Hybrid nanomaterials for controlled photothermal-switching – HEROES

HEROES is a 42 months research project dedicated to the synthesis of novel switchable heterostructures based on bistable units made of spin-crossover nanoparticles associated with gold nanoparticles to promote a fast and highly efficient photoswitching at room temperature. We propose to achieve picosecond - to nanosecond photoswitching times in order to develop more energy efficient switchable systems, taking advantage of synergetic pathways between the optical and the electronic properties.

Spin-Crossover (SCO) phenomenon is related to coordination complexes able to change their electronic configuration while perturbed by a physical parameter such as temperature, light, magnetic or electrical field, pressure. A number of properties are affected along this SCO since volume, color, magnetism, dielectric constant... are modified. The interest in the photo-switching properties of such molecular material is its speed, since femtosecond switching can be achieved. Moreover, molecules and nanoparticles are targeted to take part of electronic devices, especially those exhibiting memory effect at room temperature through the existence of a thermal hysteresis loop.

The aim of the HEROES project is to develop new hybrids nano-architectures to reach room-temperature fast and low energy photo-switching of the SCO properties and take advantage of this unique capability to implement it in electrical devices for photo-triggering of current. To achieve these goals the expertise of partner 1 in the elaboration of metallic and molecular nanoparticles is associated to the expertise of partner 2 in time-resolved optical characterizations and partner 3 on molecular electronics devices.

The HEROES project implies an important chemical step to produce hybrid nanoparticles based on SCO materials associated, through an original direct grafting to metallic nanoparticles able to promote local heating while irradiated. Indeed, the room temperature photo-switching of SCO materials is based on a photo-thermal effect: the pulsed light irradiation induces a short local heating allowing the compound to overcome its thermal hysteresis and change its state. The introduction of metallic nanoparticles as hyperthermia mediators, through their plasmonic properties, will allow a drastic reduction of the required irradiation power. Consequently a detailed optical characterization of the switching properties will provide key feedback information to the chemistry bottom-up build-up of these hybrid materials through the correlation between the switching intensity and the ratio of metallic/SCO nanoparticles, their morphologies and the global architectures.

Moreover, SCO properties should interplay with the conductive properties of an electronic device. These hybrid systems can then be implemented in electronic devices. The presence of the metallic nanoparticle is expected to enhance the conductivity of the bulk hybrid and its interfaces with metallic electrodes, and therefore improve this conductive switching. The elaboration of the hybrid architectures will open the possibilities to fast and easy photo-switch of an electrical device current.

All along the 42 months of the project, the chemistry, the optical and electrical properties of the nanohybrids will be addressed through the recruitment of one PhD and two postdoctoral researchers. The strong complementary expertise and the track record of the previous collaborations of the three partners will insure the success of the project.