In this paper we describe the fabrication of two-dimensionally periodic non-close-packed nanoshell arrays, consisting of a spherical polystyrene core coated with a thin gold shell, as well as their surface plasmonic properties. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle, atmospheric pressure plasma-induced isotropic etching, and deposition of gold thin film by thermal evaporation. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement without changing their original spherical shape and periodicity. Both experimental and theoretical studies revealed that the densely packed nanoshell array with a 160 nm inner core diameter and a 20 nm thick shell strongly scattered and absorbed near infrared light, due to the interaction between primitive plasmon modes associated with the surface of the nanoparticle. Furthermore, the resultant nanoshell array was utilized for near infrared light responsible localized surface plasmon resonance based sensor. The bulk refractive index sensitivity was 220 nm RIU(-1). Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.