Many recent research
studies have reported indirect methods for
the detection and quantification of OH radicals generated during photocatalysis.
The short lifespan and high reactivity of these radicals make indirect
detection using probes such as coumarin a more viable quantification
method. Hydroxyl radical production is commonly monitored using fluorescence
spectroscopy to determine the concentration of the compound 7-hydroxycoumarin,
which is formed from hydroxyl radical attack on coumarin. There are,
however, a number of additional hydroxylated coumarins generated during
this process, which are less amenable to detection by fluorescence
spectroscopy. Consequently, limitations and inaccuracies of this method
have previously been reported in the literature. As an alternative
approach to those previously reported, this work has developed an
electrochemical screening method using coumarin as a OH radical trap,
that is capable of in situ monitoring of not only 7-hydroxycoumarin,
but all the main mono-hydroxylated products formed. As a result, this
technique is a more representative and comprehensive method for the
quantification of OH radicals produced by photocatalysts using coumarin
as a probe molecule. Moreover, the electroanalytical method provides
a portable, rapid, sensitive, and accurate in situ method for the
monitoring of OH radical formation without the need for sample preparation.