A concept and synthesis technology for a composite nanoparticle material which can be used to develop nanocomposite films and suspension with 1) dynamic refractive index control across a wide temperature and wavelength of light, and specified refractive index range, or 2) magnetic susceptibility or electronic conductivity over a wide temperature, magnetic field and electric field range. Core-shell nanoparticles can be made from two or more materials whose temperature dependent, electric field dependent or magnetic field dependent properties compensate one another will dynamically maintain a targeted refractive index, electronic conductivity or magnetic susceptibility over a specified temperature, electric and/or magnetic field range. Mixtures of composite nanoparticles with complementary behavior can optionally be used to widen the operational range of the nanocomposite material further or dampen temperature dependency in a controlled manner, e.g. using a non-random distribution of particles to affect a compensating gradient in the property of interest.