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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 m max 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 m max 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 m max 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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