Exploring the structural properties and enhancement of Opto-electrical investigations for the synthesized epoxy based polymers with local nanoscale structures

Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA) were prepared using 4, 4′-diaminodiphenyl (44′DDS) and 3, 3′-diaminodiphenyl (33′DDS) sulfone diamines crosslinking hardeners. The structural, linear optical and mechanical properties of the investigated sample were analysed. Dynamic Mechanical Thermal Analysis and wide-angle x-ray diffraction were conducted to select a candidate presenting interesting thermo-mechanical properties and particular nanostructures embedded in an amorphous matrix. Our choice is therefore focused on DGEBA/33′DDS polymer for which, rocking curve measurements revealed the existence of two principal reflecting planes inclined to each other by about 0.27°. To highlight the potential effect of these interfaces, Thermally Stimulated Depolarization Current (TSDC) and Time Domain Spectroscopy measurements have been carried out. The application of the windowing polarization TSDC technique, in DGEBA/33′DDS polymer sample, gives an almost linear variation of the activation energies in the range between 3.65 and 4.09 eV. To our knowledge, this is the first study concerning epoxy polymers in which activation energies associated to ρ interfacial charge relaxations are calculated. To study the effect of the interfaces and trapped charge carriers, correlated by the angle x-ray diffraction measurements, the optical parameters were investigated. Our contribution will open a new avenue for developing the DGEBA/33′DDS polymer sustainable candidate in optoelectronic engineering applications

Capteurs gravimétriques et électrochimiques et leurs applications dans le domaine de la santé et de l'environnement : défis et solutions

Over the past decades, there has been a skyrocketing demand for reliable, ultra-sensitive, and low-cost tools capable of identifying and quantifying a considered analyte (or a family of analytes) in a complex environment. Chemosensors and biosensors can meet these needs and respond to the strict requirements of two key domains: environment and health. My research concerns the design of electrochemical and surface acoustic wave sensors for the detection of biological entities (DNA and proteins) and various types of environmental pollutants (pesticides, heavy ions, etc.). Depending on the analyte to be detected, we have optimized the functionalization technique of the sensors' surfaces (molecular printing, self-assembled layers, or physical adsorption) to ensure the robustness and selectivity of the designed devices. In addition, and to avoid experimental bias, we have quasi-systematically used dual transduction (electrochemistry/gravimetry or electrochemistry/ELISA).While it is indisputable that sensor technology has reached maturity, there are still several challenges to be met before these tools become THE analytical devices of choice for ultrasensitive and specific detection of chemical and biological species.Les dernières décennies ont vu émerger une forte demande d’outils fiables, ultrasensibles et peu coûteux permettant d’identifier et de doser des analytes (ou une famille d’analytes) dans un milieu complexe. La technologie des capteurs chimiques et biologiques s’est ainsi développée pour accompagner ces besoins et répondre aux exigences sociétales de deux secteurs clés : l'environnement et la santé. C’est dans ces deux domaines que s’inscrivent mes recherches dédiées à la conception et à la réalisation de capteurs électrochimiques et à ondes acoustiques de surface pour la détection d'espèces biologiques (ADN et protéines) et de divers types de polluants environnementaux (pesticides, ions lourds, etc.). Les techniques de fonctionnalisation des surfaces des capteurs (impression moléculaire, couches auto-assemblées, adsorption physique) ont été à chaque fois optimisées en fonction de l’analyte à détecter pour s’assurer de la robustesse et de la sélectivité du capteur réalisé. Par ailleurs, et pour s’affranchir de biais expérimentaux, nous avons quasi-systématiquement utilisé une double transduction (électrochimie / gravimétrie ou électrochimie / ELISA).S’il est indéniable que la technologie des capteurs a beaucoup gagné en maturité, il reste néanmoins plusieurs défis à relever pour que ces outils deviennent LES dispositifs analytiques de choix pour la détection ultra-sensible et spécifique d'espèces chimiques et biologiques dans un milieu donné

Surface acoustic wave sensors: From design to chemical and biological applications

International audienc

Editorial to the Special Issue SELSA: “Sensors for Environmental and Life Science Applications”

International audience“Warn, inform, and prevent” are three essential elements to remember when designing sensors for real-time and in situ monitoring of organic, inorganic, and macromolecular compounds as well as micro-nanoparticles and microorganisms [...

Synthesis, structural and microstructural study of new FeNa0.5H1.5MoO5 hybrid material for highly efficient energy storage hybrid systems

International audienc

Novel Approach for Modeling an Ionic Imprinted Polymer Based SAW Sensor with COMSOL Multiphysics

Modeling a Surface Acoustic Wave (SAW) sensor response as a chemosensor and not only as just an electronic transducer was performed with COMSOL Multiphysics. For this study, the SAW’s sensing area was functionalized with an ionic imprinted polymer (IIP), designed for the selective detection of lead ions. The idea consists in subdividing the IIP into elementary blocks whose physical properties can be modified separately. Three configurations have been envisaged: the IIP before and after lead ions extraction and the non-imprinted polymer (NIP). The generation of shear-horizontal waves on LiTaO3 piezoelectric substrate is confirmed by recording the displacement amplitude versus time, according to the three space directions. The sensors sensitivity is estimated from the delays induced by the incorporation of the lead ions in the IIP layer. To the best of our knowledge, this approach has never been presented in the literature

Modelling and simulation of SAW delay line sensors with COMSOL Multiphysics

International audienceThis study concerns 2D and 3D Finite Element Method (FEM) simulation of surface acoustic wave (SAW) sensors using COMSOL Multiphysics software. SAW device has been designed on piezoelectric substrate; 36° rot lithium tantalate (LiTaO3). Simulations were made on well-known structure to ensure the concordance between 2D and 3D models, and to define a 2D one that can account for and predict the electrical behaviour of SAW transducers for the future optimizations. The results show good agreement between numerical simulation and experimental S21 spectra. Accordingly, we can use the 2D built model for simulations intended to optimize the structure of devices, mainly for increasing their sensitivity

Ultra-sensitive selective detection of HopQ protein as a biomarker for Helicobacter pylori bacteria by an electrochemical voltammetric sensor

Background Helicobacter pylori (H. pylori) is a highly contagious pathogenic bacterium that can cause gastrointestinal ulcers and may gradually lead to gastric cancer. H. pylori expresses the outer membrane HopQ protein at the earliest stages of infection. Therefore, HopQ is a highly reliable candidate as a biomarker for H. pylori detection in saliva samples. Materials and Methods: An H. pylori immunosensor is developed based on detecting HopQ as a biomarker in saliva by a screen-printed carbon electrode (SPCE) modified with MWCNT-COOH decorated with gold nanoparticles (AuNP). The HopQ antibodies are grafted on the SPCE/MWCNT/AuNP surface using EDC/S-NHS chemistry. The sensor performance is investigated by various methods and H. pylori detection performance in spiked saliva samples is evaluated by square wave voltammetry. Results: The sensor is suitable for HopQ detection with high sensitivity and excellent linearity in the 10 pg/mL - 100 ng/mL range and with a 10 pg/ml limit of detection. The sensor was tested in saliva at 10 ng/mL and returned an 107.6% recovery. The dissociation constant Kd for HopQ/HopQ antibody interaction, estimated from Hill\u27s model, is calculated with a value of an order of 4.605 × 10−10 mg/mL. Conclusions: Due to the strategical choice of biomarker, the utilization of nanocomposite material to enhance the SPCE electrical performance, the intrinsic selectivity of the antibody-antigen interaction, and effective immobilization, the fabricated platform shows high selectivity, good stability, reproducibility, and cost-effectiveness for early H. pylori detection. Additionally, we provide insight into possible future aspects the researchers are recommended to focus on

Optical, Dielectric Properties and Energy Storage Efficiency of ZnO/Epoxy Nanocomposites

International audienceZnO/epoxy nanocomposites were prepared in five different contents (0.25–3.0 wt%). Optical, thermal and dielectric properties have been examined as a function of ZnO nanoparticles. The absorption optical spectra exhibit a broad intense peak assigned to the n–π* (HOMO–LUMO) transitions. Nanocomposite with 3.0 wt% ZnO sample completely blocks UV-light radiations in the region from 300 to 480 nm, which allowed that the prepared material to be used for UV-Shielding devices. The optical band gap is found to decrease with increasing filler ZnO concentrations. This might be due to increasing the density of defect states. Permittivity and electric modulus formalisms are used to analyze and interpret the experimental data. γ relaxation is observed in the low temperature region, which is attributed to the rearrangement of small parts of the polymeric chains. The α relaxation and the Maxwell–Wagner–Sillars (MWS) effect, attributed to the glass rubber transition of the polymeric matrix and the interfacial polarization phenomena respectively, are observed in the high temperature region. Using Havriliak–Negami approach, the temperature dependence of relaxation time for MWS and γ relaxations follows an Arrhenius behavior while the α relaxation time is well described by the Vogel–Fulcher–Tamann behavior. The activation energies of all relaxation modes were calculated and discussed. The energy density of the investigated samples is significantly enhanced. It is about 2 × 10−6 J/m3 for nanocomposite with 3.0 wt% ZnO at 20 °C.These results indicate that the effect of ZnO nanoparticles makes the proposed materials suitable candidates for energy storage applications