The local-field effects in optical response of nanocomposite thin films. An implementation in sensorics of biospecific interactions

The method of calculation of optical response of nanocomposite film with inhomogeneous distribution of inclusions along the film thickness is proposed in the framework of the effective susceptibility concept. The electrodynamic interactions inside the nanocomposite system are taken into account. The optical responses of nanocomposite thin films with embedded Au spherical nanoparticles are calculated. The calculated dissipative functions show that interaction between elementary excitations inside the inclusions and an electromagnetic field results in arising hybrid excitations which causes the peaks in absorption spectra. The dependencies of the absorption spectra on different volume filling fraction of inclusion particles and different spatial distributions of inclusion nanoparticles are presented for some thicknesses of film. The developed method was used to study the dependence of absorption profiles on the characteristics of the shell of nanoinclusions. The dependencies allow to propose an implementation of the method for studies of biospecific interactions at the surface of modified nanoinclusions.