Influence of silver decoration on the nonlinear optical absorption exhibited by multiwall carbon nanotubes

A study about the optical and electrical response exhibited by multi-wall carbon nanotubes (MWCNTs) decorated by silver nanoparticles (Ag NPs) is presented. The size of the NPs varies in the range from 35 to 65 nm, with an average size of 47 nm. The samples were prepared by a chemical vapor deposition method. The third-order nonlinear optical response of the samples was evaluated by using single pulses of 1 ns at 532 nm wavelength. A vectorial two-wave mixing configuration was employed in order to measure the absorptive and refractive nonlinearities. An optical Kerr effect and a two-photon absorption process were identified as the main physical phenomena responsible for the third-order optical nonlinearities in the MWCNTs; however, a saturated optical absorption was developed by the sample when the tubes were decorated by Ag. Moreover, an important modification in the electrical capacitance exhibited by the studied sample after the inclusion of Ag NPs was observed. It is estimated that metallic NPs are capable to modulate nonlinear optical processes in decorated CNTs by selective near-resonant energy transfers.