Thermally induced tuning of SPR of metal-fullerene Ag(26%)-C70 nanocomposite

- Synthesis of bi-functional Ag-C70 nanocomposite thin film.
- Tuning of plasmonic resonance of Ag-C70 nanocomposite by thermal annealing.
- Growth of Ag nanoparticles in fullerene C70 matrix by thermal annealing.
- Fullerene C70 transforms into amorphous carbon at 300 °C.
- SPR tuning is due to mutual polarization and thermally induced structural transformation of matrix.

A bi-functional nanocomposite thin film containing Ag nanoparticles embedded in fullerene C70 is synthesized by thermal co-evaporation technique. Tuning of plasmonic resonance of Ag-C70 nanocomposite is obtained by annealing the nanocomposite thin film at different temperatures from 80 to 300 °C for 30 min. The optical and structural properties of nanocomposite thin film with respect to high temperature are studied by UV-visible absorption spectroscopy and X-ray diffraction. Transmission electron microscopy is performed to investigate the temperature dependent size evolution of Ag nanoparticles in fullerene C70 matrix. Growth of Ag nanoparticles is observed with increasing temperature above 200 °C due to enhanced diffusion of Ag in fullerene C70 and Ostwald ripening. The optical and structural properties of metal-fullerene nanocomposite is not significantly affected upto a temperature of 150 °C, after that a progressive blue shift of ~ 27 nm in SPR wavelength is observed with increasing temperature. The tuning of SPR is ascribed to the thermal induced structural transformation of fullerene C70 matrix into amorphous carbon and also to mutual polarization of the particles.