Sensors for health and environment

Dosimeters for small-field radiation therapy

Principal investigators: C. Fauquet, D. Tonneau
PostDoc S. Debnath

We designed and fabricated smart X-Rays sensors for applications in radiation therapy (collaboration with Institute Paoli Calmettes, Marseille, France). The dosimeter is based on inorganic scintillators grafted at the extremity of an optical fibre (Fig.1). The visible light emitted by the scintillators is guided to a photon counter. The dosimeter is extremely stable and reliable and easy to calibrate. Because of the tiny interaction volume of this device with the irradiation field, this dosimeter affords a true improvement in comparison with those commercially available. Indeed, we could characterize with a very high accuracy small irradiation fields (below 5x5 mm²) needed for early stage cancer treatment. The dosimeter is particularly convenient for brachytherapy and we were able to demonstrate accurate dose measurement at a very small distances from the source (down to 200 µm), as well as high sensitivity at very large distances (up 5 cm from the source) (Fig. 2). The irradiation time during treatment was also measured with a high accuracy.

Nanostructured films of TCO for energetical and environmental applications.

Principal investigators: C. Fauquet, D. Tonneau

Collaboration: Laboratoire des Sciences de la Matière Condensée (LSMC), Oran 1 University, Algeria.

We collaborate with the LSMC lab, specialized in Transparent Conductive Oxide nanofilms elaboration and characterization, for fabrication of high efficiency photovoltaic cells  and highly sensitive gas sensors. The originality is in the elaboration methods, like hydrothermal growth or spray-pyrolysis, that can be handled at low temperatures and require little amount of reagents. These nanomaterials present numerous oxygen defects and active sites on their surface, due to their high surface/volume ratio. Recently, we demonstrated their high efficiency on the photodegradation of methylene blue, often released in the wastewater of textile industry (Fig. 4). Because this process only necessitates solar energy, it looks very promising.

Ingénierie des couches lipidiques et leurs propriétés physiques

Principal investigators: A. Charrier

PhD Student: USTH, doctoral grant
Collaborations: J.-M. raimundo, IMMF et M. Petit, NM, CINaM ; Y. Wakayama, NIMS, Japan, C. Henry-De-Villeneuve, LPMC,

Les couches lipidiques souvent utilisées comme système modèle des membranes cellulaires possèdent des propriétés intrinsèques (fluidité latérale, propriétés diélectrique) qui en font un matériau d’intérêt pour les applications. Les propriétés diélectriques naturelles de ces couches proviennent à la fois de leurs longues chaînes aliphatiques qui constituent une barrière au transport électronique mais aussi de leur haute densité moléculaire. Celle-ci est obtenue par l’auto-organisation spontanée des lipides mis en milieu aqueux sous forme de vésicules du fait de leurs propriétés amphiphiles. En couplant ingénierie moléculaire des lipides, et optimisation des procédés de dépôt sur substrat nous fabriquons des couches extrêmement denses, quasi-cristallines, stables mécaniquement, et aux propriétés d’isolant électrique tout à fait remarquables pour une couche de quelques nanomètres d’épaisseur. Nous nous intéressons aux interfaces constitués de cette couche avec des substrats organiques ou inorganiques et étudions les propriétés physiques de ces interfaces (organisation structurale, propriétés électriques et mécaniques.

OFET sensors for ion detection in complex media

Principle Investigator: A. Charrier

Organic field effect transistors (OFETs) are gaining interest for their potential applications in low-cost and flexible electronics. While most studies have focused on optimizing the mobility of organic semiconductor carriers (OSL), the choice of the gate dielectric (ODL) is also very important to minimize the density of electrical traps at the ODL/OSL interface. Most polymers already in use suffer from large leakage currents that are compensated for by increasing the thickness of the material, usually by several hundred nanometers or even microns. The disadvantage of this is the large operating voltage required to operate the transistor, with operating voltages ranging from a few volts to tens of volts. This can lead to heating of the device and possible damage to the organic materials and loss of performance. Moreover, in the more specific field of OFET sensors, a high operating voltage is a disadvantage for a high sensitivity and for reaching a low detection limit.
The originality of the project lies in the use of a lipid monolayer as a gate dielectric. With a thickness of a few nanometers and exceptional electrical insulating properties, this layer allows to use low working voltages while limiting leakage currents. The optimization of the ODL/OSL interfaces allows to reach extremely low detection limits in the attomolar range. We also develop original methods to reach high selectivity.The originality of the project lies in the use of a lipid monolayer as a gate dielectric. With a thickness of a few nanometers and exceptional electrical insulating properties, this layer allows the use of low working voltages while limiting leakage currents. The optimization of the ODL/OSL interfaces allows to reach extremely low detection limits in the attomolar range. We also develop original methods to reach high selectivity.