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Reference : UMR6252-JULCAR-001
Workplace : CAEN
Date of publication : Monday, April 27, 2020
Scientific Responsible name : Julien Cardin
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
The criticality of rare earth elements, which is due to a combination of vulnerabilities related to their quantity, environmental issues and their supply, is a major strategic issue due to their unique properties. Rare earths indeed have properties which leads to their use in various fields such as chemistry (cracking of petroleum, catalytic converters), mechanics (increase in hardness), magnetism (of very powerful permanent magnets), optics (coloring, fluorescent lighting, laser, optical amplifier). In the field of optics in particular, the search for stable materials without rare earth, with efficient luminescence and which can be shaped is therefore a major challenge.
The objective of this thesis is to investigate the optical properties of a new class of rare earth free crystalline organic-inorganic hybrid luminescent materials, the metallophosphonate family synthesized from original phosphonic acids. This family of hybrid materials is studied because it offers the possibility to modulate the nature and the properties of each sub-element constituting it and thus obtaining a combination of these properties. The targeted luminescent hybrid materials must contain no rare earths and exhibit high thermal, chemical and photophysical stability, high quantum efficiency and specific spectral emission. To achieve this objective, we will study in particular hybrid materials of the metallophosphonate family which have induced emission (AIE: Aggregation-Induced Emission)  or exacerbated emission (AEE: Aggregation-Enhanced Emission)  properties by a phenomenon of physical aggregation.
These phenomena concern the appearance or the increase of the intrinsic light emission of a luminescent sub-element by the reduction of its number of degrees of freedom by the confinement of the molecule within the superstructure . It is in this perspective that we propose to develop this research project selected and funded by the Labex EMC3 (Energy Materials and Clean Combustion Center).
 Luo, Xie, Lam, Cheng, Chen, Qiu, Kwok, Zhan, Liu, Zhu, Tang, Chem. Commun., 2001, 1740-1741
 Chang, Jiang, He, Chen, Yang, Lu, Kwok, Zhao, Qiua, Tang, Chem. Commun., 2013, 49, 594-596
 Bloyet, Rueff, Cardin, Caignaert, Doualan, Lohier, Jaffres, Raveau, Eurjic, 2018, 3095-3103.
We are looking for a motivated candidate to carry out this multidisciplinary subject in collaboration with researchers from laboratories involved in this project. The candidate must hold a Research Master in Solid State Physics or Materials Science or hold an engineering degree in these fields. Experience in optical spectroscopy of materials would be a significant asset as well as a skills in written and spoken English.
This thesis project is part of a research project between several research laboratories supported by the Labex EMC3 which, in addition to the CIMAP laboratory, includes two other partner laboratories. This project is articulated in several tasks: the preparation of organic precursors, the hydrothermal synthesis of luminescent hybrid materials, the structural resolution of the compounds, the study of the optical properties of the selected materials. This last task will be the main activity of this thesis. It will consist of carrying out the study of the optical properties of post hydrothermal synthesis materials and that of the shaped materials. The materials obtained in the form of single-phase powders will be the subject of a conventional optical spectroscopy study comprising a spectral characterization of the refractive index, absorption, excitation and emission. Luminescence decay and quantum yield measurements will allow the selection of hybrid compounds with high quantum yield. Once formed, these materials will again be characterized optically. In addition, this work will be based on the strong collaboration with the doctoral student recruited by one of the partner laboratories who will mainly carry out hydrothermal synthesis, physico-chemical and structural characterizations. Thus the thermal and chemical stability and the luminescent properties will be compared with the results of the physico-chemical and structural study and the results of the theoretical study of the electronic structure of materials by ab initio methods. This will allow a better understanding of the phenomena involved in exalted luminescence; and possibly to carry out future optimizations.
The hired candidate will also participate in the drafting of Labex interim reports, presentation in the framework of conferences and scientific articles.
The candidate will carry out his thesis at the Research Center on Ions, Materials and Photonics (CIMAP CNRS UMR6252 ENSICAEN UNICAEN CEA) which is internationally recognized and which brings together physicists of solid and diluted matter. This project is part of a scientific collaboration existing for 5 years between the laboratories of the consortium with the CIMAP, which concerns the study of the luminescence properties of metallophosphonates.
Constraints and risks
Short stay in France and abroad are planned within the framework of congresses or thematic schools.
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