Hydrophobic to hydrophilic conversion of TiO2 has been reported to occur based on measurements of the contact angle between water and a hydrophobic substrate surface as a function of UV irradiation time. The formation of -OH groups is considered to be responsible for the hydrophilicity; therefore, it is possible that the relative humidity in the atmosphere has an effect on the hydrophilicity response. In this study, TiO2 single crystals were first exposed to UV light at different relative humidity levels and then the UV light was switched off and the water contact angle was measured as a function of time. There was a linear relationship between the contact angle and time. Contact angles 30 s after the water drop first fell on the surface of the substrate after UV irradiation were smaller than those before UV irradiation. However, the contact angle was not dependent on the relative humidity. The slope of the contact angle vs. time curve before/after UV irradiation was dependent on the relative humidity.
Polymer gels containing dibenzo-24-crown-8 (DB24C8) ether moieties were synthesized by radical copolymerization of a DB24C8-containing monomer and acrylamide in the presence of a cross-linker. The IR spectra of the resulting polymer gels are indicative of the successful preparation of the DB24C8-containing acrylamide-based polymer gels. The polymer gels containing DB24C8 moieties can bind cesium ions and effectively remove cesium ions from an aqueous environment without nonspecific adsorption. The cesium removal was confirmed in the competition tests performed in the presence of sodium and potassium ions.