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Title: Epitaxial Formation Mechanism of Multilayer TiO 2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly

Abstract

Surfactant-templated mesoporous titania (TiO 2) films have excellent physical and electronic properties, but some potential applications require films thicker than the 100-200 nm typically prepared by sol-gel coating. In this paper, the mechanism of forming micron-thick TiO 2 films with vertically oriented nanopore channels by a layer-by-layer deposition technique (up to eight 125 nm-thick layers) is investigated. In situ grazing incidence small angle x-ray scattering (GISAXS) performed on successive layers of Pluronic F127-templated films reveals if and how epitaxially oriented layers form during aging at 4 °C. At 78% relative humidity (RH), films cast onto substrates modified with crosslinked F127 maintain (011)-oriented $$Im\bar{3}m$$ cubic mesophase order, whereas micelles on unmodified glass lose their preferred orientation, leading to the observation of an arc in GISAXS attributed to an anisotropic micelle structure. A similar arc from randomly oriented domains is found at low RH (38%) regardless of substrate modification. Avrami model analysis shows that each oriented epitaxial layer followed formation kinetics with the same order (n=1.8±0.3) and half-life (10-20 min). Cross-sectional electron microscopy and impedance spectroscopy of the films after calcination at 400 °C show the formation of continuous, accessible vertical pore channels by micelle fusion for mesophases properly oriented by initial substrate modification.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [2];  [1];  [1];  [1]
  1. Univ. of Kentucky, Lexington, KY (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States). X-Ray Science Division
Publication Date:
Research Org.:
Univ. of Kentucky, Lexington, KY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division; National Science Foundation (NSF)
Contributing Org.:
Advanced Photon Source, Argonne National Laboratory
OSTI Identifier:
1580579
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Name: Journal of Physical Chemistry. C; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; nanoporous TiO2; multilayer film; epitaxial growth; in situ; GISAXS; surface modification; surfactant templating; battery; photocatalysis

Citation Formats

Khan, M. Arif, Islam, Syed Zahadul, Nagpure, Suraj, He, Yuxin, Wanninayake, Namal, Palmer, Rebecca L., Strzalka, Joseph, Kim, Doo-Young, Knutson, Barbara L., and Rankin, Stephen E. Epitaxial Formation Mechanism of Multilayer TiO2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly. United States: N. p., 2019. Web. doi:10.1021/acs.jpcc.9b09376.
Khan, M. Arif, Islam, Syed Zahadul, Nagpure, Suraj, He, Yuxin, Wanninayake, Namal, Palmer, Rebecca L., Strzalka, Joseph, Kim, Doo-Young, Knutson, Barbara L., & Rankin, Stephen E. Epitaxial Formation Mechanism of Multilayer TiO2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly. United States. doi:10.1021/acs.jpcc.9b09376.
Khan, M. Arif, Islam, Syed Zahadul, Nagpure, Suraj, He, Yuxin, Wanninayake, Namal, Palmer, Rebecca L., Strzalka, Joseph, Kim, Doo-Young, Knutson, Barbara L., and Rankin, Stephen E. Fri . "Epitaxial Formation Mechanism of Multilayer TiO2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly". United States. doi:10.1021/acs.jpcc.9b09376.
@article{osti_1580579,
title = {Epitaxial Formation Mechanism of Multilayer TiO2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly},
author = {Khan, M. Arif and Islam, Syed Zahadul and Nagpure, Suraj and He, Yuxin and Wanninayake, Namal and Palmer, Rebecca L. and Strzalka, Joseph and Kim, Doo-Young and Knutson, Barbara L. and Rankin, Stephen E.},
abstractNote = {Surfactant-templated mesoporous titania (TiO2) films have excellent physical and electronic properties, but some potential applications require films thicker than the 100-200 nm typically prepared by sol-gel coating. In this paper, the mechanism of forming micron-thick TiO2 films with vertically oriented nanopore channels by a layer-by-layer deposition technique (up to eight 125 nm-thick layers) is investigated. In situ grazing incidence small angle x-ray scattering (GISAXS) performed on successive layers of Pluronic F127-templated films reveals if and how epitaxially oriented layers form during aging at 4 °C. At 78% relative humidity (RH), films cast onto substrates modified with crosslinked F127 maintain (011)-oriented $Im\bar{3}m$ cubic mesophase order, whereas micelles on unmodified glass lose their preferred orientation, leading to the observation of an arc in GISAXS attributed to an anisotropic micelle structure. A similar arc from randomly oriented domains is found at low RH (38%) regardless of substrate modification. Avrami model analysis shows that each oriented epitaxial layer followed formation kinetics with the same order (n=1.8±0.3) and half-life (10-20 min). Cross-sectional electron microscopy and impedance spectroscopy of the films after calcination at 400 °C show the formation of continuous, accessible vertical pore channels by micelle fusion for mesophases properly oriented by initial substrate modification.},
doi = {10.1021/acs.jpcc.9b09376},
journal = {Journal of Physical Chemistry. C},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {12}
}

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This content will become publicly available on December 27, 2020
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