Hybrid Nanocomposite Films Comprising Dispersed VO2

Oct 17, 2017 - ...
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Hybrid Nanocomposite Films Comprising Dispersed VO2 Nanocrystals: A Scalable Aqueous-Phase Route to Thermochromic Fenestration Nathan Fleer, Kate Pelcher, Jian Zou, Kelly Nieto, Lacey Douglas, Diane Sellers, and Sarbajit Banerjee ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b09779 • Publication Date (Web): 17 Oct 2017 Downloaded from http://pubs.acs.org on October 19, 2017

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ACS Applied Materials & Interfaces

Hybrid Nanocomposite Films Comprising Dispersed VO2 Nanocrystals: A Scalable Aqueous-Phase Route to Thermochromic Fenestration Nathan A. Fleer,a,b Kate E. Pelcher,a,b Jian Zou,a,b Kelly Nieto,a,b Lacey D. Douglas,a,b Diane G. Sellers,a,b* and Sarbajit Banerjee*a,b a

Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United

States b

Department of Materials Science and Engineering, Texas A&M University, College Station,

Texas, 77843-3003, United States Corresponding authors E-mail: [email protected]; [email protected] Keywords: fenestration, nanocrystals, optical coatings, smart glass, smart windows, sustainable nanotechnology, vanadium dioxide

Abstract: Buildings consume an inordinate amount of energy, accounting for 30—40% of worldwide energy consumption. A major portion of solar radiation is transmitted directly to building interiors through windows, skylights, and glazed doors where the resulting solar heat gain necessitates increased use of air conditioning. Current technologies aimed at addressing this problem suffer from major drawbacks, including a reduction in the transmission of visible light, thereby resulting in increased use of artificial lighting. Since currently used coatings are 1 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces

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temperature-invariant in terms of their solar heat gain modulation, they are unable to offset coldweather heating costs that would otherwise have resulted from solar heat gain. There is considerable interest in the development of plastic fenestration elements that can dynamically modulate solar heat gain based on the external climate and are retrofittable onto existing structures. The metal—insulator transition of VO2 is accompanied by a pronounced modulation of near-infrared transmittance as a function of temperature and can potentially be harnessed for this purpose. Here, we demonstrate that a nanocomposite thin film embedded with well dispersed sub-100 nm diameter VO2 nanocrystals exhibits a combination of high visible light transmittance, effective near-infrared suppression, and onset of NIR modulation at wavelengths 10 kg, the maximum limit tested under the specified method, further demonstrating the excellent adherence of the coatings to glass. Conclusions: In summary, fenestration units that are able to adapt to changes in ambient temperature have the potential to bring about considerable energy savings in both residential and industrial buildings by dynamically modulating solar heat gain in response to the external temperature without requiring human intervention. VO2 exhibits a reversible insulator to metal transition that is accompanied by a massive and dynamically switchable suppression of NIR transmittance and reflectance as a function of temperature. This phase transition can be utilized to limit NIR solar heat gain at high ambient temperatures, while allowing for use of solar heat gain to warm interiors at low ambient temperatures. In this work, we demonstrate that nanocomposite thin films embedded with well dispersed