Electronic excitation induced tuning of surface plasmon resonance of Ag nanoparticles in fullerene C70 matrix

We report the electronic excitation induced controlled tuning of the surface plasmon resonance (SPR) wavelength of Ag nanoparticles (NPs) in fullerene C-70 matrix. The transformation of fullerene C-70 into amorphous carbon (a:C) under ion irradiation is used to tune the SPR wavelength of C-70-Ag nanocomposite thin films. A 100 nm blue shift was recorded for irradiation at a fluence of 3 x 1013 ions cm(-2) by 120 MeV Ag ions. A growth of Ag NPs from 7.0 +/- 0.8 to 11.0 +/- 0.4 nm with increasing fluence was observed by transmission electron microscopy and it is explained in the framework of thermal spike model. The transformation of fullerene C-70 into amorphous carbon with ion irradiation was confirmed by Raman spectroscopy. This work demonstrates the possibility to locally excite the SPR at a desired wavelength and therefore, acquiring multiple SPR bands at a single substrate which could be useful in developing more efficient optical sensors.