In this paper, we have used in-house the 3-D finite-difference time-domain method to analyze a novel design of metallic nanoparticles based on a sensing nanosystem. The proposed structure is composed of two gold-nanocylinders of finite height with varying radii separated by a nanogap. We have demonstrated that tunable plasmonic nanoparticles can be controlled by varying the size of the interparticles separation distance. By engineering the nanogaps, it is shown that a strong enhancement of the electric field is achieved. Our simulations show a pronounced wavelength shift for small nanogaps. In addition, the influence of the refractive index of the surrounding medium is presented.