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A novel method has been implemented to prepare metal oxide nanopowders covered with known quantities of adsorbed water; we subsequently studied the γ-radiolysis of ZrO2 nanopowders covered with H2O layers. H2 yields from the adsorbed water radiolysis are of importance in multiple industrial contexts – the nuclear industry being a prime example. Measured H2 yields at water coverages of just below and above one monolayer are around 350 times greater than for neat water, but these yields decrease rapidly with increasing water loading of the ZrO2 nanoparticles, approaching the yield of bulk water at coverages of tens of water layers. The observed plateau of the yields at 0.5 to 2.0 monolayers coverage can be explained by the ease with which electronic excitations in the ZrO2 can be transferred across the interface to the first one or two adsorbed water layers. However, with increasing water loading, energy transfer to water layers further away from the interface becomes less efficient, and above ~30 water layers, most of the water is not affected by any exciton formation in the ZrO2.
The reactivity of graphene at its boundary region has been imaged using non-linear spectroscopy to address the controversy whether the terraces of graphene or its edges are more reactive. Graphene was functionalised with phenyl groups, and we subsequently scanned our vibrational sum-frequency generation setup from the functionalised graphene terraces across the edges. A greater phenyl signal is clearly observed at the edges, showing evidence of increased reactivity in the boundary region. We estimate an upper limit of 1 mm for the width of the CVD graphene boundary region.