Electrical and optical properties of silver core-lithium niobate shell nanostrucures within a glass medium

Abstract

Silver nanoparticles of diameters in the range of 4.2-46 nm have been used to grow nanoshells of lithium niobate with thicknesses in the range of 2.2-22 nm in a silicate glass matrix. The lithium niobate shells form a percolative network and show electronic conduction. This has been explained as due to Mott's variable range hopping conduction mechanism. The hopping is interparticle because the density of localized states is found to be in reasonable agreement with the density of nanoparticles with a core-shell structure. The ac conductivity is shown to be dependent on frequency with the exponent having a value around 0.5. This arises due to the charge motion's being operative in a two-dimensional structure with one of these dimensions involved in such motion. Optical absorption of the core-shell structured nanoparticles exhibits two peaks- one around 350 nm is ascribed to plasmon resonance of silver nanoparticles which are not covered by a niobate shell, and the other in the range of 550-650 nm is caused by light scattering from the core-shell structure.