Functionalization of nanostructured ZnO films by copper-free click reaction.

The copper-free click reaction was explored as a surface functionalization methodology for ZnO nanorod films grown by metal organic chemical vapor deposition (MOCVD). 11-Azidodecanoic acid was bound to ZnO nanorod films through the carboxylic acid moiety, leaving the azide group available for Cu-free click reaction with alkynes. The azide-functionalized layer was reacted with 1-ethynylpyrene, a fluorescent probe, and with alkynated biotin, a small biomolecule. The immobilization of pyrene on the surface was probed by fluorescence spectroscopy, and the immobilization of biotin was confirmed by binding with streptavidin-fluorescein isothiocyanate (streptavidin-FITC). The functionalized ZnO films were characterized by Fourier transform infrared attenuated total reflectance (FTIR-ATR), steady-state fluorescence emission, fluorescence microscopy, and field emission scanning electron microscopy (FESEM).