Description du sujet de thèse

Optical sensor for organophosphorus pesticides detection and immobilization

Contexte de travail

Half of the work will be carried out at the Institut de Physique de Nice (INPHYNI, Université Côte d'Azur, CNRS UMR 7010, 17 rue Julien Lauprêtre, 06200 Nice), within the "Magnetorheology and Nanomaterials" team. This institute in Nice includes 175 researchers, faculty members, engineers, technicians, and PhD students, whose activities are organized into three main research areas and 11 teams working on photonics, waves and quantum physics, as well as nonlinear physics, complex fluids, and biophysics.
PhD Project Description

Organophosphorus (OP) compounds are a class of chemicals containing phosphorus atoms bonded to organic groups and oxygen. These compounds are widely used in agriculture as pesticides, as well as in industrial applications such as flame retardants, plasticizers, and lubricants. Highly toxic, they can cause neurotoxicity by inhibiting acetylcholinesterase enzyme activity. Additionally, OPs persist in the environment, contaminating soil, water, and air, leading to long-term ecological damage.

Traditionally, OP analysis relies on complex, expensive, and time-consuming chromatographic techniques (HPLC, GC), which require sample transportation to specialized laboratories, posing challenges for sample preservation and preventing in-situ measurements. To address this limitation, there is growing interest in developing detection methods for portable and cost-effective devices that enable rapid on-site OP compound detection. Among these methods, enzyme-based sensors (using acetylcholinesterase, alkaline phosphatase, organophosphorus hydrolase, etc.) have been extensively studied. However, they cannot fully replace chromatographic analysis due to their limited sensitivity and selectivity. Additionally, enzyme sensor efficiency is affected by pH, temperature, and humidity, making them unsuitable for some applications.

Non-enzymatic electrochemical sensors have attracted attention due to their low cost, rapid analysis time, and very low detection limits. Their sensitivity mainly depends on the conductive properties of the material used. Materials such as graphene, carbon nanotubes, metal and metal oxide nanoparticles, nanopolymers, metal-organic frameworks (MOFs), and metal-imprinted polymers (MIPs) have been investigated. However, further improvements are needed, particularly to enhance sensitivity, selectivity, and the stability of electrochemical performance.

Optical signals from nanomaterials have also been explored as a powerful alternative for OP detection. Enzyme-based optical biosensing relies on measuring the optical signal of a substrate (nanomaterial) in the presence and absence of OP. In the absence of OP, the substrate undergoes hydrolysis, leading to an optical signal response. When OPs are present, enzymatic activity is inhibited, preventing substrate hydrolysis and producing the opposite optical response. Depending on the substrate, different techniques such as photoluminescence, fluorescence, chemiluminescence, electrochemiluminescence, or colorimetry can be used.
Objectives

The aim of this PhD project is to develop an optical probe for the rapid detection of OPs with sensitivity at least comparable to current, time-consuming methods. The project involves designing an optical detector based on optical fiber co-functionalized with metal-organic frameworks (MOFs) as absorbers and/or gold, silver, or other metal nanoparticles to enhance plasmonic Raman signals. The use of colorimetric methods within the UV-Vis spectroscopy range is also considered. Another objective is to understand the nature of interactions between selected OP molecules and MOF-type substrates, metal nanoparticles, and/or optical fiber.
Project Plan

Selection of OP compounds and MOF-type materials

Synthesis of MOFs with and without metal nanoparticles, followed by OP impregnation

Determination of physicochemical properties to select the optimal sensing method

Investigation of interactions between tested OPs and substrates

Measurement, analysis, and evaluation of the fabricated sensor's performance

Experimental Methods

X-ray diffraction (XRD)

IR/Raman spectroscopy

Electron spectroscopy (absorption, emission)

Gas chromatography-mass spectrometry (GC-MS)

Microscopic techniques (SEM)

Elemental analysis

Zeta potential measurement

³¹P nuclear magnetic resonance (NMR)

Surface area analysis (BET)

This project aims to provide an innovative and efficient alternative for the rapid and reliable detection of organophosphorus pesticides, integrating advanced optical sensing technologies and nanomaterials.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

As part of a contract funded by Horizon Europe under the Doctoral Networks calls of the Marie Sklodowska-Curie actions, the PhD candidate will be supervised by two academic tutors from two different universities and an industrial mentor.

For this four-year PhD position, the candidate will conduct half of their research at the Institute of Low Temperature and Structure Research, Polish Academy of Sciences in Poland, under the supervision of Dr. Maciej Ptak. The industrial mentor is KLEARIA (France), where the PhD candidate will also gain research experience.

Additionally, two one-month research stays are planned during the PhD: the first at Tampere University (Finland) and the second at Nazarbayev University (Kazakhstan).