Vanadium dioxide (VO2) has received considerable attention from a variety of fields due to its relatively low temperature and reversible metal-to-insulator transition (MIT). This transition, which occurs at approximately 68°C, is characterized by a small structural transformation from the low temperature monoclinic phase to the high temperature rutile phase. Along with this structural change, the electrical and optical properties of VO2 change dramatically, leading to interest in utilizing this material for solid-state memory devices and smart windows. The ability to lower the MIT is of critical importance for practical applications. Efforts in this area have focused on straining, doping, and electrical gating. Here, we demonstrate how nanocrystalline films of VO2 can be generated from colloidally synthesized and strained V2O3 bixbyite nanocrystals. The optical properties of these films could then be controlled electrochemically by application of various potentials. Using variable temperature spectroelectrochemical analysis under inert atmospheric conditions, we were able to identify four distinct optical states for the VO2 nanocrystalline film. Additional analysis using X-ray and Raman spectroscopy enabled us to relate the structural properties to the different optical states. The reversible electrochemical control of the optical properties in these VO2 nanocrystal films provides a new avenue for the practical application of VO2 at relevant temperatures. More broadly, the concept of using electrochemistry to influence the structural and optical properties of nanomaterials is of interest to the community studying the basic science of these systems.

Electrochemical control of vanadium dioxide nanocrystal films

251st National Meeting (2016)

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