Description of the thesis topic

The detection and quantification of water either as trace in liquids, or as relative humidity (RH) in air are highly critical for industrial process controls, solvent manufacture, food and drug storage, lithium-ion batteries life extension, and indoor air quality improvement. In the last years, photoluminescent (PL) solid sensors, that can respond to the presence of water with a detectable change in their PL signal, have been considered as an attractive potential alternative to traditional analytical technics due to their faster response, higher sensitivity and ability of in situ and real-time detection. However, new sustainable, reusable and recyclable PL water sensors are highly desirable, to be able to use them in real-world applications.

This PhD project aims at investigating the potentiality of new PL anhydrous alkali salts of the [SbW6O24]7- (SbW6) lanthanide-free polyoxometalate to sense RH in the air and trace amounts of water in organic solvents. These materials can be elaborated in water via low-energy and eco-friendly procedures. Upon exposure to water molecules, they rehydrate quickly causing strong PL quenching effects. The variation of the light signal is correlated to the water content of the medium, which these phases detect with high sensitivity and selectivity. The PL-active anhydrous phases are regenerable after use, and they can be easily recycled via a one-step procedure in water.

Further investigations are required to streamline the complex reactivity of these materials towards water, and to ultimately understand their detection mechanism. The objectives of this research project are:
- to enrich this class of materials by performing a prospective research of new alkali SbW6 salts whose chemical composition will vary with the nature and the ratio of the alkali ions, and with their degree of hydration.
- to characterize by advanced structural analyses methods and DFT calculations the H-bonding networks involving water molecules and SbW6 units, responsible of PL quenching effects.
- to optimize the recycling procedures of the materials.
- to streamline the hydration/dehydration processes of these compounds, by investigating their temperature and humidity-dependent thermodynamic stability domains, and by studying the kinetics of phase conversions.
- to characterize the photophysical properties (absorption and emission) of the anhydrous phases as such or incorporated into polymer matrices in order to elaborate new water sensing devices with improved applicability. These studies will allow correlating composition, crystal structure, particle size and morphology of the salts with their water sensing performances.

The profile sought is that of a young scientist holding or in the process of obtaining a Master's degree (or equivalent) focused on materials or/and solid-state chemistry, extremely motivated by exploratory synthesis, and possessing a strong interest in interdisciplinary subjects.

Work Context

This PhD work is a part of the ALPS-Water project (ANR-24-CE08-4167) funded by the French National Research Agency which brings together three French laboratories: the Institute of Materials of Nantes Jean Rouxel (IMN) from Nantes University, and the Separative Sciences and Methods (SMS) Laboratory and the Polymers, Biopolymers, Surfaces (PBS) Laboratory from the University of Rouen. IMN is the host laboratory for this research project which is a joint CNRS-Nantes University research unit (UMR 6502, http://www.cnrs-imn.fr), composed of more than 200 staff, including about 120 permanent and 80 PhD students and postdocs. The recruited PhD student will be part of the MIOPS (Innovative Materials for Optics, Photovoltaics and Storage) team, which has internationally renowned expertise in the field of photoactive materials.

This research project offers the candidate the opportunity to acquire knowledge and multidisciplinary know‐how in inorganic chemistry, materials science, physico-chemistry of hydrates, and photophysical characterizations. In addition, the candidate will gain experience in a wide variety of characterization techniques available at IMN through the PLASSMAT platform (https://plassmat.cnrs-imn.fr/), and in complementary techniques available at SMS for the characterization of hydrates.

Furthermore, he will have the opportunity to mentor Master students and to present his results in national and international congresses.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

The PhD candidate will undertook several short research stays at SMS. Travel to project partners for scientific meetings is also planned.
Classical risks linked to a research project in the field of materials science and chemistry.