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Photo-induced changes in the Langmuir adsorption constants of metal oxide layers in self-cleaning cation sensors.

Published online by Cambridge University Press:  07 February 2012

Philip S. Foran
Affiliation:
Engineering Department, Lancaster University, Lancaster, LA1 4YW, UK.
Colin Boxall
Affiliation:
Engineering Department, Lancaster University, Lancaster, LA1 4YW, UK.
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Abstract

For the first time, we have used a metal oxide-coated quartz crystal microbalance (QCM) to measure Cs+ adsorption onto illuminated and un-illuminated mesoporous TiO2 (m-TiO2) films by microgravimetric means in-situ. In the simplest case, such experiments yield two parameters of interest: K, the Langmuir adsorption coefficient and mmax the maximum mass of adsorbate to form a complete monolayer at the m-TiO2-coated quartz crystal piezoelectric surface. Importantly, we have found that illumination of the m-TiO2 film with ultra bandgap light results in an increase in mmax i.e. illumination allows for greater adsorption of substrate to occur than in the dark. Our studies also show that under illumination, K also increases indicating a higher affinity for surface adsorption. The photoinduced change in mmax and K are thought to be due to an increase in surface bound titanol groups, thus increasing the number of available adsorption sites – and so providing evidence to support the notion of photoinduced adsorption processes in photocatalytic systems. These findings have implications for the development of a reversible adsorption based microgravimetric sensor for Cs+.

Type
Research Article
Copyright
Copyright © Materials Research Society 2012

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