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Title: Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods

Low-temperature processed mesoporous nanocrystal thin films are platforms for fabricating functional composite thin films on flexible substrates. Using a random arrangement of anisotropic nanocrystals can be a facile solution to generate pores without templates. However, the tendency for anisotropic particles to spontaneously assemble into a compact structure must be overcome. Here in this paper, we present a method to achieve random networking of nanorods during solution phase deposition by switching their ligand-stabilized colloidal nature into a charge-stabilized nature by a ligand-stripping chemistry. Ligand-stripped tungsten suboxide (WO 2.72) nanorods result in uniform mesoporous thin films owing to repulsive electrostatic forces preventing nanorods from densely packing. Porosity and pore size distribution of thin films are controlled by changing the aspect ratio of the nanorods. This template-free mesoporous structure, achieved without annealing, provides a framework for introducing guest components, therefore enabling our fabrication of inorganic nanocomposite electrochromic films on flexible substrates. Following infilling of niobium polyoxometalate clusters into pores and successive chemical condensation, a WO x–NbO x composite film is produced that selectively controls visible and near-infrared light transmittance without any annealing required. The composite shows rapid switching kinetics and can be stably cycled between optical states over 2000 times. This simple strategymore » of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.« less
Authors:
 [1] ;  [1] ;  [2] ; ORCiD logo [1]
  1. Univ. of Texas, Austin, TX (United States). McKetta Dept. of Chemical Engineering
  2. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 9; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
electrochromic; flexible substrates; ligand-stripping; mesoporous thin films; nanocomposite; Tungsten oxide
OSTI Identifier:
1374232
Alternate Identifier(s):
OSTI ID: 1417751

Heo, Sungyeon, Kim, Jongwook, Ong, Gary K., and Milliron, Delia J.. Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods. United States: N. p., Web. doi:10.1021/acs.nanolett.7b02730.
Heo, Sungyeon, Kim, Jongwook, Ong, Gary K., & Milliron, Delia J.. Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods. United States. doi:10.1021/acs.nanolett.7b02730.
Heo, Sungyeon, Kim, Jongwook, Ong, Gary K., and Milliron, Delia J.. 2017. "Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods". United States. doi:10.1021/acs.nanolett.7b02730.
@article{osti_1374232,
title = {Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods},
author = {Heo, Sungyeon and Kim, Jongwook and Ong, Gary K. and Milliron, Delia J.},
abstractNote = {Low-temperature processed mesoporous nanocrystal thin films are platforms for fabricating functional composite thin films on flexible substrates. Using a random arrangement of anisotropic nanocrystals can be a facile solution to generate pores without templates. However, the tendency for anisotropic particles to spontaneously assemble into a compact structure must be overcome. Here in this paper, we present a method to achieve random networking of nanorods during solution phase deposition by switching their ligand-stabilized colloidal nature into a charge-stabilized nature by a ligand-stripping chemistry. Ligand-stripped tungsten suboxide (WO2.72) nanorods result in uniform mesoporous thin films owing to repulsive electrostatic forces preventing nanorods from densely packing. Porosity and pore size distribution of thin films are controlled by changing the aspect ratio of the nanorods. This template-free mesoporous structure, achieved without annealing, provides a framework for introducing guest components, therefore enabling our fabrication of inorganic nanocomposite electrochromic films on flexible substrates. Following infilling of niobium polyoxometalate clusters into pores and successive chemical condensation, a WOx–NbOx composite film is produced that selectively controls visible and near-infrared light transmittance without any annealing required. The composite shows rapid switching kinetics and can be stably cycled between optical states over 2000 times. This simple strategy of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.},
doi = {10.1021/acs.nanolett.7b02730},
journal = {Nano Letters},
number = 9,
volume = 17,
place = {United States},
year = {2017},
month = {8}
}