Investigating functionalized active coated nanoparticles for use in nano-sensing applications

In this paper we investigate the use of active coated nano-particles (CNPs) for nano-sensing applications. Simulation results of the optical properties of an active CNP with a 24nm radius active silica core and 6nm thick plasmonic shell made of silver that has been functionalized by an additional spherical outer layer of varying thickness and refractive index are presented. In particular, the effects of the functional-layer thickness and refractive index on the super-resonant ( SR) state of the active CNP are presented. It is shown that the wavelength and optical gain required to excite the SR state may provide both a spectral and a power signature usable for nano-scale sensing and that these signatures may be used to identify the dimensions and optical properties of the functional layer. These results are then applied to the case of a functional layer containing a solution of human hemoglobin. It is demonstrated that the concentration of hemoglobin may be remotely determined from these SR signatures. (C) 2007 Optical Society of America.