Hierarchical Route for the Fabrication of Cavitand-Modified Nanostructured ZnO Fibers for Volatile Organic Compound Detection

A hierarchical hybrid inorganic-organic system suited for the recognition of aromatic volatile organic compounds on brushlike ZnO fibers was synthetized. The hybrid material was obtained by a multistep approach based on the growth of ZnO nanorods onto electrospun ZnO fibers (average diameter 200 nm). The obtained nanostructured ZnO brushlike fibers (overall diameter 2 μm) were functionalized through the grafting of a bifunctional phosphonic linker (12-azidododecylphosphonic acid) followed by the anchoring of a specific cavitand receptor. The linker was anchored on ZnO fibers through the phosphonic group while the azide terminations reacted with a quinoxaline-bridged cavitand (QxCav) having four alkyne groups via "click" reaction. The anchoring steps were monitored through the evolution of the FT-IR features in the 3200-2800 cm-1 region due to C-Hx stretches and in the 2200-2000 cm-1 region due to the azide and alkyne groups of the phosphonic linker and QxCav. The recognition properties of this hybrid nanostructure toward α,α,α-trifluorotoluene vapors were evaluated by XPS and Raman measurements.