Silica-shell encapsulation and adhesion of VO2 nanowires to glass substrates: integrating solution-derived VO2 nanowires within thermally responsive coatings
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2014 IOP Publishing Ltd. The binary vanadium oxide VO 2 undergoes a reversible insulator-metal phase transition in response to increasing temperature accompanied by an orders of magnitude alteration of optical transmittance; the low-temperature monoclinic phase of VO 2 is infrared-transmissive, whereas the high-temperature rutile phase is infrared-reflective. This remarkable property portends applications in thermally responsive spectral mirrors that can modulate infrared transmittance as a function of temperature. Using a modified Stber process, we demonstrate the constitution of conformal SiO 2 shells around the VO 2 nanowires. The SiO 2 shells enhance the robustness of the VO 2 nanowires towards thermal oxidation; the thickness of the shells is observed to depend on the reaction time. Notably, the deposition of conformal shells does not deleteriously impact the metal- insulator transitions of the VO 2 nanowire cores. A modification of this approach allows for the VO 2 nanowires to be embedded within a SiO 2 matrix bonded to glass. The applied coatings are strongly adhered to glass as evaluated using standardized ASTM methods. The coatings exhibit promising thermochromic response and attenuate transmission of near-infrared radiation with increasing temperature.
