Wettability conversion on the liquid flame spray generated superhydrophobic TiO₂ nanoparticle coating on paper and board by photocatalytic decomposition of spontaneously accumulated carbonaceous overlayer

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Hannu Teisala, Mikko Tuominen, Milena Stepien, Janne Haapanen, Jyrki M. Mäkelä, Jarkko J. Saarinen, Martti Toivakka, Jurkka Kuusipalo
Publisher: SPRINGER
Publication year: 2013
Journal: Cellulose
Journal acronym: CELLULOSE
Volume number: 20
Issue number: 1
Start page: 391
End page: 408
Number of pages: 18
ISSN: 0969-0239
eISSN: 1572-882X


Abstract

Titanium dioxide (TiO2) is a photoactive material with various interesting and useful properties. One of those is the perfect wettability of TiO2 surface after ultraviolet (UV) illumination. Wettability of a solid surface plays an important role in the field of printing, coating, and adhesion among others. Here we report on a superhydrophobic and photoactive liquid flame spray (LFS) generated TiO2 nanoparticle coating that can be applied on web-like materials such as paper and board in one-step roll-to-roll process. The LFS TiO2 nanoparticle coated paper and board were superhydrophobic instantly after the coating procedure because of spontaneously accumulated carbonaceous overlayer on TiO2, and thus there was no need for any type of separate hydrophobization treatment. The highly photoactive LFS TiO2 nanoparticle coating could be converted steplessly from superhydrophobic to superhydrophilic by UV-illumination, and the coating gave strong response to natural daylight illumination even in the shade. The superhydrophobic LFS TiO2 coated surface can be used as an intelligent substrate, where photo-generated hydrophilic patterns guide the fluid setting and figure formation. Our study reveals that the wettability changes on the LFS TiO2 surface were primarily caused by the photocatalytic removal of the carbonaceous material from TiO2 during the UV-illumination and spontaneous accumulation of the carbonaceous material on the surface of the metal oxide during storage in the dark. The latter mechanism was found to be a temperature activated process which could be significantly speeded up by heat treatment. If other mechanisms such as surface oxidization, increment of hydroxyl groups, or charge separation played a role in the wetting phenomena on TiO2, their effect was rather secondary as the removal and accumulation of the carbonaceous material dominated the wettability changes on the surface. Our study gives valuable information on the complex issue of photo-induced wettability changes on TiO2.


Keywords

Cellulose, Interface wetting, Patterning, Photocatalysis, Roll-to-roll, Titanium

Last updated on 2019-16-10 at 02:38