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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 (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. Here, 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 Im3m 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:
; ; ; ; ORCiD logo; ; ORCiD logo [1]; ORCiD logo; ; ORCiD logo
  1. X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Kentucky, Lexington, KY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; National Science Foundation (NSF)
Contributing Org.:
Advanced Photon Source, Argonne National Laboratory
OSTI Identifier:
1580579
Alternate Identifier(s):
OSTI ID: 1603349
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 124; Journal Issue: 3; 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 Z., 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 TiO 2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly. United States: N. p., 2019. Web. https://doi.org/10.1021/acs.jpcc.9b09376.
Khan, M. Arif, Islam, Syed Z., 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 TiO 2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly. United States. https://doi.org/10.1021/acs.jpcc.9b09376
Khan, M. Arif, Islam, Syed Z., Nagpure, Suraj, He, Yuxin, Wanninayake, Namal, Palmer, Rebecca L., Strzalka, Joseph, Kim, Doo Young, Knutson, Barbara L., and Rankin, Stephen E.. Thu . "Epitaxial Formation Mechanism of Multilayer TiO 2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly". United States. https://doi.org/10.1021/acs.jpcc.9b09376. https://www.osti.gov/servlets/purl/1580579.
@article{osti_1580579,
title = {Epitaxial Formation Mechanism of Multilayer TiO 2 Films with Ordered Accessible Vertical Nanopores by Evaporation-Driven Assembly},
author = {Khan, M. Arif and Islam, Syed Z. 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. Here, 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 Im3m 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 = 3,
volume = 124,
place = {United States},
year = {2019},
month = {12}
}

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