Resonance frequencies of electrically charged nanoparticles

We develop a procedure to analyze charged nanoparticle (NP) surface modes. Using the resonance condition derived by Rosenkrantz and Arnon, we obtain frequencies at which the electromagnetic (EM) radiation stimulates resonance over a wide range of modes. Our results confirm that the relation between the resonance frequencies and the excess surface charge can be described by a monotonically increasing function. Taking the derivative of this function, it is evident that the lower surface potentials have a greater influence on the resonance frequency. This effect decreases as the surface potential increases. Surface modes contribute to the surface energy of charged NPs, and for this reason, they can modify charged NP optical properties. We found that there is a strong dependence of the resonance frequencies on the electrically charged NP refractive index and surface potential. This dependence can play an important role in nonmetallic nanotechnological devices, such as attenuators and modulators in optical communication and optical detectors in biomedical sensors.