratoire of Physique des Solides as a postdoctoral researcher with Cyrille Hamon. Currently, his interest focuses on the synthesis of gold nanostructures controlling their shapes and sizes for possible application in non-linear optics. He is now doing a postdoc at ITODYS (Université Paris-Cité)

Wajdi Chaâbani (post-doc) - 2020-2022

Wajdi Chaâbani obtained his Ph.D. from the University of Technology of Troyes (France) and the University of Sciences of Sfax (Sfax, Tunisie) under the supervisions of Jérôme Plain and of Abdallah Chehaidar in July 2019. He was a postdoctoral researcher in IEMN Laboratory (Lille, France) from September 2019 to August 2020. He then joined the Laboratoire de Physique des Solides in Orsay (France) as postdoctoral researcher. Currently, his interest focuses on self-assembling plasmonic nanoparticles in confinement. The nanostructuration will be resolved at the single supercrystal level using an innovative Small Angle X-ray Scattering (SAXS) setup developed on a synchrotron beamline.(SWING, @SOLEIL). He is now doing a postdoc at ITODYS (Université Paris-Cité)

Jianan Qian (M2) - 2022

I obtained my Bachelor of Engineering in Nano Materials and Technology from Soochow University in China. During my undergraduate study, I worked on several projects related to nanoscaled functional materials for energy conversion and storage under the supervision of Prof. Yanguang Li.   I am now the M2 student from Erasmus Mundus Joint Master program: SERP+. Currently, I am working on my thesis project about self-assembly of colloidal liquid crystal in levitation under the supervision of Dr. Cyrille Hamon and Dr. Erwan Paineau.

Jieli Lyu (PhD) - 2018-2022

Jieli Lyu completed her M.S. degree at the Key Laboratory of Applied Surface and Colloid Chemistry of Shaanxi Normal University. She studied under the supervision of Prof. Junxia Peng and Prof. Yu Fang, and her main research topics were (1) synthesis and characterization of amphiliphic compounds; (2) formulation and performances of the emulsions; (3) emulsion-templated preparation of porous materials and their catalytic performance. She started her PhD in october 2018. Her research interest focuses on nanomaterials with a multiscale organization as well as shedding light on the self-assemblies pathways using light scattering techniques.

Samantha Roque (M2) - 2021

Samantha Roque earned her Bachelor of Science in Chemistry (2017) and in Materials Science Engineering (2018) from Ateneo de Manila University in the Philippines. She worked on printable carbon composites and biosilica inks for perovskite solar cells under Erwin P. Enriquez, Ph.D.    She is now doing her master's degree under the Erasmus Mundus Joint Master Degree SERP+. She is at present doing her internship on Anisotropic plasmonic-semiconductor nanocomposites for photocatalytic applications which is a joint project between the “Institut de Chimie Physique” and the “Laboratoire de Physique des Solides” supervised by Cyrille Hamon Ph.D. and ‪Mohamed Nawfal Ghazzal, Ph.D.     She is now doing a PhD at Université du Sud Toulon Var

  Masa Johar (M1)- 2021

Masa Johar graduated from An-Najah National University, Palestine (2020),  with a bachelor's degree in Applied Chemistry. She joined University of Paris Saclay in September  2020 to start her master's degree within the Chemistry International Track program for two years.   Currently, she is doing her M1 internship on "Colloidal chemistry of plasmonic triangular nanoplatelets" under supervision of Prof. Cyrille Hamon at the Laboratory of Solid Physics (LPS). Her main motivation is to find the best protocol for synthesizing triangular gold nanoparticles.      Finally, she is looking forward to being a highly skilled researcher enthusiastic about supporting advancements in the nanotechnology world, passionate about increasing knowledge to drive growth and needed improvements related to sustainable developments in Energy, Health and Environment.   She is now doing a PhD at Université Paris Saclay

 Kinanti Aliyah (M2)- 2019

Nika Kutalia

I started thinking about chemistry when I participated in international chemistry Olympiad, (ICHO) 48 where I became fascinated about science. Therefore, I studied chemistry at San Diego State University Georgia and obtained bachelor’s degree there. Then, I decided to divert study direction towards physical chemistry and materials science that is why I applied to SERP master program. Currently, I am involved in M2 internship in LPS where I work for the project “Templated Colloidal Crystals with Collective Optical or Magnetic Properties” which is supervised by Dr.Cyrille Hamon and Dr.Marianne Imperor-Clerc.   Currently, I am particularly interested in self-assembly of nanoparticles and how to utilize the properties of nanoparticles in the field of plasmonics/photonics and imaging.

Jaime Gabriel Trazo

Jaime Gabriel Trazo earned his bachelor degrees in Chemistry and in Materials Science and Engineering at the Ateneo de Manila University (2019, 2020), where he worked on formulating green silver nanoparticle inks for printed electronics and on nanocellulose synthesis, under Dr. Jose Mario Diaz and Dr. Erwin Enriquez. He was also a National Awardee at the BPI-DOST Science Awards 2019 in the Philippines.   He then pursued his master’s degree under the Erasmus Mundus SERP+ Program. For his M2 internship, he joined the Laboratoire de Physique des Solides, where he works on the self-assembly of nanoparticles into supercrystals with collective optical/magnetic properties, under Dr. Cyrille Hamon and Dr. Marianne Impéror-Clerc. He obtained a grant from the ED2-MIB doctoral school to continue the adventure at LPS in PhD.

Claire Hotton

Claire Hotton obtained her PhD from Sorbonne University under the supervision of Natalie Malikova in PHENIX laboratory. She worked on the structure and properties of hydrogels based on ionene-type cationic polyelectrolytes and clay nanoplatelets. She is now joining the Laboratoire of Physique des Solides as a postdoctoral researcher with Cyrille Hamon and Erwan Paineau. Currently, her interest focuses on the self-assembly of colloidal liquid crystals by acoustic levitation.

Jules Marcone

Jules Marcone graduated in 2022 from the Paris-Saclay University in 2022 with a Magister of Molecular Physicochemistry, focusing on Inorganic, Physical, and Materials Chemistry. During his study, he developed various skills in characterization methods (SAXS, XRD, SEM, etc.), and also in nanoparticle synthesis and self-assembly.   Jules started his PhD in October 2022 under the supervision of Marianne Impéror-Clerc and Cyrille Hamon at the LPS, on the synthesis and self-assembly of nanoparticles focusing particularly on cobalt nanorods, aiming for collective magnetic properties.

Marianne Impéror-Clerc

Marianne Impéror-Clerc has a permanent position at CNRS as ‘directrice de recherche’. She studied Physics at the ENS de Saint-Cloud (1986-1990) where she passed the ‘aggrégation de Physiques’ (1989) before obtaining her PhD (1992) and HdR ‘Habilitation à diriger des recherches’ (2007) at the Université Paris-Sud in Orsay. Her research is devoted to structural studies of self-assembled systems and her favorite experimental tool is Small Angle Scattering using X-rays or neutrons (SAXS and SANS).  For example, for mesoporous materials, the control of the architecture of the porosity allows to optimize transport properties. Main goal is to control the nanostructure during the synthesis of such materials. For this, time-resolved scattering experiments allow to follow in real time the formation of the materials and to elucidate the mechanisms involved. Her research thus lies at the frontier between Soft Matter and Materials Chemistry. She is alos regularly involved in activities about Crystallography for education and the general public (http://www.cristallo2014.u-psud.fr/)

Team MATRIX

Cyrille Hamon

Cyrille Hamon obtained his Ph.D. from the University of Rennes 1 (France) under the supervision of Pascale Even-Hernandez and Valérie Marchi in 2013. He was a postdoctoral fellow in Luis Liz-Marzán laboratory (CIC Biomagune, Spain) from 2014 to 2016. He then joined the laboratories of Gaëlle Charron and Pascal Hersen (MSC, Université Paris 7) from 2016 to 2017. He has been appointed in 2017 with a permanent CNRS position in the Laboratoire de Physique des Solides in Orsay. His current interest focuses on devising new plasmonic architectures for sensing applications.