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

Abstract

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:
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)
OSTI Identifier:
1374232
Alternate Identifier(s):
OSTI ID: 1417751
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Published Article
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 9; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
electrochromic; flexible substrates; ligand-stripping; mesoporous thin films; nanocomposite; Tungsten oxide

Citation Formats

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., 2017. 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. Tue . "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 = {Tue Aug 08 00:00:00 EDT 2017},
month = {Tue Aug 08 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.nanolett.7b02730

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  • 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 preventingmore » 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 strategy of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.« less
  • Cited by 15
  • Graphical abstract: - Highlights: • ZnO nanorods synthesized on CVD-graphene and rGO surfaces, respectively. • ZnO/CVD-graphene and ZnO/rGO form a distinctive porous 3D structure. • rGO/ZnO nanostructures possibility in energy storage devices. - Abstract: In this work, reduced graphene oxide (rGO)/ZnO nanorods composites were synthesized on graphene coated PET flexible substrates. Both chemical vapor deposition (CVD) graphene and reduced graphene oxide (rGO) films were prepared following by hydrothermal growth of vertical aligned ZnO nanorods. Reduced graphene sheets were then spun coated on the ZnO materials to form a three dimensional (3D) porous nanostructure. The morphologies of the ZnO/CVD graphene andmore » ZnO/rGO were investigated by SEM, which shows that the ZnO nanorods grown on rGO are larger in diameters and have lower density compared with those grown on CVD graphene substrate. As a result of fact, the rough surface of nano-scale ZnO on rGO film allows rGO droplets to seep into the large voids of ZnO nanorods, then to form the rGO/ZnO hierarchical structure. By comparison of the different results, we conclude that rGO/ZnO 3D nanostructure is more desirable for the application of energy storage devices.« less