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5 sujets /NIMBE/LEDNA

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In situ and real time characterization of nanomaterials by plasma spectroscopy

SL-DRF-24-0388

Research field : Atomic and molecular physics
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Marc BRIANT

Yann LECONTE

Starting date : 01-10-2024

Contact :

Marc BRIANT
CEA - DRF/IRAMIS/NIMBE

01 69 08 53 05

Thesis supervisor :

Yann LECONTE
CEA - DRF/IRAMIS/NIMBE/LEEL

0169086496

Personal web page : https://iramis.cea.fr/Phocea/Membres/Annuaire/index.php?uid=mbriant

Laboratory link : https://iramis.cea.fr/nimbe/ledna/

The objective of this Phd is to develop an experimental device to perform in situ and real time elemental analysis of nanoparticles during their synthesis (by laser pyrolysis or flame spray pyrolysis). Laser-Induced Breakdown Spectroscopy (LIBS) will be used to identify the different elements present and to determine their stoichiometry.

Preliminary experiments conducted at LEDNA have shown the feasibility of such a project and in particular the acquisition of a LIBS spectrum of a single nanoparticle. Nevertheless, the experimental device must be developed and improved in order to obtain a better signal to noise ratio, to decrease the detection limit, to take into account the different effects on the spectrum (effect of nanoparticle size, complex composition or structure), to automatically identify and quantify the elements present.

In parallel, other information can be sought (via other optical techniques) such as the density of nanoparticles, the size or shape distribution.
Porous materials integrated into devices for glycomic analysis in hospitals.

SL-DRF-24-0442

Research field : Chemistry
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Marc MALEVAL

Martine Mayne

Starting date : 01-10-2024

Contact :

Marc MALEVAL
CEA - DRF/IRAMIS/NIMBE/LEDNA

0169084933

Thesis supervisor :

Martine Mayne
CEA - DRF/IRAMIS/NIMBE

01 69 08 48 47

Personal web page : https://iramis.cea.fr/Phocea/Membres/Annuaire/index.php?uid=mmaleval

Laboratory link : https://iramis.cea.fr/NIMBE/LEDNA/

Glycomics involves identifying oligosaccharides (OS) present in a biological fluid as a source of biomarkers for diagnosing various pathologies (cancers, Alzheimer's disease, etc.). To study these OS, sample preparation involves 2 key phases, enzymatic cleavage (breaking the bond between OS and proteins) followed by purification and extraction (separation of OS and proteins). However, the materials currently used in the protocols impose numerous manual and time-consuming steps, incompatible with high-throughput analysis.

In this context, the LEDNA laboratory specialized in materials science has recently developed a sol-gel process for the manufacture of Hierarchical Porosity Monoliths (HPMs) in miniaturized devices. These materials have provided a proof of concept demonstrating their value for the second stage of glycomic analysis, i.e. the purification and extraction of oligosaccharides. The LEDNA is now looking to improve the first step, corresponding to enzymatic cleavage, which has become a limiting factor in the glycomics analysis process. Functionalization of porous materials, in particular HPMs, with enzyme would enable simple sample preparation in just a few hours with a single step.

The aim of this thesis is therefore to show that the use of porous materials with a dual function - catalytic and filtration - applied to the preparation of samples for glycomic analysis is a relevant means of simplifying and accelerating glycomic analysis, as well as employing them in hospital-related studies to identify new biomarkers of pathologies.

The research project will involve developing a device incorporating porous materials with catalytic and filtration functions. Several aspects will be addressed, ranging from the synthesis and shaping of these materials to characterization of their textural and physico-chemical properties. Particular emphasis will be placed on enzyme immobilization. The most promising prototype(s) will be evaluated in a glycomic analysis protocol, verifying the oligosaccharide profiles obtained from human biofluids (plasma, milk). Physico-chemical characterization will involve a variety of techniques (SEM, TEM, etc.), as well as characterization of porosity parameters (nitrogen adsorption, Hg porosimeter). Oligosaccharides will be analyzed by high-resolution mass spectrometry (mainly MALDI-TOF).

For this multidisciplinary thesis project, we are looking for a student chemist or physical chemist, interested in materials chemistry and motivated by the applications of fundamental research in the field of new technologies for health. The thesis will be carried out in two laboratories, LEDNA for the materials part and LI-MS for the use of materials in glycomics analysis. The research activity will be carried out at the Saclay research center (91).
Nanodiamond-based porous electrodes: towards photoelectrocatalytic production of solar fuels

SL-DRF-24-0426

Research field : Physical chemistry and electrochemistry
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Jean-Charles ARNAULT

Hugues GIRARD

Starting date : 01-10-2024

Contact :

Jean-Charles ARNAULT
CEA - DRF/IRAMIS/NIMBE/LEDNA

01 68 08 71 02

Thesis supervisor :

Hugues GIRARD
CEA - DRF/IRAMIS/NIMBE/LEDNA

0169084760

Personal web page : https://iramis.cea.fr/nimbe/Phocea/Membres/Annuaire/index.php?uid=jarnault

Laboratory link : https://iramis.cea.fr/nimbe/ledna/

Among nanoscale semiconductors, nanodiamonds (ND) have not been really considered yet for photoelectrocatalytic reactions in the energy-related field. This originates from the confusion with ideal monocrystalline diamond featuring a wide bandgap (5.5 eV) that requires a deep UV illumination to initiate photoreactivity. At the nanoscale, ND enclose native defects (sp2 carbon, chemical impurities such as nitrogen) that can create energetic states in the diamond’s bandgap decreasing the light energy needed to initiate the charge separation. In addition, the diamond electronic structure can be strongly modified (over several eV) playing on its surface terminations (oxidized, hydrogenated, aminated) which can open the door to optimized band alignments with the species to be reduced or oxidized. Combining these assets, ND becomes competitive with other semiconductors toward photoreactions. The aim of this PhD is to investigate the ability of nanodiamonds in reducing CO2 through photoelectrocatalysis. To achieve this goal, electrodes will be made from nanodiamonds with different surface chemistries (oxidized, hydrogenated and aminated), either using a conventional ink-type approach or a more innovative one that results in a porous material including nanodiamonds and a PVD-deposited matrix. Then, the (photo)electrocatalytic performances under visible illumination of these nanodiamond-based electrodes toward CO2 reduction will be investigated in terms of production rate and selectivity, in presence or not of a transition metal macrocyclic molecular co-catalyst.
Custom synthesis of diamond nanoparticles for photocatalytic hydrogen production

SL-DRF-24-0432

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Hugues GIRARD

Jean-Charles ARNAULT

Starting date : 01-10-2024

Contact :

Hugues GIRARD
CEA - DRF/IRAMIS/NIMBE/LEDNA

0169084760

Thesis supervisor :

Jean-Charles ARNAULT
CEA - DRF/IRAMIS/NIMBE/LEDNA

01 68 08 71 02

Personal web page : https://iramis.cea.fr/Phocea/Membres/Annuaire/index.php?uid=hgirard

Laboratory link : https://iramis.cea.fr/NIMBE/LEDNA/

Our recent results show that nanodiamond can also act as a photocatalyst, enabling the production of hydrogen under solar illumination [1]. Despite its wide band gap, its band structure is adaptable according to its nature and surface chemistry [2]. Moreover, the controlled incorporation of dopants or sp2 carbon leads to the generation of additional bandgap states that enhance the absorption of visible light, as shown in a recent study involving our group [3]. The photocatalytic performance of nanodiamonds is therefore highly dependent on their size, shape and concentration of chemical impurities. It is therefore essential to develop a "tailor-made" nanodiamond synthesis method, in which these different parameters can be finely controlled, in order to provide a supply of "controlled" nanodiamonds, which is currently lacking.

The aim of this PhD is to develop a bottom-up approach to nanodiamond synthesis using a sacrificial template (silica beads or fibers) to which diamond seeds < 10 nm are attached by electrostatic interaction. The growth of diamond nanoparticles from these seeds will be achieved by exposing these objects to a microwave-enhanced chemical vapor deposition (MPCVD) growth plasma, allowing very fine control of (i) the incorporation of impurities into the material (ii) its crystalline quality (sp2/sp3 ratio) (iii) its size. This growth facility, which exists at the CEA NIMBE, is used for the synthesis of boron-doped diamond core-shells [4]. In the second part of the thesis, an innovative process (patent pending) is implemented to achieve MPCVD growth of diamond nanoparticles by circulating the sacrificial templates in a gas stream. During this work, different types of nanodiamonds will be synthesized: intrinsic nanoparticles (without intentional doping) and nanoparticles doped with boron or nitrogen.

After growth, the nanoparticles will be collected after dissolution of the template. Their crystal structure, morphology and surface chemistry will be studied at CEA NIMBE by scanning electron microscopy, X-ray diffraction and Raman, infrared and photoelectron spectroscopy. A detailed analysis of the crystallographic structure and structural defects will be carried out by high-resolution transmission electron microscopy.

Nanodiamonds will then be surface-modified to give them colloidal stability in water. Their photocatalytic performance for hydrogen production will be evaluated in collaboration with ICPEES (Strasbourg University).


References
[1] Patent, Procédé de production de dihydrogène utilisant des nanodiamants comme photocatalyseurs, CEA/CNRS, N° FR/40698, juillet 2022.
[2] Miliaieva et al., Nanoscale Adv. 2023.
[3] Buchner et al., Nanoscale (2022)
[4] Henni et al., Diam. Relat. mater. (under review)
Exploring the reactivity of oxide based catalysts by radiolysis

SL-DRF-24-0239

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l’Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Nathalie HERLIN

Sophie LE CAER

Starting date : 01-10-2024

Contact :

Nathalie HERLIN
CEA - DRF/IRAMIS/NIMBE/LEDNA

0169083684

Thesis supervisor :

Sophie LE CAER
CNRS - DRF/IRAMIS/NIMBE/LIONS

01 69 08 15 58

Personal web page : https://iramis.cea.fr/Pisp/sophie.le-caer/

Laboratory link : https://iramis.cea.fr/nimbe/LIONS

More : https://iramis.cea.fr/nimbe/LEDNA

In the context of the search for processes that are less polluting and more energy-efficient than current processes, it is interesting to produce high-stake molecules such as C2H4 by developing alternative synthesis routes to steam cracking, which is used in the majority of cases, but is energy-intensive and based on fossil resources. Processes such as photocatalysis, which relies on the use of light energy, seem an attractive way of generating these molecules of interest. In this context, we have already shown that the use of TiO2-based photocatalysts decorated with copper particles enables the production of ethylene from an aqueous solution of propionic acid, with a selectivity (C2H4/other carbonaceous products) of up to 85%.

However, photocatalysis kinetics can be slow, and it can take a long time to identify the best catalysts or catalyst/reagent pairs for a given reaction. So, in order to determine whether radiolysis, which relies on the use of radiation to ionize matter, can be an effective method of screening catalysts, initial experiments have already been carried out on catalyst (TiO2 or Cu TiO2)/reagent (propionic acid more or less concentrated) pairs, previously studied in photocatalysis. Initial results obtained by radiolysis are encouraging. In these experiments, only dihydrogen production was measured. A significant difference was observed in this production depending on the system: it was high during radiolysis of propionic acid with TiO2 nanoparticles, and significantly lower in the presence of Cu TiO2 nanoparticles, suggesting a different reaction path in the latter case, in line with observations made during photocatalysis experiments.

The aim of this thesis work will be to extend these initial results by synthesizing nanoparticles (catalysts), preparing reagent/catalyst mixtures, then irradiating them and measuring the various gases produced by gas-phase micro-chromatography, with special attention on ethylene. Particular attention will be paid to determining the species formed, especially transient ones, in order to ultimately propose reaction mechanisms accounting for the differences observed for the different reagent/catalyst pairs. Comparisons will also be made with results obtained by photocatalysis.

 

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