Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates

A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with <i>p</i>-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (<i>p</i>-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250–350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and ¹H NMR spectroscopy. The resulting hydrophobicity correlates with H₂ temperature-programmed reduction (H₂-TPR) stability, which therefore provides a practical gauge of hydrophobicity