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The superhydrophilization of a silicon (Si) surface by atmospheric-pressure plasma jet irradiation was analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The Si surface was irradiated with an atmosphericpressure argon (Ar) plasma jet in air for 5 s. The contact angle of a water drop on the Si surface decreased from 77 to 7 • as a result of plasma jet irradiation, meaning that the Si surface became superhydrophilic. TOF-SIMS analysis indicated that the superhydrophilization was due to the removal of hydrophobic polydimethyl siloxane (PDMS) adsorbed on the Si surface and the increase in the amount of the hydrophilic silanol (SiOH) group. Emission spectral analysis of the plasma jet indicated that the SiOH group was formed when hydroxyl (OH) radicals, generated by collisions between high-energy electrons in the plasma and water molecules in air, bond to Si atoms on the surface.

Porous Ni catalyst modified with a small amount of Zr was found to be highly active for hydrogenation of nitrate (200 ppm) in water at 333 K. This is the first example of noble metal-free catalyst effective for this reaction.