Near IR Exciton Theory of Ultrathin Crystalline Film Optics and Possibilities for Drug Delivery

Abstract

In this paper we have applied theory of exciton on the ultrathin molecular dielectric films—layered nanostructures with the thickness up to 20 atomic layers. We have calculated optical properties: the absorption, reflection and transparency indices as the function of frequencies of external electromagnetic field in near IR region. We showed that one of the significant properties of the ultrathin film is their interaction with substrate or environment, which could be represented through perturbation parameters. For symmetrically perturbed films, all optical properties depend on the position of the crystal plane with regard on boundary planes of the film. We have analyzed optical properties for the whole film structure based on the consideration for multiple reflection, absorption and transparency. The theory has been applied for the four-layered dielectric nanofilms with various different boundary conditions on film surfaces. As a result, we obtain some discrete resonant absorption lines, where their number, position and distribution strongly depend on the boundary parameter values, i.e. on the type and the technological process of their preparation/fabrication. While balk made from the same material totally absorb the near IR region, in ultrathin films will appear only selective and discrete absorption (also with reflection and transparency too). These results could be used in optical engineering of nanostructures and technology of designing of new electronic, photonic and photovoltaic devices. In addition, particularly designed nanoparticles are used in nanomedicine, whose behavior strongly depends on external electromagnetic field, in purpose of drug carry or delivery.