The project aims to dynamically control the spectral radiative properties of nanoparticles dispersed in a fluid. Nanoparticles are known to offer a variety of benefits for thermal transport, and of particular relevance here the vast changes to the radiative properties that can be achieved through the dispersion of nanoparticles. With the advent of nanoparticles it is possible to control the radiative properties of dispersions as opposed to just passively observing such properties. In particular, a dispersion of core-shell multifunctional nanoparticles will be created that are capable of dynamically changing their volume and thus their spectral radiative properties. Preliminary experiments have shown that these multifunctional nanoparticles are capable of being synthesized to achieve temperature sensitive volumetric changes. To date most of these particles have been synthesized with polymer shells and inorganic cores while this proposal plans to reverse this with polymer cores and inorganic and metallic shells to achieve large radiative property shifts in the visible-infrared wavelengths. This proposal addresses this question through a comprehensive set of experiments and analyses. The experiments will largely focus on measuring the spectral radiative properties of different dispersions at different temperatures and thus different volumes using spectrophotometric techniques. These measurements will then be correlated with modeling results to improve fundamental understanding of the dynamic control of radiative transport as a function of the core material, shell material, size and volumetric shift achievable.
. The potentially transformative nature of the proposed project is the exciting capability to dynamically (and reversibly) change the radiative properties of a dispersion of nanoparticles. Fundamental questions will be addressed such as: can a single dispersion of core-shell multifunctional nanoparticles be controlled so that it can serve as either an absorber, or as an emitter of energy? Can this control be achieved in a passive manner? Can this be done using cost effective, environmentally benign materials? By coupling radiative property control with the dynamic capabilities offered by multifunctional nanoparticles innovative passive control methods will be investigated addressing further questions such as: Can volumetric changes be effected with changes in temperature? How many times can the dispersion go through the reversible volume change process? What are the fundamental structure-property relationships in these core-shell materials that give rise to changes in absorbance and how can this relationship be tuned?
The broader impacts of this project come from the technological opportunities that may be enabled by developing dynamically controllable radiative properties within the proposed nanoparticle dispersions. One potential system that may result from such a system is a dual-use solar thermal collector and night-sky radiator. The use of nanoparticles acting as direct absorption receivers has been shown to offer improved efficiencies over conventional surface-based receivers. Another intriguing option is the ability to create a thermo-optical switch. Such a switch would allow for creating a liquid filter that at times is transparent while at other times could be opaque. Another impact lies in the direction of undergraduate research and the recruitment of under-represented minority.
