At the same time water molecules may adsorb at the oxygen vacancy (Vo) site. These defect sites are
kinetically more favourable for hydroxyl groups (OH-
) adsorption than oxygen adsorption, hence
promotes increased water adsorption at the UV light irradiated areas.
Further, to understand the observed spectral effect on the wettability, the absorption spectrum of the
synthesized ZnO nanowires has been collected and plotted along with the UV LEDs emission spectra as
shown in figure 4. Better spectral overlap indicates that ZnO nanowires absorb more light at 365 nm than
385 nm. Therefore, the observed change on the surface wettability of ZnO nanowires is high when
irradiated with λp = 365 nm. This indicates that the wettability of the ZnO nanowires can be controlled by
tuning the wavelength of irradiating light.