Nanoparticles are known to offer a variety of benefits for thermal transport, and of particular relevance here are the vast changes to the radiative properties due to the large extinction cross section at the corresponding surface plasmon resonance wavelength [1, 2]. Recent papers have indicated that dielectric core metallic shell nanoparticles yielded a plasmon resonance tunable from ultraviolet to infrared by changing the ratio of core radius to the total radius [3-6]. We are interested in developing a dispersion of core-shell multifunctional nanoparticles capable of dynamically changing their volume ratio and thus their spectral radiative properties. This work addresses the plasmon resonance tuning ranges for different metallic shell nanoparticles, and explores the solar-weighted efficiencies of corresponding core-shell nanoparticle dispersions. Through our electrostatic model, we achieve a shift in the plasmon resonance peak from a wavelength of about 500 nm to around 1500 nm for Au-coated silica core nanoparticles. Using core-shell nanoparticles dispersions, we show that it is possible to create efficient spectral solar absorption fluids. We also demonstrate that it is possible to design materials for applications which require variable spectral absorption or scattering.